Variable Geometry Spray Fuel Injection: Investigating its Effects on Combustion Efficiency and Emissions

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本研究旨在研究可变几何喷雾器（VGS）的科学，特别是它对压缩点火发动机燃油喷射的燃烧效率和污染物产生的影响。该研究的核心是一种新型的实验室喷油器，该喷油器设计用于在整个喷射过程中独立控制燃油喷射锥角和燃油流量。这项技术将能够详细研究喷雾几何形状对混合和燃烧过程的影响。目前，这样的研究将需要使用几个固定的燃料喷射器，并且将限于那些易于获得的几何形状。动态注入剖面的研究目前只能在模拟中进行。通过优化活塞碗内的燃料分配，未燃烧的碳氢化合物将大大减少，新的燃烧模式，如HCCI燃烧，将有可能在更广泛的操作系统中使用。原型喷油器将用于研究喷嘴锥角变化对空气-燃料混合、点火、燃烧和污染物形成的影响。该喷射器的特点是在一个特殊形状的喷嘴内有一个可移动的针，在整个喷射过程中，喷射角（70到160度）变化很大，可以产生一个空心锥形喷雾。喷雾和燃烧测试将在光学可及的等体积燃烧室中进行。该燃烧室将提供真实的压燃发动机燃烧条件，并将使用最先进的仪器来测量混合物、氮氧化物、烟尘和混合物中的其他污染物。激光衍射技术将用于测量瞬态燃料液滴的大小，而阴影图和米散射图像将显示燃烧室中液体和气体燃料的分布。自然火焰光度成像将用于捕获点火和燃烧火焰结构。采用双色高温法定量测量烟尘浓度和火焰温度分布。排放分析仪和气相色谱-质谱联用系统将用于分析产品种类，特别是污染物排放。这些研究将证明可变几何喷嘴对空气-燃料混合增强的有效性，以及与固定几何喷嘴相比，改进后的混合对点火、燃烧和燃烧产物的影响。建议的研究也将创造一个跨学科的合作，并进一步发展研究生和本科生的教育。由于激发公众对研究的兴趣对于招募下一代工程师和科学家至关重要，因此喷油器技术将成为北卡罗莱纳州立大学（NCSU）中学工程营的特色技术。每年夏天，该项目邀请60名中学生花一周的时间参加有趣的探究性活动，加强科学和工程概念的应用和解决问题的能力。

0854174Fang This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This research is studying the science of variable-geometry sprays (VGS), specifically as it affects combustion efficiency and pollutant production in fuel injection for compression-ignition engines. At the heart of the study is a novel laboratory-based injector designed to control the fuel spray cone angle and the fuel flow rate independently throughout the injection process. This technology will enable detailed studies of the effects of spray geometry on the mixing and combustion processes. At present, such a study would require the use of several fixed fuel injectors, and would be limited to those geometries that are readily available. Studies of dynamic injection profiles are currently only possible in simulation. By optimizing the fuel distribution within the piston bowl, unburned hydrocarbons will be significantly reduced, and new combustion modes such as HCCI combustion will become possible for broader operating regimes. A prototype injector will be used to study the effects of the spray-cone angle variation on air-fuel mixing, ignition, combustion, and pollutant formation. The injector features a movable pintle inside a specially shaped nozzle, producing a hollow-cone spray with a wide variation in spray angle (70 to 160 degrees) smoothly variable throughout the injection process. Spray and combustion tests will be conducted in an optically accessible, constant-volume combustion chamber. This chamber will provide realistic compression-ignition engine combustion conditions and will use state-of-the-art instrumentation to measure mixing, NOx, soot, and other pollutant species in the mixture. Laser diffraction techniques will be used to measure transient fuel droplet size, while shadowgraph and Mie-scattering images will show the distribution of liquid and gaseous fuel in the chamber. Natural flame luminosity imaging will be used to capture the ignition and combustion flame structure. Two-color pyrometry will be adopted to quantitatively measure the soot concentration and flame temperature distributions. An emission analyzer and a Gas Chromatograph-Mass Spectrometer system will be used to analyze the product species, particularly, the pollutant emissions. The studies will demonstrate the effectiveness of variable geometry sprays on air-fuel mixing enhancement, and the effect of the improved mixing on ignition, combustion and combustion products as compared to fixed geometry sprays.The proposed research will also create an interdisciplinary collaboration and further the educational development of graduate and undergraduate students. Because generating public interest in research is critical to recruiting the next generation of engineers and scientists, the injector technology will be a featured technology of the North Carolina State University (NCSU) Middle School Engineering Camp. Each summer, this program invites 60 middle-school students to spend a week participating in fun, inquiry-based activities that reinforce the application of science and engineering concepts and problem solving.