通过AVL Fire软件建立了4B26柴油机的燃烧模型，并耦合甲醇正庚烷的化学反应机理文件，研究了柴油机燃用甲醇柴油混合燃料着火过程中，缸内温度、燃料浓度和中间产物的变化规律，并分别依据放热率、中间产物、温度的变化对滞燃期进行了计算。研究结果表明，在甲醇正庚烷着火之前，与甲醇分解有关的中间产物中，CH2O，H2 O2，OH变化最显著，且中间产物浓度呈双峰走势；－7°~－5°范围内，与甲醇相比，正庚烷发生了明显的脱氢反应。正庚烷低温分解相关的主要基元反应中，生成CH4，C2H4，C3H6的基元反应更容易发生。根据瞬时放热率、正庚烷脱氢、OH浓度、缸内温度场变化等方法确定的甲醇正庚烷着火时刻分别为－7.2°，－7°~－5°，－2.4°，－5.8°。几种判断方法中，依据OH浓度变化判断的着火时刻较晚。
The combustion process model of 4B26 diesel engine was established by AVL Fire software, the chemical reaction mechanism of methanol/nheptane was adopted, the changing law of incylinder temperature, fuel concentration and intermediate products were studied during the ignition process of methanol/diesel fuel on a diesel engine, and the ignition delay period based on the heat release rate, the intermediate product and the temperature was calculated. The results indicate that CH2O, H2O2 and OH show the most significant change among the intermediate products related to methanol decomposition before the ignition of methanol/nheptane and the intermediate product concentration shows the trend of double peaks. In the range between －7° and －5°, the dehydrogenation reaction of nheptane has been observed obviously compared with methanol. In the main reactions related to nheptane decomposition at low temperature, the CH4, C2H4 and C3H6 elementary reactions were more likely to occur. According to the instantaneous exothermic rate, the dehydrogenation of nheptane, OH concentration and the change of incylinder temperature field, the corresponding ignition timing of methanol/nheptane is －7.2°, －7°~－5°, －2.4° and －5.8°respectively. The determined ignition timing from OH concentration is relatively late in all kinds of judgments.
