ENDWALL BOUNDARY LAYER CONTROL IN COMPRESSOR CASCADES

摘要

Recent investigations have shown a reduction of secondary losses in compressor cascades using a bulb like modification of the profile at the endwall. This paper is focussed on experimental work in comparison of 5 different endwall modifications at a compressor cascade. The cascade is modified near the endwall with a bulb, a medium and a large fillet. The fillet configurations are modified by an axial blunt cut-off at the leading edge. The investigations have been carried out at a profile developed from a hub section of the Dresden Low Speed Research Compressor (LSRC) blade, a compressor profile with a nominal turning of 18 deg. A datum configuration and the 5 other configurations were tested at the Low Speed Cascade Windtunnel (LSCW). For the bulb configuration, an intensified horse shoe vortex was suspected and observed counterrotating to the passage vortex with an influence on its propagation. The interaction of the passage vortex and the suction side profile boundary layer is influenced. The superposition of both is minimized and the losses developing from this effect are significant lower. For the fillet and blunt-fillet configurations, a fillet vortex develops and was observed co-rotating to the passage vortex with an influence on the mentioned interaction as well. Blunt leading edges produce additional losses but the superposition of the growing vortices may reduce the overall losses. The cases show a reduction in losses of 1.9% for 3 deg incidence and a range of 1.2% rise to 1.9% reduction in dependence of the incidence. This equals a reduction of the isolated secondary losses up to 28% with respect to the reference profile. Detailed results of the experiments are presented for the reference and all modified cascades.