PRESSURE OSCILLATIONS OCCURRING IN A CENTRIFUGAL-COMPRESSOR SYSTEM WITH AND WITHOUT PASSIVE AND ACTIVE SURGE CONTROL

A study of pressure oscillations occurring in small centrifugal compre ssor systems without a plenum is presented. Active and passive surge c ontrol were investigated theoretically and experimentally for systems with various inlet and discharge piping configurations. The determinat ion of static and dynamic stability criteria was based on Greitzer's ( 1981) lumped parameter model modified to accommodate capacitance of th e piping. Experimentally passive control using globe valves closely co upled to the compressor prevented the occurrence of surge even with th e flow reduced to Zero. Active control with a sleeve valve located at the compressor was effective brit involved a significant component of passive throttling which reduced the compressor efficiency. With an os cillator connected to a short side branch at the compressor, effective active control was achieved without throttling. Bath methods of activ e control reduced the flow rate at surge onset by about 30 percent. In general, the experiments qualitatively confirmed the derived stabilit y criteria.