Behavior of Combustion Wave Induced by Propagation of Shock Wave into Premixed Gas of Hydrogen and Oxygen

Experiments were conducted in order to investigate a behavior of comcustion wave when a shock wave was propagated into a combustible premixed gas of hydrogen and oxygen. A phenomenon occurring in the premixed gas can be classified into four types, i.e. (a) the shock wave just transmitted into the gas without causing ignition for the shock wave of low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave of high-Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a hydrogen-oxygen premixed gas varied with an equivalence ratio φ, initial pressure p1 and Mach number of the shock wave Msi. As a result, the phenomena observed in the gas was classified using a cell-size λ for steady detonation wave, since the cell-size was inversely proportional to a chemical reaction rate of the gas. For the case of sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. An empirical equation to evaluate a pressure was obtained, which is a threshold pressure to ignite the gas behind incident shock wave.