Keep in mind that both power turbines and electrical generators have an efficiency factor, so measuring the electrical power is less than what the gas turbine is actually making.
I’m glad you explained the different fuels and how they compensate between them. I had wondered what they did and if the power changed with different fuels. Makes sense that they’d be able to end up being able to just adjust the fuel flow to get to the desired temps. I’m so used to piston engines it’s sometimes difficult to wrap my head around the turbine engines.
Back in the 1960s, when I began my career lifetime in the design of gas turbine engines, industrial, marine and aero, the Industrial Olympus was just entering service at a rating of 17.5MW. It was derived from the Olympus 200 series engine in the Avro Vulcan bomber, which had a take-off rating of 17,000lb thrust. However, the 17.5MW rating was effectively a derating from the aero T/O rating: the industrial gas generator would not have lasted very long at the aero engine's T/O rating - nor would the aero engine. The same basic gas generator, with an improved combustion system based on that of the engine for the Concorde prototypes, plus a cooled HP turbine, designed in the early 1970s, was rated at 30MW. This is the Industrial Olympus that AgentJayZ has shown us in the past.
got the math at the end a bit tounge tangled i think; one megawatt is 1000 killo watts, or 1 million watts (1000 killowats), making it 1 kilowatt of power roughly equals one pound of thrust, or 1.3 ish horsepower per pound
You nail this. It is all about the frame of reference as soon as people try and do apples and apples comparisons but then fail to treat it as an energy in versus energy out black box model. And the comparisons between a turbojet and a piston engine measuring horsepower at the fly wheel? C’mon!! Madness.
Right?! The inconsistency is really annoying. If we want to calculate actual propulsive power delivered to the aircraft, then stick to velocity * thrust for both jets and propellers.
AJZ Happy Holidays thanks for an informative and entertaining video. Having worked on J79 (LM1500) in a USN Patrol Gunboat BITD which was rated at 12,900 SHP and drove the 240T 165' boat to 45-50knts. Also after Navy I worked at Lockheed ADP who built the F104 which also had a single J79 W AB and did Mach2.2+. I also worked at a So Cal Utiltiy for 31 yrs where We had 8 PW GG4s (J75s) exhausting on expander turbines that created 180MW of emergency peaker electrical power in about 2min from turning gear to 3550 srpm where field brkrs closed and at 3600 srpm w system synchronized. Stay Healthy.
As it’s Christmas, can I recite my party piece, please? If you have an aircraft in horizontal flight at constant speed and you know (or can calculate) the thrust of the engines at that flight condition - or you know (or can calculate) the drag force on the aircraft, then you can work out the actual horsepower that the engines are effectively delivering. You know the velocity of the aircraft (in ft/sec). You know the force that the engines are working against (in lb force) - and thrust equals drag, of course. You can multiply one by the other and divide by James Watt’s magic number of 550 - and, hey presto, that is the horsepower figure for the engines at that condition. Do that for Concorde in supersonic cruise at 1,350 miles /hr, at an altitude of 58,000ft, where the four Olympus 593 engines were producing 9,000lb thrust each. The answer? Near enough 130,000 horsepower. And a Merry Christmas everyone!
The only thing you said that I understood was "go to the cat videos" but after 25 minutes I was still watching this. Jokes aside, this was a great explanation to a question that on the surface seems very simple, but in reality is like trying to compare oranges to lemons.
I was driving with a mate back when I was young, and a semi was 2 metres from the back of our car when a front tyre blew out. Oh man I thought I'd not get a chance to grow old. No turn offs available so I helped the driver steady the steering at 75MPH. Then we ended up on a hill and the wheel nuts were rattle gunned on. Had to find a large boulder to mount the L shape tool onto, while getting the driver to drive forward gingerly. Took a while.
That's a good idea, I have a M35a2, Duce and a half. The front tire is bald and I want to put on the spare, I've stood on the breaker bar and it didn't care at all, about 300ft/lbs. I'll put a block of wood under the wrench or something. Thanks.
JZ, I’ve been thinking when an engine is fixed to the ground and running it is moving and doing work. Not only is it moving the air as you explain, it’s also changing the rotation of the planet. It’s just hard to measure 🤣
Oooooooh! Greg's airplane and Angent Jayz, thurst vs Hp! This is the most interesting internet discussion ever.. Always a pleasure to listen to both of you guys! Merry Christmas and Happy New year!
Bit late to the party, but really great to see your take on it, talking about the actual usable power that the engine can make. This contrasts nicely with Greg's video on the Tomcat's horsepower, at a very different take, looking at propulsive power usable for overcoming aircraft drag and accelerating it (which is effected by its thrust directly). As you said in the beginning, no equation, and tons of equations, depending on your point of view. Thanks.
I've always used a very rough rule-of-thumb as 2.5 lbs of thrust makes 1 hp. I used to fly a Citation C-550 which had 5,000 lbs thrust in total and it felt like it had about 2,000 hp. When I was flying 747's I once stuck a car accelerometer on it for one take-off and it came up with 72,000 hp, which was about 2.5:1 with the thrust.
A rough conversion is the LM2500, which is also the core of a CF-6, which was sometimes used to power the earlier models of the 747. Early LM2500 engines, which had an integral power turbine and a mechanical shaft output, were rated at about 45 thousand Hp. 66 thousand ft-lbs of torque at 3600 rpm. So 4 of those is a lot of ponies.
@@AgentJayZ Yeah I've flown 747's with CF6-50's and -80's. Best engine of the three options I reckon. Set power with N1 rpm, not EPR, a more reliable way to make sure you're getting the right power.
For a turbofan....how much shaft horsepower would it take to turn the fan at takeoff rated thrust? It's a lot. When talking to people I always give it 1:1 ratio. 60,000lbs of thrust takes roughly 60,000 horsepower to turn the fan at that RPM. Rough estimate, but it's ballpark.
JayZ. Good to see you back. Hoping all is well up north and that your holidays and upcoming year are the best ever. Thanks for the interesting, no, fascinating content. Keep up the good work.
Four Lm2500 engines power the Spruance DD-963 class destroyers. Thanks to point out that this engine is an power turbine version of the Cf-6 aeroengine.
G'day Jay, Yay Team ! I was wondering where you'd got to, good to see you back in my feed. I'm olde Skool mate, my idea of a HorseyPower is the 50-pound Wooden Bucket with 10 Imperial Gallons of Water weighing 550 Pounds gross between them, with a 1-inch diameter Rope (officially weightless according to the allegation !) leading straight up the Mineshaft and over a 1-ft diameter Pulley, harnessed to a Horse...; the Horse walks away at 1 Foot per Second (0.68 mph), and thus the 550 Pounds is lifted vertically at 1 Foot per Second. Last time I actually used the equation was "test flying" my eBike on the neighbour's Driveway, with me and the Bike with 2 spare Batteries (220 pounds) travelling 1 Km in 3 minutes and climbing 40 metres (126 ft) at an indicated average groundspeed of 19 Km/Hr. I make it out that the Vertical Lifting equates to the Hub-Motor delivering 0.16 Horsepower to lift the weight up that height in that time...; and I pluck from my Arse the guess that the work overcoming Aerodynamic Drag plus the work overcoming Rolling Resistance (bouncing over the rocky Dirt Driveway) is about equal to the work of lifting the Weight in the time. All done without my input to the Pedals, so the "250 Watt Motor" does 0.32 Horsepower worth of work, and with a Horsepower being "half a Columbus (1492/2= 746 Watts !), then a third of 746 equals 248.6 Watts of Twistiness and 1.4 Watts wasted as Heat...(the Motor warms up from 28 degrees C. to 31 during the 3 minutes !) So, them there Chinamen sure seem to know what they're doing, when it comes to making Electric Bicycles, and the Maths more or less works out. Comparing Horses to Watts to Twistiness in a Shaft to Air Displacement and Wind to Thrust is always goanna be an approximation founded in Guesswork, but it feels good when the numbers indicate that our Guesses are "somewhere close to reality" ; I guess (!). Anyway mate, to collect your reward (having a few giggles about Biggles !), please feel free to backtrack me to my Videos, therein to find, "The Aviator's Moustache..., Mystery Solved !" Its only 56 seconds duration, but it relies on a New Scientist magazine Photo Feature, so it might be not-wrong (?) ! Happy Solstice Festival ! Such is life, Have a good one... Stay safe. ;-p Ciao !
As you will see from my party piece comment, what James Watt applied to Dobbin can be applied to something a little more advanced, such as Concorde, although that's passing into history now too - but at least I got to fly on her. Merry Christmas!
@@grahamj9101 G'day, Yay Team ! You flew on the Concorde ? Yikes ! Well done mate, welcome to the Club for Aeroplanologists who've flown things which are now safely stashed in Museums ! I was literally away off at the opposite end of the spectrum from the Concorde. To see what took me for my first solo, title-search YT for, "The 8-Hp, 1975, Red Baron Skycraft Scout ; World's 1st Legal Minimum Aircraft !" I was it's 3rd owner, it was my first Aeroplane, when I was 17, and I didn't do anything actually "pioneering" in it ; but in 1978 I was the last person to ever sit in it while wondering how to get it back down on the ground, without making a mess of everything ! Such is life, Happy (Summer, here) Solstice Festival ! Have a good one... Stay safe. ;-p Ciao !
@@WarblesOnALot Yes, I flew on Concorde as a guest of BA, because I was a member of the team at R-R Bristol that kept her Olympus 593 engines turning and burning. Periodically, they organised an engineering meeting at JFK and made a day trip of it. However, when it was my turn, there were too many paying passengers and we had to stay overnight in New York.
It is funny why it is so important to concert thrust to horse power or kW. My light bulbs makes Candela / Lumen, why don't we convert this to Watts too. Thanks for all your great videos, I have learned a lot from them
My simplistic understanding is this ..... Automobile engines are not typically described in terms of thrust or units of force because they do not produce a direct force to propel the vehicle forward in the same way that a jet engine does. In an automobile engine, the power output is used to turn the wheels of the vehicle through a transmission and other mechanical components. The force that is produced by the engine is transmitted through the drive-train to the wheels, which then apply the force to the ground to move the vehicle forward. Therefore, while force is involved in the operation of an automobile engine, it is not the primary output of the engine, and it is not a direct measure of the engine's ability to propel the vehicle forward. In contrast, thrust is the primary output of a jet engine and is a direct measure of the engine's ability to propel an aircraft forward through the air. Therefore, thrust is a more useful measure for jet engines, while horsepower is a more useful measure for automobile engines, because it provides a direct measure of the engine's ability to turn the wheels and move the vehicle forward.
Yes, all good. With the LM1500 and J79, we have the opportunity to compare the thrust and Hp of two engines built on the exact same gas generator. The part numbers of the rotating bits inside are the same, and so are major shafts and cases. Same story with the LM2500 /CF6.
Stereo amplifiers are rated in watts. By how much power they deliver to the speakers, which rattle air to make sound. At jet exhaust, the power of the air being accelerated also is 'wasted' to make sound. That can be measured in decibels. As loud as jets are, the sound wattage is only a tiny fraction of the acceleration wattage. Accelerated air + vibrating air = power out. Little side note.
I built a sub using a JBL 18" that has a maximum continuous sine wave power rating of 30W... recommended for use with amplifiers rated at up to 1200W RMS. Different standards!
Horsepower is defined as the amount of work over time. That to me seems very vague. How do you measure work? What is work? In a car it's could be how much it is pushing to car to overcome weight and friction. How can that be measured in a jet? Or driving a generator? You are right, it can be confusing. Going to watch cat videos now...
Yep the problem is that if the frame of reference is not based on energy in and energy out - then the analysis is totally arbiter and open to apples and oranges comparisons.
Why do I watch, because I use to repair gas turbines and screw turbines, I balanced them plus ultrasound the turbine blades. But now retired and want to see if anything has changed in the industry. But it's all the same.
consider the efficiency of the pt, a jet generator can put out 10x energy per sec but the pt output may have 5x at the 50% efficient pt+electric generator combo
I did some rough thrust calculation based on a piston engine at x HP at x rpm with x axle ratio and x tire diameter. This gets thrust at the tires and also a headache
A faster but also very rough method (it ignores friction forces that are being overcome such as drivetrain loss, aerodynamic forces and rolling resistance) is to take the 0-60 time (X in following equation) and convert that to an acceleration (Acceleration (m/s^2) = 60 miles/hour / X seconds *[1609 meter/ 1 mile]*[1 hour / 3600 seconds] ), Force (N) = Thrust = Mass (kg) * Acceleration (m/s^2). A car with an 8 second 0-60 time that weighs 1500 kg is accelerating at 3.35 m/s^2 averaging 5028 N (1130 lbf) thrust. All the terms in square brackets are equal to 1 so they don't affect the value of the result, but allow various units to cancel out to get everything to SI units as this unit system was designed to do these types of calculations.
Well, as Jay said, it comes down to mass-flow. Measuring that on the exhaust of these things is difficult. And, the measurement method will to some extent affect the performance of the engine. For aircraft, knowing the thrust is enough, because the drag of the aircraft can be calculated. For a power turbine, to get some idea of shaft horsepower output, you need to have some idea of mass-flow out of the gas generator...
If you really want to break someone's brain, we can show that 180 horsepower equals both 600 lbs of thrust and 1,370 lbs of thrust. My 1964 M20C, powered by a 180 HP Lycoming O-360, has a 500 ft takeoff roll at 2200 lbs gross weight, at sea level on a cold day. This maths out to about 600 lbf thrust. The Robinson R-22 helicopter idea a nearly identical 180 HP Lycoming HO-360, H being the "helicopter" designation. The R-22 has a Max grid weight of 1,370 lbs, and it can hover at that weight. So, 180 hp produces either 600 or 1,400 lbf thrust, depending on what spinny things you connect it to.
I’m fine with the “A metric mega-shit-ton” as an answer for turbo jet thrust to horsepower conversion. Just change the HP to KW to keep things simple, even for us Americans.
Hey, I’m having a question that wasn’t talked about just yet, if I’m not mistaking. It’s especially regarding older Turboshaft engines, with a one shaft design (take the Alouette II with it’s Artouste engine as an example). Being a one shaft turboshaft must mean they’re unable to start under load just as a piston engine would because spinning the compressor in first place would mean the starter would have to spin the whole Rotor and gearbox assembly, right? So do they have manually engageable clutches like cars? Or does the term „One shaft“ just ignore the shaft and the stage of the working turbine? I‘m currently an apprentice and my Instructor couldn’t tell me! Thank you very much in advance and marry Christmas! Greetings Louis
PS: I know piston helicopters like the Robinsons R22 and 44 do use a clutch system based on the variable tensionable driving belt’s. Clearly that’s not the case for those Jet-Powered Helicopters like the Alouette. My suggestions would be: - A centrifugal clutch (Idk if they’re able to manage those high revs taking into consideration the turbine would do like 30k rev‘s while the rotor is still at 0 when engaging- I guess it would just burn down) - A hydraulic clutch (with lock-up-clutch - not completely load-free while starting though when the clutch is flooded) - A normal Disc clutch (But it goes the same as for the centrifugal clutch - huge rev-difference; a lot of heat and wear on that clutch) Something like a jet engine and a clutch just does not sit right for me - seems like to much effort to avoid designing a second shaft with a dedicated work-turbine!
I do not think those choppers have a clutch. The trick is to start the engine with the main rotor in zero pitch. It therefore presents no load to the engine, only a large amount of inertia, so your batteries better be good. I would expect that the normal start procedure would require ground power. As a homework assignment: observe the two types of turboprop starting. A single shaft like the TPE331 starts with the prop in zero pitch. A free power turbine engine like the PT6 starts with the prop in max pitch, or even feathered. And why? Then we think about what prop setting presents the least load... it depends on whether you are trying to start up, or glide home... eh?
You are correct. I flew Jetstream 41's which had Garrett TPE-331 turboprop engines which are single shaft engines. When you hit the start switch, the ammeter would spike over 1000 amps for a little bit because the electric starter had to turn the entire engine including the compressor section/turbine section/gearbox/propellor to get it up to high enough rpm to light off and sustain combustion without hot starting. Most turbine engine of any size (on aircraft anyway) use starters powered by compressed air (Air turbine starters) as to start them with electric motors/generators would take such a massive motor that packaging it wouldn't make sense and the air starters are much less maintenance intensive and lighter as well. Hope that helps
@@AgentJayZ They do have a sprag clutch that allows the rotor to freewheel faster than the engine if the engine loses power, but for starting, the drive belts that connect the engine to the gearbox that turns the rotors are disengaged. On a robinson, you start the engine, let it warm up adequately, then you flip a red guarded switch which causes the drive pulleys to move further apart and engage the drive belts which happens gradually over like a minute (with lots of screeching from the belts). So in a way, it does have a clutch in that the drive belts slip until the pulleys are in the fully engaged position. Here's a vid with an explanation ruclips.net/video/oig9MA6ZjgA/видео.html
@@AgentJayZ Thank you very much for your response! Also thank you very much, Alan! The thing about it is, that at startup you can clearly hear the compressor spin up without the gearbox and rotor system spinning just as you would expect it to behave, having a separate power turbine Stage. Here’s a video of the startup of the engine: ruclips.net/video/XMP6PrPfof4/видео.html Reading about the Turbomeca Artouste I noticed that though the shafts were not mentioned, it said that it has two / three turbine stages. Do they both respective all three of them maybe power the compressor? Because if that’s unrealistic I think maybe it being described as a „single shaft“ is just a misinformation. The only source, mentioning it being a single shaft engine for me is the handout I received by my German Airforce supervisor. That handout may be incorrect there and it in fact isn’t a single shaft design! This engine also was used as an APU, also being built by continental named T51. Unfortunately because the two alouettes we have are out of service not since yesterday the paperwork we have regarding it isn’t the best. I was trying to look it up but unfortunately couldn’t find the information in our records! Once again thank you for your time and have a great day! Greetings Louis PS: I did. Research regarding the „Astazou“ engine which is based on the „Artouste“ and it was described as a „single shaft“ multiple times. The Astazou was also built in later version’s of the Alouette and it’s successors. That being said it leaves even more questionmarks making it nearly certain that there must be a clutch indeed in my understand even though it sounds very unrealistic… I’ll try to get more information about that and later on report! Thanks!
Horsepower and thrust are a way of measuring propulsive force. 1000 pounds of thrust coming from a taxiing jumbo jet engine will be created with a rear nozzle velocity of...300mph. 1000 pounds of thrust coming from a small jet trainer engine at takeoff has a rear nozzle velocity of mach 3 or more. A 500 horsepower piston engine propeller driven stunt plane might produce 3000 pounds of thrust at takeoff and while performing. Take that same engine and put it in a aerodynamically sleak go fast plane and it might reach airspeeds of 400mph+. The 1000lb thrust jet trainer will go 100-200mph faster. Equating thrust to horsepower has more in common with trying to compare apples to oranges7
It's hard to solve an equation with missing variables that substantially change the result. It's people trying to understand with something relatable asking "how much hp that thang got"... I'm going to start purchasing lightbulbs in horsepower from now on. No more 60watt bulbs. You guys have those .08hp bulbs? haha....
Slightly off the topic of this vid, but sort of relevant. I've watch pretty much all your vids, and haven't seen one that explains how the thrust produced at the accelerating nozzle is mechanically transmitted to the airframe/mounts. Love the depth of detail you go into.
That must be the one that you missed as he has done that video. In short the engine's thrust moves the engine forward. The engine is bolted to the wings. The wings are bolted to the aircraft, thus the thrust is transferred from to the engine to the aircraft as the gas exhausts through the nozzle.
I've seen said episode/vid. It's more how the thrust transmits through the structure of the engine from nozzle to mounts. It strikes me that it's a lot of force applied to some quite thin cross sections.
@@jimarcher3711 - I suppose it seems that way to you. But Aeronautical Engineers are highly skilled at calculating the forces exerted on those parts and designing the parts to withstand those forces, and then some. Have you not heard Jay refer to "thrust bearings" in some of his videos? Why do you think they have that name?
As a Mechanical Design Engineer of many years, yes it does .... For instance, I guess you'll be able to tell us what that calculates out at if it were being transmitted via the jet pipe. The ducting between the gas generator snd power turbine tends to be fairly chunky, but some of that could be put down to long term heat resistance.
I am pretty sure, one can convert thrust to power... BUT: The way you measure power and thrust has to be the same on all tests you do to get the calibration curve. Also the effeciancy of the Thrust-to-Power-Converter (aka the powerturbine/backpressuregenerator/whatever-else-you-are-using) has to be the same on all tests. To conclude: the Conversionfactor of Thrust-to-Power is dependent on the conversion device in use
Merry Christmas, LM2500 could be a nice example. As you know the big guy generates 30000-33000 sHP and 25 MW. When you tested it, you used a exhaust nozzle so you convert the gas generator to jet engine easily. when the Lm2500’s Gas generator testing (with exhaust nozzle, no power turbine), we can obtain the thrust. There is no problem but how we can get the Horsepower (ex: 8000 rpm or 9000 rpm) ? Thanks
@@AgentJayZ When you tested it, you used a exhaust nozzle so you convert the gas generator to jet engine easily. when the Lm2500’s Gas generator testing (with exhaust nozzle, no power turbine), we can obtain the thrust. There is no problem but how we can get the Horsepower (ex: 8000 rpm or 9000 rpm) ? I wonder your opinion
The exhaust nozzle is choked, meaning it causes an upstream pressure rise, because it is an actual restriction. We don't measure thrust. We measure the pressure rise and use that with the diameter to calculate gas (horse)power.
Efficiency seems to be a big variable . IC engines seem to be rated in terms of BSFC, lbs per hour per HP. The figure is usually between .4 and .5. There must be some equivalent for a turbine engine?
Turboshaft and turboprops are rated in terms of BSFC, same as piston engines (I won't call them ICE as gas turbines are also ICE). Turbojets/turbofans are rated in TSFC. Replace power with thrust.
The engine should have a thermodynamic power rating. There is some amount of available power from the fuel burnt. But that's theoretical, not practical useful output power. For example they say that PT-6 has thermodynamically (gas generator) around 300hp more than on the output shaft. Don't quote me on the numbers, but principal should be clear.
The fatal flaw of using global numbers... Depending on the model of PT6, the net output is somewhere between 550Hp and about 1900 Hp. The thermal mechanical efficiency of gas turbines is roughly similar to that of piston engines. About one third of the chemical energy in the fuel is turned into net output.
@@AgentJayZ exactly. When the engine is burning set amount of fuel, it is possible to calculate the amount of energy flowing into the system. J/s ->kW (hp). That would give theoretical max thermodynamic power of the gas generator. Take away all the downstream inefficiencies and we could get some general value. It's impractical, but people would be happy. They would know the horsepower. 😂
It only does seem counter-intuitive that there is no "clear" factor for conversion, because the fact that planes fly faster/higher with more thrust seems to be comparable to fly faster and higher with more horsepower. But it does not really make sense, because both ratings are actually outputs for different uses on different systems. Kinda like with cars where horsepower and torque are linked - but also not. There are tractors with 60 PS that plow through a field as if it was warm butter, but if you try to pull the plow with your 600 PS Supersportscar it won't move a single meter. So what matters is pulling force or speed but both setups are influenced by gearbox, fuel, rpm etc. Most importantly, max torqe and max speed are not at the same rpm. Similar for Thrust and Horsepower on the Jet engine. The engine is setup to produce max thrust at the mounting point for an airplain, so it can fly efficient. But in a powerplant it is setup for using the least fuel to produce a certain power output. So for flying you want to move a maximum ammount of air at highest possible speed, therefore you accept to make a compromise on how much fuel you burn. If needed you just add extra tanks. In powerplants you have a certain ammount of fuel and you dont need thrust. So you want to extract as much energy from the airflow and put it in the generator. So you want enough air to burn you fuel completely and than get that energy the moving air transports as completly as possible from your turbine. So thrust or horsepower are different sides of the same medal: Energy. You have a fuel that stores a certain ammount of caloric energy that gets set free in the combustion. That energy causes the rise of pressure and temperature in the gas inside the engine, so it can be transormed into mechanical work. You can now try to move as much air as possible and create a high ammount of thrust with that energy, therefore you put a turbine in the gas that has low stage count and doesn't hinder the airflow to much so it doesn't lose speed, you just want the system to be self sustaining and increase fuel input to get faster and faster by hotter and hotter air. On the other hand if you have fix ammount of fuel (it is what ou pay for as powerplant) to fulfill a need of power, you try to get as much energy out of the exaust gas with the turbine, so you don't open bypasses, you slow the gas down in the turbine as much as possible to gain mximum torqe for the input to the generator and you just leave enough torque on the engine shaft to feed itself with enoug air for a clean combustion of the fuel. That also means you dont get thrust ideally, because the mechanical work shall be put to the generator and not into accelaration of air in the exhaust. So yes, from the physics side you can calculate the ammount of thrust to the ammount of calorimetric enrgy you put in the engine. And you can also calculate an ammount of horsepower for that fuel consumption. So there is a factor between horsepower and thrust and trust and horespower will scale for that engine to that factor if the ammount of oxygen in the air the engine consumes changes for example. But that factor is dependent on the engine tuning in its use-case and cannot be just copied for another engine. Of course that does not answer the question completely, because you cpuld now make a deepdive how to define "horsepower" of an engine by asking if you talk about mechanical work on compressor/fasn blades or turbine output work or whatever you want to take energy from to measure it...
@@AgentJayZ thats interesting, especially considering the effects of the air already being high speed or ram air effect. Neat. Impressive engineering for the test stands for sure.
Actually even more "confusing": if you have the same gas generator with the same fuel and air flow (so it is fair to assume the same horse power) and then build a tubojet and a turbofan with it, the thrust will be very different! I don't know if some manufacturer has ever done this transformation (from turbojet to turbofan or turboprop) but it's a comon theoretical exercise.
As they say, there's nothing new under the sun. Both Metrovick and Whittle did it towards the end of WWII, by adding aft fans to their turbojets. It's also been done more recently at the model aircraft level. I have seen a Wren turbojet with a free power turbine added to drive a propeller.
how did u learn so much about jhet engines and made one homemade so fast how long did it take ya? will a thermodynamics course help a lot? i only took 1 thermodybnamic course in my life and it was about those adiabatic stuff and control volume control mass and enclosed work-energy area from the specific volumes stuff i forgot but im sure theres more. u keep talking about newtonian mechanics on the particle level, so will classical mechanics help a lot and did ya learn that? what if i wanna learn about rc engines and building just small jet engines i can put on a go kart where do i start??? then what if i wanna move on next to big engines what should i do? ya seem like a smart dude its like u know every nerve and fiber of that big saber engine video, u stripped it down and tested it without exploding into failure and basically knew every part of it and a bit of everything in all engineering departments needed to inspect that engine before safely running it as is likely the standard in the jet engine companies of the real world.
Well, you're biting off enough to fill the lifelong careers of more than a dozen people there. If you want to put an RC engine in a gokart, do that. Designing a working engine of any size takes hundreds of engineers working for years, and billions of dollars. And all that is done using the knowledge gathered through the work of countless scientists over the last 150 years. Me? I'm an interested amateur when it come to the science and the engineering, and the design. I'm a technician, so I follow the instructions in the manual written by the people who designed the things. If you want to learn more about how these engines work, you should watch my playlist called Your Questions Answered. When you get to episode 96, I tell you about some great books. Read those, too. Then, in order to restore or work on any engine, you are going to need the overhaul manual, and you are going to need to make some specialized tools... or you'll end up wrecking it. There: if that's not enough info to get you started, then no amount will help. Good luck with your project!
It's striking how long turbines have been limited mostly by materials science alone - the temperatures at which things melt or lose strength. The mechanical engineering is so optimized. It's said the Pratt & Whitney F135 approaches 2,000°C (when all the coatings are in good condition). Is that going to be the end unless new materials are discovered?
The only other possibility is to use very clever fluid mechanics to maintain a layer of colder gas on the turbine surfaces, while hotter gas can still pass by them and transfer momentum to them. With the high speeds and high turbulence involved in jets, I suspect even a lab demonstration of this working in a stable way would be very impressive. As fluid flow simulations continue to get better in terms of computing power and result accuracy, there is still a chance something might be found. There's also a chance that a completely different way of making an engine will be invented that can rewrite the rules. When you think that steam turbines driving pistons with steam pressure was the 'obvious' way to do things that couldn't be improved on before the Parson's turbine and that Whittle only get the go-ahead to develop his jet engine designs because the UK government heard the German's were interested in it - the powers that be in aviation didn't see much value in the idea in the time of piston engined planes, there's always a chance of a completely new paradigm showing up.
@@peglor Using a cold gas layer to shield turbines from hot temperatures has been done for decades. It's not some fancy concept only seen in a lab - most modern engines utilize it. It's called film cooling - "cold" air (cold being relative here) is routed from the compressor and blown through cooling holes in the turbine blades/vanes surfaces and through the trailing edge, in such a way that the airfoil is "coated" in a cold air film to greatly reduce the heat flux into the airfoil. In many modern engines the first stage turbine is operating at temperatures above the melting point of the metal, and this film cooling prevents it from melting/failing.
@@ASJC27 I was aware of this being used in some situations, but as it is currently implemented, jet performance is already on the thermal limit, so a better way of doing it is needed. Building a cool boundary layer at the leading edge is too obvious not to have been already tried, so I suspect it reduces performance.
If you used ethanol instead of kerosene in a gas turbine, would the fuel control manage to inject twice the volume of fuel? Does it have that kind of overcapacity built in without having to modify anything?
Yes. The difference in emissions might make the increased cost worthwhile in some installations. The power output would not change, because the engine is limited by turbine inlet temperature. However much fuel, of whatever type, will be sprayed in by the fuel control until that temp is achieved.
My humble thoughts... Horsepower is a unit of power. Pounds of thrust is a unit of force. You simply can't convert those units. It would be like trying to convert a unit of length to a unit of temperature. Or am I misunderstanding what is meant by "pounds of thrust" in the gas turbine world? Is this similar to the relationship between torque and horsepower in an automotive engine? They both say a lot about what the engine "can do" but they represent two different things. Interestingly enough I ran the conversion calculations for your two examples and got 1.3 hp per lb thrust for both examples... coincidence? (7MW = 7,280 lb thrust. 15,000hp = 11,500lb thrust).
@@AgentJayZ Let's say jet fuel has an average energy density of ~45MJ/kg (~20,000BTU/lb) and a density of ~800kg/m³ (~7lb/gal), if the 777 engine burns ~7ton/hr in flight (~3.5ton/hr per engine; ~7,000lb/hr; very economical), then a nominal Pegasus horsepower [php] (we should register that) can be calculated as 45MJ/kg x 3.5ton/hr = ~55,000php. That would be the nominal horsepower if the engine is 100% efficient and the energy source only comes from the fuel. For the J79, a fuel consumption of ~17ton/hr (~90gal/min x ~7lb/gal; thirsty bastard) with afterburners translates to ~300,000php and ~130,000php without afterburners (~40gal/min). For the F-18, 36,000lb/hr per engine on afterburners translates to ~285,000hp. For the efficient SR-71 Blackbird, ~22,000lb/hr per engine translates to ~175,000php with afterburners. For a car engine, 30mi/gal at 50mph (50mph / 30mi/gal x 7lb/gal x 20kBTU/lb) = ~90php.
W=T*V, V for speed so you can only has full power in ISO and sea lever; the idea of think a airplane engine and industry gas turbo was okay but if you has different fuel control it may off set.
Yo big jay. How many different fuels will your turbines run on? Not the black bird or new equipment. Just what you work on. I’m able to use kerosene, jet1A,or diesel fuel in the small jetcat engines. Just was wondering.
Gasoline is a specified alternate, but it's hard on the fuel pumps. Octane rating does not matter. A much better alternate is home heating oil. It is very close to diesel, and of course it's less expensive because it is not taxed like road vehicle fuel. We have run Afterburning J79s on the stuff, and it works without any problems.
Wow. So both engines actually produced a ratio of 1. (1lbt was roughly equivalent to 1kW) 7280 lbt engine produced 7MW or 7000 kW. 11500 lbt engine produced 15000hp which is 11194 kW.
regarding the discussion about the equivalent power to thrust ratio, and how the book mentions 2:1 I'm assuming that even when operating the engine with an output shaft, it still produces "some" thrust with the exhaust gasses? So maybe this thrust could equate to some equivalent power that cannot be converted to mechanical work at the output shaft. Could the book be taking that into account to measure the equivalence? As in, it produces X ammount of power but only Y% of that thrust can be harvested at the output shaft? And the other (100-Y)% is still converted to work in accelerating air mass? If that makes sense.
A turboprop certainly produces some residual thrust from its exhaust. The Bristol Proteus engine of the 1950s was rated at 4,250SHP going to the prop at its take-off rating, plus around 1,000lb of thrust.
It's impossible for all the energy added to the gas flowing through the engine to be completely converted to mechanical work at an output shaft. If you think about what 100% conversion would mean, it would result in the exhaust gas exiting with the same energy as it entered the engine, so at room temperature and pressure and with zero velocity. The problem with zero velocity air is that then there's no way to move it out of the way of the new air flowing into the engine, so the engine will stop dead. There are clever theoretical ways of getting around this by having the air exit at lower than ambient temperature or pressure so there's energy left over to give it a non-zero velocity so new flow can enter the engine, but this isn't practical in any real world setup I'm aware of. Engine designs like the Atkinson cycle engine are an attempt to get close to the ideal maximum work extraction by setting up a piston engine so it has different expansion and compression ratios. A version of this is implemented in most hybrid cars by leaving the inlet valve open for part of the compression stroke, so it flows back out the inlet for part of the compression cycle. This means less gas is compressed than the cylinder could normally compress, but after combustion this smaller amount of gas is expanded to the full extent the piston allows it to. This means more combustion pressure is turned into work pushing the piston down. The downside of this is that an identical engine will make less power per kg on the Atkinson cycle compared to the normal 4 stroke Otto cycle, though it will have better mpg, even when the lower max power figure is accounted for.
@@peglor That was an awesome write-up and thank you for taking the time. I just want to point out, and I'm mentioning to perhaps steer the conversation a bit: I am aware of these concepts and they are off-course totally correct and valid. What I was trying to discuss is not the general aspect of power efficiency in regards to fuel caloric intake but more specifically this: The video does some practical measuring to come up with a practical ratio of mechanical power to thrust output figures of 1:1 on practical applications for each scenario, whereas the book mentions that the ratio is 2:1. And I'm wondering if this discrepancy is due to the book mentioning not a practical comparison, i.e. "an engine that practically outputs 1000lbs of thrust when set up as a jet aircraft engine will produce 1000hp of mechanical work when setup to drive a mechanical shaft", which is a statement that already takes into account the different conversion efficiencies of producing mechanical work on the shaft or thrust, or if it is referring to a comparison of the relative output figures, i.e.: "an engine set up as a shaft output engine will produce twice as many horsepower as it will produce pounds of thrust (simultaneously)" Now, taking into account grahams comment above this last ratio would more likely seem to be 4:1 so that would also contradict the figure. So that's probably not what it's referring to either. So I'm mostly trying to figure out if interpreting the figure the book is mentioning will explain somewhat why the discrepancy between those ratios is so significant.
@@stathisbikos6563 I think part of the issue is that a lot of the energy in jet exhaust is heat, so while the momentum and pressure can be captured and turned to mechanical motion, the heat is much harder to capture (Some can be captured by the behaviour described by the PV = mRT gas equation where reducing the pressure will reduce the temperature, but it would take a lot of expansion to do this and the bigger the expansion space the more heat will be lost through the outer walls, so the less worthwhile the expansion is). Using jet engines as combined heat and power setups rather than just for generating mechanical power can get figures over 90% efficiency in some cases, so a more equal thrust to power comparison might be to look at thrust vs. the sum of mechanical power and heat from a CHP system using the same engine.
I realize I'm being pedantic here but are the fuel atomizers different between ones that accept aircraft grade kerosene and natural gas / propane? It seems with the LM1500s your shown tested, some of the plumbing looks a bit different.
No, I don’t think you’re being at all pedantic. It’s a very fair question from someone who isn’t familiar with the technology. For the same heat release rate in the combustor and the same power output, the volumetric fuel flow of gas will be much greater than for a liquid fuel, and the burners can look very different. I was familiar with the gas and dual fuel burners for the Industrial Olympus and responsible for the design of the gas and dual fuel burners for the Industrial RB211 - but it’s all a long time ago now. My recollection is that we did manage to use the same basic external profile of the RB211 aero burner feed arm for the gas burner, but had to increase the internal passage size. The 'airspray' head of the liquid burner was completely replaced by a simple ‘pepper pot’ injector, with a ring of holes. For the dual fuel burner, it was a case of trying to get a quart into a pint pot. I had to devise a completely new two-piece casting for the feed arm, with a ‘fatter’ external profile, which could be retrofitted into the existing engine. The assembly was brazed together, with two tubes passing through the gas passage to carry the liquid (diesel) fuel. And perhaps I should explain the term ‘dual fuel’. It means that the engine can change over from liquid to gas, and vice -versa, while running under power, and can even run on a mixture of the two. You’ve noticed the different external ‘plumbing’ on a gas-fuelled engine. Again, that's down to the significantly greater volumetric fuel flow - and, of course, a dual fuel engine has to have both liquid and gas manifolds.
As mentioned in the video, and in the description, my Fuel Nozzles series of videos shows the difference between liquid and gaseous fuel nozzles for the LM1500/J79.
@@AgentJayZ Thanks! Sorry, I did actually watch that video some time back and did not remember when I commented. I've always wondered if the engines would pass the 'tequila test' like the Chrysler turbine car engine allegedly could, but it would take an awful lot of tequila to run an LM1500. Also, I'd probably rather keep it for myself than see it burned 😝
@@grahamj9101 Absolutely fascinating! Thank you! I had figured 'dual fuel' would probably mean an overhaul where the atomizers were changed, but the fact that you designed some that could do both is fascinating. I suppose I realized it was thermodynamically possible (a gas turbine engine combustor is just a heater at heart) but not practical to build. Are dual fuel nozzles standard or is that a specialty type need? Also, are there any appreciable differences between Diesel and kerosene?
@@KronosIV A duel fuel system wasn't standard, but was a special order option for a customer - and there were quite a few such installations. Dual fuel nozzles were only fitted on gas generators for dual fuel installations and, as I recall, the gas generators had a specific designation. It meant having two completely different fuel systems, of course, with a control system that managed both for fuelling proportionality during a changeover. While a burner designed originally for kerosene could handle diesel equally well, there could be problems with 'coking', ie, soft carbon build up on the burner and in the combustion chamber head. For the same heat release, the combustion chamber walls ran hotter, because of the more luminous flame when burning diesel. Also, the exhaust could be rather smokier, particularly at lower powers. I recall being in Portsmouth Harbour on a sailing trip years ago, opposite the Royal Navy's base there. A Type 42 destroyer (with two Marine Olympus, two Marine Tynes) started its engines, resulting in clouds of white smoke and the inevitable stink of unburnt diesel.
HP is about the same as kinetic energy of exhaust gas per second at engine exhaust nozzle? Another question, why the by pass route of big turbo fan engine is not streamlined (pipes etc disturbing the flow)?
Modern turbofan engines have a cover over the core, so the bypass duct is more streamlined. Every extra part costs money, and selling engines to aircraft manufacturers is an extremely competitive business.
The bypass annulus of the early low bypass engines was often not well faired (ie, ‘streamlined’). However, the bypass annulus of the modern high bypass engines is invariably well faired. Take a look elsewhere on RUclips for videos of engines with their cowlings open. There's a good clip of a LEAP engine with its cowlings open and you will see that the rear cowlings form the inner and outer walls of the bypass duct. PS It occurs to me that you have been misled by the fact that, when the cowlings are open you see all the 'plumbing'. However, take a look at the video I've suggested and you will realise that the pipework is covered by the inner wall of the rear cowling. And all the pipework, etc, that you see beneath the front cowling is on the outside of the fan case.
got a question, tried to find it mentioned before but can not find it so here we go : If you got a gearbox connected to the N1-shaft and it brakes and stops the N1 fan completely .. is it likely that the N2 continues to run .. ( although with somewhat disturbed airflow from the front ?
If a geared turbofan has a failure inside and stops turning, that might cause the N1 system to stop, but this is extremely unlikely. If the input shaft to the gearbox fails, then the N1 system will have insufficient load, and may overspeed, but this is extremely unlikely. The N2 system in your hypothetical engine could continue running, but since the N1 system makes most of the thrust the whole thing would be quite ineffective. If anything like what you describe happened, there would be alarms going off, and the pilot would shut down the engine, if it didn't already shut itself off. I think modern FADEC systems are looking for this and many other problems about a hundred times every second.
I am going to be pedantic (as I am so often) and object to the use of N1 and N2 to refer to the spools of an engine. Those terms should be used for the rotational speeds of the spools, not to define the spools.
@@AgentJayZ thank you for the answer! Absolutely makes sense , and yes in 99.99% of the cases the engine would have been shut down straight away manually when detected. I understand it is a very unlikely case, I was assuming that the stopped N1 Fan and the stopped turbine would cause to much issues with the airflow for the N2 to even continue to run. But I guess it could continue to run slowly by itself without it´s N1 friend :)
Your imaginary thought experiment could only take place without the fuel control and all of it's sensors. Such a case would never happen. Who would attempt to start and run an engine without the fuel control installed and working properly? Thought experiments are fine for break time banter, but that's all.
Would it make any sense to use radioactive isotopes of air molecules to directly observe turbulences inside the engine and use that data to find out a way to reduce Reynolds number right to zero ? And had you ever heard about exoskeletal turbojet engines ?
The flow inside a jet engine, or around anything in motion through a fluid, can now be modelled to a high degree of accuracy using Computational Fluid Dynamics (CFD). It's been around and in use for many years now. Messing about with air seeded with radioactivity would be utterly foolhardy. There is no way that Reynolds Number can be reduced to zero, except by reducing the flow velocity to zero. Any fluid that is in motion can have a Reynolds Number ascribed to it, relative to what it is flowing through or around. As someone who had a career lifetime in the design of gas turbine engines, I really don't understand the use of the term "exoskeletal" in relation to a jet engine, turbojet or otherwise.
@@grahamj9101 It seems to refer to a jet engine that has the bearings for the compressor/turbine blades on the outside a drum holding the blades instead of inside. In theory the advantage is the blades are now in compression not tension so you can use ceramics but making bearings that work at the velocities and dimensions required isn't solved yet. (No actual opinions on it, just got curious and googled them)
@@hannahranga To make rolling element bearings the diameter of the outside of a compressor casing, while rotating at the same speed as the existing bearings, would probably need an aerospace grade of Unobtanium. The nearer term solution will most probably be the utilisation of composite materials, so that blings (integrally bladed rings) eventually replace the blisks (integrally bladed discs) that are currently in increasingly common use.
Question it would be cool to hear you answer: what is the effect of heavy rain on a turbojet or turbofan in flight? I heard somewhere it improves performance due to the increased mass transfer. But it must at some point become a detriment and eventually stop the engine.
Rain is insignificant, no matter how much. A modern turbofan can not be stopped by a dozen 3 inch fire hoses aimed directly into the inlet. Have a look at water ingestion testing. These engines are amazing.
There is actually an example of fire crews stopping an engine with their hoses - but it does go to prove how difficult it is to stop a big turbofan with water. Check out the Qantas QF32 engine failure in 2010. It's been discussed on this channel more than once, so I won't go into the failure of the No.2 engine. However, it severed the controls to the No.1 engine, which ran for about 3-1/2 hours after the emergency landing. The engine, having been doused with water and foam for much of that time, finally flamed out, after being flooded with massive amounts of foam. My suspicion is that the combustion process wasn't simply overwhelmed by the sheer volume of water and foam, but that the compressor aerodynamics were progressively degraded by ingestion of the foam, contributing to the flameout.
@@AgentJayZ maybe im splitting hairs here, but theoretically wouldn't it boost power if only by a tiny percent since water going from liquid to gas takes away heat from the air making it cooler making it more dense = the engine making more power? Edit: you're 3000 times better than my teachers in module 15 in a certified 147 school
a: any natural rain is insignificant in terms of hurting the engine, and also in terms of helping the engine. Yes, theoretically it helps increase mass flow though the engine, and it reduces combustion temp... just like theoretically I am lighter at the top of my stairs because I am farther from the Earth. To boost power in a large airliner turbofan, you need gallons of water per second, going through the fuel burning core. So not enough, but also, turbofans eject anything heavier than air to the outside of the airflow path, which is the bypass duct, so not into the core.
Off topic: Does anyone have extensive experience with the engine used in the U.S. B57? I was in the Cal ANG when we had a B57 come by TDY for a few weeks. I swear, every post flight, I poured in 3-4 quarts of lube oil. What was annoying was that the filler was in a gawdawful position and it always looked full. I was told to keep pouring until it overflowed. Comments please?
A one second search of Goog, starting with this: Martin B-57 Canberra. Yes, we have tested those engines. I have posted a video of the run. They have a very strange oil system. The rear main bearing is lubed by a total loss system, at a rate of about one drop per second, with the oil dumped into the exhaust stream. It says in the manual that it takes oil about 20 minutes to make it from the reservoir to the rear bearing. There's no way to look in there, so you have to have faith that oil is flowing/dripping. If it isn't, then in about 5 minutes the bearing will fail. I'll bet there was a maintenance decision that it's better to overfill the reservoir than to have even the slightest chance of going dry... using oil at 3600 drops per hour...
@AgentJayZ, John from Australia here. I see it like this, in a thrust rated engine it takes X Horsepower to create X thrust. My reasoning is this: to spin the compressor at full thrust it takes HP, lots of HP. With a big fan on the front, you'd have to add to power turbine output. In an engine rated for shaft HP, it's rather obvious. Unless there is a shaft output creating rotating torque, you'd have to use Horse-Farts as there is no torque. No rotating torque, NO POWER! You could just convert the BTU output to HP, but not really useful.
This topic has long been argued about, including several times on this channel. I have a copy of a book (I think AgentJayZ also has a copy) on the subject of jet engines, written by a well-respected author. In it he states that a jet engine, running at maximum thrust with the aircraft stationary at the end of the runway, is producing no power (or words to that effect). However, I fundamentally disagree. The engine might not be producing any useful power in accelerating the aircraft. It is, nevertheless, producing a massive amount of power in accelerating a massive amount of hot air, which can be calculated and turned into a horsepower figure. I haven’t seen the term used for some time but, years ago, R-R used to quote an equivalent gas horsepower (EGHP) figure for its industrial gas generators. This was effectively a measure of the power potentially available in the gas efflux from the exhaust unit, for which a horsepower figure was obviously calculated or inferred. In the past, I’ve made the point that I/C engine manufacturers will quote maximum power figures for their engines taken from dynamometer testing, where the engines are doing no more than producing heat by heating water or generating electricity that is being turned into heat. So why is a power figure for a stationary I/C engine on a dynamometer any more valid than an equivalent power figure for a jet engine on test?
@@grahamj9101 It's all depends on whether you're measuring its power as a device for imparting kinetic energy to the airplane, or its power as an open-air space heater.
@@MatthijsvanDuin You’re being a bit of a smart****. I’ll go along with my knowledge and experience of a career lifetime in the design of gas turbine engines, industrial, marine and aero.
Jay, Merry Christmas and thanks for another year of turbine nerd content. I saw this photo of an French aerotrain with a wild exhaust nozzle; can you tell me why it's shaped like this? It looks jet-ish in the front and a lot like my propane grill in the back. ruclips.net/video/ND3MegqYQFA/видео.html
Very interesting. That nozzle on the back of Train 2 looks like a combination of 60s era hush kit nozzles meant to reduce noise, and the back end of the F-117, intended to reduce the heat signature of the exhaust. I love all the old, weird stuff. Technology does not have enough weird nowadays...
Think monorail. The defusion nozzles at the rear of the vehicle is, as I recall from popular mechanics, aerodynamic only. All the propulsion is provided by the jet engine mounted on the strut structure overhead.
More rare than when? Those don't go into the F-4. I have posted many videos of test runs of them. What do you mean by access? To see? To touch? To buy? A championship level player in the league of Vague!
I think your math is wrong brother, 15,000 hp is 11.19 Megawatt, so follows the same rough 1:1 relationship between MW and Thrust. Great vid, nice to think through this stuff. I always thought Turbines had direct relationship to HP, turning shaft has torque and RPM....may be tough to measure, but theoretically it's calculatable and measurable. I'd guess the newer engines do a much better job of turning rotational power into thrust (efficiency), so thrust measurements to hp correlation is likely very different between eras..
As I've suggested in another comment, there is a potential problem in that, for an aero engine (turbojet, turbofan, or whatever), the take-off thrust is usually the most commonly quoted rating, with publicity in mind. In contrast the maximum power (aka peak) rating for the equivalent industrial gas generator (whether quoted in SHP or MW) is normally a derating relative to the T/O thrust, as it may be used for hours rather minutes. Consequently, there may not be a consistent relationship between the two from one manufacturer or engine type to another. For applications such as gas pumping, there is a usually so-called base load rating, which is a further substantial derating, with gas generators running tens of thousands of hours between overhauls.
HP is work done over time You can produce infinite amounts of thrust but if no movement no work is done that’s why to convert thrust to HP it needs to be at speed and see level
Ahem... I have an announcement to make: The air is moving, being accelerated from zero to over one thousand km per hour. Accelerating a mass, takes force. Force times distance equals energy. Force times distance divided by time is the actual definition of power. Work is being done by a stationary jet engine, because it is moving air. If you can not understand that, you are an infant. Over... Thank you! Come again!
It is still producing power, just in a different way: the engine is not moving, all the power is going into the air, ultimately heating it up through friction with other air molecules. So the power is just all going into heat
I agree with AgentJayZ. However, please take a look at what I describe as my "party piece" comment somewhere below. I quote an effective horsepower figure of around 130,000 for Concorde in supersonic cruise. I recall that, years ago at R-R Bristol, on occasions I had to assist in dealing with letters and enquiries from the general public. There was one individual who just would not believe that 130,000 HP figure, insisting on comparing it with the power quoted for the massive steam turbines of the ocean liners of the day.
yes 1 watt is 1 volt ampere .. ... or in laymans terms 1 volt at 1 amp is 1 watt ... also all the other maths like 0.5 volts at 2 amps is still 1 watt etc ..
wouldnt a change in fuel require a potential change in the combustion chamber ... sure some fuels will still self regulate to stable in the same or smaller chamber BUT some may take longer and need a slightly longer chamber to work optimally .. . from all I have read and seen it seems that how fast the flame burns or slow determines the size of your combustion chamber ... and lower octane fuel needs a bit more space while higher octane needs less .. to do the same job .. the part I am not sure about is how much of a difference the different fuel octanes or types change that size ... lets same old leaded pump gas might need an 8inch chamber while 97 octane no lead may need only 6 inches ... and jp4 may need 6.5 inches etc ...
It'll burn any hydrocarbon liquid fuel with no difficulties. What does that mean? Alcohol, gasoline of any octane rating, diesel, home heating oil, straight kerosene, or actual jet fuel are all just fine, with an adjustment on the fuel control (one dial) for specific gravity. The engine sense EGT, and controls fuel delivery to reach a set Temp.
Nope. All iron based metals have the same density. And no other than iron based metals are suitable for jet engine. Aluminum is already used on J-79 parts where it could be used.
Some of the compressor disks are made of titanium alloy. It was a fairly new material then. Modern fighter engines use a lot more of it. For example the LP compressor cases of the GE F404 are titanium instead of steel.
The extensive use of steel in the J79 gave GE an advantage in turning the engine into an industrial gas generator. In comparison, the Olympus 200 series engine, as used in the Vulcan bomber, had an aluminium (not 'aloo-min-um') LP compressor. To make the engine robust enough to become an industrial gas generator, the LP compressor was redesigned in steel, whilst retaining the same aerodynamics.
If a stationary jet engine produces no propulsive horsepower, then how the hell does the plane start rolling. Point blank, it does work. Just like a floor does work to push back against my feet.
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Keep in mind that both power turbines and electrical generators have an efficiency factor, so measuring the electrical power is less than what the gas turbine is actually making.
I’m glad you explained the different fuels and how they compensate between them. I had wondered what they did and if the power changed with different fuels. Makes sense that they’d be able to end up being able to just adjust the fuel flow to get to the desired temps.
I’m so used to piston engines it’s sometimes difficult to wrap my head around the turbine engines.
Back in the 1960s, when I began my career lifetime in the design of gas turbine engines, industrial, marine and aero, the Industrial Olympus was just entering service at a rating of 17.5MW. It was derived from the Olympus 200 series engine in the Avro Vulcan bomber, which had a take-off rating of 17,000lb thrust. However, the 17.5MW rating was effectively a derating from the aero T/O rating: the industrial gas generator would not have lasted very long at the aero engine's T/O rating - nor would the aero engine.
The same basic gas generator, with an improved combustion system based on that of the engine for the Concorde prototypes, plus a cooled HP turbine, designed in the early 1970s, was rated at 30MW. This is the Industrial Olympus that AgentJayZ has shown us in the past.
Always good to hear of your experiences. I think many of us dream of having a career like yours.
Great to see you again! I love listening and learning from your experiences. Hope you have a great Holiday Season!
got the math at the end a bit tounge tangled i think; one megawatt is 1000 killo watts, or 1 million watts (1000 killowats), making it 1 kilowatt of power roughly equals one pound of thrust, or 1.3 ish horsepower per pound
You nail this. It is all about the frame of reference as soon as people try and do apples and apples comparisons but then fail to treat it as an energy in versus energy out black box model. And the comparisons between a turbojet and a piston engine measuring horsepower at the fly wheel? C’mon!! Madness.
Right?! The inconsistency is really annoying. If we want to calculate actual propulsive power delivered to the aircraft, then stick to velocity * thrust for both jets and propellers.
"Please go to the cat videos, thank you" I just spit coffee ALL over my computer screen. BUWAHAHAHAHA
the wealth of knowledge you have provided over the years is astounding,, thank you
AJZ Happy Holidays thanks for an informative and entertaining video. Having worked on J79 (LM1500) in a USN Patrol Gunboat BITD which was rated at 12,900 SHP and drove the 240T 165' boat to 45-50knts. Also after Navy I worked at Lockheed ADP who built the F104 which also had a single J79 W AB and did Mach2.2+. I also worked at a So Cal Utiltiy for 31 yrs where We had 8 PW GG4s (J75s) exhausting on expander turbines that created 180MW of emergency peaker electrical power in about 2min from turning gear to 3550 srpm where field brkrs closed and at 3600 srpm w system synchronized. Stay Healthy.
As it’s Christmas, can I recite my party piece, please?
If you have an aircraft in horizontal flight at constant speed and you know (or can calculate) the thrust of the engines at that flight condition - or you know (or can calculate) the drag force on the aircraft, then you can work out the actual horsepower that the engines are effectively delivering.
You know the velocity of the aircraft (in ft/sec). You know the force that the engines are working against (in lb force) - and thrust equals drag, of course. You can multiply one by the other and divide by James Watt’s magic number of 550 - and, hey presto, that is the horsepower figure for the engines at that condition.
Do that for Concorde in supersonic cruise at 1,350 miles /hr, at an altitude of 58,000ft, where the four Olympus 593 engines were producing 9,000lb thrust each. The answer? Near enough 130,000 horsepower.
And a Merry Christmas everyone!
Just multiply the thrust in Newtons by the exhaust velocity in m/s to get the power rating in W.
The only thing you said that I understood was "go to the cat videos" but after 25 minutes I was still watching this.
Jokes aside, this was a great explanation to a question that on the surface seems very simple, but in reality is like trying to compare oranges to lemons.
more like oranges to water buffalo ... doable but not very useful lol
Greg did a good video on the horsepower of the F-14
I was driving with a mate back when I was young, and a semi was 2 metres from the back of our car when a front tyre blew out. Oh man I thought I'd not get a chance to grow old. No turn offs available so I helped the driver steady the steering at 75MPH. Then we ended up on a hill and the wheel nuts were rattle gunned on. Had to find a large boulder to mount the L shape tool onto, while getting the driver to drive forward gingerly. Took a while.
That's a good idea, I have a M35a2, Duce and a half. The front tire is bald and I want to put on the spare, I've stood on the breaker bar and it didn't care at all, about 300ft/lbs. I'll put a block of wood under the wrench or something. Thanks.
Merry Christmas and a Happy New Year to all!
Hey, I love cat videos. But I like your videos even more. I've learned a lot from you.
JZ, I’ve been thinking when an engine is fixed to the ground and running it is moving and doing work. Not only is it moving the air as you explain, it’s also changing the rotation of the planet. It’s just hard to measure 🤣
"please go to the cat videos" ROFL That was awesome!
My neighbors woke up on that one. Like most well-aged dry humor, JZ might be undervalued for his talent in this regard.
Oooooooh! Greg's airplane and Angent Jayz, thurst vs Hp!
This is the most interesting internet discussion ever..
Always a pleasure to listen to both of you guys!
Merry Christmas and Happy New year!
Our current project at work is a little number we call the _GE9X._ The horsepower that we pull out to use to power accessories alone is quite amazing.
Bit late to the party, but really great to see your take on it, talking about the actual usable power that the engine can make. This contrasts nicely with Greg's video on the Tomcat's horsepower, at a very different take, looking at propulsive power usable for overcoming aircraft drag and accelerating it (which is effected by its thrust directly). As you said in the beginning, no equation, and tons of equations, depending on your point of view. Thanks.
Always enjoy the videos. Thank you
There are two engine options on the Boeing 787. A General Electric GEnx or a Rolls Royce Trent 1000
May You Have A Merry Christmas And A Happy and Healthy New Year
merry christmas jay :) hope you're safe!
I've always used a very rough rule-of-thumb as 2.5 lbs of thrust makes 1 hp. I used to fly a Citation C-550 which had 5,000 lbs thrust in total and it felt like it had about 2,000 hp. When I was flying 747's I once stuck a car accelerometer on it for one take-off and it came up with 72,000 hp, which was about 2.5:1 with the thrust.
A rough conversion is the LM2500, which is also the core of a CF-6, which was sometimes used to power the earlier models of the 747. Early LM2500 engines, which had an integral power turbine and a mechanical shaft output, were rated at about 45 thousand Hp. 66 thousand ft-lbs of torque at 3600 rpm. So 4 of those is a lot of ponies.
@@AgentJayZ Yeah I've flown 747's with CF6-50's and -80's. Best engine of the three options I reckon. Set power with N1 rpm, not EPR, a more reliable way to make sure you're getting the right power.
For a turbofan....how much shaft horsepower would it take to turn the fan at takeoff rated thrust? It's a lot. When talking to people I always give it 1:1 ratio. 60,000lbs of thrust takes roughly 60,000 horsepower to turn the fan at that RPM. Rough estimate, but it's ballpark.
JayZ. Good to see you back. Hoping all is well up north and that your holidays and upcoming year are the best ever. Thanks for the interesting, no, fascinating content. Keep up the good work.
Thanks for the video, Mister Agent - and I hope you have a great holiday season.
Four Lm2500 engines power the Spruance DD-963 class destroyers.
Thanks to point out that this engine is an power turbine version of the Cf-6 aeroengine.
G'day Jay,
Yay Team !
I was wondering where you'd got to, good to see you back in my feed.
I'm olde Skool mate, my idea of a HorseyPower is the 50-pound Wooden Bucket with 10 Imperial Gallons of Water weighing 550 Pounds gross between them, with a 1-inch diameter Rope (officially weightless according to the allegation !) leading straight up the Mineshaft and over a 1-ft diameter Pulley, harnessed to a Horse...; the Horse walks away at 1 Foot per Second (0.68 mph), and thus the 550 Pounds is lifted vertically at 1 Foot per Second.
Last time I actually used the equation was "test flying" my eBike on the neighbour's Driveway, with me and the Bike with 2 spare Batteries (220 pounds) travelling 1 Km in 3 minutes and climbing 40 metres (126 ft) at an indicated average groundspeed of 19 Km/Hr.
I make it out that the Vertical Lifting equates to the Hub-Motor delivering 0.16 Horsepower to lift the weight up that height in that time...; and I pluck from my Arse the guess that the work overcoming Aerodynamic Drag plus the work overcoming Rolling Resistance (bouncing over the rocky Dirt Driveway) is about equal to the work of lifting the Weight in the time.
All done without my input to the Pedals, so the "250 Watt Motor" does 0.32 Horsepower worth of work, and with a Horsepower being "half a Columbus (1492/2= 746 Watts !), then a third of 746 equals 248.6 Watts of Twistiness and 1.4 Watts wasted as Heat...(the Motor warms up from 28 degrees C. to 31 during the 3 minutes !)
So, them there Chinamen sure seem to know what they're doing, when it comes to making Electric Bicycles, and the Maths more or less works out.
Comparing Horses to Watts to Twistiness in a Shaft to Air Displacement and Wind to Thrust is always goanna be an approximation founded in Guesswork, but it feels good when the numbers indicate that our Guesses are "somewhere close to reality" ; I guess (!).
Anyway mate, to collect your reward (having a few giggles about Biggles !), please feel free to backtrack me to my Videos, therein to find,
"The Aviator's Moustache..., Mystery Solved !"
Its only 56 seconds duration, but it relies on a New Scientist magazine Photo Feature, so it might be not-wrong (?) !
Happy Solstice Festival !
Such is life,
Have a good one...
Stay safe.
;-p
Ciao !
As you will see from my party piece comment, what James Watt applied to Dobbin can be applied to something a little more advanced, such as Concorde, although that's passing into history now too - but at least I got to fly on her.
Merry Christmas!
@@grahamj9101
G'day,
Yay Team !
You flew on the Concorde ?
Yikes !
Well done mate, welcome to the Club for Aeroplanologists who've flown things which are now safely stashed in Museums !
I was literally away off at the opposite end of the spectrum from the Concorde.
To see what took me for my first solo, title-search YT for,
"The 8-Hp, 1975, Red Baron Skycraft Scout ; World's 1st Legal Minimum Aircraft !"
I was it's 3rd owner, it was my first Aeroplane, when I was 17, and I didn't do anything actually "pioneering" in it ; but in 1978 I was the last person to ever sit in it while wondering how to get it back down on the ground, without making a mess of everything !
Such is life,
Happy (Summer, here) Solstice Festival !
Have a good one...
Stay safe.
;-p
Ciao !
@@WarblesOnALot Yes, I flew on Concorde as a guest of BA, because I was a member of the team at R-R Bristol that kept her Olympus 593 engines turning and burning. Periodically, they organised an engineering meeting at JFK and made a day trip of it. However, when it was my turn, there were too many paying passengers and we had to stay overnight in New York.
I like that answer, "It depends,... or who cares?!" I'm good with that.
It is funny why it is so important to concert thrust to horse power or kW. My light bulbs makes Candela / Lumen, why don't we convert this to Watts too.
Thanks for all your great videos, I have learned a lot from them
My simplistic understanding is this .....
Automobile engines are not typically described in terms of thrust or units of force because they do not produce a direct force to propel the vehicle forward in the same way that a jet engine does.
In an automobile engine, the power output is used to turn the wheels of the vehicle through a transmission and other mechanical components. The force that is produced by the engine is transmitted through the drive-train to the wheels, which then apply the force to the ground to move the vehicle forward.
Therefore, while force is involved in the operation of an automobile engine, it is not the primary output of the engine, and it is not a direct measure of the engine's ability to propel the vehicle forward.
In contrast, thrust is the primary output of a jet engine and is a direct measure of the engine's ability to propel an aircraft forward through the air.
Therefore, thrust is a more useful measure for jet engines, while horsepower is a more useful measure for automobile engines, because it provides a direct measure of the engine's ability to turn the wheels and move the vehicle forward.
Yes, all good. With the LM1500 and J79, we have the opportunity to compare the thrust and Hp of two engines built on the exact same gas generator. The part numbers of the rotating bits inside are the same, and so are major shafts and cases.
Same story with the LM2500 /CF6.
@@AgentJayZ thank you for demystifying the most sophisticated of human creations 🙂
Merry Christmas sir. Hope you have a fantastic New Year
Stereo amplifiers are rated in watts. By how much power they deliver to the speakers, which rattle air to make sound. At jet exhaust, the power of the air being accelerated also is 'wasted' to make sound. That can be measured in decibels. As loud as jets are, the sound wattage is only a tiny fraction of the acceleration wattage. Accelerated air + vibrating air = power out. Little side note.
I built a sub using a JBL 18" that has a maximum continuous sine wave power rating of 30W... recommended for use with amplifiers rated at up to 1200W RMS.
Different standards!
Fantastic! Thank you for your in depth explanation!
Horsepower is defined as the amount of work over time. That to me seems very vague. How do you measure work? What is work? In a car it's could be how much it is pushing to car to overcome weight and friction. How can that be measured in a jet? Or driving a generator? You are right, it can be confusing. Going to watch cat videos now...
Yep the problem is that if the frame of reference is not based on energy in and energy out - then the analysis is totally arbiter and open to apples and oranges comparisons.
Did search for but only found half cutaway J79
had a really good search, wanted to make a laminated one for my wall
Why do I watch, because I use to repair gas turbines and screw turbines, I balanced them plus ultrasound the turbine blades. But now retired and want to see if anything has changed in the industry. But it's all the same.
consider the efficiency of the pt, a jet generator can put out 10x energy per sec but the pt output may have 5x at the 50% efficient pt+electric generator combo
I did some rough thrust calculation based on a piston engine at x HP at x rpm with x axle ratio and x tire diameter. This gets thrust at the tires and also a headache
A faster but also very rough method (it ignores friction forces that are being overcome such as drivetrain loss, aerodynamic forces and rolling resistance) is to take the 0-60 time (X in following equation) and convert that to an acceleration (Acceleration (m/s^2) = 60 miles/hour / X seconds *[1609 meter/ 1 mile]*[1 hour / 3600 seconds] ), Force (N) = Thrust = Mass (kg) * Acceleration (m/s^2). A car with an 8 second 0-60 time that weighs 1500 kg is accelerating at 3.35 m/s^2 averaging 5028 N (1130 lbf) thrust.
All the terms in square brackets are equal to 1 so they don't affect the value of the result, but allow various units to cancel out to get everything to SI units as this unit system was designed to do these types of calculations.
Excellent video , Happy holidays and Merry Christmas AgentJayZ !
Well, as Jay said, it comes down to mass-flow. Measuring that on the exhaust of these things is difficult. And, the measurement method will to some extent affect the performance of the engine. For aircraft, knowing the thrust is enough, because the drag of the aircraft can be calculated. For a power turbine, to get some idea of shaft horsepower output, you need to have some idea of mass-flow out of the gas generator...
loved the " go watch cat videos" comment.... cracked me up.
North American A-5 Vigilante. J-79 engines.
If you really want to break someone's brain, we can show that 180 horsepower equals both 600 lbs of thrust and 1,370 lbs of thrust.
My 1964 M20C, powered by a 180 HP Lycoming O-360, has a 500 ft takeoff roll at 2200 lbs gross weight, at sea level on a cold day. This maths out to about 600 lbf thrust.
The Robinson R-22 helicopter idea a nearly identical 180 HP Lycoming HO-360, H being the "helicopter" designation. The R-22 has a Max grid weight of 1,370 lbs, and it can hover at that weight.
So, 180 hp produces either 600 or 1,400 lbf thrust, depending on what spinny things you connect it to.
every helpful information
your r22 is about 5gram per watt. fixedwing is about 2. 2gram per watt
It's all about the propeller efficiency, could you calculate the engine thrust at best rate of climb? Propeller efficiency should be a lot better then
@@jorge8596 ugh. That requires trigonometry... Probably, but not at the moment.
23:50 RR TRENT 1000
GE NX
But I am sure you know this by now
but there is group belief phenomenon where they think it already done like 999 or 911
I’m fine with the “A metric mega-shit-ton” as an answer for turbo jet thrust to horsepower conversion. Just change the HP to KW to keep things simple, even for us Americans.
Hey, I’m having a question that wasn’t talked about just yet, if I’m not mistaking.
It’s especially regarding older Turboshaft engines, with a one shaft design (take the Alouette II with it’s Artouste engine as an example).
Being a one shaft turboshaft must mean they’re unable to start under load just as a piston engine would because spinning the compressor in first place would mean the starter would have to spin the whole Rotor and gearbox assembly, right? So do they have manually engageable clutches like cars? Or does the term „One shaft“ just ignore the shaft and the stage of the working turbine?
I‘m currently an apprentice and my Instructor couldn’t tell me!
Thank you very much in advance and marry Christmas!
Greetings
Louis
PS: I know piston helicopters like the Robinsons R22 and 44 do use a clutch system based on the variable tensionable driving belt’s. Clearly that’s not the case for those Jet-Powered Helicopters like the Alouette.
My suggestions would be:
- A centrifugal clutch (Idk if they’re able to manage those high revs taking into consideration the turbine would do like 30k rev‘s while the rotor is still at 0 when engaging- I guess it would just burn down)
- A hydraulic clutch (with lock-up-clutch - not completely load-free while starting though when the clutch is flooded)
- A normal Disc clutch (But it goes the same as for the centrifugal clutch - huge rev-difference; a lot of heat and wear on that clutch)
Something like a jet engine and a clutch just does not sit right for me - seems like to much effort to avoid designing a second shaft with a dedicated work-turbine!
I do not think those choppers have a clutch. The trick is to start the engine with the main rotor in zero pitch. It therefore presents no load to the engine, only a large amount of inertia, so your batteries better be good.
I would expect that the normal start procedure would require ground power.
As a homework assignment: observe the two types of turboprop starting.
A single shaft like the TPE331 starts with the prop in zero pitch.
A free power turbine engine like the PT6 starts with the prop in max pitch, or even feathered.
And why?
Then we think about what prop setting presents the least load... it depends on whether you are trying to start up, or glide home... eh?
You are correct. I flew Jetstream 41's which had Garrett TPE-331 turboprop engines which are single shaft engines. When you hit the start switch, the ammeter would spike over 1000 amps for a little bit because the electric starter had to turn the entire engine including the compressor section/turbine section/gearbox/propellor to get it up to high enough rpm to light off and sustain combustion without hot starting. Most turbine engine of any size (on aircraft anyway) use starters powered by compressed air (Air turbine starters) as to start them with electric motors/generators would take such a massive motor that packaging it wouldn't make sense and the air starters are much less maintenance intensive and lighter as well. Hope that helps
@@AgentJayZ They do have a sprag clutch that allows the rotor to freewheel faster than the engine if the engine loses power, but for starting, the drive belts that connect the engine to the gearbox that turns the rotors are disengaged. On a robinson, you start the engine, let it warm up adequately, then you flip a red guarded switch which causes the drive pulleys to move further apart and engage the drive belts which happens gradually over like a minute (with lots of screeching from the belts). So in a way, it does have a clutch in that the drive belts slip until the pulleys are in the fully engaged position. Here's a vid with an explanation ruclips.net/video/oig9MA6ZjgA/видео.html
@@AgentJayZ Thank you very much for your response! Also thank you very much, Alan!
The thing about it is, that at startup you can clearly hear the compressor spin up without the gearbox and rotor system spinning just as you would expect it to behave, having a separate power turbine Stage.
Here’s a video of the startup of the engine:
ruclips.net/video/XMP6PrPfof4/видео.html
Reading about the Turbomeca Artouste I noticed that though the shafts were not mentioned, it said that it has two / three turbine stages.
Do they both respective all three of them maybe power the compressor?
Because if that’s unrealistic I think maybe it being described as a „single shaft“ is just a misinformation. The only source, mentioning it being a single shaft engine for me is the handout I received by my German Airforce supervisor. That handout may be incorrect there and it in fact isn’t a single shaft design!
This engine also was used as an APU, also being built by continental named T51.
Unfortunately because the two alouettes we have are out of service not since yesterday the paperwork we have regarding it isn’t the best. I was trying to look it up but unfortunately couldn’t find the information in our records!
Once again thank you for your time and have a great day!
Greetings
Louis
PS: I did. Research regarding the „Astazou“ engine which is based on the „Artouste“ and it was described as a „single shaft“ multiple times. The Astazou was also built in later version’s of the Alouette and it’s successors.
That being said it leaves even more questionmarks making it nearly certain that there must be a clutch indeed in my understand even though it sounds very unrealistic… I’ll try to get more information about that and later on report! Thanks!
Thank you for doing these videos
Hello from Ukraine. Happy New Year. Thanks for your channel. I always look with pleasure. I wish you good health.
Addicting content.
BK below has it. If thrust and gas velocity can be measured no PT or other device reqd. SI units to get P in Watts.
is this a reaction to Greg's Airplanes and Automobiles or just a coincidence that you made video on this topic?
I've seen a few similar titles, but not that one.
How many HP will the Orenda Iroquois make when you have it running?
A new JayZ video in time for Christmas - thank you Santa!
Horsepower and thrust are a way of measuring propulsive force. 1000 pounds of thrust coming from a taxiing jumbo jet engine will be created with a rear nozzle velocity of...300mph. 1000 pounds of thrust coming from a small jet trainer engine at takeoff has a rear nozzle velocity of mach 3 or more. A 500 horsepower piston engine propeller driven stunt plane might produce 3000 pounds of thrust at takeoff and while performing. Take that same engine and put it in a aerodynamically sleak go fast plane and it might reach airspeeds of 400mph+. The 1000lb thrust jet trainer will go 100-200mph faster. Equating thrust to horsepower has more in common with trying to compare apples to oranges7
It's hard to solve an equation with missing variables that substantially change the result. It's people trying to understand with something relatable asking "how much hp that thang got"... I'm going to start purchasing lightbulbs in horsepower from now on. No more 60watt bulbs. You guys have those .08hp bulbs? haha....
I once had a Jetta 5-speed that had a Mach meter instead of a speedometer. Cruising speed was .089
Slightly off the topic of this vid, but sort of relevant.
I've watch pretty much all your vids, and haven't seen one that explains how the thrust produced at the accelerating nozzle is mechanically transmitted to the airframe/mounts.
Love the depth of detail you go into.
... watched ...
Bloody phone!
That must be the one that you missed as he has done that video. In short the engine's thrust moves the engine forward. The engine is bolted to the wings. The wings are bolted to the aircraft, thus the thrust is transferred from to the engine to the aircraft as the gas exhausts through the nozzle.
I've seen said episode/vid.
It's more how the thrust transmits through the structure of the engine from nozzle to mounts.
It strikes me that it's a lot of force applied to some quite thin cross sections.
@@jimarcher3711 - I suppose it seems that way to you. But Aeronautical Engineers are highly skilled at calculating the forces exerted on those parts and designing the parts to withstand those forces, and then some.
Have you not heard Jay refer to "thrust bearings" in some of his videos? Why do you think they have that name?
As a Mechanical Design Engineer of many years, yes it does ....
For instance, I guess you'll be able to tell us what that calculates out at if it were being transmitted via the jet pipe.
The ducting between the gas generator snd power turbine tends to be fairly chunky, but some of that could be put down to long term heat resistance.
I am pretty sure, one can convert thrust to power...
BUT:
The way you measure power and thrust has to be the same on all tests you do to get the calibration curve.
Also the effeciancy of the Thrust-to-Power-Converter (aka the powerturbine/backpressuregenerator/whatever-else-you-are-using) has to be the same on all tests.
To conclude: the Conversionfactor of Thrust-to-Power is dependent on the conversion device in use
Merry Christmas,
LM2500 could be a nice example.
As you know the big guy generates 30000-33000 sHP and 25 MW.
When you tested it, you used a exhaust nozzle so you convert the gas generator to jet engine easily.
when the Lm2500’s Gas generator testing (with exhaust nozzle, no power turbine), we can obtain the thrust. There is no problem but how we can get the Horsepower (ex: 8000 rpm or 9000 rpm) ?
Thanks
We have an old one that has 34,800hp stamped on the data plate.
The newer ones make way more.
@@AgentJayZ When you tested it, you used a exhaust nozzle so you convert the gas generator to jet engine easily.
when the Lm2500’s Gas generator testing (with exhaust nozzle, no power turbine), we can obtain the thrust. There is no problem but how we can get the Horsepower (ex: 8000 rpm or 9000 rpm) ?
I wonder your opinion
@@sevgingokel2707 I'd imagine you could feed the gas output into a turbine and generate electricity, then convert watts to HP.
The exhaust nozzle is choked, meaning it causes an upstream pressure rise, because it is an actual restriction. We don't measure thrust. We measure the pressure rise and use that with the diameter to calculate gas (horse)power.
Efficiency seems to be a big variable . IC engines seem to be rated in terms of BSFC, lbs per hour per HP. The figure is usually between .4 and .5. There must be some equivalent for a turbine engine?
Turboshaft and turboprops are rated in terms of BSFC, same as piston engines (I won't call them ICE as gas turbines are also ICE).
Turbojets/turbofans are rated in TSFC. Replace power with thrust.
The engine should have a thermodynamic power rating. There is some amount of available power from the fuel burnt. But that's theoretical, not practical useful output power.
For example they say that PT-6 has thermodynamically (gas generator) around 300hp more than on the output shaft. Don't quote me on the numbers, but principal should be clear.
The fatal flaw of using global numbers...
Depending on the model of PT6, the net output is somewhere between 550Hp and about 1900 Hp.
The thermal mechanical efficiency of gas turbines is roughly similar to that of piston engines.
About one third of the chemical energy in the fuel is turned into net output.
@@AgentJayZ exactly. When the engine is burning set amount of fuel, it is possible to calculate the amount of energy flowing into the system. J/s ->kW (hp). That would give theoretical max thermodynamic power of the gas generator. Take away all the downstream inefficiencies and we could get some general value. It's impractical, but people would be happy. They would know the horsepower. 😂
It only does seem counter-intuitive that there is no "clear" factor for conversion, because the fact that planes fly faster/higher with more thrust seems to be comparable to fly faster and higher with more horsepower. But it does not really make sense, because both ratings are actually outputs for different uses on different systems. Kinda like with cars where horsepower and torque are linked - but also not. There are tractors with 60 PS that plow through a field as if it was warm butter, but if you try to pull the plow with your 600 PS Supersportscar it won't move a single meter. So what matters is pulling force or speed but both setups are influenced by gearbox, fuel, rpm etc. Most importantly, max torqe and max speed are not at the same rpm.
Similar for Thrust and Horsepower on the Jet engine. The engine is setup to produce max thrust at the mounting point for an airplain, so it can fly efficient. But in a powerplant it is setup for using the least fuel to produce a certain power output. So for flying you want to move a maximum ammount of air at highest possible speed, therefore you accept to make a compromise on how much fuel you burn. If needed you just add extra tanks. In powerplants you have a certain ammount of fuel and you dont need thrust. So you want to extract as much energy from the airflow and put it in the generator. So you want enough air to burn you fuel completely and than get that energy the moving air transports as completly as possible from your turbine.
So thrust or horsepower are different sides of the same medal: Energy. You have a fuel that stores a certain ammount of caloric energy that gets set free in the combustion. That energy causes the rise of pressure and temperature in the gas inside the engine, so it can be transormed into mechanical work.
You can now try to move as much air as possible and create a high ammount of thrust with that energy, therefore you put a turbine in the gas that has low stage count and doesn't hinder the airflow to much so it doesn't lose speed, you just want the system to be self sustaining and increase fuel input to get faster and faster by hotter and hotter air.
On the other hand if you have fix ammount of fuel (it is what ou pay for as powerplant) to fulfill a need of power, you try to get as much energy out of the exaust gas with the turbine, so you don't open bypasses, you slow the gas down in the turbine as much as possible to gain mximum torqe for the input to the generator and you just leave enough torque on the engine shaft to feed itself with enoug air for a clean combustion of the fuel. That also means you dont get thrust ideally, because the mechanical work shall be put to the generator and not into accelaration of air in the exhaust.
So yes, from the physics side you can calculate the ammount of thrust to the ammount of calorimetric enrgy you put in the engine. And you can also calculate an ammount of horsepower for that fuel consumption. So there is a factor between horsepower and thrust and trust and horespower will scale for that engine to that factor if the ammount of oxygen in the air the engine consumes changes for example. But that factor is dependent on the engine tuning in its use-case and cannot be just copied for another engine.
Of course that does not answer the question completely, because you cpuld now make a deepdive how to define "horsepower" of an engine by asking if you talk about mechanical work on compressor/fasn blades or turbine output work or whatever you want to take energy from to measure it...
Missed you! Merry Christmas!
Interesting. However the same engine that produces 7000 pounds of thrust when stationary will produce more when in high speed flight.
Actually, the large bell mouth inlet fairing almost completely removes that effect. That's the reason they are used when testing aircraft engines.
@@AgentJayZ thats interesting, especially considering the effects of the air already being high speed or ram air effect. Neat. Impressive engineering for the test stands for sure.
Actually even more "confusing": if you have the same gas generator with the same fuel and air flow (so it is fair to assume the same horse power) and then build a tubojet and a turbofan with it, the thrust will be very different! I don't know if some manufacturer has ever done this transformation (from turbojet to turbofan or turboprop) but it's a comon theoretical exercise.
Only confusing if you forget that my little conversion talk ONLY works with turbojets. Did I forget to mention that?
As they say, there's nothing new under the sun. Both Metrovick and Whittle did it towards the end of WWII, by adding aft fans to their turbojets.
It's also been done more recently at the model aircraft level. I have seen a Wren turbojet with a free power turbine added to drive a propeller.
how did u learn so much about jhet engines and made one homemade so fast how long did it take ya? will a thermodynamics course help a lot? i only took 1 thermodybnamic course in my life and it was about those adiabatic stuff and control volume control mass and enclosed work-energy area from the specific volumes stuff i forgot but im sure theres more. u keep talking about newtonian mechanics on the particle level, so will classical mechanics help a lot and did ya learn that? what if i wanna learn about rc engines and building just small jet engines i can put on a go kart where do i start??? then what if i wanna move on next to big engines what should i do? ya seem like a smart dude its like u know every nerve and fiber of that big saber engine video, u stripped it down and tested it without exploding into failure and basically knew every part of it and a bit of everything in all engineering departments needed to inspect that engine before safely running it as is likely the standard in the jet engine companies of the real world.
Well, you're biting off enough to fill the lifelong careers of more than a dozen people there.
If you want to put an RC engine in a gokart, do that.
Designing a working engine of any size takes hundreds of engineers working for years, and billions of dollars.
And all that is done using the knowledge gathered through the work of countless scientists over the last 150 years.
Me? I'm an interested amateur when it come to the science and the engineering, and the design.
I'm a technician, so I follow the instructions in the manual written by the people who designed the things.
If you want to learn more about how these engines work, you should watch my playlist called Your Questions Answered. When you get to episode 96, I tell you about some great books. Read those, too.
Then, in order to restore or work on any engine, you are going to need the overhaul manual, and you are going to need to make some specialized tools... or you'll end up wrecking it.
There: if that's not enough info to get you started, then no amount will help.
Good luck with your project!
It's striking how long turbines have been limited mostly by materials science alone - the temperatures at which things melt or lose strength. The mechanical engineering is so optimized.
It's said the Pratt & Whitney F135 approaches 2,000°C (when all the coatings are in good condition). Is that going to be the end unless new materials are discovered?
almost everything is limited by materials science.
The only other possibility is to use very clever fluid mechanics to maintain a layer of colder gas on the turbine surfaces, while hotter gas can still pass by them and transfer momentum to them. With the high speeds and high turbulence involved in jets, I suspect even a lab demonstration of this working in a stable way would be very impressive. As fluid flow simulations continue to get better in terms of computing power and result accuracy, there is still a chance something might be found.
There's also a chance that a completely different way of making an engine will be invented that can rewrite the rules. When you think that steam turbines driving pistons with steam pressure was the 'obvious' way to do things that couldn't be improved on before the Parson's turbine and that Whittle only get the go-ahead to develop his jet engine designs because the UK government heard the German's were interested in it - the powers that be in aviation didn't see much value in the idea in the time of piston engined planes, there's always a chance of a completely new paradigm showing up.
@@peglor Using a cold gas layer to shield turbines from hot temperatures has been done for decades. It's not some fancy concept only seen in a lab - most modern engines utilize it. It's called film cooling - "cold" air (cold being relative here) is routed from the compressor and blown through cooling holes in the turbine blades/vanes surfaces and through the trailing edge, in such a way that the airfoil is "coated" in a cold air film to greatly reduce the heat flux into the airfoil. In many modern engines the first stage turbine is operating at temperatures above the melting point of the metal, and this film cooling prevents it from melting/failing.
@@ASJC27 I was aware of this being used in some situations, but as it is currently implemented, jet performance is already on the thermal limit, so a better way of doing it is needed. Building a cool boundary layer at the leading edge is too obvious not to have been already tried, so I suspect it reduces performance.
If you used ethanol instead of kerosene in a gas turbine, would the fuel control manage to inject twice the volume of fuel? Does it have that kind of overcapacity built in without having to modify anything?
Yes. The difference in emissions might make the increased cost worthwhile in some installations.
The power output would not change, because the engine is limited by turbine inlet temperature. However much fuel, of whatever type, will be sprayed in by the fuel control until that temp is achieved.
@@AgentJayZ Cool! Then if I can ever afford a jetbike I can fuel it up with E85 and be almost eco friendly 🙂
My humble thoughts... Horsepower is a unit of power. Pounds of thrust is a unit of force. You simply can't convert those units. It would be like trying to convert a unit of length to a unit of temperature. Or am I misunderstanding what is meant by "pounds of thrust" in the gas turbine world? Is this similar to the relationship between torque and horsepower in an automotive engine? They both say a lot about what the engine "can do" but they represent two different things.
Interestingly enough I ran the conversion calculations for your two examples and got 1.3 hp per lb thrust for both examples... coincidence? (7MW = 7,280 lb thrust. 15,000hp = 11,500lb thrust).
My point of the vid is that there is no real equation, but it's a point of interest.
We compared the actual measurements, and that's as far as I go.
@@AgentJayZ Let's say jet fuel has an average energy density of ~45MJ/kg (~20,000BTU/lb) and a density of ~800kg/m³ (~7lb/gal), if the 777 engine burns ~7ton/hr in flight (~3.5ton/hr per engine; ~7,000lb/hr; very economical), then a nominal Pegasus horsepower [php] (we should register that) can be calculated as 45MJ/kg x 3.5ton/hr = ~55,000php. That would be the nominal horsepower if the engine is 100% efficient and the energy source only comes from the fuel. For the J79, a fuel consumption of ~17ton/hr (~90gal/min x ~7lb/gal; thirsty bastard) with afterburners translates to ~300,000php and ~130,000php without afterburners (~40gal/min). For the F-18, 36,000lb/hr per engine on afterburners translates to ~285,000hp. For the efficient SR-71 Blackbird, ~22,000lb/hr per engine translates to ~175,000php with afterburners. For a car engine, 30mi/gal at 50mph (50mph / 30mi/gal x 7lb/gal x 20kBTU/lb) = ~90php.
php is horse power, but by Pegasus?
Isn't that a horse that can fly?
My math doesn't use flying horses...
Nevertheless - interesting!
safe to say a pile of power however you measure
W=T*V, V for speed so you can only has full power in ISO and sea lever; the idea of think a airplane engine and industry gas turbo was okay but if you has different fuel control it may off set.
Yo big jay. How many different fuels will your turbines run on? Not the black bird or new equipment. Just what you work on. I’m able to use kerosene, jet1A,or diesel fuel in the small jetcat engines. Just was wondering.
Gasoline is a specified alternate, but it's hard on the fuel pumps. Octane rating does not matter.
A much better alternate is home heating oil. It is very close to diesel, and of course it's less expensive because it is not taxed like road vehicle fuel.
We have run Afterburning J79s on the stuff, and it works without any problems.
@@AgentJayZ If you can source it, the railroad and maritime shipping industry in the US use a red diesel (#1) that is not taxed as highway fuel.
Wow. So both engines actually produced a ratio of 1. (1lbt was roughly equivalent to 1kW)
7280 lbt engine produced 7MW or 7000 kW.
11500 lbt engine produced 15000hp which is 11194 kW.
regarding the discussion about the equivalent power to thrust ratio, and how the book mentions 2:1
I'm assuming that even when operating the engine with an output shaft, it still produces "some" thrust with the exhaust gasses? So maybe this thrust could equate to some equivalent power that cannot be converted to mechanical work at the output shaft. Could the book be taking that into account to measure the equivalence? As in, it produces X ammount of power but only Y% of that thrust can be harvested at the output shaft? And the other (100-Y)% is still converted to work in accelerating air mass?
If that makes sense.
A turboprop certainly produces some residual thrust from its exhaust. The Bristol Proteus engine of the 1950s was rated at 4,250SHP going to the prop at its take-off rating, plus around 1,000lb of thrust.
@@grahamj9101 that is certainly significant
It's impossible for all the energy added to the gas flowing through the engine to be completely converted to mechanical work at an output shaft. If you think about what 100% conversion would mean, it would result in the exhaust gas exiting with the same energy as it entered the engine, so at room temperature and pressure and with zero velocity. The problem with zero velocity air is that then there's no way to move it out of the way of the new air flowing into the engine, so the engine will stop dead. There are clever theoretical ways of getting around this by having the air exit at lower than ambient temperature or pressure so there's energy left over to give it a non-zero velocity so new flow can enter the engine, but this isn't practical in any real world setup I'm aware of.
Engine designs like the Atkinson cycle engine are an attempt to get close to the ideal maximum work extraction by setting up a piston engine so it has different expansion and compression ratios. A version of this is implemented in most hybrid cars by leaving the inlet valve open for part of the compression stroke, so it flows back out the inlet for part of the compression cycle. This means less gas is compressed than the cylinder could normally compress, but after combustion this smaller amount of gas is expanded to the full extent the piston allows it to. This means more combustion pressure is turned into work pushing the piston down. The downside of this is that an identical engine will make less power per kg on the Atkinson cycle compared to the normal 4 stroke Otto cycle, though it will have better mpg, even when the lower max power figure is accounted for.
@@peglor That was an awesome write-up and thank you for taking the time.
I just want to point out, and I'm mentioning to perhaps steer the conversation a bit:
I am aware of these concepts and they are off-course totally correct and valid. What I was trying to discuss is not the general aspect of power efficiency in regards to fuel caloric intake but more specifically this:
The video does some practical measuring to come up with a practical ratio of mechanical power to thrust output figures of 1:1 on practical applications for each scenario, whereas the book mentions that the ratio is 2:1.
And I'm wondering if this discrepancy is due to the book mentioning not a practical comparison, i.e. "an engine that practically outputs 1000lbs of thrust when set up as a jet aircraft engine will produce 1000hp of mechanical work when setup to drive a mechanical shaft", which is a statement that already takes into account the different conversion efficiencies of producing mechanical work on the shaft or thrust, or if it is referring to a comparison of the relative output figures, i.e.: "an engine set up as a shaft output engine will produce twice as many horsepower as it will produce pounds of thrust (simultaneously)"
Now, taking into account grahams comment above this last ratio would more likely seem to be 4:1 so that would also contradict the figure. So that's probably not what it's referring to either.
So I'm mostly trying to figure out if interpreting the figure the book is mentioning will explain somewhat why the discrepancy between those ratios is so significant.
@@stathisbikos6563 I think part of the issue is that a lot of the energy in jet exhaust is heat, so while the momentum and pressure can be captured and turned to mechanical motion, the heat is much harder to capture (Some can be captured by the behaviour described by the PV = mRT gas equation where reducing the pressure will reduce the temperature, but it would take a lot of expansion to do this and the bigger the expansion space the more heat will be lost through the outer walls, so the less worthwhile the expansion is).
Using jet engines as combined heat and power setups rather than just for generating mechanical power can get figures over 90% efficiency in some cases, so a more equal thrust to power comparison might be to look at thrust vs. the sum of mechanical power and heat from a CHP system using the same engine.
At what point internally does the engine go from huff to puff? At the combustion chamber? GE made...made good lightbulbs.
can you define "huff" and "puff"? It is a moving flow of air, with speeds, pressures, and temperatures changing along the way
I realize I'm being pedantic here but are the fuel atomizers different between ones that accept aircraft grade kerosene and natural gas / propane? It seems with the LM1500s your shown tested, some of the plumbing looks a bit different.
No, I don’t think you’re being at all pedantic. It’s a very fair question from someone who isn’t familiar with the technology.
For the same heat release rate in the combustor and the same power output, the volumetric fuel flow of gas will be much greater than for a liquid fuel, and the burners can look very different.
I was familiar with the gas and dual fuel burners for the Industrial Olympus and responsible for the design of the gas and dual fuel burners for the Industrial RB211 - but it’s all a long time ago now.
My recollection is that we did manage to use the same basic external profile of the RB211 aero burner feed arm for the gas burner, but had to increase the internal passage size. The 'airspray' head of the liquid burner was completely replaced by a simple ‘pepper pot’ injector, with a ring of holes.
For the dual fuel burner, it was a case of trying to get a quart into a pint pot. I had to devise a completely new two-piece casting for the feed arm, with a ‘fatter’ external profile, which could be retrofitted into the existing engine. The assembly was brazed together, with two tubes passing through the gas passage to carry the liquid (diesel) fuel.
And perhaps I should explain the term ‘dual fuel’. It means that the engine can change over from liquid to gas, and vice -versa, while running under power, and can even run on a mixture of the two.
You’ve noticed the different external ‘plumbing’ on a gas-fuelled engine. Again, that's down to the significantly greater volumetric fuel flow - and, of course, a dual fuel engine has to have both liquid and gas manifolds.
As mentioned in the video, and in the description, my Fuel Nozzles series of videos shows the difference between liquid and gaseous fuel nozzles for the LM1500/J79.
@@AgentJayZ Thanks! Sorry, I did actually watch that video some time back and did not remember when I commented. I've always wondered if the engines would pass the 'tequila test' like the Chrysler turbine car engine allegedly could, but it would take an awful lot of tequila to run an LM1500. Also, I'd probably rather keep it for myself than see it burned 😝
@@grahamj9101 Absolutely fascinating! Thank you! I had figured 'dual fuel' would probably mean an overhaul where the atomizers were changed, but the fact that you designed some that could do both is fascinating. I suppose I realized it was thermodynamically possible (a gas turbine engine combustor is just a heater at heart) but not practical to build.
Are dual fuel nozzles standard or is that a specialty type need? Also, are there any appreciable differences between Diesel and kerosene?
@@KronosIV A duel fuel system wasn't standard, but was a special order option for a customer - and there were quite a few such installations. Dual fuel nozzles were only fitted on gas generators for dual fuel installations and, as I recall, the gas generators had a specific designation. It meant having two completely different fuel systems, of course, with a control system that managed both for fuelling proportionality during a changeover.
While a burner designed originally for kerosene could handle diesel equally well, there could be problems with 'coking', ie, soft carbon build up on the burner and in the combustion chamber head. For the same heat release, the combustion chamber walls ran hotter, because of the more luminous flame when burning diesel. Also, the exhaust could be rather smokier, particularly at lower powers.
I recall being in Portsmouth Harbour on a sailing trip years ago, opposite the Royal Navy's base there. A Type 42 destroyer (with two Marine Olympus, two Marine Tynes) started its engines, resulting in clouds of white smoke and the inevitable stink of unburnt diesel.
HP is about the same as kinetic energy of exhaust gas per second at engine exhaust nozzle?
Another question, why the by pass route of big turbo fan engine is not streamlined (pipes etc disturbing the flow)?
Modern turbofan engines have a cover over the core, so the bypass duct is more streamlined. Every extra part costs money, and selling engines to aircraft manufacturers is an extremely competitive business.
The bypass annulus of the early low bypass engines was often not well faired (ie, ‘streamlined’). However, the bypass annulus of the modern high bypass engines is invariably well faired. Take a look elsewhere on RUclips for videos of engines with their cowlings open.
There's a good clip of a LEAP engine with its cowlings open and you will see that the rear cowlings form the inner and outer walls of the bypass duct.
PS It occurs to me that you have been misled by the fact that, when the cowlings are open you see all the 'plumbing'. However, take a look at the video I've suggested and you will realise that the pipework is covered by the inner wall of the rear cowling. And all the pipework, etc, that you see beneath the front cowling is on the outside of the fan case.
Top!
Um Mestre!
haven't watched one of your video for a while
got AJZ withdrawal I think, missed your jet education
What ever happened to the Turbo Jet Boat?
Progressing at the speed of an after-hours project.
@@AgentJayZ thanks for the reply, great to hear that's it's still happening at least, that looked like an interesting little project.
got a question, tried to find it mentioned before but can not find it so here we go : If you got a gearbox connected to the N1-shaft and it brakes and stops the N1 fan completely .. is it likely that the N2 continues to run .. ( although with somewhat disturbed airflow from the front ?
If a geared turbofan has a failure inside and stops turning, that might cause the N1 system to stop, but this is extremely unlikely.
If the input shaft to the gearbox fails, then the N1 system will have insufficient load, and may overspeed, but this is extremely unlikely.
The N2 system in your hypothetical engine could continue running, but since the N1 system makes most of the thrust the whole thing would be quite ineffective.
If anything like what you describe happened, there would be alarms going off, and the pilot would shut down the engine, if it didn't already shut itself off.
I think modern FADEC systems are looking for this and many other problems about a hundred times every second.
I am going to be pedantic (as I am so often) and object to the use of N1 and N2 to refer to the spools of an engine. Those terms should be used for the rotational speeds of the spools, not to define the spools.
@@AgentJayZ thank you for the answer! Absolutely makes sense , and yes in 99.99% of the cases the engine would have been shut down straight away manually when detected. I understand it is a very unlikely case, I was assuming that the stopped N1 Fan and the stopped turbine would cause to much issues with the airflow for the N2 to even continue to run. But I guess it could continue to run slowly by itself without it´s N1 friend :)
@@grahamj9101 no problem for me lets call it high and low pressure spools instead then
Your imaginary thought experiment could only take place without the fuel control and all of it's sensors.
Such a case would never happen. Who would attempt to start and run an engine without the fuel control installed and working properly?
Thought experiments are fine for break time banter, but that's all.
It amazes me that pistons were popular first...
Steam engines were magic at first, but then they made sense to the practcal observer.
Jets seem to be in the magic phase, still.
Would it make any sense to use radioactive isotopes of air molecules to directly observe turbulences inside the engine and use that data to find out a way to reduce Reynolds number right to zero ? And had you ever heard about exoskeletal turbojet engines ?
No.
Not possible.
No.
The flow inside a jet engine, or around anything in motion through a fluid, can now be modelled to a high degree of accuracy using Computational Fluid Dynamics (CFD). It's been around and in use for many years now. Messing about with air seeded with radioactivity would be utterly foolhardy.
There is no way that Reynolds Number can be reduced to zero, except by reducing the flow velocity to zero. Any fluid that is in motion can have a Reynolds Number ascribed to it, relative to what it is flowing through or around.
As someone who had a career lifetime in the design of gas turbine engines, I really don't understand the use of the term "exoskeletal" in relation to a jet engine, turbojet or otherwise.
@@grahamj9101 It seems to refer to a jet engine that has the bearings for the compressor/turbine blades on the outside a drum holding the blades instead of inside. In theory the advantage is the blades are now in compression not tension so you can use ceramics but making bearings that work at the velocities and dimensions required isn't solved yet. (No actual opinions on it, just got curious and googled them)
@@hannahranga To make rolling element bearings the diameter of the outside of a compressor casing, while rotating at the same speed as the existing bearings, would probably need an aerospace grade of Unobtanium.
The nearer term solution will most probably be the utilisation of composite materials, so that blings (integrally bladed rings) eventually replace the blisks (integrally bladed discs) that are currently in increasingly common use.
@@grahamj9101 had a feeling that might have been the case.
Question it would be cool to hear you answer: what is the effect of heavy rain on a turbojet or turbofan in flight? I heard somewhere it improves performance due to the increased mass transfer. But it must at some point become a detriment and eventually stop the engine.
Rain is insignificant, no matter how much. A modern turbofan can not be stopped by a dozen 3 inch fire hoses aimed directly into the inlet.
Have a look at water ingestion testing.
These engines are amazing.
@@AgentJayZ interesting, thank you!
There is actually an example of fire crews stopping an engine with their hoses - but it does go to prove how difficult it is to stop a big turbofan with water.
Check out the Qantas QF32 engine failure in 2010. It's been discussed on this channel more than once, so I won't go into the failure of the No.2 engine. However, it severed the controls to the No.1 engine, which ran for about 3-1/2 hours after the emergency landing. The engine, having been doused with water and foam for much of that time, finally flamed out, after being flooded with massive amounts of foam.
My suspicion is that the combustion process wasn't simply overwhelmed by the sheer volume of water and foam, but that the compressor aerodynamics were progressively degraded by ingestion of the foam, contributing to the flameout.
@@AgentJayZ maybe im splitting hairs here, but theoretically wouldn't it boost power if only by a tiny percent since water going from liquid to gas takes away heat from the air making it cooler making it more dense = the engine making more power? Edit: you're 3000 times better than my teachers in module 15 in a certified 147 school
a: any natural rain is insignificant in terms of hurting the engine, and also in terms of helping the engine.
Yes, theoretically it helps increase mass flow though the engine, and it reduces combustion temp... just like theoretically I am lighter at the top of my stairs because I am farther from the Earth.
To boost power in a large airliner turbofan, you need gallons of water per second, going through the fuel burning core. So not enough, but also, turbofans eject anything heavier than air to the outside of the airflow path, which is the bypass duct, so not into the core.
Off topic: Does anyone have extensive experience with the engine used in the U.S. B57? I was in the Cal ANG when we had a B57 come by TDY for a few weeks. I swear, every post flight, I poured in 3-4 quarts of lube oil. What was annoying was that the filler was in a gawdawful position and it always looked full. I was told to keep pouring until it overflowed. Comments please?
A one second search of Goog, starting with this: Martin B-57 Canberra. Yes, we have tested those engines. I have posted a video of the run.
They have a very strange oil system.
The rear main bearing is lubed by a total loss system, at a rate of about one drop per second, with the oil dumped into the exhaust stream.
It says in the manual that it takes oil about 20 minutes to make it from the reservoir to the rear bearing.
There's no way to look in there, so you have to have faith that oil is flowing/dripping. If it isn't, then in about 5 minutes the bearing will fail.
I'll bet there was a maintenance decision that it's better to overfill the reservoir than to have even the slightest chance of going dry... using oil at 3600 drops per hour...
@@AgentJayZ No wonder.
@ 20:10
ruclips.net/video/WGA2zoXmR2w/видео.html
Watts = PIE.
Power = Amps x Volts
I know most electrica RC plane motor with propeller give about 4 gram per watt. which is 2 times more efficient
@AgentJayZ, John from Australia here. I see it like this, in a thrust rated engine it takes X Horsepower to create X thrust. My reasoning is this: to spin the compressor at full thrust it takes HP, lots of HP. With a big fan on the front, you'd have to add to power turbine output. In an engine rated for shaft HP, it's rather obvious. Unless there is a shaft output creating rotating torque, you'd have to use Horse-Farts as there is no torque. No rotating torque, NO POWER! You could just convert the BTU output to HP, but not really useful.
This topic has long been argued about, including several times on this channel.
I have a copy of a book (I think AgentJayZ also has a copy) on the subject of jet engines, written by a well-respected author. In it he states that a jet engine, running at maximum thrust with the aircraft stationary at the end of the runway, is producing no power (or words to that effect).
However, I fundamentally disagree. The engine might not be producing any useful power in accelerating the aircraft. It is, nevertheless, producing a massive amount of power in accelerating a massive amount of hot air, which can be calculated and turned into a horsepower figure.
I haven’t seen the term used for some time but, years ago, R-R used to quote an equivalent gas horsepower (EGHP) figure for its industrial gas generators. This was effectively a measure of the power potentially available in the gas efflux from the exhaust unit, for which a horsepower figure was obviously calculated or inferred.
In the past, I’ve made the point that I/C engine manufacturers will quote maximum power figures for their engines taken from dynamometer testing, where the engines are doing no more than producing heat by heating water or generating electricity that is being turned into heat. So why is a power figure for a stationary I/C engine on a dynamometer any more valid than an equivalent power figure for a jet engine on test?
@@grahamj9101 It's all depends on whether you're measuring its power as a device for imparting kinetic energy to the airplane, or its power as an open-air space heater.
@@MatthijsvanDuin You’re being a bit of a smart****. I’ll go along with my knowledge and experience of a career lifetime in the design of gas turbine engines, industrial, marine and aero.
Jay, Merry Christmas and thanks for another year of turbine nerd content.
I saw this photo of an French aerotrain with a wild exhaust nozzle; can you tell me why it's shaped like this? It looks jet-ish in the front and a lot like my propane grill in the back.
ruclips.net/video/ND3MegqYQFA/видео.html
Very interesting. That nozzle on the back of Train 2 looks like a combination of 60s era hush kit nozzles meant to reduce noise, and the back end of the F-117, intended to reduce the heat signature of the exhaust.
I love all the old, weird stuff.
Technology does not have enough weird nowadays...
Think monorail. The defusion nozzles at the rear of the vehicle is, as I recall from popular mechanics, aerodynamic only. All the propulsion is provided by the jet engine mounted on the strut structure overhead.
I'm curious: do you guys have any access to a J79-GE-J1E, or are those more rare these days?
More rare than when? Those don't go into the F-4.
I have posted many videos of test runs of them.
What do you mean by access?
To see?
To touch?
To buy?
A championship level player in the league of Vague!
@@AgentJayZ to experience :P
I think your math is wrong brother, 15,000 hp is 11.19 Megawatt, so follows the same rough 1:1 relationship between MW and Thrust. Great vid, nice to think through this stuff.
I always thought Turbines had direct relationship to HP, turning shaft has torque and RPM....may be tough to measure, but theoretically it's calculatable and measurable.
I'd guess the newer engines do a much better job of turning rotational power into thrust (efficiency), so thrust measurements to hp correlation is likely very different between eras..
As I've suggested in another comment, there is a potential problem in that, for an aero engine (turbojet, turbofan, or whatever), the take-off thrust is usually the most commonly quoted rating, with publicity in mind.
In contrast the maximum power (aka peak) rating for the equivalent industrial gas generator (whether quoted in SHP or MW) is normally a derating relative to the T/O thrust, as it may be used for hours rather minutes. Consequently, there may not be a consistent relationship between the two from one manufacturer or engine type to another.
For applications such as gas pumping, there is a usually so-called base load rating, which is a further substantial derating, with gas generators running tens of thousands of hours between overhauls.
HP is work done over time
You can produce infinite amounts of thrust but if no movement no work is done that’s why to convert thrust to HP it needs to be at speed and see level
Ahem... I have an announcement to make: The air is moving, being accelerated from zero to over one thousand km per hour.
Accelerating a mass, takes force. Force times distance equals energy. Force times distance divided by time is the actual definition of power.
Work is being done by a stationary jet engine, because it is moving air.
If you can not understand that, you are an infant.
Over...
Thank you!
Come again!
It is still producing power, just in a different way: the engine is not moving, all the power is going into the air, ultimately heating it up through friction with other air molecules. So the power is just all going into heat
I agree with AgentJayZ.
However, please take a look at what I describe as my "party piece" comment somewhere below. I quote an effective horsepower figure of around 130,000 for Concorde in supersonic cruise. I recall that, years ago at R-R Bristol, on occasions I had to assist in dealing with letters and enquiries from the general public. There was one individual who just would not believe that 130,000 HP figure, insisting on comparing it with the power quoted for the massive steam turbines of the ocean liners of the day.
GE and ABB gas turbines
787 uses a RR Trent
Or GE GENx-1B.
@@qcan8468 you are correct my friend I had forgotten about that.
yes 1 watt is 1 volt ampere .. ... or in laymans terms 1 volt at 1 amp is 1 watt ... also all the other maths like 0.5 volts at 2 amps is still 1 watt etc ..
wouldnt a change in fuel require a potential change in the combustion chamber ... sure some fuels will still self regulate to stable in the same or smaller chamber BUT some may take longer and need a slightly longer chamber to work optimally ..
.
from all I have read and seen it seems that how fast the flame burns or slow determines the size of your combustion chamber ... and lower octane fuel needs a bit more space while higher octane needs less .. to do the same job .. the part I am not sure about is how much of a difference the different fuel octanes or types change that size ... lets same old leaded pump gas might need an 8inch chamber while 97 octane no lead may need only 6 inches ... and jp4 may need 6.5 inches etc ...
It'll burn any hydrocarbon liquid fuel with no difficulties. What does that mean?
Alcohol, gasoline of any octane rating, diesel, home heating oil, straight kerosene, or actual jet fuel are all just fine, with an adjustment on the fuel control (one dial) for specific gravity.
The engine sense EGT, and controls fuel delivery to reach a set Temp.
Most of the parts in a J-79 are steel. This it could have been lighter with the exotic metals.
Nope. All iron based metals have the same density. And no other than iron based metals are suitable for jet engine. Aluminum is already used on J-79 parts where it could be used.
Some of the compressor disks are made of titanium alloy. It was a fairly new material then. Modern fighter engines use a lot more of it. For example the LP compressor cases of the GE F404 are titanium instead of steel.
The extensive use of steel in the J79 gave GE an advantage in turning the engine into an industrial gas generator. In comparison, the Olympus 200 series engine, as used in the Vulcan bomber, had an aluminium (not 'aloo-min-um') LP compressor. To make the engine robust enough to become an industrial gas generator, the LP compressor was redesigned in steel, whilst retaining the same aerodynamics.
@@janphilipp86 Generally if you're making something out a stronger exotic alloy/mixture you design the part to use less material so it's lighter.
Totally forget titanium, but I didn’t know it was fairly knew when the J-79 was developed.
If a stationary jet engine produces no propulsive horsepower, then how the hell does the plane start rolling. Point blank, it does work. Just like a floor does work to push back against my feet.