高功率密度汽油机的早燃与超级爆震机理的燃烧基础研究

Pre-ignition and super-knock are the main obstacle to achieve energy saving and emission reduction in high power-density gasoline engine. They are also the key scientific issues in advanced internal combustion engines under extreme combustion condition. This project focuses on three key scientific research problems, including the ignition mechanism for particles in high pressure and high temperature combustible mixture under internal combustion engine conditions (pre-ignition mechanism), detonation initiation mechanism in the closed system (super-knock mechanism) and the control of deflagration and detonation in gasoline engine (suppressing methods). Advanced laser measurement, rapid compression machine experiment and strengthened engine test are adopted to investigate these three aspects. The origin of pre-ignition in high power-density gasoline engine will be identified and the pre-ignition mechanism in high pressure and high temperature combustible mixture will be clarified. Theory for the combustion system design in real engine will be provided. The condition required for detonation initiation will be proposed, the super-knock mechanism in a high pressure and high temperature closed system will be developed, and the detailed transition process from deflagration to detonation will be revealed. The new knock-suppression methods in high power-density gasoline engine will be proposed, with its control mechanism revealed and its practicability explored. The research in this project is of important theoretical value to high efficiency and high power-density engine combustion, and it is of great realistic significance to the industrialization application of the ultra boosted engine.

高功率密度汽油机是汽车节能的主流，其早燃和超级爆震是国际性难题，机理尚未探明。本课题拟围绕内燃机条件下高温高压可燃混合气氛围中的微粒物点火机制（早燃机理）、闭口系统中的爆轰起爆机制（超级爆震机理）、汽油机中爆燃爆轰调控（爆震抑制方法）三个关键科学问题，采用先进的激光测试、快速压缩机实验以及强化发动机试验的方法开展早燃-超级爆震的上述三方面有机结合的研究。以期鉴别出高功率密度汽油机中早燃的诱发源，获得高温高压可燃混合气中早燃机理，为实际发动机燃烧系统设计提供理论基础；提出超级爆震的起爆发生条件，获得高温高压闭口条件下超级爆震机理，揭示爆燃-爆震模态转换的详细过程； 提出高功率密度发动机中抑制早燃和超级爆震的新方法，揭示其调控机制，并探索实用化可行性。项目研究结果对高效高功率密度发动机燃烧有重要的理论价值，对超高增压发动机的产业化应用具有重要的实际意义。

本项目针对高功率密度汽油机的早燃和超级爆震问题，完成了：1）高温高压可燃混合气中机油液滴的蒸发与自燃，2）高温高压可燃混合气发生早燃后的燃烧模式转变规律，3）基于燃料和混合气性质的早燃与超级爆震抑制等三方面的研究工作。主要成果和重要结论如下：.（1）建立了一维瞬态多组分液滴蒸发数学模型，分析了包含多组分的机油液滴在高温高压环境中的蒸发过程，获得了液滴温度、蒸发速率等受环境温度、压力和液滴组分条件的影响规律。.（2）在快速压缩机上研究了液滴初始体积、环境温度和环境压力对机油液滴着火过程的影响，明确了机油液滴诱发混合气早燃的工况范围。.（3）发现了混合气均质着火后机油液滴在一定条件下会出现液滴爆炸现象，并揭示了对高温高压环境条件、液滴表面化学反应及燃烧室内压力波三种因素对机油液滴爆炸的诱发作用。.（4）提出了液滴与混合气相互作用图谱，将图谱区分为早燃区、无早燃且无液滴爆炸区和液滴爆炸区三个区域，对机油液滴与背景混合气相互作用模式的本质进行了解析，并据此尝试构建了基于早燃与液滴爆炸判定的机油油品设计准则。.（5）研究了早燃时刻和热力学状态与无爆震燃烧、常规爆震和超级爆震的关系。通过对不同燃烧模式特征参数的理论分析，获得了不同燃烧模式间的量化区分准则。.（6）研究了等压缩终点压力、等能量密度和等新鲜进气量条件下引入惰性气体（稀释燃烧）和空气（稀薄燃烧），以及长滞燃期燃料甲烷、丙烷对对超级爆震的影响超级爆震的影响。.以上研究成果对深入认识汽油机的燃烧过程有重要的参考价值，对理解早燃和超级爆震机理并解决早燃和超级爆震对开发高效汽油机具有重要的指导意义。