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，炉子和锅炉的主要能源。这是一个复杂的过程，涉及大量化学物种的相互扩散以及化学反应产生的大量热量释放。在大多数应用中，燃烧发生在湍流中，从而为系统增加了波动，时间依赖的三维方面。该项目的目的是开发说明相关物理和化学的预测工具。重点是从小点火源引发的向外扩展的火焰的演变。由于燃烧过程和湍流固有的不稳定性，该火焰似乎最初是光滑和球形的，因此变得高度波纹。火焰表面积的增加导致燃料消耗和传播速度提高，该过程可能会过渡到爆炸和/或爆炸。对负责这些复杂火焰特性的机制的基本了解将提高燃烧系统的可预测性并提高其安全有效的操作。拟议的研究也具有重要的教学价值。基于物理学的方法将用于课堂和外展计划，以扩展科学和技术的人力资源基础。将在流体动力学理论的框架内研究由火焰不稳定性和湍流产生的球形扩展火焰的复杂动力学，并使用多规模的渐近方法从一般的保护法中系统地得出。该火焰被视为密度不连续性的表面，根据所采购的火焰速度关系传播到新鲜混合物中，这些速度关系与火焰前面的条件结合使用，模仿了火焰区域内发生的扩散和化学反应的影响。该模型没有调整参数和临时的子网格模型，这些模型困扰着常用的湍流燃烧模型。它的数值实现使用嵌入式歧管方法，其中，火焰表面被隐式表示为标量场的零级集。由于明确确定了火焰表面，因此与其传播的所有相关信息都将直接包含在火焰拓扑中，在同一位置的流场中。关于火焰不稳定性和火焰扰动相互作用的知识将有助于指导该领域的实验研究并改善大规模的计算工作，通过更换原型的火焰配置，从根本上讲是合理的，并且基于物理上的原理，这些奖项通过NSF的智力依据，其智力均具有良好的效果，从而取代了原型的火焰构型，从根本上讲是合理的。标准。