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Meeting	ACGS Committee Meeting 127 - San Diego, CA - November 2021
Agenda Location	8 SUBCOMMITTEE D – DYNAMICS, COMPUTATIONS, AND ANALYSIS 8.3 Control of Scramjet Engines
Title	Control of Scramjet Engines
Presenter	Prof. Maruthi Akella
Affiliation	University of Texas at Austin
Available Downloads*	presentation
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Abstract	Scramjet propulsion is an emerging technology that is expected to play a major role within the next generation of hypersonic vehicles. The dual-mode engine concept allows the engine to act in ramjet mode at supersonic flight Mach numbers and then transition to supersonic combustion mode at hypersonic flight Mach numbers. Unstart is one of the most challenging issues surrounding the practical implementation of scramjet engines. This presentation describes our recent work on data-driven modeling for unstart dynamics (for predictive capabilities), design of real-time state estimation algorithms, and the implementation of closed-loop control of the shock-train within a Mach 2.2 direct-connect dual-mode scramjet facility (AFRL test cell 18) operating on liquid fuel. During experiments, the data-driven model performed moderately well but, at times, a significant offset was observed between the measured and predicted shock locations. A “pseudo-shock” pressure rise metric was identified as a much better proxy for shock-train location, and a new system identification model was developed after the experimental campaign that used this quantity for predicting the shock train location within the isolator. The performance of this new model was assessed through postprocessing and demonstrated a considerable improvement, providing excellent shock-train tracking when compared to the measured location and potentially providing a method of predicting unstart events. Our current work focuses on examining the generalizability of this control scheme to distorted nozzles and the physical processes that dictate shock-train location within the isolator, especially what relationship the boundary layer plays upon the location of the shock train. We expect these expanded explorations to allow the development of higher-fidelity dynamics models, preferably based on physical principles, which will allow accurate and robust prediction of the shock-train location and facilitate their control within flight-like engine configurations.