Soot-based Global Pathway Analysis: Soot formation and evolution at elevated pressures in co-flow diffusion flames
Soot-based Global Pathway Analysis: Soot formation and evolution at elevated pressures in co-flow diffusion flames
复制标题
DOI：
10.1016/j.combustflame.2021.01.007
复制
发表时间：
2021-05
影响因子：
4.4
通讯作者：
Dezhi Zhou;Suo Yang
中科院分区：
文献类型：
--
作者：
Dezhi Zhou;Suo Yang
高压燃烧的主要问题之一是其高烟灰产量。从化学动力学的角度来看，这种现象背后的确切而全面的机制仍然难以捉摸。在这项研究中，通过详细的有限速率化学和分子输运模拟了一系列加压（1-16 atm）同流乙烯扩散烟灰火焰。模拟很好地再现了实验最大烟灰体积分数及其随压力的变化规律。为了从复杂的烟灰反应系统中提取动力学信息，开发了一种基于烟灰的全局路径分析（SGPA）方法，通过考虑从气态物质到烟灰的碳元素通量来识别从燃料到烟灰的主要全局路径（GP）。使用 SGPA，揭示了高压下烟灰化学路径的主导性和敏感性。研究发现，增加压力会将第一环多环芳烃 (PAH) 的形成从 C 3 H 3 重组转移到涉及 C 2 H 2 的反应。在 1 个大气压下，用于表面生长的 C 2 H 2 的产生完全受 C 2 H 4 和 C 2 H 3 的 H 抽象控制。相反，在升高的压力下，用于表面生长的 C 2 H 2 的产生还受到许多其他反应（包括一些第三体）的影响。反应。 SGPA方法表明，12 atm下预测的PAH与实验数据不匹配主要是由于反应C 2 H 2+ A1CH 2= C 9 H 8+ H反应速率系数不确定性造成的。根据SGPA分析，以A2和C 2 H 2 为目标物种的基于误差传播有向关系图（DRGEP）的机制还原删除了C 9 H 8 、C 9 等重要物种H 7，导致烟尘场预测不准确。研究还发现，在火焰翼区域，GPs 与较重 PAH 物种 (A4-A7) 的综合优势甚至大于最主要的 GP，这表明较重 PAH 物种对烟灰成核和凝结起着关键作用，特别是在火焰翼区域。
One of the major concerns in high pressure combustion is its high soot yield. An exact and comprehensive mechanism behind this phenomenon, from a chemical kinetics perspective, is still elusive. In this study, a series of pressurized (1–16 atm) co-flow ethylene diffusion sooting flames are simulated with detailed finite-rate chemistry and molecular transport. The experimental maximum soot volume fraction and its scaling law with pressure are well reproduced by the simulations. To extract kinetic information from the complex sooting reacting system, a Soot-based Global Pathway Analysis (SGPA) method is developed to identify the dominant Global Pathways (GPs) from fuel to soot by considering carbon element flux from gaseous species to soot. Using SGPA, the dominance and sensitivity of soot chemical pathways at elevated pressures are revealed. It is found that increasing pressure shifts the first ring Polycyclic Aromatic Hydrocarbon (PAH) formation from C 3 H 3 recombination to reactions involving C 2 H 2. At 1 atm, the production of C 2 H 2 for surface growth is purely controlled by the H-abstraction of C 2 H 4 and C 2 H 3. In contrast, at elevated pressures, the production of C 2 H 2 for surface growth is also influenced by many other reactions including some third body reactions. The SGPA method reveals that the mismatch of predicted PAH with the experimental data at 12 atm is majorly caused by the rate coefficient uncertainty of the reaction C 2 H 2+ A1CH 2= C 9 H 8+ H. Based on the analysis by SGPA, the mechanism reduction based on Directed Relation Graph with Error Propagation (DRGEP) with A2 and C 2 H 2 as the target species deleted significant species such as C 9 H 8, C 9 H 7, incurring inaccurate soot field prediction. It is also found that the combined dominance of GPs with heavier PAH species (A4-A7) is even greater than the most dominant GP at the flame wing regions, indicating that heavier PAH species play critical roles for soot nucleation and condensation, especially at the flame wing regions.