Axial Compressors : Why so many stages?

The working title was "Compressors 2"
Watch the original "Compressors" here: • Compressors - Turbine ...
Also, the compressor stall video is here: • Jet Tech: Compressor S...
and the follow up Q&A video is here: • Compressor Stall Q&A

[@MamoonSyed]

I’m an aerospace engineer that works on designing some of this stuff and I just wanted to thank you for this amazing description and explanation. We learn this stuff in textbooks and on the computer all the time, but it’s truly something special to see the people who work on this stuff explain it in a way that really explains what’s going on, so massive kudos and thank you for sharing your experience with a bunch of randos online!

[@AgentJayZ]

Thanks! Your opinion means a lot around here. Although I don't know if the citizens of Jet City really think of themselves as randos... Anyway, input from professionals like you is very much appreciated!

[@danielmarquez8060]

I agree with your comment, question, if i wanted to read up on this subject whst would be a good textbook to read?! Thank you

[@MamoonSyed]

@@danielmarquez8060 sorry Daniel, just now saw your message! I think books are a funny topic because it really does depend on what you’re doing and works for you, hence why 10 different engineers will swear by 3 different books, and of those 3, each will appear to be good at its own little niche, be it theory, numerics, lessons learned, etc. Also, none of these books are going to work from the basic math and physics, so one does have to work to understand the concepts and nomenclature. That said, I did pick up a copy of “Principles of Turbomachinery” by Korpela which I have found to be a pretty decent book to have around for me. However, I do have friends who swear by Sultanian too. Moral of the story, there is no perfect book so just grab one and take what it gives you till you can’t take from it anymore. Then grab another.

[@danielmarquez8060]

@@MamoonSyed thank you very much i appreciate it

[@DeliveryMcGee]

@@AgentJayZ I have a friend from high school (son of my Mom's BFF), and I keep asking him how his steam turbine plant works, but he won't tell me anything or even give me a tour. Rude! (Joking, he's a Master Chief Nuc on the new USS G. R. Ford) (But I still ask his mom every time she gets back from a Tiger Cruise, "Ooh, did you get any pictures of him at work?" which amuses her and does not amuse her son.)

[@qcan8468]

AgentJayZ: Here’s your invite to see how we make all those LM2500 blades and vanes. You’ll need to make a cross country trip to New England.

[@AgentJayZ]

Maybe we can discuss it during a high level meeting at Oshkosh?

[@qcan8468]

@@AgentJayZ high level means discussing over a cold one …

[@cm9247]

​@@qcan8468 🤣🍻👍

[@Mentaculus42]

This is such a great channel where I have learned so many practical things that are not available elsewhere.

[@bryanst.martin7134]

Apparently Axial compressors fall under the helicopter explanation: It beats air into submission. 16X! Centrifugal just makes it real dizzy to comply. Aerodynamics in a nutshell...

[@bkbenelli]

"If you can't find the book, don't buy it cause you won't understand it." HA! Had me laughing with that one!

[@GeoffTV2]

😀Same

[@beingsentient]

The first axial compressor you counted the stages of, if you calculate using the equations you give on your blackboard, gives 1.23 pressure rise, average, across each stage, or 23%. That's more than twice the "10%" you suggested. Anyway, thanks much for your interesting video. It might be of interest to show the geometry of the stators and explain how the increasing area of flow converts kinetic energy to potential energy (pressure).

[@amadeuss3341]

I'm not into jet engines, but the way this guy describes stuff - you can clearly see his passion about his job. I don't know why - but i watching his videos completely 😆

[@amessman]

That's why just about all I know about turbine engines comes from this channel

[@scheusselmensch5713]

You can't fool us, that's the inner spin drum from a Maytag washing machine!!

[@rokadamlje5365]

Dang thats some longevity, followup to a 10 year old video.

[@folk.]

A jet engine masterclass. Thank you so much.

[@martinwarne7183]

"Not much of an engineer" by Sir Stanley Hooker is an autobiography of his life. He worked at RR on the development of the jet engine along side Sir Frank Whittle the inventor of the jet engine. Well worth anyone's time.

[@markniblack7160]

Love your dry humor and excellent explanations!

[@charlesdunn4634]

Jay I think your name would be more appropriate as - ProfessorJayZ

[@AgentJayZ]

Thanks, but I'm really only an enthusiastic wrench turner with an interest in how these things really work.

[@lewistempleman9752]

Professor compressor

[@PerfectInterview]

Amazing to realize that something that small can generate the equivalent power of 40,000 horses. Pre industrial civilizations relying only on animal and human muscle power could not begin to imagine generating power like that. And rocket engines can generate the equivalent power of millions of horses!

[@tylerw4593]

I just bought the Aircraft Gas Turbine Powerplants book on your recommendation. As a private pilot flying Cessnas who's working my way to airline pilot, this should give me a big head start in the required learning of these engines. Thanks for suggesting it.

[@grahamj9101]

PS I'm going to be mildly critical of the use of the term 'compressor ratio'. The term that I learned as a student in the 1960s was 'pressure ratio'. as used in my text book of the time, 'Gas Turbine Theory', first published in 1951. During my career, the term 'overall pressure ratio' came into use, to cover engines with more than one spool. And, of course, use of the term 'compression ratio' in relation to a gas turbine engine is quite wrong.

[@AgentJayZ]

I am in agreement.

[@beachbarlouie]

Great your back. I was just thinking I was in need of some over my head jet engine rhetoric. But it's getting drilled in and maybe someday someone will ask me a jet engine question and I will know the answer.

[@AgentJayZ]

It creeps up on you. You know you've been bit when you kick something heavy and brown out of the mud: "What's a stg 1 blade from a J79 doing here?"

[@TheDrew2022]

@8:36 Compressions ratio in piston engines is even simpler then that @AgentJayZ. Compression ratio is the difference between the volume of the engine cylinder with the piston at the bottom of it's stroke, to the volume at the top of it's stroke. So a cylinder that has a volume of 1L (1000mL) at the bottom of the stroke and has a volume of 100mL at the top of the stroke has a 1000:100 (10:1) compression ratio.

[@hisheighnessthesupremebeing]

And it would be a 900cc single cylinder engine or 7.2L if combined in a v8 configuration (439cui in old money)

[@scottmarshall6766]

Another way of describing piston engine static CR is "Swept volume/Combustion chamber volume". Thanks for all the years of great content, sure has gone by fast!

[@AgentJayZ]

Yes, it's a joy to look at my older vids, and see how much I have aged.

[@unclemonster48]

That’s the scary part we all watch you age but we all think we look the same from years ago. I’ve gathered more gray in the beard and some wrinkles in the face. Life of a industrial chiller mechanic

[@pinkdispatcher]

I'm also very sceptical about the 2.5 per stage. That would mean that a modern engine with 60:1 overall ratio would need only 5 stages. That doesn't seem right. 1.5 is more like it, that fits with a reasonable number of stages to get to 60:1.

[@raydolinger1980]

I worked in a Siemens building doing some commercial electric work and I noticed that they had a bunch of fan blades coming out of an oven that were an aqua green color.. The blades were a weird shape and had dot's and lines carved in them :/ They wouldnt tell me what they were for but I guess it was some type of newer turbine :) It was pretty cool...

[@JohnnyWishbone85]

Sounds like it might be a steam turbine. Modern gas turbines are assembled from individual blades.

[@raydolinger1980]

@@JohnnyWishbone85 They were individual blades johnny they were about a foot long each im pretty sure they were ge90 turbo fan blades, they had a serious twist in them... or the molds for them.. :) It was hush, hush around there... 8-10 years ago..

[@johnpowell5424]

Am I the only one who feels like a moron after watching these videos?

[@tihspidtherekciltilc5469]

Nope. I'm right here with you.

[@AgentJayZ]

You guys are not morons. You are curious and enjoy the info about these amazing machines. You can spot the morons in the comments: they are the ones who say that I am completely wrong, and don't know what I am talking about. Every tidbit and factoid in my videos is cross-checked in a textbook, and probably also a quick web search. My neighbor has a very smart dog, and there are several cats who wander the streets here. They all say my stuff is accurate, and so does my proof-reader. He's the raven I feed the bones to when I have chicken wings for dinner. Dude knows stuff.

[@Leighvander]

Very interesting video! THX! But isn't the "static ratio" 1 (instead of 0)?

[@AgentJayZ]

Yes, it is

[@elixirdeveloper6673]

Hey I'm 15 years old and have an interest in MGTs, your videos help me a lot in understanding thank you

[@cmsracing]

As a piston guy I love how you explain the "other" engine.

[@ericksonb06]

The way he explained how compression ratio in a piston engine made me yell at the screen. Completely wrong. Compression ratio in a piston engine is a simple math equation. What he's describing is how to measure cylinder pressure. What he's trying to explain is the difference between static and dynamic compression ratios.

[@AgentJayZ]

BE: Blah! I do not care about your theoretical, geometric, cartoon imaginary compression. I am talking about how much the compressor raises the pressure ( or density) of the air going into it. You know, the actual compression of the inlet air. Real, not imaginary, sales brochure, wannabe crap. What's the CR of a "12.5 to 1" piston slapper, if it has no rings? Not 12.5 to 1, Johnny, er.. Benny You comment made me yell at my screen.

[@FLYWHEELPRIME]

At one point in my life I serviced most of the LM25s West of Texas and South of Oregon. When they hit the DRMO sites and then out to the natural gas sites, pretty much any former military with turbine experience could work on them. One of the saddest months of my life was retrofitting an old destroyer LM25 with an updated emissions kit in Flagstaff AZ. I can still hear the old girl screaming "help! I can't breathe!!" in my sleep 🥲

[@greghelms4458]

My favorite Canadian is back!!

[@squid0013]

Most automotive engines can handle around 15lbs boost, built engines get up to 30-45. Most diesels will hold 45 from the factory, and upwards of 80 some as high as 100psi in built form

[@cameronalexander359]

I learned sooo much. Thanks so much!

[@dreddwailing5505]

A really interesting video as always, I would add that the engineers also had fifteen years of improvements in materials science to help them build the components they wanted to.

[@Vinzmannn]

Damn fine video. I'm studying Aeronautical Engineering right now and from what I can tell you explained it very well.

[@ncktbs]

i believe the current the diesel drag race record holder runs 90-120 psi boost and rebuilds the engine every weekend

[@AgentJayZ]

As we worked out here, the LM2500 uses over 500 psi of boost at full output of over 35 thousand Hp. It can do that for over ten thousand hours before needing an overhaul. I find it amazing to see diesel trucks outperforming gasoline powered race cars at the drags.

[@neshotah1976]

Thank You, that was very interesting. When I was in the US Navy, I was a TF30-P-414/A, jet engine mechanic at the Intermediate level. We were able to tear down the engine, (HSI) except the compressor. Did the majority of my work at NAS Oceana AIMD, and also on board a few aircraft carriers. The F-14 was just switching over to the new GE F110 engine when I left Oceana.

[@nuttyDesignAndFab]

"40 to 50 psi of boost is a lot"...yes, yes it is.

[@SimonWallwork]

Hats off to the Engineers.I've done 14,000 hours on jets and turboprops- from PT6 to the new Pratt GTF engine on the Embraer 190 E2. Not a shutdown, not a surge, nothing.

[@vermontsownboy6957]

Great video content. Interesting to hear about the LM 2500 compressor ratio. I just checked the stats for the GE9X engine (powering the new 777X): 61:1 compressor ratio...900+ PSI air delivery at end of compressor section. The compressor section sealing must be an engineering marvel. It also explains why airborn emergency windmilling engine starts have such specific high energy requirements, EG airspeed of 300+ knots at altitudes below ~25,000' (apparently need the denser, lower-altitude air to provide rotational energy to achieve engine RPM to start and maintain engine ignition). Related, I had thought the Pratt & Whitney geared turbofan series would offer comparable compressor rations, but they don't. Their advantage is the gearing allowing the fan, compressors, and turbine to operate at optimal RPM. Made me think back a few years to when Rolls Royce's "Ultra Fan" design studies included a pitchable front fan, the efficiency advantages of which could be enormous, including not needing heavy thrust reversers in the engine because the fan pitch could be reversed enough to provide braking. However, a British turbine engineer with RR who regularly commented on this channel (Graham?) stated RR had shelved that design study, reasons unknown. Anyway, the point I'm coming to is that some manufacturer, some day, may yet tie all of these promising features into a single turbo-fan engine: enormous compressor ratios; gearing for optimal operation speeds of the fan, compressor, and turbine sections; and a pitchable fan out front for optimum performance from a standing start to high altitude cruise. That would be some engine.

[@blackbirdpie217]

A cylinder compression ratio is not a pressure test standard, it's a design. Cylinder total volume at bottom center vs. Remaining combustion chamber volume when the piston is at TDC.

[@AgentJayZ]

Maybe you should review the procedure for doing a "compression test" on a piston engine. My racebike was 10.8 to 1. I'm sure you understand what that means.

[@blackbirdpie217]

@@AgentJayZ I'v been a tech for over 20 years, I've done many compression tests. You could look at it either way, but if you have a car with a known design you can publish the compression ratio in a service manual, and they do, even though they have no idea what the tested pressure is. It's a ratio, not a PSI. only a test can reveal how close the pressure might come to the design expectation. But does a compression ratio relate linearly to a pressure ratio? I mean if the CR is 10:1 does that mean the pressure will be 10 bar or 147 psi? If given only one stroke of the piston it will be rather disappointing. And every 4th stroke of the piston is only one stroke, not seven strokes to build max pressure which is my standard for a test. Even a perfectly sealed piston cannot produce 10 bar on a single stroke. Still the engineer assigned it a 10:1 ratio. Only a test of accumulated strokes can come close because of the extreme compressibility of air.

[@ashbridgeprojects6916]

@@blackbirdpie217 "But does a compression ratio relate linearly to a pressure ratio? I mean if the CR is 10:1 does that mean the pressure will be 10 bar or 147 psi?" - in a nutshell, yes you're correct. This is called Boyles law, or the ideal gas law. In reality the gas heats up when it's compressed and so the law is not 100% true. Boyles law states that, given constant temperature, a change in volume will cause an inversely proportional change in pressure. So 10:1 volume change will cause 1:10 pressure change.

[@Wyld1one]

Oticed s difference between the 1500 & the 2500. The blades - the 1500 has more or less straight blades( from inner to outer). They look like the walls of a straight cylinder. the 2500 those blades also have a twist from inner to outer. When i say inner to outer thst is from the center of rotation of the engine to the outer skin.

[@ccserfas4629]

Thank you Jay. Takes me back to the good old days of you teaching us the practical concepts of gas turbine engines with your excitement & charisma. Be well sir

[@SergiuszSwitalski]

As a software engineer working in aerospace customer training, your channel has provided great insight into the workings of the type of engines I work on everyday. Thanks!!

[@SilverStarHeggisist]

Now the real question is... I do I swap this into my pickup?

[@AgentJayZ]

LM2500 is about 4 tons, PT is about 10 tons, gearbox is a couple tons, fuel consumption is a few tons per hour, but with 35,000 Hp, you'll be idling must of the time, but that's still over a half ton per hour of fuel. We can get you one, for sure!

[@bassmunk]

@@AgentJayZ I love how after explaining all of that your answer is "We can get you one, for sure!" lol As long as it's physically possible and the customer willing to go through the effort, the answer is never "No" hahaha Never say never.

[@pibyte]

I am not an engineer I am an animator and artist - but just the beauty of these diagrams make me really curious about the book by Otis and Vosbury.

[@code123ns]

Great, as always! Just one thing: the CR for a compressor standing still would be 1, not 0.

[@zakp.2759]

Jay's back. Oh yeah. I started working at Pratt & Whitney and these have been a great counterpart.

[@olsmokey]

What is the lowest speed at which this type of engine can idle?

[@AgentJayZ]

It has an idle speed. It can not idle below idle speed, or it will be damaged by overheating the hot parts.

[@isnak907]

6700 is gg idle starter drops out at 4600

[@zapfanzapfan]

I stuck my nose into a cut up GE404-variant and was surprised by how few compressor stages there were after seeing your videos with engines with 17 stages. It had 3 fan-stages and 7 compressor stages, the compressor looked absolutely tiny and so did the combustion section. With 10 stages in total and a pressure ratio of 27 each stage should give about a 40% increase in pressure.

[@AgentJayZ]

The engineers do an amazing job, year in and year out. From 1951 to1975 or whatever... if you had a ten percent improvement in compressor performance each year, and it works like compound interest... that's definitely a massive increase...

[@tashfeenuk]

Can you please make a video explaining the function of pipes that are on the outer casing of aero-engines and industrial gas turbines.

[@AgentJayZ]

I've made a few videos about some of the systems, because there's a lot of things going on. I could try to do an all-inclusive description, but it won't be very detailed. Stay tuned.

[@tashfeenuk]

@@AgentJayZ Thank u, that would be good. Actually, for this subject area, I'm unable to find much information in books or research papers. I can figure out the bleed pipes, but there are many other pipes and accessories that Im stuggling to understand.

[@AgentJayZ]

Research papers will never deal with the specifics of hardwate of particular engines. Introductory texts are full of info, in a generic way, about the many external accessories of most common engines. The place to find specific info that you are looking for is on the overhaul manual for whatever engine you are curious about. Search for "(pick an engine) manual", and you will find that many are for sale online. The most recent and modern engines will not be available, but there's many out there...

[@tashfeenuk]

@@AgentJayZ thank u for the info, will check 🙂

[@TheHalloweenmasks]

I understand that there is a phenomenon in the rotor blading called the "deviation angle" of the gas, does this exist in the stator?

[@AgentJayZ]

As a technician, the nuances of aerodynamic design are outside my area of experience and understanding.

[@ben3989]

Your channel is great!

[@madnessmaker6162]

Another great video,as someone who designs and fabricates perf. turbosystems and fuel management systems for automotive and motorcycles for 30 plus years, I can relate to many terms used in the turbine engine industry, pressure ratios,compressor stall etc. I have always been fascinated by them and wished to own one at some point for use in a perf alu jet boat.but still need to learn much more about them. Similar to what you mentioned about advances in technology in the efficiently of turbines, the same has applied to today's turbochargers in compressor and turbine design. Some of the higher level gas engines are able to achieve boost pressures above 80 psi+ on single stage compressors . As far as turbine compressor stages being of different sizes, would you think that it may be done that way to compensate for changes in air temp and density as the air is compressed through each stage? Also ,I would assume somewhere there are compressor maps for the stages of turbine engine compressors? (that are most likely locked away for only the most special to see.. ha) Keep up great wk. I'm def going to invest in the books you mentioned. 👍

[@hopkinsroger]

Check out Nye Thermodynamics for high performance alu boat

[@robertpeters9438]

If you used a thicker marker, all of us could read your equations.

[@robinwells8879]

I suppose it’s like compounding interest in that you’re multiplying the product of the previous stage. Works well for pensions and turbines! You have a gift for imparting this stuff and I hope that you are part of the STEM education process in Canada. Your enthusiasm is infectious and could inspire a whole new generation. 👍👏

[@AgentJayZ]

I guess my effort is right here. I worked as a guest instructor at a nearby aircraft maintenance school, but I'm sure there were some politics involved. I was kept busy doing other things besides speaking about engines, even though one of the classes was just starting their turbine engine module. Interesting...

[@afterburner119]

Still one of the best sources of info. Greetings my friend, been very hectic at work, and once it’s public, I will let you know some more but anyway, wanted to say hi 😻

[@AgentJayZ]

On the morning of each engine test day, I drink my coffee out of the P&W mug you sent me!

[@mgabrielle2343]

So if a turbine shaft with number of stages of vanes of all same diameter and number of blades spin all at the same speed and there were no stators, then logically each stage is simply sucking the air in passing it to next stage which passes to next stage, until that same air passes out so same amount of air coming in goes out, hence there would be hardly any compression, compressing air needs restriction, if there is no restriction then what comes in simply goes out and so logically there cannot be any compression, therefore am I right in saying that stators create this restriction in order to compress what air is being sucked and and little goes out so it generates some compression, this then gets passed on to next stage which again takes what it gets from a preceding stage and further compresses it using the stators as restriction to air being received and air leaving that stage, remember in car engines a cylinder traps almost all air it has sucked in, given that some air escapes past piston ring gaps, and assuming valves are 100% leak free. So in turbine engines the magic of compressing the air is done by rotors with blades pushing the air in and stators trying to create a restriction in order for the air to compress against. Correct me John if I am wrong.

[@AgentJayZ]

You repeated yourself. Compression does not require restriction. The pathway through the stators is divergent, which causes aerodynamic diffusion, with results in compression. Stators are stationary, so they are not on a shaft, but mounted in the cases. Yes, you are correct in saying that the stators are where the compression happens. It works like this: the rotor blades increase the speed of the air, and the stator vanes convert that speed into pressure... then the next stage of the rotor increase the speed of the air...

[@LegioXXVV]

20% compression per stage, P(final)=P(initial)*(1+stage compression ratio/number of stages)^number of stages...that gives us an average compression ratio of 22 to 23% per stage. Think if it exactly the same way as calculating compound interest only here, we calculating pressure and not capitol, and stages and not years.

[@phizc]

You can use 16th root of the final compressor ratio. 2nd root is square root, 3rd root is cube root etc. Since 16 is a power if 2, you can also use multiple square roots, 4 in this case since 2⁴ is 16. ¹⁶√26 ~ 1.225845774135 √(√(√(√(26)))) ~ 1.225845774135 1.225845774135¹⁶ ~ 26

[@wolfemcgill6091]

Well done, maritime engineers like myself love this

[@markbrown4442]

Thank you. You made this fun to learn.

[@grahamj9101]

Hi AgentJayZ, Thanks for the mention: however, I’ve been slow in commenting, because I’ve been busy with STEM activities, DIY tasks and (name dropping) an e-mail conversation with Ian Whittle. As a matter of courtesy, I sent him the text of an article that I wrote for the latest issue of the Journal of the R-R Heritage Trust. The theme of the article was a rebuttal of the mythology that seems to surround the German axial flow engines, which saw service at the end of WWII. Compared even to Frank Whittle’s first flight engine, the W.1A of 1941, they were inferior in terms of performance, SFC, power-to-weight ratio, life, reliability and handling. Compared to the centrifugal British engines of 1944-45, they were grossly inferior. Moving on to the subject of your video, I think you’ve done a good job in explaining stage pressure rise to your subscribers. Although I was responsible for compressor design during my career, I was a mechanical designer relying on the compressor aerodynamicists to specify the blade and vane aerofoil forms. In fact, I am not aware that I was ever told what the stage-by-stage pressure rise was for any of the compressors I/we worked on. However, I would expect the stage pressure rise to be similar through each stage of a given compressor, because the same level of aerodynamic technology would have been applied to all the stages during the design process. Having said this, it might tend to increase across a multi-stage HP compressor with a constant annulus outer diameter. My reasoning is that the mean blade speed (in ft/sec or m/sec) increases front to rear, meaning that the stages can do progressively more work on the air. Conversely, the stage pressure rise across a fan booster with a falling annulus line might progressively reduce because of reducing blade speed. Are there any compressor aerodynamicists out there who can comment with authority? One of the last engines I worked on had an overall pressure ratio of 25:1 across 8 stages (3 stage fan, 5 stage HPC), which works out at a stage pressure rise of around 1.5:1. However, I would expect the stage pressure rise across the HPC to be relatively more than across the fan. Finally, having gone to Wikipedia (the fount of all knowledge?) for information, the overall pressure ratios quoted for the PW120, PW127 and PW150 are 12.14:1, 15.77:1 and 17.97:1 respectively. This means that the stage pressure rise of the centrifugal stages of these engines is, at best, comparable to the pressure ratio of the dear old Nene.

[@dennisbailey4296]

Has there been any hints in the future for the Orenda Iroquois Motor assembly? I'm sure it would be a great undertaking to assemble and aquire all the parts, and get it into working condition!! All the best from Surrey

[@alexaltrichter1597]

No corvette but do you have classified documents!!

[@AgentJayZ]

I do! They were classified in the early 1950s, and have since become old news. But officially, still classified "restricted". Why do you think my title is "Agent" ?

[@thehobbyguy7089]

I've always wanted to build a model jet engine for an RC jet with an axial flow. All commercially available RC jet engines are centrifugal flow. I just wonder if it's possible. I have seen a few projects take shape but ultimately fizzle out or disappear. I would think that today with the availability of 3D printing, it would have been done. What say you AgentJayZ, is it possible to miniaturize an axial flow jet engine for RC, the thrust it would need to create would be about 50lbs?

[@AgentJayZ]

Please see my video "so you want to design a jet engine". Also, Williams makes small axial flow turbojets and turbofans for missiles, starting at about 200Lbs thrust. Check out their designs, and see if you can get a price.

[@thehobbyguy7089]

@@AgentJayZ I am not looking to design and build an engine all on my own, as you state in your video, and rightly so, it would take a team of people to do so. I guess it sounds outlandish when I say "I want to build" when what I really mean is to want to build an RC aircraft with an axial flow engine and purchase the design and parts for said engine in said model. The problem is, there does not seem to be anything available. I have written William in the past and no surprise I did not receive a reply. The F121, which is the smallest William engine I can find reference to, weighs 50 pounds, which is too heavy for an RC aircraft. It's also 8 in diameter which is also probably too large. The largest RC centrifugal flow engine is about 96 lbs of thrust, and weighs about 8 lbs, is 5 3/4 inches in diameter. It would seem there is no axial flow RC engine in existence, nor a working design that can be assembled. I'm sure Williams of Pratt has something sitting in a digital file somewhere. From what I have seen, and I have been peeking into the space for about 20 years, it is relatively easy to home kit a centrifugal flow model jet engine from commercially available parts, usually lifted from a car turbocharger, the burn can is also fairly easy to make and there are many designs readily downloadable, all that said, it is not the same for the axial flow. I am not looking to build a better mouse trap and get rich, far from it. An RC model is a hole into which you throw money. I just want the most accurate model that can be built by human hands.

[@jamslylm]

Great video, thanks for this amazing and dedicated work

[@AgentJayZ]

Thanks. Especially today, that is nice to hear.

[@mxecho]

that book is so easy to find, jet engines are much moar complicated than eBay's search bar or the Dewey decimal system

[@MuhammadAkmal-xy3sn]

I must really appreciate the way you explain. God bless u. I learn a lot from your channel. Plz continue teaching us

[@jhyland87]

5:56 Something I'm noticing that I'm a little curious of... I can see how the air would get compressed as it goes from one stage to the next by looking at where the stator vanes would go, and from bottom to top (front to back) you can see that area gets smaller and smaller. But if you look at the last 2 rows where the stator vanes would go (so the two gaps between the compressor stages at the top), it doesn't get any smaller at all. How does that compress the air? Or does it just hold the air at the same compression while passing it back? Sorry for the long comment. Great channel - Amazing content :-)

[@AgentJayZ]

The narrowing of the gas path does not cause the compression. I have a video on that exact point. The narrowing is there to maintain the valocity of the compressed air, which is smaller after it is compressed. The reaseon the last two stages don't really narrow, is to bring the speed down a bit while the air is still being compressed. This process is continued in the diffuser section, immediately after the compressor. There, the air is further slowed as the velocity energy is converted to pressure energy by the diverging path. Yes, as the path widens up, the air slows down and increases in pressure. Seems weird, but remember the compressor is not a passive duct. It has a tremendous amount of power being added to it by the spinning rotor. Aerodynamics are quite counterintuitive, and you might need to do some further reading to fully understand what's going on in an axial compressor. Try Googling those two words...

[@jhyland87]

@@AgentJayZ thanks for the detailed reply. I haven't watched all of your videos (yet!), so I'll check out the one you mentioned.

[@martinmendoza920]

You have the coolest job, I hope to land something similar one day ✌️😎

[@antidecepticon]

You are a hardcore nerd, but that is who I want making the stuff that makes me float across the planes ...

[@jadenspires1891]

Have you ever worked with the Honeywell AGT 1500?

[@AgentJayZ]

Have not.

[@khuebner]

Very interesting engines, Jay.

[@bobrewer202]

What a great instructor. He speaks well to the laypeople, like me. He doesn’t go too technical as to leave me out.

[@AgentJayZ]

Thanks for the kind words!

[@bobrewer202]

@@AgentJayZ I am a subscriber and just a private pilot. I’m a pretty good shade tree piston engine mechanic, but have been fascinated by gas turbines. Is there a video that shows what N1 and N2 are, and their relationship between them? Also, what is the difference between compressors and stators? In general, I’d like to see how all stages of the engine work together, especially the “turbine” side.I realize that you are not my personal turbine guru and don’t have the time to explain all of this. I will go through your library of videos to see what I can learn and what I might still need help with. Again, your teaching style resonances with this dyslexic dude!

[@AgentJayZ]

All of those topics have been the subject of videos. Try the search box on my channel page, and maybe my platlist called Your Questions Answered. There used to be an index, but KZbin destroyed in with an update.

[@bobrewer202]

@@AgentJayZ thank you sir. I only subscribed today and will now research your videos. Many thanks

[@grahamj9101]

It's me again - sorry, but the pedant in me demands that I should say, it is I. At around 28:00, you state that the Avon compressor had zero and double zero stages added. In fact, the RA.29/Mk.533 , from which the Industrial Avon was derived, had a triple-zero stage. Although I never actually worked on the Industrial Avon, I can be confident about this, as my section and I were on the next row of drawing boards (yes, that was in the days long before things called workstations), where we were working on the Industrial RB211. Correction: I've been into my books and checked: AgentJayZ is right and my memory was at fault. The front two stages of the 17-stage compressor of the Avon RA.29/Mk.533 are 00 and 0.

[@AgentJayZ]

I'll take your word for it. A decade or so ago I worked on the industrial 1533 and the 1535 Avons. I'm not sure where they fit in the family lineage. Their parts books showed stages 1 to 15, preceded by a 0 stage, and a 00 stage at the very front.

[@allalphazerobeta8643]

Could it be that they didn't actually put the triple zero into production? You saw them make the drawings for it, not the actual parts?

[@grahamj9101]

@@AgentJayZ You are quite right - and it's my fading memory that's at fault. I've delved into my books and, yes, the Avon RA.29/Mk.533 compressor had 17 stages 00, 0, and 1 to 15. However, somewhere in the dim and distant past, I've come across a triple-zero compressor stage, but in which engine? Maybe, just maybe, allalphazerobeta8643 is right, but I have no recollection of seeing anything on the drawing board. Nevertheless, I do clearly remember seeing the design for the improved cooling of the stage 1 NGV and turbine blade for the 1533 industrial engine. This did get introduced and go into production. Maybe, a triple-zero stage was investigated as part of a project study for an uprated Avon engine, but was discarded because it would have required installation changes, whereas changes to the turbine would not. Quite often, we would draw up such design studies that eventually came to nothing. I remember drawing a project scheme for a two-stage marine power turbine, based on the TM3B single-stage power turbine that's waiting for this engine. It was intended to go behind a Marine RB211 gas generator, with the aim of retrofitting Marine Olympus installations. The project was cancelled because of the bankruptcy in 1971, but the design of the Industrial RB211 gas generator, based on the RB211-22B aero engine, went ahead a year or so later.

[@gregwilvert]

Just wanted to thank you, Agent JZ, for your fascinating videos that I’ve enjoyed the last few years. I appreciate your expertise and experience. It pissed me off to see a couple of smartazz comments here.

[@AgentJayZ]

Thanks! ... and those are dumbass comments. Thankfully they are rare.

[@thedarker9581]

Would be interesting to see more on connection between compressor/turbines and shafts

[@AgentJayZ]

See my video called What holds it together...

[@3dartstudio007]

Thank you so much for this. Always been interested in these engines. Cheers

[@andrekemp5059]

How dose the sealling of air work? Labyrinth seal

[@keithlewis9106]

Question, rain or water cannot be compressed, how does the jet engine compressor handle rain ??

[@AgentJayZ]

Water is compressible, as are steel, granite and diamond. They all require such huge forces to reduce their volume by any significant amount, the "for all practical purposes" we can treat them as incompressible. I answered this question yesterday. Here is the answer: If you go to the search box on my channel page, and type in "water", one of the hits is this video, where I talk about water ingestion. kzbin.info/www/bejne/sH-lm2ljrJZjsKc It's called Your Questions 19.

[@WarblesOnALot]

G'day, Water is only difficult to compress when in it's Liquid Phase. As the Rainyness of the Dropsicles progress through the Compressor as the Water "occupies Space" that raises the "Compression Ratio' applying to the Air, which heats up under Compression - thus boiling the pesky Raindrops into Steam ; and Steam compresses with no difficulty at all apart from requiring Containment and Mechanical Force. Lots of Jet Aircraft employ Water Injection, to obtain more power on Takeoff - by adding Steam Pressure/increased Volumd while cooling the Gasses impinging on the Turbine Blades of the "Hot End". At least, so I was led to believe - and so far I haven't been told of it being wrong. (Yet...). Such is life, Have a good one... Stay safe. ;-p Ciao !

[@JonPMeyer]

Water injection is (was?) actually a technique used by some aircraft engines such as the Pratt & Whitney J57 to improve thrust during take-off. I worked with a guy who flew KC-135's out of Phoenix in the early 80's. He said that the water injectors were finicky and if you happened to have two engines with malfunctioning water injectors on the same wing when you ran the engines to take-off settings with the brakes locked before take-off, the differential thrust was enough to yaw the aircraft on the runway. They would have to go back to idle, re-position the aircraft to the runway heading and try again. Sounds like a little more excitement than I would prefer!

[@hazza2247]

i like this video a lot

[@Katzenkratscher]

Go get a HP41 calculator for your cell phone.

[@tonygaytan9848]

Experience at your purpose in life. Great video!

[@adrianglessner5979]

I am very interested in learning more about jet propulsion units. Can you recommend a few more books other than the 2 mentioned in this video? Or someone in the comments. Thank you for the informative videos you do, I really do appreciate the knowledge you share for free.

[@AgentJayZ]

I just put Jet Propulsion in the Google search bar. The results were impressive. NASA is free. If you are interested in learning about the subject, There's a lot of great, free info out there. From there on, it's up to you.

[@InfiniteNallidge]

Can turbines run on hydrogen without major modifications?

[@AgentJayZ]

A turbine engine with fuel system designed for natural gas will run on hydrogen with no modification. A turbine is a part of an engine, and is nothing by itself... just like a piston.

[@InfiniteNallidge]

@@AgentJayZ I had just heard that hydrogen caused embrittlement and I thought it might corrode the turbine blades.

[@fg8557]

@@InfiniteNallidge The hydrogen will be burnt by the time it reaches the turbine. But the water vapour might cause excessive corrosion. And the combustor might require a redesign

[@AgentJayZ]

FG is doing some good thinking there. Hydrogen is the best possible fuel for a jet, according to P&W.

[@isnak907]

Rolls-Royce just announced a hydrogen turbine engine.

[@daveyt4802]

Sure would be cool to take a tour of the shop!

[@squid0013]

Im assuming the combustor cans contribute to efficiency as well? Modern high performance engines have an anular combustor housing which i assume allows better burn and better flow.

[@AgentJayZ]

Yes, and yes.

[@izysly6924]

Thank you Jz for this one! ❤️ I have a question that only you could possibly answer, it's about centrifcomp. Why don't they just use a compressor manifold to combine more than two centrifugal comps to increase...uh read more

[@AgentJayZ]

That would be unnecessarily complicated.

[@izysly6924]

@AgentJayZ that makes perfect sense and I can see your point but the early engines were too ,until some genius connected the compressor and turbine with a shaft

[@DeliciousDeBlair]

One of the factors that limits a plane's maximum altitude [its 'ceiling'] is how much pressure the engine can achieve in rarefied atmosphere. This was the first thing people started to notice when they tried flying high to avoid the Germans in WW2 so it was pretty much known by the time jet aircraft were first made, but they had to [sort of] 're-learn' it for high speed flight, as a few other factors changed how much air one was having to compress, and how the plane managed it.

[@Dreamer3K]

Yes.

[@rik999]

Airplane ceiling limits were noted in WW1 when German Zeppelins avoided British fighter planes by flying at high altitudes. The British countered by fitting their planes with superchargers which lead to a technical arms race that had the Zeppelins flying and bombing from 30,000 ft and both sides flying with oxygen.

[@99bristol]

I work for THE company, 2500s, 6000s, and LMS. Love your vids.

[@trialmx]

Get back to work

[@danielmarquez8060]

Great video ! Thanks for making it!

[@hisheighnessthesupremebeing]

So by that logic they would have been using metric tools on the SR71 Blackbird?

[@AgentJayZ]

SR-71 is an aircraft. I'm an engine guy. Sorry.

[@gueratom]

When you say 2500, you mean IAE V2500 ?

[@AgentJayZ]

GE LM2500

[@justinmijnbuis]

Always wondered why compressor vanes have strengthening support in the middle instead of at the tip? If you let that tip "ring" fit into a case recess wouldn't that be a much better seal at the same time? Probably many reasons why this is a bad idea :-)

[@AgentJayZ]

The mid-span shrouds, or "snubbers" found on large fan blades are to control vibration, and are in the best spot to do that. Newer engines like the Trent and the GE90 have wide chord fan blades that are much stronger and stiffer, so they don't have mid-span shrouds. Compressor blades to not have tip shrouds because the pressure differential is so small, and the further away you get from the rotational axis, the better it is to minimize weight.

[@alro2434]

@@AgentJayZ Those snubbers, contact points wear and are rebuilt with tungsten carbide & machined/ground. IIRC from applying for a job at Union Carbide near MIA in 1973.

[@foghornleghorn8536]

Another great video. Thank you.

[@oscarzt1652]

nice orenda rocker cover on the compressor rotor there

[@JohnnyWishbone85]

Recovering engineer here. I put myself through engineering school working as an operator at a cogen plant with a 2500. Then I mostly worked on steam turbines, and then a few startups before I decided engineering wasn’t for me. I actually loved the startups, but it wasn’t a sustainable way to make a living. Anyhow, this video reminded me of why I fell in love with the field to begin with, and I’d like to thank you for that. P.S. There are calculator apps that are available for your phone that use RPN. PCalc is the one for iOS, and RealCalc for android. Both are about ten bucks the last time I looked, but it’s worth it to me not to have to dumb myself down to use the standard calculator apps.

[@AgentJayZ]

Great to hear from an experienced pro. Thanks!

[@JeffMTX]

I use hp41cv on the iphone

[@aidantawney4776]

I know you said that you are a technician and not a designer, but I was wondering if you could help me or point me towards a resource for a question I have. So when doing some research on commercial jet engines using this book called, "Turbofan and turbojet engines : database handbook", I noticed that they tend to have a higher pressure ratio when they are at cursing altitude and speed then when they are at a static max thrust at sea level. I was wondering why this was the case, for example the CFM56-2C1 on the DC-8 has a overall pressure ratio of 24.7 at max power, and a pressure ratio of 31.2 at cruise. I was thinking it could be ram pressure but could it really be that much of a impact? Or is it because of something like variable stators and guild vanes? I would appriciate any help you can give me. Also completely unrelated but I really enjoyed the part at 27:30

[@AgentJayZ]

Well, if the throttle setting was the same, the only differences are ambient air pressure, being higher at standard test conditions ( sea level), and air speed, being zero at standard test conditions. At cruise, throttle setting is lower, ambient pressure is lower, and airspeed is higher, compared to test conditions. I would expect pressure ratio to be lower, but ram effect can really make a big difference. If the two conditions were both flying, max power vs cruise power at the same altitude, I would expect pressure ratio to increase as power setting increases. There is a very inexpensive manual out there for the DC-8 super 70 ( I think it's called that), That has a section on The CFM56 engines. I found mine at eflightmanuals.com

[@aidantawney4776]

@@AgentJayZ ok I will take a look at it. Thank you I will look into that

[@iandale]

If the main shop is in the middle of town, what do the new neighbours think of the noise? They love it too yeah? Great 🤣🤣

[@AgentJayZ]

Test cell, where we uh, test run the engines... is way out in the boonies, surrounded by classified forest.

[@unclemonster48]

Has classified vicious attack dogs and cats. 😂

[@DiveTunes]

Excellent video, Thanks! Question sir-- Do you consider the addition of fuel and combustion to be an additional stage of compression or pressure increase? I have watched your videos about the Bernoulli effect and that it is more velocity, not pressure, that we're after at the backend. I'd be interested on your perspective of the role of compression all throughout the engine.

[@AgentJayZ]

You may be interested in my recent video called Combustion Pressure. If you go to my channel page and type those words into the search box...

[@DiveTunes]

@@AgentJayZ Thank you! Just watched it, must have missed it along the way. I stand better edumacated. Thank you.

[@ashbridgeprojects6916]

I can't believe something that big spins at 10,000 rpm. That must be a blade tip speed of nearly 1000mph. That's insane.

[@leoa4c]

That speed would put the blades into supersonic territory. I don't think that these engines are designed for it.

[@cerebralm]

Remember RPM is revolutions per minute, not per second.

[@AgentJayZ]

Also, it's a compressor, and the speed of sound goes up with the density of the material it is moving through

[@cerebralm]

@@AgentJayZ Respectfully sir, increasing the pressure of a gas does not increase the speed of sound, but increasing the temperature does. Of course all else being equal, if you compress a gas, you will increase it's temperature, so this is perhaps a moot point. And assuming the outer diameter of each stage is the same, the speed of the blade tips at each stage will also be the same, so even if compression (or heating) allows the later stages to move through the air faster without creating shockwaves, it won't help the first stage. I think the original commenter merely overestimated the speed of the blades.

[@ashbridgeprojects6916]

I eyeballed the first stage at 0.8m in diameter. Circumference = 2.513m. 10,000rpm to rps is 166.667rps. 2.513x166.667=418.834m/s. 418.834m/s to mph = 936.905mph. After reading the comments, and assuming the blade tips of the first stage don't run supersonic, I must have overestimated the diameter of the first stage. New glasses for me it seems. For fun I'll solve for the max first stage diameter to stay below mac 1: speed of sound at sea level is 761mph or 340.197m/s. 340.197/166.667=2.041m circumference. 2.041/pi=0.65m first stage diameter. Agent Jay, how close am I! 🙂Edit - That's 2.13 feet for the imperial folk out there.

[@alikartal8426]

Thank you Jz! I had bought the RR jet book about 30 years ago.

[@LanaaAmor]

Which book?

[@AgentJayZ]

www.pdfdrive.com/the-jet-engine-e185877924.html is one example...

[@alikartal8426]

@@LanaaAmor "The Jet Engine" by Rolls Royce " (fourth edition, 1986). There is a fifth edition, it is available on Amazon: www.amazon.com/gp/product/1119065992/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1

[@robert5]

Great video. How about you do one on the SR 71 engines.

[@AgentJayZ]

Those engines are no longer used. I can only show and demonstrate the engines I work on.