Jet Tech: Engine Configurations
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- เผยแพร่เมื่อ 31 ต.ค. 2021
- Nothing fancy here, just real information, needed by professionals and interested laypeople.
Yes, needed by... not just helpful to.
You know, essential.
Absolutely.
If you don't know this stuff, you are not meeting the minimum basic requirement. - ยานยนต์และพาหนะ
![ฉันจะ "แพรี่" ให้หมด - ผู้แข็งแกร่งที่สุดในโลกอยากจะเป็นนักผจญภัยให้ได้ - ตอนที่ 04 [ซับไทย]](http://i.ytimg.com/vi/PvmuP8y9IPk/mqdefault.jpg)
I applaud your ongoing crusade against the forces of ignorance.
Saw the title and clicked immediately. Even though I already know this stuff I just wanted to say, I found your channel back in 2007 - 2008 (honestly can't remember it's been so long) and you're one of the reason's I'm an aircraft mechanic today.
Awesome, what do you work on?
@@donaldstanfield8862 Commercial category aircraft. I've worked on a host of birds from ERJ170's all the ways up to B747's and various things in between. Currently I mainly work on B757's.
Computer tech; no, that box is a computer, not a hard drive... The hard drive is inside. I spent my first 5 years in computers explaining this... Love the channel Jay Zed ;)
Neen there doen that... 😁😂👍
JZ you ar incredible! You were talking and explaining for 24 minuts with onley 4 video cuts.
Amazing! 😎👍
Thank you for clarifying the power turbine, and also what a turbofan are. You explain things so well. I enjoy your videos and your presentations so much. I understand about saying one thing but meaning something else, it drives me crazy too. People need to be precise.
Thank You for a concise presentation.
I'm a tour guide at an aviation museum, where we have a cutaway J47 (turbojet!) on display. There's much to see, and I give myself about 5 minutes to explain the J47's workings to our visitors. Your presentation helps to refine my presentation.
Thanks! Are you aware that the J47 is one of the engines I work on?
I have quite a few videos posted about the J47, including test runs.
You might like them.
@@AgentJayZ yes, I've many. Excellent t work
I've watched many
Excellent class ! Your a great teacher. How lucky I am to have sat in on your presentation. Funny I kinda have these types of conversations with the Mrs. especially. I have found throughout my life that people often can not phrase their question correctly because they don't understand what they are asking about. If they could ask the question properly, then they are almost to the answer. But that takes a lot more work and they are usually looking for the short cut. I am cursed with the curiosity of understanding, and for some strange reason love the process and the final product which hopefully = wisdom. " To me your a genius ". Rush Time Machine Tour intro 2011.. Yes, I'm a big RUSH fan.
Your / you're --- tom(ay)to / to(mah)to.
Too bad your "curse with the curiosity of understanding" doesn't extend to an interest in common grammar.
@@manifold1476 👊🏼
@@manifold1476 Nope, I'm too busy looking for the faults in others to notice. Jeeze...
IMHO, the so-called platonic one is definitely not. He's a glass 1% empty type, as opposed 99% full type.
Far less desirable than to be a top fuel fan, I say.
I've said it before and I'll say it again I love you Jay keep up the great work and make sure you include all the awesome sarcasm. Words mean things and thank you always for pointing it out
After a hard shift by the look of it, you still took the time to explain. Top man.
G'day,
Yay Team !
Extra points for not getting anything awry when ye were talking of Wind Turbines...
One often has to take issue with the people who opine that "Windmills are not really Turbines" ; because ALL Turbines are (technically squeaking...) various subspecies of "Windmills".
The ones with which you deal with are Ducted Turbines designed to run in high speed hot, burned, and indeed still burning Windiness...; and there are Windmills which are configured to run in Superheated Steam, as well.
I'm quite partial to H.A.W.T's, myself (Horizontal Axis Wind Turbines) running in Free-Air (as opposed to their being Ducted...), because they can be readily laminated from Wood & then hand-carved ; literally just(ifiably ?) like a Propeller, but running inside out, upside down, and backwards - extracting Energy from the Air Column and converting it into Torque ..., rather than pumping Torque into a rotating Blade Array - in order to shift Air and thus generate Thrust...
Wooden Airscrews or Turbine Rotors are Dynamic Sculptures, in my opinion ; very satisfying when they work well, and bloody dangerous when they go wrong.
Such is life,
Have a good one...
Stay safe.
;-p
Ciao !
you could make a 30min video on why paint dries and i'd still watch the whole thing. love your explanations, excellent
I commented awhile back on how helpful you have been helping me to be able to 'talk shop' with my newly recruited USAF son. To make a long story short, he graduated near top of the class and is now a maintainer for USAFAng 109th transport out of Scotia, NY. Their primary mission is to support Anarctic research in the only ski equipped C-130. He was amazed that I knew so much as he was working on the trainer T-56 at Lackland AFB. Again, I just want to thank you for everything you've taught me in your videos, it has helped bond me with my son just when I was starting to feel the empty nest syndrome. Merry Christmas and a Happy New Year to you and yours!
Great to hear. I think you already know that my "turboprop core" video is of a 501, which is the industrial gas generator version of the T-56...
It's a cutaway tour.
@@AgentJayZ yep! As a novice, just learning the basics of a powerplant was huge for me. Especially your "closer look" series really helped. My son was impressed when I told him his lockwire would be representative of how meticulous he was as a maintainer :) I can't tell you how appreciative I am for your videos. Thank you! He got a real kick out of your video of the worse nightmare sound a maintainer could hear with the lost bolt dropping into a compressor or tubine fan. It was a cringe worthy video to him :) Anyway, huge fan, and again, all the best for you and yours!
Another great explanation 👌 simple-ish, easy enough to understand
Thanks for the review of terms. Over the time I've been watching your videos I've tried to review the terms to fix them in my own mind. Your review simply reinforces my understanding. When you started showing us your work on the Allison I had to review the terms because it appears to me its configuration inverts the gas turbine and power turbine (the gas turbine turning a solid shaft which goes through the hollow shaft of the power turbine.) I think I understand it but It's entirely possible I've misstated that and if I have I hope you'll correct me. I've learned an incredible amount from you on a subject about which I had zero knowledge, but clearly only a smattering or your total knowledge. Thanks for your efforts to teach us.
I want to thank you for these videos. I learnt so much about turbine engines and its really intresting i wasnt able to watch every video though but i do love your channel.
You are a funny guy… all those parts, I don’t have to tell you. Laughed Audibly. Headed to the ol’ jet factory myself. Very excited to be able to share (one day) what I have been working the last three years. Glad all is well in Jet City, if you think about coming to Sun n fun 2022, me and the wife will bring you another Pratt “care package”. I have a box with your name on it. Hey did you see the USAF Jet fuel out of air article. I immediately thought of you 🙃.
Think I saw it, but didn't read it... yet. I woke up late today and am having a coffee in that mug.
It would be cool to see where you work.
Jay you're one of the coolest dudes I know
Very clear explanation, thank you.
Thanks for clarifying that.
Always great information on this channel. Man i wish you were my instructor.
AgentJayZ has been my instructor for years thanks to TH-cam.
Thanks, John!
When you said a turbine assembly converts fluid like air into rotary motion then mentioned wind turbines it finally clicked. A wind turbine just has to be as big in diameter as it is to harvest as much energy from a relatively slow moving source coupled to a gearbox which multiplies instead of reduces the rpm to the generator head. It is like a big uncontained turbine assembly. I always wondered why they were called wind turbines
A turbine is a mechanism to convert fluid flow to rotational motion. Wind mills, water wheels, part of car turbocharger all do this.
Thank you for this video
...Some think of power turbine as "Just a fancy windmill"
Interesting I made the false assumption the Olympus 593 was a low bypass (like many fast jet engines eg F404) not a twin spool straight jet.
I'm not sure the TPE311 has a jet nozzle on it. I think 'prop-jet' was Cessna marketing for the Conquest over the piston powered 421. (Piston/Turbine Powered is ok, right?)
Also the TPE311 (as an example) is a direct drive turbo-prop. The PT-6 may be the most popular engine, but not all turbo-prop engines are 'free power turbines'. Not sure in the helicopter space if there are any direct drive examples? To be clear the core directly drives the gearbox (ie gearbox input is directly bolted to the shaft of the engine) not the propeller directly... because that would make the prop want to spin several thousand RPM which is way above what you want. Although that has happened... Thunderscreech for one example!
To add more complexity, of course you have three spools on most RR engines (fan/LP, IP, HP) and now with the 737Max/320NEO the geared engines which I believe are still two spool, but the LP shaft drives the input to the fan gearbox so the fan is even slower than the LP compressor. It's all about tip speeds of course... supersonic tips is not ideal (leads to the 'buzz' noise of the CFM56/IAE2500), so slower rotation for bigger diameter is required of course. Airlines like big fans and they cannot lie!
Key word was "simple".
But, extra cookie for you, for pointing out the single shaft engines... Not really "direct drive" because a reduction gearbox is used.
Anyway, thanks!
No mention of Turbo Pumps. No need to throw fuel on the fire.
A turbopump is not a gas turbine engine. It's a power turbine driving a pump. The ones used in the big ol' rockets are amazing, but are nothing special...
Would you ever do a video explaining the general design of a Turbo-ram-jet? More specific the Pratt & Whitney J58 engine found in the Blackbird. 🧐😁
I am considering it. There is nothing "general" about the J58. Most people commenting about it misunderstand it.
@@AgentJayZ I may or may not fit that criteria. 😅Please educate me! 😀The SR-71 is my childhood favourite plane and I would love for someone who actually works on turbine engines to make a video about this particular engine and what allows it to operate at Mach 3.2 and onwards. I really like the whiteboard videos.👍
Hey hey I give 5.5 attaboy's the .5 is for the PT schematic. I've been called a fellow and lassie before LOL.
A hopefully not too stupid question: The LM2500 is derived from the CF-6 be removing the fan and LP turbine as you mentioned. If I remember correctly you said in an other video that the fan also functions as the first stage of the compressor. I.e. the CF-6 is effectively a twin spool 17 stages compressor design. 16 stages in the core, 1 compressor stage (the fan) on the 2nd spool. Wheres the LM2500 has a single spool 16 stages compressor configuration. So one of the modifications from CF-6 to LM2500 would be an adaption for the engine to work with 16 instead of 17 stages of compressor? (An adaption that may be as small as a different setup of fuel control parameters.) Or is the difference of removing the fan as first compressor stage not significant to the core? I.e. the LM2500 works just as well as the CF-6 core, but without the fan. Maybe a tiny bit less efficient or with slightly less power, as there is slightly less compression ratio on the LM2500 compared to the CF-6.
You are right. GE sometimes calls the fan a core booster. Literally a turbocharger for a jet engine.
I'm sure a small amount of compression is lost by removing the fan, but the engineers would have adjusted the fuel control to handle everything without difficulty.
The big two-spool turbofans from GE and P&W (and most two-spool high bypass turbofans) have so-called 'booster stages' on the LP shaft, immediately downstream of the fan. As they are turning at the same speed as the fan, they are aerodynamically lightly loaded.
When we designed the Industrial RB211 in 1972/73, in removing the fan, we recognised that we had lost the pressure rise produced by the fan. However, we designed a new first-stage blade for the IP compressor, which recovered some of the loss of that pressure rise.
I could sit all day learning
Hi Agent, during my training on the H120 helicopter, I came across something weird. Maybe you can shed some light?
In the engine limitations section of the flight manual, we have an normal operating RPM range of the power turbine. Above that, we have "max continuous" and "max transient" limits as expected. However, below the normal operating range, there's another "transient range" as well as a minimum RPM rating. (The transient ranges are time-limited to 5 seconds).
I'm wondering what happens in that range: Will the turbine overheat, stall, or what exactly are the risks there? My instructor could only tell me that it will likely never be a factor due to other limits being reached much earlier. But I'm interested in the technical reasons behind this.
Thanks alot already!
I've explained the design of the Tyne aero engine and Marine Tyne before.
The Tyne aero engine has two spools, with a three-stage LP turbine driving both the LP compressor and the prop, through a reduction gearbox. The Marine Tyne engine is comprised of a two-spool gas generator, with a single-stage LP turbine driving the LP compressor, together with a close-coupled two-stage free power turbine. The single-stage LP turbine is the first stage of the aero LP turbine, and the two-stage power turbine is the second and third stages of the aero LP turbine.
@Sheila Walker 'Spools'? It's a common enough term in industry for a compressor and the turbine driving it - and someone has used the term elsewhere in these comments.
On the subject of the Marine Tyne engine, the Royal Navy's Type 21 frigates, early batch Type 42 destroyers and Type 22 frigates had two Marine Olympus and two Marine Tyne engines. Later Type 42s and Type 22s had two Marine Speys and two Marine Tynes. The last Type 22 was retired from RN service in 2011. However, some of the class were sold off to other navies and are still in service, which is perhaps why AgentJayZ has been able to show us Marine Speys and Marine Tynes being tested.
The Tyne aero engine is, I believe, still in service in the Transall C-160. To the best of my knowledge, Rolls-Royce at Bristol was still providing in-service design support until quite recently. I recall being told, only a couple of years ago, that a redesign of the HP turbine blade had been carried out, in order to replace the archaic method of manufacture of the original design.
@Sheila Walker Yes, the Tyne aero engine first ran in 1955 and there have been no major redesigns and uprates since then. Of course there was the mechanical redesign to produce the Marine Tyne, with its free power turbine, which happened around 1967/68. I was still a very inexperienced designer and they only let me bolt a few accessories onto the engine. It did get a redesigned HP turbine blade for the RM1C uprate, as I recall, but that was about it.
In terms of longevity, the Pegasus engine in the Harrier had its first run in 1959 and the Harrier is still going strong with the USMC. However, that engine has had some major redesigns and uprates on the way to the 11-61, aka the F402-RR-408. My contribution to the 11-61 was an uprated fan, which was designed by my team at Bristol in 1987.
But credit where credit is due, the JT3D, aka TF33, in the B-52H has had a long in-service life, having had its first run in 1958. It will be a few years yet before the BUFFs get their new BR725, aka F130, engines.
@Sheila Walker I drove a succession of Austin/Morris Minis and 1300s. They were all powered by what was basically the BMC A series engine, which began life in 1951. It was progressively enlarged from 803cc to 1275cc, and finally went out of production with the end of 'classic' Mini production in 2000.
@Sheila Walker I don't know whether, in 'normal' times, they allow conducted tours of the plant at Indianapolis: they do at Bristol.
Returning to the subject of the Tyne, I had a liquid lunch today with a recently-retired former colleague who was involved with the in-service design support of the aero engine. He put me right on a few details.
Apparently, the French wanted to place a bulk order for spares, including HP turbine blades. However, R-R couldn't find a supplier capable of making them, using what is now a totally archaic process. They were forged from dumbbell shaped preforms, which were drilled and copper(?) rods were inserted into the holes. The preforms were then forged to the final aerofoil shape and the copper leached out with acid, leaving oval-shaped cooling holes. No-one has done that process for decades. However, to try to avoid validation testing of a cast version of the blade, R-R is, he tells me, still trying to get the blades made to the original process.
The irony is that, years ago, the uprated Marine Tyne RM1C had a cast HP turbine blade introduced, with a major redesign of the cooling passages, and in a different material.
@Sheila Walker A very interesting theory! The Mini Moke became popular as a beach buggy and it still has a cult following.
I will say no more than, as a teenager, I was able to borrow my dad's Ford Zephyr, which had a bench front seat and a column gear change. That was before I had my first Mini: however, that was a Minivan .....
I'm an official resident of Jet City.
I would love to see a video on the SR-71 engine. I know they're out there but I prefer your take on it.
The part where I say we're not talking about turbo-ramjets here... I meant it.
The J58 was only made in the dozens, it was hideously expensive, inefficient. and it has been dead for decades.
In every way, except one, it is inferior to the J79.
@@AgentJayZ I apologize I thought you meant not in this video when you said "not here" if that's not your cup of tea no problem
"Now It's Dark"...Frank Booth LOL
You missed the single shaft cold end drive, which is basically a gas generator with an extra turbine stage bolted to it to extract energy to drive the electrical generator. Runs at 100% speed cheap and efficient. Albeit not used a great deal in the aviation industry apart from some helicopter turbo shaft and turboprops that have constant speed variable torque requirements.
Yes. See below, and above.
In the power turbine section, does it contain multiple sections or one large turbine?
There are many designs, from one stage up to six stages that I know of. They all function well.
Review your gas turbine history, the turboprop engine came along years after the first use of power derived from the shaft of a gas turbine engine. Look up GT Neuchâtel from 1932.
Can you explain how a 3-spool engine (RB199 for instance) has advantages over a 2-spool or one spool?
I've already done that, a few years ago. I might make another video on that subject.
In one line:
1-spool is good. 2-spool is very good. 3-spool more optimized but more complicated and expensive.
Agent jay zulu, do you know how to find the engine exploitation manual of a R11 F2S 300 engine and how to dismantle it ?
I have no info. I could search for it, but that's what you should do.
2:31 Probably verbatim what was going through Frank Whittle's logic stream around 1928 or so.
@@grahamj9101 Like I said, he was probably thinking along the lines of "Let's get rid of all this." prior to his patent application in 1930. Hence the "or so".
@@jpatt1000 I've been trying to post a further comment to you, but it just disappears, so here goes once more.
If you want to try to understand Frank Whittle's motivation and thought processes in his early days, I suggest you read get a copy of his book, 'Jet: The Story of a Pioneer'. It was first published in 1953 and a copy of a first edition will set you back around GBP50, but copies are on sale in the USA.
@@grahamj9101 I got this message. I wonder what happened to the others you sent. I'm fortunate to live in Oshkosh and the EAA Museum library has a copy of Jet. (Theirs has a picture of the butt of a F-106 or Mirage. Some delta winged jet. It's been a while!)
@@jpatt1000 I can also recommend, 'Jet Man: The Making and Breaking of Frank Whittle, Genius of the Jet Revolution'. It was published at the end of 2020 and is now available in paperback for around GBP10.
Let's see if this message gets through: those that did I had to send via my cellphone - we call them 'mobile phones' in the UK but, of course, we hear your terminology all the time in movies and on TV.
So why am I almost obsessively interested in Whittle’s life and work? Because I regard him as having laid the foundations for my career lifetime in gas turbine engine design. I also have a more specific connection, as I served my apprenticeship with Bristol Siddeley Engines, Coventry, in and on the outskirts of the city of his birth, and one of the Section Leaders I first worked for was a former Power Jets employee.
In November 2018, I drove up from Bristol to attend a lecture given by Ian Whittle, in the very room at Brownsover Hall that served as his father’s office during WWII. However, before the lecture, I drove the few miles into Coventry, to stand for a few moments before a very small, very ordinary terraced house (row house, or town house in US English). The house bears a small plaque, marking it as the birthplace of ‘Sir Frank Whittle, Inventor of the Jet Engine’.
Whittle came from a humble background and he probably retained an noticeable working-class Coventry accent at the beginning of his career. I suspect that much of the antipathy towards him was as a result of the entrenched class attitudes of the time. Here was a pilot cadet of short stature, only recently promoted from an engineering craftsman apprenticeship. He had no formal education in thermodynamics, fluid mechanics, etc, and yet here he was putting forward an incredible proposal for an aircraft propulsion system with no propeller?
I miss the jet nozzle on the two shaft turbojet.... and a question: is there always a power turbine (that is mechanically seperated from the gas generator shaft) in the industrial use case and turboprop engine ore are there engines that couple the workload directly to the gas generator shaft? uups, I commented to early about the nozzle....
Yes, there are single shaft industrial engines. They take much more power to get started, but once going, they are equally as good.
There are aero-derived, two-spool industrial engines, where the LP turbine drives both the LP compressor and the load: the GE LM6000 is an example.
And there is a three-spool engine, the Industrial Trent. The fan has been replaced with a three-stage (from memory) LP compressor, with the LP turbine also driving the load.
Such engines typically have large handling bleed features at the LP compressor exit.
Nice explanation , never understood the advantages of the twin spool engines- thank you! One question I’ve always wondered about the gas generator version, I understand the expanding gas is used by the power turbine to turn the generator shaft but I’m surprised there isn’t enough residual energy in the exhaust ( which you said is now just heat) to do something useful with? . This leads to another, possibly stupid question ☺️- has there ever been a sort of “hybrid” design? Like maybe a helicopter/ turbo prop engine to used to turn rotors but also with an exhaust used to provide some thrust as well?
First question: it's wasteful to have mechanical power (pressure and/or speed) in the air leaving the power turbine. That would be energy that could be extracted but is lost and therefore wasted.
The only stupid questions are the ones you dont need to ask 👍 Residual thrust for conventional helikopters turns out to be no more than 4-5% of the rotor thrust - not really a major factor. There certainly have been desings utilizing similar concepts to what you are referring to, most notably the many autogyro designs (ex the Fairey Jet Gyrodyne). As often is the case with aeronautical engineering - there are a lot of "nice idea, would probably work" but drastically fewer "here's a real world demand and half a century of empirical data that proves your design useful".
your "hybrid" is basically a bypass turbojet, most of the energy is used to drive a fan (which is much like a prop) the rest of the energy goes out the back through a nozzle adding thrust
KJ: you need to be better at paying attention.
Pizza Gogo: Helicopters have exhaust ducts designed to eliminate residual thrust, but a few turboprops do have exhaust nozzles that contribute a few hundred lbs of thrust. They are not called hybrids, but nobody will get upset if you want to.
Do they ever make use of a nozzle in a power turbine set up for a generator? All the best from Surrey
You need to see my video: what is a nozzle...
The power turbine has nozzle guide vanes - and the power turbine produces a similar back pressure on the gas generator as would a final nozzle. It has to for the gas generator to have a performance similar to the aero engine from which it is derived.
What type of engine would you consider an APU to be? A turbo shaft? Straight Gas generator?
It's a small gas turbine engine connected to a load - an electrical generator and, maybe, a hydraulic pump: it's a turboshaft. A gas generator produces ..... gas (ie, hot air).
An APU might also have a compressor offtake bleed, but that's a possible additional and secondary function.
the engine designs that mr jayz has listed are all "axial" gas turbines, an APU is a smaller "radial inflow" gas turbine, as graham mentioned is mounted to an output shaft that spins a gearbox with the oil pump, fuel pump, a generator, starter and maybe more accessories in some (?). they are more efficient in low horsepower applications that their equivalent axial counterpart for some reason an idiot like i does not compute but it seems to be 1000hp (???) and below, so APU, start carts, small helicopters and a few small turboprops, jet and fire boats. some have multiple stages and the line between some of the older axial designs and radial kind of gets blurry in some designs i feel taking characteristics of both
hmm i think mr jayz refers to them as centrifugal vs axial which makes sense, maybe just the manufacturer that i am familiar with refers to them as radial inflow (ze germans) ?
I appreciate the contribution, but as schematic engine layouts go, a turbojet with a centrifugal compressor is no different than one with an axial.
To put it simply: 'A turbine is a part in a turbine engine'
For a gas generator it does make me wonder if a direct drive through a reduction gearbox would be more efficient? But I guess the wear and maintenance would be higher.
It is done that way with single shaft engines. They have different turbines.
The disadvantage is it takes huge power to get them started.
The TPE 331 is exactly that, it's a turboprop engine with a single shaft and reduction gearbox. They're very popular engines and because it's direct coupled and runs at 100% all the time they are extremely responsive (adjust the prop pitch to adjust power extracted, engine is running at 100% all the time)
"I know you think you understand what you thought I said,
but
I'm not sure you realise, that what you heard, is not what I meant"
-Quotation from Alan Greenspan-
I know you think you know what I think, but you don't understand that there is no way you understand what my understanding of my thinking is, if you get what I'm saying. That's what I'm thinking right now.
@@AgentJayZ Exactly, etc, etc, etc, :)
p.s. I love what you are making,
your work is fantastic !
thank you.
It's even more fun at 1/4 playback speed 😂
It adds an alcohol induced air to it 😜
Question how efficient is a turbo shaft engine in comparison to a piston engine? Why I ask is I've seen diesel engines converted to run on bio gas. I would have thought a turbo shaft would be more suitable for generating power for a electrical generator.
Ps love your dedication from NZ
At full rated output, they are about equal. As you lower the power setting, the piston engine reduces its fuel consumption accordingly. The gas turbine is very fuel inefficient at idle and part throttle.
A major reason they are not used in cars and trucks.
@@AgentJayZ thank you would it be true that service times and costs would work out cheaper in the long run. I just wounder why they use piston engines to power the bio gas power generators seems to be something a turbo shaft would do better and cheaper in the long term. These things run 24/7. Or is it a problem with burning methane
Methane is near perfect fuel for a gas turbine engine. The managers and accountants are the ones who decide what gets purchased and installed. There are many considerations that go into choosing a prime mover.
For one example, if you have ten piston engines running on natural gas and rated at 1,200 Hp each, driving pumps or generators, you have flexibility in being able to shut some down in response to low demand, and you keep 90% of your capacity if one needs to be repaired.
To change all that to one gas turbine/PT combo, rated at 12,000 Hp is a lot of expense, and now you are only more efficient at full output, and if for any reason it fails, in the best case you can get your spare engine in within about a 24 hr shutdown, during which you are not producing.
Or you can get a replacement shipped and installed in a few days.
Worst case: It's your only one, and the repair will be a turnaround of a few weeks. Not including shipping.
Spare engine stored on site?
How much does that cost?
...We'll talk...
@@AgentJayZ or instead of 4 big arse piston engines you run two smaller turbo shaft
Endless choices, but switching cost a fortune. Once you've built an installation, it pays to keep it running and not change it.
this guy gives me very strong Rodney McKay vibes
When you say to me directly "this guy", who are you talking about? I don't think you understand how comments work...
@@AgentJayZ maybe not, I wasn't saying it you directly. I didn't actually expect you to read it. Now that I read more of your comments I see the confusion. Your comment section seems to be more of a forum of people asking you questions. Whereas other comment sections are people talking among one another about a video. My bad.
Hope you weren't offended by my remark there. I meant it in a good way. It's just about how you talk and explain things with very obviously a lot of experience. It's nice to listen to. Would love to see some PT6 content as a king air pilot! If you ever encounter one, doesn't seem to be your niche. 😅
If somebody says "well, actually ..." in person, they're just belittling you for a minor pedantic thing. If they're beating you over the head with a textbook (or frantically looking for one), you were probably massively wrong. This video is the latter.
I saw a few of the latter during my time at the newspaper, e.g. the copyeditor yelling "NO! Bad reporter! Only Mark Twain gets to spell things phonetically in a stupid regional accent, look up the CORRECT spelling of 'barbed wire'!" while threateningly waving an AP Stylebook* open to said page.
(Said reporter wrote "bobwire" for the spikey cattle fence.)
*every reporter is issued one in journalism school, and expected to keep up with updates or buy the new edition. The '99 model I inherited from that editor when she finally got tired of making margin notes and got a new copy was up-to-date with her new one. OFC it's changed since, so mine has even more notes and she's probably got a newer one and passed down the now-heavily-annotated copy she got to replace the one she gave me.
Why do larger jet engines use axial compressors instead of a centrifugal compressors.
In Jet Questions 60, we look into that. Here's a link to that one: th-cam.com/video/n61oL__sqVs/w-d-xo.html
@@AgentJayZ
Refere to the JZ lexicon. Just love it!
😂👍
Thank you very helpful. Impressive that you remembered the exact video. And sorry for asking an old question. I’ve been watching your channel for around 3 or 4 years and never saw that video.
I didn't remember anything. I did what I always suggest: I used the search feature on my channel page. I typed "centrifugal" and hit enter...
@@AgentJayZ
🤭👍 Thats wath i vere refere to, the JZ lexicon. 😎
I'm curious if you, AgentJayZ, have commented on the SR-71's J58. Granted, it's got some ramjet blood in the mix somewhere, but I'm particularly interested in your easy to understand explanation of the common claim that around 54 percent of the total thrust of the engine system is provided by the inlet. To the uneducated, they make it sound like it's "Hoovering" itself through the air. Thanks.
Whoever said that was mistaken. No thrust has ever been made by an inlet, or a compressor.
Also, there's no such thing as suction. See my videos about that.
What they probably were trying to talk about ( and failing (what a surprise)), was that at higher speeds, all of the compression of the air needed for combustion is provided by the aircraft inlet, and the axial compressor, and the turbine needed to drive it, can be completely bypassed, and shut down.
This is what happens in the J58.
It is a turbojet up to a certain speed, at which point the inlet adjusts to take advantage of shock waves to compress the incoming air. That compressed air is then directed through bypass tubes (not the conventional definition of bypass) which lead directly to the afterburner section... which now become the combustion section of a ramjet.
For these reasons, the J58 is called a turbo-ramjet.
The oft-described and nearly always misunderstood condition called the "un-start" is something only experienced by the J58, is when the aircraft reduces speed to the point where the core, or the bypassed portion of the engine... which is a conventional turbojet...which was shut down and now needs to be started again... fails to start.
It is a very interesting engine, and unique in aerospace.
Now, why do I dislike the J-58?
I don't, but I am quite tired of the hundreds of spec sheet armchair experts commenting on my J79 afterburning test run vids. They always say "too bad it's not an SR-71"
To which I usually reply "Would you even be able to tell the difference?"
Or : "The SR-71 is an aircraft, and we don't test aircraft, in case you haven't noticed."
Or: "The J58 is a large, afterburning turbojet, which propels an aircraft to over Mach 3. The J79 is a large, afterburning turbojet that propels an aircraft to over Mach 2.5. My apologies for disappointing you."
So, glass 5% empty, or glass 95% full. I'm a little tired of these complainers not realizing that nowhere on TH-cam will they find as much up close and detailed footage and information of large afterburning engines for supersonic aircraft, as they will right here, on my channel.
Melonfarmers!
@@AgentJayZ I've watched your videos on suction and was going to incorporate that into my question, but then realized that after watching your last video, I should probably keep my post as brief as possible so as to not use incorrect terminology in the formation of a question, further confusing the issue. :) I've seen great videos describing how the J58 functions, and in combination with your videos on suction, came to the conclusion that the "thrust provided from the inlet" claim was almost certainly incorrect, or a clumsy reference to the source air for the bypass tubes. Thanks for clearing it up.
I'm in no position to comment on the J58 but, as AgentJayZ knows, I did help keep an even bigger supersonic engine turning and burning for some years. So here are the facts, in terms of the nett forward load distribution, as a percentage, for the complete Concorde propulsion system at supersonic cruise:
Forward load on the airframe-mounted intake structure - 63percent
Forward load on the engine thrust trunnions - 8percent
Forward load on the airframe-mounted final nozzle system - 29percent
At 58,000ft, the ambient air pressure is about 1.2lb/sqin, at a temperature of -56degC. In supersonic cruise at that altitude, the pressure at the intake face of an Olympus 593 was about 9lb/sqin, at a temperature of 127degC. The total thrust produced by the complete powerplant was around 9,000lb, 63percent of which was exerted on the intake structure. More specifically, there was a forward load on the structure equivalent to 75percent of the total thrust, less a rearward load of 12percent of the thrust on the forward ramp of the intake.
With that level of pressure rise in the intake, there must be a nett forward load on the intake structure. As it it is contributing to propelling the aircraft through the sky, I can only use the term 'thrust' for this and for the other forward loads.
Now whether you wish to regard the force as thrust being "made" by the intake is, perhaps, a matter of semantics. That the Concorde's complex intake system wouldn't work without a two-spool turbojet (or something similar) turning and burning behind it, to produce the necessary heat release, is indisputable.
What is your opinion?
PS And if anyone ventures to suggest that the Olympus 593 was "inefficient", in its day, in supersonic cruise, it was the most efficient simple-cycle heat engine on the planet, in terms of thermal efficiency. Having said that, the machine it powered wasn't the most cost-effective way of transporting 100 items of self-loading cargo across the Atlantic - but it was the most impressive (been there, done that!).
So, by your little table above, if the engines of Concorde were ejected, the aircraft would keep flying while losing only 8 percent of thrust, and be carried forward through the air by only the aircraft inlet ducts?
I am unable to comprehend.
Also, the engines I deal with have a final jet nozzle, that fits into what is basically a hole in the back of the airframe.
I have never heard of an airframe mounted nozzle.
I have always understood that there are both forward and rearward thrust forces on the main rotating components, supported by the thrust bearings, and these forces are different than the net thrust output of the engine as a whole... which is always forward, and is 100% of what propels the aircraft forward.
Is this a case of me having different definitions of terms?
@@AgentJayZ I remember, years ago, a very senior engineer at Bristol quipping that, when Concorde was in supersonic cruise, the 593's turbomachinery could be thrown away. However, as I've already stated, there still has to be something there to burn the fuel - and the pressure rise across the compressors is still needed to add to the pressure rise in the intake.
Take a look at the 593 I believe you may have in Fort St John, or find a cross-section on the internet. You won't find a flange on the exhaust annulus extension, to which a nozzle can be bolted. The hole that the back end of the 593 fits into is the complex con-di nozzle, which also doubles as a thrust reverser. There's no golden rule demanding that the nozzle has to be bolted to the engine. What's wrong with a huge piston ring seal? Industrial and marine gas generators don't necessarily have to be bolted to their power turbines, do they?
Yes, there are large forward forces on the compressors of any engine, and large rearward forces on the turbines, which are times greater than the nett thrust of the engine. As we both know, the thrust load on the location bearings (as Derby very correctly calls them) is the difference between the two opposing forces on the compressor and turbine rotors and is not related to the engine thrust. I've mentioned more than once that I was involved with the design of an engine with a rearward load on its HP location bearing.
I'm sorry, but you're going to have to get your head around the fact that a supersonic powerplant is much more than just the turbomachinery and a combustion system - I had to.
PS: Has it occurred to you that you've just done to me what some of your disbelieving subscribers all too often do to you (and to me)?
So for clarification, what is a turbine then? Is it a single stage of an turbine engine or is it the stack of stages that moves as a whole? thx
A turbine is an assembly that can have more than one stage, all moving at the same speed because they are all attached.
@@AgentJayZ I'd think that the rotor and the stator move at different speeds when the turbine is operational...
They do! The stator, or more correctly, the stators, are called that because they are stationary; the do not move. Anything moving at all is moving at a different speed than a stationary object, eh?
Maybe you meant the compressor and the turbine... of the gas generator.
See how the proper names are important?
@@AgentJayZ When I said "stator" I was referrring to the not moving part(s) of the turbine. So far I know most turbines can't operate without these and hence I consider them to be fullworthy parts of the turbine, but you said that all parts of a turbine move at the same speed. So I kind of noticed sort of a contradiction.
Yeah, again... knowing the right terms is essential.
People are going to say this is pedantic, but fuck them.
The turbine section of an engine consists of the outer cases, containing the turbine stators, often called nozzles, or turbine inlet guide vanes, or even nozzle guide vanes (all are correct), and also containing the turbine assembly, which consists of the main rotor shaft, to which are attached the disk or disks, which hold all the blades. The bearing supporting the rotating shaft is usually not in the cases, but in an adjacent supporting structure, called a turbine bearing housing in a turbine frame.
Everything attached to the rotating shaft, rotates together. Everything connected to the turbine case, is stationary.
So, the turbine is a moving assembly, that makes up part of the turbine section. The section includes the stators.
I hope this helps clear things up.
All those people commenting below how pedantic I am being, please return to line 2 and read it out loud... twelve times.
So :
- a turboshaft has a power turbine driving the load
- a turbo fan as a power turbine driving the fan
- all gas generators have at least one power turbine driving the compressor
Good/not good?
B+: the turbine driving the compressor is not called a power turbine. I know that conceptually it can be thought of as one, but as part of industry standard nomenclature, it is only referred to as a turbine, or as the compressor turbine.
Could call it a core turbine, or the (LP or HP) turbine driving the (LP or HP) compressor.
To call it a power turbine driving the compressor is incorrect, but pros will know what you mean.
To call it a power turbine, will be inviting questions and corrections from the pros.
I endorse what AgentJayZ has told you. Consider yourself corrected by a professional.
Thanks! I hope everyone by now knows that you are a professional engineer, who spent a career in the field of designing gas turbine engines at none other than Rolls-Royce Aero Engines.
I consider your opinion on this subject to be of the highest possible value.
@@AgentJayZ Not just aero engines: that was the second half of a career lifetime in gas turbine engine design. As you already know, the first half was in the design of aero-derivative, industrial and marine gas turbine engines, some of which you have shown us.
Just the other day read another of those lazy people talk about a "two-piston airplane". And I was really wondering if he was talking about a little half-VW engine in tiny single-seater experimental aircraft (these exist), but he actually meant a twin-engine aircraft with two piston *engines*. Or others that tell me "it's the same thing" when I point out that a turboprop is not a jet engine, because the jet exhaust is not the main propulsion.
Propfan (unducted fanjet) seems to be missing.
Yes, maybe, but take a look around. That was an experiment that was never put into production.
If I was to include that, I would have to include the ramjets at the blade tips of the Fairey Rotodyne.
Hmmm, I think I need to make a pt.2...
@@AgentJayZ hey agent jay I had a question. Why don't large airliners use adjustable nozzles like jet fighters? Or do they and maybe they're just not visible? I love this video by the way I don't know much about jet engines but that's why I watch. In fact I would assume that the majority of your audience has never set hands on a jet engine. Or maybe I'm just an outlier but I appreciate all your work. It's one thing to explain something but it's another thing to make them understand. I really hope you have some apprentices
Piston Engine or u can say Reciprocating engine.
I prefer "rattlebox".
@@AgentJayZ
That were a new one for me. 😂👍
@@AgentJayZ and considering an optimistic efficiency of 33% there's likely as much power in the exhaust gas as out the crankshaft
@@fuzzy1dk - Thus turbochargers.
@@wickedcabinboy or going even further, the current F1 cars have a generator connected to the turbo, the Porsche 919 that have a generatoir connected to an extra power turbine in the wastegate exhaust, to generate electricty for the hybrid system
so Technically when talking windmills, its Mother nature that's the generator?
Technically a wind turbine harvests energy from the wind. The machine does not have a gas generator.
The gas generator would be the sun, or mother nature. You'll notice your mistake there, in that you omitted the word gas. A wind turbine does have a generator, an electrical generator.
This is an excellent example of the importance of using the correct terminology.
So, Anti Decepticon, you are both correct and incorrect, depending on what you meant to say...
@@AgentJayZ But he was talking about wind *_mills_* which do not have an electrical generator, they mill grain into flour :-)
Gas turbine...is the core for turbojet, turbofan, turboprop, turboshaft, industrial & marine power plant...
Hold up…. A turbine engine is essentially a huge turbocharger
yes, but with some super fancy plumbing attached as well
That's a very bad way to describe it.
@@AgentJayZ why? From my understanding it just uses exhaust gas to spin the propeller and that exhaust gas gets pushed back into the engine, does it not?
@@thebmxchannel1516 NO! Your understanding is a total misunderstanding.
@@grahamj9101 this explaination was too brief for me then
build 2 × Soloviev D-30-II turbofan engines, that runs off of diesel
ah, and I thought you was just going to confuse things and talk about the aft-turbo fan engine
We actually had a few CJ805-23s, but sadly, during conversion to industrial gas generators, all the weird parts were thrown away. It was before I was hired...
I am in telecom and frequently hear "Customers 4G isn't working" where they actually mean mobile internet. My reaction would and will always be: So 2G and 3G are ok? Which usually can't be answered.. Then I know they mean mobile internet.
If I was calling you, I would start off with "I have no idea how any of this stuff works, and I hope you can help me..."
@@AgentJayZ Thx that way I know what I'm dealing with and I forgive you in advance for saying things that make no sense at all ;-)
@Sheila Walker It's a good thing people can't just buy a jet generator.
Oh my - you must have had one helluva cringe experience with a 'layperson(s)' to need to make this video.
Great job as usual though, nice pictures - great comedy.
One? More like thousands!
@@AgentJayZ And some are STILL ready to correct you on what you said in the video
Beekuz wurds mater.
@James Myers - I'd give you two thumbs up if I could.
Your explanation on why they are so inefficient isn't quite right. The velocity of the aircraft can actually exceed the exhaust gas speeds because these are reaction engines and work by throwing particles of air out the back end and the result is an equal force in the opposite direction.
It's also the reason they become more efficient at altitude once you already have speed... Also why they become less powerful too. There's less air. Less air equals less fuel. Less fuel burned equals lower reaction force.
"A simple review"... remember that part?
@@AgentJayZ haha, yeah. But I like more complex reviews 😝 tease tease
In an air-breathing propulsion jet engine, whether it is a turbojet or a turbofan, the forward velocity of the aircraft it is propelling can never exceed the rearward velocity of the exhaust jet.
There is something known as the Froude Equation (other Froude Equations are available), which demonstrates that, for 100percent propulsive efficiency, the aircraft forward velocity equals the rearward velocity of the jet efflux. However, this would mean that there was no momentum change in the jet efflux and, consequently, no thrust.
If it is impossible to achieve 100percent propulsive efficiency, it's certainly impossible to achieve greater than 100percent.
@@grahamj9101 hmm, interesting interpretation. I didn't quite get the same interpretation from Froudes equations. There are several and I'm guessing that you're referring to Froudes propellor theory?
@@SupernovaSpence I am referring to the Froude Equation for propulsive efficiency, which I would have copied down in my lecture notes as a first-year undergrad in 1963-64, as follows:
ηp = 2V/(V + Vj) x 100, if you wish to express as a percentage.
Translating this into English for other readers, propulsive efficiency equals twice the forward velocity of the aircraft, divided by the sum of the forward velocity and the rearward velocity of the jet efflux.
It's not a case of my personal "interpretation": you will find it in any reputable gas turbine theory textbook. I just happen to have 'Jet Propulsion' by Nicholas Cumpsty open at page 24 in front of me. You will also find the equation on page 2-29 of 'Aircraft Gas Turbine Powerplants', to which AgentJayZ has often referred, where it is expressed as:
Peff = 2/(1 = Vf/Vi)
I repeat, a propulsion gas turbine powered (ie, a jet-propelled) aircraft cannot fly faster than the velocity of the jet efflux of its engine(s): it's very basic physics.
PS: And I do have a career lifetime in the design of gas turbine engines, industrial, marine and aero, to back me up.
Since when are diagrams right to left?😂
You need to possess the ability to interpret diagrams no matter what their orientation, as well as be fluent in both metric and imperial units of measurement. With those basic minimum requirements, I'm afraid you will only be considered for custodial positions at Jet City.
@@AgentJayZ - Hey, everybody's got to start somewhere. I'm a nurse and I had to start out by wiping butts and giving baths.
The convention of having the engine intake on the left and the exhaust on the right is just that, a convention. At least, it is recognised on both sides of the pond.
convert a gas generator turbine engine to run on pulverized coal
Only conversion necessary is to the combustor and fuel control. It has been done.
@@AgentJayZ i want to see it done
@@AgentJayZ also turn it into a generator that generates power
Go look for it, then.
Yes, it's been done - but there's a problem, a big problem. Coal produces ash, which can be highly abrasive and has the potential to grit blast the turbine aerofoils. And, if it doesn't do that, it will tend to deposit on the aerofoils and both effects will degrade their efficiency.
Have you ever seen the pulverised fuel ash produced by a coal-fired power station?
16:05 How dare you, it's a knowledgeable non binary person
I couldn't think of the counterpart to fellow. I knew it wasn't "chick" !