Blade-Mounted Single Dielectric Barrier Discharge Plasma Actuators in Turbine Cascade

摘要

An experiment was conducted in a linear cascade of Pratt and Whitney Pack-B turbine blades to simulate the flow in the tip-gap region of a low-pressure turbine blade row. The objective was to investigate the sensitivity of the tip-clearance flow to blade-mounted plasma actuators designed to improve the net pressure loss coefficient. Investigations were performed at inlet Reynolds numbers of 0.2 x 106 and 0.5 x 106, corresponding to inlet Mach numbers of 0.08 and 0.2 and exit Mach numbers of 0.13 and 0.3, respectively. The gap-to-chord ratio was 4%. The flow was documented using endwall static pressure measurements and downstream pressure measurements using a five-hole pitot probe. The plasma actuators were operated to excite periodic disturbances that could couple with instabilities associated with the separated shear lay er or bulk flow jetting from under the blade-wall gap. At the lower Reynolds number, the unsteady excitation resulted in as much as a 15% increase in mass-averaged total pressure loss. However, at the higher Reynolds number, the opposite occurred with a maximum of a 12.6% decrease in the total pressure loss. Both occurred at an actuator disturbance frequency that suggested that the actuator excited an instability of the shear layer between the tip-clearance flow and the passage flow.