Investigation Of Internal Flow Field Characteristics Under Inlet Distortion In Dual Boost Compressor

The dual boost centrifugal compressor with different intake condition is a newmechanical supercharger. Because of its small size, transient response and a wide operatingrange, this kind of compressor, with a very great potential and prospects, is being valuablein the field of automotive turbochargers. Due to limited by the turbocharger mountingdimensions and forms of organization on the engine, the inlet air in compressor is suppliedby a common intake pipe. However, the intake forms between the two side of impeller arequite different: the front impeller is supplied by a short straight pipe intake, with a lessertotal pressure loss; and the rear impeller is supplied by the complex shape of the bendingpipe, which causes the rear impeller inlet total pressure loss greater than the front impellerand the velocity distribution is not uniform that there exists an inlet distortion near the rearimpeller inlet. Furthermore, the rear inlet distortion is provided with a strong ability tospread in the passages of rear impeller, which makes a non-axisymmetric distribution in theflow field of rear impeller passages. In this paper, the numerical simulation method hasbeen carried on for the dual boost centrifugal compressor with different condition toanalyze the internal flow field under the distortion condition.First, on the base of dual boost centrifugal compressor model with re-circulatingcavity, the model without the re-circulating cavity and the performance curve can be got.Compared with the solid casing model, the study shows that the casing treatment model isless susceptible to the influence of the complex rear inlet pipe and the compressor canoperate steadily for a wide range in the parallel mode.Then, by analyzing the flow distribution between the rear pipe and the distortionspreading characteristics, it indicates that the air flow distribution is unbalanced betweenthe rear pipe under small flow condition. Besides, the distortion can spread to thedownstream through the blade channels, which results in the different mass flow in bladechannels and affects the stable operating status of dual boost compressor.Last, to investigate the common diffuser flow loss caused by the total pressuredifference between the double sided impeller of dual boost compressor, the details of theflow field for dual boost compressor has been studied. The results show that the flow loss exists in the common diffuser because of the pressure difference. With the increasing of theinlet pressure, the flow loss becomes larger. Moreover, the main diffuser loss is the exhaustmixing loss of double sided impeller under the large mass flow condition; On the smallmass flow condition, the wall separating vortex loss is more obvious in the diffuser.