Experimental study on the aerodynamic influence of purge flow in a turbine cascade with different mainstream incidence angles

Demand for high reliability and long life of modern turbine requires that turbine components should be cooled adequately. The cooling flow purged into the rotor-stator disk cavity will inevitably interact with the mainstream. The current paper mainly focuses on the aerodynamic influence of cooling flow on the secondary flows in the mainstream. Both particle image velocimetry and blade wall pressure measurement were utilized to study the flow field within the turbine blade passage under different mainstream incidence angles and purge flow rates. The purge flow was found to promote the development of the passage vortex by inducing vortices which can enhance the vorticity of the passage vortex. In addition, the mainstream incidence angle also has an impact on the development of the passage vortex through affecting the blade loading and the horseshoe vortex. Furthermore, the transient results demonstrate that the time-averaged vortex is the superposition of large number of transient vortices, and the purge flow causes more transient vortices with large size and high strength.