Fire Safety Science Digital Archive

Numerical simulations are presented of the spontaneous ignition of a stoichiometric propane-air mixture in a duct containing an obstacle. The simulations were performed by combining a solution of the compressible equations of fluid dynamics with a phenomenological chemical induction model for species conversion and energy release. The mixture ignites as a weak shock wave hits and is reflected from the obstacle. Nonreactive simulations show how the obstacle partially blocks the flow such that one portion of the shock front reflects off of the obstacle and another portion is transmitted. Reactive-flow simulations show spontaneous ignition in the reflected shock region, which quickly transitions to a detonation. Eventually, transition to detonation also occurs in the transmitted shock direction. As the obstacle height is increased, the strength of the transmitted wave is decreased and transition to detonation requires longer time.