Investigations on the initiation characteristics of radical-assisted oblique detonation waves generated by plasma discharges

Abstract

The oblique detonation engine (ODE) faces issues such as no-ignition, difficulty in combustion, and unstable combustion, some proactive auxiliary ignition measures should be implemented. This paper explores the application of radical-assisted combustion technology in the ODE and studies the effects of radicals on the oblique detonation wave (ODW) initiation characteristics. The two-dimensional Navier-Stokes equations which take into account the elementary reaction of acetylene/ethylene-air mixtures are solved, including chain reaction initiation, branching, and termination. The results demonstrate that the addition of radicals yields significant improvements in accelerating the initiation of ODW. The introduction of H, O, or OH radicals decrease the characteristic length of the induction zone with the mole fraction increases. Conversely, the inclusion of CHO radicals leads to an increase in the characteristic length of the induction zone with increasing mole fraction, primarily due to dominant chemical reaction kinetic effects. Additionally, the paper conducts an ignition sensitivity analysis of the radicals on the chemical reaction mechanisms and their influence on the initiation characteristics. Finally, a comprehensive analysis is performed by comparing the numerical results with the constant volume combustion theory, focusing on two initiation patterns: wave-controlled and chemical kinetics-controlled configurations. It is observed that varying the particle parameters results in changing the boundary lines between these two initiation patterns, and increasing the mole fraction shifts the initiation pattern from wave-controlled to chemical kinetics-controlled.