Partially-premixed bluff-body flame dynamics and acoustic coupling in vitiated flows

0967474 Renfro智能优点在许多燃烧系统中，火焰需要在速度高于火焰速度的气流中稳定。 可以将钝体放置在流中以产生低速区域，从而实现火焰稳定。 钝体稳定火焰用于许多应用中，包括用于航空发动机的加力燃烧室。 在加力燃烧室火焰中，几个附加特征使对火焰稳定过程的全面理解变得复杂：（1）由于发动机内的燃烧，流被预热，使得温度和氧气水平影响火焰，（2）燃料被添加到靠近火焰的流中，使得燃料没有时间完全混合，以及（3）后燃器被封闭在一端（射流出口）开口的管道中，使得声学共振能够引起火焰中的振荡。 以前的研究主要研究火焰稳定没有这些complications.The拟议的工作将使用最近建造的燃烧室钻机在康涅狄格州大学，提供高速流与高温和降低氧气水平，以模拟在飞机发动机的条件。 该装置能够产生钝体稳定火焰，控制温度、氧气水平、燃料/空气混合和声级，以分别解决这三个复杂问题。 火焰稳定在一个测试部分与窗口，允许基于激光的测量和火焰成像。 火焰和流场的测量将通过粒子成像测速仪和平面激光诱导荧光。 此外，在普惠公司的支持下，通过设备和人员交换，将完成不稳定火焰的高速成像。 这些测量恢复了局部速度和火焰形状，以便可以定量地检查火焰不稳定的原因。 这些测量结果将应用于飞机加力燃烧室火焰的三个选定的功能参数变化。 由此产生的实验预计将提供一个更完整和定量的描述火焰稳定过程的钝体火焰比目前可用。 将向公众提供许多案例的定量数据集。 这项研究的结果是直接适用于飞机加力燃烧室，但也将广泛适用于新的燃烧室设计与替代燃料，这可能需要增强钝体稳定燃料灵活operation.Broader ImpactsThe建议的工作将导致更好的基本理解火焰传播的流动与非均匀的燃料/空气混合，包括温度升高和氧气水平降低的影响。这对飞机发动机加力燃烧室等装置的设计有直接影响，但也扩大了对流动中基本火焰行为的理解，这可能广泛适用于改进新燃料的燃烧室设计。该项目每年将资助两名研究生和一名本科生，并将为这些学生提供接受广泛光学测量技术培训的机会。 学生和PI将直接与普惠公司合作，选择试验条件和分析加力燃烧室数据，以提供康州大学试验台研究结果与更大的全尺寸试验之间的良好耦合。 研究生将有机会在P W实习。 该计划中测量的数据集将广泛共享，为未来的模型比较提供基础。

0967474RenfroIntellectual MeritIn many combustion systems, flames are required to be stabilized in flows with velocities higher than the flame speed. Bluff-bodies can be placed in the flow to create a low speed region to enable flame stabilization. Bluff-body stabilized flames are used in many applications including afterburners for aircraft engines. In afterburner flames several additional features complicate a comprehensive understanding of the flame stabilization process: (1) the flow is pre-heated due to combustion within the engine so that the temperature and oxygen levels affect the flame, (2) fuel is added to the flow close to the flame so that is does not have time to fully mix, and (3) the afterburner is enclosed in a duct open at one end (the jet exit) so that acoustic resonance can cause oscillations in the flame. Previous research has primarily studied flame stabilization without these complications.The proposed work will use a recently constructed combustor rig at the University of Connecticut that provides high speed flows with elevated temperatures and reduced oxygen levels to simulate conditions in an aircraft engine. The rig is capable of creating bluff-body stabilized flames with control over the temperature, oxygen level, fuel/air mixing, and acoustic level to address each of these three complications separately. The flames are stabilized within a test section with windows that permit laser-based measurements and imaging of the flame. Measurements of the flame and flow field will be made via particle imaging velocimetry and planar laser induced fluorescence. In addition, high-speed imaging of unsteady flames will be accomplished with the support of Pratt & Whitney through equipment and personnel exchange. These measurements recover the local velocity and flame shape so that the cause of flame de-stabilization can be quantitatively examined. These measurements will be applied as the three chosen features of aircraft afterburner flames are parametrically varied. The resulting experiments are anticipated to provide a more complete and quantitative description of the flame stabilization process for bluff-body flames than presently available. The quantitative data sets from numerous cases will be made publicly available. The results of this study are directly applicable to aircraft afterburners, but will also be broadly applicable to new combustor designs with alternative fuels, which may require enhanced bluffbody stabilization for fuel flexible operation.Broader ImpactsThe proposed work will lead to a better fundamental understanding of flame propagation in flows with non uniform fuel/air mixing including the effects of elevated temperature and reduced oxygen level. This has direct impact on the design of devices such as afterburners for aircraft engines, but also expands understanding of basic flame behavior in flows that could be broadly applicable to improved combustor design for new fuels. The project will support two graduate students and one undergraduate student each year, and will provide opportunities for these students to be trained in a broad range of optical measurement techniques. The students and PIs will collaborate directly with Pratt & Whitney on the selections of test conditions and analysis of afterburner data to provide good coupling between the results from the studies in the UConn rig and larger full scale tests. Graduate students will have the opportunity for internships at P&W. The data sets measured in this program will be shared broadly to provide a basis for future model comparisons.