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arXiv · 1810.10311

Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures

Mikhail Liberman·Cheng Wang·Chengeng Qian·JianNan Liu
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Abstract

Understanding the mechanisms of explosions is important for minimizing devastating hazards. Due to the complexity of real chemistry, a single-step reaction mechanism is usually used for theoretical and numerical studies. The purpose of this study is to look more deeply into the influence of chemistry on detonation initiated by a spontaneous wave. Results of high resolution simulations performed for one-step models are compared with simulations for detailed chemical models for highly reactive and low reactive mixtures. The calculated induction times for H2/air and for CH4/air are validated against experimental measurements for a wide range of temperatures and pressures. It is found that the requirements in terms of temperature and size of the hot spots, which produce a spontaneous wave capable to initiate detonation, are quantitatively and qualitatively different for one-step models compared to the detailed chemical models. The impact of detailed chemical model is particularly pronounced for the methane-air mixture. In this case, not only the hot spot size is much greater than that predicted by a one-step model, but even at elevated pressure the initiation of detonation by a temperature gradient is possible only if the temperature outside the gradient is so high, that can ignite thermal explosion. The obtained results suggest that the one-step models do not reproduce correctly the transient and ignition processes, so that interpretation of the simulations performed using a one-step model for understanding mechanisms of flame acceleration, DDT and the origin of explosions must be considered with great caution.

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Mikhail Liberman, Cheng Wang, Chengeng Qian, JianNan Liu. 2018-08-21. Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures. https://doi.org/10.1080/13647830.2018.1551578

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