1. Aerodynamic stability of a compressor

1.1 Compressor types concerned

Pumping is an aerodynamic instability of the flow in the machine, accompanied by a reversal in the direction of flow. The compressors concerned by this phenomenon belong to the family of turbomachines, or so-called "dynamic" machines, including axial, centrifugal and mixed (helical-centrifugal) compressors. Their common feature is that no internal technological device can oppose counter-current flow (as opposed to the valves of reciprocating piston compressors, for example).

In these machines, the dynamic effects leading to pressure rise are a succession of accelerations and decelerations imposed on the gas by rows of blades.

In axial compressors, the rows of rotating blades impart kinetic energy to the...