An extended methodology for automated calculations of non-Boltzmann kinetic sequences: H + C2H2 + X and combustion impact
An extended methodology for automated calculations of non-Boltzmann kinetic sequences: H + C2H2 + X and combustion impact
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自动计算非玻尔兹曼动力学序列的扩展方法：H C2H2 X 和燃烧影响
DOI：
10.1016/j.proci.2020.06.385
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发表时间：
2021
影响因子：
3.4
通讯作者：
Burke, Michael P.
中科院分区：
文献类型：
--
作者：
Lei, Lei;Burke, Michael P.
在唯象动力学模型中，通常假设双分子反应仅发生在振动能遵循玻尔兹曼（热）分布的物质之间。也就是说，假设最初以非玻尔兹曼分布形成的任何复合物在双分子反应之前通过能量转移碰撞而热化。鉴于燃烧环境中活性物质 X 的摩尔分数较高，配合物与 X 的反应碰撞通常与能量转移碰撞发生在同一时间尺度上，从而产生穿过多个势能表面的非玻尔兹曼中间体进行的序列。最近的研究表明，这种非玻尔兹曼动力学序列可以对燃烧系统的整体反应性产生重大影响。这些非玻尔兹曼反应序列的模拟可以通过化学术语分子反应在唯象动力学模型中进行描述，需要将一个势能表面的振动激发转移到下一个势能表面。本文提出了一种扩展的理论和计算方法，该方法耦合了多个主方程并推导了现象学反应的速率常数，描述了热反应物到热产物的转化，用于现象学动力学方案。然后使用涉及 C 2 H 3*+ X（其中 X= O 2、H 和 OH）的非玻尔兹曼序列的内部脚本实施该方法，其中 C 2 H 3* 通过 H+ C 2 H 2 关联形成，在最近的研究中被认为具有影响燃烧预测的强大潜力。结果表明，X= O 2 的非玻尔兹曼反应序列（本文的主要焦点）显着改变了热序列路径中从 H+ C 2 H 2 到产物和产物分支分数的总转化率。此外，目前的结果表明，非玻尔兹曼反应序列对预测的点火延迟时间具有高达一个数量级的显着影响。类似地，它们产生了显着不同的点火延迟时间与温度和O 2 摩尔分数的依赖性——产生可能通过实验观察到的特征。
It is generally assumed in phenomenological kinetic models that bimolecular reactions only occur between species whose rovibrational energy follows a Boltzmann (thermal) distribution. That is, any complexes initially formed in non-Boltzmann distributions are assumed to be thermalized by energy-transferring collisions prior to bimolecular reactions. Given the high mole fractions of reactive species, X, in combustion environments, reactive collisions of the complexes with X often occur on the same timescale as energy-transferring collisions–yielding sequences proceeding through non-Boltzmann intermediates across multiple potential energy surfaces. Recent studies have shown that such non-Boltzmann kinetic sequences can have substantial impact on the global reactivity in combustion systems. Simulations of these non-Boltzmann reaction sequences, which can be described in phenomenological kinetic models via chemically termolecular reactions, require that rovibrational excitation from one potential energy surface be carried over to the next. This paper presents an extended theoretical and computational methodology that couples multiple master equations and derives rate constants for phenomenological reactions describing the conversion of thermal reactants to thermal products for use in phenomenological kinetic schemes. The methodology is then implemented using in-house scripts for non-Boltzmann sequences involving C 2 H 3*+ X (with X= O 2, H, and OH) where C 2 H 3* is formed via H+ C 2 H 2 association–which were identified as having strong potential for influencing combustion predictions in a recent study. The results reveal that non-Boltzmann reaction sequences for X= O 2 (the primary focus of this paper) significantly alters the total conversion rate from H+ C 2 H 2 to products and product branching fractions from those of thermal sequential pathways. Furthermore, the present results demonstrate that non-Boltzmann reaction sequences have significant impact–as high as an order of magnitude–on predicted ignition delay times. Similarly, they yield significantly different dependence of ignition delay times with temperature and O 2 mole fraction–yielding signatures that are likely observable experimentally.
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影响因子：
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