Experimental and numerical investigations on effects of vaned diffuser on performance of centrifugal compressor

Three vaned diffusers for a high-pressure-ratio centrifugal compressor are designed, and the effects of inlet blade angle and blade profile of diffuser on the stage performance are investigated by the experiment and numerical simulations. The results show that, the decrease of inlet blade angle makes the performance curve move towards the low flow rate side, and the little drops of the peak stage efficiency and pressure ratio can be detected. The low-solidity airfoil diffuser can enlarge the operating range of stage, but decreases the stage efficiency and pressure ratio remarkably. The further flow analysis show that, decreasing the inlet blade angle leads to the spread of flow separation zone, the blockage of flow channels and the increase of losses. The large-scale flow separation is more likely to generate when the low-solidity airfoil diffuser is adopted.