甲醇聚甲氧基二甲醚混合燃料燃烧过程仿真研究

作为一种清洁替代燃料，甲醇凭借优异的经济性与良好的燃烧能力，开阔了发动机等动力领域新的方向，也为实现世界范围内碳达峰及碳中和提供新的选择。在点燃式汽油机和压燃式柴油机中,甲醇均可以作为一种清洁燃料代替柴油或者汽油被使用。由于甲醇本身十六烷值仅为3--5，当甲醇用在柴油机上时，难以在现有压燃式发动机中直接燃烧，因此需要配合高十六烷值燃料，改善甲醇燃料的着火性能、降低自燃温度，以达到直接压燃的目的。

本文首先通过计算确定甲醇掺混高十六烷值、高含氧量燃料聚甲氧基二甲醚混合燃料的可压燃理论十六烷值掺混比例。经过计算得出，甲醇掺混比例低于30\%可以在柴油机中正常燃烧。
其次基于玉柴YC4FA130-50型号发动机进行简单的原机柴油燃烧实验，测得原机的外特性和负荷特性数据。之后通过GT-Power软件系统的分析了在不同负荷的工况下，M0-P100(纯$PODE_n$)、M10-P90（体积分数为10\%甲醇与90\%$PODE_n$混合，下同）、M20-P80和M30-P70四种不同甲醇掺混比例混合燃料在压燃发动机中的燃烧过程，详细讨论了掺混比例、转速、负荷等性能对发动机参数的影响。

结果表明：在聚甲氧基二甲醚中掺入甲醇以后，在低、中、高三种负荷下，发动机的缸内压力均会明显变小，燃料燃烧的滞燃期有所延长，初始放热点向后推迟。放热率方面，在中低负荷的工况下，甲醇掺混比例的增加会导致放热率的最高值先增大后减小，在高负荷下，放热率最大值呈现逐渐升高的趋势。
对于燃料的燃烧持续期，在低、中、高三种负荷下，当甲醇掺混比例相对比较低时，会使燃料的燃烧持续时间缩短，随着甲醇比例的增多，中低负荷下的燃烧持续时间有所延长。甲醇的掺混均会导致\ce{NO_x}的排放浓度降低，HC和CO的排放会有上升。

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