Mechanisms of strong pressure wave generation in end-gas autoignition during knocking combustion
Mechanisms of strong pressure wave generation in end-gas autoignition during knocking combustion
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DOI：
10.1016/j.combustflame.2014.12.013
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发表时间：
2015-05
影响因子：
4.4
通讯作者：
H. Terashima;M. Koshi
中科院分区：
文献类型：
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作者：
H. Terashima;M. Koshi
采用直接数值模拟的方法模拟了一维定容反应器中爆震燃烧过程，其中直接有效地引入了正丁烷（113种组分）和正庚烷（373种组分）两种预混气体的大量详细化学动力学机理。阐明了尾气自燃过程中强压力波产生的详细机理。正丁烷和正庚烷的比较表明，负温度系数（NTC）区的存在不仅显著影响爆震发生的时刻，而且还影响压力振荡的幅度。在绝热壁条件下，正庚烷的爆震强度在450 ~ 1000 K之间有一个较大的峰值，而正丁烷没有峰值。在650 K附近产生的峰值归因于通过在末端气体中传播而增强的压力波，该压力波在NTC区域的影响下在壁附近局部产生。还发现，有一个过渡的自燃位置在端部气体区域从壁为较高的初始温度的火焰前锋的区域之前，为较低的初始温度，导致不同的机制的爆震强度的产生。在等温壁条件的情况下，650 K附近的峰值由于在壁处缺乏局部温度升高而减小，表明壁温度条件对爆震强度的影响。
A knocking combustion modeled using a one-dimensional constant volume reactor is simulated in a manner of direct numerical simulations, in which large detailed chemical kinetic mechanisms for two premixed gases,n-butane (113 species) andn-heptane (373 species), are directly and efficiently introduced. Detailed mechanisms of strong pressure wave generation during end-gas autoignition are clarified. Comparison ofn-butane andn-heptane shows that the presence of the negative temperature coefficient (NTC) region significantly influences not only the timing of knocking occurrence but also the amplitude of pressure oscillations. In the case ofn-heptane with the condition of an adiabatic wall, there is one large peak produced in the strength of knocking intensity for initial temperature between 450 and 1000 K, whereas there is no peak produced in the case ofn-butane. The peak generated around 650 K is attributed to a pressure wave intensified through propagation in the end-gas, which is locally generated near the wall with the influence of the NTC region. It is also found that there is a transition of the autoignition position in the end-gas region from the wall for higher initial temperatures to the region ahead of the flame front for lower initial temperatures, leading to different mechanisms of knocking intensity generation. In the case of the isothermal wall condition, the peak around 650 K is reduced due to the lack of a local temperature increase at the wall, demonstrating the influence of wall temperature conditions on the strength of knocking intensity.