废气稀释下正庚烷-异辛烷高温反应过程的模拟

Simulation of High-Temperature Reaction Processes of n-Heptane and iso-octane Mixtures Diluted by Exhaust Gases

在废气稀释条件下,汽油机中的燃油会随着气流运动迅速进入燃烧室内的高温区进行燃烧.为了合理地描述这一过程对高温反应过程的影响,通过对正庚烷和异辛烷详细反应机理进行温度敏感性分析,得到了影响其低温和高温下的关键反应路径,构建了一个包含45种组分和57个基元反应的正庚烷和异辛烷汽油替代物简化化学反应机理.该简化化学反应机理的合理性得到了试验验证.借助本文的简化机理模拟了不同残余废气率下正庚烷和异辛烷的高温反应路径.通过化学反应路径的模拟发现,在高温反应过程中,正庚烷和异辛烷的消耗受到C4H8、C5H11、C6H13、C7H14和C8H16生成过程的影响;正庚烷的脱氢反应和异辛烷的裂解反应受到残余废气率的影响较大,而正庚烷的裂解和异辛烷的脱氢过程几乎不受残余废气率的影响.

In the case of the mixture diluted by exhaust gases,the fuel in gasoline engines will be quickly entrained by the flow in the cylinder into high-temperature regions and start burning. In order to reasonably describe the influence of this process on the exothermic process under high temperature,temperature sensitivity analysis was made of the detailed chemical reaction mechanisms of n-heptane and iso-octane,there key reaction paths under low and high temperatures were obtained,and then simplified n-heptane and isooctane gasoline surrogate chemical reaction mechanisms including 45 species and 57 elementary reactions were built and validated. The chemical reaction mechanisms were validated by the experimental data. High temperature chemical reaction paths of n-heptane and iso-octane under different exhaust gas rate were simulated with this simplified chemical kinetic mechanism. It can be found from the simulation of chemical reaction paths that under high temperature,the consumption of n-heptane and iso-octane is affected by the formation of C4H8,C5H11,C6H13,C7H14 and C8H16;residual gas rate influences the H atom abstraction of n-heptane and the pyrolysis reac-tions of iso-octane,but it has little effect on the pyrolysis reactions of n-heptane and the H atom abstraction of iso-octane.