CAREER: Droplet Vaporization under Asymmetric Conditions: Implications for Combustion at Conventional and Reduced Scales

职业：不对称条件下的液滴蒸发：对常规规模和缩小规模燃烧的影响

• 批准号: 0346297
• 负责人: Herek Clack
• 金额: --
• 依托单位: Illinois Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-15 至 2010-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0346297&HistoricalAwards=false
• 关键词: CAREER; Droplet; Vaporization; under; Asymmetric

The primary objective of this CAREER project is to assess the impact of asymmetrical convective and thermal conditions on the fuel-vapor distributions and ignition characteristics of vaporizing liquid-fuel droplets. The experimental methodology exposes monodisperse acetone droplet streams to thermally and convectively asymmetric flow conditions. Two separate flow reactors, a heated linear plug-flow reactor (LPFR) and a heated circular Couette-flow reactor (CCFR), provide thermally asymmetric (LPFR), convectively asymmetric (CCFR), and combined thermal/convective asymmetric (CCFR) environments for observation of vaporization of acetone droplets. An Nd-YAG laser sheet illuminates the vaporizing droplet streams, causing the acetone vapor to fluoresce. An intensified CCD camera captures the fluorescence images. Analysis of these images reveals the degree to which asymmetric thermofluid conditions induce nonuniform fuel-vapor distributions, which in turn can impact adversely droplet ignition, combustion, and pollutant formation. By comparing the effects of thermal, convective, and combined thermal/convective asymmetric conditions, individual and collective effects can be exposed, thus providing the basis for extending classical droplet vaporization theory to include nonuniform environments. A separate, concurrent numerical modeling effort is being developed to simulate observed anomalous vaporization behavior and to validate new vaporization models using parallel processing architectures and micro-scale transport formulations.As emission regulations become ever more restrictive for traditional combustion devices, environmental compliance may depend increasingly on understanding higher-order effects, such as asymmetric droplet vaporization phenomena. Further, asymmetric droplet vaporization phenomena may play a dominant role in combustion processes within miniature (~ 1 mm) combustors, an emerging technology being developed to provide power for portable electronics, remote sensors, and remotely piloted vehicles. Such miniature combustors require liquid fuels in order to allow the long refueling intervals needed to compete with electric batteries. However, miniaturization increases the size of liquid fuel droplets relative to the combustor dimensions and produces stronger and more prominent thermofluid property gradients within the combustor itself. Thus, successful miniaturization of combustors depends on identifying and understanding anomalous combustion phenomena that are nearly insignificant at conventional scales but which predominate at these reduced scales.The educational component of this CAREER project uses vertically integrated teams ("Engineering Collectives" or ECs) of high school, undergraduate, and graduate students to embark upon guided science and engineering discovery projects. High school students are recruited from the neighborhoods surrounding the IIT campus, which are predominantly African-American and Latino, thereby helping to broaden the participation of underrepresented groups in science and engineering and their representation on the IIT campus.

该CAREER项目的主要目标是评估不对称对流和热条件对汽化液体燃料液滴的燃料-蒸汽分布和点火特性的影响。 实验方法暴露单分散丙酮液滴流的热和对流不对称的流动条件。 两个独立的流动反应器，加热的线性活塞流反应器（LPFR）和加热的圆形Couette流反应器（CCFR），提供热不对称（LPFR），对流不对称（CCFR），和组合的热/对流不对称（CCFR）的环境，用于观察丙酮液滴的蒸发。Nd-YAG激光片照射蒸发的液滴流，使丙酮蒸气发出荧光。 增强的CCD相机捕获荧光图像。 对这些图像的分析揭示了不对称热流体条件引起不均匀燃料蒸气分布的程度，这反过来又会对液滴点火、燃烧和污染物形成产生不利影响。 通过比较热，对流，和组合的热/对流不对称条件的影响，个人和集体的影响可以暴露，从而提供了扩展经典的液滴蒸发理论，包括不均匀的环境的基础。 一个单独的，并发的数值模拟工作正在开发，以模拟观察到的异常汽化行为，并验证新的汽化模型，使用并行处理架构和微尺度的传输formulations.As排放法规变得越来越严格的传统燃烧装置，环境合规性可能越来越依赖于了解高阶效应，如不对称液滴汽化现象。 此外，不对称液滴蒸发现象可能在微型（~ 1 mm）燃烧室的燃烧过程中起主导作用，这是一种正在开发的为便携式电子设备、遥感器和遥控飞行器提供动力的新兴技术。 这种微型燃烧室需要液体燃料，以便允许与电池竞争所需的长加油间隔。 然而，小型化增加了液体燃料液滴相对于燃烧室尺寸的尺寸，并在燃烧室本身内产生更强和更显著的热流体性质梯度。 因此，成功的小型化的燃烧室取决于识别和理解异常燃烧现象，几乎是微不足道的，在传统的规模，但占主导地位，在这些减少scales.The教育的CAREER项目的组成部分使用垂直整合的团队（“工程集体”或EC）的高中，本科生和研究生开始指导科学和工程发现项目。 高中生从IIT校园周围的社区招募，这些社区主要是非洲裔美国人和拉丁裔，从而有助于扩大代表性不足的群体在科学和工程领域的参与，以及他们在IIT校园的代表性。