Study on stability extension using pre-swirl and variable diffuser for centrifugal compressor

For a centrifugal compressor with vaneless diffuser, designed inlet guide vanes and adjustable diffuser, the centrifugal compressor performances in different conditions of using pre-swirl, settled diffuser and pre-swirl, variable diffuser and pre-swirl etc. were simulated to investigate the centrifugal compressor stability extension characteristics by pre-swirl and variable diffuser. The results show that using pre-swirl can widen the surge margin by 16.7% with keeping the max. efficiency unchanged simultaneously, and using vane diffuser, the max. efficiency of the compressor increases by 1.7%. On the basis of centrifugal compressor with vaneless diffuser, using both pre-swirl and variable diffuser can widen the surge margin and improve the compressor efficiency by 1.2%.