Precalculation of rotating stall in multistage axial compressors

The present investigation is concerned with the development of a nonlinear model for predicting rotating stall. Previously, the nonlinear model could only be employed in cases involving a single stage. An analysis of the effects found in cases involving several stages makes it possible to adapt this model for a precalculation of the rotating stall in a multistage compressor. The boundary conditions in the model developed by Takata and Nagano (1972) and in the model reported by Orner (1979) make it impossible to consider the effects of a use of several stages. In the current investigation, an 'interface' is used to consider the influence of adjacent stages. The obtained nonlinear model is employed in the case of a single-stage design and a two-stage design. It was found possible to calculate the important data, including the beginning of rotating stall, the rotational frequency of the stall cells, and the left branch of the characteristic. A basic problem in the case of a nonlinear model of the rotating stall is related to the continuous increase in the amplitude of the stall cells.