Appreciating The Beauty of Jet Engines by Juxtaposing Them Against Piston Engines

[@d4a]

NOTE: After shooting the entire video I noticed that the turbine blades are pointing in the wrong direction. The "scooped" part of the blade is pointed away from the stream of air. I was just blindly following the model instructions and focused on shooting the video so I missed this. But this video just covers the basic operating principle of the engine and I didn't discuss any fluid dynamics, this will be corrected and explained in more detail in future videos. "Use juxtapose in a video title" crossed off the bucket list This is the jet engine model from the video: *REMOVED* until the assembly instructions/parts are updated by the manufacturer. Patreon: www.patreon.com/d4a Amazon: amzn.to/47U9Zhj Shop: driving-4-answers-shop.fourthwall.com/en-eur/

[@Rampart.X]

Replace "against" with "with" - ie "juxtaposing with"

[@luiscardozo0000]

i want to know where did you learn to speak english like that?...its amazing , please tell me and another little question why you dont live in the us or canada we really need people like you...thank you very much and please answer me

[@Lozzie74]

D4A, I’m glad you commented about this. It was the first thing I noticed and came here to comment but was glad to see you had made the comment.

[@Lozzie74]

@@michaelbrinks8089turbofan blades look just like turbine blades. They are simply larger. Their role is to act like a propeller to generate more thrust.

[@MinecraftMasterNo1]

@@michaelbrinks8089 Yeah, maybe a video on Turbojet vs Ramjet vs Scramjet would be good as well.

[@RafaelLima-ce1rh]

Can you imagine how developed of a world we would live in if all the teachers were just like this guy

[@d4a]

There's likely many better ones out there . It's maybe the willingness of the people to listen that's the bottleneck? 🤔

[@4ffff2ee]

@@d4a come on buddy, don't be so humble. teaching and explaining stuff is completely different from knowing stuff, and it's a skill on its own, you're really damn good at that. you really should be a teacher. and on the topic of the gas turbines, i'd love to see you do one about turbofans too. i get how they work, but i don't understand why. i don't get what's the purpose of the bypassing air.

[@bernarddelossantos322]

Exactly.. im not a native english speaker and yet I easily understood every explanation he says.. one of my very few favorite youtube channels.

[@williambarry8015]

I probably had teachers as smart as this guy but i was too stupid to realize it.

[@SnowIsMyTerrain]

@@d4aIMO, there's a lot to be said about someone who can explain things well, understandably, and passionately. There's a whole lot of people out there who only avoided learning something because of bad teachers.

[@Chris-hx3om]

50 years I've been trying to work out how a jet engine actually works. Thank you for 16 minutes. Brilliant!

[@Sir_Cactus]

Sadly this expanation is not entirely correct. The gas pressure in the combustor does not increase, but decrease. Heating the air expands it, which would increase it's pressure if it were in a close container, which it is not. There is some backpressure in the combustor, as the turbine and the exhaust nozzle somewhat restrict the airflow, but the pressure in the combustor is always lower than the compressor discharge pressure. Otherwise the compressor would not be able to push more air into the engine and the engine would stall.

[@Blockbuster2033]

@@Sir_Cactus But doesn't increasing the pressure in the combustion chamber also make more power, because you are basically moving more air through it? Basically like turbocharging a piston engine?

[@JohnFrumFromAmerica]

​@@Sir_Cactusyou have no idea what you are talking about. The pressure in the combustion chamber is 60psi or 4 bar . This takes seconds to look up why post such bad information.

[@Dellvmnyam]

Basic jet engine principle is much siumpler than described here.

[@akhtarkh]

If you don't have internet for 50 years, there must have been libraries, where I used to get my information before the internet.

[@jorge8596]

Another huge upside for jet engines is their incredible reliability, as long as they are maintained properly they will almost never fail, save for external things like a birdstrike or a fuel system failure that would have stopped any type of engine. And even if one of them were to fail, they have so much power that a fully loaded passenger jet is capable of climbing on a single engine. They just fit so perfectly in the role of an aircraft engine it's incredible

[@3SPR1T]

They have an extremely long life span compared to piston engines but yes they do fail... Usually to degrading turbine blades because it's the most stressed member of the system. One major facor is thermal cycling. The longer the engine runs at a time the longer it will last. Industrial turbine engines that never shut off can last up to 20000h. The thermal cycling lead to cracking of the turbine blades.

[@Blockbuster2033]

I largely agree, however, a birdstrike will do barely anything to a piston engine, but can totally destroy a turbine.

[@MinecraftMasterNo1]

@@Blockbuster2033 Clogging the air intake on a piston will lead to an extremely lean air-fuel ratio leading to numerous issues that can permanently damage the engine. What are you talking about?

[@Blockbuster2033]

@@MinecraftMasterNo1 That is correct, but the air intake is extremely small for a piston engine in comparison to a turbine engine making it less likely to get hit. Also it's very unlikely that it actually clogs up.

[@D3V1NF5]

As an aircraft maintenance technician I can attest to this, in fact, only a few hours ago I was doing an internal inspection of a 737 jet engine for wear and damage. The engine in question had just under 35,000 hours on it. Meaning that it had been ran for close to 35,000 hours. The inspection went fine, which is to be expected, because we normally get another 20,000 hours out of it before it needs to rebuilt! They are truly magnificent feats of engineering.

[@pahaahv]

Thank you. Natgeo and Dicovery needed a competitor. Calm explanation, understandable diagrams, important efficient interesting content and no commercials, this is what a popular science channel should be like. Looking forward to new stuff!

[@jesusfreakpl]

Dicovery - should be Dickovery :D

[@brianb-p6586]

But there are substantial technical errors.

[@aheartattack1]

I commend you D4A for trying to explain these complicated engines. Heres some feed back! 1) they vibrate like crazy, as they can rotate at speeds well over 50krpm, it's not uncommon to have "modes" or natural frequencies in the 900hz or more. 2) compressors: the rotors increase P total, the stators convert most of the Ram pressure into a static. 3)the reasons each stage gets smallest is due to the density increase of the air. The engine must have near constant mass flow throughout. (Near constant due to bleed systems etc..) 4) as the gasses combust, the pressure goes down! If it didn't, it would go back to the compressor which is lower temperature. The highest pressure in engine is right after the compressor. As the gasses burn and heat up, the velocity increases. 4) the turbines have two sections like a compressor, stator and rotor. Also, unlike a compressor, they increase in size due to the density decreasing over each stage. 5) for most jets, the highest temperatures are seen on starting. There's not enough airflow to cool things and there's a ton of fuel burning on things. That's why the quickest way to kill a jet it to start it with a weak battery. 6) the ignitor only comes on at start or inclement conditions. Generally combustion is self sustaining. 7) the turbine on the model is installed backwards. 8) the usual limit on rpm is the material properties of the rotors due to centripetal force. The larger the engine the slower it will rotate. 9) One thing you did not mention, as the engine has all stages operating simultaneously, the engine grows unevenly, the cold section compressor will grow very little, the combustion and turbine section can grow A LOT. A large turboprop can grow as much as a .25" over those sections from cold to max power. Again, nice video.

[@kentauree]

What a load of bs!

[@therflash]

@@kentauree what?

[@9HighFlyer9]

​@@kentaureeafter a quick read through I don't see anything wrong in what was written. Anything specific?

[@jetcitykitty]

That shot panning up from the bike exhaust to the jet taking off was real smooth ❤ thank you for more knowledge!

[@TheRalliowiec]

Trying to channel some James Burke, no doubt. Too bad this wasn't a video about rockets.

[@jetcitykitty]

@@TheRalliowiec I'm going to be honest, I have had a huge crush on @driving4answers for awhile now. I'm attracted to intelligent men, especially when they are as good at communicating, as he is. He is totally capable of surprising my own intelligence, and challenging it when it needs to be challenged. I'm just saying, big wrinkly brains are sexy. I shouldn't smoke weed before i write comments

[@NortheasternP.T.S.]

@@jetcitykittywhat the hell…

[@Skibidigokyllyourself]

​holy shit methead calm down@@jetcitykitty

[@InitiateDee]

@@jetcitykitty ayo what the fuck

[@timessix8434]

Once you start calculating stage efficiencies and blade angles in gas turbines, that’s where the real fun starts :)

[@michaelbrinks8089]

I can only imagine....blade shapes, blade angles, blade spacing/number of blades used, distance between sets of blades, stator shapes, stator distance, combustion chamber shape/ size....The list goes on, to determine which design works best overall= driving yourself crazy 🤪 🤪

[@Blockbuster2033]

@@michaelbrinks8089 One would need to have a good simulation program that then could automatically go through thousands of iterations to optimise various parameters and converge on the "best" design for a specific task.

[@pruthvirajbhople]

Blade and stator: Cross-section Shape Size Angle Curvature Thickness Spacing Material Surface texture Weight Bending moment Efficient RPM range These things are on top of my mind Add more if anyone know/think of more

[@Soupy_loopy]

For real. I love it how 50,000 people think it's so easy now after watching a 16 minute introduction to jet engines.

[@renesisfd1]

​@Sqeeze_da_cheez people aren't thinking that. It's like any topic, the theory and basically of operation are simple when explained well. When it comes to actually making it thats when it becomes complicated.

[@Terrados1337]

To be fair a turbo fan is just attaching a big fan in front of the turbine and encasing it so you have lots of air bypassing the turbine. And a turbo prop is just a jet engine but you attach a propeller. And if you want to be REALLY fancy you bend those prop blades a bit and call it the "revolutionary (tm) CFM RISE" Great video!

[@allesmedvesek]

It is also worth mentioning, that air at about 10 km altitude is usually very cold which helps a lot with efficiency.

[@Tornado2409]

hence why race cars have intercoolers

[@makantahi3731]

hottest air is on higher altitude, that is why is up, not down , because is lighter, if you take 1 cubic meter of air from 12km in sealed syringe, on sea level it would have less volume and higher temperature than local air on sea level

[@OldSchoolZ-wy2yx]

​@@Tornado2409some use the A/C to cool down the intercooler too and I think that's awesome

[@NavyVet4955]

@@makantahi3731that maybe the most ignorant post concerning air pressure I've ever seen.

[@gort8203]

@@makantahi3731 Your sentence is unintelligible, but if I read it correctly you are mistaken. Air from 12 km high is less dense than sea level, but it is colder, not hotter.

[@gort8203]

Actually turbojets do struggle more at high altitude than at low altitude. Air density is the prime determinant of how much thrust the engine can develop, so thrust drops with every foot the aircraft climbs. Transport aircraft get around this by flat-rating their engines. At low altitude the engine can actually produce more thrust than than it internals can withstand, so the throttle is only advanced as far as that limit. As the airplane climbs and air density and thrust drop off you can increase the thrust lever setting to work the engine harder and continue to produce sea level thrust with reduced air density -- up to a point of course. It is somewhat analogous to managing manifold pressure in a supercharged piston engine. At low altitude the turbo can deliver more MP than the engine can withstand, so you have have to throttle the engine back until you reach the critical altitude where you are working it at max capacity.

[@thenewhalogod]

Aircraft mechanic here, just a note. While what you described is in fact a turbo-jet, was was used on aircraft in the past most airliners today use turbo-fans for turbo-props. Basically the turbine is just a torque producer to run a big ducted fan or a propeller. think of Dash-8, it is turbine driven but they don't produce thrust, only torque for the props.

[@d4a]

Hi Aircraft mechanic, yes, I mentioned this at the very end of the video. This is an ancient design but it's there to explain the basics.

[@indiglowpufferfish1002]

​​​@@d4aalso aircraft mechanic here the power section blades stator and rotor look backwards on your model. The engine would be operating backwards in that configuration. Might warrant a reupload to prevent confusion. But definitely fix if you are using that model for teaching purposes in future videos.

[@onefastneonrt]

​@@indiglowpufferfish1002I thought too. If the turbine blades were to spin in it's correct rotation, the compressors would be directing airflow the wrong way.

[@tturi2]

​@@indiglowpufferfish1002the orientation of the blades is a few more levels advanced than this video really needs

[@piccalillipit9211]

*ONE OF THE BEST DAYS OF MY LIFE* was a private tour and explanation at the Rolls Royce Jet Engine plant at Derby in the UK - absolutely amazing They GROW the turbine blades as a single crystal of titanium...!!! Also they don't compress the air in the RR engines, they keep the pressure the same and increase the VELOCITY, this lowers the temperature of the combustion I believe.

[@Sir_Cactus]

You are correct, gas pressure in the combustion chamber should be atmospheric, it is indeed velocity what is needed. In fact the only reason why the compressor is there is to prevent the exhaust gases from going back through the intake. After the compressor, there even is a diffusor (even in his model), where the intake air gets expanded, reducing it's pressure.

[@crissd8283]

I think you mistook what you were told. Technically the compressor blades increase the velocity of the air while the stators actually do the compression of the air. RR jet engines certainly compress air before they enter the combustion chamber.

[@Zmit]

Top fuel dragsters actually DO use the thrust of their piston engine's exhaust to contribute to down force or propulsion, but most often a combination of both.

[@peterchampagney4990]

I'm currently in college to become an aviation mechanic and just finished my semester on jet engines and am about to finish piston engines and graduate. You have done a beautiful job of explaining this, keep up the good work. Also if you have any questions on jet engines in the future I'd be happy to help

[@pruthvirajbhople]

I always wanted to make a turboshaft motorcycle. Where can I source a small turboshaft engine? I believe they are being used for power generation and helicopter, any other application of turboshaft that I'm unaware of? Any brand name/engine model you can suggest which is small enough to fit in motorcycle chassis?

[@richardlewis4288]

Good luck on your career choice. I’ve been an aircraft mechanic (A&P) for the airlines since 1983 and loved it.

[@brianb-p6586]

If you think that was a good description you should go back and review your course material, particularly looking for information on the diffuser stage between the compressor sections and the combustors, and on the temperature, pressure, and velocity of the gas as it goes through the engine... since all of that is wrong in the video.

[@theairaccumulator7144]

​@@pruthvirajbhople something like that would have a price tag in the tens of thousands & it would be much less powerful

[@abraamsamor7418]

​@@richardlewis4288How's the pay? I'm also in college to be an A&P, except I just finished the first semester, so I still have a couple years left.

[@icezebra]

Worked on Super Hornet engines while I was in. So cool taking them apart, putting them back together, and then testing it in a test cell.

[@beingsailorshani]

I'm will be going to recommend this channel to my future son🙏

[@lennie617]

Please do more or this aviation stuff. I find it very fascinating, not least the final developments of large radial piston engines. The Wright engine used in for example the Douglas DC7 actually used turbo compounding with a turbine very similar in principle to the one you showed running off water. This turbine added power to the engine without taking any power from it..

[@Obsidian0Knight]

Man ive watched so many of your videos, they just seem to be getting better snd better the more i watch

[@Reimalken]

Such a quality, detailed and approachable explanation. I am not a car guy but I find mechanism and engineering fascinating, and the channel has been wonderfully empowering so far :)

[@firstielasty1162]

Good video! If you're going to diverge from cars, consider rocket engines as well. Non-air breathing, I mean. V2 development is interesting, and I'm always amazed by the fact that each of the 5 first stage engines of the Saturn booster had a fuel pump (of course) , turbine powered. EACH was 53,000 horsepower. The fuel pump. The actual engine power is hard to compare to any other machine made by humans. I'm a car/motorcycle nut, A&P mech, pilot...if it burns fuel and makes noise, it is interesting, sometimes amazing.

[@zweispurmopped]

The turbine wheel in your jet engine is installed in the wrong orientation! Except for that: As usual with you, a brilliant video! 🤩

[@jhgrc]

exactly I was to write about this - but checked if someone else had noticed.. :) This orientation causes compressor to rotate wrong way round..

[@DCDrCoyne]

​@@jhgrchaha same

[@indiglowpufferfish1002]

Agreed his stator on the power section is backwards as well. Great content but kids learning this for the first time will get some very bad misconceptions about the power section.

[@eTiMaGo]

Every time I think I know all about something mechanical, here comes D4A to show me how little i actually know :D

[@d4a]

I'd like to like your comment but I'm not going to support a claim to the lack of your knowledge, which I believe is unfounded :)

[@eTiMaGo]

@@d4ayou are too kind :D We just love things that make us go fast! I was about to ask for more details about high-bypass turbofans, but you covered this right at the end... really interesting stuff!

[@silvervortex2441]

Please do more on jet engines🙏. I know this is an automotive channel and i’m asking too much but your explanation is on a whole another level.

[@markam306]

You may want to look at the AgentJayZ channel. He is a jet engine technician who rebuilds them. Jay has extensive knowledge and the ability to convey it using normal english.

[@photohounds]

I grokked much of this already, but as usual, you reveal some interesting gems along the way. Bravo, sir! Rarely can I resist watching your videos.

[@rodintoulouse3054]

Another fantastic, simple and clear explanation. Your understanding of the subjects you tackle at such a young age is impressive. Extra points for the opening sequence with the take off shot

[@АнтонДемченко-д8т]

It took my uni 1 year to explain the turbojet engine operation. You did it in 20 minutes. Thank you for your work! I hope it will be useful to a lot of people.

[@truebluemiata]

Echoing others, I finally understand the JE principle and process. Yes please, a JE 102 video, bypass, ram, scram etc🙏

[@TheFakeFatLegitimate]

Your timing is crazy, I was looking into jets just yesterday!

[@richardconway6425]

What did you see?

[@therflash]

6:52 - No, the pressure in the combustion chamber isn't increased, it stays the same. It's volume that's increased. If the pressure increased, nothing would be stopping the air from going out through the front.

[@ravener96]

Something to note, combusting the fuel doesent actually increase the pressure, as the pressure has to be lower in tye combustor for compressor air to be able to flow in. What it does is it takes the high pressure air, and increases the volume without decreasing pressure, you just get more of it.

[@godfreypoon5148]

I was yelling at the screen about this.

[@AfonsoBucco]

but, does it increases the speed of the air?

[@godfreypoon5148]

@@AfonsoBucco Yes.

[@Meyer-gp7nq]

I’ve been interested in aerospace engineering for my whole life and I’ve studied in so many aerospace classes, both highschool and college level. I’ve never seen a better explanation of jet engines. I also never knew jet engines had stators. Well done!!!

[@IkarimTheCreature]

Thank you so much for indulging in my request from your last video! I'm looking forward to the next installments of this series. One last thing, I don't want to be pedantic but at 6:50 you made a little mistake. The pressure doesn't rise in a constant pressure type engine like a gas turbine, the temperature and *velocity* of the gas increases.

[@d4a]

Yes, a few things interconnected at the same time so it happened :) Maybe I should have worded that part differently and made it more clear that what I'm describing is the engine being fired up, hence the mentioning of the sparking. I'm basically referring to how all the steps increase the potential energy in front of the turbine. Obviously pressure increases with combustion in comparison to what it was before combustion started and then remains relatively constant since combustion is mostly constant. Hope it makes more sense now.

[@IkarimTheCreature]

@@d4a It's realy untuitive, but the gas never increases in pressure in a jet engine combustor, since it is allowed to freely expand and speed up towards the turbine section where the speed is harnessed, and used in the compressor section to increase pressure. But your video makes it seem like the combustion chamber is what increases the pressure. If it did that the flames would shoot out the front and you would have a real mess. No one expects the pressure to peak at the compressor section, but at this point it feels like esotheric knowledge to most people, so it would be super appreciated if you could elaborate on this when you make a video about the crysler gas turbine or the olds mobile coal turbine cars. cheers!

[@AfonsoBucco]

@@IkarimTheCreature talking about esoteric (or exoteric) knowledge, I confess I still feel it's counter-intuitive the fact you have less pressure in the middle of a venturi

[@emekauzo5358]

As the gases burn in the combustor, pressure is reduced but velocity is increased. Also the narrowing of the exit nozzle is to maintain velocity and not pressure. Nuce video, as always! 👍👍.

[@Casey_Schmidt]

The CFM-56 engine found on Airbus and Boeing narrow body aircraft can exceed 120 miles/gallon/passenger. They can be very efficient.

[@chrislatchem1854]

Really enjoy your explanations! Clear and well done. Two minor points, the pressure through the jet engine has to be less in the combustion chamber than the output pressure of the compressor otherwise the compressor couldn't force air into it (except for a pulse jet). A theoretical efficiency edge of the piston engine is that work is extracted from the system at a higher absolute temperature (as the pistons are not exposed all the time to this temperature) and efficiency is related to difference in T between where energy extracted and the T where heat is 'dumped'. I learned from you that the ability to run in low atmospheric pressure of jet can overcome this disadvantage though. (Wonder if you ran a supercharger at a high enough ratio you could get it back though?) As we get better materials for blades to live in the exhaust gases this 'advantage' will be reduced. Jets are so nice for their simplicity though!

[@Anima_2_2302]

what a fantastic video. than you very much for the comparission and the new style. how does a turboprop function, compared to an prop?

[@napsage]

the timing for that plane during the intro 10/10

[@DonnieX6]

What a great video, thank you so much! Please do continue with this turbine story line, will watch them all! 😊👍

[@mohammedalmamari7494]

You're the ULTIMATE TEACHER when it comes to machinery and mechanics.

[@gollygosh40]

top marks, your videos are always very interesting

[@williamebrahim2612]

Even if I think I know how something works I still watch your videos because every time I learn something new, keep up the good work

[@johnelliott7375]

I wish you were able to do one with the Chrysler Turbine engine in the 60's . Would like to see what, how, and what it would all run on for fuel, plus what kinda power it made and what kept it so quiet compared to the rest of the Jet engines of today.

[@BillSmith-fx7xx]

I am making a guess here. 1. It had a diffuser type muffler / exhaust. Spread it over a larger outlet and therefore slower airflow. 2. It was designed to output 'shaft horsepower' for movement (work) rather than thrust / highspeed air for movement.

[@theodebordeaux8368]

I love cars and I recently really begin to like planes. The best cross over👍👍, thanks

[@buxybuilt1519]

Overall great video, a few things to note: You are incorrect about the purpose of the narrowing compressor duct. It does NOT increase pressure. The duct narrows to maintain air velocity. As the compressor blades and stators work the air, its pressure/density increases. When the pressure/density increases, its volume decreases. To maintain air velocity for an incrementally decreasing volume of air, you have to decrease the area it travels through. Aka narrowing the duct. You want to keep air velocity travelling through first 3/4 of compressor section mostly the same and only increase its pressure. If you didn’t narrow the duct, the air would lose enough velocity to render the engine useless. Also, your model is a bit crude, it doesn’t show accurate combustion chamber hole size and placement. Primary, secondary and dilution holes all have different purposes. Then there’s wall cooling holes that are much smaller (not shown in your model) and also swirl vanes around the fuel nozzle. But your explanation of this part is decent enough without making the video too long and complicated.

[@michaelsohocki1573]

Brilliantly taught! What great teachers do, they take a piece if knowledge that is apparently inaccessible and opaque, and crack it open, and make it not scary--so that the student can climb into it and understand it for themselves. Thank you for doing that. I know it's not easy.

[@matthiasmay1977]

Pressure is NOT increased in the combustion chamber of a gas turbine. Temperature and volume are increased during combustion. The pressure after the combustion chamber is the same like the pressure after the compressor. This is the reason gas turbines are not efficient under partial load or even worse when idling. A certain speed is need to get a good compression. In a piston engine compression is given mostly by the geometry and can further easily be tuned to different conditions by valve timing.

[@skaldlouiscyphre2453]

Basically a turbofan adds a ducted fan (typically) to the front of a turbojet. The exhaust gas has less energy due to more work being extracted from it, but the additional cool air adds more mass, which offsets that, in particular they tend to be more efficient at somewhat lower speeds. Fighter engines are often described as 'leaky turbojets' due to how low the bypass ratio is. Essentially the bypassed air largely serves to cool the engine, rather than contribute to thrust. Because very little air is bypassed, not very much energy is diverted from the exhaust gas, meaning the engine will be more optimized for higher speeds. Going in the opposite direction one can remove more, or even all of the energy from the exhaust gases, whether to a propeller or some sort of geared fan. This further optimizes the engine for low speeds over high speeds. The RFB Fantrainer is a unique example of a using a ducted fan instead of a propeller. Very high bypass turbofans use a gearbox between the fan and compressor to reduce the speed of the tips of the fan blades, reducing noise and improving efficiency at lower speeds. There's also propfans, where the fan is unducted and looks like a multi-bladed propeller sticking out the the jet engine.

[@thomasbordelon4149]

I have never been a fan of jet engines or jets, but the science and capabilities are incredible. They are definitely going to give even more to the future.

[@truebluemiata]

Fans. Fanjets. Phunny!

[@masonrobbins9302]

The timing on that intro shot was immaculate

[@Yakhontov]

6:50 Increasing volume, not pressure. If the pressure is increased, it will become greater than the air pressure and air will no longer enter the combustion chamber.

[@leoa4c]

When you heat something up the pressure goes up. Why isn't so in this case?

[@kennethhumphries2930]

I've been looking for someone to use the word "volume". There you go. That's key to the whole operation. All the pressure that spins the turbine and propels the reaction force is developed by the compressor. But the compressor only increases the pressure of the low volume of intake air. The burners add energy by multiplying the volume of the air by making it hotter. All that hot air has just a little less pressure than was developed by the compressor, but now there's lots of it.

[@kennethhumphries2930]

@@leoa4c When you heat something up the pressure goes up only if the volume remains the same (or doesn't sufficiently increase). You can alternatively heat something up, maintain constant pressure, and allow the volume to increase instead.

[@leoa4c]

@kennethhumphries2930 Ok. With that in mind, the only way for volume to increase is for it to pass through the turbine. Correct? Also, is that the reason why multiple turbine stages get progressively bigger (the opposite of compression stages)? Because static pressure must not increase?

[@Yakhontov]

​@@leoa4c "When you heat something up the pressure goes up" This is not entirely true. By the ideal gas law when heated, pressure and/or volume increases, depending on the design. Jet engine designers make sure that the pressure in the combustion chamber does not rise above air pressure, otherwise the engine would't work.

[@mikemoreno2444]

thank you for the simple concise way you explain the material i wish all schools taught this way

[@Roukos_Rks]

insane timing 0:50

[@d4a]

It's not 😁 there's a cut there. Look closely.

[@zazugee]

Turbo fans basically generate most thrust from the front fans, so they extract most energ from the compressed hot air and use it to turn the front fans which generate thrust. they are like an intermediary between turbo props and turbojets

[@AbrahamArthemius]

Another thing to add with Turbofan engines is that most of their thrust is now generated by the giant fan upfront which makes modern jet engines lots more fuel efficient than older jet engines

[@ChristopherBurtraw]

That's probably saved for the next video on the subject, he kinda mentioned it.

[@hugolafhugolaf]

You have a way of explaining this simply that makes this channel so enjoyable. Great job!

[@ShoX396]

The reason for the reduction in room or space as you move through the compressor section is NOT because it is sqeezing the air... The compressor stages are littile difussors...they are designed to progressively compress the air, and as the air is compressed, its volume decreases...thats why the room shrinks. The reduction in volume is a result of the increase in pressure.

[@Ijusthopeitsquick]

Isn't that just a long-winded way of saying the same thing?

[@danielhanlon5607]

@@Ijusthopeitsquick I don't accept that you have explained the jet engine well. There is no such thing as free energy. Yes the rear turbine drives the front compressor via a connecting shaft and the air is compressed. But this does not mean that more air passes out the rear nozzle as useful thrust. In comparison your piston engine can rotate and suck air in, then the piston compresses it. If you do not introduce fuel and ignition the piston will rotate back down the cylinder to where it started at whch point the pressure returns back to zero again. In a perfect engine no energy is used to compress the air, it is recovered on the downstroke and no energy is available in the exhaust. It would act like a spring. But there is always a little friction and you will always lose a bit of energy. The only way you can get energy out is if you introduce fuel to heat the air and this causes the cold air to expand. The only purpose of the compression is to introduce enough air into a small confined space so fuel can be burned in sufficient quantity to produce a lot of power. That's why high compression engines produce more power. When you burn fuel with air it expands to make a bigger volume. This increased volume depends entirely on the temperature. In going from air at ambient temperature to say 1500C this expansion is not as much as you would think because it works on absolute temperature Kelvin with zero at - 273C. Accordingly air at ambient 273K heating up to 1730K in our example only expands by a factor of about 6 at the most. This is not a very high compression or expansion but ratio and would not produce much thrust. But you say there is a rear nozzle after the turbine to increase the speed of the exhaust air to produce the required thrust? No!! In order to do this there would need to be a significant pressure increase in the jet engine. There isn't. In fact there's a pressure drop from the compressor at the front, with the highest pressure, right through the combustion chambers, through the turbine and out the back as exhaust thrust. There are no non return valves in a jet engine and if there was no pressure drop the exhaust would try to flow back though the engine to the front! Obviously this does not happen. Using any type of compressor to suck in a lot of air at the front can only result in the same volume of air flowing out the back and with no real change of energy unless there is a great pressure increase. Dan

[@brianb-p6586]

No, @@Ijusthopeitsquick, it's fundamentally different.

[@brianb-p6586]

@@danielhanlon5607 The exhaust contains more energy per unit mass of air than the intake because the velocity and temperature are higher, not because of a pressure change.

[@Ijusthopeitsquick]

"they are designed to progressively compress the air, and as the air is compressed, its volume decreases.." Sounds like squeezing to me. @@brianb-p6586

[@keenheat3335]

a simple trick jet engine used to increase efficiency at low load is water injection into the rear part of the combustion chamber. Artificially increase the mass flow rate travel through the engine, thus increase thrust without expending extra energy. But it's usually done during take off when thrust requirement is the highest, and the reserve water tank will exhaust its water mass in a few minute of operation

[@Twobarpsi]

1st!!

[@IkarimTheCreature]

Wow congratz!

[@pabsocs]

Thank you for teaching me in 15mins things I’ve tried to understand for years, as always

[@Drunken_Hamster]

Nice. When you expand on this, be sure to flex that "low efficiency at low load" thing with what happens at high load and how a jet engine might be ideal as a range extender/active power unit for electric vehicles. IIRC "simple" construction, high reliability, high power density, good emissions, and fuel flexibility make turboshaft APUs somewhat ideal for future hybrids.

[@JWQweqOPDH]

6:51 The combustion chamber cannot be at a higher pressure than the output of the compressor because then air would not flow into the combustion chamber. Combustion only increases temperature and volume. This is similar to the fact that a fireplace does not increase air pressure, except in this case it's occurring at above atmospheric pressure. The combustion in liquid fuel rocket engines also cannot increase pressure for the same reason. The fuel pumps must output the full pressure of the combustion chamber. The combustion simply increases volume (and thus volumetric flow rate [proportional to fluid velocity for a given cross section]).

[@xkr88]

This is a good intruduction video. I just want to correct that the combustion only needs ignition for startup, during operation the burning is self sustaining. One more thing that I want to say is that the burner does *not* increase the pressure of the gas/air in a jet engine. The pressure ideally stay the same as the pressure after the compressor, but in a real engine it has some drop in the combustor. It need to stay lower than the compressor end pressure or the flow would reverse in the engine. What the burning increase is the *volume* of the gas when its temperature increases. Then in the turbine the speed/pressure of the flow is partially converted to power. More power is made in the turbine than it is put into the flow by the compressor because there is more volumetric to the turbine when the temperature of the gas is increased.

[@JazzbLu]

Ok, i love the explanation of the thrust part of the unused heat. Makes a lot more sense why jets are designed the way they are! You are an amazing teacher!

[@maxcactus7]

Confirming once again why D4A is the best engineering channel on the interwebs or anywhere for that matter! Utterly brilliant explanation & illustration!

[@joaocampos1500]

Hello @d4a just a correction, jet engines only use the igniter typically, on startup or on severe conditions that threaten flame-out such as severe rain, severe turbulence.

[@adrianreyno1]

Even though the jet engine illustrated in your video is obsolete, it gives a great insight on how jet engines work. I learn a little more each day with your videos. Thank you so much.

[@joelboutier1736]

As always, your explanations are well illustrated and easy to understand even for those that are not engineers. I appreciate your content as always. Thank you D4A. You're the best

[@anon_y_mousse]

This is exactly the video series I need. I've been wanting to build my own jet engine for a while now. I understand the operating principles, but there are always little tidbits that I miss in the operations of things and hopefully this will clear them up.

[@johnelliott7375]

I was thinking about this and not long after I was thinking 🤔 about it, bam you come through as always and I have to watch and enjoy your production as always. Awesome 😎👍 and thank you. Now I can wear my Sunglasses in the pouring rain 🌧️ North of the Farm belt country North of Pittsburgh, PA.

[@rolandotillit2867]

The airfoils on the compressor are also diverging. This slows down the air which is what actually compresses it. The case volume in the compressor is converging to help the air move faster. Air in a jet compressor is subsonic and plays by subsonic rules.

[@muhammadowaismalik3451]

I needed this guy growing up. Great quality content and amazing to the poin explanations. You have the hearts of many people.

[@paulbergin4239]

So well explained as usual. You make complicated processes so easy to follow. Cheers mate.

[@mikepratt5964]

This is the best channel on YT right now. Absolutely addicted.

[@EuReKaPresents]

Used to do heavy repairs on turboprops and man they are so reliable. Have seen shrouds on the turbine disks that were just basically gone and the plane was just fine. Often the things I have to do on the PT6 engine is all based on time limit. On the rare end, I might have to deal with adjustments but even FADEC is taking that away.

[@JustWasted3HoursHere]

I remember all the science magazines in the eighties telling us that "very soon" all of our cars would use turbines and that they'd be getting 100 mpg or more. Turns out there were many issues that were unsolvable, such as how to pipe the very hot exhaust gases away from the vehicle in a practical and safe way. Another big issue is that turbines tend to have very slow throttle response, making them not very fun to drive. But, I think they would be perfect for range extenders for electric cars because quick throttle response is not needed.

[@QUADRAXIS666]

We need to take a moment to appreciate the timing of showing the bike exhaust pulses to showing a plane taking off in one unbroken shot while narrating. Very much reminds me of the 1978 connections episode where James Burke pointed at a rocket and it launched. Very well done, you had one chance to get that shot or hours/days of waiting for another!

[@yoslauda4714]

Sometimes I need long explanation than the shorter one, especially for difficult things like this😅 Nothing I can say more than THANK YOU🔥🔥🔥

[@MrAlwaysBlue]

Excellent description. I have been trying to explain the turbojet and turbofan to my son today on a whiteboard.

[@MisterMr2.775]

this was awesome! I was hummin and hawin the whole time. I love learning mechanical things from this channel, thank you!

[@amateurtorque6709]

Thanks for this video, I never understood even the basics of a jet engine until now.

[@Tom-Lahaye]

Superb explanation of the principle of a jet engine, I never realised that the main combustion air comes in at the front of the combustion chamber, always thought that the holes in the chamber served this goal. In fact a car turbo can be used to make a crude jet engine, simply by removing the piston engine between compressor and turbine and adding a combustion chamber instead. With a simple exhaust cone fitted to the exhaust flange it does even create thrust.

[@miki35001]

turbine engines dont use the sparkplug all the time mostly during start and rain, the combustion is occurring using the self sustaining flame from the previous combustion, sometimes the flame burns out which is called a flameout, the pilot can control when the sparkplug is working or not

[@zrtlrncm]

Thank you very much for such an educational video! I liked how you started the story with an example of a motorcycle engine, being near the airport, and then near the water turbine!

[@engraving_8956]

Would love to see another video on “Free” Turbines, I Think a lot of people here would find it fascinating that most turbo props/turbo shafts don’t have any mechanical linkage from the compressor section to the driven/accessory section. That being said talking about twin spool/ multiple spool turbines would be cool as well. As an AMT this was a great video, cheers!

[@challacustica9049]

Jet engines were my first and foremost fascination, so I knew their workings well before a piston engine. Regardless watching this because you were presenting was a treat! Hats off to your great videos.

[@TBPony]

wow i was just searching this subject and well well looks like our favorite automotive engineering youtuber just posted it, how perfect is that lol. out of all of the videos ive just watched you explained it in the most understandable way possible.

[@user-rs1fo2dd9b]

i heard this from a jet engine mechanic (AgentJayZ) - he said the narrowing diameter/volume of the compressor stages against the inner casing isn't what mechanically compresses the air he said the stator is what mechanically compresses the air - as rotors spin, they increase velocity of the air, increasing its kinetic energy, then the stators convert that KE (velocity drops) into potential energy in the form of pressure he said the volume reduction from one compressor stage to the next in the engine casing is a consequence of said compression, as the compressed air occupies less & less space as it makes its way thru the compressor stages

[@marianlech3378]

Now this is just fascinating! And your style, Sir, makes it all so beautifully digestible. Oh my... love it, thank you!

[@drmahaCroc9164]

The best explainer of piston v jet engines. Well done.

[@ethanslade2362]

Hey! Great video. You may just want to do a bit of a follow up about the pressure in the combustion chamber. As it is not a sealed system, the pressure doesn't increase. Only volume does. It is this increased volume that is harnessed as greater dynamic pressure to spin the turbine. It works on a conceptually different cycle to piston engines, using expansion rather than the force of greater pressure to provide energy to do work.

[@Brian-S]

Not sure how I've never come across your channel till now. Only a couple minutes into the video but you've got a new sub, very well explained.

[@fandommennis1348]

Love your videos. You are an amazing teacher! Your amount of knowledge is staggering and the way that you present it is easy to absorb. I can onky think that if all my college professors were like you, I would've ended up being an engineer like my father instead of giving up after an associates degree. Keep up the amazing work and wish hou nothing but continued success with your channel

[@pcka12]

The steam turbine engine invented by Parsons in the 1880s provided some of the inspiration for Frank Whittle in his invention of as gas turbine internal combustion engine using continual rather than intermittent compression of the fuel / gas mixture.

[@fernandomunizsimas7023]

What a great Professor! Thanks for sharing your knowledge and your talent.

[@alanploetz7100]

A very good explanation comparing the basic differences of the two types of engines. Toward the end he got to how the constant combustion makes jet engines less fuel efficient for what we tend to use reciprocating engines for and why we don't see common use of jet engines in road vehicles. I would like to see a comparison of thrust to torque to get a better understanding of the fuel burned for work performed.

[@kermanp]

Thankyou ❤ Your way of explaining these things make them easy to understand. Can't wait for the future video about more modern jet engines.

[@kencarlile1212]

This is a fantastic explanation. I've always struggled with wrapping my head around how a jet engine creates forward motion. I can almost make a turbofan make sense, but a turbojet is harder to follow, at least for my brain. I get it now!

[@jakem7838]

A turbo fan is not much different. A turbo fan has 2 or even 3 separate rotating assemblies. The front fan is attached to the very aft turbine by a shaft, inside of a hollow tube, or spool. In between the forward fan and the aft turbine is a turbo jet engine mounted on a hollow spool. The forward fan and the aft turbine are known as "N1". The inner "turbo jet" portion is known as "N2". They spin at different RPM, to increase efficiency and performance. Rolls Royce turbo fans, have 3 spools N1, N2, N3. They also rotate reversed from GE, P&W, etc.

[@jakem7838]

I forgot to add, the forward fan air bypasses the rest of the engine and provides the majority of the thrust.

[@christopherjofficial]

Wow ! Am a CPL student and this is so much important for me to understand the turbine engine even more

[@g.4279]

Can you cover some of the land vehicle turbines? Like the Honeywell AGT1500? I always wondered why it produced so much less exhaust heat and so much more torque than the diesel it competed against.