Effect of flow distortion on fuel/air mixing and combustion in an upstream-fueled cavity flameholder for a supersonic combustor
Effect of flow distortion on fuel/air mixing and combustion in an upstream-fueled cavity flameholder for a supersonic combustor
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DOI：
10.1016/j.expthermflusci.2017.06.013
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发表时间：
2017-11
影响因子：
3.2
通讯作者：
S. Etheridge;J. Lee;C. Carter;M. Hagenmaier;Ryan T. Milligan
中科院分区：
文献类型：
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作者：
S. Etheridge;J. Lee;C. Carter;M. Hagenmaier;Ryan T. Milligan
本文研究了入射冲击波对上游喷油腔式火焰座内流场、燃料分布和燃烧的影响。采用了两个撞击位置：(1)在喷油器附近（所谓的冲击对喷气机情况）和(2)在空腔剪切层（冲击对空腔情况）。用阴影图来描述流场。空气中加入一氧化氮（NO）作为模拟燃料，由NO分子产生的平面激光诱导荧光（NO- plif）用于表征燃料/空气混合，OH分子的平面激光诱导荧光用于表征实际燃烧过程。将阴影图像和NO-PLIF图像与reynolds -average - navier Stokes （RANS）的CFD（计算流体动力学）解进行比较，以评估和解释无反应试验的实验结果。激波对空腔剪切层的作用是控制空腔内的燃料分布。激波对射流的影响是迫使剪切层深入空腔，从而导致在空腔中心线附近的燃料浓度较高。空腔冲击导致剪切层在空腔上游分离。燃料羽流破碎的增加提高了混合均匀性。当激波撞击空腔时，燃烧更强烈、更均匀，而当激波撞击射流时，燃烧仅限于空腔边缘。在空腔冲击情况下提供的更大的混合降低了中心线附近的燃料浓度，并允许在空腔中心更强的燃烧。在两种情况下，燃油喷射动量通量比增加一倍不会对燃油分布模式产生强烈影响，但在空腔冲击情况下，燃烧会减少，因为中心线处的燃油浓度较高。
This paper describes an experimental study of the effects of an incident shockwave on the flow field, fuel distribution and combustion within a cavity flameholder with upstream fuel injection. Two impingement locations are employed: (1) near the fuel injector (the so-calledshock-on-jetcase) and (2) on the cavity shear layer (theshock-on-cavitycase). Shadowgraph is used to characterize the flow field. Air seeded with nitric oxide (NO) is used as the simulated fuel and the resulting planar laser-induced fluorescence (NO-PLIF) from NO molecules is used to characterize fuel/air mixing while planar laser-induced fluorescence of OH molecules to characterize the actual combustion process. The shadowgraph and NO-PLIF images are compared with a CFD (Computational Fluid Dynamics) solution of the Reynolds-averaged-Navier Stokes (RANS) for assessment and explanation of experimental results of non-reacting tests. The effect of the shock on the cavity shear layer is to control the fuel distribution within the cavity. The effect of the shock on the jet is to force the shear layer deep within the cavity, which results in higher fuel concentrations near the cavity centerline. Theshock-on-cavitycase causes the shear layer to separate upstream of the cavity. Mixing uniformity is enhanced by the increased breakup of the fuel plume. Combustion is stronger and more uniform with the shock impinging on the cavity, while it is limited to the edges of the cavity with shock impingement on the jet. The greater mixing afforded in theshock-on-cavitycase reduces the fuel concentration near the centerline and allows stronger burning in the center of the cavity. Doubling the fuel injection momentum flux ratio does not strongly affect the pattern of fuel distribution in either case, but combustion in theshock-on-cavitycase is reduced, because the fuel concentration at the centerline is high.