The effects of the U-shape pipe on a centrifugal compressor were investigated with experimental and numerical simulation methods. Compared with straight pipe inlet

the bend pipe resulted in a significant performance degradation of the compressor at the high mass flow rate. The pressure ratio and efficiency dropped by 10% and 18%

respectively. The numerical results show that the distortions of the static pressure and the total pressure were generated at the outlet of U-shape pipe. The pressure distortions were induced by the circumferential nonuniform geometry of downstream compressor volute. When transported to the upstream blade channels

the outlet pressure distortions encountered with the inlet pressure distortions. These coupled distortions changed the flow structure and inlet conditions in the impeller inlet

and also the mass flow rates distribution in the blade channels. The entropy increase existed at the distortion regions of the impeller. Meanwhile

the mean load of whole main blades increased about 8% due to the variations of the static pressure distribution at main blade surfaces.