Analysis on stationary window of oblique detonation wave in methane-air mixture

Abstract

In order to obtain the standing conditions and stationary range of oblique detonation wave in methane-air combustible mixture, we use the Newton-Raphson iteration method to solve the perfect gas flow conservation equations of oblique detonation wave based on detonation theory. We investigate the variation laws of the oblique detonation stationary window and internal mechanism under different methane-air equivalence ratio, incoming flow velocity, initial pressure and initial temperature. The oblique detonation polar curve can be separated into three sections, each of which has different flow characteristics corresponding to different wave morphology. Among them, a stationary oblique detonation wave can be formed when the wedge angle is larger than the wedge angle of Chapman-Jouguet state oblique detonation wave, and smaller than the maximum wedge angle corresponding to the oblique detonation wave without detached. The wedge angle range is called the stationary window of the oblique detonation wave. We found that the oblique detonation is more easily formed when the methane-air mixture is under the oxygen-enriched condition, and the range of oblique detonation wave stationary window becomes larger as the incoming velocity increases. The changes of initial pressure and temperature have little influence on the stationary window. The change law of the stationary window of oblique detonation wave corresponds to the change law of Mach number behind CJ oblique detonation wave. In addition, the standing conditions are mainly related to the coupling of the incoming mixture kinetic energy and heat release.