适用于HCCI的正庚烷化学动力学简化模型的研究和比较

Study and Comparison of Reduced Chemical Kinetic Models of N-Heptane Oxidation for HCCI Engine

利用敏感性分析、主要组分分析以及准稳态假定3种方法,将含有44种组分和72个反应的SKLE正庚烷简化模型再简化到40种组分和56个反应;简化后的模型对滞燃期的预测结果与LLNL详细模型非常接近,与激波管实验结果基本吻合,适用于HCCI发动机的多维模型的计算.与其他模型比较发现,Patel等人的模型缺少在低温区起关键作用的反应,即二次加氧反应(.QOOH+O2.OOQOOH),而Tanaka等人的模型缺少了CO的主要生成历程;在HCCI发动机典型工况范围内,SKLE简化模型预测着火时刻与LLNL详细模型吻合最好,Tanaka等人模型和Patel等人模型表现稍差,说明构建简化动力学模型时必须保证低温反应路径主干完整,同时不能忽略CO的主要生成历程.

The SKLE model, which is a reduced chemical kinetic model of n-heptane oxidation for HCCI engine including 44 species and 72 reactions, is further reduced to a 40 species, 56 reaction model by means of sensitivity analysis, principal components analysis and steady-state approximation. The 56 reaction model could predict ignition delay for shock tube, and the prediction result is close to that using the LLNL detailed mechanism of n-heptane oxidation, and in good agrecment with the result of shock tube experiments. So the model can be applied to a multi-dimensional CFD model. Comparison with other models shows that the most sensitive reaction （ · QOOH＋ O2 ←→ ·OOQOOH）in the low-temperature region is not included in the Patel et al model, and that the main reactions describing CO formation are neglected in the Tanaka et al model. In comparison with the LLNL detailed mechanism, ignition delay times are correctly predicted by the proposed model and are underestimated by both the Tanaka et al model and Patel et al model under typical HCCI engine operating conditions. This indicates that both the main reaction pathways in the low-temperature region and the main reactions descri-bing CO formation are essential for the development of a reduced chemical kinetic model.