A theory for rotating stall in contra-rotating fans

Abstract

This paper reports on a theory of rotating stall in contra-rotating fans and compressors. The theory is developed from Moore’s theory. A second-order hysteresis is used in the current study for the pressure rise of the counter-rotating rows. This enables the model to predict the transient behavior of the stall cell. Comparing the experimental results with the theory shows that the modified model can predict the speed of the stall cells fairly accurately. Results show that the rotor speed ratio plays a critical role in the stall cell speed and its direction of rotation. Furthermore, the developed model makes it possible to study the effects of stagger angle and number of stall cells. The conditions under which pure rotating stall can occur in contra-rotating fans are also discussed in this paper. It is shown that the stall cells merge to form a single cell before a stable fully-developed rotating stall is established.