A 3-D Simulation of Flows in Axial Rotors with and without Tip Clearance

Abstract

Full three-dimensional simulations of incompressible stalled and stall-free flows in a single stage axial rotor with and without tip clearance are presented in this report. The simulation are conducted for one flow passage between blades assuming periodicity in circumferential direction, and hence rotating stall is not considered presently. Effect of centrifugal force which manifests itself seriously in the flows in axial rotors, particularly in stalled flow is of present concern. Comparing with the counterpart flow in stationary straight cascades for similar inlet flow conditions which are mentioned in the accompanying paper, basis of models required to make two-dimensional simulation which is far small in computational load possible to predict onset of unstable fluctuating flow in an axial rotor are expected to be established. It is revealed that due to centrifugal force, separated flow at the blade leading edge is pushed toward casing wall and sheds intermittent vortex tubes, inducing high fluctuation in the flow. Unsteady separation with fairly long period is crucial in the understanding of the flow in the case of stalled rotor.