Axial Compressors : Why so many stages?
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- čas přidán 14. 01. 2023
- 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 - Auta a dopravní prostředky
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!
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!
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
@@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.
@@MamoonSyed thank you very much i appreciate it
@@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.)
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.
Maybe we can discuss it during a high level meeting at Oshkosh?
@@AgentJayZ high level means discussing over a cold one …
@@qcan8468 🤣🍻👍
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 😆
That's why just about all I know about turbine engines comes from this channel
"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.
"If you can't find the book, don't buy it cause you won't understand it." HA! Had me laughing with that one!
😀Same
As a piston guy I love how you explain the "other" engine.
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.
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.
Love your dry humor and excellent explanations!
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).
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!
Yes, it's a joy to look at my older vids, and see how much I have aged.
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
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!!
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...
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
Hey I'm 15 years old and have an interest in MGTs, your videos help me a lot in understanding thank you
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 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.
A jet engine masterclass. Thank you so much.
You can't fool us, that's the inner spin drum from a Maytag washing machine!!
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. 👍👏
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...
I find your videos absolutely mesmerizing. Love how you explain how things like this work. Wild that this engine also flies on airplanes.
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.
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.
I must really appreciate the way you explain. God bless u. I learn a lot from your channel. Plz continue teaching us
Thank you so much for this. Always been interested in these engines. Cheers
What a great instructor. He speaks well to the laypeople, like me. He doesn’t go too technical as to leave me out.
Thanks for the kind words!
@@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!
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 CZcams destroyed in with an update.
@@AgentJayZ thank you sir. I only subscribed today and will now research your videos. Many thanks
Damn fine video. I'm studying Aeronautical Engineering right now and from what I can tell you explained it very well.
Great video, thanks for this amazing and dedicated work
Thanks. Especially today, that is nice to hear.
Very interesting engines, Jay.
Thank you. You made this fun to learn.
I learned sooo much. Thanks so much!
Your channel is great!
Great video ! Thanks for making it!
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.
Another great video. Thank you.
My favorite Canadian is back!!
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 😻
On the morning of each engine test day, I drink my coffee out of the P&W mug you sent me!
Experience at your purpose in life. Great video!
Jay's back. Oh yeah. I started working at Pratt & Whitney and these have been a great counterpart.
Well done, maritime engineers like myself love this
Sure would be cool to take a tour of the shop!
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.
You have the coolest job, I hope to land something similar one day
✌️😎
I work for THE company, 2500s, 6000s, and LMS. Love your vids.
Get back to work
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.
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...
Nice one Jay xx
Thank you Jz! I had bought the RR jet book about 30 years ago.
Which book?
www.pdfdrive.com/the-jet-engine-e185877924.html is one example...
@@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
@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.
And it would be a 900cc single cylinder engine or 7.2L if combined in a v8 configuration (439cui in old money)
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.
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.
Thanks! ... and those are dumbass comments. Thankfully they are rare.
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.
Dang thats some longevity, followup to a 10 year old video.
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. ;)
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.
i like this video a lot
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...
Sounds like it might be a steam turbine. Modern gas turbines are assembled from individual blades.
@@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..
*Awesome Possum!*
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.
Great to hear from an experienced pro. Thanks!
I use hp41cv on the iphone
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.
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.
@@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.
@@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.
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.
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?"
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
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.
great video
Thanks!
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.
I am in agreement.
Nice vid. Thanks.
*Interesting stuff...*
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.
Wiki says 8 LP and 7 Hp, with the first two stages of the LP being enlarged to create a 2 stg fan.
I haven't worked on the engine, and i don't have access to the parts catalog.
nice orenda rocker cover on the compressor rotor there
14:45 "Exponentiate" is the verb you're looking for.
yup,, thats Jay
Would be interesting to see more on connection between compressor/turbines and shafts
See my video called What holds it together...
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.
Thanks!
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
Professor compressor
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.
Yes.
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.
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
You are a hardcore nerd, but that is who I want making the stuff that makes me float across the planes ...
as always - read more than one book, great advice about any subject but particularly jet engines
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!
How dose the sealling of air work? Labyrinth seal
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.
Yes. That valve cover is from the Orenda 8. It was sent by a friend of Jet City. It's main feature was not efficiency, but up front cost. Is was/is less than half the price of a PT6.
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
CDP is influenced by inlet air velocity, general condition of the compressor airfoils, altitude, inlet air temperature, and engine rpm.
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. 👍
Check out Nye Thermodynamics for high performance alu boat
Jay I think your name would be more appropriate as - ProfessorJayZ
Thanks, but I'm really only an enthusiastic wrench turner with an interest in how these things really work.
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.
nice video
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.
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...
@@AgentJayZ Thank you! Just watched it, must have missed it along the way. I stand better edumacated. Thank you.
Curls my toes to think about those compressor rotors could " fall over " on the floor !
They are a few hundred kilos in weight, and no clumsy people are allowed in the shop. It would take a large earthquake to knock one over.
Ive seen similar used to compress natural gas to liquid so the helium can be taken out. Also seen a turbomolecular pump with a similar design for UHV stuff 🤓❤
Natural gas is a vapor at 900 psi. The propane in natural gas becomes a liquid at around 140 psi, and is removed so that it does not damage the high pressure pumps that can not handle liquids.
Never heard of helium content before.
@@AgentJayZ Helium production is a byproduct in some natural gas production. Some gas fields in the Midwest have a few % helium in them. The US had a near monopoly on helium before but there is now extraction of helium from natural gas in Algeria, Qatar and a few other places too.
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 a technician, the nuances of aerodynamic design are outside my area of experience and understanding.
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.
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.
How much did the compressor discharge pressure improve in the Orenda at high airspeeds? Any idea?
What is high airspeed for you? Airliner? Almost no change. The airspeed only counteracts the lower ambient pressure at flight altitude, iirc...
Schuesselmensch.
The pressure itself depends on the flight altitude and flight speed, which determines the pressure inlet pressure, the compressor exit pressure is this inlet pressure times the 'compressor pressure ratio' running at design rpm (100%).
Important to determine fuel consumption, for given design turbine inlet temperature.
An efficient compressor has, for given pressure ratio, the lowest compressor exit temperature.
All this becomes understandable if the 'temperature-entropy' diagram is used.
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.
Yes, and yes.
At ~26:30 the blades get smaller as the pressure rises because the density of the air is going up. The compressor is a volumetric machine while the energy is mass flow dependent. The mass flow is constant throughout the compressor, but the volume is always decreasing so to avoid stage stall, the blades get smaller because each blade is pushing more mass. That's all a bit simplified but it's accurate. Also, HP calculators rule!
Can you please explain why the stages get progressively larger on the turbine section of the engine? I think I understand it, but I am not sure.
Thank you very much.
@@leoarc1061 Just the reverse of the compressor. As the gases give up their energy, they expand. The volume increases and the mass flow remains constant, so the density goes down requiring more area to keep the gas velocity subsonic. Compressible fluids don't play well when trying to go supersonic.
@Michael Patrick That makes sense. If one were to use progressively smaller turbine blades, with the progressive increase of the fluid's volume, that would create a restriction to the flow.
I didn't contemplate the issue of the flow becoming supersonic as a result. It makes perfect sense.
Thank you ever so much.
Does each compressor have its own stator when installed in the engine?
Each stage of compression in an axial flow compressor consists of a rotating set of blades pushing air into a set of stators. For example, the Lm2500 has a single shaft, or single spool compressor, made up of 14 stages of compression, which all turn at the same speed.
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.
Just one thing. By "MacGyver style" i mean temporary solutions.
Btw, I think MacGyver was one of the best tv shows in 80's.
That's one of the things that I like most about working on jets. All examples of each model are identical. It's obvious when even one fastener is non standard, or one clamp is missing. If such an irregularity is found, the question becomes " how deep does this poor decision making go?" The owner is notified, and everything is reconfigured to the way it should be.
@AgentJayZ Now you us woke up my curiosity.
have you any examples which you could show in upcoming video?
Thanks.
Question. Does compressor inlet area or compressor discharge area [or whatever you call it] factor in anywhere in the calculations?
That would have an effect on mass airflow, which is one of the primary factors determining total power.
Gas path area is something determined by the engineers designing the engine.
@@AgentJayZ Thanks for the reply.
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
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
@@AgentJayZ ok I will take a look at it. Thank you I will look into that
cool propellers
I certainly am not an aerospace or aviation engineer. I just have been accused of being insanely curious, including all kinds of topics outside of my own field. I have been happy to follow various presentations and histories of jet engine development from the WW2 inventions to the modern era. It looks like the RB211 front fan is mostly serving the bypass purpose, which reduces the output side turbulence. That turbulence used to cause noise and waste fuel. I believe I see in the picture the large bypass channel all around the engine. Or am I wrong?
Not wrong. The RB211 was one of the very first high bypass airliner engines. 80% of the thrust is created by the fan.