Feedback into Mixture Plenums in Rotating Detonation Engines

TLDR

Rotating detonation engines extend pulse detonation engines to continuous detonation, yet their interaction with the upstream mixture plenum remains poorly understood and critical for stability and performance. This study extends validated RDE models to investigate how pressure feedback into the mixture plenum, across two‑ and three‑dimensional simulations, varies with three injector configurations. The authors performed 2‑D and 3‑D simulations of RDEs using established models, systematically varying injector throat‑to‑face area ratios (0.2 and 0.4) to assess stability, performance, and pressure feedback. Results show that for an area ratio of 0.2 the RDE performance is nearly ideal, while a ratio of 0.4 reduces specific impulse by 2.4–11.4 % and causes large pressure feedback (up to 3.83 atm), with cylindrical micro‑injectors exhibiting the worst unsteady flow and stability at extreme pressures.

Abstract

Rotating detonation engines (RDE’s) represent a natural extension of the pulse detonation engine (PDE) concept to a continuous detonation for obtaining propulsion and power from the high efficiency detonation cycle. Although extensively studied for the last few years, RDE’s are still less understood and developed than the PDE concept. In particular, interaction between the detonation wave in the combustion chamber and the upstream mixture plenum is critical to the stability and performance of an RDE, and has not been studied in detail. In this paper, we extend our well-tested RDE models to examine the effect of pressure feedback into the mixture plenum with two and three-dimensional simulations. We examine three main injector configurations to determine their effect on stability, performance, and feedback into the mixture plenum. Results indicate that although the flow-field is considerably different, the performance of the RDE with all three modeled injection systems is close to that of assuming an ideal injection process, especially for a injector throat to injector face area ratio of 0.2. For an area ratio of 0.4, the drop in performance is more noticable, varying between 2.4% at 10 atm plenum pressure to 11.4% at 4 atm. Specific impulses for all the modeled injector cases varied from 3975 s to 5263 s. The stability at high and low pressures becomes much more of an issue when modeling specific injectors, due to an increase in flow unsteadiness from the injection. Pressure feedback into the mixture plenum appears to be relatively low for area ratios of 0.2 (less than 10% of stagnation pressure), but becomes very large for even moderate area ratios of 0.4. The cylindrical micro-injectors had the worst pressure feedback, with underpressures between 1 and 1.77 atm and overpressures between 3.09 and 3.83 atm with the large area ratio.