Descending Modal Transition Dynamics in a Large Eddy Simulation of a Rotating Detonation Rocket Engine

Rotating detonation rocket engines (RDREs) exhibit various unsteady phenomena, including modal transitions, that significantly affect their operation, performance and stability. The dynamics of the detonation waves are studied during a descending modal transition (DMT) where four co-rotating detonations waves decrease to three in a gaseous methane-oxygen RDRE. Detonation wave tracking is applied to capture, visualize and analyze unsteady, 3D detonation wave dynamics data within the combustion chamber of the RDRE. The mechanism of a descending modal transition is the failure of a detonation wave in the RDRE, and in this study, the failing wave is identified along with its failure time. The regions upstream of each relative detonation show the mixture and flow-field parameters that drive detonation failure. Additionally, it is shown that descending modal transitions encompass multiple phases of detonation decay and recovery with respect to RDREs. The results show high upstream pressure, heat release and temperature, coupled with insufficient propellants, lead to detonation wave failure and non-recovery of the trailing detonation wave during a descending modal transition. Finally, the Wolanski wave stability criterion regarding detonation critical reactant mixing height provides insight into detonation failure or sustainment.

Micro-level modeling of the detonation wave attenuation by inert particles

A computational technology for direct modeling of the detonation waves interaction with a set of particles at the micro level has been developed. A simulation of the detonation waves passage through a system of particles with their different relative positions was carried out. Stoichiometric hydrogen air mixture is considered. The combustion process is described using a reduced kinetic mechanism. Estimates of the ratios between times of the velocity and thermal relaxation are obtained. Detailed shock-wave patterns of gas flow in the particles vicinity are obtained. The possibility of detonation failure at particles volume fractions of close to the concentrations obtained in modeling at the macro level has been revealed.