Particle Image Velocimetry Analysis on the Effect of Stator Loading on Transonic Blade-Row Interactions

Abstract

Experiments were performed to investigate interactions between a loaded stator and transonic rotor. The blade row interaction (BRI) rig was used to simulate an embedded transonic fan stage with realistic geometry (thin trailing edge), which produces a wake through diffusion. Details of the unsteady flow field between the stator and rotor were obtained using PIV. Flow-visualization images and PIV data that facilitate analysis of vortex shedding, wake motion, and wake-shock-interaction phenomena are presented. Stator wake and rotor-bow-shock interactions were analyzed for three stator/rotor axial spacings and two stator loadings. Specific shed vortices and wake topological features were isolated for each configuration. The data analysis focuses on measuring the vortex size, strength, and location as it forms on the stator trailing edge and propagates downstream into the rotor passage. It was observed that vortex shedding is synchronized to the passing of a rotor bow shock. Results show that the circulation of a vortex increased by 19% to 23% from far to close spacing due to the increased strength of the rotor bow shock impacting the stator trailing edge. Reduction in stator loading decreased shed vortex circulation for the same stator/rotor axial spacing by 20% to 25%. Pitchwise radius of vortices also decreased by 13% to 19% from far to close spacing. Such changes in vortex size and strength should be accounted for to predict the effect of unsteady blade-row interactions on transonic compressor performance.