柴油机燃烧多环芳香烃前驱体等物质的化学动力学研究

Study on PAH Precursors and Other Important Species in Diesel Engine Combustion Using Detailed Chemical Kinetics

为了揭示混合气浓度对柴油机排放的影响规律,采用正庚烷氧化详细反应机理及化学动力学分析软件对不同燃空当量比下柴油机燃烧初级碳烟粒子前驱体等重要反应中间产物或自由基的形成及发展历程进行了数值模拟.模拟结果表明,降低混合气浓度可以实现低温燃烧,使燃烧温度远离“碳烟形成温度窗”,大幅度降低柴油机碳烟排放.混合气浓度对反应中间产物或自由基有重要影响,通过改变混合气浓度可以控制燃烧过程中多环芳香烃(PAH)前体物乙炔(C2H2 )、炔丙基(C3H3 )及其他重要物质羟基(OH)、过氧羟自由基 (HO2 )、过氧化氢 (H2O2 )、甲醛(CH2O)和一氧化碳(CO)等的生成量,从而实现控制柴油机排放.

In order to reveal the effects of mixture concentrations on diesel engine exhaust emissions, by using a detailed chemical kinetic mechanism of n-heptane oxidation and chemical kinetics analysis code, numerical simulations were made on the formation and development course of young soot precursor particles and other important intermediates or radicals in diesel engine combustion processes, whose fuel-air equivalence ratios are from 0.3 to 0.6. The results indicate that, by reducing the mixture concentration, lower temperature combustion can be achieved. The soot emissions sharply decrease when combustion temperatures are away from the temperature window of soot formation. The mixture concentration has a significant impact on reaction intermediates or radicals. The aggregate yields of acetylene (C2H2) and propargyl (C3H3), which are precursors of polycyclic aromatic hydrocarbons (PAH), and other important species, such as hydroxide radical (OH), hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), formaldehyde (CH2O) and carbon monoxide (CO) in the process of fuel combustion, can be successfully controlled by means of altering the mixture concentration, and then the control of exhaust emissions from a diesel engine can be obtained.