The Effects of Blade Loading on Trailing Edge Vortex Formation on a Highly Loaded Stator Upstream of a Transonic Rotor

Abstract

Multiple high-fidelity time-accurate computational fluid dynamics simulations were performed to investigate the effects of upstream stator loading and rotor shock strength on vortex shedding characteristics in a single stage transonic compressor. Three loadings on the upstream stator row of decreased, nominal, and increased were studied. The time-accurate URANS code TURBO was used to generate periodic, quarter annulus simulations of the Blade Row Interaction compressor rig. It was observed that vortex shedding was synchronized to the passing of a rotor bow shock. Results show that vortex size and strength increase with stator loading. “Normal” and “large” shock-induced vortices formed on the stator trailing edge immediately after the shock passing, but the “large” vortices were strengthened at the trailing edge due to a low velocity region at the suction surface. This low velocity region was generated upstream on the suction surface from a shock-induced thickening of the boundary layer or separation bubble. The circulation of the “large” vortices was greater than the “normal” vortices by a factor of 1.7, 1.9 and 2.1 for decreased, nominal and increased deswirler loadings. At decreased loading only 24% of the measured vortices were considered “large” while at nominal loading 58% were “large”. An understanding of the unsteady interactions associated with blade loading and rotor shock strength in transonic stages will help compressor designers account for unsteady flow physics at design and off-design operating conditions.