HCCI燃烧中NO与异辛烷相互作用简化动力学模型构建与分析

为了分析废气再循环中NO对HCCI燃烧的影响,本文构建了一个新的NO与异辛烷相互作用的化学动力学机理,包括167种组分和835个反应,其中异辛烷分支反应包括112种组分和467个反应。NO分支的子机理是在Anderlohr等人对NO与异辛烷详细机理研究的基础上根据路径分析而得到的。新IC₈H₁₈-NO机理的验证分为:IC₈H₁₈分支机理验证了在激波管中温度范围为855-1269 K,压力范围为2-6 MPa,化学计量比为0.5和1.0条件下的着火延迟时间; IC₈H₁₈-NO机理验证了在HCCI发动机中NO添加浓度为0-500 × 10^-6(体积分数),同时也发现不同的NO添加浓度对IC₈H₁₈的HCCI燃烧的影响有所不同。因此,本文利用CHEMKINPRO软件中的零维单区化学动力学模型,模拟了在不同NO浓度下NO对异辛烷燃烧影响。通过敏感性分析和产率分析,得出了NO添加后对异辛烷燃烧影响的关键性反应为R476。在IC₈H₁₈燃烧初期通过R476产生活性基OH,从而体现对燃烧的促进作用。但是在NO添加浓度较大时,由于NO浓度较大结合活性基(如OH)的能力增强,进而NO对燃烧的促进作用被削弱。

Generation and Analysis for a Skeletal Chemical Kinetic Model of IC8H18 with Nitric Oxide in HCCI Combustion

A new mechanism for IC₈H₁₈ with nitric oxide (IC₈H₁₈-NO) in homogeneous charge compression ignition (HCCI) combustion is presented to investigate the effects of NO in exhaust gas recirculation (EGR) on combustion. The IC₈H₁₈ sub-mechanism consists of 112 species and 467 reactions. A NO sub-mechanism is developed through reaction path analysis. The reaction paths of NO are summarized on the basis of the detailed NO mechanism reported by Anderlohr to describe the effects of NO on IC₈H₁₈. A new IC₈H₁₈-NO mechanism with 167 species and 835 reactions is described. The IC₈H₁₈ sub-mechanism of IC₈H₁₈-NO mechanism was validated by the ignition delay times in a shock tube. Experimental and computational results are in good agreement with those of ignition delay times at 855 to 1269 K and at 2 and 6 MPa with equivalence ratios of 0.5 and 1.0. The new IC₈H₁₈-NO mechanism is also validated in an HCCI engine. Computational results are consistent with experimental data of ignition delay times at a NO concentration range of 0 to 500 × 10^-6 (volume fraction). The effects of NO on IC₈H₁₈ differ as the NO concentration increases. Therefore, the effects of NO on IC₈H₁₈ are simulated using a zero-dimensional model using the CHEMKIN PRO software. Key reactions at different NO concentrations are proposed by analyzing the sensitivity and productivity rates. The resource of OH for initial IC₈H₁₈ consumption is mainly generated through R476, which occurs as a result of the promoting effect of NO on IC₈H₁₈ consumption. The ability of NO to combine with active radicals, such as those in R476, is enhanced as the NO concentration is increased.