Numerical and experimental research on different inlet configurations of high speed centrifugal compressor

Three different inlet configurations, including a original straight pipe and two bend pipes with different axial length, for a high speed low mass flow centrifugal compressor were modeled with whole blade passages and simulated unsteadily by 3D viscous Navier-Stokes equations. The performance disparities of compressor stage were tested and verified by experiments in which dynamic pressure data acquisition of internal flow field was performed. As the result shows, the choke point decreases to lower mass flow rate due to the distortion caused by bend-pipe inlet and is aggravated as the rotation speed increases. The distortion effect spreads circumferentially in impeller and makes the flow structure varied. The longer axial distance bent inlet leads to larger radial distortion and heavy blockage at mid-span under large mass flow mainly causes compressor choke margin narrowed. Bend pipe distortion brings an impact up to diffuser on unsteady pressure pulsation caused by blades sweep and the impact appears more powerful when it is closer to volute tongue.