Wave Mode Dynamics in an Ethylene-Air Rotating Detonation Combustor

This experimental study focuses on investigating the wave mode dynamics in an ethylene-air rotating detonation combustor. The experiments were conducted at various equivalence ratios from similar to 0.7 to similar to 1.7 and at three testing mass flow rates of similar to 0.152, similar to 0.195, and similar to 0.238kg/s. Fast-response wall pressure measurements, high-speed gas luminosity imaging, and heat flux measurements were employed simultaneously to evaluate the dynamics of the detonation waves among various testing conditions. Wave mode transition from two pairs of counter-rotating waves at fuel lean conditions to a single dominant wave at fuel-rich conditions has been observed. Four different wave modes in this transition are identified and discussed in the views of the wave dynamics, the pressure rise magnitude, and the thermal effect. Spectral analyses on the combustor pressure and the flame intensity present good consistency, showing the dynamics of the multiple detonation wave components from two different measuring techniques. The results suggest multiple wave components (namely, a single wave component, a primary wave pair, and a secondary wave pair) can coexist in the current rotating detonation combustor. The wave dynamics at different equivalence ratios follow the tendency of the wave evolution at ideal Chapman-Jouguet conditions. The wave mode transition is found to be a fact of the change of the dominant wave component in the combustor. The sudden growth of the single wave component is observed in the wave mode transition, which greatly changes the combustor environment. The wave mode is inferred to be correlated to the fuel-oxidant mixing configuration, suggesting the fuel-oxidant blowing ratio and the combustor geometry could be significant parameters in the formation of the wave mode.