![]() In many cases however, the compressor airfoils are critically loaded without capacity to absorb the disturbance to normal airflow such that the original stall cells affect neighbouring regions and the stalled region rapidly grows to become a complete compressor stall.Īxi-symmetric stall or compressor surge Īxi-symmetric stall, more commonly known as compressor surge or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor's inability to continue working against the already-compressed air behind it. Local stalls substantially reduce the efficiency of the compressor and increase the structural loads on the airfoils encountering stall cells in the region affected. Stable local stalls can also occur which are axi-symmetric, covering the complete circumference of the compressor disc, but only a portion of its radial plane, with the remainder of the face of the compressor continuing to pass normal flow.Ī rotational stall may be momentary, resulting from an external disturbance, or may be steady as the compressor finds a working equilibrium between stalled and unstalled areas. The adjacent blade stalls as a result of the incidence spike, thus causing stall cell "rotation" around the rotor. Propagation of the instability around the flow path annulus is driven by stall cell blockage causing an incidence spike on the adjacent blade. The stall cells rotate with the rotor blades, but at 50 to 70% of their speed, affecting subsequent airfoils around the rotor as each encounters the stall cell. The stalled airfoils create pockets of relatively stagnant air (referred to as stall cells) which, rather than moving in the flow direction, rotate around the circumference of the compressor. ![]() Rotating stall arises when a small proportion of airfoils experience airfoil stall, disrupting the local airflow without destabilising the compressor. Rotating stall is a local disruption of airflow within the compressor which continues to provide compressed air, but with reduced effectiveness. An animation of an axial compressor showing both the stator blades and the rotor blades
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