Vortex-Lift Mechanism in Axial Turbomachinery with Periodically Pitched Stators

Abstract

Conventional aerodynamic theory of lift is based on the Kutta–Joukowski condition, in which the lift and drag coefficients are predicted based on the assumption that flow is attached and steady-state. Recent research on insect flight indicates, however, that the unsteady motion of a wing can generate much higher unsteady aerodynamic force through the flow induced by the shedding vortices. In the present work, therefore, we propose a novel type of stage consisting of rotor and periodically pitched stator to take advantage of unsteady vortex lift. The numerical results suggest that the flowfield around the leading and trailing edges of the blades are substantially modified by the interactions between the rotor and pitching stator. Several transient lift peaks can be generated for each period. If an appropriate pitching phase is chosen for the stator, stage performance can be improved through unsteady lift mechanism effects.