Fuel with Static Air in a Jet engine

[TheBusFlyer]

Good evening,

Today's planes' need bleed air to start. Above a certain speed, igniters fire up and we inject fuel inside the combustor chamber. Why do we need to have the engine running to inject fuel (around 20%N2)? Can we simply not inject fuel with static air (i.e. when engine is not running)? What would happen if I would do so?

Thanks a lot!

 

[CWatters]

Jet engines work by compressing the air then injecting fuel. The resulting hot gasses expand rushing out the back turning a turbine that's connected to the compressor at the front.

This process only becomes self sustaining above a certain minimum speed (rpm). Below that speed the power generated isn't enough to run the compressor, fuel and oil pumps and shift the air that is going through the bypass.