Your work has inspired me to join the aviation industry. Just recently got my airframe license and about to wrap up my powerplant time. We just finished doing a mock inspection of a J34 in school. Thank you for your videos!
When our Unit converted from Recips to C-130E's in 1975 an Allison Rep gave a class and I remember him saying about over temp of TIT, that metal has a memory and never forgets.
This is the best explanation on turbine ITT, on ATRs we have to keep a watch out on ITT on Eng2 cause we use it as APU during ground operations when GPS is not available or A/C is required for commercial usage, when ITT hits near the cap due to tail wind bleed needs to be switched off immediately otherwise eng kablamo is to be expected.
It is interesting to note that the current king in terms of turbine inlet temperature is the PW F135 in the F-35 at 2260 K. At that temperature, about 70% of the oxygen in the combustors is burned, which is much higher than any other engine I've seen.
@@AgentJayZ Here is an article from the American Society of Mechanical Engineers discussing the F135 and its record breaking temperature tolerance: asmedigitalcollection.asme.org/memagazineselect/article/129/04/34/366970/Fahrenheit-3-600Everywhere-You-Look-the-Gas. With this and the other specs of the engine (overall pressure ratio, bypass ratio, thrust...) the thermodynamic cycle calculation can be made to determine a lot about its operation. I used a professional gas turbine analysis software (GasTurb) to do these calculations. The result is that about 70% of the oxygen in the combustor must be combusted in order to reach this temperature. Another very interesting result is that with the afterburner fully engaged, nearly all of the air (>90%) is burned (that includes the ~30% remaining in the core flow plus the bypass flow). This engine is quite a monster.
@@AgentJayZ i know you're probably not going to see this, but I want you to know that your videos have changed my life. Whenever im down, i come here to take my mind off of stuff. Thanks for that!
Jay, TGT on the Tyne 515 used to reach > 680*c on startup. Any higher than 700*c, shut the fuel off and abort the start. Normal TGT in the cruise is between 550*c to 600*c. Loved the comment on the bucket!
Today, 15th September 2020, is acknowledged as the 80th anniversary of the Battle of Britain here in the UK. As Churchill said, "Never in the field of conflict was so much owed by so many to so few." At this moment, I'm watching a TV programme showing the restoration of a WWII Spitfire that suffered a forced landing and, yesterday evening, I watched an extended programme about the Spitfire (and the Hurricane) and the people who flew them, included the women of the ATA who delivered them from the factories to the squadrons.
FWIW, designers are mostly interested in the TIT (turbine inlet temp) for maximising the cycle (thermodynamic) efficiency as well as preventing exceeding Tmax of the first row of blades (NGV's), while pilots are mostly interested in ITT and EGT, again primarily to prevent engine overheat (even though they're usually much different and lower than the TIT) but used more commonly because they're much more easily measured in the cooler downstream flow than in the hot zone immediately aft of the combustor. On the combustor pressure, the Brayton (turbine) cycle assumes heat addition (combustion) at constant pressure by design, (as opposed to say, the Otto (petrol) cycle, where heat is added at constant volume, ie when a piston is near TBC causing a spike in cylinder pressure) hence the nearly constant pressure in the combustion chamber. The small / gradual reduction in pressure shown in the diagram in the combustion chamber is actually mostly due to combustion loss (mostly turbulence needed for mixing the hot combusted air with the cooler dilution air, ensuring the working fluid entering the NGV is as uniform as possible). In a well designed machine, this is around 1% of the max combustion pressure.
AgentJayz, regarding the T56. Series 1, 2 and 2.5 T56 engine do in fact use TIT, however the series 3 and subsequent use TMT (turbine measured temperature) measured between stages 2 &3
before I retired we made f110 1st stage stators and F404 1st stators at Johnston Technology. A f110 had around 600 cooling holes on airfoils and inner and out bands. These all for creating a cooling film on part surface to minimize heat damage. I do have question for you. was ceramic coating on the blades of the original version of j79?
The original J79s most likely had no thermal barrier coatings. I have experience with the J79-8, -10, -11, -15, -17, and the -19. None of them had thermal barrier coatings anywhere, except the liners of the jet pipe on the afterburners.
To see the effect of an extreme case of turbine over temperature look for the video "Tractor Pull Accidents - Crash Encounters", at 0:56 it starts with flame leaving the exhausts under full power, at 1:03 turbine 1 explodes at 1:04 turbine 2 explodes. I guess they were used to diesel engines, no harm in over fuelling !
Auto generated captions have proven to be so inaccurate as to be misleading, and only add confusion. Every time I have tried them, I disapprove of the content. Sorry, the YT algorithms are not up to the job.
That damaged blade (at approx 15 minutes into the video) is so cool! Do you have any similar ones you'd be willing to part with? (for a fee, of course) Love the videos, they're always very informative and interesting.
Of course! I would love to give you something, and send it you completely free! And what would you do for me in return? Nothing? Hmmm. Let me think on that a bit.
@@AgentJayZ no worries - I'm sure you get all sorts of grifters and beggars on the page trying to get free stuff. It must be exhausting. I'll have a poke around on the channel and see if I can't find the aforementioned vidjayos.
Dear Mr Z, not sure if you're taking questions anymore and you may have answered this in the past but I figured I should ask anyway as I cant find much online or on your channel. My question is about inertial separators. I know they are supposed to eject debris from the engine (??? I think ???) but I have no idea what the actual mechanism looks like. I'm also not sure if the separators are aircraft specific or engine specific. Thanks! p.s. your videos are awesome
Inertial particle separators are used on the intakes of some helicopter engines. They are discussed in the introductory text books I recommend in my video called "Books!"
AJZ - I always thought a demonstration of this was simply to pop out a torch. Seeing how the flame shoots out and how faster super heated flames are used to cut metal.
"Gas producer" seems unusual, I mostly hear them called "gas generator", but whatever. The Quest Kodiac is sort of a better, more modern and slightly smaller Cessna Caravan. They are easy to mix up: single turboprop, fixed gear, strut-braced high wing. And here's some pronunciation guide for the German inventor: "Hunns fonn O-hine".
@@DeepCZero3, @Dino Alberini, Yes, thank you, I know what it *is*. I was referring to AgentJayZ using the unusual word "gas producer", instead of the more common "gas generator".
Hello AgentJayZ I was wondering if you ever looked at the skylon spaceplane from reaction engines, if you have what do you think about the applications of the precooler in jet engines especially turbofans to achieve higher speed?
The Skylon precooler is designed for cooling the air which becomes heated during ram inlet compression when the inlet is traveling above mach 5 or so. Since even fighter jet turbofans can barely get almost to mach 2.. a precooler on their inlet would be as useful as drag chutes on a golf cart.
I have no idea what the limits are on a PT6 , but that question sounds more like the pilot is using that turbine temp as a setting to maintain a proper climb out or cruise airspeed.
interesting, I imagine the blades are glowing hot when in normal operation at that temperature. Are there not composite type materials that could be used that can withstand higher temperatures? I imagine not or it would already be used!
If any of AgentJayZ's subscribers wish to see an ex-Concorde Olympus 593 running, then go to Adrian Bennett's Jetpower.co.uk RU-vid channel. He ran the engine yesterday (Sunday) afternoon and broadcast it live.
AgentJayZ that’s awesome. After many many years of ongoing training in the car business. Computer based and hands on. I think it would have been cool to have a guru that actually does the work you’re learning to look at on a regular basis.
@@AgentJayZ Now if they'd give proper attribution, or better yet, proper "consideration" for your hard work for a class you're effectively helping to teach "for free"...
All engines work "best" and economy wise at highest safe temp. Diesel's, gas, turbines and nuclear higher is best. Only electric which are actually motors work best at cooler temps. Of course, the human engine, well you know that answer!
It's the basic thermodynamics of a heat engine. The higher the top temperature of the cycle and the higher the pressure, the greater is the thermal efficiency.
OK... jet fuel max temp around 3800°F or 2100°C... (1 bar, 68°F, 20°C initial conditions). I'm guessing modern vented ceramic coated blades & nozzles might be able to sustain half that (?¿?)... lots of development room left, eh jZ? PS: itt of 740°C is 1364°F
The Patreon channel is a separate project, and contains material that the general audience finds boring. I'm not interested in dealing with them. The people interested in the work I do on turbine engines realize that for 5 bucks a month, they get a half dozen highly detailed videos, without any commercials. Also on RU-vid, I am lucky to have a 90 to 98% like to dislike ratio. On Patreon, it is always 100%, so I must be reaching the right people. I will continue making YT vids, and continue with the Patreon effort.
Good day AgentJayZ. How does a pilot reduce the ITT when operating the aircraft? Does he reduce the air flow or enrich the mixture? Possible reduce power? Thank you for an interesting video.
Reduce ITT by reducing fuel flow. There is no way to control airflow except by changing rpm, which is a result of power level, which is a result of fuel flow.
May I just share this thought on the nineteenth anniversary of 9/11? A short while ago I was watching a documentary on TV here in the UK, which disputed both the official explanation of the collapse of the towers and the conspiracy theories. I was suddenly and forcibly reminded that my daughter stood on the observation deck of the south tower on 8th September 2001, before flying back to the UK the following day. Her original plan had been to have the following week in New York.
I have a question. I been watching some aircraft vids and I noticed that when sitting infront of the engine you could here a sort of low tone buzzing/huming tone. Could explain what that is? I am quite curious about it.
Is it possible to run engines hotter than originally specified if the turbine blades are ceramic-coated like the ones you've shown a few times? Or is it just used to increase the safety margin?
I like to think of the coatings as extra protection from thermal transients. As we have seen form our industrial engines, if you run the TBC coated blades at "stock" temperatures, they last basically forever. The user can do whatever they want, and some are interested in greater performance by running hotter. That's guesswork, with a very expensive machine...
Trying to work out some energy calculations. For a J79, do you know the temperature of the air just after the last compressor stage? Pressure there is about 200psi, right?
I'm currently studying mechanical engeneering in Italy and I don't know much about jet engines (yet), but after a compression at 218psi (15bar) temperature could be around 700K (426,85 °C). These are all theoretical data from my exercises. My guess is that in reality both pressure and temperature are a bit lower due to energy losses. I hope it helps
Wasn't there a Soviet fighter jet that could do Mach 3 ... for two minutes, and then required new engines? Basically same as overheating a piston engine to the point of the head gaskets failing, but at least they'd hopefully shoot down an American bomber and maybe have enough left of the turbines to limp back to base or at least friendly territory. Fake edit (I looked it up before posting): MiG-31! Quoth Wikipedia: "was normally limited to Mach 2.83, but it could reach a maximum speed of Mach 3.2 or more with the risk of engine damage." I.e., those turbine blades aren't coming home. Also apparently the skin starts to melt around max engine RPM as well, especially at low altitudes where the air is thicker, up where there's relatively little air to compress (supersonic heating is from compressing the air, not friction), EGT was the limiting factor.
MIG25, it was an interceptor rather than a fighter, essentially a drag racer with wings. The engines were very low pressure ratio turbojets. In the 90's it was possible to get a flight in one of these to the edge of space, they would accelerate through the atmosphere till the air ran out and follow a ballistic trajectory out of the atmosphere.
@@ValExperimenter That's an overstatement. It could do a zoom (ballistic) climb to about 200,000 ft (about 61 km) but that is still well within the atmosphere. The accepted definition of the edge of space is the Karman line at 100 km.
@@ASJC27 No problem I mix up feet and meters sometime I had the figure 115000 in my head. but there is certainly not enough atmosphere to run a turbojet up there.
Does the airflow get reversed as it travels through the combustion chamber/hot section of this PT6 engine? (Looks like it in the diagram) And what are the advantages of this? (If so)
Sir Special Agent JayZed, In the early days of turboJets or Low Bypass Turbines, the flight crew (engineer) would turn on water injection during takeoff (The old films of B-52's doing MTI would turn the sky black with soot) Was this done to increase thrust due to greater air density with water injection, or did this allow for the burners to run a hotter burner temperature as the water would evaporate and cool the gas temp coming off the gas generator? Also, where were the water injectors placed inside the turbine? Pre Compressor, Pre Burner, Pre gas generator, Pre Power Turbine? Thank you kind sir.
It was primarily to allow burning of more fuel while keeping the temperature within the turbine's limit. It had a secondary effect of slightly increasing mass flow.
@@AgentJayZ 16 gigs of older DDR3 1866mhz RAM, more HDMI cables than I can shake a stick at. Wish I still had some old kitschy stuff like 10base2 T connectors or something.
It's a legacy device with instant random access, immunity to malware, zero energy usage, and infinite backwards compatibility. It is physical data storage, so the medium does have a lifespan, but can typically run error free for over a hundred years.
Think advanced nickel alloys, with advanced casting methods (more uniform grain or single crystal), with really expensive Thermal Barrier Coating formula
@@alkooj There are some form of composite blades possible I think. The engine in f-35 has turbine inlet temperature around 2000C°. If I remember correctly the turbine blades in that engine aren't made of metal.
So basically if you want to see the good stuff you have to pay will what if I can’t afford to pay because I have kids to feed I was a faithful sub but not no more
Your RU-vid subscription is unaffected. The RU-vid content will always be free to enjoy by everybody. You can always choose to cancel your free subscription, if you want.
