Geometrical Properties and Turbulent Flame Speed Measurements in Stationary Premixed V-flames Using Direct Numerical Simulation
Geometrical Properties and Turbulent Flame Speed Measurements in Stationary Premixed V-flames Using Direct Numerical Simulation
复制标题
DOI：
10.1007/s10494-010-9284-1
复制
发表时间：
2011-12
期刊：
影响因子：
--
通讯作者：
T. Dunstan;N. Swaminathan;K. Bray;R. Cant
中科院分区：
文献类型：
--
作者：
T. Dunstan;N. Swaminathan;K. Bray;R. Cant
对v型火焰结构下的预混湍流火焰进行了三维全可压缩直接数值模拟。详细描述了控制方程和数值实现，包括对Navier-Stokes特征边界条件（NSCBC）的修改，以适应火焰穿过边界时产生的陡峭横向速度和成分梯度。在湍流强度u ' /sL为1、2和6时，考虑了三种情况。通过表面条件下的位移速度、曲率和切向应变率的分布，并与类似处理的平面火焰的数据进行比较，评估了火焰支架对下游火焰特性的影响。在火焰支架下游大于17δ的距离内，其分布与平面火焰难以区分，其中δ表示层流火焰的热厚度。构造了Favre平均场，发现平均火焰刷的生长可以用简单的Taylor型扩散很好地描述。紊流火焰速度是根据描述平均反应过程的等值面传播速度的表达式来计算的，该表达式根据火焰刷内平均反应、扩散和紊流通量之间的不平衡来表示。将结果与消耗速度sC（由平均反应速率的积分计算得到）和最近开发的火焰速度模型的预测进行比较（Kolla等人，燃烧科学技术181(3):518-535,2009）。考虑到切向对流通量的影响，模型的预测在所有情况下都得到了改进，并且在湍流强度较高的情况下，模型的总体一致性较好。
Three dimensional, fully compressible direct numerical simulations (DNS) of premixed turbulent flames are carried out in a V-flame configuration. The governing equations and the numerical implementation are described in detail, including modifications made to the Navier–Stokes Characteristic Boundary Conditions (NSCBC) to accommodate the steep transverse velocity and composition gradients generated when the flame crosses the boundary. Three cases, at turbulence intensities,u′/sL, of 1, 2, and 6 are considered. The influence of the flame holder on downstream flame properties is assessed through the distributions of the surface-conditioned displacement speed, curvature and tangential strain rates, and compared to data from similarly processed planar flames. The distributions are found to be indistinguishable from planar flames for distances greater than about 17δthdownstream of the flame holder, whereδthis the laminar flame thermal thickness. Favre mean fields are constructed, and the growth of the mean flame brush is found to be well described by simple Taylor type diffusion. The turbulent flame speed,sTis evaluated from an expression describing the propagation speed of an isosurface of the mean reaction progress variablein terms of the imbalance between the mean reactive, diffusive, and turbulent fluxes within the flame brush. The results are compared to the consumption speed,sC, calculated from the integral of the mean reaction rate, and to the predictions of a recently developed flame speed model (Kolla et al., Combust Sci Technol 181(3):518–535, 2009). The model predictions are improved in all cases by including the effects of mean molecular diffusion, and the overall agreement is good for the higher turbulence intensity cases once the tangential convective flux ofis taken into account.