I’m sure most of us at some stage have been sitting in an aeroplane staring blankly out the window and wondered to ourselves how the big shiny thing bolted to the wing turns fuel into thrust. It may surprise you but the way which jet engines work are a lot simpler than you may realise. In this video I will explain to you the basic operation of how jet engines work.
*Roll title*
In this video I will be referring to an axial jet engine, which is the most common type, axial meaning that the air flows along the axis of rotation of the engine, rather than a centrifugal jet engine in which the air flows in and then out to the sides although the principle is exactly the same.
While there are many different types of jet engines, the operation of all of them boils down to 4 simple steps:
Suck, squeeze, bang, blow.
Now you won’t be forgetting that in a hurry.
The first part, suck, refers to the air surrounding the intake being sucked into the engine, the intake being the big hole at the front which allows the air to enter. This is helped by the forward motion of the aircraft through the air, causing what is called “Ram Air,” essentially air being forced into the intake as it acts like a big scoop when the aircraft is in flight.
The next part, squeeze, is the air which has entered through the intake being compressed by a part of the engine called the...compressor. This is done by a series of fan discs, called rotors, set in stages, each smaller than the previous, all joined together and forming a duct which gradually narrows. In between these rotors is a stator vane, a matching fan disc which as the name suggests remains stationary. There can be as many as 20 of these disc pairs. The result of this process is the gradual compression of the air. This will increase the velocity of the air through the engine which allows us to transform all that potential energy into something useful which brings us to our next step.
Bang! In the next section, the rather cool sounding Combustion Chamber, fuel is sprayed into the high velocity airstream where it is ignited, initially by an igniter plug which causes a very strong spark to ignite the fuel and then by the already ignited fuel as the engine becomes “Self Sustaining.” This is when the already ignited fuel will ignite more fuel which will in turn ignite more fuel and so on, much like holding a lighter up to a spray can. This process will release a huge amount of energy! Think of it as a controlled explosion. All the expanding gasses have to go somewhere and as they cannot go forwards through the engine due to all the air rushing through, they must go backwards which brings us to our final step.
Blow. All the rapidly expanding gas is blown out on to another set of rotors and stators called the “Turbine”. There is usually only 3 or 4 pairs of discs here and their primary purpose is to spin the compressor. Once the gasses have passed through the turbine, they are then blown out the back of the engine, through a section called the exhaust, in a high velocity jet of air used to propel the aircraft forwards.
So as you can see, the jet engine works as a cycle with the air being sucked into the engine and compressed, then fuel is introduced and ignited which drives the turbine which in turn drives the compressor, sucking more air in which continues on and on with the result being thrust and a lot of it.
