HOW DO JET ENGINES work and WHY do they get BIGGER Explained by CAPTAIN JOE

dear friends and followers welcome back to my channel today we'll be looking at the question why size matters in aviation they're becoming a rare sight they're boeing 757 100s and 200s boeing's first generation of the 737 known as the originals famous for the unusually long and slim engines directly mounted under the wings to 737 100 and the slightly longer 737 200 paved the way for boeing's most successful aircraft family upcoming 737 generations received numerous upgrades including bigger engines which were just too big to fit under the wing anymore so therefore 737 300 and its successors had their engines mounted in front of the wing and it's not just a 737 that received larger engines the mother ship the 747 also increased her engine size over the years now this trend can clearly be seen in all generations of all types of airplanes which leads us to the question why do jet engines become bigger and bigger and are there any limitations to their size we're going to scale it up and let's get started chapter 89 kennedy ground runway three one left kilo echo right alpha and hold shorter julia before we start we have to take a short look on the physics behind the jet engine also known as the turbo jet of older commercial airliners now there is a more detailed video on how a modern turbo fan jet engine works right here so the simplest form of a turbo jet is made up of four parts an intake including a compressor the combustion chamber a turbine and a nozzle as long as the engine is running meaning as long as there is a supply of fuel the compressor is spinning sucking air into the engine where it gets compressed as it passes rotor and stator blades then the hot and pressurized air gets mixed with fuel and is burned in the combustion chamber the expanding and accelerated hot air then passes through the turbine which is made up of rotary blades which are mounted on the same shaft as the rotors of the compressor at the front of the engine or as you know it the fan and is finally blown out of the nozzle at a higher velocity than it was taken in by the fan resulting in a force that continuously wants to push the aircraft forward very simply speaking suck squeeze bang blow which pretty much breaks it down to the essence of how it works so in order to increase our force which in our case is our thrust output we must either increase the exhaust velocity or we have to get more air through the engine at the same time keeping that in mind let's have a look at commercial jet engines now this type of engine is called a turbo fan engine now turbo because the entering air is being compressed and turbo fan obviously because of the huge fan at the front of the engine which primarily accelerates the sucked in air and secondly to compress parts of it too it works just like the turbo jet but now has an additional fan a second compressor and a second turbine now besides that we now have two channels through which the air can pass through the inner channel called the core which is basically going through the actual engine and an outer channel between the core and the engine's casing which is called the bypass now the ratio between the amount of air passing through the bypass and the amount of air passing through the core is called the bypass ratio but more about that in a minute now the principle of suck squeeze bang and blow stays the same with the difference that the air is now sucked in by the fan and is split up into those two channels now the bypassed air is simply accelerated air by the fan and guided around the core to be blown out at the end the inner channel on the other hand leads the air through the low pressure and high pressure compressor and then into the combustion chamber where the compressed air is mixed with fuel and then ignited now the pressurized and hot air then expands and accelerates over the high pressure turbine which in return drives the high pressure compressor at the front of the engine and it also passes through the low pressure turbine which drives the low pressure compressor and the fan and after that the air is blown out of the engine exhaust in modern turbine fan engines over 80 percent of the thrust is solely provided by the bypass how is that possible you might think how can a fan that just pushes cold air around the actual engine provide far more thrust than a high-tech mix of compressors and turbines that burns fuel and air at temperatures that are sometimes even higher than the melting points of the components itself well the answer is simple the bypass ratio now remember to increase thrust we can either accelerate our air faster or put more air through the whole thing now trying to increase the exhaust velocity will at one point lead us to some military use solutions such as the afterburners but these technologies are sadly inefficient although they look fantastic hence concord now instead we rather try to put more air through the engine and the turbofan does exactly that for that purpose we need much larger intakes and as technology strives further the fans get larger and larger and therefore the engine size increases and engine manufacturers are constantly trying to increase efficiency and reaching higher bypass ratios by using modern manufacturing techniques and materials it is also worth mentioning that besides providing most of the thrust the bypass obviously surrounds the core with relatively cool air which has a cooling effect reduces engine noise and increases its efficiency now let's take a step back into reality and to get a little bit out of the world of physics let me show you some numbers the engine of a 737 200 as shown in the beginning of this video has a fan with a diameter of about 1.2 meters and it has a bypass ratio of 1.7 to 1 meaning 1.7 times of the air has bypassed around the engine compared to that that went through it it has an overall mass flow of 225 kilograms of air per second now that sounds like much in the first place but wait for the next engine the general electric 900 which powers the current triple 7 models has a fan diameter of 3.2 meters and a bypass ratio of 9 to 1. at takeoff it pushes 1 300 kilograms of air per second around the bypass let me say that again per second counter one and the air with a massive equivalent to an average compact car has passed through that engine and yes the triple seven has two of them the next big deal to come is the general electric 9x built for the next generation of the triple 7 x now by now it is the biggest turbofan engine ever made it has a fan diameter of 3.4 meters and is therefore with its engine casing wider than a 737 fuselage take that in for a minute in addition to that it has a bypass ratio of 10.1 to 1 and therefore pushes its efficiency even further if you think about it a turbofan jet airliner very basically speaking is a propeller driven plane think about that side question comment below the most famous turbo jet aircraft not turbo fan to have ever existed i'm excited to see your comments now that we have seen why the engine size increased over time the question arises are there any limitations to the size of the turbofan engine sure you might think it has to fit under the wing at least well that's not wrong ground clearance is definitely an important point but let's imagine we wouldn't worry about that and we could keep increasing the size and the engine's efficiency repeatedly so bigger fan more bypassed air and more thrust well and not quite imagine two race cars going in a straight line at the same speed suddenly they're coming towards a turn now they both maintain the exact same speed but the car on the inner lane of the turn will automatically end up overtaking the car on the outer lane and that's because the inner car has a greater angular velocity than the outer one to prevent itself from being passed by the outer car must increase its speed to reach the same angular velocity as the inner car and the same goes for the fan blades while having the same angular velocity the fan blade tip turns much faster than the root of the blade because of its greater distance to the shaft now by increasing the engine size you increase the diameter of the fan which puts the fan blade tips even further away now the low pressure compressor as well as every other turning component in the engine reaches its maximum efficiency at a specific rpm now because the low pressure compressor sits on the same shaft as the fan the rpm which may suit the compressor best can lead to supersonic speeds at the fan blade tips and that's not what you want propellers or fans have the characteristic that their efficiency decreases when they're spun too fast therefore the pratt whitney 1000g engine family powering for example the a320 neo are so-called geared turbo fans now instead of attaching the low pressure compressor and the fan to the same shaft a gearbox between the fan and the compressor is used to lower the fan rpm assuring that both the fan and the compressor can work at their most suitable rpm which decreases fuel burn and increases the efficiency a lot it's the sweet balance that make modern jet engines so efficient i have to say being a jet engine engineer for either rolls royce pratt whitney or general electric must be an incredible job trying to constantly push the physical boundaries but trying to keep it efficient and safe at the same time must be their drive to go to work every day ladies and gents i highly respect your work that's it today i hope you enjoyed this video make sure to check out my other video with more detailed information on how a jet engine works and here's your checklist for today subscribe to my channel check activate the notification bell check follow my instagram account check perform a touch and go at my website check and don't forget a good pilot is always learning wishing you all the best [Music] you

Channel: Captain Joe

Views: 511,623

Keywords: big jet engine, jet engine sound, captain joe, captain joe flying, Boeing 777x, Jet engine how it works, GE90x, Turbofan, Turbojet, Jet power, boeing 747, bypass ratio, jet engine power, some interesting aviation facts, bypass ratio in turbofan engine formula, ge90 startup, ge90 takeoff, jet engine power test ho, jet engine (invention), turbofan (engine category), turbojet, 1-spool engine, 2-spool engine, airplane jet engine sound, rc airplane jet engine

Id: 5kE9wxsxdfc

Length: 12min 21sec (741 seconds)

Published: Thu Oct 07 2021