2008 Volume 2 Issue 3 Pages 985-996
The unsteady flow field of an axial-flow turbine rotor was investigated experimentally using an LDV system. Detailed measurements of the time-averaged and time-dependent distributions of the velocity, the flow angle, and the turbulence intensity were carried out. The obtained data was analyzed from the viewpoints of both absolute (stationary) frame of reference and relative (rotating) frame of reference. This paper focuses on the effect of the turbine nozzle secondary vortices (passage vortices combined with trailing edge vortices) near the hub endwall on the flow field inside the rotor passage. The nozzle passage vortex are accumulated on the rotor suction surface because of both the negative jet effect of the nozzle passage vortex itself and the formation of the rotor passage vortex. The nozzle passage vortex induces large fluctuations of velocity and turbulence intensity inside the rotor. On the rotor suction surface, the maximum value of the turbulence intensity at the nozzle passage vortex region is as much as 18%.
