The influence of non-axisymmetric end wall in a high-load compressor stage with tandem stator

The application of tandem blade in compressors has been study for decades. According to the open literature, using tandem blade can effectively extend the working range of the compressor under high incidence. Many earlier researches focused on the two-dimensional influence of tandem blade, and revealed that a proper arrangement on the positions of the front and the rear blade would allow the boundary layer on the suction side to develop in a more favourable way to control the two-dimensional separation. However, because of the serious corner separation and higher loss in the end wall region of high-load compressors. Some recent researches started to focus on the three-dimensional flow for further understanding the effect of the tandem setup. As an effective way to influence the end wall flow, the profiled end wall can be applied to both turbines and compressors to reduce the end wall loss. However, the co-work of tandem blade and profiled end wall was seldom reported. In this paper, a numerical research was carried out based on a single-stage high-load compressor with a tandem stator. After a numerical study for the hub separation. A series of optimization design were carried out for the hub end wall of the rotor, stator and the stage to improve the overall efficiency. The discussion revealed the positive effects of the optimum profiled end wall on the tandem stator were on one hand to limit the extension of the recirculation region of the front passage and on another hand to suppress the suction side corner separation in the rear passage. The efficiency of the upstream rotor was also reduced in small value because the variation of the through flow. After that, the indirect influence of the rotor profiled end wall on the stator and the stage profiling case were also analysed. The optimum stage hub profiling did not equal to the simple combination of the optimum stator and the rotor hub end wall. It is found that in the stage profiling case, the variation of loss in stator and rotor are very well adjusted and balanced by the optimization algorithm. The improvement of efficiency therefore achieved the highest value.