正庚烷燃烧详细化学动力学模型的简化及其有效性分析  

Reduction of a Detailed Chemical Kinetics Model of N-Heptane Combustion and Its Validity Analysis

作　　者：赵昌普[1] 陈生齐[1] 李艳丽[1] 孙强[1] 宋崇林[1] 

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《内燃机学报》2008年第4期346-352,共7页Transactions of Csice

基　　金：国家自然科学基金资助项目(50676067);国家重点基础研究发展规划资助项目(2002CB211603)

摘　　要：为了应用CFD多维数值分析模型研究柴油机排放中多环芳香烃(Polycyclic Aromatic Hydrocarbons,PAH)生成和变化规律,很有必要发展一个简化的、包含PAH形成和生长机理的正庚烷燃烧化学反应动力学模型。通过敏感性分析,找到了柴油模拟燃料正庚烷燃烧过程的18个重要反应,其中8个过氧烷基(C7H15O2)的异构化反应,5个过氧羟庚基(C7H14OOH)的分解反应,2个正庚烷(NC7H16)被羟基氧化的反应,2个过氧化氢酮(NC7KET)的裂解反应及1个过氧化氢的分解反应,并对其作用进行了分析。在保留这18个重要反应及与PAH形成重要前体物相关的重要反应的基础上,构建了包含46种物质77个基元反应(记为46/77)和37种物质45个基元反应(记为37/45)两个简化动力学模型,并对其有效性进行了验证。结果表明,两种简化模型缸内压力和温度曲线均与包含544种物质2 446个基元反应的详细模型(记为544/2 446)吻合得较好,而46/77简化模型更能准确地模拟燃烧相位、缸内压力及温度的变化过程。通过与544/2 446详细模型比较,发现37/45简化模型可以较好地模拟CO、H2O2、CH2O、OH的产生和变化历程,而46/77简化模型可以较好地模拟C2H2、NC7H16、HCO的生成和消耗过程。CFD multi-dimensional numerical analysis is implemented to study the formation and development history of PAHs in diesel engines. A reduced chemical reaction kinetics model for the n-heptane combustion, containing the PAH formation and growth mechanism is proposed. Eighteen main reactions of the combustion process were summarized through the sensitivity analysis method, containing eight peroxy-alkyl radical （C7H15O2 ） isomerization, five hydroperoxy-heptyl radical decomposition, two n-heptane （NC7H16） oxidation by hydroxide radicals, two ketohydroperoxide molecule（ NCTKET） degradation and one hydrogen peroxide decomposition. Based on these 18 reactions and other important reactions related to the formation of PAH precursors, one reduced kinetics model composing of 46 species and 77 elementary reactions （46/77） and another containing 37 species and 45 elementary reactions （37/45） are proposed. Results showed that the simulated cylinder pressure and temperature traces using two reduced models were in good agreement with those from the detailed model. Comparing the computed results of the detailed 544/2 446 model, the reduced 37/45 model could simulate the formation and change history of CO, H2O2, CH2O and OH better than the reduced 46/77 model. The reduced 46/77 model can better simulate the formation and consumption processes of C2H2, NC7H16 and HCO.

关 键 词：柴油机 简化模型 数值模拟 敏感性分析 自由基 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]