C2 H3与C2 H5 OH和CH3 HCO间的脱氢反应对乙醇-碳氢混合燃料燃烧过程的影响

摘要

The mechanism of C2 H3 new reactions on the combustion of ethanol/hydrocarbon blends was investigated at QCISD ( T )/6­311 ++G ( d, p )//B3LYP/6­311G ( d, p ) level. The results indicated 2H­abstraction channels with fast reaction rate: C2 H3+C2 H5 →OH TS1 →C2 H4+C2 H5 O and C2 H3+CH3 →HCO TS2 →C2 H4+CH3 CO. The rate constants of these two reactions were calculated via the ca­ nonical variational transition state theory( CVT) among a temperature range of 400—2000 K and a small cur­ vature tunneling correction was also considered. Path analyses about the n­heptane/ethanol and iso­octane/ethanol premixed flames were carried out with CHEMKIN. Compared with the experimental data, the predic­ tion was apparently improved for the species adjacent to the reaction paths of C2 H3 , after the addition of the new reactions of C2 H3 to each mechanism. However, few influences were observed on other large species ( e. g. C3 H4 , C4 H4 ) , which are far from the pathways of C2 H3 .%在QCISD(T)/6­311++G(d,p)//B3LYP/6­311G(d,p)的水平下计算了乙醇及乙醇燃烧裂解产物与C2 H3之间的脱氢反应机理,利用正则变分过渡态理论( CVT)结合小曲率隧道效应模型( SCT)计算400~2000 K范围内的速率,对比OH, H及CH3等自由基相似脱氢反应速率,选择2条具有较快反应速率的通道( C2 H3+C2 H5 OH →TS1→C2 H4+C2 H5 O和C2 H3+CH3→HCO TS4→C2 H4+CH3 CO)。将这2个反应耦合到正庚烷/乙醇混合燃料及异辛烷/乙醇混合燃料的机理中,利用CHEMKIN程序中预混火焰模型模拟混合燃料的燃烧过程并进行路径分析。对比相应的实验数据发现,改进的动力学模型对燃烧过程中C2 H3路径上相近组分的预测精度有较大改善,而对C2 H3路径上较远的组分丙炔( C3 H4)和乙烯基乙炔( C4 H4)等影响不大。