Effects of air injection throat width on a non-premixed rotating detonation engine

Rotating detonation engines are widely studied because of their compact configurations and high thermal cycle efficiency. For simplification, most of the numerical simulations of rotating detonation engines used premixed reactant mixtures. The rotating detonation waves under non-premixed conditions are not studied enough. The width of air injection throat is an important design parameter for a non-premixed rotating detonation engine. Here, a series of three-dimensional numerical simulations of a non-premixed rotating detonation engine with different air injection throat widths are performed. Cases with three different throat widths of 0.4 mm, 1.0 mm and 2.0 mm are calculated. The transient explicit density-based solver in ANSYS Fluent is used to perform the simulations. Detonation combustion happens in different radial domains for different air injection throat widths. When the air injection throat width is 1.0 mm, there is only one rotating detonation wave in the combustion chamber when the total mass flow rate is 272.3 g/s or 500 g/s. When the total mass flow rate is further increased to 1000 g/s, there are two co-rotating detonation waves in the combustion chamber. While for air injection throat width 0.4 mm, the transition to two-wave mode happens at a smaller total mass flow rate of 500 g/s. When the air injection throat width is too large, the interaction between the injection process and the propagating of rotating detonation wave becomes very strong, and the detonation wave quenches due to the insufficient injected reactants. The engine requires a larger total mass flow rate to sustain the continuous propagation of the rotating detonation wave.