4类碳氢燃料的高温燃烧反应简化建模

Simplified Kinetic Modeling of High Temperature Combustion Reactions of Four Hydrocarbon Fuels

以正辛烷(n-C8H18)、异辛烷(i-C8H18)、甲基环己烷(CH3cyC6)和正丁基苯(A1C4H9)4类大分子碳氢燃料为对象,探究了简化建模方法对含不同官能团的碳氢化合物燃烧反应动力学的适用性。建立了上述4类碳氢燃料的简化反应动力学模型,包含124个化学组分和854个基元反应;采用热解反应和氧化反应过程的主要中间产物分布、点火延时时间、层流燃烧速率等基础燃烧数据对该模型进行验证;分析了4类燃料中间产物的碳分布及对宏观燃烧特性的影响;以n-C8H18为例,采用误差传播直接关系图谱法对所建简化模型进行进一步简化,简化后的模型包含56个化学组分和387个基元反应。结果表明:本简化建模方法不仅对直链烷烃和支链烷烃有较好描述,同时适用于环烷烃和烷基芳香烃的燃烧化学;不同官能团的大分子碳氢燃料裂解中间产物的不同决定了其宏观燃烧特性;该建模方法通过进一步简化,可有效与先进计算流体力学CFD软件或代码耦合,用于对真实发动机系统的仿真模拟。

The applicability of a simplified modeling approach to describe the combustion chemistry of macromolecular hydrocarbon fuels with different functional groups is explored by taking n-octane(n-C8H18),iso-octane(i-C8H18),methyl cyclohexane(CH3cyC6)and n-butyl benzene(A1C4H9)as four macromolecular hydrocarbon fuels.One unified kinetic model for above four fuels is constructed,consisting of 124 chemical species and 854 elementary reactions.The model is verified by using the fundamental combustion data such as distribution of main intermediate products in oxidation and pyrolysis reactions,ignition delay time and laminar flame speed.The carbon distributions of the main intermediate products of four fuels and their influences on the global combustion characteristics are examined.Taking n-octane as an example,the number of chemical species and elemental reactions in the above simplified model is further reduced to 56 and 387,respectively,by the directed relation graph with error propagation.These results show that the above simplified modeling method describes the combustion chemistry of linear and branched alkanes well,and can be applied to that of cycloalkanes and alkyl aromatics;the distinct intermediate products generated from the macromolecular hydrocarbon fuels with different functional groups eventually determine their global combustion characteristics;and this modeling method can be effectively coupled with CFD software or code for the simulation of real engine system after further simplification.