Simulation Of Impacts On Performance Of The Centrifugal Compressor With High Pressure Ratio By Self-recirculation Casing Treatment

A high-performance turbocharger demands its centrifugal compressor has highpressure ratio, high flow capacity, high efficiency as well as a good stability. While ahigh-pressure-ratio centrifugal compressor always has a poor flow capacity, and anarrow stable operating range. According to this problem, self-recriculation casingtreatment for the high-pressure-ratio centrifugal compressor is designed in this paper,and also a study on the influence on centrifugal compressor by structure sizes of thedevice is made. The thesis mainly includes:Based on a centrifugal compressor with a maximum pressure ratio5.2, and alsorely on NUMECA commercial software, compressor characteristic of centrifugalcompressor with impeller and vaned diffuser under high, medium, low speed issimulated. Judgment methods of the turbulent boundary and clogging boundarywithin simulation are obtained.Structure size of the self-recriculation casing treatment suited for thathigh-pressure-ratio centrifugal compressor is designed. By numerical simulation,effects on broadening the stable operating range and increasing the surge margin ofthe compressor by different structure sizes of the self-recriculation casing treatmentare studied.A suitable structure size for the compressor is chosen by the simulation ondifferent structure sizes of the device. Compressor characteristic with the device underhigh, medium and low speed is obtained. By comparing the results, effects onbroadening the stable operating range and increasing the surge margin by the device isobtained.Through the analyzing the internal flow field of the centrifugal compressor, it isfound that using the bleed air recirculation device, relative Mach number at the inletof the compressor has been more even, the local flow acceleration of the main bladeleading edge has been weaken, positive attack angle at the inlet of the blade has beensmaller, the boundary layer separation in blade surface has been inhibited.In this paper, influence on the centrifugal compressor with high pressure ratio bybleed air recirculation device is studied. With the self-recriculation casing treatment, efficiency under each speed decreases about1.5%, stable operating range broadensmore than15%, surge margin increases11%. The stable operating range is broadenedas well as the surge margin is increased at the same time while keeping the highefficiency.