Design optimization of a transonic compressor blade with sweep and lean integrated with axial slot casing treatment

Abstract

Two multi-objective optimization designs of the rotor blade for an axial transonic compressor are carried out in this study. Among them, the optimization of the blade alone is called blade-only optimization. The optimization of the blade integrated with axial slot casing treatment (ASCT) is called blade-integrated optimization. During the optimization stage, the values of sweep and lean in the tip region are used as the optimal variables. The stall margin improvement and the efficiency at the design-operating-point are adopted as the optimal objectives. The Radial Basis Function (RBF) approximation is used to construct the surrogate model, and the non-dominated sorting genetic algorithm II (NSGA-II) is selected to search for Pareto fronts. The optimal individuals selected from the Pareto fronts of the two optimizations are compared and analyzed. The coupling effect between the blade and ASCT is studied in this paper to illustrate the advantage of the integrated optimization. The results show that the blade-integrated optimization can optimize the coupling effect, which strengthens the ability of the ASCT to eliminate the blockage while ensuring little efficiency loss at the design point. However, the application of ASCT for the blade-only optimized blade may reduce efficiency and lead to a premature stall, which is caused by the failure to eliminate the negative effect of the coupling. Compared with the blade-only optimized blade, the application of ASCT for the blade-integrated optimized blade increases the stall margin improvement from 10.77% to 14.88%, and increases the efficiency improvement from −0.3% to −0.12%.