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I want to start out by saying these questions will make me look a fool but i simply haven't found answers for them anywhere so i'm hoping you could help me!
What is the purpose of bypass ducts? If the air is going around the turbine then what even is the point? Why not just make jet engines simple consisting only of the turbine and skip out on the bypass duct?
What makes the fan blades in a jet engine keep spinning? I know how they are started but what keeps the blades constantly spinning with enough inertia to keep compressing air? Is there like a small motor connected to the fan blades via a crankshaft or is a portion of bleed air used to keep the blades in motion?
Thanks in advance for answering my questions :)