Mainstream aerodynamic effects due to wheelspace coolant injection in a high-pressure turbine stage: Part II - Aerodynamic measurements in the rotational frame

The current paper deals with the aerodynamic measurements in the rotational frame of reference of the Axial Flow Turbine Research Facility (AFTRF) at the Pennsylvania State University. Stationary frame measurements of "Mainst ream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High Pres sure Turbine Stage" were presented in Part 1 of this paper The relative aer odynamic effects associated with rotor-nozzle guide vane (NGV) gap coolant injections were investigated in the rotating frame. Three-dimensional veloc ity vectors including exit flow angles were measured at the rotor exit. Thi s study quantifies the secondary effects of the coolant injection on the ae rodynamic and performance character of the stage main stream flow for root injection, radial cooling, and impingement cooling. Current measurements sh ow that even a small quantity (1 percent) of cooling air can have significa nt effects on the performance and exit conditions of the high-pressure turb ine stage. Parameters such as the total pressure coefficient, wake width, a nd three-dimensional velocity field show significant local changes. It is c lear that the cooling air disturbs the inlet end-wall boundary layer to the rotor and modifies secondary flow development thereby resulting in large c hanges in turbine exit conditions. Effects are the strongest from the hub t o midspan. Negligible effect of the cooling flow can be seen in the tip reg ion.