Separation control using plasma actuators: 2-D and edge effects in steady flow in low pressure turbines

A Dielectric Barrier Discharge plasma actuator is operated in quiescent air and in flow over a Low Pressure Turbine (LPT) airfoil at a Reynolds number of 50,000 (based on exit velocity and suction surface length) and inlet free-stream turbulence intensity of 2.5%. Measurements of velocity and total pressure are taken with constant and intermittent operation of the actuator to study the effects of excitation frequency and amplitude on flow velocity, and the effects of the intermittent signal parameters on separation control. LPT measurements are also taken with opposite and aligned actuator orientations, and downstream of the span-wise plasma discharge edge. The objectives of this paper are: a) to investigate the authority of the plasma actuator for control of bypass transition and separation of low Reynolds number flows in LPT airfoil geometries, b) to comment on the relationship between separation control and frequency of disturbance, and c) to examine the role of three-dimensional vortical disturbances on separation control. Control is demonstrated with the actuator imparting momentum opposite to the flow direction, showing that it is possible to use disturbances alone to destabilize the flow and effect transition. No frequencies of strong influence are found over the range tested, indicating that a broad band of effective frequencies exists. Edge effects are found to considerably enhance separation control.