Unsteady Flow Interaction Caused by Stator Secondary Vortices in a Turbine Rotor

Abstract

Nonintrusive measurements near and within the rotor of a cold-air turbine showed a sudden increase of turbulence energy when the wake portion of the incoming fluid entered the rotor. It has been suggested that this was due to the cutting of the passage vortices and trailing-edge shed vortices which emerge from the stator row. Since these secondary vortices are located very close to the stator wakes, it was very difficult to distinguish between the effects of shed vortex and passage vortex cutting on turbulence intensification. In the present paper, a method is shown which, with the help of time-distance diagrams, made it possible to attribute the turbulence increase to the breakdown of the secondary vortices. Further, the time-distance diagrams made it possible to locate the origin of the turbulence production and follow the spreading of the highly turbulent flow regions through the rotor channel.