A Theory for Predicting Stall Cell Transient Behavior

In this paper, a new model is developed for rotating stall in low speed axial compressors and fans. The theory is developed from Moore’s theory. The modified model makes it possible to predict the transient behavior of the stall cells, which is not possible with Moore’s theory. The general assumptions such as the layout of the compression system, the lags in the entrance and exit ducts, and the small disturbances are assumed to be similar to those of Moore’s theory. However, a second order hysteresis is used in the current work for the pressure rise of the rotor and stator rows. Comparing the experimental results with the theory shows that the modified model can predict the transient behavior of the stall cells fairly accurately. Furthermore, the current model makes it possible to study the effects of different parameters such as the stagger angle, number of stages, and number of stall cells. It has been suggested in the current study that the number of stall cells should reduce to one in a fully developed rotating stall pattern.