Auto-ignition effect in gaseous detonation propagation

In this paper, the auto-ignition mechanism in the gaseous detonation propagation of the stoichiometric H₂-air detonable mixture in a straight tube was numerically studied using an overall one-step chemical reaction model and a detailed chemical reaction model based on the two-dimensional Euler equations. Meanwhile, the ignition delay times predicted by different models under different pressures and at different temperatures were compared and the propagation process of triple-shock points and the cell sizes were investigated. The results demonstrated that the cell sizes are proportional to the ignition delay times, and the ignition delay time in the induction zone is consistent with the average movement period of the triple-shock points. The leading shock compresses the detonable gas and then both the temperature and the pressure of the gas rise. The gas with high temperature and pressure soon finishes the process of auto-ignition, and a lot of heat is released during the ignition to maintain the detonation propagation, which means the auto-ignition mechanism ensures the self-sustained detonation propagation. The ignition delay time is considered as a chemical time scale characterizing the chemical reaction. The period of the movement of the triple-shock points is a characteristic time scale of shock dynamics. The coupling of these two time scales is a principal mechanism in gaseous detonation propagation.