Multiscalar Measurements in Supersonic Flames

0933633Karpetis该奖项是根据2009年美国复苏和再投资法案（公法111 - 5）资助的。当查克·耶格尔在1947年首次超音速飞行时打破了音障，当时实现这种努力的关键技术与空气动力学设计和材料强度有关。在过去的几十年里，与推进所必需的燃烧过程有关的一种更为隐蔽的音障，对飞机速度施加了实际的限制。具体地，通过发动机的流动可能变得足够快以与完全燃烧所必须发生的化学反应竞争，从而导致抑制并且最终熄灭甚至最快的火焰。该奖项的研究工作主张采用实验和理论相结合的方法来研究航空航天推进的高速火焰。其目标是促进对超音速燃烧的基本理解，并最终实现在未来几十年新的商用高超音速飞机起飞之前必须到位的技术。将解决的主要问题是在极端条件下操作的湍流可压缩火焰中的流体动力学和化学之间的相互作用。本工作的中心假设是高马赫数及其引起的相关压力变化对火焰抑制和熄灭的重要性。线成像光谱的旋转和振动的拉曼散射将允许完整的本地热化学测量，该技术是能够测量压力，温度，和所有主要物种沿着线的激光在一个单一的拍摄方式在超音速火焰。线成像实验还将产生两个导出量的有价值的信息：守恒标量和标量耗散率。第一个是非常宝贵的火焰结构的检查，而第二个作为最好的可用测量的局部特征时间尺度的流场。这两个派生的数量将在这项研究中使用的火焰抑制和最终熄灭高马赫数火焰。空间和标量超音速火焰结构将在"正则"构型中进行研究，这些构型设计成最大化流动-化学相互作用效应。对超音速条件下流体力学和化学之间相互作用的基本理解是关键的预期结果，并且这项工作的实验结果将证明对模型开发以及计算比较有价值。湍流火焰中的流动化学相互作用的研究，表现出压力变化有很大的意义，从喷气发动机燃烧室和加力燃烧室，脉冲爆震发动机和火箭排气的航空航天推进应用的广泛范围。此外，研究生和本科生将通过参与涉及激光诊断和超音速火焰的尖端研究来学习。与该小组合作的学生还将受益于夏季访问桑迪亚国家实验室和参加会议和研讨会。PI还将开发关于光学和物理问题的实用实验教育模块，供9 - 12年级使用。这些模块涉及光学和物理学的基本问题，并与拟议工作的研究方面密切相关。代表性不足的团体的成员将参与外联和研究计划

0933633KarpetisThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).When Chuck Yeager broke the sound barrier with the first supersonic flight in 1947, the crucial technologies of the day that enabled such an endeavor were associated with aerodynamic design and strength of materials. During the last few decades a more insidious sound barrier, associated with the combustion process necessary for propulsion, has imposed practical limits on aircraft speeds. Specifically, flow through the engine may become fast enough to compete with the chemistry that must take place for complete combustion, resulting in suppression and, ultimately, extinction of even the fastest flame. The research work in this award advocates a combined experimental and theoretical approach to the study of high-speed flames for aerospace propulsion. Its objective is to contribute to the fundamental understanding of supersonic combustion and ultimately to enable the technology that must be in place before new, commercial hypersonic aircraft can take flight in the coming decades. The main issue that will be addressed is the interaction between fluid dynamics and chemistry in turbulent compressible flames operating at extreme conditions. The central hypothesis of the present work is the importance of high Mach number and the associated pressure variation it induces onto flame suppression and extinction. Line-imaging spectroscopy of the rotational and vibrational Raman scattering will allow for complete measurements of local thermochemistry; the technique is capable of measuring pressure, temperature, and all major species along the line of the laser in a single-shot fashion within supersonic flames. The line-imaging experiments will also yield valuable information of two derived quantities: conserved scalar and scalar dissipation rate. The first is invaluable in the examination of flame structure, while the second serves as the best available measurement of the local characteristic timescale of the flow field. Both derived quantities will be used in this study to examine the flame suppression and eventual extinction in high Mach-number flames. Spatial and scalar supersonic flame structures will be examined in ¡¥canonical¡¦ configurations designed to maximize the flow-chemistry interaction effects.Fundamental understanding of the interaction between fluid mechanics and chemistry under supersonic conditions is the key expected outcome, and the experimental results from this work should prove valuable for model development as well as computational comparisons. The study of flow-chemistry interaction in turbulent flames that exhibit pressure variation has large significance to a wide range of aerospace propulsion applications, from jet engine combustors and afterburners, to pulse-detonation engines and rocket exhausts. In addition, graduate and undergraduate students will learn by participating in cutting-edge research involving laser diagnostics and supersonic flames. Students working with the group will also benefit from summer visits to Sandia National Laboratories and participation in conferences and workshops. The PI will also develop practical experimental educational modules on issues in optics and physics for use in grades 9-12. The modules deal with fundamental issues in optics and physics, and are closely related to the research aspects of the proposed work. Members of under-represented groups will be engaged by the outreach as well as the research program