Cell Width and ZND Calculations

The ZND (Zeldovich - von Neumann - Döring) model of a detonation wave decomposes the one-dimensional steady wave into a non-reactive thin shock followed by an exothermic reaction zone [Zeldovich (1950)] that terminates at the CJ state. The reaction zone typically consists of an induction zone where non-exothermic dissociation reactions cause radical species to accumulate, followed by a thin recombination zone where the reaction runs to completion and heat is released. The thickness of the reaction zone is determined by the reaction rates, primarily in the induction zone.

Numerically, the shock speed is computed from the Chapman-Jouguet model and equilibrium thermochemistry. The frozen postshock state is the initial condition for a marching solution of a system of ordinary differential equations for the thermal and chemical state. The distance from the shock to the point of maximum heat release normally defines the reaction zone thickness, analogously to the constant volume induction time. In fact, reaction zone thicknesses have been estimated using a constant volume approximation [Westbrook (1982)]. Other definitions based on Mach number can be used, and the different definitions provide information about the shape of the reaction zone [Shepherd (1986)].

Reaction zone thicknesses (vs percent mixture in air) computed by ZND analysis for mixtures 1-26 of [Ross and Shepherd (1996)] (see Table ) and two additional mixtures are presented in Figs. - in Appendix . Fig.  shows reaction zone thicknesses for mixtures 12-17 from Table 1. These calculations were performed with the modified reaction mechanism of [Miller and Bowman (1989)].