Experimental and Numerical Investigation of the Mechanisms of Local Extinction Using Flame Kernel-Vortex Interactions

项目摘要本研究的目的是调查，实验和计算，局部熄灭过程中发生的预混火焰使用一种新的火焰核涡配置。 核-涡相互作用提供了丰富的配置来研究至少两种导致熄灭的重要机制：火焰流场拓扑结构（曲率和应变）;和火焰-火焰相互作用（或相互火焰湮灭过程）。 在相同的相互作用中，可以同时产生正和负的不稳定应变率和曲率的条件，为比较火焰对不同类型的火焰拉伸的响应提供理想条件。 此外，膨胀核的相对大小的涡的结果在一个不断变化的贡献，火焰湍流和平流的核心演变过程中。 这两个互补的（实验和计算）的方法进行协调，以提供更好的理解的火焰和流场拓扑结构（主要是不稳定的应变和曲率效应）和相互火焰湮灭对局部火焰熄灭的作用，并确定实验观测，测量预混碳氢化合物火焰中的局部燃烧强度。 本文的主要工作和技术价值体现在以下三个方面：（1）火焰核-涡相互作用熄火过程的实验研究。 这项研究依赖于广泛的实验条件，跨越不同的火焰和涡流强度。 同时测量的中间物种，温度和速度提供了一个更强大的火焰和流场拓扑结构和局部火焰响应之间的联系;（2）一般结构的数值研究，以及在火焰内核中的两个重要区域的结构，受到淬火不稳定应变或相互火焰湮灭。 数值研究用于确定相关的实验条件，并探索，使用详细的化学，灭绝过程中涉及的化学机制。 详细的化学模拟的初始条件由所选择的实验条件提供;和（3）组合的方法提供补充信息，以确定局部灭绝的条件和机制。 一个同样重要的奋进是使用模拟，以确定候选人的实验观测值，可用于量化燃烧强度的碳氢化合物预混火焰的不稳定和extinction conditions.Broader impactThe内核涡提供了一个现实的和有利的配置，以开发模型的火焰熄灭，这将是有价值的，我们的理解湍流火焰一般和湍流内核具体，例如在火花点火内燃机和其它实际燃烧装置中观察到的那些。 所提出的方法可以有一个广泛的影响，在燃烧科学和相关领域的研究，无论是计算或实验方法本身不能充分解释的意见类似的问题。 协调实验计算方法的范例提供了独特的机会，为研究生的教育，在这两种方法的项目要求。

Project SummaryThe objective of this research is to investigate, both experimentally and computationally, the local extinction processes occurring in premixed flames using a novel flame kernel-vortex configuration. The kernel-vortex interaction provides a rich configuration to study at least two important mechanisms responsible for extinction: flame-flow field topologies (curvature and strain); and flame-flame interactions (or mutual flame annihilation processes). Conditions of positive and negative unsteady strain rate and curvature may be generated simultaneously within the same interaction, providing the ideal condition for comparing the flame's response to different types of flame stretch. Moreover, the relative size of the expanding kernel to the vortex results in an evolving contribution of the vortex to flame wrinkling and its advection during the kernel evolution. The two complementary (experimental and computational) approaches are coordinated to provide improved understanding of the role of flame and flow field topologies (mainly unsteady strain and curvature effects) and mutual flame annihilations on local flame extinction, and to identify experimental observables that measure the local burning intensity in premixed hydrocarbon flames. Three important elements represent the main thrusts of thework and its technical merit: (1) An experimental study of extinction processes during flame kernel-vortex interactions. The study relies on a broad range of experimental conditions that span different flame and vortex strengths. Simultaneous measurements of intermediate species, temperature, and velocity provide a more robust link between flame and flow-field topologies and the local flame response; (2) Numerical studies of the general structure as well as the structure of two important regions in the flame kernels that are subject to quenching by unsteady strain or mutual flame annihilation. The numerical studies are used to identify relevant experimental conditions and explore, using detailed chemistry, the chemical mechanisms involved during extinction. Initial conditions for the detailed chemistry simulations are provided by the selected experimental conditions; and (3) The combined approaches provide complementary information to identify conditions and mechanisms for local extinction. An equally important endeavor is to use the simulations to identify candidate experimental observables that may be used to quantify the burning intensity of hydrocarbon premixed flames for unsteady and extinction conditions.Broader impactThe kernel-vortex offers a realistic and advantageous configuration to develop models for flame extinction that will be of value to our understanding of turbulent flames in general and turbulent kernels specifically, such as those observed in spark-ignited internal combustion engines and other practical combustion devices. The methodology proposed can have a broad impact on similar problems in combustion science and related areas of research where neither computational nor experimental approaches alone can adequately explain observations. The paradigm of coordinated experimental-computational approaches provides unique opportunities for the education of graduate students in both approaches as the project requires.