Engineering Acoustics/Detonations

Detonation wave structure
Assuming a one dimensional steady flow, the Zel’dovich, von Neumann and Doring (ZND) model is an idealized representation of the detonation wave. The model essentially describes the detonation wave as a leading shock followed by chemical reactions. The leading shock adiabatically compresses the reactants, increasing the temperature, pressure and density across the shock. An induction zone is followed where the reactants are dissociated into radicals and free radicals are generated. The induction zone is thermally neutral in the sense that the thermodynamic properties remain relatively constant. When enough active free radicals are produced, a cascade of reactions occurs to convert the reactants into products. Chemical energy is released resulting in a rise in temperature and a drop in pressure and density. The decrease in pressure in the reaction zone is further decreased by expansion waves and creates a forward thrust that will support the leading shock front. In other words, the proposed propagation mechanism of a detonation wave is autoignition by the leading shock which is supported by the thrust provided by the expansion of the products.