Three Dimensional Flow Analysis in a Radial Turbine Rotor. 1st Report. Effect of Tip Clearance to Secondary Flow in Rotor Passage.

Abstract

Three dimensional viscous flow analysis was performed in a radial turbine rotor in which blade-to-blade velocity distribution had been measured by LDV. Calculations were executed both cases and without clearance. Tip clearance area was filled with another computational grid and multi-block analysis code was adopted. The result of calculation was compared with experimental data. Good agreement was found in tendency of velocity distribution. Secondary flow occurring in rotor passage was investigated. At the inlet part of a turbine, passage vortex rotating counter to the rotor was observed. The mechanism of its generation could be explained dividing the vortex into the flows along the wall surfaces. At the exit part of a turbine, two calculations were quite different in the figure of secondary flow. Leakage vortex was growing and moving away from suction surface. It was clear that secondary flow was greatly affected by the flow discharging from leakage vortex. It shouldn't be considered that leakage flow is a local phenomena and can be distinguished from the flow between blades.