Flow combustion characteristics and performance of Al powder-fueled water ramjet engine under different injection schemes

Powder-Fueled Water Ramjet Engine (PFWRE) is the most promising powerplant in underwater high-speed propulsion. However, the effect of powder injection mode on its performance and the mechanism of this effect are not well understood. In this paper, a computational framework for multiphase combustion flow is developed and validated. Further, the effects of different injection schemes on flow combustion characteristics and engine performance are evaluated via simulation. Our findings indicate that the dominant recirculation zone in front of the primary water inlet delivers water vapor to the combustor head, providing the necessary oxidant for the ignition and combustion of Al particles. Changing the injection parameters directly affects the flame zone distribution and the ability of the recirculation zone to deliver water vapor, leading to variations in particle ignition delay. The engine combustion efficiency and specific impulse efficiency exhibit a negative correlation with injection height, peaking before declining with increased injection angle. It is shown that particle mixing degree and particle dispersion degree are closely related to engine performance. Enhanced particle mixing in front of the primary water inlet and particle dispersion behind the secondary water inlet are considered favorable approaches to improve engine performance, which promotes the particle combustion process and improves the heat-work conversion efficiency.