A statistical approach to develop a detailed soot growth model using PAH characteristics
A statistical approach to develop a detailed soot growth model using PAH characteristics
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DOI：
10.1016/j.combustflame.2009.01.005
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发表时间：
2009-04
影响因子：
4.4
通讯作者：
A. Raj;M. Celnik;Raphael Shirley;Markus Sander;R. Patterson;R. West;M. Kraft
中科院分区：
文献类型：
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作者：
A. Raj;M. Celnik;Raphael Shirley;Markus Sander;R. Patterson;R. West;M. Kraft
建立了详细的多环芳烃生长模型，并用动力学蒙特卡罗算法进行了求解。该模型描述了平面多环芳烃分子的结构和生长，称为动力学蒙特卡罗芳香族中心(KMC-ARS)模型。基于文献中提供的自由基位上的反应，以及从量子化学计算中获得的附加反应，详细的多环芳烃生长机理被用来模拟多环芳烃的生长过程。本文基于密度泛函理论模拟计算了多环芳烃上环脱氢形成六元环的新反应速率。KMC-ARS模型通过将实验观测到的多环芳烃上的系综与燃烧器上方不同高度的C2H2和C6H6火焰的计算系综进行比较，验证了KMC-ARS模型。这一模型的动机是开发了一个详细的烟尘颗粒种群平衡模型，该模型描述了基于其多环芳烃结构的烟尘颗粒集合的演化。然而，目前将这样一个详细的模型纳入人口平衡在计算上是不可行的。因此，发展了一种更简单的模型，称为位置计数模型，它用统计闭合表达式增强的官能团来代替多环芳烃分子的结构信息。这一闭合是从KMC-ARS模型获得的，该模型用于在不同的火焰环境中建立描述此类多环芳烃结构信息的关联式和统计量。这些相关性和统计量被实现在站点计数模型中，站点计数模型和KMC-ARS模型的结果具有很好的一致性。此外，我们还研究了空间位阻对大分子多环芳烃结构的影响，并给出了无法进行反应的位置的关联式。
A detailed PAH growth model is developed, which is solved using a kinetic Monte Carlo algorithm. The model describes the structure and growth of planar PAH molecules, and is referred to as the kinetic Monte Carlo–aromatic site (KMC-ARS) model. A detailed PAH growth mechanism based on reactions at radical sites available in the literature, and additional reactions obtained from quantum chemistry calculations are used to model the PAH growth processes. New rates for the reactions involved in the cyclodehydrogenation process for the formation of 6-member rings on PAHs are calculated in this work based on density functional theory simulations. The KMC-ARS model is validated by comparing experimentally observed ensembles on PAHs with the computed ensembles for a C2H2and a C6H6flame at different heights above the burner. The motivation for this model is the development of a detailed soot particle population balance model which describes the evolution of an ensemble of soot particles based on their PAH structure. However, at present incorporating such a detailed model into a population balance is computationally unfeasible. Therefore, a simpler model referred to as the site-counting model has been developed, which replaces the structural information of the PAH molecules by their functional groups augmented with statistical closure expressions. This closure is obtained from the KMC-ARS model, which is used to develop correlations and statistics in different flame environments which describe such PAH structural information. These correlations and statistics are implemented in the site-counting model, and results from the site-counting model and the KMC-ARS model are in good agreement. Additionally the effect of steric hindrance in large PAH structures is investigated and correlations for sites unavailable for reaction are presented.