Computational Examination of Converging Geometries in RDRE Nozzles

Prior studies have shown that nozzle geometry can affect wave dynamics within rotating detonation rocket engines, but details of that relationship are still not well understood. In this study, we investigate how changes to the subsonic section of a converging-diverging nozzle affects engine operation. Three-dimensional reacting large eddy simulations are presented for three chamber geometries: one without a nozzle; one with a nozzle that incorporates a convex subsonic converging section; and one with a concave converging section and the same constricted area ratio. This change in nozzle geometry had minimal effect on engine dynamics for the conducted simulations, resulting in the same number of waves for both nozzle geometries, and wave speeds that matched to within 1%. However, the convex geometry operated with a 4 % higher specific impulse. A methodology is proposed for using enthalpy of formation to compare the energy released due to combustion. Results show that the choice of converging section does change overall performance in a rotating detonation engine even when combustive energy release is unchanged, a demonstration that traditional nozzle design considerations, such as pressure loss, are still important in the design of detonation engines.