The Sydney piloted partially premixed flames with both homogeneous and inhomogeneous fuel/air inlets are studied using a dynamic second-order moment closure model in the framework of large eddy simulation with a four-step global reaction mechanism. The filtered reaction rates are directly closed using the second-order correlation moments of reactive scalars. Good agreements between LES and experimental data are obtained for time-averaged radial profiles, scatter plots and conditional profiles for mixture fraction, temperature and major species, demonstrating the capability of the model to reproduce the partially premixed flames. Further studies of the combustion characteristics of the two flames suggest that the coincident occurrence of high dissipation and reaction can weaken the flame stability for the homogeneous case, while the separation in the inhomogeneous case can help to enhance the stability. In the inhomogeneous case, the premixed flame is dominant upstream with a proportion of 70% to heat release and then decreases to about 40% downstream. The inhomogeneous conditions can establish a near-stoichiometric reactant belt with lower dissipation near the nozzle exit, which connects the hot pilot and central cold fuel/air mixture. Through this belt, the hot pilot gas can ignite the near-stoichiometric reactant in premixed mode by releasing significant heat and the flame can propagate upstream to form a stable flame.

中文翻译：

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使用动态二阶矩闭合模型对具有非均匀入口的湍流部分预混火焰进行大涡模拟

在具有四步全局反应机制的大涡模拟框架中，使用动态二阶矩闭合模型研究了具有均质和非均质燃料/空气入口的悉尼先导部分预混火焰。使用反应标量的二阶相关矩直接关闭过滤后的反应速率。对于混合分数、温度和主要物质的时间平均径向剖面、散点图和条件剖面，LES 和实验数据之间获得了良好的一致性，证明了模型再现部分预混火焰的能力。对两种火焰燃烧特性的进一步研究表明，高耗散和反应同时发生会削弱均质情况下的火焰稳定性，而在非均质情况下的分离有助于增强稳定性。在不均匀的情况下，预混火焰在上游占主导地位，占放热的 70%，然后下降到下游​​的 40% 左右。不均匀的条件可以建立一个接近化学计量的反应物带，在喷嘴出口附近具有较低的耗散，连接热的引燃器和中央冷燃料/空气混合物。通过这条带，热的引燃气体可以通过释放大量热量以预混模式点燃接近化学计量的反应物，并且火焰可以向上游传播以形成稳定的火焰。不均匀的条件可以建立一个接近化学计量的反应物带，在喷嘴出口附近具有较低的耗散，连接热的引燃器和中央冷燃料/空气混合物。通过这条带，热的引燃气体可以通过释放大量热量以预混模式点燃接近化学计量的反应物，并且火焰可以向上游传播以形成稳定的火焰。不均匀的条件可以建立一个接近化学计量的反应物带，在喷嘴出口附近具有较低的耗散，连接热的引燃器和中央冷燃料/空气混合物。通过这条带，热的引燃气体可以通过释放大量热量以预混模式点燃接近化学计量的反应物，并且火焰可以向上游传播以形成稳定的火焰。