Active Control of a Scramjet Engine

ABSTRACT: Scramjet engines are expected to operate across wide Mach number ranges and typically incorporate isolators to provide sufficient back-pressure margin and prevent unstart. Unfortunately, isolators introduce additional weight and drag, and form multiple shockwave/boundary layer interactions, which degrade the incoming flow. As military requirements become increasingly demanding, an active control system is necessary to maintain engine stability and power output. Ahmic Aerospace LLC, in collaboration with The Ohio State University (OSU), proposes to develop and experimentally demonstrate an active control system. OSU has recently demonstrated that a plasma actuator controlled cavity can increase the back-pressure margin of an isolator by 70% while mitigating the associated parasitic drag and tonal pressure fluctuations. This cavity/actuator system will be experimentally optimized. A control algorithm will be designed to detect imminent unstart and signal the appropriate excitation condition to the actuators. Skin friction is an ideal quantity to measure for feedback to the control algorithm. Two direct-measuring skin friction sensors will be developed, one with sufficient response-time (>2 kHz), and another capable of maintaining accurate measurements when subjected to shock-induced pressure gradients. All components will be integrated and tested as a preliminary active control system to demonstrate the feasibility of design.; BENEFIT: The proposed active control system will improve the operational stability and net power output of scramjet engines. The technology would ultimately expand vehicle flight envelopes, increasing range, speed, and payload performance. Primary military applications include various time-critical weapon systems, strike/reconnaissance vehicles, and space launch applications. In addition, the developed technology can be privatized for future hypersonic transport and space access vehicles.