This has really got me confused lately. I’ve read online that it increases efficiency, the potential energy of the air and helps with combustion, but my question is:
If the same amount of air is passing through the engine regardless, why pressurise it? Wouldn’t the gain in PE of the air just be equal to the loss of KE of the aircraft due to the air hitting/dragging the aircraft back as it’s compressed? I’m almost certain I’m wrong here, but any explanation which could clear this up for me would be great thanks.
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You HAVE TO compress it, it’s fundamentally how jet engines work. No compression, no jet engine.
It’s been a while since I’ve done this, but I’ll do my best to explain it. Jet engines (and power plants) work by abusing physics. As it turns out, air has different properties at different pressures. So by pressurizing the air, we change the properties as it burns. This allows us to get way more energy out than it takes to run the compressor. If you didn’t compress it, you’d only be able to only get the amount of energy it takes to run the compressor out (in theory, in reality it’s way less).
Look into thermodynamic cycles, specifically the Brayton cycle (what jet engines use). If you’d like, I can look this up in my textbook and give a more detailed answer if you’d like.
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