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

本文是对稀薄直喷发动机中燃油喷雾混合和燃烧相互作用的研究。先进的光学诊断和多维建模被用于表征缸内燃料/空气混合和在光学可接近的直接喷射发动机中的燃烧。光学诊断包括用于显示燃烧条件下液体和蒸汽燃料的空间分布的激基复合体荧光，用于显示液体燃料的燃料掺杂的平面激光诱导荧光(PLIF)，以及用于表征喷雾液滴大小和速度的相位/多普勒粒子分析(P/DPA)。此外，通过同时成像激基复合体液体荧光和Mie散射信号，发展了一种新的平面液滴测量技术，这些信号的比例与Sauter平均直径成正比，该技术可以利用P/DPA测量进行校准。计算是在两相反应流模型的框架内进行的，该模型已用于喷雾和发动机测量的比较。研究结果为稀薄直喷火花喷射发动机的设计提供了基本依据。这种发动机被认为可以提供更好的燃油经济性和减少排放，但由于对燃油喷射、混合和燃烧之间的关系认识不足，它的发展一直受到阻碍。

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.