Modeling and Optimization of Trajectory-Based HCCI Combustion

该奖项支持内燃机新操作模式的基础研究，通过使用自由活塞发动机成为可能。在标准的汽车发动机中，活塞位置由曲轴转角固定。在自由活塞发动机中，活塞运动是独立控制的。这种控制可用于显著提高发动机效率并适应各种替代燃料。该项目可以为混合动力汽车提供模块化，清洁和高效的电源，并使可再生燃料得到广泛使用。由于交通占全国能源消耗的30%左右，这些进步可能对能源独立和环境质量产生重大有益影响。研究了自由活塞发动机均质压燃（HCCI）燃烧的动力学特性及其优化。利用自由活塞发动机，可以实时控制活塞运动以主动调节气缸容积，从而在燃烧事件之前、期间和之后调节气体压力-温度历史。这种额外的自由度使得能够在循环中实时优化HCCI燃烧的化学反应性和传热过程。为了实现上述目标，缸内过程的基本属性需要进行调查，以获得无约束的气体压力-温度历史的影响的见解。分别建立了化学动力学驱动模型和控制导向模型来预测活塞运动轨迹对HCCI燃烧效率和排放的影响。在此基础上，将开发优化方法，以实现最大可达到的燃油效率和排放效益，通过设计最佳的活塞轨迹。在自由活塞发动机和快速压缩膨胀机上的实验工作将有助于验证建模和优化结果。

This award supports the fundamental study of a new mode of operation for internal combustion engines, made possible through the use of a free piston engine. In a standard automobile engine, the piston positions are fixed by the crankshaft angle. In a free piston engine the piston motions are independently controlled. This control can be used to significantly improve engine efficiency and to accommodate a large variety of alternative fuels. This project could enable a modular, clean and highly efficient power source for hybrid vehicles, and enable the wide use of renewable fuels. Because transportation accounts for about thirty percent of the national energy consumption, these advances could have a major beneficial impact on energy independence and environmental quality. The research objective is to investigate the dynamics and the optimization of a new combustion mode: trajectory-based homogeneous charge compression ignition (HCCI) combustion enabled by the free piston engine. With a free piston engine, the piston motion can be controlled in real-time to actively regulate the cylinder volume, and thereby adjust the gas pressure-temperature history prior, during, and after the combustion event. This extra degree of freedom enables the in-cycle real-time optimization of the chemical reactivity and heat transfer processes of the HCCI combustion. To achieve the above objective, fundamental properties of the in-cylinder processes need to be investigated to gain insights of the influence of the unconstrained gas pressure-temperature history. Both chemical kinetics driven model and control oriented model will be developed to predict the effect of the piston trajectory on the efficiency and emissions of HCCI combustion. On this basis, optimization methods will be developed to achieve the maximum attainable fuel efficiency and emissions benefits by designing the optimal piston trajectory. Experimental work on a prototype free piston engine and a rapid compression and expansion machine will help to validate the modeling and optimization results.