生物柴油替代混合物化学动力学模型构建及路径分析

以癸酸甲酯(C₁₁H₂₂O₂)和正庚烷(nC₇H₁₆)作为生物柴油替代混合物，通过相对分子质量、低热值以及含氧量与实际生物柴油对比确定两种组分按摩尔比1：1混合，并在此基础上构建了一个由691种组分、3226个基元反应组成的生物柴油替代混合物的化学动力学机理. 在激波管条件下该机理计算的着火延迟与实验数据吻合很好；在发动机条件下该机理计算的缸内压力与实验值吻合很好，CO、未燃碳氢和NOx与实验结果趋势一致.此外，本文还对替代混合物的低温反应动力学过程进行了分析，结果表明癸酸甲酯脱氢产物主要为MD2J和MDMJ. MD2J在低温阶段的主要消耗途径除了加氧之外,还有与正庚烷基(C₇H₁₅-1)第一次加氧产物(C₇H₁₅O₂-3)进行交叉反应；发生分解反应生成MP2D及与氧发生脱氢反应生成MD2D. 另一种主要脱氢产物MDMJ在低温阶段的主要消耗途径为通过同分异构转化为MD2J和MD3J.

Chemical Kinetic Model Development of Biodiesel Surrogate Fuel and Reaction Path Analysis

In the present study, methyl decanoate (C₁₁H₂₂O₂) and n-heptane (nC₇H₁₆) were selected as a surrogate of biodiesel fuel. The molar ratio of the two constituents was determined to be 1:1, based on a comparison of the relative molecular weights, low heat values, and oxygen contents of the surrogate fuel and real biodiesel fuel. Furthermore, a chemical kinetic model including 691 species and 3226 elementary reactions of this biodiesel surrogate fuel was developed. The ignition delay times from experiments and calculations, under shock tube conditions, were compared; the computational results agree well with the experimental results. Comparisons of the in-cylinder pressure and main emissions under the engine conditions showed that the in-cylinder pressure calculated using this model agrees very well with the experimental result, and the trends in variations in the amounts of CO, unburned hydrocarbons, and NO_x emissions calculated using this model are also close to the experimental results. In addition, the lowtemperature reaction kinetics was analyzed in this study. The results show that the main products of methyl decanoate H- abstraction are MD2J and MDMJ. Besides the oxygen addition reaction, the main consumption paths of MD2J include reaction with C₇H₁₅O₂-3 (the product of the first oxygen addition of C₇H₁₅-1), decomposition to MP2D, and H-abstraction by O₂ forming MD2D. The main consumption paths of MDMJ are conversion to its isomers, MD2J and MD3J.