Control of Vortex Breakdown and the Blue Whirl

涡破裂和蓝旋涡的控制

• 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

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.

火旋风是危险的，迅速旋转的火焰，自然产生的野火。当它们发生时，它们可以高达一公里，非常具有破坏性。 火旋风可以举起和抛出燃烧的材料，并产生快速的风，迅速蔓延火灾。然而，在正确的控制实验室条件下，火旋风可以转变成美丽的，良性的，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，无论是气体还是液体形式，同时产生最小的污染物，根本没有烟尘。这种绿色燃烧特性对于燃烧碳氢化合物是最佳的，这使得蓝色漩涡成为真正清洁燃烧能源的潜在来源。然而，要将蓝旋风用于实际应用，还需要了解它的结构、形成方式以及如何控制它。本研究项目旨在了解蓝旋风是如何从火旋风自然演变而来的，以及如何控制它。这些研究的结果将揭示如何绕过危险的火旋风阶段来创造蓝旋风，研究结果将为旋转流的研究提供基础知识，对其它相关系统的研究也有一定的借鉴意义。该研究项目将培养几名早期职业研究人员，包括一名博士后研究员和几名研究生。以前的研究导致发现蓝色漩涡的存在，其火焰结构和一些动力学特性。一个重要的观察结果是，蓝色漩涡是从火漩涡中出现的，火漩涡通过一个称为漩涡破裂的过程变得不稳定，这是一种流体转变，导致各种可能的旋流模式。该研究项目的目标是关注涡破裂过渡，并使用大尺度数值模型来研究是否有可能控制向不同模式的演变。更具体地说，研究人员将考虑几种不同类型的旋流旋涡破裂。一种是在涡破裂区域有局部热变化的旋流。在这里，研究人员希望调查和量化引入涡流分解过程的热量变化如何影响到不同模式的转变。另一种待研究的旋流是化学反应性流，其产生火焰，如蓝色漩涡。研究人员希望找到有关如何控制蓝色漩涡的信息，并使其能够用于发电和燃料泄漏清理。这些研究将提供对其它相关应用中控制涡流破裂所需的系统的基本了解，例如控制大后掠机翼和旋流燃烧室的不稳定性。新的数值算法和物理模型从这个研究项目的发展将增加到一般的计算能力，以模拟低速反应复杂的流system.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

项目成果

Triple flames in swirling flows

旋转流中的三重火焰

• DOI: 10.1016/j.combustflame.2022.112364
• 发表时间: 2022
• 期刊: Combustion and Flame
• 影响因子: 4.4
• 作者: Zhang, Xiao;Chung, Joseph D.;Oran, Elaine S.
• 通讯作者: Oran, Elaine S.