Measurements of Secondary Flows in a Turbine Cascade at Off-Design Incidence

Abstract

The present study is part of an on-going project concerned with the effects of off-design incidence on losses. Previous work has examined the profile losses (Benner et al., 1995). This study focusses on the secondary flow, the endwall flow in the absence of tip clearance. This paper describes an experimental study in a large-scale, low-speed, linear turbine cascade for which the incidence was varied. Three different values of incidence were investigated: 0, +10 and +20 degrees. Detailed flow field measurements were made upstream and downstream of the cascade and static pressure distributions were measured on the blade surfaces. The data were supplemented by extensive surface oil flow visualization. This paper concentrates on the physical insights into the relationship between the behaviour of secondary flows and incidence which have been gained from the measurements and the flow visualization. A preliminary discussion of the effect of incidence on the losses is also included.