A New Method for Imaging Mixture Fraction in Turbulent Non-premixed Flames

湍流非预混火焰中混合分数成像的新方法

• 批准号: 1134020
• 负责人: Noel Clemens
• 金额: $ 32.28万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1134020&HistoricalAwards=false
• 关键词: New; Method; Imaging; Mixture; Fraction

1134020ClemensThe improvement of combustion models for turbulent non-premixed combustion is severely limited by the lack measurements of mixture fraction and its dissipation in complex reacting systems. Currently, the highest fidelity mixture fraction measurements are inferred from Raman/Rayleigh scattering, but these measurements are difficult to apply in more applied combustion environments where walls, soot or particles may be present. We propose to develop a new technique that holds promise for enabling space- and time-resolved imaging of a conserved scalar in turbulent reacting flows, and which can be applied in a wider range of environments than alternative techniques. This new technique is based on using two-photon laser-induced fluorescence (LIF) of a noble gas (e.g., Kr or Xe), which is seeded into the fuel or oxidizer stream. Noble gases are inert in the presence of combustion and so can be treated as a conserved scalar. The noble-gas LIF measurement gives the mole fraction of the conserved scalar, but a temperature measurement and state relationship are required to infer the mixture fraction (i.e., mass fraction of atoms originating in the fuel stream). Our main objectives will be the following: (i) to improve our understanding of the technique's limitations, particularly regarding the need for an assumed state relationship, (ii) to determine if the technique can be applied with higher-hydrocarbon fuels where laser beam absorption, fluorescence interference and quenching may add additional difficulties, (iii) to combine the technique with particle image velocimetry (PIV) to obtain important and still unique mixture-fraction/velocity correlation data in flames, (iv) to investigate two-photon Xe LIF as an alternative conserved scalar, and (v) explore combining noble-gas LIF with filtered Rayleigh scattering to obtain simultaneous temperature fields when particles/soot/walls are present. Intellectual Merit: The proposed work has as its objective the further development of a new diagnostic technique, which holds promise for enabling measurements of mixture fraction and its dissipation in non-premixed combustion systems. The main conserved scalar of interest is krypton, although xenon will be investigated. The combined two-photon LIF will enable conserved scalar measurements to be made in more applied flows, such as confined combustors, or in flows with particles. This feature will enable one to combine mixture fraction imaging with PIV, and potentially to make conserved measurements in flows with soot or soot precursors. It also can be effectively used as a technique for studying mixing/combustion where safety concerns preclude the use of toxic-gas markers.Broader Impacts: This new technique holds promise for enabling measurements of mixture fraction (or a related surrogate conserved scalar quantity) in combustion environments where such measurements were previously not practical, such as gas-turbines, IC engines, fires, and supersonic combustors. Noble-gas LIF is potentially much easier to implement than alternative techniques and it is likely that the technique will see much wider use in academics, government and industry. The data that can be provided by the technique could potentially impact the accuracy of advanced combustion models and therefore impact a wide-range of technologies including those that utilize sustainable fuels. As great strides are made in computational engineering, we must not lose sight of the importance of validating the computations and this will require that we maintain and develop the experimental infrastructure that enables the acquisition of the needed data.

1134020Clemens 由于缺乏混合分数的测量及其在复杂反应系统中的耗散，湍流非预混燃烧的燃烧模型的改进受到严重限制。目前，最高保真度的混合分数测量是从拉曼/瑞利散射推断的，但这些测量很难应用于可能存在墙壁、烟灰或颗粒的更广泛的燃烧环境。我们建议开发一种新技术，有望实现湍流反应流中守恒标量的空间和时间分辨成像，并且与替代技术相比，它可以应用于更广泛的环境。这项新技术基于使用惰性气体（例如氪或氙）的双光子激光诱导荧光 (LIF)，将其注入燃料或氧化剂流中。稀有气体在燃烧时呈惰性，因此可以被视为守恒标量。惰性气体 LIF 测量给出了守恒标量的摩尔分数，但需要温度测量和状态关系来推断混合分数（即源自燃料流的原子的质量分数）。我们的主要目标如下：（i）提高我们对该技术局限性的理解，特别是关于假设状态关系的需要，（ii）确定该技术是否可以应用于较高碳氢化合物燃料，其中激光束吸收、荧光干扰和淬灭可能会增加额外的困难，（iii）将该技术与粒子图像测速（PIV）结合起来以获得重要且仍然独特的信息 火焰中的混合物分数/速度相关数据，(iv) 研究双光子 Xe LIF 作为替代守恒标量，以及 (v) 探索将惰性气体 LIF 与过滤瑞利散射相结合，以获得当存在颗粒/烟灰/墙壁时的同步温度场。智力优点：拟议工作的目标是进一步开发一种新的诊断技术，该技术有望实现非预混燃烧系统中混合分数及其耗散的测量。尽管我们将研究氙，但我们感兴趣的主要守恒标量是氪。组合的双光子 LIF 将使守恒标量测量能够在更多应用的流动中进行，例如受限燃烧室或带有颗粒的流动。这一功能将使人们能够将混合分数成像与 PIV 相结合，并有可能在具有烟灰或烟灰前体的流中进行保守测量。它还可以有效地用作研究混合/燃烧的技术，因为出于安全考虑而无法使用有毒气体标记。 更广泛的影响：这项新技术有望在燃烧环境中测量混合分数（或相关的替代守恒标量），而在这些环境中，这种测量以前不可行，例如燃气轮机、内燃机、火灾和超音速燃烧室。惰性气体 LIF 可能比替代技术更容易实施，并且该技术很可能会在学术界、政府和工业界得到更广泛的应用。该技术提供的数据可能会影响先进燃烧模型的准确性，从而影响广泛的技术，包括那些利用可持续燃料的技术。随着计算工程取得巨大进步，我们绝不能忽视验证计算的重要性，这将要求我们维护和开发能够获取所需数据的实验基础设施。