On the Partial Flow Rate Performance of Axial-Flow Compressor and Rotating Stall : 2nd Report, Influences of Impeller Load and a Study of the Mechanism of Unstable Performances

Abstract

Two experimental investigations of the off-design operations of axial-flow compressor are described. One of them is an investigation of influences of impeller load on both partial flow rate performances and the rotating stall characteristics, the other being an attempt to make clear the mechanism of the unstable performance related with rotating stall. The width of the rotating stall regions and a decrease in discharge pressure in the partial flow rate region become small as the impeller load decreases. When the impeller load becomes so small that rotating stall completely disappears, the slope of the performance curve becomes negative at all flow rates. It is clear that the reverse flow of rotating stall (large stall) reverses from delivery to suction side across the rotor. The mechanism of the reverse flow is discussed and it is shown that the reverse flow is the cause of the unstable performance.