【作者】 马骁；

【导师】 王建昕；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2010， 博士

【摘要】 以激光诱导荧光法(PLIF)为代表的内燃机缸内燃烧过程可视化研究是近年来车用发动机研发工作中的重要内容,目前我国在这一领域与国外先进水平相比还有明显差距,而新一代缸内直喷汽油机(GDI)的自主研发迫切需要建立先进可视化试验平台。本文即围绕这一目标开展研究工作。首先,搭建了内燃机激光测试可视化平台,包括可以工作于GDI模式的光学发动机、定容燃烧弹、激光片光系统、同步装置、燃油供给装置等,可以实现对发动机喷雾和缸内混合气状态进行包括PLIF在内的多种光学测量。完成了PLIF定量研究的标定和校正方法,并对标定的具体计算过程进行了部分改进。其次,开发了设计PLIF试验用多组分替代燃油的普遍方法,可以同时满足试验燃料与真实汽油的挥发特性相似性要求和试验用示踪剂与所代表组分同步挥发的要求,并实际设计了一种五组分替代燃油以配合轻中重三种示踪剂。通过变参数分析计算比较了多组分燃油不同配比方案的优劣,研究了温度、组分比例对同步挥发特性的影响,以及设计过程中改进气液平衡计算(VLE)收敛性的优化方法。基于理论计算和试验结果的综合分析从原理上提出了快速设计时筛选组分的优选原则。第三,用PLIF方法定量研究了多种GDI两段喷射策略下缸内的混合气浓度分布,对火花塞附近混合气浓度的不均匀性和循环变动进行了分析。采用优化的五组分燃油方案对缸内混合气分布进行了研究。重点研究了燃油轻、中、重三种不同组分在不同喷射策略下火花点火时刻的分布差异,基于获得的图像结果采用定量方法研究了火花塞附近混合气浓度的循环变动,对测试结果序列相对于平均结果的误差进行了评估,结果表明芳烃类荧光剂对误差的影响相对较大。最后,采用KIVA-3V程序(源代码),在与可视化结果对比的基础上,研究了不同转速、不同油量、不同二次喷射比例和喷射时刻等条件下混合气的状态和适宜的点火提前角范围。更多还原

【Abstract】 Optical diagnostics such as Laser-induced Fluorescence (PLIF) is now an important role in vehicle engine research. At present, the backwardness of domestic engine optical diagnostics researches compared to foreign advanced level is obvious. It is necessary to build advanced optical diagnostics systems and carry on researches in this field. As the development of gasoline direct injection (GDI) engine goes on, greater attention has been paid to in-cylinder mixture formation, especially to those researches basing on multi-component fuel. Improving the ability of PLIF method and taking a deeper step into the research of GDI in-cylinder mixture formation will be significant. This research worked in the field of GDI in-cylinder PLIF diagnostics.In this work, an internal-combustion-engine based laser diagnostic system, including an optical engine which can works in GDI mode, a combustion vessel, laser sheet optics, synchronization modules and fueling systems, has been built to realize PLIF researches on spray and in-cylinder mixture distribution. Calibration and correction methods were developed basing on the system, with some improvements in the calculation.A method of designing a multi-component fuel for planar laser-induced fluorescence (PLIF) experiments was developed based on thermal gravity (TG) analysis and vapor-liquid equilibrium (VLE) calculation. The goal is to create a fuel whose volatility is similar to real gasoline and that has good coevaporation ratios (near 1.0) with tracers. Acetone, toluene, and trimethylbenzene were chosen as the tracers for light, medium, and heavy fractions, and a five-component test fuel was developed. This test fuel was used to study the influence of components and temperature on coevaporation ratios. The saturate vapor pressure and the activity coefficient of the tracer and components in a fraction group affect the coevaporation optimization substantially, indicating that these values should be a primary consideration in tracer selection.PLIF was used to study different strategies and cycle-to-cycle variation in GDI in-cylinder mixture distribution. The five-component fuel was applied to an in-cylinder gasoline direct injection fuel mixture distribution measurement using PLIF. The differences between the light, medium, and heavy fraction groups were studied under different strategies. Cycle-to-cycle variation analysis was also applied.Finally, simulation works on mixture distribution were carried out basing on KIVA-3V. The best ignition timing and available ignition ranges under different rotation speeds, air-fuel ratios, injection times and fueling percentages of second injection are analyzed.更多还原