Unsteady characteristics on inlet distortion of bend-pipe of centrifugal compressor

Inlet distortion from 90°bend-pipe of turbocharger centrifugal compressor was investigated by numerical simulation. Performance of compressors with two different axial position bend-pipe inlets was compared and the internal unsteady flow was analyzed by frequency-domain method. Results show deterioration in performance strongly depends on position of bent pipes, and large influence is presented in the case where impeller has long distance to bent pipe outlet. Distortion makes noticeable decline in compressor performance under large mass flow and slight drop under low mass flow. The pressure fluctuation at impeller inlet is increased because of bend-pipe distortion, altering the frequency spectrum structure of impeller upstream and tip clearance, and resulting in enhancement on rotor dominant frequency amplitude. The distortion also makes the blade vibration and aerodynamic noise at tongue especially at low mass flow rate.