Airfoil separation control with plasma actuators.

摘要

Separation flow control using single dielectric barrier discharge, or plasma actuators, was investigated at low Reynolds numbers on a La203a airfoil. A combination of two actuators placed on the airfoil was used to investigated the impact of placement for single actuators and aggregate flow control impact using both actuators simultaneously. One actuator was placed near the airfoil's leading edge while the other was placed near x/c = 0:4.;Prior to the wind tunnel study, bench-top testing was performed on three dielectric materials to determine the impact of dielectric on control authority; these materials were Teflon, acrylic, and alumina. The following parameters were tested to determine effect on jet velocity: plasma frequency, modulation frequency, and voltage input. The plasma frequency was varied from 3,000 to 15,000 Hz, under constant activation with a duty cycle of 100%. The modulation frequency was then tested over a range from 5 to 1,000 Hz with a semi-logarithmic step while operating at a duty cycle of 50%. Alumina produced the highest plasma jet velocity and momentum input but was too brittle and inflexible to be applied to the surface of the airfoil. Teflon provided a reasonable trade off between the flexibility required and a relatively high peak plasma jet velocity and momentum coefficient.;Wind tunnel testing was performed to demonstrate the ability of plasma actuators to control separation over an airfoil in deep stall. The actuators were tested in a variety of configurations including activating the leading edge actuator alone, the aft actuator alone, and both actuators simultaneously. Each configuration was tested across a range of Reynolds numbers from 50,000 to 150,000 with both steady and pulsed activation. The steady activation was performed while holding duty cycle at 100% while the pulsed cases had a duty cycle of 50%. For the pulsed configurations a range of reduced frequencies was examined from 0.1 to 10. It was observed that the lower reduced frequencies exhibited a stronger control. Control authority was demonstrated with Reynolds numbers up to a Reynolds number of 150,000. The leading edge actuator performed best in both constant and pulsed activation, while the aft actuator performed best when operated in conjunction with the leading edge actuator to maintain control authority across the entire suction surface.