Limitation of the Propeller in Propulsion
In
order to maintain good flow over the blade certain conditions must be meet.
1. The relative approach
angle and the blade leading edge angle must be close to
prevent flow separation from the blade.
2. The turning angle must be
keep quite small, or the flow will also separate from the
blade.
3. The relative approach
velocity must not be too close to the speed of sound. This is to prevent shock waves from forming on the blade.
Thus conventional propellers are used for flight speeds well
below the speed of sound; usually at or below 135 m/s (300 mph).