Control of Vortex Breakdown and the Blue Whirl

涡破裂和蓝旋涡的控制

基本信息

批准号：
2050771
负责人：
Elaine Oran
金额：
$ 42万
依托单位：
Texas A&M Engineering Experiment Station
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2050771&HistoricalAwards=false
关键词：
Control Vortex Breakdown Blue Whirl

项目摘要

Fire whirls are dangerous, rapidly whirling flames that arise naturally in wildfires. When they do occur, they can be up to a kilometer tall and very destructive. Fire whirls can lift and throw burning material and generate fast winds that quickly spread the fire. Under the right controlled laboratory conditions, however, a fire whirl can transition into a beautiful, benign, small, blue flame called a blue whirl. These blue whirls can burn many different types of hydrocarbon fuels, either in gaseous or liquid form, while producing minimal pollutants and no soot at all. Such green-combustion properties are optimal for burning hydrocarbons, which make blue whirls a potential source of truly clean combustion energy. To use the blue whirl for practical applications, though, more needs to be understood about its structure, how it forms, and how to control it. This research project aims to understand how the blue whirl evolves naturally from a fire whirl and how to control it. The results of these investigations should reveal how to bypass the dangerous fire-whirl stage for creating the blue whirl, and the research should provide fundamental knowledge about swirling flows, which would benefit other related systems. This research project will train several early-career researchers, including a postdoctoral researcher and several graduate students.Previous studies led to the discovery of the existence of the blue whirl, its flame structure, and some of its dynamic properties. An important observation was that the blue whirl emerges from a fire whirl that goes unstable through a process known as vortex breakdown, which is a fluid transition leading to various possible modes of swirling flow. The objective of this research project is to focus on the vortex-breakdown transition and use large-scale numerical models to investigate whether it is possible to control the evolution to different modes. More specifically, the researchers will consider several different types of swirling flows subject to vortex breakdown. One type is a swirling flow with localized heat changes in the region of vortex breakdown. Here, the researchers hope to investigate and quantify how heat changes introduced into the vortex-breakdown process affect the transition to different modes. Another type of swirling flow to be investigated is a chemically reactive flow that produces flames such as the blue whirl. The researchers anticipate finding information on how to control the blue whirl and to enable its use for power generation and fuel spill clean-up. These studies will provide a fundamental understanding of the system that is needed to control vortex breakdown in other related applications, such as controlling instability on highly swept wings and swirl combustors. The new numerical algorithms and physical models developed from this research project will add to the general computational ability to simulate low-speed reactive complex flow systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

火旋风是野火中自然产生的危险的、快速旋转的火焰。当它们确实发生时，它们的高度可达一公里并且极具破坏性。火旋风可以举起和抛掷燃烧的物质，并产生快速的风，使火迅速蔓延。然而，在适当控制的实验室条件下，火旋风可以转变为美丽、良性、小的蓝色火焰，称为蓝色旋风。这些蓝色漩涡可以燃烧许多不同类型的碳氢化合物燃料，无论是气态还是液态，同时产生的污染物极少，而且根本不产生烟灰。这种绿色燃烧特性非常适合燃烧碳氢化合物，这使得蓝色漩涡成为真正清洁燃烧能源的潜在来源。然而，要将蓝色漩涡用于实际应用，需要更多地了解它的结构、它是如何形成的以及如何控制它。该研究项目旨在了解蓝色旋风如何从火旋风自然演变以及如何控制它。这些研究的结果应该揭示如何绕过危险的火旋风阶段来产生蓝色旋风，并且研究应该提供有关旋流的基础知识，这将有利于其他相关系统。该研究项目将培养几名处于职业生涯早期的研究人员，包括一名博士后研究员和几名研究生。之前的研究导致发现了蓝色旋涡的存在、它的火焰结构以及它的一些动态特性。一个重要的观察结果是，蓝色涡流是从火涡流中产生的，火涡流通过称为涡流破裂的过程变得不稳定，这是一种导致各种可能的旋流模式的流体过渡。该研究项目的目标是关注涡破裂转变，并使用大型数值模型来研究是否有可能控制不同模式的演化。更具体地说，研究人员将考虑几种不同类型的易受涡流破坏的旋流。一种类型是在涡流破坏区域中具有局部热量变化的旋流。在这里，研究人员希望调查并量化涡流分解过程中引入的热量变化如何影响向不同模式的过渡。要研究的另一种类型的旋流是化学反应流，它会产生火焰，例如蓝色旋涡。研究人员预计会找到有关如何控制蓝色涡流并将其用于发电和燃料泄漏清理的信息。这些研究将为控制其他相关应用中的涡流破坏所需的系统提供基本的了解，例如控制大后掠翼和涡流燃烧室的不稳定性。该研究项目开发的新数值算法和物理模型将增强模拟低速反应复杂流动系统的通用计算能力。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优势和评估进行评估，被认为值得支持。更广泛的影响审查标准。