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

0854174方这个奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。这项研究是在研究可变几何喷雾(VGS)的科学，特别是它对压燃式发动机燃油喷射的燃烧效率和污染物产生的影响。研究的核心是一种基于实验室的新型喷油器，设计用于在整个喷油过程中独立控制燃油喷雾锥角和燃油流速。这项技术将使详细研究喷雾几何形状对混合和燃烧过程的影响成为可能。目前，这样的研究将需要使用几个固定的喷油器，并将限于那些容易获得的几何形状。动态注水剖面的研究目前只能在模拟中进行。通过优化活塞缸内的燃料分配，未燃烧的碳氢化合物将显著减少，新的燃烧模式，如HCCI燃烧，将成为可能的更广泛的运行模式。将使用一个原型喷油器来研究喷雾锥角变化对空气-燃料混合、点火、燃烧和污染物形成的影响。该喷嘴的特点是在一个特殊形状的喷嘴内有一个可移动的针头，产生一个中空锥体喷雾，喷雾角度变化很大(70到160度)，在整个注射过程中平稳变化。喷雾和燃烧测试将在光学接近的恒容燃烧室中进行。该燃烧室将提供真实的压燃式发动机燃烧条件，并将使用最先进的仪器来测量混合气中的混合、NOx、烟尘和其他污染物种类。激光衍射技术将被用来测量瞬时燃料液滴的尺寸，而阴影和米氏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捉点火和燃烧火焰的结构。采用双色测温法对烟尘浓度和火焰温度分布进行定量测量。将使用排放分析仪和气相色谱-质谱仪系统来分析产品种类，特别是污染物排放。这项研究将展示与固定几何喷雾相比，可变几何喷雾在增强空气-燃料混合方面的有效性，以及改进后的混合对点火、燃烧和燃烧产物的影响。拟议的研究还将创造一个跨学科的合作，并进一步促进研究生和本科生的教育发展。由于激发公众对研究的兴趣对于招聘下一代工程师和科学家至关重要，喷油器技术将成为北卡罗来纳州立大学(NCSU)中学工程夏令营的一项特色技术。每年夏天，该计划邀请60名中学生花一周时间参加有趣的、以探究为基础的活动，以加强科学和工程概念的应用和解决问题。

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.