Computational investigation of thermo-diffusive instabilities in flames: from laminar cellular structures to turbulent flows

不稳定火焰的传播是许多自然现象和工程应用的中心。了解和模拟这些不稳定的火焰以及它们如何与湍流相互作用，对于设计高效和清洁的能源转换设备，减轻意外爆炸的风险以及了解天体物理现象至关重要。 本工作是进行计算研究，以揭示一个完整的图片的几何形状的近极限预混火焰前锋。虽然主要关注的是热扩散不稳定火焰，但预计结果将揭示许多其他科学问题。这项工作将导致高保真度的计算模型的发展，这将用于设计和优化高性能的燃烧系统的推进application.Experimental观察和理论研究长期指出层流稳定火焰和热扩散不稳定火焰之间的差异。不幸的是，国家的最先进的技术，目前用于模拟大规模的湍流火焰不能充分预测的流场反应的混合物，本质上是不稳定的。这项工作是量化的基本特征，使不稳定的火焰不同于他们的稳定的同行：细胞结构的大小和火焰传播的加速。这两个特征构成了任何大涡模拟（LES）模型的基础：它们决定了LES过滤器的大小并控制了化学源项的闭合。该建议的强度依赖于考虑从一维球形火焰到二维固定管状火焰到三维不稳定层流和湍流火焰的广泛条件。在整个分析过程中，不会采取任何精确度的捷径，并且将重新访问并包括（如有必要）以前被忽略的效应（如Soret/Dufour）。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进行评估，被认为值得支持。

The propagation of unstable flames is at the center of numerous natural phenomena and engineering applications. Understanding and modeling these unstable flames and how they interact with turbulent flows are of critical importance to designing efficient and clean energy conversion devices, mitigating the risks of accidental explosions, and understanding astrophysical phenomena. This work is to conduct a computational study to reveal a complete picture of the geometry of the near-limit premixed flame front. While the primary focus is on thermo-diffusively unstable flames, the results are expected to shed light onto numerous additional scientific problems. This work will lead to the development of high-fidelity computational models, which will be used for designing and optimizing high-performance combustion systems for propulsion application.Experimental observations and theoretical studies have long pointed out the differences between laminar stable flames and thermo-diffusively unstable flames. Unfortunately, state-of-the-art techniques currently used to simulate large-scale turbulent flames fail to adequately predict the flow field of reacting mixtures that are intrinsically unstable. This work is to quantify the fundamental characteristics that make unstable flames different from their stable counterparts: the size of the cellular structure and the acceleration of the flame front propagation. These two features form the foundation onto which any Large Eddy Simulation (LES) models will be built: they determine the size of the LES filter and control the closure of the chemical source terms. The strength of the proposal relies on considering an extensive range of conditions from 1D spherical flames, to 2D stationary tubular flames, to 3D unstable laminar and turbulent flames. Throughout the analysis, no shortcut of accuracy will be taken, and previously neglected effects (such as Soret/Dufour) will be revisited and included (if necessary). The outcome will be a complete picture of the geometry of the reaction zone, and the proposed work will have important impacts on many natural phenomena and engineering applications: from energy generation to safety to astrophysics.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.