Twin Shaft Turbine Engine Bearings

[@Evo2Raid]

I would like to say (Thank You) for all your time and effort to bring this amazing series for all of us to learn from.

[@Mentaculus42]

There seems to be significant variations on the placement location and configuration of the bearings in multi shaft turbofan engines depending upon which engine. Thank you for motivating me to go down that rabbit hole.

[@arthurcpiazzi]

Once upon a time, you were in favor of protecting mesh. Love your videos man, congratz

[@thedave7760]

Thanks man. I have watched about 5 of your videos tonight and have learnt a lot of things that I have been curoius about for many years. Much appreciated.

[@BigBoy4005]

Very well illustrated. And thanks for the recommendation of that book "The Jet Engine". I go nuts when i see something that interests me and I don't know exactly how it works. Your videos answer many questions.

[@nohandle1]

Always wondered about the bearing arrangement on twin shaft machines! Thanks for this

[@paqx3534]

Thank you! I can't beleive I got all the way through propulsion 1 without ever considering, mechanically, how X amount of thrust got transferred from the front fan to the airframe. Also seeing the way the shafts were braced was really enlightening, I need to take machine design and get a look a that stuff analytically

[@kneecaps2000]

Excellent video, I enjoy seeing the mechanical details that you do not see anywhere else!

[@nodariel]

I giggled at the thrust here label. Awesome video and nice diagrams.

[@knocknwalk]

Beautiful video of exactly the details I wanted to know about. Thanks for making it.

[@gobbagpete]

Thank you for this video. As you said yourself, most videos, animations and articles leave more questions than answers but you have demystified it.

[@Jigme85]

Heya AgentJayZ, I've been following your channel for a while now, I really wish this stuff would've been around when I started studying Aero.Eng., would have saved me a lot LOT of looong nights sitting in front of crazy diagrams trying to figure out how Gas Turbines actually work in detail.... but I still enjoy watching this channel a lot, so THANK YOU!

[@damio]

nice video as usual. nice because it is hard to find someone that takes the time to explain such interesting things!!! thanks!

[@WasimAkhtaraircraftengineer]

as you said that those videos are all nice and cool but no complex details like this one. Thank you

[@migueldenovi5873]

I could not be more pleased with this video. Thanks

[@AgentJayZ]

Some engines use variable stators and others use compressor bleed valves to limit the airflow through the compressor at low rpms to avoid a stall. Aerodynamic refinements and advances in materials, as well as inlet design has helped a bit over the years, but turbofans are much quieter than turbojets because the exhaust is expelled at a much lower velocity. What makes them more efficient also makes them quieter.

[@AgentJayZ]

Both turn the same way in this engine. The axial force on each shaft is the sum of the compressor pulling it forward minus the turbine pulling it backward. These values vary with aircraft speed, engine rpm, and fuel flow to the combustor. Often these engines have a "balance chamber" which is a cavity behind the compressor last stage disk fed with compressor discharge air to push the whole rotor assembly forward, balancing against the rearward pull of the turbine.

[@xenocideac]

Yeah! Muscles glasses in jet-tech form! I'm american and I'm really starting to appreciate Canadian things lately. My three favorite Canadian things: How It's Made, Epic Mealtime, and AgentJayZ. My dad's a pilot so I've grown up fascinated by jet engines and you have helped me immensely in my understanding of how they work. I really appreciate it and keep up the good work!

[@AgentJayZ]

@343jonny It's not really vacuum packed, but it's packed in oil to prevent corrosion. The packaging is sealed to prevent leakage, and looks vacuum packed to use as little oil as possible.

[@teddy_alfista7206]

Thank you a lot for this explanation! I'm an Aerospace Engineering student and thank to you i finally understood how these bearings work!

[@AgentJayZ]

Spey has two shafts or systems. HP system and LP system. The Trent is based on the earlier RB211, which was The first three-shaft engine successfully introduced by Rolls Royce. HP, IP, and LP systems. The Orenda 14 will be tested soon, I hope. We have many projects on the go... A couple years ago I posted a video of an Orenda 14 with elctric starting. "It's called vintage fighter jet engine". I've also got videos of electric start RR Avons... ...and propane burning Orendas...

[@AgentJayZ]

Yes... it seems hard to believe at first, but the LP system is never in any way mechanically driven by anything. The exhaust of the core has a lot of energy left in it, and could be accelerated out of a jet nozzle as it would be in a turbojet, or it could drive an LP turbine, which turns a huge fan and a compressor which feeds the core. The second option is more efficient, and quieter, which is why all big airliner engines are turbofans like the CFM56.

[@thedulcimer]

Your stuff is fantastic! Thanks so much, I am impressed with your detail and well edited videos. All I can say is thank you.

[@AgentJayZ]

The F-18 and the F-16 have different engines, but both are low bypass turbofans, which makes them twin spool. The type of turbojet which makes the most thrust is the one that flows the most air, and that usually means the biggest one, all things being equal, and they aren't equal. Afterburners add thrust to a turbojet, and not all of them have them.

[@daniel2001]

@AgentJayZ Ah cool. Thanks for taking the time to respond, and for taking the time to make your video's in the first place.

[@osama09128]

I am sure that , too late to me attending the watching of your great video but I am lucky now to be one of those attending your video you are great man, go ahead really we need your kindly support we appreciate these knowledge. thanks for every things that you sent to us

[@wasanthakulasekara9865]

great shows sir,i love to watch your great presentations, Thank you very much for sharing the knowledge with us

[@AgentJayZ]

@crazyrum The turbines are connected to the compressors. Typically for each shaft there needs to be three bearings: supporting radial loads at the front and rear, and one supporting the axial loads somewhere else. The thrust bearing can be anywhere along the length of the shaft, as shown here by both of them being at the front of their shaft.

[@SkyhawkSteve]

nicely done! I had wondered about how the bearings were arranged on multi-spool engines myself.

[@64jorthom]

Hi Jay, these engines are for the future of commecial airliners, from there the NX engines, less fuel comsumption, and less CO2. They're safer than other ones. New engines since a long time ago, they use ac/dc electrical system. It is my believe computers are doing much more work everyday. Thanks for this and all videos, a great job you're doing and many of us love it! Best regards!

[@AgentJayZ]

@AKiss620 cosistency is a big factor. Many small changes are added to newer editions of the manuals and documentation. A change in naming of parts that would contradict versions of the books would be awkward, expensive, and is generally avoided at all costs.

[@ElectraFlarefire]

Fine! I've dug deep enough into the archives and watched videos until I'm slightly sick of turbines to know I'm going to keep enjoying this in small but steady doses in the future. *subscribes* Keep up the good work.

[@SmokedTails]

The blade count differs in the CFM-56s. The -2B, as used in the 135 fleet, have 44 fan blades. The more modern versions of the 56s usually have the nifty wide-chord blades that lead to a larger dia. fan with less blades that turn slower to meet the required standards for noise regs to allow carriers to fly into more airports. I was curious if you could at some point do a video about airflow regulation in engines? VSVs/VBVs vs RCVVs, CIVVs and a bleed strap, etc. Thanks! Love the videos!

[@paqx3534]

I don't know what enough of those last words mean, and thats good enough reason for me to want a video on all of that

[@AgentJayZ]

@matube73 Also in Star Trek 2009, at about 1:25:00 there, in the engine room of the Enterprise, is a J79 afterburner fuel manifold ring, an LM2500 compressor case, and a stack of J47 combustor cans. Cool that we work on all of those engines ! And in the pilot episode of Battlestar Galactica (2003 ?) in the maintenance bay there are several RR/Allison 250 turboshafts on rolling stands... That was shot in the old BCIT building where I trained on those exact engines.

[@AgentJayZ]

@crazyrum Ball bearings by their basic shape can handle axial loads in either direction. Thrust bearings are slightly modified, as shown in the video, to optimize their load carrying in one axial direction, but they still can handle both. The load on the thrust bearing in a gas turbine engine changes in magnitude with power output, but it is always in the same direction.

[@denislushch6905]

What a great view of the stators, thanks!

[@AgentJayZ]

@MonoBawuino Dude... have some respect for the old school... The JT8-D is the most-produced large turbine engine in history. The CFM56 is a fantastic, beautiful, efficient and wonderful machine, but it dreams in its wet dreams of ever being as successful as P&W's transitional masterpiece.

[@AgentJayZ]

@mwiz100 Hey, I'm a Canadian, and proud of what my fellow Canadians have done...

[@AgentJayZ]

@tvirus457 ... If I said it that way, it's wrong. The radial drive shaft would be driven by the HPC, and the most sensible place to do that would be from one end of it, and the cold end would be better than the hot end. Your location is the right one.

[@AgentJayZ]

This nearly incoherent question is I think asking if there could be enough axial movement of the shaft due to heat expansion for the blades to come in contact with the vanes. Remember the engine cases are heated and expand also. But no, the engine is designed with clearances greater than the axial movement would be.

[@rchelimania]

@saxonlight and that's not counting all the stators and EVERYTHING ELSE... very impressive engineering

[@corrodesthefilm]

A larger fanned variant of this engine (the TF41) was used in the A-7 Corsair II. The exposed first stage is one of the reasons it was referred to as a "maneater." Careful out there.

[@AgentJayZ]

The CFM56 needs to have the fuel burning "core" brought up to starting speed. That's the HP compressor and turbine. So, like our Olympus twin-shaft turbojet, the starter is connected to the HP shaft. The Olympus uses a hydraulic motor for starter power, the LM1500 an air turbine, and some other engines use electric motors attached to the starter drive. I'm not sure what is the power source for the CFM56.

[@sharonjraj8080]

hey Mr.A.JayZ....that was a fantastic video.....I would like to knw whether CFM56-7B is having the same sets of ball n roller bearing in it??

[@AgentJayZ]

A turbine disk is extremely heavily built and is turning at a very high rate of revolution. In the extremely unlikely event that it should fail, nothing can stop the released energy and nothing can protect against the flying pieces of metal debris. The good news is that, if this one-in-ten-million chance event happens, the pieces fly out in the plane of rotation of the turbine. The lines indicate this plane, and you are advised to stand out of it.

[@AgentJayZ]

@MonoBawuino The CFM56 is getting on 35 years old or so, and still a fully modern engine. It will be very interesting to see what the next step will be.

[@jameswest8280]

For all you curious cats out there, I'll save you some math, (technically, arithmetic). There are 614 HP compressor blades * 15 minutes = 9210 minutes, or 153.5 hours, or 6 days and 9.5 hours. Just to inspect the HP compressor blades. What's that, you want breaks, we don't get no stinking breaks.

[@AgentJayZ]

The actual specifics of bearing locations are different for each engine, and are in the manual. Also, you have made the mistake of thinking the thrust bearings are called that because they transmit engine thrust to the airframe. This is not so. They are called thrust bearings because they handle axial loads, or thrust, place on the shaft. They could be called "axial positioning bearings". There is one on each rotating shaft, and can be anywhere along its length.

[@AgentJayZ]

@daniel2001 You could think of the HP system as the essential engine, or the "core" engine... and that's what it is sometimes called. The LP system is mainly a way of harnessing the power of the HP system and using it more efficiently to propel the aircraft, and it also acts like a supercharger for the HP "core". All of the accessories and power take-off devices take there power from the HP system. The only thing running off the LP system is the LP speed sensor.

[@si178970emq]

Very nice I’m impressed with your explanation wow

[@Jigme85]

And since you pointed out that this is the place for nice and interesting details ;-) here is a minor correction:The CFM56 has never been installed on the A330, however it is a very common powerplant on the A320 series. Furthermore these are missing numbers for blades/vanes installed on LPC/Booster Stage1--> 24 blades/108 vanes (on older versions i.e. CFM56-3 also 38 up to 44 blades) Stage2--> 74 blades / 136 vanes Stage3--> 78 blades / "" Stage4--> 74 blades / "" Greetings from Germany

[@mohammedalmehdar7749]

Thank u sir for your time and effort

[@veeaa]

The CFM56 has an air turbine started. It's similar to one of the videos on this channel except that it has it's own lubrication system inside with an oil pump.

[@AgentJayZ]

I'm not the expert on that subject but I hope he chimes in. I know the aerodynamic shape of the compressor blades, turbine and turbine nozzles were changed. The TF41 was tougher, simpler, and more powerful. Still, a very intricate engine with superior fuel economy for the power it produced.

[@SyrusWolfe]

As always Jay,thank you so much for sharing! Great video! Can't wait to see more ;-)

[@lmelin1959]

great video Jay.

[@DanFrederiksen]

Cool. Who makes the bearings? SKF? what rating terms do they use for jet engines, is that always custom or do they call it abec 11 or something.

[@exodu266]

Couple of questions about the thermal expansion.... The travel that bearing seem to have is quite massive, do you know how much of it is actually used ? If not what alloy is the shaft made out of and/or its thermal expansion coefficient ?

[@cmsracing]

Awsome! Thanks for referancing this vid. It answered all my questions!

[@pasoundman]

Although not really the kind of engine you encounter, I'm curious if you have any comments to make about 3 spool turbofans and especially in the light of the competition from the increasingly popular geared fanjet.

[@AgentJayZ]

@viperdriver82 You're right! I couldn't reshoot the video, and I forgot to fix that mistake with annotations. I was wondering when I would be caught. The reason I messed up : because the 330 is one of my favorite airliners. It looks like it giant bird that sticks its neck out far forward because it is so happy to fly.

[@scoobydog411]

I am 50 and I love engines. I was interested in how the bearings worked because of the high RPM's a engine runs at. they must use a lot of oil pressure? I work at a airport ( not on planes ). Great speaker . Thanks Gary

[@lazystart]

If I remember correctly from advanced troubleshooting class, another factor contributing to the CFM56's efficiency is a system that thermally expands/lengthen the compressor blades to minimize the gap between the blade tip and the casing, thus reducing the amount of wasted flow-by air. I'll go find my stack o' books to verify this.

[@professorsurya.n5301]

One of the best videos on the jet engine I've ever watched. Most practical, detailed and real stuff out there. I have one question.. What do the stator blades do on the compressor section?

[@AgentJayZ]

The stator vanes are what makes it a compressor. They provide a diverging pathway for the air that has been given speed by the rotating compressor blades. As the speed is reduced, the pressure rises, then the next stage of rotor blades speeds it up again. Repeat the process anywhere from 10 to 17 times, depending on which engine you sre considering, and the Compressor outlet pressure can easily be hundreds of psi.

[@professorsurya.n5301]

@@AgentJayZ right! Thanks!

[@AB-80X]

In terms of multi spool engines and the RR Trent engines. How does this compare to a RR Trent? Is the Spey system the same kind of system used in the 2 shaft GE 90s? From what I understand the RR Trent is a 3 spool engine, or have I misunderstood something? BTW, when do we get to see the Grenda 14 in action? I'm really curious to hear how the electric starter sounds compared to the huffer start-ups. Thanks for the super cool vids:)

[@AngryHybridApe]

Very informative. Covers everything in general. Translate techy terms well. (B +). No doubt the best yet on this topic.

[@AgentJayZ]

... Thanks... but why does your username contain "xenocide"... the killing of those not like you...? That's not very Canadian, sir... I am glad you like my videos, and I feel lucky to be able to bring this stuff to everybody else. I'll keep doing it as long as I keep hearing from people like you who like to watch it ! Cheers!

[@corrodesthefilm]

Jay: What are some of the differences between the Spey as seen in this video and the Allison TF41 that powered later models of the A-7 Corsair II?

[@tvirus457]

Thanks for the great videos! I found these a couple of days ago and I'm attempting to go through the entire playlist. You said that the shaft to drive the gear box and accessories was located at the third stage of the HPC. But it looks like the shaft to the accessory gear box on the diagram that I have (CFM 56-7B) passes between where the LPC and HPC are located. Then again, it is kind of hard to show on a 2D diagram a shaft which comes out of the page to a gear box on the side of the engine.

[@shaithesm0ck]

yes, please continue your detailed videos!

[@matthewbucknall8350]

So do the pitches of the blades in the compressor of a single shaft engine differ greatly to those in a twin shaft engine?

[@crazyrum]

Hi AgentJayZ, great video, thanks! Just one question, are there any thrust bearing near the nozzle of the engine? I understand that the compressors try to move forward by blowing air backwards, but the burning gas also try to push the turbines out of the nozzle. If there is no thrust bearing near the nozzle, does it mean that the engine is designed such that the force pushing the turbines backwards is definitely large than the force pushing the compressors forward?

[@matube73]

Another excelent vid Jay. Since ive been watching your vids, i see engine parts as props in sci-fi movies all the time now. e.g. STAR WARS a new hope: Centrifugal engine type intake screen in background of Luke's Tatooine house, ? a combuster can on shelf, stator section on the ground outside Mos Eisley cantina, double sided centrifugal compressor disk and and compressor manifold atttached to one of the manned cannons on the death star during the end battle scene. Keep up the good work.

[@daniel2001]

As interesting as ever.... One thing I was wondering (please forgive my lack of engineering knowledge), in a turbofan engine (like CFM56), does the gearbox take power from the high pressure or low pressure system? Watching your video's has made me wish I did aeronautical engineering at university...... I ended up doing Business instead.

[@343jonny]

Jay, why does the thrust bearing for the LM1500 come vacuum packed? Isn't it just another piece of metal like the rest of the engine which is always exposed to air? I was thinking maybe corrosion prevention?

[@abhinav87]

So now that all these parts come together, is there a real-world simulation to see how each compressor stage acts on the air? e.g. by using different coloured air pass through the engine or something along those lines?

[@AgentJayZ]

I read it. And I think it's the only place I've seen the word used.

[@RohitSharma-zg2ys]

Amazingly explained, made my day.. Thanks sir for this video.

[@arishtat4523]

Two questions. Do both shafts turn the same way? Also, any idea what kind of axial forces the shafts have to withstand?

[@johno9507]

12:00 Sorry but the Airbus A330 doesn't use the CFM-56 (that would be hilarious to see 😂). They use either the GE CF-6, RR Trent 700 or the P&W 4000.

[@AgentJayZ]

Yeah...I must have had the 340 stuck in my mind. Apologies!

[@shashair]

Hey @AgentJayz Great video! Could you please throw some light on how these bearings are fixed to the shaft? Is a key used or is it some kind of fit such as the shrink fit ?

[@scoobydog411]

I just saw your video on oil system. Thanks

[@petrkosvica7372]

Hi Jay Z, thanks for your excelent educational videos. I have a question about bearing clearence at jet engines. If you rebuild an engine and replace bearings, is necesarry to check axial and radial clearence? If yes how do you do it and what are limits of clearances? Thanks for explanation.

[@crazyrum]

@AgentJayZ Ah, I see, the ball bearing can provide force that prevent the shaft from moving either forward or backward. Since at first it has the word "thrust" on only one side of the race, I thought it is only designed to withstand force from one direction along the axle

[@clydecessna737]

Common error: The KC-135 series is a close derivative of the Boeing 369-80 technology demo aircraft. I beleive the wing is closer to the B-47 wing though I am not sure The 707 has a wider and longer fusealage and has a different wing though the two aircraft do share many parts and of course look similar. The 707 is 25% heavier.

[@eatonbeaver6083]

Great video explaining the two spool engine. I do have a question though. On 757 and the old L-1011 aircraft equipped with Rolls Royce RB-211 engines the engine instruments have an N3 indication. Does that mean the RB-211 is a 3 spool engine? If so what is the purpose of the third spool?

[@AgentJayZ]

Short answer: yes. Long answer to be in video form. Stay tuned.

[@occhamite]

good one Jay. Seems like it would be cheaper just to get a new engine.

[@alligatorpc]

Love this video.Thank you so much !!

[@MrJpsspecial]

Hi. I built the first test rig for testing the intershaft bearing they drilled a little hole in the cage for a radioactive pellet sothey could measure the speed of the cage. that was back in the 1960's it was for the Phantom fighter.

[@AgentJayZ]

For the Spey... RR likes to do things in the most complicated way. It's more elegant, the boffins would say! More straightforward, they are... The engines designed in the USA! Greetings from Canada, eh! In the afternoon of the eve of what will soon be New Years Day!

[@MrJpsspecial]

@@AgentJayZ Hi again I spent many-many hours testing on the engine parts although I spent a lot of them on the bearings & the turbine oil rotted my fingers .

[@RobertBardos]

why do jets such as the one in the video I just watched about the CFM56 have red stripes on the engine nacalle advising the location of the high pressure turbine location? just curious.

[@nakedbulletgaming4712]

your videos really help me a lot. I am an apprentice of a MRO. I wanted to ask, For the impingement cooling of Turbine blade, is the air taken from defuser.

[@AgentJayZ]

Cooling air is taken of the compressor, at a stage where the pressure is right to cause the desired flow rate. It can be tapped off the outer case, or it can be transferred throught the center of the shaft.

[@nakedbulletgaming4712]

@@AgentJayZ Thank you.

[@haquang1992]

Thanks man, sent from junior mechanic

[@AKiss620]

Just throwing a guess out there, the reason they might call those front 2 bearings collectively 3 is to keep it consistent with the station numbering for the engine overall. While it's actual location looks like it would be station 25 (between the LPC and HPC), since it is for the HPC it would make sense to call it 3.

[@BlitzvogelMobius]

Another great video. Thank you very much sir.

[@FrontSideBus]

Nicely explained. Bet a triple shaft engine would be far more complex.

[@dklearjet]

Wow I love your channel and is a really informative set of videos to help me with my growing love of jet engines. Could you help me with this question? How does the engine regulate the two systems (HP and LP) to run at different RPMs?

[@pascalmiller4798]

On the outside of the stator case you show near the end of the video there's what seem to be ways of changing the pitch of the stators. Is that actually what it is? If so, do most jet engines allow you to change stator pitch?

[@AgentJayZ]

+Pascal Miller Those are indeed variable stators, commonly called VSVs for variable stator vanes. It is a technology for preventing aerodynamic stall of the rotor blades by changing the direction of the airflow they encounter. the result is control over the resultant angle of attack of the rotor blades, which are mounted to the rotor at a fixed angle. It's a bit more complicated than that, and I am planning to make a video about it. There are other ways of doing the same thing, but many jet engines use variable stator geometry.

[@pascalmiller4798]

Fascinating! I look forward to a video about that. It would be cool to see the mechanism that controls the pitch too; powered by bleed air, hydraulics? I have another question too I've been pondering about. I remember you made a video showing the first stage ventilated stator and turbine blades, and explained how the cooling air prevents the blades from melting. My question is seeing as this is the part of the engine with probably the highest pressure (as it's hit with the freshly ignited gasses, where and what is pumping cold air directly through the blades? Bleed air from the compressor is certainly lower than the pressure of gasses hitting the first stage right? Or is the centrifugal force of the spinning blades sucking cold air through them? Last question, do you ever begin working on a strange engine (like some cold war era russian one), and realize that the parts are going to be too expensive or hard to find, and decide to scrap it?

[@veeaa]

The bearings are constantly lubricated with oil jets. There are good videos about that on this channel.

[@michaelpayne206]

It looks like the stator blades are adjustable, why? What makes these engines less noiser?

[@AgentJayZ]

@TheEPITROCHOID ... They didn't have an epitrochoid bacon strips one... Bacon weave = win !