Abstract:

To study the reaction mechanism and combustion characteristics of diesel fuel under CO₂/O₂ atmosphere, quantum chemical calculations and optical experiments were performed. The reactive sites on molecules were analyzed by the average local ionization energy and surface electrostatic potential, and new chemical reactions were proposed by computational chemistry calculations, which were simplified after sensitivity analysis to compute the flame natural luminosity and the flame lift-off length. Finally, a constant volume combustion chamber experimental platform with optical channels was built and fluid mechanics simulation of diesel combustion was performed. Compared with the experimental results, the calculated maximum, minimum and average errors of the flame lift-off length under 35% CO₂+65% O₂ atmosphere were 13.9%, 0.5% and 1.4%, respectively, which were all acceptable and indicate the suitability of the new mechanism. It was found that high concentration carbon dioxide causes flame bifurcation and turbulence, which was pyrolyzed into carbon monoxide and oxygen radicals at high temperatures, and the chemical reactivity of carbon atom was greater than that of oxygen atom, with an average local ionization energy of 12.62eV and a very small electrostatic potential of -0.51eV.

Key words: computational chemistry, average local ionization energy, surface electrostatic potential, constant volume combustion chamber, fluid mechanics, carbon dioxide

摘要：

为研究柴油在CO₂/O₂氛围下燃烧反应机理与燃烧特性，本文提出了量子化学计算的机理与光学实验，通过分子平均局部离子化能和表面静电势分析分子的反应活性位点，通过计算化学计算了新的化学反应路径，对反应路径进行敏感性分析和简化，然后计算了火焰自然光度和火焰浮起长度，最后搭建了具备光学通道的定容燃烧弹实验平台并进行柴油燃烧的流体力学模拟。计算结果与实验结果对比结果表明，在35% CO₂+65% O₂氛围下火焰浮起长度最大误差、最小误差和平均误差分别为13.9%、0.5%和1.4%，均为可接受的误差，说明此机理适用于CO₂/O₂氛围下柴油燃烧特性的研究。高浓度二氧化碳会致使火焰发生分叉，引起湍流现象，并且二氧化碳在高温下会热解成一氧化碳和氧自由基。一氧化碳的碳端化学反应活性比氧端的大，碳端平均局部离子化能为12.62eV且静电势极小值为-0.51eV。

关键词: 计算化学, 平均局部离子化能, 表面静电势, 定容燃烧弹, 流体力学, 二氧化碳