Lagrangian-conditioned statistics of detonation propagation in a realistic rotating detonation engine

Abstract

Flow behavior was investigated in an RDE using Lagrangian Particle Tracking coupled with high-fidelity Eulerian simulations. The case considered utilized the AFRL Radial Air Inlet design under stoichiometric hydrogen–air conditions at a specified mass flow rate, with a single wave observed in the system. Particle properties were recorded throughout the simulation to compare to Eulerian data as well as to examine the effect of particle injection location on resulting flow behavior. The Lagrangian description of the flow closely resembled the Eulerian description in terms of capturing the detonation wave front properly, but axial velocities between the two descriptions varied significantly due to the moving particles increasing the average recorded velocities within the flow. Injection location was examined based on three conditions, namely starting injection locations 5° ahead of the detonation wave, 5° behind, and 180° ahead. Results showed differing behavior in the 180° condition, wherein a pressure rise was seen further axially into the chamber from detonation wave contact. Particle data was also viewed from a thermodynamic cycle standpoint and compared against an ideal detonative process from a reduced-order cycle deck model. Each injection condition studied failed to fully represent the ideal detonative process, despite showing similar overall trends between enthalpy and entropy, with the highest peak enthalpy coming within 23.75% of the ideal enthalpy in the 180° condition. Heat release behavior aided in understanding deflagrative losses incurred in certain injection conditions. An optimal injection location of 26° ahead of the wave was determined based on maximum pressure rise, which also failed to produce fully ideal thermodynamic behavior. Overall, this analysis shows the value of examining RDE flow from a Lagrangian perspective, given the insight it yields into how fluid interacts with flow structures inside complex RDE systems and how this translates to thermodynamic space for comparison to ideal behavior.