Plasma actuator for wake flow control of high camber blades during part load operation

Plasma actuators, composed of two electrodes with a constant or time-varying voltage difference applied between them are known to impart a directed momentum on the gas in the vicinity of one of the electrodes. This work focuses on a plasma actuator installed on one blade of a gas turbine blade cascade. These high-camber angle blades are used for transportation and stationary applications, and at partial load (i.e. low flow speeds) they exhibit flow separation on the suction side. A plasma actuator, optimized in terms of insulation thickness and applied voltage waveform, is placed on the suction-side, near the trailing edge of the blade, and airfoil plasma-off performance compared to plasma-on. Separation is detected via surface pressure measurements, and loss of stagnation pressure via measurements of total pressure with Pitot tubes. Flow directions are measured in a few cases as well. The actuator is found to decrease the stagnation pressure loss at most experimental conditions, and to increase the flow turning angle. Conclusions as to the plasma actuator effectiveness are derived from blade loss coefficients. The plasma actuator can reduce stagnation pressure losses by 50% with the most effective actuator of those investigated thus far in this cascade. An approximate ratio of electrical to dynamic forces is defined and calculated as a means of characterizing the relative magnitude of the plasma force required to avert separation. Since the loss is measured in the wake of the blade, the term "wake filling configuration" seems an appropriate description of this specific actuator location.