Controlling Fuel Flow in a Jet

Jet fuel nozzles, ignitors, combustors, fuel lines, a look inside the combustor of a real turbojet engine, and I try to explain how it all works.

[@SUN_2607]

The amount of work and research gone into designing every aspect of a jet engine just blows my mind. This is not just a piece of machinery, it's a work of art.

[@conkerconk3]

yeah. makes it a nightmare for anyone building one though lol

[@randomamericansoldier8586]

For me, any piece of machinery is a piece of art.

[@moned90]

As an engineering student. i love all you vids! Thanks!!

[@zapfanzapfan]

"I don't know how they work", sounds like a good start for a video on fuel controls :-)

[@biggen2ooo]

I am a retired RF design Engineer and will never work on a jet engine but I love the videos and the time and detail you put into them. I just cant get enough I am sure you love your work and its easy to see that you are very good at what you do. Thanks for all the effort and time it is greatly appreciated. please keep the videos coming.

[@AgentJayZ]

@xxJohn1977xx We are using Mobil Jet II synthetic turbine engine oil. These engines are dry sump. Each bearing has it's own sump that is emptied by its own scavenge section of the main oil pump. That pump has three sections: one pressure element and two scavenge. There is also a separate scavenge pump for the gearbox. The oil supply in out tests is that silver box you see under the engine. Most installations have a large remote reservoir holding a hundred gallons or so.

[@scottmarshall6766]

"I don't know" (how they work)" The 1st step to "here's how they work". I could work alongside you sir, and am sure we'd get along fine. Thanks for the great videos, you make it look easy. Scott

[@jaishetty8586]

you teach better than my professors did. been watching you for three years now. learnt most of my lessons from you. thank you. keep it up.

[@vf84tcat1]

Excellent video. I've been a pilot for 43 years but never saw the level of detail for the operation of the turbines like you show here. Thank you sir!

[@ksben0016]

Best explanation of the operational principles of a modern jet engine. I always thought the fans were electrically driven - but the fans are actually impelled by the combustion of fuel as it is expelled from the rear of the combustion chamber-forcing air into the chamber through the turbine fans as it is being compressed through volumetric reduction. Incredible technology-very counter intuitive.

[@sreenivasanm4303]

You are a gifted person. Amazed the way you explain everything in great detail. It is a great service to the engineering students and amateur aviation enthusiasts.

[@VanguardDragon]

Wow what an amazing and interesting job you have, thanks for sharing it with us!

[@alekseisorokin4723]

Thanks for your work! There is no valve in the fuel nozzle, but it's needed to manage fuel flow supply. It's related to fuel control system

[@rajatm625]

whenever i sought to check engine components, especially the combustors, i cudnt!..bt nw, i feel happy to c 'em....A Bigg Thank You to Jay!!!...

[@billautotech]

Agent,I suspect you really enjoy making these good videos and you enjoy educating others There are many excellent technicians out there,but not many of them have the ability to to explain these concepts in an informative and entertaining manner.

[@davidalex4844]

Yes you are right despite of the complexity of design and manufactiring still even Rolls-Royce never made such a detailed video like you do God bless you...

[@CC--le3tn]

Wow! I never really knew how pilots control the power of the engine and I couldn't find any information about it until now! Very nicely and clear explained. Love it!

[@Laleea8498]

Wow, in 2024 am learning about jet engine and agentJay help me understand alot about jet engine thanks.

[@roberthakizimana7286]

Thank you sir, your explanations are wonderful ......you make it more interesting with I don't know how it works

[@bartdereu9267]

I truly love all of you vids !!!

[@renatomartinez3183]

AgentJayZ i'm highly impressed of the scorch that the starter fuel line does,this is a very instructed and comprehensive video 😀,tons of thanks.....

[@SOU6900]

Like watching your videos and learning stuff about jet engines even if I won't use what I'm learning.

[@billyost1479]

You explained it perfectly.

[@WasimAkhtaraircraftengineer]

Your videos are amazing, i got to learn and see the actual combustion chamber components in your video for free which i did not get to see so clearly in a 3 year degree course in my university, respect top man

[@Xevious5]

Truly fascinating stuff. Thanks for your time, effort, and honesty!

[@pesciro]

@AgentJayZ Thanks for all the work you put into making this videos. They are absolutely cool and informative.

[@AgentJayZ]

@pjvenda I've just been doing some reading on combustor design, and as always, it's a bit more complicated than I present in this quick, easy video. Although there is no control for fuel-air ratio in a jet engine, the ratio in the combustion zone does change on its own. Because of the interaction between fuel spray patterns at differing fuel pressures, and air density at different compressor discharge pressures, the air-fuel ratio changes from lean at start to rich at full power.

[@AgentJayZ]

@mwroush Once the fire is lit, it stays lit. For safety, during takeoff, airliners keep the ignition sparking just in the one-in-a-million chance the flame might be lost. Otherwise, when you see a jet flying overhead, the ignitors are turned off. If you watch my test videos, the ignitors are turned off before the start cart is shut down. They are only used for a few seconds to start combustion in the engine.

[@AgentJayZ]

@Morkvonork Many of the engines we work on are fuelled with natural gas, and those ones we test with propane. This engine runs on jet fuel, so it will be tested with Jet A.

[@Ratlins9]

Great video, hands on illustration so much better than drawing pictures or showing charts. Thanks.

[@Gkuljian]

I'd love to see a video on the fuel control system. It looks mindbogglingly complex. (Also, another boggler is how much of this technology was done with slide rules. )

[@lightbulbout]

These are the best videos on the internet.

[@awsshahwan645]

All your videos useful U r great teacher

[@PABU427]

Agentjayz I was hoping to learn more about HMU's so your final comment made me laugh. Still very informative. Great job.

[@AgentJayZ]

This engine has a large electric starter. Some larger engines use air-turbine starters, because an electric motor large enough to start them would weigh several hundred pounds. Modern turbofans are going back to electric starting because they have a smaller "core" to spin up for starting, and because electric motors are getting much more powerful for their weight.

[@MattH-wg7ou]

Do any turbojet/turbofan engines use a fully annular combustor section or are they all segmented like this one? Man Im so grateful for this channel! It teaches me so much about how these things work that we didnt get in academics.

[@AgentJayZ]

If you go to my channel page, and type combustor liner into the search box, you will find a series of vids I've made about combustor liners and cases. If you look at them, you will see the evolution from old style single can combustors like these in the 1940s and 1950s, through cannular designs in the 1950s, through to the modern full annular design, which almost all engines use today.

[@MattH-wg7ou]

@@AgentJayZ awesome! Thanks!

[@NaveedKhan-to6ws]

Sir u r doing best work for all us.i love your all video.

[@dinosaurcomplaints2359]

When you talk about high pressure air, mention percentage of oxygen and Boyle’s law of partial pressures. Same principle applies to deep sea divers. Good video. I learned sumtin’

[@carlosalbertotorreszuniga3549]

Thank you for sharing your knowledge with the rest. You are a great person. Greetings from Mexico.

[@hemiongebr5286]

Thanks Sir , I have been try to finding this for 20 years .

[@TAShannon1]

You sound kind of like Robin Williams when you talk (Rest his soul!) Thanks for the videos!

[@Dieguito257]

Thanks for posting this awsome video, I'll have an exam about jet engines this coming thursday and now I understand them better.

[@SirDeanosity]

Him pulling that fuel nozzle out of the engine reminded me of when I replace the fuel pump on my van. Couldn't believe all the stuff fastened to one mounting plate.

[@tomuchfunwithgas846]

Thank you, and down the rabbit hole I go. I like to learn.

[@mwroush]

Hello and thanks again AgentJayZ. I too learn a lot from your videos. It sounded like you said that only some of the combustors have ignitors and that the hot gasses communicate via the interconnectors so do the ignitors need to run constantly or once the fire is burning in the combustors, they stay lit as long as there is fuel? A cool view you gave us of that nozzel being fitted into position.

[@MrLohatoolvebyte]

I found it interesting that the natural gas fuel nozzles look almost identical to Halon fire suppression system nozzles. That surprised me as the density of the gases involved are so very different. That's from my engineering back ground in fire suppression and detection systems. Interestingly there's lots of useful cross over science for me in what you're teaching. I find it fascinating and thank you for your excellent efforts explaining all of the nuances. I am much richer for it. Plus quite frankly you make it fun too. I work for the same university that the creator of the famous Lockheed Skunk Works did his ground breaking wind tunnel research in just before WWII. It's still there, I've been in it. We have a whole section of one of our campuses dedicated to aeronautics and an aviation museum with cutaways of turbojet engines (we even have a GE J-79). I didn't understand them until I heard your explanations, now they make perfect sense, especially the combustor sections. The light went on over my head when you explained the design philosophy of applying cooling air. Your insistence on precise language is absolutely spot on. Brilliant! :D Thanks again, Ted N. from Ann Arbor, MI, USA

[@Pontiacman1964]

Thanks for this video. I knew how jet engines worked, but never knew how they were regulated. Very informative! Oh by the way, my dad's family is from Canada; Chatham/Kent, so that's another plus.

[@AgentJayZ]

@rschulemann The radial drive shaft is ised to supply power to the gearbox to drive the accessories. The difference in industrial engines is that there are less accessories driven. This engine produces about 10 thousand Hp.. in the form of hot, high velocity gases exiting the engine... to be sent through a separate power turbine, which then turns a shaft.

[@garykusnierz2108]

Wow you’re human after all. Thanks Jay !!!

[@prayerbabies]

You have an education superpower. Thanks very much for the learning and the inspiration. Wondered if you had thought about endoscope cameras - cheap now and provide stunning internal views of tight spaces...

[@AgentJayZ]

@ProjectWolfDragon This is all true, except the last bit. The only engines I know of that use some sort of heat-transfer evaporation feature for vaporizing fuel as it is fed to the combustor are the Tubomeca helicopter engines, and the Orenda Iroquois. All other large engines spray the fuel directly into the burning zone. Some of the most modern airliner engines incorporate "pre-mixing" zones for air and fuel, but even the manufacturers don't call them evaporators or vaporizers.

[@AgentJayZ]

... combustor and compressor.... but I really like your line of thought !!

[@welshpete12]

As always very well done. You are an excellent teacher .

[@aagguujjaa]

So awesome.... No textbook matches seeing this

[@ryanhat5328]

awesome videos i've always wanted a better understanding of how jet engines work. Thanks

[@squid0013]

That nozzle vane combo looks just like a volcanic heater unit flame gun. Just used to power a jet as opposed to heating fluid to heat a barge

[@a1sloth1]

Excellent instruction, thank you.

[@tonyneyra]

excellent description

[@DedhedWaldo]

Love your turbine engine videos. Makes me want to learn to say "aboot" and finish sentences with "eh" so I can go to Canadia to lean to work on them, haha. I'm more of a motorcycle guy but a turbine motorcycle would be awesome!

[@richardlevy8699]

Very cool. It's not very complicated at all. I'm interested in the use of bypass air and air pressure bearings.

[@AgentJayZ]

Bypass air is ejected out the rear to create thrust. Air pressure bearings are not used in any engines I have worked on or had any contact with.

[@greghelms4458]

Would have loved to be in on all the trial and error to get a viable jet engine. Air, fuel, materials, power, with acceptable fuel usage, no melt, etc etc. etc. Beautiful engineering. Even on those old fifties models.

[@AgentJayZ]

You can re-live it all. Read the autobiography of Gerhard Neumann, the GE engineer who led the team that developed the variable stator system. He called the book "Herman the German". I guarantee you will like it. If you don't, I will buy it from you.

[@greghelms4458]

AgentJayZ Thanks man. Sounds like a good read for sure. Have a great day and keep up the cool content.

[@zizomanism]

جازاك الله خيرا على العلم اللذي تقدمه

[@Tomasu321]

@AgentJayZ I get positively giddy whenever you post a new video!, absolutely fantastic informative and interesting. Really makes me want to work with this.

[@colemcleod941]

It would be really cool if you got a snake attachment for the camera - or just a mini-cam on a flexible wand - similar to the one your mini-flashlight is on - to continue that shot into the Combustion chamber - or any other part of an engine that's hard to get to

[@Carlitosway211]

Those are amazing looking pieces of engineering! I'd love to work on one! Looks nothing like a big block! :-p

[@sarahcurry5717]

Love your videos!!!! I have no knowledge with these and enjoy your through tutorials good job!

[@kennethcohagen9037]

Wow, I didn't expect an answer that fast. Thanks, I'll look that up. P.S. I've enjoyed the videos you've done that I've discovered recently. Thanks for taking the time to do them. It helps a lot of us enthusiasts understand what's going on under the hood, er uh cowling. ;)

[@gfly7100]

could you please do a video on the actual fuel control units. yes as much as you've mentioned that they control the fuel metering, anything with some kind of illustrations would be of great help. Once again, thanks for your time.

[@steve4316]

Fuel injectors have nozzles but it is only one part of the whole injector. It also has a coil, a seat, a body, and a valve. The nozzle, as also on the turbine engine.

[@Tricky4Trick]

thanks you for all your effort I all ways wanted to know whats inside the case of a turbine

[@FrontSideBus]

You guys in the shop should have a little competition to see who can make the most powerful engine out of a car turbocharger :) I reckon you'd win.

[@igorcastro747]

Thanks for your explanation... Jay

[@RedPillRachel]

Wow you're amazing, thank you so much! I'm going to download this whole channel for study offline, and start to think about aircraft restoration as a possible future hobby! I've always been fascinated by jets, but I had no clue where to start, and there seems to be a lot of elitist gate keeping around this area of technology! Well you open gates by making these and you are very much appreciated for it! A random video of a test fire led me to these videos of yours, for once the KZbin algorithm has given me something useful! Thank you again, much appreciated! I hope your company does well, you deserve the best!

[@AgentJayZ]

I guess if you want to download my videos for repeated watching that's OK... but please don't copy and share them. That denies me the tiny amount of revenue that helps me get by... Thanks for understanding!

[@RedPillRachel]

@@AgentJayZ I would never do something like that, I only share when asked to by the author, I meant in case they are taken down or my unreliable internet stops working, or god forbid, start again after Corona or similar event, with whatever is available, that's why I got a bit excited, you make it understandable and real to me for the first time. For the theory I have books and my math degree. For the practical I will have this. For my grammar, I'm sorry, lol. Thanks for replying, Rachel

[@adenmhed7924]

Your videos are the best !

[@Muuip]

That was really interesting, thanks for posting! Nice presentation!

[@matube73]

Another great vid Jay. Your editing keeps getting better. Cheers.

[@osama09128]

we appreciate your effort thanks alot

[@AgentJayZ]

@joelvh1 The only thing controlling the air fuel mixture is how much fuel is sprayed in. The mixture is always the same, because there is always more than enough air. That's the whole point of this video. There is no such thing as mixture control with turbine engines. The VSV's manage the direction of incoming air so as to avoid having the compressor blades experience aerodynamic stall.

[@holyteejful]

Hey, these videos are awesome! I appreciate your desire to share your knowledge and help us learn. Keep up the great, informative videos!

[@davidalex4844]

Thanks for nice and informative video...

[@AgentJayZ]

@krbruner The flame travels to all the other combustors essentially instantly. If there was any banging or roughness in starting, these engines would have an ignitor for every fuel nozzle.

[@romanescalera7752]

Que chingon eres señor. Gracias por tus videos

[@ADAPTATION7]

It would be nice to see how the fuel control module works. Now that I know that the IGV are linked to it. :-)

[@AgentJayZ]

It's a hydro mechanical computer, contained inside an aluminum casing. You may as well wish to see how a computer's microprocessor works.

[@Les__Mack]

Thanks again for these videos! I am enjoying them. :-)

[@AgentJayZ]

@elcuervo1984 Occasionally we experience icing of the inlet during our testing. I've only seen ice build up on the leading edges of the struts in the front frame. This happens at just above freezing when the humidity is high. On days like that when we are having a test, we place one person where they can watch for ice in the inlet, and if they see it, we stop the test. The reason is the engines we work on are not equipped with anti-icing capability.

[@AgentJayZ]

Returning to service in a Canadair Sabre6 as an air-show demonstration performer

[@kinsley2108]

We did an overview of a hydromechanical FCU. We traced the inputs and outputs to a 3 dimensional cam. (Apparently the designer lost his mind). They said as long as you understand that there is a computing side and a metering side to the cam, don't bother with the rest. It's too complicated.

[@AgentJayZ]

These are hydromechanical, and also have a 3-D cam inside. It looks like a metallic ham bone.

[@kinsley2108]

AgentJayZ it's a genius little device!

[@AgentJayZ]

With all engines, but especially with these antiques, the emphasis is on careful and slow, not quick and powerful. Power tools are great for production if it's OK to break the odd bolt.

[@AgentJayZ]

The stuff from them I've heard, I liked.

[@Blakearmin]

First - thank you for taking the time to make all of these and for answering the few questions I've had. Now for the question: At 8:09 there's a really rough spot on the front end of the combustor liner right where your light is pointing -- Is that from heat damage? If it is, how does that part get heat damage? I understand how turbine blades, and the combustor liner further aft, get damaged but that seems - to a layman - a bit of an odd spot for heat damage.

[@AgentJayZ]

The liner is made of shiny stainless steel. The rough spot you see might just be the ragged accumulation of soot, which is normal for all these old jets. The soot flakes off, and often looks very rough.

[@Blakearmin]

@@AgentJayZ Thanks for answering my question! There's a shadow behind the edge of the rough spot so it's definitely a hole, however it looks to be something that's actually machined into the liner. I went back and watched it again and it's not as rough as I initially thought. It's a triangular cut with two straight edges on it, ending in one of the liner holes - and no flame I've ever seen burns in a straight line. Thanks again for taking the time to answer my question. I really appreciate it!

[@lcambilargiu]

Thanks for your videos! Great stuff.

[@AgentJayZ]

Yes, this is a good comparison.

[@amrraouf9396]

very good video jay z

[@Lsanchez0411]

A great video! Thanks!

[@manuhernz2745]

At Spartan they teach you the hydro-mechanical fuel control unit jfc12-11 by Hamilton

[@craigthebrit1132]

Excellent video...thank you....

[@guidowager]

... great stuff! All your clips interesting AND entertaining!

[@AgentJayZ]

Automotive fuel injectors, modern ones, have an electrically activated valve that stops or starts fuel flow, to deliver a pulse of fuel at or into the cylinder. Jet engine fuel nozzles have no valve, or any other way of controlling flow through them. They are more like sprinkler heads, or spray nozzles, which is why they are called nozzles, not injectors. Hell, the Brits call them burners.

[@steve4316]

The nozzle, as also on the turbine engine, is merely the port for the fuel to spray through. All injectors have nozzles, but not all nozzles have injectors.

[@ahmedsultan3366]

Thanks ! I’ve learned a lot !

[@arthurdog3]

Thank you, teacher !

[@hawaiinnative]

Great video. So the injector is somewhat similar to the "old" fuel injectors on old 1979 Audi or Mercedes car that run on CIS (continuous injection system) as opposed to EFI.