多构象、非谐振耦合的生物柴油不饱和甲酯替代燃料燃烧机理研究

Great achievements have been made in saturated fatty acid methyl ester (FAME) combustion models of biodiesel surrogates. However, the combustion model studies of unsaturated fatty acid methyl esters (uFAMEs) still lag far behind the saturated ones. In fact, the content of uFAMEs contains more than 50% in the biodiesel. Moreover, the FAMEs would also produce small uFAMEs in the combustion process. Hence, the combustion mechanism of uFAMEs is crucial for the mechanism construction of biodiesel surrogates. Focusing on three uFAMEs including methyl acrylate (MA), methyl 3-butenoate (MB), and methyl crotonate (MC), the objective of this proposal is to explore the microscopic reaction mechanism and macroscopic combustion properties combined quantum chemical calculation, shock tube experiment and kinetic modeling. Theoretically, the main reaction channels of three uFAMEs are determined by the corresponding potential energy surfaces (PESs). In order to solve the problem of accurate thermodynamic and kinetic parameter calculations in uFAMEs combustion model, the multistructural and torsional anharmonicity of species are introduced into the rate constant calculations of the key elementary reactions. Furthermore, the combustion kinetic models of three uFAMEs are constructed based on the core mechanism and quantum chemical calculations in wide temperature- and pressure-dependent ranges. Experimentally, the ignition delay times of three uFAMEs are measured by shock tube and the rationality of combustion kinetic models is further validated by the experimental results under a wide temperature and pressure conditions. This research will provide valuable theoretical basis for the automated generation of large uFAMEs combustion mechanism.

生物柴油替代模型的研究在饱和甲酯方面已取得了丰硕成果，但不饱和甲酯的研究仍存在明显滞后。生物柴油中不饱和甲酯的含量超过50%，且饱和甲酯燃烧过程中也会形成小分子不饱和甲酯。因此，不饱和甲酯燃烧机理对生物柴油替代模型的构建至关重要。本项目以三种典型不饱和甲酯：丙烯酸甲酯（MA）、3-丁烯酸甲酯（MB）、巴豆酸甲酯（MC）为对象，结合量子化学计算，激波管实验以及动力学模拟等手段，探究不饱和甲酯燃烧的微观反应机制和宏观特性规律。理论方面，基于势能面计算确定主要的反应通道，将物种的多构象、非谐振耦合效应引入关键基元反应的速率常数计算，解决不饱和甲酯燃烧机理构建中热、动力学参数的精确计算问题；基于核心机理，构建以量子化学计算为基础的不饱和甲酯燃烧机理。实验方面，采用激波管测量三种燃料不同工况的点火延迟时间，以实现燃烧机理宽参数范围的实验验证，为大分子不饱和甲酯燃烧机理的自动化生成提供理论基础。

不饱和甲酯的燃烧机理研究对生物柴油替代模型的构建至关重要。本项目围绕三种典型不饱和甲酯：丙烯酸甲酯（MA）、3-丁烯酸甲酯（MB）、巴豆酸甲酯（MC），开展系统的量子化学计算和激波管实验测量。基于高精度势能面确定燃料分子的主要反应通道，将物种的多构象、非谐振耦合效应引入关键基元反应的速率常数计算，明确多重效应下不饱和甲酯的多势阱、多通道压力依赖反应动力学竞争机制，解决不饱和甲酯燃烧机理构建中的热、动力学参数精确计算问题。通过实验测量获得C4和C5不饱和酯宽温度、压力和当量比下的点火特性规律，并与已有饱和酯的点火特性对比，发现C4不饱和酯点火延迟时间快于对应饱和酯，而C5不饱和与饱和酯之间的点火特性无明显差别。结合实验与理论计算，构建和发展包含MA、MB和MC的高精度不饱和甲酯燃烧动力学模型，通过机理模拟分析，明确不饱和甲酯燃烧的微观反应机理与宏观点火特性的对应关系，从分子层面阐明影响不饱和甲酯点火特性规律的根本原因，形成了宽参数范围内燃料燃烧机理研发与激波管实验验证的相互支持的自主研究模式。本项目的研究成果有助于深入理解不饱和甲酯燃烧反应机理，为大分子生物柴油替代模型的发展提供重要的实验和理论数据。