High-Speed Experiments on Combustion-Powered Actuation for Dynamic Stall Suppression

Abstract

This work documents high-speed wind-tunnel experiments conducted on a pitching airfoil equipped with an array of combustion-powered actuators. The main objective of these experiments was to demonstrate the stall-suppression capability of combustion-powered actuators on a high-lift rotorcraft airfoil (the VR-12) at relevant Mach numbers. Through unsteady pressure measurements at the airfoil surface, it was shown that combustion-powered actuators could positively affect the stall behavior of the VR-12 at Mach numbers up to 0.4. Static airfoil results demonstrated 25 and 50% increases in poststall lift at Mach numbers of 0.4 and 0.3, respectively. Deep dynamic stall results showed cycle-averaged lift coefficient increases up to 11% at Mach 0.4. Furthermore, it was shown that these benefits could be achieved with relatively few pulses during the downstroke and with no need to preanticipate the stall event. The flow mechanisms responsible for stall suppression were investigated using particle image velocimetry. The flow structures found at these Mach numbers appeared to be very similar to the flow structures noted previously at very low Mach numbers.