Abstract: By deducting the HLLC(Harten, Lax, van Leer, Contact) fluxes of convective terms in the rotating coordinate system, a finite volume analysis code based on multi-block structured grids is developed independently, which aims at realizing the numerical solving of internal flow fields of turbo machineries. The flow simulations of a shrouded backswept impeller and an unshrouded radial impeller are carried out respectively. The calculated data such as surface pressure at various blade heights show favorable agreement with the data from commercial software, which verifies the accuracy of the algorithm. Then the characteristic analysis of tip clearance flow for the radial impeller is carried out. The results obtained indicate that, although the total leakage mass flow rises almost linearly as the impeller diffusion factor increases, the absolute value of leakage mass flow and the leakage loss decrease as the diffusion factor increases. Clearance leakage is driven by the loading near blade tip, and the leakage mechanism shows some similarity within a certain range of rotational speed. Under near choke operation point the generation spot of leakage vortex shifts more downstream, but attenuates faster.

Key words: Radial impeller　Clearance flow　HLLC flux　Numerical simulation　Diffusion factor