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Outwardly Expanding Premixed Flames in Turbulent Media

湍流介质中向外扩展的预混火焰

基本信息

批准号：
1911530
负责人：
Moshe Matalon
金额：
$ 30万
依托单位：
University of Illinois at Urbana-Champaign
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-01-15 至 2023-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1911530&HistoricalAwards=false
关键词：
Outwardly Expanding Premixed Flames Turbulent

项目摘要

Combustion of fossil fuels remains the primary energy source in power generating plants, vehicle engines, furnaces, and boilers. It is a complex process that involves the inter-diffusion of a large number of chemical species and substantial heat release generated from the chemical reactions. In most applications the burning takes place within a turbulent flow that adds a fluctuating, time-dependent, three-dimensional aspect to the system. The objective of this project is to develop predictive tools that account for the relevant physics and chemistry. The focus is on the evolution of an outwardly expanding flame initiated from a small ignition source. The flame, which appears initially smooth and spherical, becomes highly corrugated due to instabilities inherent to the combustion process and to the turbulence. The increase in flame surface area results in enhanced fuel consumption and propagation speed, a process that may potentially transition to an explosion and/or detonation. Fundamental understanding of the mechanisms responsible for these complex flame properties will improve predictability of combustion systems and increase their safe and efficient operation. The proposed research has also a significant pedagogical value; the advocated physics-based approach will be used in the classroom and in outreach programs intended to extend the human-resources base of science and technology. The complex dynamics of spherically expanding flames resulting from flame instabilities and turbulence will be investigated within the framework of the hydrodynamic theory, derived systematically from the general conservation laws using a multi-scale asymptotic approach. The flame, treated as a surface of density discontinuity, propagates into the fresh mixture in accordance to the procured flame speed relation which, in conjunction with the conditions across the flame front, mimic the influences of diffusion and chemical reaction occurring within the flame zone. The model is free of tuning parameters and ad-hoc sub-grid models that plague commonly used turbulent combustion models. Its numerical implementation uses an embedded manifold approach, wherein the flame surface is represented implicitly as the zeroth level set of a scalar field. Since the flame surface is determined unambiguously, all pertinent information to its propagation will be directly contained in the flame topology and in the flow field at the same location. The acquired knowledge on flame instabilities and flame-turbulence interactions will serve to guide the experimental studies in this area and improve large-scale computational efforts, by replacing ad-hoc lumped parameters with prototypical flame configurations that are fundamentally sound and based on physical first principles.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.

化石燃料的燃烧仍然是发电厂、车辆发动机、熔炉和锅炉中的主要能源。这是一个复杂的过程，涉及大量化学物质的相互扩散和化学反应产生的大量热释放。在大多数应用中，燃烧发生在湍流内，这给系统增加了波动的、依赖于时间的三维方面。该项目的目标是开发预测工具，解释相关的物理和化学。重点是从一个小的点火源开始向外扩展的火焰的演变。火焰最初看起来是光滑的球形，由于燃烧过程和湍流固有的不稳定性而变得高度波纹化。火焰表面积的增加导致燃料消耗和传播速度增加，这是一个可能转变为爆炸和/或爆震的过程。对这些复杂火焰特性的机理的基本理解将提高燃烧系统的可预测性，并增加其安全和有效的操作。拟议的研究也有重要的教学价值;倡导的基于物理的方法将用于课堂和旨在扩大科学和技术的人力资源基础的推广计划。火焰不稳定性和湍流引起的球形膨胀火焰的复杂动力学将在流体动力学理论的框架内进行研究，该理论使用多尺度渐近方法从一般守恒定律系统地导出。被视为密度不连续表面的火焰，根据所获得的火焰速度关系传播到新鲜混合物中，该火焰速度关系与火焰前缘的条件相结合，模仿火焰区内发生的扩散和化学反应的影响。该模型是免费的调整参数和ad-hoc子网格模型，困扰常用的湍流燃烧模型。它的数值实现使用嵌入式流形方法，其中火焰表面被隐式地表示为标量场的第零水平集。由于火焰表面是明确确定的，所有相关的信息，其传播将直接包含在火焰拓扑结构和流场在同一位置。获得的关于火焰不稳定性和火焰-湍流相互作用的知识将用于指导这一领域的实验研究，并改进大规模计算工作，用AD代替AD，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。