Characterization of Combustion Powered Actuators for Flow Control

The performance of a high-power small-scale combustion-based fluidic actuator for flow control applications is characterized with specific focus on increased operating frequencies. Momentary (pulsed) actuation jets are produced by the ignition of a mixture of gaseous fuel and oxidizer within a small (cubic centimeter scale) combustion chamber. The combustion process yields a high pressure burst (1 to 3 ms in duration in the typical configurations) and the ejection of a high-speed exhaust jet. The actuation frequency can be continuously varied by independently controlling the flow rate of the fuel/oxidizer and the spark ignition frequency up to a maximum determined by the operating characteristics of the actuator. The effects of variation in mixture ratio, orifice diameter, mixture flow rate, and actuation frequency on the characteristic time scales are investigated. Results for operation of the device in both premixed and nonpremixed modes are discussed, with nonpremixed operation typically yielding higher pressures in the present configurations. Operating frequencies up to 500 Hz are demonstrated for nonpremixed operation. The actuator performance is characterized by both its peak thrust and net total impulse, with increases in peak jet momentum often two to three orders of magnitude above the baseline steady jet.