Couldn’t the compressed air by itself make a plane fly? Or does it need that extra energy from the combustion chamber to make a plane fly?
In: Engineering
I’m assuming you’re talking about like on a commercial airliner, which uses a turbofan jet engine.
The combustion chamber is what is generating the energy to drive the fan to begin with, so it is quite necessary. It needs to be turned somehow! With a regular old engine that would just be a propeller plane, or using the turbine separate from the fan would be a turboprop.
What it comes down to is this: propeller planes are good for lower speeds, we’ve had them for a century now. The jet engine comes along (in the form of the turbojet) and revolutionizes airplanes as now they can go fast — *really* fast. But turbojets (where all the air goes through the gas turbine engine itself) were not very good at lower speeds. So a turbofan combines the “propeller low speeds” and the “turbojet high speeds” into a medium speed engine perfect for commercial airliners that want to go fast but not *too* fast.
So why not use just the air from the fan itself? Because of that medium speed they want, and because if the jet exhaust isn’t also being used to go forward, that’s wasted energy, Just like how the heat in the exhaust or the radiator of your car is energy that got wasted by not going to the wheels. Turbofan engines put 100% of energy produced into propulsion (minus frictional losses and any power sipped off to run the airplane electric system and cabin pressurization).
It’s efficient and it’s right in the perfect performance zone for a 747.
Latest Answers