先进液压自由活塞发动机中燃烧过程关键问题的研究

本申请所提出的先进液压自由活塞发动机具备：对置活塞、PPM调频、切向进气口直流扫气、HCCI燃烧的特征。由于不受曲柄连杆机构的束缚，活塞的运动规律具有上止点停留时间短、膨胀速度快的特点，并且活塞的运动规律与缸内的燃烧过程具有较强的耦合关系；切向进气口的直流扫气作用，导致了缸内残余废气浓度分层分布的可能性。本研究针对上述燃烧过程的特点，通过大涡模拟加详细化学反应动力学模型的仿真研究，结合光学发动机的模拟实验，以及实际样机的台架实验，对燃烧过程中热功转化效率的影响因素，有害排放物NOx的形成规律，爆震发生的机理开展研究，探索通过发动机结构参数设计、EGR、运行参数控制等手段，在液压自由活塞发动机中实现高效、清洁燃烧过程的方法，探讨在液压自由活塞发动机中拓展HCCI燃烧模式工况运行范围的途径。

The advanced hydraulic free piston engine proposed here comprising such characteristics as: opposed piston, PPM frequency control, uniflow port scavenging, HCCI combustion mode. Out of the restraining of the crank-link mechanism, the movement of the piston has such characteristics as short staying time at TDC, rapid expansion, strongly coupling with the combustion process in the cylinder.The uniflow scavenging process of the tangential inlet port makes the residual exhaust gas concentration stratified distribution.Considering of the particularity in combustion process said above, factors affecting conversion efficiency in combustion process, NOx creating process and knock occurrence mechanism will all be studied after simulation research based on large eddy simulation with detailed chemical reaction kinetics, and experiments study on an optical engine and a prototype engine in this application. The method will be explored to reach efficient and clean combustion process by structural parameters design, EGR, and operation parameters control.The way will also be explored that how to expansion the HCCI combustion mode operating range in a hydraulic free piston engine.