Numerical Study of the Different Outlet Angles of Diffuser and Performance of Centrifugal Compressor

Based on the first stage of centrifugal compressor,the effects of outlet angles of diffuser on the stage performance were investigated by the numerical simulation.The performance curves at stage with different outlet angle were measured.The internal flow and the total pressure loss on the stage were analyzed,and by comparison of pressure recovery coefficient of different vaned diffusers to judge diffusion effect.The results show that the increase of outlet angle makes the performance curve move toward the large flow rate side,and the peak stage efficiency and pressure ratio increase firstly and then decrease.The diffusion effect of vaned diffuser depends upon flow condition during different operations.When the flow mass is larger than the design level,the separation zone generates near the shroud of diffuser,and the different vortex regions enlarge with the outlet angle of diffuser.When the flow mass is smaller than the design level,the separation zone is firstly emerged in large outlet angle at vaned diffuser.