Flow stability model of centrifugal compressors based on eigenvalue approach

A stall inception model of centrifugal compressors is developed on the basis of the global stability analysis in the present paper. This model takes specific flow patterns and impeller geometry into account, which can be used to analyze the effect of blade design parameters on the stall limit of centrifugal compressors. In particular, the body force model and the solution of the stability eigenvalue equation are two important problems to be addressed in this frame. The spectral method and singular value decomposition are used to discrete stability equations to obtain the eigenvalues. By applying conservation laws, a perturbation-response form of the body force, specifically for centrifugal compressor, is also established to simulate blade behavior. Two different forms (the meridional model and the normal expansion model) are derived to make a comparison of grid independence and computation time. The capacity of these models is assessed against the experimental data of a NASA low-speed centrifugal compressor rotor. The results show that these models could be used to predict stall onset with acceptable accuracy and low computational cost.