Deflagration-to-Detonation Transition in Highly Reactive Combustible Mixtures

Introduction

The mechanism by which a deflagration becomes a detonation (deflagration-todetonation transition, or DDT) still remains one of the most interesting unsolved problems of combustion theory. Understanding of the mechanisms responsible for DDT is important since detonation represents the most severe form of explosive hazard in industrial accidents involving fuel-air explosions. The conclusion drawn from numerous studies which solved two dimensional Navier-Stokes equations using a one-step chemical model with Arrhenius kinetics was that the gradient of induction time (usually related to the temperature gradient), which is involved in the Zel’dovich criterion [1, 2] seems quite plausible as the mechanism of DDT. However, a one-step reaction model cannot reproduce the main properties of the combustion such as the induction time in chain-branching kinetics and detonation initiation. A detailed chemical model for the chain-branching chemistry has a profound effect on the validity of Zeldovich’s spontaneous wave concept and on the mechanism of the DDT. The primary cause for disagreement come not from three dimensional effects in the experiment but from a one-step Arrhenius kinetics which was employed for CFD simulations (see [3] for recent review) and which can not capture the principle features of the phenomena.