Effects of disturbance on detonation initiation in H2/O2/N2 mixture

Abstract

Detonation initiation has been extensively investigated in the past several decades. In the literature, there are many studies on detonation initiation using a large amount of blast energy and obstacles to respectively achieve direct detonation initiation or deflagration to detonation transition (DDT). However, there are few studies on detonation initiation with a non-uniform initiation zone. In this work, two-dimensional numerical simulations considering detailed chemistry and transport are conducted to investigate the effects of disturbance on detonation initiation in a stoichiometric H2/O2/N2 mixture. The high-pressure and high-temperature detonation initiation regime is imposed by a sinusoidal disturbance. Introduction of such disturbance is found to promote the onset of detonation and to reduce time and distance for detonation formation. This is mainly because such disturbance can induce shock wave interaction, which generates transverse waves. The reflected transverse waves result in local autoignition/explosion. The coherent coupling between local autoignition and pressure wave resulting from a large amount of heat release eventually leads to the detonation development. It is found that the distance and duration for detonation initiation become shorter when a disturbance with smaller wavelength or larger amplitude is enforced. When the ratio between the wavelength and amplitude of disturbance is fixed, the change in wavelength and amplitude has little influence on detonation initiation. Therefore, disturbance with either small wavelength or large amplitude can be used to promote detonation initiation.