Effects of the Tip Clearance Flow Field on the Secondary Losses

Abstract

In this paper an extension of our secondary flow calculation method is presented in order to estimate the influence of the tip clearance on the secondary flow field. The impact of the tip clearance vortex is embodied in the method so that the secondary vorticity field, based on the complete form of the meridional vorticity transport equation is properly modified. In this way the changes of the secondary flow field quantities are predicted along with the resulting additional losses imposed by the existence of the tip clearance. The estimated tip clearance losses, based on the flow field structure, are compared to results obtained from various semi-empirical loss correlations found in the literature. Several cases encountered in axial flow compressor configurations are investigated and the calculated results are favourably compared to experimental data and results of previous calculations. Additionally, in order to clarify the influence of the tip clearance structure upon the secondary flow field, cases with and without tip clearance are also examined.