Shock Propagation Through a Square Injector, a Methodology to Investigate RDE Injector Dynamics

The rotating-detonation engine is perhaps the most promising means to realize pressure-gain combustion in modern engines. The physical processes underpinning the dynamics of the combustion wave are complex, and a lack of understanding of these processes represents a significant barrier to practical implementation of the technology. While the propagation of the detonation wave in the azimuth is pseudo-steady in time when the observer is fixed to the motion of the wave, the interaction of the wave with the fuel and reactant injectors is highly unsteady. This interaction directly relates to the performance of the engine, as the pressure rise behind the detonation wave alters the pressure differential across the injector, and thus the flow of reactant into the detonation annulus. This variation in flowrate can result in instability of the detonation waves in the annulus, and consequently in the power output and efficiency of the engine. Between the complexity of the geometry, the unsteadiness of the flow, and the intrinsic challenge of studying shock-driven combustion, the details of this interaction remain relatively obscure. As a first step towards understanding the injector-wave interaction, a significant simplification of the problem is considered through an abstracted experimental setup. The detonation wave is replaced with a non-reacting shock generated by a shock tube, and the annulus is unwrapped into a single linear channel. Both simplifications make direct visualization of the problem via schlieren imaging tractable. The experimental work is then used primarily as a validation for computational fluid dynamics simulations of the simplified problem; simulations that permit the extraction of quantitative data that can be used to characterize the time-varying performance of the injector.