化学动力学对甲烷/空气温度梯度起爆的影响
Influence of chemical kinetics on detonation initiating by temperature gradients in methane/air
摘要：
不同的简化和详细的化学模型和它们的影响，在甲烷/空气混合物的初始温度梯度引发的燃烧制度的模拟进行了研究。反应波传播的限制取决于自发波的速度和问题的特征速度。本研究主要集中于确定发展爆轰所需的条件，并比较简化化学模型和详细化学模型之间的差异。结果表明，广泛使用的简化化学方案，如一步，两步和其他简化模型，不能正确地再现甲烷/空气混合物的着火过程。使用简化模型计算的点火延迟时间比使用详细的化学模型计算和实验测量的点火延迟时间短几个数量级。当放热反应显著影响自发反应波和压力波的点火、演化和耦合时，这导致相当不同的时间。我们表明，能够触发爆震使用详细的化学模型计算的温度梯度是浅得多（热点的大小要大得多）比，通过模拟与简化的化学模型预测。这些研究结果表明，导致爆燃转爆轰（DDT）的情况下，可能在很大程度上取决于模拟中使用的化学模型，Zeldovich梯度机制是不一定是一个通用的机制触发DDT。结果表明，用简化的化学模型模拟DDT所得出的结论应持谨慎态度。
英文摘要：
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 development 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 other simplified models, do not reproduce correctly the ignition process in methane/air mixtures. The ignition delay times calculated using simplified models are in orders of magnitude shorter than the ignition delay times calculated using detailed chemical models and measured experimentally. This results in considerably different times when the exothermic reaction affects significantly the ignition, evolution, and coupling of the spontaneous reaction wave and pressure waves. We show that the temperature gradient 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 Zeldovich gradient mechanism is not necessary a universal mechanism triggering DDT. The obtained results indicate that the conclusions derived from the simulations of DDT with simplified chemical models should be viewed with great caution.
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