Using an improved detailed soot model and based on a reduced diesel surrogate fuel chemical reaction mechanism of n-heptane/toluene,a computational validation study is performed on the veracity and effectiveness of the detailed soot model,which can predict the process of soot formation and oxidation in an optical engine and a single-cylinder diesel engine,respectively.In this detailed soot model,the effects of soot precursors including isomers of acetylene and PAHs on soot formation are considered.The result shows that the simulated in-cylinder combustion pressure,heat release curve and ignition timing are in excellent agreement with the experimental values.And the simulated 2-dimensional transient distributions of soot volume fraction are in good agreement with those obtained by the two-color method.The simulated change trend of soot emission value is in consistent with the experimental data.So the improved detailed soot model can achieve better prediction.Meanwhile,the changes of particle number concentration and average size in diesel engine obtained by the improved detailed soot model are studied.The result shows that the value of particle diameters increases dramatically at the start of the combustion and tends to get stable afterwards.%采用改进的详细碳烟模型,耦合了由正庚烷和甲苯组成的混合燃料的简化反应机理.在碳烟模型中,考虑了反应中生成的乙炔类异构体和多环芳香烃前驱物对碳烟颗粒成长过程的影响作用,分别以可视化发动机和单缸柴油机台架试验的结果,对详细碳烟模型预测柴油机碳炯生成和氧化过程的准确性和有效性进行了验证.结果表明,模拟得到的缸内压力、放热率曲线以及着火时刻和试验结果吻合较好,得到的碳烟浓度瞬态二维分布与采用双色法得到的试验结果较为接近,碳烟排放量的模拟值与试验值的变化趋势基本一致,因而本文的详细碳烟模型可较好地预测不同工况条件下柴油机碳烟颗粒排放的变化趋势.同时,采用提出的详细碳烟模型对柴油机内碳烟颗粒数密度和平均尺寸进行数值模拟,研究其在柴油机缸内的变化情况,结果表明,碳烟颗粒的直径在预混燃烧期和急燃期急剧增加,在缓燃期以及燃烧后期收敛于某一稳定值.
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