CAREER: Investigation of Fuel Sprays and Air Mixing in Lean Direct-Injection Four-Stroke Spark-Ignition Engines

摘要-李 本文研究了稀薄直喷发动机燃油喷雾混合与燃烧的相互作用。 先进的光学诊断和多维建模用于表征缸内燃料/空气混合和燃烧的光学可访问，直接喷射发动机。 光学诊断包括用于在点火条件下可视化液体和蒸气燃料的空间分布的激基复合物荧光、用于可视化液体燃料的具有燃料掺杂剂的平面激光诱导荧光（PLIF）以及用于表征喷雾的液滴尺寸和速度的相位/多普勒粒子分析（P/DPA）。 此外，一种新的平面液滴尺寸测量技术的开发，通过成像激基复合物液体荧光和米氏散射信号的同时，这些信号的比例是成比例的索特平均直径和该技术可以使用P/DPA测量校准。 计算范围内的两相反应流，已被用于喷雾和发动机测量的比较模型。 本文的研究结果为设计一台成功的稀薄直喷火花喷射发动机提供了基础。 这样的发动机被认为提供改进的燃料经济性和减少的排放，但是其发展受到对燃料喷射、混合和燃烧之间的关系的不好理解的阻碍。

Abstract - Lee This is a study of the interaction of fuel spray mixing and combustion in a lean direct-injection engine. Advanced optical diagnostics and multi-dimensional modeling are used to characterize in-cylinder fuel/air mixing and combustion in an optically accessible, direct-injection engine. Optical diagnostics include exciplex fluorescence for visualization of spatial distributions of liquid and vapor fuel under firing conditions, planar laser-induced fluorescence (PLIF) with fuel dopants for visualization of liquid fuel, and phase/Doppler particle analysis (P/DPA) to characterize drop size and velocity of the spray. In addition, a new planar droplet sizing technique is developed by imaging exciplex liquid fluorescence and Mie scattering signals simultaneously; the ratio of these signals is proportional to the Sauter mean diameter and the technique can be calibrated using the P/DPA measurements. Computations are performed within the framework of a model for two-phase reacting flows that has been used for comparisons of spray and engine measurements. The results of this work should provide the fundamental basis for design of a successful lean direct-injection spark-injection engine. Such an engine is believed to offer improved fuel economy and reduced emissions, but its development has been hampered by poor understanding of the relationships among fuel injection, mixing, and combustion.