Rotating Stall and Surge

Safe off-design operation of compressors is limited to the region in which the flow is stable. Flow instabilities can be of two types, rotating stall and surge. The first of these subjects the blading to high oscillating stresses while the second may also have a disastrous effect on the whole system of which the compressor is a component. In this paper, the properties of these two types of instability are discussed and some simple criteria for determining system stability are presented.