Incredible how heavy some of these older turbine blades seem to be - they must be pulling like crazy on the shaft at high RPMs. Anyway - thanks for showing all these, amazing stuff. Would be fun to see how they manufacture the blades and get those tiny holes in there.
As I watch this mams videos. I realize his education is way beyond an average gas turbine engine mechanic. He has a very good understanding of very complex concepts in design and heat transfer technologies and metallurgy. Metallurgy is a subject that is more difficult than a nuclear physicist. Metallurgy is so complex that many will specialize in a group of metals such as non ferrous, ferrous, Titanium and it's alloys, Grasses and bronze, etc... I used to teach Metallurgy and am impressed with his knowledge of so many of these areas of expertise. I also was a welding engineer who built gast tibine engine hot zone components, mostly combustion cans. Someday I want to visit his shop and learn more in person. My last bucket list thing to do while alive. May visit after I pass...😅
At prima machine training the past few weeks. I manufacture and produce these parts. I love your videos. I make replacement parts for most of what you show.
Investment casting was revived and refined to make the complex internals of blades. It was state of the art in the 1970's when I studied it formally as part of Materials Science, Thermodynamics and Fluid Mechanics. There were of course gaping chasm of untold wisdom. Which is why I'm watching this channel.
I'm not a turbine engine engineer, but I have some training in heat exchanger design. The objective here is to maximize the heat transfer to the cooling air while minimizing the mass flow rate of the cooling air, since this is what costs compressor power and therefore fuel consumption. Yes, the Series flow path potentially increases the max temperature of the cooling air in the blade, but this also means that the cooling air has absorbed more heat per mass. Sure, you could just restrict the outlet of air, but then the air is moving very slowly inside the blade, which reduces the heat transfer coefficient. And then you also have a thermal gradient within the air in the blade that results in the air at the tips being hotter, whereas with the series path, the temperatuee gradient of the air in the blade will somewhat average out radially. This temperature gradient will also be present in the air exiting the film cooling holes. The series path will have more pressure drop, but you likely have more differential pressure than you need for the convective cooling path because the exit pressure is somewhere between the stage inlit and stage outlet pressures, whereas the film cooling exit pressure is the turbine inlet pressure.
Out of curiosity; if you were to compare the area of the inlet section to the area of the outlets combined, do you generally keep those areas as close to the same as possible?
Another good question which i have never thought about. I would think the rate of flow would be metered by outlet area, but that would only be a guess. I really don't know where to turn for a definitive answer. It's such a specialized niche question. But, maybe Graham knows. He designed turbine engines for his whole career.
@@SirSpence99 That's probably actually quite a complicated question. If you want the pressure inside the blade to be as high as possible, you'd have the inlet wide open and control total flow by manipulating the outlets. You also have to keep in mind that the flow out of each outlet will depend on the size, shape, pressure inside the blade at the outlet, Pressure outside the blade at the outlet, and cooling air temperature at the outlet. I don't know that there's a strong reason to control the bulk pressure of the air inside the blade, so that will probably be secondary after optimizing the distribution of mass in the blade, since mass at the outside increases load on the entire blade, whereas mass at the root can help support the blade structurally. Moving metal around also affects manufacturability, steady state and transient thermal performance, vibration modes, etc. So there's at least five domains for optimization: External flow, internal flow, thermal, structural, and manufacturing. That goes a lot towards explaining why these engines and especially their development are so expensive.
If you don't know, like I don't know, why spend three times as many words saying you don't know? You seem like a nice guy, trying to help, but guesses are usually treated as chaff. Carry on, as if normal.
@@AgentJayZ The rule of thumb I follow when designing ducts for my 3d printer is that I maintain the same cross-sectional area unless I want to increase velocity and I also make sure I never increase area and then decrease it. According to my understanding of physics, (from looking into rocket nozzles, though that is rather different) decreasing area increases velocity while decreasing effective pressure given an unchanging source. Given that "high static pressure" fans basically don't exist and that fans of all kinds lose flow rate as the required pressure increases, I try not to decrease the area of my ducts unless I have to. What I'm mostly curious on is which part (if any) I'm wrong on. Considering I'm doing cooling much like the vents on the leading edge in your examples are doing, this is something that would actually be quite helpful for me to know. (I'm currently designing 3d printer cooling ducts so they need to vent air out a bit of a distance to cool the part.) I suppose that means my question is two-fold, one, does changing the area after some distance in a duct decrease flow-rate and do you want higher velocity or higher flow-rate for cooling.
Great video as always! Some pertinent terms you could throw into this conversation (to help tie together everything you're talking about) are 'surface area', 'choked flow', 'dwell time', and 'gas density'. Yes, lots of fluid dynamics and thermodynamics math over both our heads (and I'm even in the mass flow measurement business!). In short, we're trying to pass a low molecular weight gas over a much higher molecular weight metal to draw (lots of) heat energy away. Or at least enough to maintain a nice safety margin on the metalurgical temp limits. Some 30+ years ago I met a guy (working as a car mechanic in Tucson AZ ironically) who apparently revolutionized the manufacturer of these cooled turbine blades; specifically for private jet sized engines. Interesting fellow, not sure what he was doing working on my Honda with that kind of resume! Anyway, it was great to finally see a breakdown (literally!) on what theses blades are all about. Thanks again for making these videos.
What baffles me when I look at the engineering of these turbine engines is how the designers and engineers manage the complexitiy within their process. When I am doing my little tinkering projects as a hobbyist I always try to keep it as simple and functional as possible. But a solution to an upcoming design problem often leads to a feature that comes with its own challenges, requirements and issues. And this spiral of fixes and more issues can grow really fast. I do not even dare to think of the level of complexity when designing rocket or gas turbine engines. Keeping it simple yet efficient and effective is really an art form.
When I worked at a combined cycle plant, we had rotor cooling air. Bleed air was passed through a water to air heat exchanger (aka kettle boiler). This cooled the air and added some heat to the feed water for the steamer setup. Siemens SGT5000F
In a reciprocating engine, the boundary layer usually does a good job at insulating the metal bits from peak combustion temperatures. Undet knock however, supersonic waves scour the boundary layer from the surface often resulting in holes burnt through piston tops. A gas turbine situation is a little different mainly because there's no respite from heat so sustaining a cooler boundary layer requires some "help" in the form of air bleeds.
The pressure in the combustion chamber can not exceed the pressure in the compressor. The pressure is assumed as constant ideally. However it drops a little.
It's still amazing to me that those early gas turbine engines, and even piston engines, were designed and built by extremely smart people with nothing but pencil, paper, slide rules, and a vision of what they wanted to achieve. No computers or AI modeling, just ingenuity.
The HPT blades on the Rolls-Royce Trent 1000 TEN have a life of 1000 cycles (flights) mandated by EASA (if they last that long before cracking due to creep) and cost around $25,000 USD each
Rolls has been GROWING titanium single crystal blades for their "Trent" series ... with internal passages and surface holes somehow grown in place. The process is proprietary and secret.
Single crystal turbine blades are by no means new: R-R was casting them for both civil and military engines well before I took early retirement twenty years ago. Essentially, they are cast, using the 'lost wax' process. The single crystal is then 'grown' by slowly withdrawing the ceramic mould from the furnace, so that the blade progressively cools and solidifies from root to tip. This much is not secret: more details can be found on the internet. However, I have to tell you that HP turbine blades are not cast in titanium: it's not a turbine blade material. Think in terms of high-temperature-resistant nickel-cobalt alloys, such as MAR-M 002.
Turbine blades are not made of any type of titanium alloy. Ti is soft, weak, and prone to melting or even catching fire in combustion gases. Ti is stronger, harder, heavier, and more temperature resistant then aluminum, but compared to Refractory alloys of nickel and iron, Ti is weaker, softer, lighter, and less temperature resistant. Turbine blades made from Wensleydale cheese, and even balsa wood, are just as good as those made of titanium.
@@AgentJayZ Titanium can catch fire in a compressor, where the air pressure and temperature is high enough. There is something known as the 'titanium fire line', downstream of which, if there is (eg) a heavy tip rub, then a fire may be initiated. If this occurs, all the titanium aerofoils (and possibly the discs) will be consumed. The fire may be so intense as to burn through the engine casings and the airframe structure. I am aware that such an event happened somewhere over Canada, some years ago, to a twin-engined fighter, which was not of Canadian or US origin. The wingman who observed the event said it was the brightest white light that he'd ever seen. The second engine continued to run, keeping the aircraft in the air, but its electrical control connections had been destroyed, and possibly some of the aircraft's flight controls too. There was no chance of getting the aircraft down to a safe landing, so the two crew used their ejection seats, and the final result was a smoking hole somewhere in the Canadian wilderness.
@@AgentJayZ I approve of your choice of cheese. Unfortunately, the UK has called off trade agreement talks with Canada, and a whopping increase in tariff will be imposed on British cheese imports.
We all know that Canadians make really good cheese. We also know that we use recipes from other places. Canadian cheddar is darn good. I think many of us don't realize that it's named after a place, that makes the real thing. It is more expensive, and to regular folks like me, that's a shame.
G'day Jay, Yay Team ! A beautiful Explainification ; I enjoyed every bit Of it... Thankyou. As regards your Parting Question, "Who makes Cars with Wooden Spoked Wheels today (?)... Nobody !" Well, um, probably because I posted a Video showing two of my grandfather's Wheelwrighting Tools which I'd cleaned and oiled-up for their first use in 25 years (and then, I was using them for the first time since 1936 when my grandfather last made a Wagon Wheel Spoke with them)... ; The mighty RUclips Algae-Rythm has been feeding me with back-catelogue Uploads from @ Engels Coach Workshop Channel... Whereas I use the 1905 Patent Tools on my grandfather's Brace & Bit, Dave Engel has a pair of Drill-Presses, one with a Spoke-Pointer and the other with a Spoke-Tennon Cutter... He scratch-built Full Size Replicas of the 3 Wagons in the Death Valley Borax Wagon-Train - which used to operate from 1892 till 1896 or something....; each Rear Wheel from all of 3 Wagons , weighed 1,080 Pounds, before fitting - and he built all three complete, working Wagons, two Ore-Carriers holding 8 Cubic Yards each and a Water-Wagon holding 6 tons or so to water the 16 to 24 Mules it took to haul the Wagon-Train out from the Mine. At age 15 I helped Dad to shape & fit one of the last of 6 Pairs of Sulky-Shafts which his father had bought pre-sawn in 1936, there were 3 pairs still in stock in 1976 (!) {and the old man had no trouble selling the two remaining pairs...}. Not long after that, he was asked to fit a pair of Steel Tyres to two Wooden Wheels, for an old Combination Harvester being restored, and I was enlisted to help in the second one of them. I've flown behind two Propellers which I designed, laminated with Ancestral G-Clamps, carved with the inherited Drawknife & Spokeshaeves, and shaped with the Grandparental Wood-Rasps....(!) ; so I sort of barely almost know enough to understand & appreciate what an amazing (Remnant) Expert Master Craftsman he actually is. And his Production Values are Superb. Do yourself a favour, maybe And check out the answer to your Question.... Look him up...(?) ! He's not churning out Wheels for Henry's Model-Ts But he is Still making an apparently handsome living, as a Wheelwright, Making and Repairing & Restoring Wooden Wheels, and Horse-Drawn Vehicles. Commercially, with a Main-Street Shopfront Workshop FULL of the most wonderfully Specialised Tools... I really enjoy watching the pair of you..., because You and he are like two Peas in Parallel Pods, On different pathways, Both in relentless Pursuit of preserving the Old Machinerys, in the Olden Ways, Least it all be forgot...(!). Kinda thing. Just(ifiably ?) sayin'. Such is life, Have a good one... Stay safe. ;-p Ciao !
I spend around 30 plus years measuring the position and angle of various jet engine cooling holes. The F110 engine ( f16 motor) for an example in first stage nozzle has around 600 cooling hole two vane noozle. The first stage blades and vanes are in the hottest place in a jet engine.
Seeing you present these blades that had a bad day it made wonder: How much damage can a jet engine absorb and still be repairable? Or put another way; at what point do you consider an engine a total loss?
That really depends on a lot of things. The common term for scrapping a modern engine is "beyond economical repair". But for vintage collector items like the Orendas and J47s I work on... the value goes up, so it has to be much further "gone" before it's scrapped. of course all the good bits would be saved. For an engine from an F35 to be scrapped, it needs to be more expensive to fix than a new one. But they are available new, and all the parts are still being made. For the old stuff, new old stock is getting harder to find, and new engines stopped popping up decades ago. The engines that I restore are made out of a combination of all the best parts from several engines that may be considered beyond saving on their own.
Seeing the size of the internal cooling passages on some of those blades brings a side question to my mind: Is there a secondary effect of reducing the mass of the blade, so reducing the forces on the blade root?
@agentjayz, cheers buddy. You might be surprised how similar “modern” turbine blades are in similarity to earlier turbofans. The huge difference is in the coatings applied, and that can go into an episode all of its own. Well coatings normally contain RE elements that are very, very expensive. In development we would start with full thickness coatings and then thin it out for “war on cost” until it looks like swiss cheese and go from there. There is just no substitute for rhenium, its just how low can you go (material life vs. cost). Then we could get into military engines vs. commercial and different cost concerns blah blah blah 😂. We are total nerds buddy ✈️.
A lot of less expensive jet engines like general aviation turboprops and helicopter turboshafts still have uncooled turbine blades that look like the one from the early 50s.
I wonder if the computer on a modern engine varies the compressor bleed air to the different cooling pathways during different operatig conditions? I know we are extracting smaller and smaller effiencies from modern engines, and varying the bypass air might account for several percents of thermal efficiency at cruising conditions.
Well, the turbine blade cooling air is never restricted, or controlled by anything other than what we describe here in the design process. But you may be interested in turbine case cooling, which is varied by changing airflow. It's called Active Clearance Control, and here is a vid I made a couple years ago featuring it as one of two subjects: "Racing Bikes and Active Clearance Control" ACC discussion starts at 22:00.
The amount of air which goes to the nozzle guide vanes can be controlled by Fadec. But never the 1st stage. For example on Pw4000 and Cf6- 80c2 the amount of air can be reduced during cruise conditions for the 2nd stage high pressure turbine nozzle guide vanes. Only reduced never cutoff
The manufacture of those things is very data intense. Everything in the process is logged, a few of each batch gets X-Rayed and that data is stored away for a very long time for traceability. If they make one today and it fails 30 years from today, the investigator will be able to track back to the initial making of the thing. At least that is supposed to be how it works. Pretty fascinating process, IMO to make so many and record so much and yea, each one cannot cost $1M...not practical.
I was watching a talk on this here RUclips by the chap that wrote the “The Secret Horse Power Race” book, he mentioned that BMW when developing a turbo charger for the FW190 engine used air cooling for the turbine due to a lack of Nickel needed to make high temperature steel. I’ve failed to find other mentions of this on the net.
That's true, here a foto of the BMW801TJ-turbine blades, which I shot in Deutsches Museum. upload.wikimedia.org/wikipedia/commons/thumb/2/2a/801-turbo2.jpg/1280px-801-turbo2.jpg They are made of CrMn-steel, cooling air was blown through.
I've had a quick scan of my copy of the book, but I haven't found any mention of this. However, on page 388, I've found a very small illustration of an FW190 turbocharged fighter with a Jumo 213 engine. I will look again, but there are several hundred pages of relatively small print. If you want detailed information on the cooled turbine blades of the wartime German jet engines, then I can recommend, 'German Jet Engine and Gas Turbine Development 1930-1945', by Antony Kay. However, I believe that it's out of print, and it will cost you at least GBP85 second hand. PS Don't be fooled by Kay characterising the German engines as "advanced". In 1944, their performance figures (in terms of pressure ratio, specific fuel consumption and power-to-weight ratio) were all inferior to Frank Whittle's W.1 engine, which took to the air in May 1941. Their handling was abysmal: starting was laborious and any rapid throttle movement was likely to result in a surge and a flameout. And of course, their life (typically 25 hours) was limited by the lack of suitable nickel alloys for the turbine aerofoils, hence the need for rudimentary air cooling. Compare this with the W.1 engine: in 1941, it did 25 hours of high power ground running before being released for 10 flight hours in the E.28/39.
where i work we do steel stacks the can hold 800°C ...we had numerous connected to a gas turbine generators ...thats some crasy ass technical solutions in those stacks. we didnt went to aircool the liners yet :D:D. when the inlet is of the size of two buses its 99.9 chance its one of those.
This is what I keep explaining to my pilot friends when they start talking about a mythical small, efficient, low cost turbine engine. The key is the temperature differential, or how hot you can run the turbine itself. The key to keeping the turbine buckets (aka blades) cool enough to survive a large temperature differential is through cooling air inside of it, and a film of protective cooling air surrounding it as protection from the combustion heat. The physics of moving air around tiny little passages gets harder and harder to do, and even more difficult to manufacture. Making a 250hp gas turbine engine that is efficient and cheap, is simply not possible, at least not in any means we have today. Film cooling was used in the V2 rocket engine in WW2, quite effectively.
Something I've wondered about for a long time: what is the smallest feasible gas turbine engine (either axial or centrifugal)? I've seen pretty tiny ones (like IDK maybe 4" diameter) but can they be made smaller still? And if not, what is the limiting factor? I can think of a couple of candidates: 1) strength of materials (the smaller they are the faster they spin, right? So at some point everything will fly apart at the rotational speeds required); 2) thermodynamic: smaller turbines means less space available for gas expansion; 3) engineering: the smaller you go, the more microscopic the tolerances get.
What do you want, and how much money do you have? And "feasible" means a different thing to different people. If you are super rich, and just want to play, I'm sure you could make a jet engine out of a dentist drill. It's a tiny air turbine, and you would need to micromachine a compressor for it, and a fuel system, and a combustion section.
I have a related question. I read somewhere recently that one way to significantly reduce drag on a torpedo (as in a torpedo from a submarine) is to eject compressed air out of the torpedo nose so that the torpedo essentially moves through a near-still (relative to the torpedo) envelope of air (which would have significantly less drag than moving through the water). Leaves me wondering if the cooling air ejected out of the leading edge of a turbine blade, which at that point would be moving at the same, or very nearly the same, speed as the blade, helps reduce drag on the blade?
The turbine blades are not "being propelled" through the gases, so they do not need reduction in friction. The blades are being moved by the gases, which are moving faster than the blades. If anything, friction is helping the gases move the blades.
@@AgentJayZ Sorry, but I don’t think you have thought this out, and I’ve been thinking about how to explain this to your subscribers. As buckybucky8596 has suggested, turbine blades can be considered as airfoils/aerofoils, albeit highly cambered, which are intended to produce a lift force in the circumferential direction. However, taking into account their stagger angle, their lift force could conventionally be considered as acting as approximately normal to the stagger angle, with a component in the axial direction ie, producing a rearwards force. But if there is a lift force, there must also be a drag force, which could conventionally be considered as acting at right angles to the lift force. However, this would mean that there would be a component in the circumferential direction, ie, producing a force opposing the circumferential component of the lift force. You suggest that, as the turbine blades are "not being propelled" through the gas flow, then this must make a difference. However, an aerofoil in a wind tunnel is not being propelled through the air flow. Nevertheless, we treat the results as being representative of an aerofoil being propelled through the air by an aeroplane - sorry, airplane. So, how would increasing the 'friction' of a turbine blade improve its function and increase its efficiency? It wouldn’t. PS We consider 'lift' and 'drag' as two separate and distinct forces: it's a useful convention but, in reality there is really only one total aerodynamic force acting on an aerofoil (or any body in a moving air flow), albeit produced by various interactions of the air with the aerofoil. 'Lift' and 'drag' are effectively components of that force.
Cooled cooling air for the turbine, AgentJayZ? Yes, it was done years ago - by the Russians in one of their military turbofans. If you trawl the internet, you might be able to find a photo of a sectioned engine with a mass of small tubes in the bypass duct. I did look at cooled cooling air and putting a heat exchanger in the bypass duct of a future military engine project at R-R Bristol, many years ago. Having told you this, I hope that I don't get a knock at the door and get taken away by some men in dark suits.
@@kizzjd9578 a quick search did pull up one of Agent Jay's videos where he addressed the various manufacturing methods over the years... ruclips.net/video/jCb6-LGfeHg/видео.html "Turbine Blade Production Techniques".
I think the logic behind the serpentine configuration has to do with making the air do more work until it it ‘uses up’ its ability to absorb heat thus making a specific mass of air do more work than simply one pass of the same mass. Sorry for that long sentence…
AgentJayZ could possibly have shown us pages 88 and 89 of the 1986 edition of Rolls-Royce's 'The Jet Engine' book. The diagram on page 88 shows the "serpentine" complexity of a Trent HP turbine blade of that era. There are two parameters, which I used to give a little lecture on, many, many years ago, back in the 1970s: they are 'cooling efficiency' and 'cooling effectiveness'. Perhaps I should venture into the loft and see if I've kept any notes, because my memory is hazy: nevertheless, here goes. As I recall, cooled single pass blades typically have low cooling effectiveness, but can have relatively higher cooling efficiency. The amount of cooling that is done is limited, but the increase in temperature of the cooling air is high, hence 'efficiency'. In comparison, cooled multi-pass blades have high effectiveness, but may have relatively lower efficiency. Perhaps that sounds contrary to your suggestion: I will try to do some revision.
A notable professor once said, "Let the rest of the world worry about water". When a civilizations ability to move is ruled by exothermic reaction, where your wallet releases heat, and now is even given cooling holes so it can release more heat! Then we have reached the maximum potential of a turbine blade and the said societies ability to evolve. Therefore it's up to the individual to fight for their right in how their ability to move is ruled. Physics that include an endothermic reaction would loosen this shackle, cool the wallet, reduce the need of exotic geometric shapes and balance the equation allowing evolution to continue. Change comes from the bottom!
Can the cooling air be intercooler to lower it's temperature? Would that be worth the hassle? Maybe air that was too cold would cause thermal shock to the blades?
Not worth doing; it works fine now, and the drag and weight of an intercooler would not help enough to be worth it. The engineers where I work dream of materials that wouldn't need cooling at all!
Uncle Kenny is right. Here is an answer to a comment just above yours: such a small amount of air is used for cooling compared to total mass flow, the expense and complication would not be worth the bother. Also, when you want to carry heat away from something that is over 1500F, and you use air at even 500F, it's going to work just fine.
It's not called a PTO. If you want to say power take off in generic terms... that's not how it is described. Most helicopter engines use a free power turbine, which drives a reduction gear train, with the final output being a rotating shaft, which then feeds power to the main helicopter gearbox. I have a series of videos where we work on the T58, a medium-lift helicopter turboshaft engine, rated at just over 1200 Hp. The first vid in the playlist is here: ruclips.net/video/vgDEhLj_ySw/видео.html
Excellent presentation, sir. Question: possible to use low-pressure air from the early compressor stage passing through an intercooler to lower the temperature of high-pressure air from later stages of the compressor in order to increase the cooling capacity for turbine blad cooling? ~just curious~ 👍
Not necessary to add Rube Goldberg complexity. Blade cooling is accomplished with a tiny fraction of total compressor air. I more cooling is needed, the design is changed to take more. These adjustments are done in the development of a new engine design.
The straight answer to your question is: yes, it is possible - and the Russians did it some years ago in one of their military turbofans. Please see the comment I've previously posted. However, as AgentJayZ has suggested, in answer to similar questions, if it was a really good idea, then it would have been taken up more widely. I agree with him that it's just not worth the complexity - and the weight penalty.
Diffuser air is used for 2 reasons. The pressure of cooling air MUST be higher than combustion gas pressure, otherwise you would not get cooling air effusion, you'd get hot gas ingestion. AND. The temp of the earlier stage would be too LOW and cause thermal differential cracking. Too cool is bad. Modern engines run very hot, and we only need to cool them to just below a "critical temp" to stop creep and TBC damage. Rolls Royce also uses single crystal blades for Crack resistance.
Maybe a stupid question, but is it possible to have regeneratively cooled blades (similar to rocket engine combustion chamber) by running fuel trough them? I guess coking would be a problem…
No need. Air works best, otherwise something else would be used. Well, maybe you are smarter and have better ideas than the thousands of professional engineers constantly working to improve engine performance...
Apologies because its not fully relevant. Its eh almost relevant though. It is about engine cooling. I recently found out that Top fuel dragsters are cooled by their fuel. Because they run on almost pure Nitro which has its own oxygen supply they actually can and do use more fuel than air. (a car or jet, burns about 15 times more air by weight than fuel) Dragsters have about 40 fuel injectors, some in the supercharger and other parts of the airflow. So the fuel is providing almost all of the lubrication and cooling. thats why they choose to run them on a mix that uses more fuel than air.
A top fuel engine has an overhaul interval of about 5 seconds when running at full throttle. Any gas turbine in good condition can go over two years at max rated output before any work needs to be done. When run until something gives, several years. I know a little about piston engines, enough to know there are very few similarities with the stuff I work on.
Does GE or any other aircraft Engine manufacturer make a triple spool engine like the Rolls-Royce RB211 Trent, they were the first bleed air turbine cooling turbojet cause I have seen possibly from you How's the pt6 going updates please
I believe that the Russians designed and built a three-spool, high bypass turbofan some years ago. And, of course, the Turbo Union RB199 engine, which powered the Panavia Tornado, had three spools.
@@grahamj9101 well I guess our Rolls-Royce RB211 high bypass originally made for the Lockheed TriStar and when fitted to the Qantas B747 had a fuel saving of 1 million lb of fuel per aircraft had to be investigated The RR RB 199 engine I have a fourth stage turbine bought e-bay Interesting comment thank you for your reply
Don't light the combustors. 😅 Seriously though, it'd reduce output power. Air film bleed cooling, along with coating and internal cooling for best results. Even if it's all ceramic.
Such a small amount is used compared to total mass flow, the expense and complication would not be worth the bother. Also, when you want to carry heat away from something that is over 1500F, and you use air at even 500F, it's going to work just fine.
There’s no point because when we design an engine, you can chose from where you want the cooling air with temps varying from T1 to T2.8ish. If you want cooler air, just take from a station closer to the inlet. Plus you dont want to reduce the temp in the gas path with really cold air because that means that less work can be produced by the next turbine stage.
@@AgentJayZ That’s impossible.. But I really like Lucifer the cat , Corporal Clegg and the entire Wall album , although I love The Dark Side of the Moon and Animals. Love it all Why..? I had a cool Siamese cat when I was a kid , my dad was wounded in WWII and the first time I drank alcohol I was listening to The Wall.
I belt and polish those blades daily. It's crazy the amount of work that goes into them from start to finish.
Incredible how heavy some of these older turbine blades seem to be - they must be pulling like crazy on the shaft at high RPMs. Anyway - thanks for showing all these, amazing stuff. Would be fun to see how they manufacture the blades and get those tiny holes in there.
They are all heavy. At takeoff, each blade is pulling with dozens of tons of force on its mount, and it is glowing orangey red hot.
As I watch this mams videos. I realize his education is way beyond an average gas turbine engine mechanic. He has a very good understanding of very complex concepts in design and heat transfer technologies and metallurgy. Metallurgy is a subject that is more difficult than a nuclear physicist. Metallurgy is so complex that many will specialize in a group of metals such as non ferrous, ferrous, Titanium and it's alloys, Grasses and bronze, etc... I used to teach Metallurgy and am impressed with his knowledge of so many of these areas of expertise. I also was a welding engineer who built gast tibine engine hot zone components, mostly combustion cans. Someday I want to visit his shop and learn more in person. My last bucket list thing to do while alive. May visit after I pass...😅
At prima machine training the past few weeks. I manufacture and produce these parts. I love your videos. I make replacement parts for most of what you show.
Investment casting was revived and refined to make the complex internals of blades. It was state of the art in the 1970's when I studied it formally as part of Materials Science, Thermodynamics and Fluid Mechanics.
There were of course gaping chasm of untold wisdom. Which is why I'm watching this channel.
I'm not a turbine engine engineer, but I have some training in heat exchanger design.
The objective here is to maximize the heat transfer to the cooling air while minimizing the mass flow rate of the cooling air, since this is what costs compressor power and therefore fuel consumption. Yes, the Series flow path potentially increases the max temperature of the cooling air in the blade, but this also means that the cooling air has absorbed more heat per mass.
Sure, you could just restrict the outlet of air, but then the air is moving very slowly inside the blade, which reduces the heat transfer coefficient. And then you also have a thermal gradient within the air in the blade that results in the air at the tips being hotter, whereas with the series path, the temperatuee gradient of the air in the blade will somewhat average out radially.
This temperature gradient will also be present in the air exiting the film cooling holes.
The series path will have more pressure drop, but you likely have more differential pressure than you need for the convective cooling path because the exit pressure is somewhere between the stage inlit and stage outlet pressures, whereas the film cooling exit pressure is the turbine inlet pressure.
Out of curiosity; if you were to compare the area of the inlet section to the area of the outlets combined, do you generally keep those areas as close to the same as possible?
Another good question which i have never thought about. I would think the rate of flow would be metered by outlet area, but that would only be a guess. I really don't know where to turn for a definitive answer. It's such a specialized niche question.
But, maybe Graham knows. He designed turbine engines for his whole career.
@@SirSpence99 That's probably actually quite a complicated question. If you want the pressure inside the blade to be as high as possible, you'd have the inlet wide open and control total flow by manipulating the outlets. You also have to keep in mind that the flow out of each outlet will depend on the size, shape, pressure inside the blade at the outlet, Pressure outside the blade at the outlet, and cooling air temperature at the outlet.
I don't know that there's a strong reason to control the bulk pressure of the air inside the blade, so that will probably be secondary after optimizing the distribution of mass in the blade, since mass at the outside increases load on the entire blade, whereas mass at the root can help support the blade structurally. Moving metal around also affects manufacturability, steady state and transient thermal performance, vibration modes, etc.
So there's at least five domains for optimization: External flow, internal flow, thermal, structural, and manufacturing.
That goes a lot towards explaining why these engines and especially their development are so expensive.
If you don't know, like I don't know, why spend three times as many words saying you don't know?
You seem like a nice guy, trying to help, but guesses are usually treated as chaff.
Carry on, as if normal.
@@AgentJayZ The rule of thumb I follow when designing ducts for my 3d printer is that I maintain the same cross-sectional area unless I want to increase velocity and I also make sure I never increase area and then decrease it.
According to my understanding of physics, (from looking into rocket nozzles, though that is rather different) decreasing area increases velocity while decreasing effective pressure given an unchanging source. Given that "high static pressure" fans basically don't exist and that fans of all kinds lose flow rate as the required pressure increases, I try not to decrease the area of my ducts unless I have to.
What I'm mostly curious on is which part (if any) I'm wrong on. Considering I'm doing cooling much like the vents on the leading edge in your examples are doing, this is something that would actually be quite helpful for me to know. (I'm currently designing 3d printer cooling ducts so they need to vent air out a bit of a distance to cool the part.)
I suppose that means my question is two-fold, one, does changing the area after some distance in a duct decrease flow-rate and do you want higher velocity or higher flow-rate for cooling.
Great video as always! Some pertinent terms you could throw into this conversation (to help tie together everything you're talking about) are 'surface area', 'choked flow', 'dwell time', and 'gas density'. Yes, lots of fluid dynamics and thermodynamics math over both our heads (and I'm even in the mass flow measurement business!). In short, we're trying to pass a low molecular weight gas over a much higher molecular weight metal to draw (lots of) heat energy away. Or at least enough to maintain a nice safety margin on the metalurgical temp limits.
Some 30+ years ago I met a guy (working as a car mechanic in Tucson AZ ironically) who apparently revolutionized the manufacturer of these cooled turbine blades; specifically for private jet sized engines. Interesting fellow, not sure what he was doing working on my Honda with that kind of resume!
Anyway, it was great to finally see a breakdown (literally!) on what theses blades are all about. Thanks again for making these videos.
What baffles me when I look at the engineering of these turbine engines is how the designers and engineers manage the complexitiy within their process.
When I am doing my little tinkering projects as a hobbyist I always try to keep it as simple and functional as possible. But a solution to an upcoming design problem often leads to a feature that comes with its own challenges, requirements and issues. And this spiral of fixes and more issues can grow really fast.
I do not even dare to think of the level of complexity when designing rocket or gas turbine engines. Keeping it simple yet efficient and effective is really an art form.
When I worked at a combined cycle plant, we had rotor cooling air. Bleed air was passed through a water to air heat exchanger (aka kettle boiler). This cooled the air and added some heat to the feed water for the steamer setup.
Siemens SGT5000F
The cooling air, once it has passed through these blades, become part of the gas path, so there is no way to collect it and use it.
Informative. I did not know that some were air cooled. Thank you for video
They are all air cooled. Since the late 1960's anyway. And there are very few airliners from the 60's still flying, if any at all.
AJZ, thank you for your explanation and demonstration.
In a reciprocating engine, the boundary layer usually does a good job at insulating the metal bits from peak combustion temperatures. Undet knock however, supersonic waves scour the boundary layer from the surface often resulting in holes burnt through piston tops.
A gas turbine situation is a little different mainly because there's no respite from heat so sustaining a cooler boundary layer requires some "help" in the form of air bleeds.
The pressure in the combustion chamber can not exceed the pressure in the compressor. The pressure is assumed as constant ideally. However it drops a little.
It's still amazing to me that those early gas turbine engines, and even piston engines, were designed and built by extremely smart people with nothing but pencil, paper, slide rules, and a vision of what they wanted to achieve. No computers or AI modeling, just ingenuity.
A good slide rule can provide an accuracy of 2~3 significant digits, which is enough for most engineering applications.
The HPT blades on the Rolls-Royce Trent 1000 TEN have a life of 1000 cycles (flights) mandated by EASA (if they last that long before cracking due to creep) and cost around $25,000 USD each
Is it the fatigue failure ?
Rolls has been GROWING titanium single crystal blades for their "Trent" series ... with internal passages and surface holes somehow grown in place. The process is proprietary and secret.
Single crystal turbine blades are by no means new: R-R was casting them for both civil and military engines well before I took early retirement twenty years ago. Essentially, they are cast, using the 'lost wax' process. The single crystal is then 'grown' by slowly withdrawing the ceramic mould from the furnace, so that the blade progressively cools and solidifies from root to tip. This much is not secret: more details can be found on the internet.
However, I have to tell you that HP turbine blades are not cast in titanium: it's not a turbine blade material. Think in terms of high-temperature-resistant nickel-cobalt alloys, such as MAR-M 002.
Turbine blades are not made of any type of titanium alloy. Ti is soft, weak, and prone to melting or even catching fire in combustion gases.
Ti is stronger, harder, heavier, and more temperature resistant then aluminum, but compared to Refractory alloys of nickel and iron, Ti is weaker, softer, lighter, and less temperature resistant.
Turbine blades made from Wensleydale cheese, and even balsa wood, are just as good as those made of titanium.
@@AgentJayZ Titanium can catch fire in a compressor, where the air pressure and temperature is high enough. There is something known as the 'titanium fire line', downstream of which, if there is (eg) a heavy tip rub, then a fire may be initiated. If this occurs, all the titanium aerofoils (and possibly the discs) will be consumed. The fire may be so intense as to burn through the engine casings and the airframe structure.
I am aware that such an event happened somewhere over Canada, some years ago, to a twin-engined fighter, which was not of Canadian or US origin. The wingman who observed the event said it was the brightest white light that he'd ever seen.
The second engine continued to run, keeping the aircraft in the air, but its electrical control connections had been destroyed, and possibly some of the aircraft's flight controls too.
There was no chance of getting the aircraft down to a safe landing, so the two crew used their ejection seats, and the final result was a smoking hole somewhere in the Canadian wilderness.
@@AgentJayZ I approve of your choice of cheese. Unfortunately, the UK has called off trade agreement talks with Canada, and a whopping increase in tariff will be imposed on British cheese imports.
We all know that Canadians make really good cheese. We also know that we use recipes from other places. Canadian cheddar is darn good. I think many of us don't realize that it's named after a place, that makes the real thing. It is more expensive, and to regular folks like me, that's a shame.
I would love it if you ground down more turbine blades to discuss cooling paths and heat management.
G'day Jay,
Yay Team !
A beautiful
Explainification ;
I enjoyed every bit
Of it...
Thankyou.
As regards your
Parting Question,
"Who makes Cars with Wooden Spoked Wheels today (?)... Nobody !"
Well, um, probably because I posted a Video showing two of my grandfather's Wheelwrighting Tools which I'd cleaned and oiled-up for their first use in 25 years (and then, I was using them for the first time since 1936 when my grandfather last made a Wagon Wheel Spoke with them)... ;
The mighty RUclips Algae-Rythm has been feeding me with back-catelogue Uploads from
@ Engels Coach Workshop Channel...
Whereas I use the 1905 Patent Tools on my grandfather's Brace & Bit, Dave Engel has a pair of Drill-Presses, one with a Spoke-Pointer and the other with a Spoke-Tennon Cutter...
He scratch-built Full Size Replicas of the 3 Wagons in the Death Valley Borax Wagon-Train - which used to operate from 1892 till 1896 or something....; each Rear Wheel from all of 3 Wagons , weighed 1,080 Pounds, before fitting - and he built all three complete, working Wagons, two Ore-Carriers holding 8 Cubic Yards each and a Water-Wagon holding 6 tons or so to water the
16 to 24 Mules it took to haul the
Wagon-Train out from the Mine.
At age 15 I helped Dad to shape & fit one of the last of 6 Pairs of Sulky-Shafts which his father had bought pre-sawn in 1936, there were 3 pairs still in stock in 1976 (!) {and the old man had no trouble selling the two remaining pairs...}.
Not long after that, he was asked to fit a pair of Steel Tyres to two Wooden Wheels, for an old Combination Harvester being restored, and I was enlisted to help in the second one of them.
I've flown behind two Propellers which I designed, laminated with Ancestral G-Clamps, carved with the inherited Drawknife & Spokeshaeves, and shaped with the Grandparental Wood-Rasps....(!) ; so I sort of barely almost know enough to understand & appreciate what an amazing (Remnant) Expert Master Craftsman he actually is.
And his Production Values are
Superb.
Do yourself a favour, maybe
And check out the answer to your
Question....
Look him up...(?) !
He's not churning out
Wheels for Henry's Model-Ts
But he is
Still making an apparently handsome living, as a
Wheelwright,
Making and Repairing & Restoring Wooden Wheels, and
Horse-Drawn Vehicles.
Commercially, with a
Main-Street
Shopfront
Workshop
FULL of the most wonderfully
Specialised
Tools...
I really enjoy watching the pair of you..., because
You and he are like two
Peas in
Parallel Pods,
On different pathways,
Both in relentless
Pursuit of preserving the
Old Machinerys, in the
Olden Ways,
Least it all be forgot...(!).
Kinda thing.
Just(ifiably ?) sayin'.
Such is life,
Have a good one...
Stay safe.
;-p
Ciao !
I spend around 30 plus years measuring the position and angle of various jet engine cooling holes. The F110 engine ( f16 motor) for an example in first stage nozzle has around 600 cooling hole two vane noozle. The first stage blades and vanes are in the hottest place in a jet engine.
Seeing you present these blades that had a bad day it made wonder: How much damage can a jet engine absorb and still be repairable? Or put another way; at what point do you consider an engine a total loss?
That really depends on a lot of things. The common term for scrapping a modern engine is "beyond economical repair".
But for vintage collector items like the Orendas and J47s I work on... the value goes up, so it has to be much further "gone" before it's scrapped. of course all the good bits would be saved.
For an engine from an F35 to be scrapped, it needs to be more expensive to fix than a new one. But they
are available new, and all the parts are still being made.
For the old stuff, new old stock is getting harder to find, and new engines stopped popping up decades ago.
The engines that I restore are made out of a combination of all the best parts from several engines that may be considered beyond saving on their own.
Jumo 109-004B Orkan engines had hollow bleed air cooled blades.
Good to know.
Folded sheet metal, made by WMF...
I just made a similar comment about BMW during the war.,
@@hiha2108
I mentioned that on the previous video.
Seeing the size of the internal cooling passages on some of those blades brings a side question to my mind:
Is there a secondary effect of reducing the mass of the blade, so reducing the forces on the blade root?
every gram counts on an airplane or helicopter.
@agentjayz, cheers buddy. You might be surprised how similar “modern” turbine blades are in similarity to earlier turbofans. The huge difference is in the coatings applied, and that can go into an episode all of its own. Well coatings normally contain RE elements that are very, very expensive. In development we would start with full thickness coatings and then thin it out for “war on cost” until it looks like swiss cheese and go from there. There is just no substitute for rhenium, its just how low can you go (material life vs. cost). Then we could get into military engines vs. commercial and different cost concerns blah blah blah 😂. We are total nerds buddy ✈️.
A lot of less expensive jet engines like general aviation turboprops and helicopter turboshafts still have uncooled turbine blades that look like the one from the early 50s.
I wonder if the computer on a modern engine varies the compressor bleed air to the different cooling pathways during different operatig conditions? I know we are extracting smaller and smaller effiencies from modern engines, and varying the bypass air might account for several percents of thermal efficiency at cruising conditions.
Well, the turbine blade cooling air is never restricted, or controlled by anything other than what we describe here in the design process.
But you may be interested in turbine case cooling, which is varied by changing airflow.
It's called Active Clearance Control, and here is a vid I made a couple years ago featuring it as one of two subjects:
"Racing Bikes and Active Clearance Control"
ACC discussion starts at 22:00.
The amount of air which goes to the nozzle guide vanes can be controlled by Fadec. But never the 1st stage. For example on Pw4000 and Cf6- 80c2 the amount of air can be reduced during cruise conditions for the 2nd stage high pressure turbine nozzle guide vanes. Only reduced never cutoff
The manufacture of those things is very data intense. Everything in the process is logged, a few of each batch gets X-Rayed and that data is stored away for a very long time for traceability. If they make one today and it fails 30 years from today, the investigator will be able to track back to the initial making of the thing. At least that is supposed to be how it works. Pretty fascinating process, IMO to make so many and record so much and yea, each one cannot cost $1M...not practical.
I was watching a talk on this here RUclips by the chap that wrote the “The Secret Horse Power Race” book, he mentioned that BMW when developing a turbo charger for the FW190 engine used air cooling for the turbine due to a lack of Nickel needed to make high temperature steel.
I’ve failed to find other mentions of this on the net.
That's true, here a foto of the BMW801TJ-turbine blades, which I shot in Deutsches Museum. upload.wikimedia.org/wikipedia/commons/thumb/2/2a/801-turbo2.jpg/1280px-801-turbo2.jpg
They are made of CrMn-steel, cooling air was blown through.
I've had a quick scan of my copy of the book, but I haven't found any mention of this. However, on page 388, I've found a very small illustration of an FW190 turbocharged fighter with a Jumo 213 engine. I will look again, but there are several hundred pages of relatively small print.
If you want detailed information on the cooled turbine blades of the wartime German jet engines, then I can recommend, 'German Jet Engine and Gas Turbine Development 1930-1945', by Antony Kay. However, I believe that it's out of print, and it will cost you at least GBP85 second hand.
PS Don't be fooled by Kay characterising the German engines as "advanced". In 1944, their performance figures (in terms of pressure ratio, specific fuel consumption and power-to-weight ratio) were all inferior to Frank Whittle's W.1 engine, which took to the air in May 1941. Their handling was abysmal: starting was laborious and any rapid throttle movement was likely to result in a surge and a flameout. And of course, their life (typically 25 hours) was limited by the lack of suitable nickel alloys for the turbine aerofoils, hence the need for rudimentary air cooling.
Compare this with the W.1 engine: in 1941, it did 25 hours of high power ground running before being released for 10 flight hours in the E.28/39.
@@grahamj9101 FW190 not 109. I always seem to do that.
I was talking from memory so it might not of been BMW.
If I get a chance I shall check.
At 27:52
ruclips.net/video/QailgWUZ1XE/видео.html&si=vf9sO2-NGx2xMrWn?t=27m52s
12:05 mentions it being used on a Jumo
ruclips.net/video/x3xmJ74ME7E/видео.htmlsi=gYma_1jOQtQ-OpGv?t=12m05s
where i work we do steel stacks the can hold 800°C ...we had numerous connected to a gas turbine generators ...thats some crasy ass technical solutions in those stacks. we didnt went to aircool the liners yet :D:D. when the inlet is of the size of two buses its 99.9 chance its one of those.
This is what I keep explaining to my pilot friends when they start talking about a mythical small, efficient, low cost turbine engine. The key is the temperature differential, or how hot you can run the turbine itself. The key to keeping the turbine buckets (aka blades) cool enough to survive a large temperature differential is through cooling air inside of it, and a film of protective cooling air surrounding it as protection from the combustion heat. The physics of moving air around tiny little passages gets harder and harder to do, and even more difficult to manufacture. Making a 250hp gas turbine engine that is efficient and cheap, is simply not possible, at least not in any means we have today. Film cooling was used in the V2 rocket engine in WW2, quite effectively.
Thanks.
Can you show a pathway of supplying air to discs and blades for air cooled blades?
Yes. Have a look at this recent video. More info is in the description. ruclips.net/video/AVQJV2utKxs/видео.html
How do they make those blade with all the holes inside? No wonder they are $10,000 each.
I made a video called Turbine Blade Production Techniques.
@@AgentJayZ Thanks. Your channel is like sipping from a firehose.
Something I've wondered about for a long time: what is the smallest feasible gas turbine engine (either axial or centrifugal)? I've seen pretty tiny ones (like IDK maybe 4" diameter) but can they be made smaller still?
And if not, what is the limiting factor? I can think of a couple of candidates: 1) strength of materials (the smaller they are the faster they spin, right? So at some point everything will fly apart at the rotational speeds required); 2) thermodynamic: smaller turbines means less space available for gas expansion; 3) engineering: the smaller you go, the more microscopic the tolerances get.
What do you want, and how much money do you have? And "feasible" means a different thing to different people.
If you are super rich, and just want to play, I'm sure you could make a jet engine out of a dentist drill. It's a tiny air turbine, and you would need to micromachine a compressor for it, and a fuel system, and a combustion section.
We use nitrogen powered turbines to drill out calcified heart arteries before placing stents to improve blood flow.
I have a related question. I read somewhere recently that one way to significantly reduce drag on a torpedo (as in a torpedo from a submarine) is to eject compressed air out of the torpedo nose so that the torpedo essentially moves through a near-still (relative to the torpedo) envelope of air (which would have significantly less drag than moving through the water). Leaves me wondering if the cooling air ejected out of the leading edge of a turbine blade, which at that point would be moving at the same, or very nearly the same, speed as the blade, helps reduce drag on the blade?
It's an interesting suggestion, but it was never discussed when I was involved in turbine design many years ago
The turbine blades are not "being propelled" through the gases, so they do not need reduction in friction. The blades are being moved by the gases, which are moving faster than the blades. If anything, friction is helping the gases move the blades.
@@AgentJayZ But don't the turbine blades act as 'air foils' so less drag would be a plus?
@@buckybucky8596 Yes, and I'm about to post a reply to AgerntJayZ.
@@AgentJayZ Sorry, but I don’t think you have thought this out, and I’ve been thinking about how to explain this to your subscribers.
As buckybucky8596 has suggested, turbine blades can be considered as airfoils/aerofoils, albeit highly cambered, which are intended to produce a lift force in the circumferential direction. However, taking into account their stagger angle, their lift force could conventionally be considered as acting as approximately normal to the stagger angle, with a component in the axial direction ie, producing a rearwards force.
But if there is a lift force, there must also be a drag force, which could conventionally be considered as acting at right angles to the lift force. However, this would mean that there would be a component in the circumferential direction, ie, producing a force opposing the circumferential component of the lift force.
You suggest that, as the turbine blades are "not being propelled" through the gas flow, then this must make a difference. However, an aerofoil in a wind tunnel is not being propelled through the air flow. Nevertheless, we treat the results as being representative of an aerofoil being propelled through the air by an aeroplane - sorry, airplane.
So, how would increasing the 'friction' of a turbine blade improve its function and increase its efficiency? It wouldn’t.
PS We consider 'lift' and 'drag' as two separate and distinct forces: it's a useful convention but, in reality there is really only one total aerodynamic force acting on an aerofoil (or any body in a moving air flow), albeit produced by various interactions of the air with the aerofoil. 'Lift' and 'drag' are effectively components of that force.
The CF6-6 and the TF-39 had the two in one blades. They called them buckets.
The steam guys called them buckets, and it caught on. Such a term is archaic and some would say inappropriate these days.
I worked at general electric in evendale and that was what they called the area that made those parts. I have no idea where the the term came from
There is another book
Irwin E Treager Aircraft Gasturbine engine technology.
Very practical book like the Jeppesen one.
Cooled cooling air for the turbine, AgentJayZ? Yes, it was done years ago - by the Russians in one of their military turbofans. If you trawl the internet, you might be able to find a photo of a sectioned engine with a mass of small tubes in the bypass duct.
I did look at cooled cooling air and putting a heat exchanger in the bypass duct of a future military engine project at R-R Bristol, many years ago. Having told you this, I hope that I don't get a knock at the door and get taken away by some men in dark suits.
If it was a good idea, it would be incorporated into modern engine designs.
I am again impressed with the range of your knowledge.
Thanks.
❤
I wonder if they somehow injectionmold those or theyre drilled after?
I think investment casting is used for creating the internal passages?? I suspect Agent Jay has done a video on this in the past.
@@SkyhawkSteve havent seen any videos.
@@kizzjd9578 a quick search did pull up one of Agent Jay's videos where he addressed the various manufacturing methods over the years... ruclips.net/video/jCb6-LGfeHg/видео.html "Turbine Blade Production Techniques".
IIRC edm is used for some of the holes.
I think the logic behind the serpentine configuration has to do with making the air do more work until it it ‘uses up’ its ability to absorb heat thus making a specific mass of air do more work than simply one pass of the same mass. Sorry for that long sentence…
AgentJayZ could possibly have shown us pages 88 and 89 of the 1986 edition of Rolls-Royce's 'The Jet Engine' book. The diagram on page 88 shows the "serpentine" complexity of a Trent HP turbine blade of that era.
There are two parameters, which I used to give a little lecture on, many, many years ago, back in the 1970s: they are 'cooling efficiency' and 'cooling effectiveness'. Perhaps I should venture into the loft and see if I've kept any notes, because my memory is hazy: nevertheless, here goes.
As I recall, cooled single pass blades typically have low cooling effectiveness, but can have relatively higher cooling efficiency. The amount of cooling that is done is limited, but the increase in temperature of the cooling air is high, hence 'efficiency'.
In comparison, cooled multi-pass blades have high effectiveness, but may have relatively lower efficiency.
Perhaps that sounds contrary to your suggestion: I will try to do some revision.
A notable professor once said, "Let the rest of the world worry about water". When a civilizations ability to move is ruled by exothermic reaction, where your wallet releases heat, and now is even given cooling holes so it can release more heat! Then we have reached the maximum potential of a turbine blade and the said societies ability to evolve. Therefore it's up to the individual to fight for their right in how their ability to move is ruled. Physics that include an endothermic reaction would loosen this shackle, cool the wallet, reduce the need of exotic geometric shapes and balance the equation allowing evolution to continue. Change comes from the bottom!
"Um... I'll have what he's having."
Can the cooling air be intercooler to lower it's temperature? Would that be worth the hassle? Maybe air that was too cold would cause thermal shock to the blades?
Not worth doing; it works fine now, and the drag and weight of an intercooler would not help enough to be worth it.
The engineers where I work dream of materials that wouldn't need cooling at all!
Uncle Kenny is right. Here is an answer to a comment just above yours: such a small amount of air is used for cooling compared to total mass flow, the expense and complication would not be worth the bother. Also, when you want to carry heat away from something that is over 1500F, and you use air at even 500F, it's going to work just fine.
Jay - What is the approximate thickness of the ceramic coating applied to the solid turbine blades to extend their service life ?
I think it is less than ten thousandths of an inch. Less than .010"
Do you have a video showing the pto from turbine shafts. More to the point which axle is it taken from. My interest is heli engine
It's not called a PTO.
If you want to say power take off in generic terms... that's not how it is described.
Most helicopter engines use a free power turbine, which drives a reduction gear train, with the final output being a rotating shaft, which then feeds power to the main helicopter gearbox.
I have a series of videos where we work on the T58, a medium-lift helicopter turboshaft engine, rated at just over 1200 Hp.
The first vid in the playlist is here: ruclips.net/video/vgDEhLj_ySw/видео.html
Excellent presentation, sir. Question: possible to use low-pressure air from the early compressor stage passing through an intercooler to lower the temperature of high-pressure air from later stages of the compressor in order to increase the cooling capacity for turbine blad cooling? ~just curious~
👍
Not necessary to add Rube Goldberg complexity.
Blade cooling is accomplished with a tiny fraction of total compressor air. I more cooling is needed, the design is changed to take more.
These adjustments are done in the development of a new engine design.
The straight answer to your question is: yes, it is possible - and the Russians did it some years ago in one of their military turbofans. Please see the comment I've previously posted.
However, as AgentJayZ has suggested, in answer to similar questions, if it was a really good idea, then it would have been taken up more widely. I agree with him that it's just not worth the complexity - and the weight penalty.
Diffuser air is used for 2 reasons. The pressure of cooling air MUST be higher than combustion gas pressure, otherwise you would not get cooling air effusion, you'd get hot gas ingestion. AND. The temp of the earlier stage would be too LOW and cause thermal differential cracking. Too cool is bad. Modern engines run very hot, and we only need to cool them to just below a "critical temp" to stop creep and TBC damage. Rolls Royce also uses single crystal blades for Crack resistance.
Maybe a stupid question, but is it possible to have regeneratively cooled blades (similar to rocket engine combustion chamber) by running fuel trough them? I guess coking would be a problem…
No need. Air works best, otherwise something else would be used. Well, maybe you are smarter and have better ideas than the thousands of professional engineers constantly working to improve engine performance...
Apologies because its not fully relevant. Its eh almost relevant though. It is about engine cooling. I recently found out that Top fuel dragsters are cooled by their fuel. Because they run on almost pure Nitro which has its own oxygen supply they actually can and do use more fuel than air. (a car or jet, burns about 15 times more air by weight than fuel) Dragsters have about 40 fuel injectors, some in the supercharger and other parts of the airflow. So the fuel is providing almost all of the lubrication and cooling. thats why they choose to run them on a mix that uses more fuel than air.
A top fuel engine has an overhaul interval of about 5 seconds when running at full throttle. Any gas turbine in good condition can go over two years at max rated output before any work needs to be done.
When run until something gives, several years.
I know a little about piston engines, enough to know there are very few similarities with the stuff I work on.
Does GE or any other aircraft Engine manufacturer make a triple spool engine like the Rolls-Royce RB211 Trent, they were the first bleed air turbine cooling turbojet cause I have seen possibly from you
How's the pt6 going updates please
I believe that the Russians designed and built a three-spool, high bypass turbofan some years ago. And, of course, the Turbo Union RB199 engine, which powered the Panavia Tornado, had three spools.
@@grahamj9101 well I guess our Rolls-Royce RB211 high bypass originally made for the Lockheed TriStar and when fitted to the Qantas B747 had a fuel saving of 1 million lb of fuel per aircraft had to be investigated
The RR RB 199 engine I have a fourth stage turbine bought e-bay
Interesting comment thank you for your reply
£ meant not lb sorry
Voice to text, I should have read it first
Is there possibility to cool that cooling air between compressor and turbine blade?
Don't light the combustors. 😅
Seriously though, it'd reduce output power.
Air film bleed cooling, along with coating and internal cooling for best results. Even if it's all ceramic.
@@BerndFelsche I am talking about that airflow which is used for blades cooling only. Not reducing the temperature of exhaust gases of the burner.
@@BerndFelsche the idea is to make that bleeding air cooler in order to reduce the mass flow of it.
Such a small amount is used compared to total mass flow, the expense and complication would not be worth the bother. Also, when you want to carry heat away from something that is over 1500F, and you use air at even 500F, it's going to work just fine.
There’s no point because when we design an engine, you can chose from where you want the cooling air with temps varying from T1 to T2.8ish. If you want cooler air, just take from a station closer to the inlet. Plus you dont want to reduce the temp in the gas path with really cold air because that means that less work can be produced by the next turbine stage.
How the fuck are they manufactured? Amazing things.
I love Pink Floyd
Tell us you favorite song and why. OK, top three.
@@AgentJayZ That’s impossible.. But I really like Lucifer the cat , Corporal Clegg and the entire Wall album , although I love The Dark Side of the Moon and Animals. Love it all
Why..? I had a cool Siamese cat when I was a kid , my dad was wounded in WWII and the first time I drank alcohol I was listening to The Wall.
@@AgentJayZ i’m a hardline Echoes enjoyer
🥡
❤