The influence of the heat capacity and diluent on detonation structure

In this article, we investigate the validity of certain common simplifications in the chemical and thermophysical models used as input to multidimensional detonation simulations, derive a more accurate model, and apply the model in two-dimensional studies of the structure detonations in hydrogenoxygen mixtures diluted with argon and nitrogen. In a series of one-dimensional calculations, we examine the effects of (1) approximation of the temperature dependence of the ratio of specific heat, γ, (2) varying the amount and rate of heat release, and (3) varying the chemical induction time, and we compare all of these approximations with a computation that uses a detailed model of the chemical kinetics and correct thermophysics. From these, we derive a simple form for the temperature dependence of γ and show that this gives good results in comparison to the predictions of the detailed calculation for the detonation velocity and the thickness of the induction zone. In a series of two-dimensional calculations, we investigate the effects of using the more accurate simplified chemical models and varying the type of diluent while maintaining the same dilutions. In agreement with experiments, the mixture of hydrogen, oxygen, and argon mixture shows regular detonation structures and clearly formed detonation cells, whereas the mixture of hydrogen, oxygen, and nitrogen shows highly irregular cellular structure.