论文标题
湍流提起的H2/N2火焰的LES和有限体积CMC建模：CMC网格分辨率和数值方案的影响
LES and finite-volume CMC modelling of a turbulent lifted H2/N2 flame: effects of CMC mesh resolution and numerical scheme
论文作者
论文摘要
具有三维有限体积的条件力矩闭合（CMC）模型的大型涡流模拟，用于使用详细的化学磁质的氢 /氮提升的火焰。重点是有限体积CMC模型对反应性标量分布和不稳定火焰动力学预测的网格分辨率和对流方案的影响。结果表明，提升高度被低估了，用更粗的CMC网格过度预测了反应性标量（例如温度，H2和OH）。还发现，CMC网格的进一步完善不会大大改善结果。最具反应性和化学计量的OH质量分数的时间序列表明，较细的CMC网格比更粗的CMC网格捕获更不稳定的细节。此外，粗CMC网格具有较低的条件标量耗散率，这将促进火焰底座的自动点击率。此外，还研究了CMC方程中对流方案对举起的火焰特性的影响。结果表明，不同的对流方案导致时间平均温度，混合部分和物种质量分数的差异有限。此外，H2和OH质量分数的RMS值与混合上风和中心差异方案（尤其是在火焰底座周围）相比显示出更大的偏差。此外，CMC面上的数值通量的分布在上风方案和混合方案之间也显示出明显的区别。对单个CMC术语的预算分析表明，一系列CMC面孔对Upwind方案具有可比的贡献。但是，使用杂种方案，瞬时通量主要来自有限的CMC面。当使用上风方案时，CMC细胞的反应性更容易受到其邻居的影响。
Large eddy simulations with three-dimensional finite-volume Conditional Moment Closure (CMC) model are performed for a hydrogen / nitrogen lifted flame with detailed chemical meachanism. The emphasis is laid on the influences of mesh resolution and convection scheme of finite-volume CMC model on predictions of reactive scalar distribution and unsteady flame dynamics. The results show that the lift-off height is underestimated and the reactive scalars (e.g. temperature, H2 and OH) are over-predicted with coarser CMC mesh. It is also found that further refinement of the CMC mesh would not considerably improve the results. The time sequences of the most reactive and stoichiometric OH mass fractions indicate that finer CMC mesh can capture more unsteady details than coarser CMC mesh. Moreover, the coarse CMC mesh has lower conditional scalar dissipation rate, which would promote the ealier auto-ignition of the flame base. Besides, the effects of the convection schemes in the CMC equations on the lifted flame characteristics are also investigated. It is shown that different convection schemes lead to limited differences on the time-averaged temperature, mixture fraction and species mass fractions. Moreover, the RMS values of H2 and OH mass fractions show larger deviation from the measurements with hybrid upwind and central differencing scheme, especially around the flame base. Furthermore, the distributions of the numerical flux on the CMC faces also show obvious distinction between the upwind scheme and the blending scheme. The budget analysis of the individual CMC terms shows that a sequence of CMC faces has comparable contributions with upwind scheme. However, with the hybrid schemes, the instantaneous flux is dominantly from limited CMC faces. The reactivity of a CMC cell is more easily to be affected by its neighbors when the upwind scheme is used.
