Collaborative Research: Fuel Droplet Disruption under Locally Supersonic Conditions

合作研究：局部超音速条件下的燃料液滴破裂

• 批准号: 0853817
• 负责人: James Hermanson
• 金额: $ 8.5万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0853817&HistoricalAwards=false
• 关键词: Collaborative; Research; Fuel; Droplet; Disruption

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). 0853817/0853396Hermanson/TryggvasonThis preliminary experimental and computational research program will study the physical mechanisms of disruption and vaporization of liquid droplets in supersonic flow. These mechanisms include the deformation of the droplet due to aerodynamic forces, the inertial instability associated with droplet acceleration, and shear instability due to the high-speed flow across the droplet surface. An additional instability can result from the rapid evaporation that can result from the droplet fluid becoming superheated due to the low static pressure in the test section. The action of these mechanisms will be systematically studied by varying both the flow and thermal boundary conditions, including the Mach number relative to the droplet and the liquid composition. The possible existence of optimum combinations of parameters, such as droplet size, vapor pressure, and compressible free-stream conditions for the most rapid droplet disruption and vaporization will be explored. The original and potentially transformative aspects of this research stem from the combination of locally supersonic conditions with potential liquid superheating, which explores a practically important regime of droplet disruption that has not been examined in depth or in a systematic fashion to date. Droplets will be injected into supersonic flow using small-scale supersonic wind tunnels at the University of Washington (UW). A droplet-on-demand generator will produce monodisperse droplets sufficiently small that the droplets will not disrupt too quickly, but sufficiently large so that the droplets will "lag" the supersonic airflow to create compressible conditions relative to the droplet. Different test section geometries will produce droplets with both subsonic and supersonic Mach numbers relative to the surrounding flow. Diagnostic techniques will include planar laser-induced fluorescence (PLIF), spark schlieren/shadowgraph imaging, double-pulsed laser velocity measurement, and direct photography. These techniques will provide detailed knowledge of the droplet deformation/disruption, the dispersion of the expelled vapor, the droplet acceleration, the compressible flow field near the droplet, and the features of the interfacial instabilities. The computational modeling at Worcester Polytechnic Institute (WPI) will employ a finite volume/front-tracking method capable of simulating droplet deformation and explosive evaporation under compressible flow conditions. The simulations will be conducted synergistically with the experiments, using flow information from the experiments to guide the development and implementation of the numerical modeling. In turn, the numerical simulations will serve both to guide the conduct of the experiments as well as to help interpret the experimental results by providing key information not readily accessible by the experiments, such as the pressure variation in the vicinity of the droplets and the rate of vaporization. This research topic has applications to a number of practically important problems involving the injection of liquids in high-speed flows, including supersonic combustion ramjets (scramjets), pulsed detonation engines, re-entry body cooling, and surface erosion in high-speed flows. Such applications are impacted critically by the nature of droplet disruption and vaporization mechanisms of the liquid fuel droplets to be studied. This research will also directly impact education. The planar laser induced fluorescence and pulsed-laser droplet/particle velocity measurement techniques introduced into the undergraduate curriculum through existing experimental methods courses at the UW. Similarly, the numerical work will lead to examples that will be utilized as classroom examples at WPI. Undergraduate students will also participate directly in carrying out the research. The graduate students will actively participate in the undergraduate component of the program by serving, under faculty supervision, in the role of "grant monitor" for the undergraduate component of the research. Lastly, the co-PIs will recruit qualified and interested members of under-represented groups to conduct research at the University of Washington and at Worcester Polytechnic Institute.

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。这个初步的实验和计算研究项目将研究超声速流动中液滴破坏和汽化的物理机制。这些机制包括由于空气动力引起的液滴变形，与液滴加速相关的惯性不稳定性，以及由于高速流过液滴表面而引起的剪切不稳定性。由于测试段中静压较低，液滴流体变得过热，从而导致快速蒸发，从而导致额外的不稳定性。通过改变流动和热边界条件，包括相对于液滴的马赫数和液体成分，将系统地研究这些机制的作用。将探讨是否存在最佳的参数组合，如液滴大小、蒸汽压力和可压缩自由流条件，以实现最快速的液滴破坏和汽化。这项研究的原始和潜在的变革方面源于局部超音速条件与潜在液体过热的结合，它探索了一个实际重要的液滴破坏机制，这一机制迄今尚未得到深入或系统的研究。液滴将通过华盛顿大学的小型超音速风洞注入超音速气流中。按需液滴发生器将产生足够小的单分散液滴，使液滴不会太快破裂，但又足够大，使液滴“滞后”超音速气流，从而形成相对于液滴的可压缩条件。不同的测试截面几何形状将产生相对于周围流动具有亚音速和超音速马赫数的液滴。诊断技术将包括平面激光诱导荧光（PLIF）、火花纹影/阴影成像、双脉冲激光速度测量和直接摄影。这些技术将提供液滴变形/破裂、喷出蒸汽的分散、液滴加速、液滴附近的可压缩流场以及界面不稳定性特征的详细知识。伍斯特理工学院（WPI）的计算建模将采用有限体积/前沿跟踪方法，能够模拟可压缩流动条件下的液滴变形和爆炸蒸发。模拟将与实验协同进行，利用来自实验的流动信息来指导数值模拟的开发和实施。反过来，数值模拟既可以指导实验的进行，也可以通过提供实验中不易获得的关键信息（如液滴附近的压力变化和蒸发速率）来帮助解释实验结果。该研究课题可应用于涉及高速流动中液体喷射的许多实际重要问题，包括超声速燃烧冲压发动机（冲压发动机）、脉冲爆震发动机、再入体冷却和高速流动中的表面侵蚀。这些应用受到液滴破裂的性质和待研究的液体燃料液滴汽化机制的严重影响。这项研究也将直接影响教育。通过威斯康星大学现有的实验方法课程，将平面激光诱导荧光和脉冲激光液滴/粒子速度测量技术引入本科课程。同样，数值工作将导致的例子将被用作WPI的课堂例子。本科生也将直接参与开展研究。研究生将积极参与该项目的本科部分，在教师的监督下，担任本科生研究部分的“拨款监督员”。最后，联合pi将从代表性不足的群体中招募合格和感兴趣的成员，在华盛顿大学和伍斯特理工学院进行研究。