可控自燃汽油机瞬变工况燃烧畸变机制及调控研究

The engine running on the car is mostly in the transient state condition, and the performance often deviates from the steady state condition and even worsens significantly. Controlled Auto-Ignition is a high efficient clean combustion technology, recognizing the engine performance under transient state conditions is of great significance and value to promote the practical application on the vehicle. This project intends to focus on the study of combustion distortion phenomenon as shown in the transient state conditions of controlled auto-ignition engine combined with the real engine test, optical test and theoretical analysis methods, to establish a quantitative evaluation method for combustion distortion, and combined with combustion boundary regulation to prove in cylinder macro and micro local combustion distortion rules and characteristics systematically; to study the chemical dynamic mechanism of critical combustion boundaries on the transient combustion distortion, and to identify the combustion distortion mechanism and approach, and find out the main inducements of different combustion distortion characteristics; to determine the effect of combustion distortion on engine performance and harmful substance emissions, and define the optimum range of sensitive combustion distortion parameters; to suppress combustion distortion and lift working performance in transient conditions based on the active control strategies of transient combustion boundaries. This project will not only provide reference and guidance for the exploitation and optimizing control of controlled auto-ignition engine, but also help to enrich the combustion theory of internal combustion engine in China.

发动机在实车运行时多处于瞬变工况，且性能经常会偏离稳态工况，甚至发生显著恶化。可控自燃是一种高效清洁燃烧技术，认清其在发动机瞬变工况下的工作性能对促进其实车高效清洁应用具有重要意义和价值。本项目拟结合实机试验、光学测试和仿真分析等手段，针对可控自燃发动机瞬变工况已展现出的燃烧畸变现象进行研究，建立燃烧畸变定量评价方法，结合燃烧边界调控系统地探明可控自燃发动机瞬变工况缸内宏观及微观局部的燃烧畸变特点和规律；研究关键燃烧边界对瞬变工况燃烧畸变的化学动力学作用机理，明确瞬变工况燃烧畸变机制及途径，找出不同燃烧畸变特征的主要诱因；确定燃烧畸变对发动机性能和有害物排放的作用效能，界定出关键燃烧畸变参数的优化取值范围；基于主动控制瞬变燃烧边界的策略抑制瞬变工况燃烧畸变、提升工作性能。本项目研究不仅对我国可控自燃发动机的开发和优化控制具有一定参考和指导价值；同时，还有助于丰富我国的内燃机燃烧理论。

发动机瞬变工况是汽车实际行驶中常见情况，对整车油耗和排放起到至关重要的作用。针对可控自燃发动机燃烧和性能变化特性进行研究，认清发动机实际工作瞬态循环下可控自燃模式燃烧和排放畸变关键诱因与机制，无疑会对可控自燃发动机瞬变工况优化技术策略的制定，发动机和整车高效、清洁运转过程的实现等均具有积极的推动作用。有鉴于此，本项目首先针对支撑汽油机可控自燃燃烧模式实机实现的高自由度可变气门升程及正时系统进行了开发，提出了新型机构构型，研究了机构关键结构和控制参数对气门运动特性、响应性等的影响，并在实机进行了搭载测试及应用性能分析；耦合进-排气门升程和正时的联合调控，在试验样机上实现了可控自燃燃烧模式的稳定实施，并基于试验结果对一维和三维仿真研究平台进行了标定和验证。结合试验和仿真研究了过量空气系数、进气温度、进气压力、气门正时与升程等条件因素对汽油机可控自燃模式燃烧与排放特性等的影响；分析了多种瞬变工况下可控自燃燃烧模式燃烧和排放性能的变化规律，探索了节气门、进-排气门正时和升程等因素条件响应性及响应差异性对发动机主要燃烧和排放指标的抑制/促进作用，且结合三维仿真从缸内混合气形成、温度、压力等微观场变化层面对发动机性能偏离诱因进行了进一步探讨；同时，从引发可控自燃发动机瞬变工况燃烧畸变的关键燃烧边界着手，探索了有助于其性能提升的控制技术策略。本项目研究成果不仅有助于丰富现有内燃机燃烧理论，还可为可控自燃发动机开发和优化控制提供工程指导。