Influence of chemical kinetics on detonation initiating by temperature gradients in methane/air
Nordita Astrophysics seminars
Wednesday 31 October 2018
to 14:30 at
Mikhail A. Liberman (Nordita), Chengeng Qian (Beijing), JianNan Liu (Taiyuan)
Different simplified and detailed chemical models and their impact on simulations of combustion regimes initiating by the initial temperature gradient in methane/air mixtures are studied. The limits of the regimes of reaction wave propagation depend upon the spontaneous wave speed and the characteristic velocities of the problem. The present study mainly focus to identify conditions required for the devel- opment a detonation and to compare the difference between simplified chemical models and detailed chemistry. It is shown that a widely used simplified chemical schemes, such as one-step, two-step and Keywords: other simplified models, do not reproduce correctly the ignition process in methane/air mixtures. The ig- Temperature gradient Chemical models nition delay times calculated using simplified models are in orders of magnitude shorter than the ignition Deflagration delay times calculated using detailed chemical models and measured experimentally. This results in con- Detonation siderably different times when the exothermic reaction affects significantly the ignition, evolution, and Explosions coupling of the spontaneous reaction wave and pressure waves. We show that the temperature gradient Ignition capable to trigger detonation calculated using detailed chemical models is much shallower (the size of the hot spot is much larger) than that, predicted by simulations with simplified chemical models. These findings suggest that the scenario leading to the deflagration to detonation transition (DDT) may depend greatly on the chemical model used in simulations and that the Zel’dovich gradient mechanism is not necessary a universal mechanism triggering DDT. The obtained results indicate that the conclusions de- rived from the simulations of DDT with simplified chemical models should be viewed with great caution.
Wang et al. (2018).