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首页> 外文期刊>Combustion and Flame >Lifted methane-air jet flames in a vitiated coflow
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Lifted methane-air jet flames in a vitiated coflow

机译：通风的甲烷气流中升起的甲烷空气喷射火焰

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The present vitiated coflow flame consists of a lifted jet flame formed by a fuel jet issuing from a central nozzle into a large coaxial flow of hot combustion products from a lean premixed H_2/air flame. The fuel stream consists of CH_4 mixed with air. Detailed multiscalar point measurements from combined Raman-Rayleigh-LIF experiments are obtained for a single base-case condition. The experimental data are presented and then compared to numerical results from probability density function (PDF) calculations incorporating various mixing models. The experimental results reveal broadened bimodal distributions of reactive scalars when the probe volume is in the flame stabilization region. The bimodal distribution is attributed to fluctuation of the instantaneous lifted flame position relative to the probe volume. The PDF calculation using the modified Curl mixing model predicts well several but not all features of the instantaneous temperature and composition distributions, time-averaged scalar profiles, and conditional statistics from the multiscalar experiments. A complementary series of parametric experiments is used to determine the sensitivity of flame liftoff height to jet velocity, coflow velocity, and coflow temperature. The liftoff height is found to be approximately linearly related to each parameter within the ranges tested, and it is most sensitive to coflow temperature. The PDF model predictions for the corresponding conditions show that the sensitivity of flame liftoff height to jet velocity and coflow temperature is reasonably captured, while the sensitivity to coflow velocity is underpredicted.
机译：本发明的烟状同流火焰由升起的火焰组成，该升起的火焰由从中央喷嘴向稀薄的预混合H_2 /空气火焰的热燃烧产物的大同轴流中形成的燃料喷射形成。燃料流由CH_4与空气混合而成。对于单个基本情况，可以通过组合的拉曼-瑞利-LIF实验获得详细的多标量点测量结果。呈现实验数据，然后将其与合并了各种混合模型的概率密度函数（PDF）计算所得的数值结果进行比较。实验结果表明，当探头体积位于火焰稳定区域时，反应性标量的双峰分布变宽。双峰分布归因于瞬时提升火焰位置相对于探头体积的波动。使用改进的Curl混合模型进行的PDF计算可以很好地预测瞬时温度和成分分布，时间平均标量分布图以及多标量实验的条件统计量的若干但并非全部特征。一系列补充性的参数实验用于确定火焰上升高度对射流速度，顺流速度和顺流温度的敏感性。发现提升高度与测试范围内的每个参数近似线性相关，并且对同流温度最敏感。相应条件的PDF模型预测表明，合理地捕获了火焰上升高度对射流速度和并流温度的敏感度，而对并流速度的敏感度却被低估了。

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