The effect of end wall boundary layer on matching and corresponding flow control technique for multistage axial compressor

Abstract

The development pattern of the end wall boundary layer (BL) in whole conditions and its effect on the matching of multistage compressor have been studied in detail in this paper. Moreover, one method of end wall zone blade modification is carried out, using computational fluid dynamics, to improve the stage matching by re-camber. It is found that the pitch-averaged thickness of end wall BL gradually increases along streamline direction and the BL is highly skewed in the pitchwise direction. In addition, the value of BL thickness, mainly depends on the stage pressure rise coefficient [Formula: see text]. For a fixed rotating speed, the axial BL displacement thickness is changed dramatically from choked condition to near surge operating point. However, this thickness shows insensitive to the change of rotating speeds. On the other hand, BL degrades the pressure-rise characteristics of stages with low efficiency, and it results in mismatching of the compressor stage. Furthermore, the deviation angle of the blades is strongly affected by the end wall BL. Finally, two rows of stators are re-cambered on the leading edge to improve the matching near the hub region where it is influenced by end wall BL. The results show that the total pressure loss coefficient of the stators is reduced by 0.6 points and 1.73 points each. Moreover, the overall isentropic efficiency of multistage compressor is enhanced by 0.39 points without compromising pressure-rise capability and surge margin.