Effects of employing supplemental oxygen in the ignition process on the initiation of rotating detonations

To simplify the ignition system, a new method named the spark plug ignition with supplemental oxygen has been proposed and validated in this study. The effects of this new ignition method on the initiation process and propagation characteristics of rotating detonations have been experimentally investigated in a hollow chamber by varying the air mass flow rate, the equivalence ratio, and the mass flow rate of supplemental oxygen. The room temperature air and ethylene are utilized as oxidizer and fuel, respectively. The experimental results indicate that rotating detonation waves can be obtained by adopting this new method under different inflow conditions, and the equivalence ratios for the detonation mode range from 0.51 to 1.15. When the equivalence ratio exceeds 0.5, the operating range and initiation time of rotating detonations achieved with this new method are comparable to those obtained with pre-detonation tube ignition. In contrast to the ordinary spark plug ignition, this new ignition method demonstrates superior performance. In addition, when additional supplemental ethylene is supplied, rotating detonations also can be obtained at the equivalence ratio of lower than 0.5 by using this new method. Moreover, increasing the mass flow rate of the supplemental oxygen is helpful for rapid establishment of rotating detonations and meanwhile, improves the success rate of initiating rotating detonations.