Jet Engine - Explained

I had a request for an explanation of jet engines, so here's my response. There are many videos that explain this, so I'm trying a different approach and including some other details. Also attached at the end is the combustor video link which helps explain what occurs after the air is compressed.
• Combustor - Explained
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[@Nick-xc4fy]

Literally the clearest explanation I could find and it's like 6 years old. Thanks!

[@EngineeringExplained]

Haha very welcome!

[@basselalkhoury7697]

they all use fansy animations but no one provides good clear info like this guy

[@yoali7330]

Lol 😂

[@martinsandoval9330]

9 years now

[@benjamin7114]

11 years now and still the simplest way to set your mind to understand the complexity of a jet engine.

[@EngineeringExplained]

Unfortunately I stick to automotive based videos now. Cheers

[@andrerrie]

Sam Aj indeed, make a suggestion on social media.

[@andrerrie]

I’m subscribed for a few years but Never knew of this video until i wanted to find out how jet engines work lol.

[@EngineeringExplained]

@Aexotica Yes, the fuel is sent into the combustor via fuel injectors.

[@EngineeringExplained]

@TheTerribleSwede Well, I'm no expert on turbine engines. Thanks for the tip; I made this video for a student who wanted help on a project.

[@EngineeringExplained]

Not sure about the pitch, it could be equal with the speeds of the following props increasing, or it could be as you've described, or a mix of both.

[@yummyzerg]

Wasn't the easiest to follow in the beginning, but I'm very happy that I watched it through - this was the best explanation I've had so far. Thanks!

[@EngineeringExplained]

I'm not sure. I don't think so, but if the material was flexible I suppose it could, or if it were controlled somehow to increase/decrease the suction force. As far as I know though, I believe they are fixed.

[@Micknesss]

Wow found one of your early videos mate! Love the hairdo and the wooden framed whiteboard! Your confidence in presentation has grown massively since this vid, you're a natural now :) Keep up the good work

[@EngineeringExplained]

@Aexotica Just like in cars, large turbines can have starter motors that rotate the main turbine to get things started (starts the rotation of the compressor). If it's a small engine, like for a model plane, you could even just put a fan up to it to get it started (or a hair dryer!).

[@EngineeringExplained]

Not sure about the overheating, it certainly creates more heat, but I'm not sure how much of it affects the aircraft. Fuel consumption goes way down though, for sure.

[@EngineeringExplained]

@TheTerribleSwede No, just using it as a demonstration to show how the different stages of the compressor rotate at different speeds.

[@askersatz]

I love your work and really appreciate your knowledge and effort to do this stuff. Thanks, man!

[@viktorrosen4561]

wow this was the best explanation i could find, even though it is 18 years old! Thank you for saving my school project!

[@MH-ve5sz]

This video is so clear! You are a great teacher! I'm a pilot, preparing for initial training on a jet.

[@kielerrr]

These whiteboards should be framed for how easy they are able to summarize and make understandable very complicated subjects..

[@mehdibouchebri6866]

+Engineering Explained can you please make an updated video ?

[@vishveshtadsare3160]

This is why teaching method hasn't changed in 200 years. I have seen many videos on jet engine working where they explain with animation but this one I understood the most. Thank you.

[@josephburton92]

Thank you very much I’m taking an Airframe and Power plant test tomorrow and i really couldn’t wrap my head around how it works. I really appreciate it

[@yarbooa]

Great explanation! at last, a straight forward, no fancy CGI, thx.

[@EngineeringExplained]

Likely some arms that reach across and hold it on bearings.

[@topcrocsuser]

This dude... Is not the hero we deserved, but the hero we needed

[@billieguitar]

BTW a turboshaft engine (the configuration explained later in the video, used in tanks and helicopters as explained) is being used in a street legal motorcycle! If you're interested it's called the Turbine Superbike, research it it's a pretty unique thing

[@GobindaDotel]

I searched lots of videos at KZbin but this video finally answered my queries. Thank you.

[@233kosta]

Might I suggest adding also a separate set of videos on how axial compressors and turbines work, I think they would supplement this video nicely

[@ChrisZoomER]

That was awesome! Are you able to do a sequel video to this explaining how turbofan and turboprop engines work? If so, I'm sure we'd all love to see it!

[@marketfluxadvertising]

Wow engineering explained 9 yrs ago love this guy even now. I want this guy as my Physics lecturer..

[@bodom11716]

Thank you, much better than the other explanations of this on KZbin

[@matthewotasowie7695]

I have listen to this topic several times, this is simple enough to almost anyone. thanks

[@flyingtravel]

Simple but very nice and clear explanations. Thanks!

[@quahntasy]

The clearest explanation out there.

[@ozzyan123]

Only a small comment, the air velocity is quite constant through the compressor stages. The goal is to increase the pressure, not the speed. (To begin a preliminary design, you can start from the approximation that the inlet and outlet velocity of a given axial stage is constant) Thank you for posting, very good

[@SirPlankton]

An afterburner introduces fuel into the exhaust stream and igniting it, producing more thrust as the gasses expand. This is where thrust vectoring and adjustable vanes come into their own in fighter aircraft as usually a computer like a FADEC would optimise the outlet vane diameter to produce maximum thrust with reheat. Hope this helps and sorry for long concentric replies.

[@115racing5]

Out of all the super well put together 3D videos you are the only one I could understand. Simple and directed. Great for visual learners. Thank you.

[@davidthomas8258]

He does a great job explaining this stuff.

[@veeaa]

1. The compressor does NOT have turbine blades. Turbine is a device that converts kinetic energy into rotational shaft power. That's why you don't have turbine blades in the compressor but compressor blades. Terminology is important! 2. The air does NOT accelerate in the compressor. The narrowing of the compression path is meant to prevent the air from decelerating too much. 3. Modern engines don't have combustor cans anymore. They have a single annular combustor. 4. Modern aviation jet engines are turbofans that have a fan in front of the compressor. It accelerates air that bypasses the core jet engine that you drew completely and may create most of the thrust depending on the design. 5. It would be important to tell about the exhaust nozzle after the turbines which is what accelerates the gas to the highest speed producing thrust. Without the nozzle the gas coming out would be just a hot breath, exaggerating a bit.

[@veeaa]

I should correct myself a bit. The fan and compressor do in fact accelerate air from the relative standstill to the speeds inside the compressor. Also according to a Rolls Royce video the air is also accelerated between low pressure compressor (booster) and high pressure compressor. However the total air velocity does not increase while it's passing through either of the compressors.

[@rockhopper123452]

veeaa Where can i learn more about jet engines? Im actually really interested.

[@233kosta]

rockhopper123452 Best thing to do is get a degree in aerospace engineering. Failing that, many books on thermo/fluid dynamics can help you. A good place to start is a book published by Rolls-Royce (in many editions) titled simply "The Jet Engine". I'd advise you to get the latest edition as it will reflect the most current information. It _is_ simplified to an extent and does not include the maths behind it (mostly), but that's what the degree and really thick and topic specific books are for :)

[@veeaa]

rockhopper123452 Sorry, I sent you a reply when you asked but it never registered obviously. I agree with 233kosta, just stay away from the latest Rolls Royce The Jet Engine book. It doesn't explain many things the older versions do and the quality is rubbish too. Two of my copies are falling apart by themselves! Also, check out this virtual tour by Rolls Royce with very good and easy to understand information: www.rolls-royce.com/interactive_games/journey03/ If you want a very comprehensive information package, still without complicated math, read the "Aircraft Gas Turbine Powerplants" published by Jeppesen.

[@233kosta]

veeaa Have they messed it up in the latest release? Damn

[@EngineeringExplained]

@9743271297 Wish I could help. Although aerospace is offered at my university, I'm in mechanical engineering. I made this video to help a student with a class project. Not sure of a good book to use.

[@alysonserrao5128]

Actually you forgot the bleed air. Well you did good. You owe knowledge. Aaah didn't make sense.

[@EngineeringExplained]

Yep

[@jasvir605]

I was trying to understand jet engine easy theory last 6 years. .but you explain it very easy way. .thanks. .but can you tell me about shafts how it's joined with cover drum or whatever you call it. ..

[@nev123123123]

I read a book once and it suggested that the turbines and compressors were designed ie the angle of the blades in them, to facilitate the continued movement through the engine. path of least resistance. aswell as the combustion chamber outlets pointed at the turbines

[@FALprofessional]

What are the shafts that connect the compressor and turbine blades connected to in order to keep them contained in the engine housing?

[@samuelramesh8621]

Excellent explanation. I want to how the big fans at the front gets driven first? Is it that when the airplane runs faster in the run way, does the speed of the wind hitting these big fan spins compressing the air to start the combustion, is that correct?

[@EngineeringExplained]

Afterburners incorporate a method of injecting fuel into the exhaust of a jet engine, burning up the remaining oxygen and creating extra thrust.

[@grzesiek1x]

I have just been in the Aviation Museum and watched all those jet engines. Thanks for your explanationts. It makes more sense now to me what I saw (and secretely moved some shafts - I couldn't resist - 🤫 without any harm of course ;) )

[@user-dg3qf7di1e]

So what is the starting system for this engine?

[@flemmingploug2670]

I'm stunned it took you 6 minutes to explain me something i have been trying to figure out for years watching several other video's about Thanks a lot

[@zrx8]

From the first time back in my childhood when I first heard about how jet engines work, quite until now I still can't understand, why the expanding gases don't exert the same momentum by braking the compressor as they accelerate the turbine. I mean, I know the thing works somehow, but the main trick (at least for me) remains always unexplained.

[@dido1803]

Great explanations and easy to understand.

[@Skyefuego]

I start school on aviation maintenance next month. I can't wait to learn even more.

[@karmakingstephen]

Cool. I'm thinking about the same career path. Not sure yet though.

[@Skyefuego]

Man, it's pretty cool stuff. I'm learning basic electricity right now

[@karmakingstephen]

Cool. Some of branches of aerospace and marine look really cool but I still have no idea what I wanna do.

[@Skyefuego]

You should have them give you a tour of the schools.

[@karmakingstephen]

Perhaps

[@yco67]

yep.. but for example in fighter jets they don't you use afterburner that much only on take off, vertical flight or dog fight etc.. whats the disadvantage of afterburners.. is it only worst fuel consumption or it creates overheating after a while in engine?

[@modernpanther]

You don't want to have on all the time because of the high fuel consumption. There are also limitations involving altitude and air pressure (i.e. it's much more efficient to activate an afterburner at certain conditions). I'm not sure of any overheating issues, but I assume the afterburner section experiences the similar conditions as the pre-turbine, combustion stage.

[@skxjenje1072]

hi, im curious if jet engines use spark plugs to ignite the air fuel mixture or is it just that the air is too hot that ignites by itself when mixed with fuel

[@godzalli44]

wow, i am newbie , and i see this is very clear explanation, and simple. SUBSCRIBED!

[@m.s.kk.8539]

Great explanation. Thank you. My 9 year old understands it. Using the drawing and the main components as a science project.

[@chriscanada2439]

So how do you get the speed for that?

[@animosity242]

I think I know what you mean. When the gases expand, they are going to move toward the path of least resistance. In the example above, because of the change in the pitch in the blades, the easiest path is out toward the rear of the engine. Though there is actually pressure on the backside of the compressor blades, there is more net force on the exhaust side that continues the momentum of the blades.

[@philb912]

Holy crap, you've come a long way since then !!!

[@philb912]

but your explanations are always great !

[@caimetalfesto]

what makes the blade start to rotating? initial process?

[@carlosp9933]

Doesn't the force of the exhaust gas weaken after passing the last turbine? How does the weakened force drive the engine?

[@mohammadanwar6515]

Is there an external engine to rotate the turbines. Or how do they rotate by themselves

[@shubham-pawar]

I see the whiteboard has been with us from the very early beginning.

[@SeIzmIc12]

as the air comes in through the intake does the pitch on the blades change?

[@willhaney96]

why does the pressure inside the combustion chamber not push against the compressed air and slowing down the compressor to a stand still?

[@vahagnmelikyan2906]

So are the shafts attached in one piece or individual shafts?

[@vahagnmelikyan2906]

Is the shaft directly attached to eighter side blades?

[@davidtheguitarman]

But how do you get each shaft to spin at his own speed?

[@josephburton92]

No one really knows how Jet Engines work it’s all Magic!

[@jibjob3298]

I've just watched a video actually and now I know how they work.

[@jeremyclarkson-69]

​@@jibjob3298 yeah it's not that simple unless you're a aeronautics graduate KZbin doesn't provide you the full picture but only the basics

[@lakshmanreddyMADDULA]

which book is best to understand aerodynamics, aircraft structures and jet engines.

[@TheTerribleSwede]

Do you have a particular triple spool coaxial turbine in mind?

[@jasonlauder3402]

I know this is bringing a video back from the grave possibly but this seemed the best video to ask my question on. What are your thoughts on micro turbine hybrids as range extenders in both trucks and cars? maybe a video to explain the concept and the pros and cons from your point of view. P.S. Watching this old video of yours is a chuckle

[@Tydides64]

But how does it start when it doesn't have air coming in yet, does it need some kind of electro motor to start the fan to initiate the air intake-compression process?

[@mattthompson5022]

There will be some sort of starter/APU which will be used to rotate the compressor initially to a sufficient speed to establish airflow through the engine. I imagine it will only be used until the air is at sufficient pressure (and other necessary conditions e.g temperature/velocity) for combustion to be sustained. Im mechanical engineering undergrad so I don't claim to be an expert at all but that's my best guess!

[@tylerhunter3763]

@@mattthompson5022 the APU sends bleed air to the HPC and that will spin the turbines which will then spin the fan in the inlet. Once a specific RPM is reached fuel is introduced and it will become self sustaining

[@joseacuna3239]

10 years later you’ve come a long way Jason.

[@joshlawson5436]

Is it true the lower the bypass ratio the louder the engine will be? Like for example will a jet with a bypass ratio of 0.7 be louder than one with a 1.2 ratio?

[@daanvandenberg5204]

Yes that is true. How bigger the bpr the more silence the engine is. The reason is that the cold air is ‘isolating’ the hot air and hot air makes a lot of noise. Because of higher Mach number

[@dashbmw]

I believe the air flow through the engine stays at the same speed. Of course after the inlet duct slows it down and after the exhaust nozzle accelerates it. Also after the combustor the gas speed will be greater but the turbine does not slow the gases either. The compressor (Turbine) rotors and stator are designed to maintain a constant air speed.

[@nolanh1991]

@EngineeringExplained thanks you. I have a follow-up if you don't mind: by what means or mechanism is fuel provided to be ignited, does it use fuel injection?

[@swayingGrass]

Very good!! You did explain the basic. Oh yeah, don't forget the stators ^^.

[@jaimu30]

Okay, so I guess then that once the engine is running, the hot air coming out of the exhaust keeps the blades spinning and pulling in more air, so you don't really need to power the blades anymore, but how does it start? Can the combustion alone at first start it and it gets faster and faster?

[@peterf557]

They use a starter motor to get going. Once you get it started, the more fuel you put in the higher the rpm gets.

[@n7565j]

Excellent explanation! But I had an ah ha moment half way through your video... Consider the engine in 3 pieces, 1st is the compressor, 2nd is the storage tank (this was my ah ha) the fuel is injected into the burner can (which remember, it's located inside the storage tank) sort of like direct injection in a car, and burned expanding the gases imparting more energy to the tank of air, the aft is the exhaust which is where the the burnt gases are expelled causing thrust and also turning the drive shaft to start the process all over again, except, the air never stops like my imaginary engine :-) When I thought of the engine as 3 distinct pieces, it all made since, now I had something that looked a lot like a normal 2 stroke engine.. Minus the stroke ;-) I realize you'll never see this, but I've studied turbine engines forever but never understood them, Thanks :-).

[@mabazarichy2]

Front of the intake is the compressor blades not turbine blades as you have called them at the beginning

[@Triple070007]

Why isn't the faster air going out the back slowed down again by the slower (red) blades?

[@JoseMedina-gf4cu]

Subscribed for the car content many years ago, but back watching this old video because I'm in ground school now trying to become a pilot 😁😁

[@prandomable]

so the engine on fighter jets are different from the commercial jets? If yes then how much technical difference?

[@timnb0340]

this is the best explanation i could find!

[@SirPlankton]

You missed out the stators in the compressor stage I believe, its used to increase the pressure, as the axial flow coupled with the venturi effect of the engine design drops the pressure for increase in velocity.

[@fitofight8540]

Why do the exploding gas dont come out in the intake?

[@EngineeringExplained]

Y2k, yes, an awesome machine!

[@MrIrrepressible]

So is a jet engine siimular to a turbo? Also how does an after burner work?

[@carlmis4680]

Nicely made man!

[@SWSW560]

Dude ...it's 2020....look at you now....thumbs up

[@kakr8r785]

Do turbine blade spin with same speed as that of compressor?

[@tanmaydeshmukh7850]

Best... i think we all here need more related sequential videos up to a working prototype.

[@thebrain7441]

Perfect for visual learners like myself.

[@af235]

WOW!!! you been doing this since 2011?? i just learned about you 3 yrs ago!!

[@shams166]

Source which run/drive the compressor????

[@garyanellis6132]

This is the best Explanation ever.

[@yco67]

what about afterburner?

[@poorformance7392]

Great explanation!

[@LouisSamuel82]

Why does the air flow into the intake in the first place? it is the shape of the combustor?

[@nightyjammer2532]

Fan

[@hunterrogue8591]

I am so using your video's for my Aviation Students.

[@dimwitrj]

Getting recommended this in 2022. Great explanation!