Flames, Flows and Their Interactions

在某些条件下，层流火焰可能是固有的不稳定的，导致结构起皱或波纹。显然，不稳定的一般特征与基本的流体流动密切相关，并在一定程度上远离火焰锋面的热量传递。分层混合物存在于许多燃烧环境中，形成弯曲的、可能不稳定传播的火焰锋面。所提出的研究旨在从根本上理解层流预混火焰的行为和对流场中这种不均匀的响应。还将研究液滴的汽化和燃烧。所使用的技术是渐近法和摄动法，辅之以数值计算，并将结果与观察到的物理现象进行比较。一个人对像发动机和熔炉这样的复杂系统中的燃烧行为的了解，往往通过一个描述简单得多的分析模型来加强，该模型分离出一个或两个控制物理参数。这项理论研究将尝试将渐近和摄动技术应用于非均匀混合物中传播的预混火焰，目的是深入了解应变率、火焰前沿曲率、涡度、质量扩散、以及传热对火焰稳定性的影响。

Laminar flames can, under certain conditions, be inherently unstable, leading to wrinkled or corrugated structures. It is clear that the general character of the instability is intimately tied to the underlying fluid flow and by the extent of heat transfer away from the flame front. Stratified mixtures exist in many combustion environments, creating a curved and possibly unsteady propagating flame front. The proposed research is directed towards a fundamental understanding of the behavior and response of a laminar, premixed flame to such non-uniformities in the flow field. Droplet vaporization and combustion will also be investigated. The techniques to be used are the asymptotic and perturbation methods supplemented by numerical calculations, with the results compared to observed physical phenomena. One's understanding of the behavior of combustion in systems as complex as engines and furnaces is often enhanced by an analytical model of a much simplified description which isolates one or two controlling physical parameters. This theoretical study will attempt to stretch the application of asymptotic and perturbation techniques to premixed flames propagating in non-uniform mixtures, with the objective of gaining insight into the effects of strain rate, flame front curvature, vorticity, mass diffusion, and heat transfer on the flame stability.