Engine performance analysis for mode transition conditions in Rotating Detonation Engines using detailed numerical simulations*

Mode Transition (MT) is a phenomenon of abrupt change in the number of detonation waves, occurring in a Rotating Detonation Engine (RDE), and is due to a change in inlet conditions, such as plenum pressure, fuel reactivity or mass flow rate. MT can result in sudden changes in engine performance$^{\mathrm{1}}$ or detonation failure. In this work, we report results from numerical simulations on the effect of MT on three, key engine performance parameters -- thrust, specific impulse and mass flow rate. The working fuel was stoichiometric H$_{\mathrm{2}}$-O$_{\mathrm{2}}$ mixture, while the N$_{\mathrm{2}}$ dilution was varied to trigger MT. Sensitivity of the new mode configuration on the N$_{\mathrm{2}}$ perturbation trajectory was also examined. It was observed that the engine thrust showed little variation with the change in N$_{\mathrm{2}}$ dilution. All the simulations were performed on a 2D unrolled RDE geometry with discrete nozzle injectors. The compressible Euler equations were solved using the FLASH$^{\mathrm{2}}$ code, with a Piecewise Parabolic Method on a cartesian mesh. $^{\mathrm{1}}$A. George et al., Proc. Comb. Inst., 36 (2), 2691, (2017). $^{\mathrm{2}}$B. Fryxell et al., Astrophys. J., Suppl. Ser. 131, 273 (2000).