Thrust by passage of air through a duct??

Question

Folks how is thrust obtained by the passage of air through a simple duct in a jet engine??

Answer 1

It is not the mere passage of air through a complex, not simple duct that produces the thrust of a jet engine.  It is the introduction of air and fuel into a combustion chamber from which the hot, expanded gases exit rearward that produces it.

A ramjet engine is closer to a simple duct and still relies on the expansion of a  burning fuel-air mixture to produce thrust.

All classes of jet engines, and there are others not mentioned, rely on the expansion of gases caused by burning an air-fuel mixture to produce thrust.  There is no mechanical reason that a jet engine could not have intakes pulling in air from the rear rather than the front.

Answer 2

In it's simplest form, a jet engine works like this. Suck, squeeze, bang and blow.

Answer 3

Simple answer - Newtons 3rd Law of Motion: "Every action has an equal and opposite reaction".

Therefore the act of blasting hot gas and air out of the back of a jet engine, pushes then engine forward; i.e. thrust. The same effect is seen with water causing hose pipes to move about - it is the same principle!