Models for shock-induced ignition evaluated by detailed chemical kinetics in the context of deflagration-to-detonation transition
2016
会议
Eleventh International Symposium on Hazard, Prevention, and Mitigation of Industrial Explosions
Deflagration-to-detonation transition is possible in industrial explosion accidents involving highly reactive gas mixtures such as H2/air. Obstructions inside an explosion volume support strong flame acceleration and the transition to detonation. Various mechanisms are known to play a role during onset of detonation, including mixing processes and instabilities or shock-induced ignition. This paper focuses on shock-induced ignition, which is relevant in obstructed geometries. Laboratory-scale experiments in a closed rectangular channel with H2/air mixtures were conducted using high-speed color schlieren visualization. The observed detonation onset mechanism is comparable to the strong shock-induced ignition phenomenon known from shock tube studies. Models for the determination of the extended second explosion limit and for strong ignition proposed by Lewis and von Elbe (1942, 2012), Shepherd (1986, 2009), Meyer and Oppenheim (1971) and Thomas et al. (2002) are evaluated using a state-of-the-art detailed chemical kinetic scheme. While the first two models agree well, Meyer and Oppenheim’s model deviates significantly at high pressures. Thomas’ model provides a prediction of crit- ical obstacle height for the onset of detonation. At low pressure and laboratory scale, the obstacle height likely controls the ignition mode. At high pressure, even millimeter size obstacles allow for onset of detonation. Experimental validation data on ignition modes at high pressure and large scale, relevant for industrial explosions, is not available.
