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!

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

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.

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 😆

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

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!

"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.

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).

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

Love your dry humor and excellent explanations!

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!!

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

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.

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

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 🥲

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. 👍👏

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

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

A jet engine masterclass. Thank you so much.

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...

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.

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.

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.

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

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

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

I find your videos absolutely mesmerizing. Love how you explain how things like this work. Wild that this engine also flies on airplanes.

@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.

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.

Well done, maritime engineers like myself love this

Very interesting engines, Jay.

Great video, thanks for this amazing and dedicated work

My favorite Canadian is back!!

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

Thank you. You made this fun to learn.

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.

Your channel is great!

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.

I learned sooo much. Thanks so much!

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...

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.

Great video ! Thanks for making it!

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

Another great video. Thank you.

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 😻

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.

Experience at your purpose in life. Great video!

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

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

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.

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.

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.

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

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.

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

Nice one Jay xx

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

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.

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

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

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

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!

The Detail of the menusha of a turbine that you go into makes me feel like I could show up and actually rebuild an Orenda. ;)

Even though my day job involves the largest "blades and vanes" flying, I still love this channel. Is that a valve cover from the ill-fated Orenda recip? It was supposed to replace small turbines for greater efficiency.

Long time I could"t follow you, now I just come acroos with tnis video. I am very happy to know you are still active, thanks for all.

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.

great video

i like this video a lot

*Awesome Possum!*

*Interesting stuff...*

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. 👍

I recall that the JT 3 engine that was used in the 707 had 16 stages in the low speed compressor and another 9 in the second stage compressor.

great vid i actually came up with a question after seeing this, does the aircraft speed contribute to the cdp? thinking that at altitude with lower density and pressure the forward speed (inlet velocity) may be part of what maintains that cdp in lower density environment by increasing intake volume

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

14:45 "Exponentiate" is the verb you're looking for.

Nice vid. Thanks.

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.

Professor compressor

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.

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

How dose the sealling of air work? Labyrinth seal

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?

Hey Jay :) I have a question. how often do you see "MacGyver style" fixes in the engines when you stripping them for overhaul? As a car mechanic sometimes I cant believe in what I see, been wondering if same thing might apply to gas turbines? Cheers. Greets from Ireland.

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.

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.

nice orenda rocker cover on the compressor rotor there

How much did the compressor discharge pressure improve in the Orenda at high airspeeds? Any idea?

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

great video. One question. Does inlet pressure change when an aircraft is traveling at, say, mach 0.5? And does that affect CDP? I realize altitude will affect things but I am curious about inlet pressure at speed in an aircraft application. Obviously a stationary application is not questioned -it is constant atmospheric inlet pressure as the unit is not in motion

Question. Does compressor inlet area or compressor discharge area [or whatever you call it] factor in anywhere in the calculations?

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

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 :-)

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

as always - read more than one book, great advice about any subject but particularly jet engines

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

Does more compression always equate to higher power, or is there a topping point where you cannot pass (assuming its mechanically possible to get more)..

Thanks!

Great video ... plus thanks for the info on the books (an electronic .PDF is OK sometimes but being able to make notes in an actual paper book can be very helpful). (comment) I'm an old guy and I think in English units and then convert to Metric when needed. (question) I've read that modern 3D printing is allowing the development of cleaner burning jet engine fuel nozzle spray patterns. Is there any reason that more efficient (cleaner burning) fuel nozzles couldn't be retrofitted to existing engines so long as the fuel flow rate of the new nozzle design is in the same range that the old engine runs at ?

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.

Does the quantity of compressor sections and/or compression ratio affect response rate of the engine? Is that even a concern to operation of the aircraft which it's powering?