Experimental study of local extinction in laminar and turbulent flames

在许多实际的燃烧器中，热量通过化学反应在相对薄的火焰片中释放。 燃烧室中燃料和空气流的湍流导致速度波动，这扰动火焰片并增加热量从火焰传递出去。 当这些波动足够大时，与火焰释放的热量相比，热损失可能太高，导致局部熄灭。 局部熄灭事件在火焰片上留下一个洞，这可能导致火焰完全熄灭。 在许多应用中，熄灭是对燃烧器的操作的显著限制，而在其它应用中，熄灭可被期望以熄灭火焰。 无论哪种情况，都需要对导致灭绝的机制有物理上的理解。 该项目旨在从根本上了解导致局部熄灭的速度和火焰片的相互作用，从而可以生成更准确的火焰极限和火焰孔响应模型。 这项工作的智力价值集中在详细了解湍流火焰中的速度波动对火焰片传热的影响，以及这些变化对火焰化学热释放的影响。 该实验和计算项目将利用一个光学可访问的燃烧器，该燃烧器被设计用于在火焰片中产生局部熄灭，从而能够使用激光诊断进行详细研究。 这些测量结果将用于开发描述灭绝的模型，这些模型可能对工业设计工具产生更广泛的影响。 这项研究将涉及研究生和本科生的参与，他们将接受基础燃烧理论和光学测量应用方面的培训。

1336184RenfroIn many practical combustors, heat is released by chemical reactions in relatively thin flame sheets. Turbulence in the flow of fuel and air in the combustor lead to fluctuations in velocity that perturb the flame sheet and increase the transfer of heat away from the flame. When these fluctuations are sufficiently large, the heat loss can be too high compared to the heat released by the flame resulting in local extinction. A local extinction event leaves a hole in the flame sheet that can lead to complete extinction of the flame. In many applications extinction is a significant limitation to the operation of the combustor, while in other applications extinction can be desired to quench a flame. In either case, physical understandings of the mechanisms that cause extinction are needed. This project seeks a fundamental understanding of the interactions of velocity and flame sheets that cause local extinction such that more accurate models of flame limits and the response of flame holes can be generated. The intellectual merit of the work focuses on a detailed understanding of the impact that velocity fluctuations in turbulent flames have on heat transfer from flames sheets as well as the impact of these changes to the flame's chemical heat release. The experimental and computational project will utilize an optically-accessible combustor that has been designed to create local extinction in a flame sheet enabling a detailed study using laser diagnostics. The measurements will be used to develop models describing extinction that can have broader impact on industrial design tools. The research will involve the participation of graduate and undergraduate students, who will be trained in fundamental combustion theory and application of optical measurements.