Self-excited wave stabilization in a linear detonation combustor

Detonative combustors, such as rotating detonation engines, have increasingly been viewed as next-generation propulsion and power generation systems because they offer higher theoretical thermal efficiencies than conventional constant-pressure combustors. In order for these systems to be realized in a practical context, the impacts of inflow and outlet conditions, reactant mixing, and interactions between counter-propagating waves must be better understood. To examine these phenomena in a simplified geometry, the present work considers a methane-oxygen reflective shuttling detonation combustor with an open-closed chamber configuration. High-fidelity simulations are conducted for two equivalence ratio conditions (lean and rich), and comparisons are made to complementary experiments. The results show that self-sustained steady-state wave behavior consists of minimally-reacting left-running waves and right-running detonation waves. The lean case is found to establish steady-state operation after a shorter time and exhibit detonation waves after a shorter distance from the closed end of the chamber. The simulations are able to predict the experimentally observed trends in the wave velocity in the direction of propagation. Wave-relative averaged flow fields show considerable reactant stratification and parasitic combustion ahead of the waves, likely contributing to their low speeds and pressures relative to ideal detonations. Conditional statistics ahead and behind the waves indicate that peaks in heat release occur at both lean and rich conditions near the open end of the chamber, and incomplete fuel oxidation in the primary detonation waves leads to delayed oxygen consumption and higher temperatures downstream.