ABSTRACT

The focus of the present study is to evaluate the capability of reaction-diffusion manifold (REDIM) technique combined with presumed filtered density function (PFDF) method to calculate the important characteristics of turbulent partially-premixed flame with near-homogeneous inlets and inhomogeneous inlets. The REDIM approach reduces detailed chemical kinetics into two-dimensional chemistry table, where mass fractions of CO₂ and N₂ are used as reduced coordinates. The fluctuation of the scalars within the LES filter volume is modeled by the PFDF method. Higher shear generated turbulent intensity at the mixing layer of the fuel and air streams provides the near-homogeneous inlet conditions. The radial statistics analysis of the mixture fraction, temperature and species mass faction, and their comparison with the experimental data show the good performance of the REDIM-PFDF model. Scatter plots show the better agreement for the inhomogeneous case. The near-homogeneous case exhibits little discrepancy with the measured distribution because of the limited ability of the present model to capture local extinction effects. Flame index parameter identifies the multiple combustion modes present at different locations. This parameter shows the presence of premixed and diffusion dominated types of combustion near the main jet exit plane in the inhomogeneous and near-homogeneous cases, respectively.

摘要

本研究的重点是评估反应扩散歧管（REDIM）技术结合假定过滤密度函数（PFDF）方法计算具有近均匀入口和不均匀入口的湍流部分预混火焰的重要特征的能力。REDIM 方法将详细的化学动力学简化为二维化学表，其中 CO ₂和 N _{2的质量分数}用作简化坐标。LES过滤器体积内的标量波动由PFDF方法建模。在燃料和空气流的混合层处产生的较高剪切产生的湍流强度提供了近乎均匀的入口条件。混合分数、温度和物种质量分数的径向统计分析，以及它们与实验数据的比较，表明REDIM-PFDF模型具有良好的性能。散点图显示了非均匀情况的更好一致性。由于当前模型捕捉局部消光效应的能力有限，接近均匀的情况与测量的分布几乎没有差异。火焰指数参数识别存在于不同位置的多种燃烧模式。