Effects of Dilution and Pressure on Detonation Propagation Across an Inert Layer

In explosion accidents, inert layer(s) can be used to dampen or suppress detonation propagation. In detonation engines, the detonation may propagate in an inhomogeneous mixture with inert layer(s). Here, the detonation propagation in hydrogen/oxygen/nitrogen mixtures with a single inert layer normal to the detonation propagation direction was investigated. Six hydrogen/oxygen/nitrogen mixtures with different amounts of nitrogen dilution and at different initial pressures were considered. The emphasis was placed on assessing the effects of nitrogen dilution and pressure on detonation across an inert layer. It was found that successful detonation reinitiation occurs only when the inert layer thickness is below some critical value. The detonation reinitiation process was analyzed. The interactions of transverse waves, the reactive–inert layer interface, and instabilities jointly induced local autoignition/explosions and detonation reinitiation. Counterintuitively, it was found that a thicker inert layer is required to quench a weaker detonation (with more nitrogen dilution or with lower-energy density at lower pressure). With the increase of nitrogen dilution or the decrease of initial pressure, the induction length and cell size of the detonation became larger, which unexpectedly resulted in the larger critical inert layer thickness.