Hey there, love your videos. I wanted to comment here on what I think is a critical phenomenon in helping people understand compressor rotor AOA and why the vectors work out the way they do. You have always mentioned AOA as a vector of 2 factors, rotor RPM and the velocity of air through the compressor. As you've said, the rotor blade angles are optimized for full power operation, so at lower RPMs we need the help of bleed valves and variable stator vanes to change both the speed and angle of air introduced to the rotor blade to stay within a proper AOA. But what is really driving this is that as we decrease RPM, the decrease in velocity of the air through the compressor is not linear, if it was, then we wouldn't need bleed valves and VSVs as the AOA would stay constant. This is something you eluded to and I know you understand but in my humble opinion needs to be explained further. For example, a jet engine turning at 50% RPM is not going to have 50% of max velocity through the compressor, it will be much lower. Again, you did mention something about this on your compressor video, but I think this needs to be hammered on more as this non-linear relationship is what drives all these vectors to be so much more complex.
Jay I thought your compressor stall video was very insiteful with a tone of info that was explained so that even an idiot could understand it, and as an idiot I can say that from first hand. A huge thank you for all the effort and work you put into your video's for us. Wish I could give more than just 1 thumbs up.
Great explanation ! I’m in Avionics program, however Im really interested in Jet Engine and your videos are giving much knowledge...keep up the great work sir!
I chuckle with the banter. I understand engineering quite well and I understand people who just run with common sense. Bridging the Gap with the language is difficult cuz we see it from two different ways😊
Love the drama that goes with a 'heated' discussion! I learned a bit more, as I usually do viewing your efforts here on You Tube., so thanks as always for your efforts. This video got Graham J AND Pink commenting; it is good to hear from both of them. Cheers Jay!! DD
I wonder if using an example for stall like when people put their hand out the window while driving (I don't recommend this btw) into the wind and as long as its relatively knife edged it cleaves through the wind with little resistance, whereas if you increase the "angle of attack" as we're referencing, it gets more and more difficult to keep your hand from being blown back. If the hand flattens out against the wind it is pushed back and encounters what one might call a stall. This gives people a more direct example they can put in their heads I think. But that's just me. Again, I might be misunderstanding things. Really enjoy the videos AgentJayZ. Learning a lot. :)
No. The pump rotates at a certain speed and it pumps a certain volume per rotation. The pressure is not important. And the fuel control is not as advanced as you might think. In most cases it is hydraulics or Fly by Wire. And not the computer Fly by Wire. Fly by real wires.
Hello! I have a question for you. About the variable stator system - I see in your videos, especially the j79/lm1500, that the variable stators in the compressor are all linked together by mechanical arms that makes them move in synchronized harmony to their told position. All of which is connected to a bracket and powered by one single hydraulic piston. Is there allot of force needed to move all the stators? There are apparently many stators.. And I guess that just the mechanical structure, with all its parts, offers allot of resistance too. Anyway, I really what to thank you for the effort on makeing these videos! It have certainly given me countless hours of interest, knowledge and joy! My interest in turbine engines are really true! My father and my brother are both pilots and learn me allot about that. So it feels great to be able to learn them a thing or two about the machines they are handling, very much thanks to you!
So glad to finally see the compressor stall video and this follow up. In the original video you said a compressor stall occurred when the compressor accelerates too quickly, faster than the air can accelerate, so the critical angle of the blades is exceeded. I wondered if combustor and diffuser pressure were an issue, as well, with an over zealous application of fuel the flame gets rapidly bigger faster than the rotor would spin up. Does the air pressure on the diffuser exceed the dynamic pressure from the compressor in these cases and stalls the compressor from back to front? If not, I would guess resistance from stalling would be a real advantage to fixed rpm engines. Another question, when these engine stall, which stage of a compressor stalls first? Still so many questions about this. Do centrifugal compressors stall? What damage occurs to an engine during a stall?
" I wondered if combustor and diffuser pressure were an issue, as well, with an over zealous application of fuel the flame gets rapidly bigger faster than the rotor would spin up." In this scenario the issue will be combustion temperature, not pressure. The lack of cooling air from the compressor will cause the combustion output to exceed the thermal limits of the turbine nozzles.
One thing that has got me confused is how you mentioned compressor inlet temp reflects air density + the compressor RPM tells the VSV what position it should be in. My Question is Wouldn't air at -20 degrees Celsius at ground level during a test in winter be at a different density to say -20 degree at 30,000 feet in the air (hypothetical values) due to the change in altitude pressure affecting how dense the air can get? Would you know of a book/source that explains this a bit more in detail??
Maybe I didn't include that the VSV controller also measures ambient air pressure. My video called Books! will suggest a few that include this subject.
J, it seems that everything that operates in air or a gas requires LAMINAR FLOW to function correctly. Which means the molecules are moving in unison and in a smooth path parallel to each other. This applies to airfoils like wings, rotors, props, and axial compressor elements. LF is also required for orifice meters used for measuring NG flow rates. But when the flow becomes TURBULENT the molecules go into disarray and move in non uniform patterns. That causes airfoils to stall and NG meters to read incorrectly. I believe turbine engine designers strive to maintain uniform laminar flow at all points in an engine which results in smooth efficient power delivery. The variable angle stator guide vanes in a compressor is a way of optimizing laminar flow in variable air densities to get that result. Bob
The combustion area and the afterburner flame holder are structures engineered specifically to maintain turbulent flow in order to ensure reliable ignition of all the fuel air mixture. Otherwise yes. The loss of laminar flow over the convex surface of the compressor airfoils is the definition of a compressor stall.
Ok im good to go with that. Combustion chambers do work best with turbulence whether in turbine or recip engines. Since fuel and air need to be well mixed for good burn. But was trying to give a general sense of the process without getting in too deep. While hoping to be mostly correct. Bob.
Why is the VSV posistion not determined by inlet air pressure too? I would guess that pressure is more indicative of the density of the air than temperature? Especially in aircraft the pressure is going to change a lot.
Q: at 15:50 there seems to be several mm of free play / lash in the rod end of the hydraulic cylinder of the actuator for the vanes, is that what i am seeing; it seems amount of lash would be too much to be within tolerance. I can only guess that the air rushing across/thru the vanes are always applying a moment that keeps the linkages in compression or tension and never from one to the other... but then i saw that rod end linkage wiggle....
Joe Kozak I reckon it is a closed loop system and it doesn't matter what the hydraulic cylinder does because the actual position of the thing that moves the vains is read by the computer. and not the hydraulic cyclinder position
Joe Kozak Also there needs to be some wiggle because the arm the hydraulic cylinder engaged on is on a pivet so it moves up and down on an arc as the cylinder moves out and in
good point about the pivot and arc! i totally missed that! So there must be some special bearing in there that takes up the difference... surprised they didn't just make a secondary linkage there...
We are talking about different bands, I didn't know D:Ream, but after a quick RUclips check I think Dare are much better, even if they have never achieved a top one like D:Ream.
Re: angle of attack. You also get some interesting effects due to rate of climb in airplanes. Hopefully in a turbine engine the air will always be entering the compressor section close to perfectly axially. If you want to go into the details of airplanes stalling, you usually don't lose lift at the point of stalling, you just have a massive jump in drag, and lose flow over control surfaces.
Thanks for the J79 memories - in my old airplane-fixin' school (Colorado Aero Tech) we had as our teaching engine a civilian variant of the J79, the free turbine driven aft-fan version called the CJ805-23. It was used on the Convair 990. I'm sure you've heard of it but have you ever come across one in your travels?
Great vid and on point as usual. With VSV and bleed valves basically doing the same thing, preventing stall, why would VSV be used in a industrial envorment? Seems very complicated and costly for steady-state running. In a aircraft, do VSV react quicker to prevent stall than bleed valves?
When you say industrial , do you mean power generation? If so we do not have vigv or vsv here because we operate at one specific speed. As to your comment on vsv vs bleed valves; I believe either VSV or VIGV are preferable during constant varying rotational speeds than bleed valves. Because with bleed valves you loose total compression, I believe. That is why we (power industry) start with bleed valves open, because we want increased flow without cavitation, we don't care about compression at startup. IGV's stated as closed are not closed, they are just limiting. Once an industrial turbine is close to speed the IGV'S can be opened (80%ish) and bleed valves closed. It is more of a cavitation and stall issue during start up while the compressor airfoils are not in proper attack angle.... Once the air is "walked" in a forward motion and the rotational speed is near max we close bleeds and open IGV's. Spinning up can take up to 45 minutes to ease thermal issues. The airfoils are not in there optimum angle and creating Bernoulli's vacuum. You can stall! I saw a unit trip with IGV failure and it rumbled the ceiling tiles out of the ceiling with the air changing speed and not being able to go anywhere.
Question could it be possible to eliminate the need of stators by arranging the compressor blades in a corkscrew pattern? Air is a fluid it should get pushed back instead trapped in a tornado type pattern right?
nice video as always, i do have one question, but it doesnt really have anything to do with a compressor stall, but could you do a video on how the high pressure recoup works in an gas turbine engine. there seems to be very little known about it on the internet.
Long time lurker here, so far i have enjoyed it all. I have not seen all your videos or read all the comments but I did read as many as I had time for and I don't believe my questions have been asked. 1. why is the FCOC on the J79 rendered inoperable when it is demilitarized? I have heard of firearms and destructive devices being cut but not anything else. Is it considered a proprietary technology or is the engine itself not available for civilian use, so key components are destroyed? I also have another question but I need to find the video. Edit: question 2. In the RR Tyne test prep video at 1 :55 a fella pulls a cable up by the inlet, can you explain what that was for? Also: If you have time to cover the chemical dispersion system for the chemtrails lol thanks man.
You got it right: Stall is a function of angle of attack not velocity. No matter the speed (subsonic) stall will always happen at the same angle of attack, for a given airfoil.
AgentJayZ okay this may be silly and end up in a wtfq video but looking at the footage of the vsv and vigv it looks like the mechanism would move them in opposite directions?? is that correct and if so why?? in any case great job mate i really enjoy your videos its great to see some one explaining these awesome engines in such clear and concise detial if i ever meet meet ya ill buy ya a drink cheers and keep up the good work
Number 9 to #1....uhm there is an engine behind the man, I would conclude that this video/channel is mainly about the engine and not about how to fly. Their are other videos on that subject on RUclips. Well done on the explanation sir....keep up the good work.
Hello AgentJayZ my name is Tobias 23 Years and live in Holland have an Question! Do the compressor and stator work together to compress air? so you get that super hard scream? What is caused by air that gives an explosion?because I write a song about it
Hi. Didn't evan expect that you answer to me. Thanks. :-D I' agree. Smoke probably would be to abrasive for blades or something else but I' think at stuff like dry ice or smoke they used in the wind tunnels, from long pipes for measuring coefficient of drag Thanks anyway
A wing stalls at the same angle of attack no matter the speed. Between 15-20 degrees. In an airplane where air is blown over the wing by the engine, such as a piper Seminole, and most prop planes, the wing will stall at a lower indicated airspeed at a high power setting because the propeller is moving more air over the wing. However, the critical angle of attack doesn’t change. Private single/multi complex high performance. Cirrus / Cessna / piper
chanbaggett555 The problem is that in the compressor the angle of attack lowers with higher airspeed and rises with higher rpm. Pretty weird compared to a plane I guess but I think that is what he means
As long as compressibility plays no role (up to around maybe Mach 0.3) that is true. At higher Mach numbers, where compressibility becomes an issue, stall occurs at lower angles of attack, some times as low as 10º. I would argue that compressor blades are well into the high-subsonic region, and will stall at lower angles of attack than typical airplanes. The (compared to aircraft wings) relatively small blade-nose-radius will also facilitate an earlier stall. When the stagnation points moves too far to the underside, the nose itself may cause flow separation.
pinkdispatcher Compressor blades are pretty much just a half a bee's dick under transsonic speeds for the incoming air in flight conditions and the compressor blades move at.. well lets say we have 10krpm, so just round to 160 per second at 0.5m diameter (outer diameter of the blades) thats 0.25 radius so 2*3.141*0.25=1.57m approx 1.6m soo 1.6m per rev and 160revs per second is 256m/s is 921kph. Pretty damn fast. But the shapes of the blades are somewhat optimised for a high airspeed a little bit like a supersonic jet has a different wingprofile than a slow stuntairplane
@@AgentJayZ Thank you. I was not sure if the low pressure and high pressure compressors experienced (not sure how to word it) different stall conditions.
If you see this i have a question if there is a videos about it let me know. The question is how do you move lift and transport the engines around? Thanks and have a good day.
There's a search feature on my channel page, to help find your answer in one or more of the hundreds of videos I have made. How about searching for "engine transport" Yeah. Try that one...
Several ways. Power turbine driving an electrical generator. Power turbine driving an aerodynamic load with a torquemeter on the shaft. Or we can measure pressure rise in the jet pipe with a measured choked nozzle at the exit.
@@AgentJayZ Excellent! I figured barring any physical load, SOMETHING (pressure or velocity) in the throughput could be measured. Thank you kind sir. Happy Holidays. Btw, someone sent me a video of a recent Community and Public Health Commitee meeting in Ottawa in regards to Covid. Speaking was Dr. Hopkinson (specialist in pathology including virology). I can’t post it here. But, you can google it if interested. Powerful commentary.
LOL..... The RUclips Certified mechanics and engineers making great efforts to take a bite out of your a$$. I am laughing while shaking my head at them...
Hi! Its not related to this video, but i think you might be interested. If you remember, a few years ago you did a giveaway of s bunsh of J79 blades, i got them. Recently i have come across a supply of old german army stock with several hundreds of brand new J79 blades, compressor as well as turbine and a complete assembly of all three turbines. If you are interested in them contact me and i will get you in contact. They sell them dirt cheap in original packaging.
So maybe airplane analogies are not the best way of explaining gas turbine engine stuff. Because the analogy breaks down exactly at the point where it gets interesting.
"Comprehension in context" used to be... used to be... part of common sense. "He used some words that I also use, therefore what he said MUST agree with when I use those words". Ahhhrgh.
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Great job. I really like this format where a subject is addressed with level of detail followed by a Q&A.
Hey there, love your videos. I wanted to comment here on what I think is a critical phenomenon in helping people understand compressor rotor AOA and why the vectors work out the way they do. You have always mentioned AOA as a vector of 2 factors, rotor RPM and the velocity of air through the compressor. As you've said, the rotor blade angles are optimized for full power operation, so at lower RPMs we need the help of bleed valves and variable stator vanes to change both the speed and angle of air introduced to the rotor blade to stay within a proper AOA. But what is really driving this is that as we decrease RPM, the decrease in velocity of the air through the compressor is not linear, if it was, then we wouldn't need bleed valves and VSVs as the AOA would stay constant. This is something you eluded to and I know you understand but in my humble opinion needs to be explained further. For example, a jet engine turning at 50% RPM is not going to have 50% of max velocity through the compressor, it will be much lower. Again, you did mention something about this on your compressor video, but I think this needs to be hammered on more as this non-linear relationship is what drives all these vectors to be so much more complex.
Jay I thought your compressor stall video was very insiteful with a tone of info that was explained so that even an idiot could understand it, and as an idiot I can say that from first hand. A huge thank you for all the effort and work you put into your video's for us. Wish I could give more than just 1 thumbs up.
Great explanation ! I’m in Avionics program, however Im really interested in Jet Engine and your videos are giving much knowledge...keep up the great work sir!
I chuckle with the banter. I understand engineering quite well and I understand people who just run with common sense. Bridging the Gap with the language is difficult cuz we see it from two different ways😊
Jay you have a wonderful polite way of putting your point across
Most awesome use of a protractor ever.
Flying on the back of the drag curve...Now I`m back to the video for my information needs
Love the drama that goes with a 'heated' discussion! I learned a bit more, as I usually do viewing your efforts here on You Tube., so thanks as always for your efforts. This video got Graham J AND Pink commenting; it is good to hear from both of them. Cheers Jay!!
DD
PS: Coincidentally, I was 'Like' number 400 for this video! That's a lot of 'Likes'! Who were the 2 'Dicklikes'? I didn't misspell that.
I wonder if using an example for stall like when people put their hand out the window while driving (I don't recommend this btw) into the wind and as long as its relatively knife edged it cleaves through the wind with little resistance, whereas if you increase the "angle of attack" as we're referencing, it gets more and more difficult to keep your hand from being blown back. If the hand flattens out against the wind it is pushed back and encounters what one might call a stall. This gives people a more direct example they can put in their heads I think. But that's just me. Again, I might be misunderstanding things.
Really enjoy the videos AgentJayZ. Learning a lot. :)
Great video. How does altitude affect the fueling of the engine? Is combustion chamber pressure fed in to the fuel control?
No. The pump rotates at a certain speed and it pumps a certain volume per rotation. The pressure is not important. And the fuel control is not as advanced as you might think. In most cases it is hydraulics or Fly by Wire. And not the computer Fly by Wire. Fly by real wires.
Hello! I have a question for you. About the variable stator system - I see in your videos, especially the j79/lm1500, that the variable stators in the compressor are all linked together by mechanical arms that makes them move in synchronized harmony to their told position. All of which is connected to a bracket and powered by one single hydraulic piston. Is there allot of force needed to move all the stators? There are apparently many stators.. And I guess that just the mechanical structure, with all its parts, offers allot of resistance too.
Anyway, I really what to thank you for the effort on makeing these videos! It have certainly given me countless hours of interest, knowledge and joy! My interest in turbine engines are really true! My father and my brother are both pilots and learn me allot about that. So it feels great to be able to learn them a thing or two about the machines they are handling, very much thanks to you!
Can a centrifugal compressor stall?
So glad to finally see the compressor stall video and this follow up. In the original video you said a compressor stall occurred when the compressor accelerates too quickly, faster than the air can accelerate, so the critical angle of the blades is exceeded. I wondered if combustor and diffuser pressure were an issue, as well, with an over zealous application of fuel the flame gets rapidly bigger faster than the rotor would spin up. Does the air pressure on the diffuser exceed the dynamic pressure from the compressor in these cases and stalls the compressor from back to front? If not, I would guess resistance from stalling would be a real advantage to fixed rpm engines. Another question, when these engine stall, which stage of a compressor stalls first? Still so many questions about this. Do centrifugal compressors stall? What damage occurs to an engine during a stall?
" I wondered if combustor and diffuser pressure were an issue, as well, with an over zealous application of fuel the flame gets rapidly bigger faster than the rotor would spin up."
In this scenario the issue will be combustion temperature, not pressure. The lack of cooling air from the compressor will cause the combustion output to exceed the thermal limits of the turbine nozzles.
randomRUclipsR That was definitely an issue for the Me 262 engines.
One thing that has got me confused is how you mentioned compressor inlet temp reflects air density + the compressor RPM tells the VSV what position it should be in. My Question is Wouldn't air at -20 degrees Celsius at ground level during a test in winter be at a different density to say -20 degree at 30,000 feet in the air (hypothetical values) due to the change in altitude pressure affecting how dense the air can get? Would you know of a book/source that explains this a bit more in detail??
Maybe I didn't include that the VSV controller also measures ambient air pressure. My video called Books! will suggest a few that include this subject.
@@AgentJayZ thanks for the reply, I dont think you did mention it, there was only quick statement about temperature reflecting density
J, it seems that everything that operates in air or a gas requires LAMINAR FLOW to function correctly. Which means the molecules are moving in unison and in a smooth path parallel to each other. This applies to airfoils like wings, rotors, props, and axial compressor elements. LF is also required for orifice meters used for measuring NG flow rates. But when the flow becomes TURBULENT the molecules go into disarray and move in non uniform patterns. That causes airfoils to stall and NG meters to read incorrectly. I believe turbine engine designers strive to maintain uniform laminar flow at all points in an engine which results in smooth efficient power delivery. The variable angle stator guide vanes in a compressor is a way of optimizing laminar flow in variable air densities to get that result. Bob
The combustion area and the afterburner flame holder are structures engineered specifically to maintain turbulent flow in order to ensure reliable ignition of all the fuel air mixture.
Otherwise yes. The loss of laminar flow over the convex surface of the compressor airfoils is the definition of a compressor stall.
Ok im good to go with that. Combustion chambers do work best with turbulence whether in turbine or recip engines. Since fuel and air need to be well mixed for good burn. But was trying to give a general sense of the process without getting in too deep. While hoping to be mostly correct. Bob.
I want equations. :D
Why is the VSV posistion not determined by inlet air pressure too? I would guess that pressure is more indicative of the density of the air than temperature? Especially in aircraft the pressure is going to change a lot.
corrected N2 is what sets the vsv settings
Q: at 15:50 there seems to be several mm of free play / lash in the rod end of the hydraulic cylinder of the actuator for the vanes, is that what i am seeing; it seems amount of lash would be too much to be within tolerance. I can only guess that the air rushing across/thru the vanes are always applying a moment that keeps the linkages in compression or tension and never from one to the other... but then i saw that rod end linkage wiggle....
Joe Kozak I reckon it is a closed loop system and it doesn't matter what the hydraulic cylinder does because the actual position of the thing that moves the vains is read by the computer. and not the hydraulic cyclinder position
Joe Kozak Also there needs to be some wiggle because the arm the hydraulic cylinder engaged on is on a pivet so it moves up and down on an arc as the cylinder moves out and in
good point about the pivot and arc! i totally missed that! So there must be some special bearing in there that takes up the difference... surprised they didn't just make a secondary linkage there...
Greatest program
Hi! You are by far my favorite agent! Love your videos. Where can I ask uou a question? Best regards from Norway
Don't forget that Brian Cox was also the keyboard player in the band Dare. Isn't he cool?
Things can only get better ..... D: Ream was the band - but he didn't play on that track
I went to see his road show last year.
We are talking about different bands, I didn't know D:Ream, but after a quick RUclips check I think Dare are much better, even if they have never achieved a top one like D:Ream.
Re: angle of attack. You also get some interesting effects due to rate of climb in airplanes. Hopefully in a turbine engine the air will always be entering the compressor section close to perfectly axially.
If you want to go into the details of airplanes stalling, you usually don't lose lift at the point of stalling, you just have a massive jump in drag, and lose flow over control surfaces.
Thanks for the J79 memories - in my old airplane-fixin' school (Colorado Aero Tech) we had as our teaching engine a civilian variant of the J79, the free turbine driven aft-fan version called the CJ805-23. It was used on the Convair 990. I'm sure you've heard of it but have you ever come across one in your travels?
That had an aft fan if I recall
What about the bleed off valve that deals with compressor stall? Briefly talk about it, at at stage of the compressor is it installed and why?
The bleed valve method of preventing compressor stall is discussed in the video that precedes this one. It is called Jet Tech: Compressor Stall.
Great vid and on point as usual.
With VSV and bleed valves basically doing the same thing, preventing stall, why would VSV be used in a industrial envorment? Seems very complicated and costly for steady-state running. In a aircraft, do VSV react quicker to prevent stall than bleed valves?
When you say industrial , do you mean power generation? If so we do not have vigv or vsv here because we operate at one specific speed. As to your comment on vsv vs bleed valves; I believe either VSV or VIGV are preferable during constant varying rotational speeds than bleed valves. Because with bleed valves you loose total compression, I believe.
That is why we (power industry) start with bleed valves open, because we want increased flow without cavitation, we don't care about compression at startup. IGV's stated as closed are not closed, they are just limiting. Once an industrial turbine is close to speed the IGV'S can be opened (80%ish) and bleed valves closed. It is more of a cavitation and stall issue during start up while the compressor airfoils are not in proper attack angle.... Once the air is "walked" in a forward motion and the rotational speed is near max we close bleeds and open IGV's.
Spinning up can take up to 45 minutes to ease thermal issues. The airfoils are not in there optimum angle and creating Bernoulli's vacuum. You can stall!
I saw a unit trip with IGV failure and it rumbled the ceiling tiles out of the ceiling with the air changing speed and not being able to go anywhere.
Question could it be possible to eliminate the need of stators by arranging the compressor blades in a corkscrew pattern? Air is a fluid it should get pushed back instead trapped in a tornado type pattern right?
That would be a centrifugal compressor.
example: Pratt and Whitney PT6
Good job.
Can't please everyone all the time.
Keep up the good work.
nice video as always, i do have one question, but it doesnt really have anything to do with a compressor stall, but could you do a video on how the high pressure recoup works in an gas turbine engine. there seems to be very little known about it on the internet.
+Wouter Van Oerle
I don't know what that means.
Long time lurker here, so far i have enjoyed it all. I have not seen all your videos or read all the comments but I did read as many as I had time for and I don't believe my questions have been asked.
1. why is the FCOC on the J79 rendered inoperable when it is demilitarized? I have heard of firearms and destructive devices being cut but not anything else. Is it considered a proprietary technology or is the engine itself not available for civilian use, so key components are destroyed? I also have another question but I need to find the video.
Edit: question 2. In the RR Tyne test prep video at 1 :55 a fella pulls a cable up by the inlet, can you explain what that was for?
Also: If you have time to cover the chemical dispersion system for the chemtrails lol thanks man.
You got it right: Stall is a function of angle of attack not velocity. No matter the speed (subsonic) stall will always happen at the same angle of attack, for a given airfoil.
Thanks once more for all the efforts.
Great video agent jayz,the j79 is a beautiful thing isn't it, thanks 😀
at 16:07 the rod end sure has a lot of visible "slop", no? good vids. btw, will not a stage stall cascade thru the remaining stages?
AgentJayZ okay this may be silly and end up in a wtfq video but looking at the footage of the vsv and vigv it looks like the mechanism would move them in opposite directions?? is that correct and if so why?? in any case great job mate i really enjoy your videos its great to see some one explaining these awesome engines in such clear and concise detial if i ever meet meet ya ill buy ya a drink cheers and keep up the good work
Look carefully at the links. Nothing is going backwards or opposite. VIGVs and VSVs track in the same direction.
Number 9 to #1....uhm there is an engine behind the man, I would conclude that this video/channel is mainly about the engine and not about how to fly. Their are other videos on that subject on RUclips. Well done on the explanation sir....keep up the good work.
Hello AgentJayZ my name is Tobias 23 Years and live in Holland have an Question! Do the compressor and stator work together to compress air?
so you get that super hard scream? What is caused by air that gives an explosion?because I write a song about it
Question: do you (while working on the engine) define it as Engine Trimming or do you word it differently??
LOL did you just use "Spaceballs" logic to explain compressors. LOL awesome.
+Pitch Lock
...when will it be now?
...soon.
Hi AgentJayZ.
Can you create some kind of smoke in front of the engine to see from how far engine pulls air at full throttle?
The books I recommend have nice diagrams of that.
When you take your car to be dyno tested, do you want some smoke going through it?
Hi.
Didn't evan expect that you answer to me. Thanks. :-D
I' agree. Smoke probably would be to abrasive for blades or something else but I' think at stuff like dry ice or smoke they used in the wind tunnels, from long pipes for measuring coefficient of drag
Thanks anyway
A wing stalls at the same angle of attack no matter the speed. Between 15-20 degrees.
In an airplane where air is blown over the wing by the engine, such as a piper Seminole, and most prop planes, the wing will stall at a lower indicated airspeed at a high power setting because the propeller is moving more air over the wing. However, the critical angle of attack doesn’t change.
Private single/multi complex high performance. Cirrus / Cessna / piper
I thought your compressor stall vid was thoughtful and well put together.
chanbaggett555 The problem is that in the compressor the angle of attack lowers with higher airspeed and rises with higher rpm. Pretty weird compared to a plane I guess but I think that is what he means
As long as compressibility plays no role (up to around maybe Mach 0.3) that is true. At higher Mach numbers, where compressibility becomes an issue, stall occurs at lower angles of attack, some times as low as 10º. I would argue that compressor blades are well into the high-subsonic region, and will stall at lower angles of attack than typical airplanes. The (compared to aircraft wings) relatively small blade-nose-radius will also facilitate an earlier stall. When the stagnation points moves too far to the underside, the nose itself may cause flow separation.
pinkdispatcher Compressor blades are pretty much just a half a bee's dick under transsonic speeds for the incoming air in flight conditions and the compressor blades move at.. well lets say we have 10krpm, so just round to 160 per second at 0.5m diameter (outer diameter of the blades) thats 0.25 radius so 2*3.141*0.25=1.57m approx 1.6m soo 1.6m per rev and 160revs per second is 256m/s is 921kph. Pretty damn fast. But the shapes of the blades are somewhat optimised for a high airspeed a little bit like a supersonic jet has a different wingprofile than a slow stuntairplane
pinkdispatcher provide your source.i would love to read about it
Would the information in both of you Compressor Stall videos apply equally to a High Bypass Turbofan engine?
It applies to all axial compressors.
@@AgentJayZ Thank you. I was not sure if the low pressure and high pressure compressors experienced (not sure how to word it) different stall conditions.
If you see this i have a question if there is a videos about it let me know. The question is how do you move lift and transport the engines around? Thanks and have a good day.
There's a search feature on my channel page, to help find your answer in one or more of the hundreds of videos I have made.
How about searching for "engine transport"
Yeah. Try that one...
How do you determine power? With an automobile, you have a dynamometer to use.
Several ways. Power turbine driving an electrical generator. Power turbine driving an aerodynamic load with a torquemeter on the shaft.
Or we can measure pressure rise in the jet pipe with a measured choked nozzle at the exit.
@@AgentJayZ Excellent! I figured barring any physical load, SOMETHING (pressure or velocity) in the throughput could be measured. Thank you kind sir. Happy Holidays. Btw, someone sent me a video of a recent Community and Public Health Commitee meeting in Ottawa in regards to Covid. Speaking was Dr. Hopkinson (specialist in pathology including virology). I can’t post it here. But, you can google it if interested. Powerful commentary.
If you had a free Ticket for a Jet flight, what Jet would you like to fly or have a ride in ? ( Any Jet ever made ) :)
I got the free ticket, New York and return .... on Concorde, back in 1995. it had the best airline food and a the vintage port .....
Someone trying to make the professor look bad..haha didn't work.. great job agent jayz..
LOL..... The RUclips Certified mechanics and engineers making great efforts to take a bite out of your a$$. I am laughing while shaking my head at them...
great vid once again!
What "The Power of Yaos" said. Great job!
True 👍
Hi!
Its not related to this video, but i think you might be interested. If you remember, a few years ago you did a giveaway of s bunsh of J79 blades, i got them. Recently i have come across a supply of old german army stock with several hundreds of brand new J79 blades, compressor as well as turbine and a complete assembly of all three turbines. If you are interested in them contact me and i will get you in contact. They sell them dirt cheap in original packaging.
Question #10...I concur.
OMG. The airplane people are going to go nutz because you have poked your finger into their dogma again.
Know it all pilots. Feed their warped heads through the compressor.
Are you actually an A&P mechanic and have your own repair shop....or are these jet engines all surplus and out of service toys for your hobby....??
+panther105
Are those my only two choices?
For your multiple choice question, I choose C, none of the above.
Aahhh.....You're a wizard..... That WAS going to be my third choice...
So maybe airplane analogies are not the best way of explaining gas turbine engine stuff. Because the analogy breaks down exactly at the point where it gets interesting.
"Comprehension in context" used to be... used to be... part of common sense. "He used some words that I also use, therefore what he said MUST agree with when I use those words". Ahhhrgh.
you are displaying those flags wrong.
Lol @ explanation of a timeline. Jesus wept.
first