Numerical Study On The Flowfield Inside Centrifugal Compressor Stage With Different Diffusers

In recent years, study of multistage internal flow has become one of the major research areas in turbomachinery aerodynamics. In comparison with the axial turbomachinery, internal flow in centrifugal compressors is more complex, and the achievement in centrifugal compressors is left behind of their axial counterpart. Furthermore, many questions concerning the 3D flow structure in centrifugal compressors are yet to be solved. This dissertation develops research work on a sort of centrifugal compressor stages, Numerical simulation on three-dimensional viscous flow fields of centrifugal compressor stages are carried out using Baldwin-Lomax algebraic turbulent model. The velocity and pressure distributions are obtained by employing Reynolds-Averaged N-S equation. This thesis tries to carry out a deeper investigation in the following aspects:Periodic gas about geometrical model of centrifugal compressor is set up from NUMECA software package, which is used in flow calculating. under several Mach numbers numerical simulation using NUMECA software package is carried out for a centrifugal compressor with vane-less diffuser, such as 0.8, 0.75, 0.65, 0.55,etc. the simulation be developed in a steady condition which can be also compressed. analyze the homologies and the differences of the characteristic curve of the same operating mode from comparing with experimental results under every mach numbers. Through analyzing the flow field detailedly inside impeller, vaneless diffuser and return channel, it is found out the reason why performance drops in some other operating modes.Numerical simulation about three sorts of centrifugal compressors with different straight plate diffusers are developed under 0.8 mach. Launch a comparison about their efficiency and absolute pressure ratio, and analyze the flow inside impeller, vaneless diffuser and return channel, show the reason about every model is good or bad, find out that compressor with half of height vane near shroud in diffuser is the best one.The results are meaningful to both theoretical research and industrial application, and they provide useful data for analysis of loss in the stage and further development of a new basic stage.