Stability Improvement Of Turbocharger Centrifugal Compressor By Asymmetric Vane Diffuser Treatment

Demanding for energy reduction and increasingly stringent emissionsregulations of internal combustion engines put forward higher requirements onthe stable flow range of turbocharger centrifugal compressor. The stability of acentrifugal compressor become one of the major bottlenecks in the developmentof turbocharging technology.The asymmetric volute resulting in an asymmetric flow field in theturbocharger centrifugal compressor at off-design conditions. The conventionalcentrifugal compressor flow control methods ignoring the asymmetric flow fieldin the centrifugal compressor, which is far away from the real. Based on theintrinsic asymmetric flow field in the centrifugal compressor, TsinghuaUniversity proposed an “asymmetric flow control” method. Diffuser has animportant impact on the stability of centrifugal compressor. Based on the“asymmetric flow control” method, the asymmetric vane diffuser flow controlmethod is studied and explored, to extend the flow range of vane diffusercentrifugal compressors for turbochargers.In order to quantify the distortion induced by the volute, a distortion modelwas proposed to replace the volute by imposing a circumferentially asymmetricpressure distribution. The simulation results proved this model well reproducedthe distortion induced by the volute and therefore was sufficient for the researchon the volute’s effect. Based on the distortion model, variable amplitudes ofdistortion were realized and the influence of the amplitude of the distortion onthe performance of centrifugal compressor was studied in detail. The resultsshow that the distortion severely harms aerodynamic stability of the investigatedcompressor. The larger the amplitude of the distortion, the worse theperformance of the compressor. The distortion induced by asymmetric volutepropagates to upstream components and causes local flow separations at part ofdiffuser and impeller, leading to the compressor surge.Based on the influence of the distortion on the performance of centrifugalcompressor, a circumferentially non-axisymmetrical installation angle or solidity of diffuser vanes are first proposed to extend the stable flow range ofthe centrifugal compressor. Both numerical and experiments were conducted ona designed asymmetric vane diffuser turbocharger centrifugal compressor. Theexperimental results show that the stable flow range of the vane diffusercentrifugal compressor at90%rotational speed is extended from25.4%to33.1%.