Operating envelope of axial compressor?

Question

at extremities of the operating envelope of the axial compressor it may stall or surge. what conditions cause this ?? please I need help

Answer 1

Your having us on right?

Answer 2

The compressor blades on an axial compressor are basically just wings moving around in a little circle.  They are cambered and have an angle of attack just like the big wings.  Because of that, they can actually exceed a critical angle of attack when at high pitch angles or when airflow into the engine gets disrupted by aerodynamic forces (extreme turbulence, high-speed mach buffets, etc).

When the fan blades begin to stall, a high pressure zone of airflow develops in front of the blade hampering the smooth flow of air into the rest of the engine blades, worsening the problem.  

Your fan blades are basically just little propellers, and at high pitch angles, they can actually stall.  Remember that angle of attack on blades, just like wings, is not dependent solely on aircraft deck angle.  Angle of attack is the difference between the relative wind and the chord line of the blade and can differ significantly from aircraft deck angle.  Just like your props, the angle of attack on the descending side will be greater than the AoA on the ascending side, so that tends to force the stall to one side of the engine intake resulting in an asymmetric situation.

Answer 3

No Rose he's not having us on. It's a great question. Compressor stall occurs because of dissruption on the inlet air. Can be caused by extreme pitch attitudes or heavy water injestion.