Vaneless diffuser rotating stall based on two-dimensional inviscid flow analysis (2nd report, nonlinear analysis)

摘要

In the first report it was shown, by a linear stability analysis, that a vaneless diffuser rotating stall can be a manifestation of a 2-D inviscid flow instability subjected to vanishing velocity fluctuation at the diffuser inlet and vanishing pressure fluctuation at the diffuser outlet. The purposes of the present paper are to elucidate the nonlinear effects, to determine the factors which set limits on the amplitude of the fluctuation, and to obtain additional information, within the framework of 2-D flow analysis. Two dimensional nonlinear inviscid and viscous flow calculations are carried out based on the SMAC method. It was found that, (1) the critical flow angle and the propagation velocity determined from the linear analysis agree well with the present calculation, (2) viscosity in 2-D flow, wall friction, and resistance at the diffuser outlet can be the factors that set limits on the amplitude. Reasonable agreements with experiments were obtained, and a discussion is presented as to the energy transfer from steady flow to disturbances.