Influence of Rotor Blade Stagger Angle on Rotating Stall Inception in an Axial-Flow Fan

Abstract

Pressure fluctuations on the casing wall of an axial flow fan were measured. These measurements were used to investigate the inception of rotating stall at different rotor-blade stagger angles. Near the peak of the pressure rise, stall cells formed around blades with the design stagger angle as well as around blades with a larger stagger angle. When flow rate was decreased, the stall cells were developed in the case of the design stagger angle, but not developed in the case of the larger stagger angle. Rotating stall was not observed in the case of a smaller stagger angle untill the flow rate was much lower than that at the peak pressure rise. It was confirmed that the formation and development of stall cells were affected by the throat length of the rotor blade passage and the pressure fluctuation magunitude.