The operating range of any compressor is limited on the high flow side by the choke region and on the low flow side by surge. Sometimes a phenomenon called rotating stall further limits the operating range of the compressor. Compressors will surge when forward flow through the compressor can no longer be maintained due to an increase in pressure across the compressor, and a momentary flow reversal occurs. Choke, on the other hand, is simply a very high flow point on the compressor's map where the total amount of energy available to the impeller is utilized for pumping gas, but at a very low head or pressure ratio. Flow separation, stall, and rotating stall may be detectable by monitoring shaft vibrations, especially in high pressure machines.
The Compressor Operating Range: Surge, Stall and Choke Klaus Brun; Rainer Kurz Mechanical Engineering; May 2009; 131, 5; Docstoc pg. 52 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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