A direct numerical simulation analysis of pressure variation in turbulent premixed Bunsen burner flames-Part 1: Scalar gradient and strain rate statistics
A direct numerical simulation analysis of pressure variation in turbulent premixed Bunsen burner flames-Part 1: Scalar gradient and strain rate statistics
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DOI：
10.1016/j.compfluid.2018.03.010
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发表时间：
2018-09-15
影响因子：
2.8
通讯作者：
Chakraborty, N.
中科院分区：
文献类型：
--
作者：
Klein, M.;Alwazzan, D.;Chakraborty, N.
对本生灯火焰进行了三维简单化学直接数值模拟（DNS）。对于同一组由层流燃烧速度归一化的平均和均方根入口速度值以及由喷嘴直径归一化的积分长度尺度，已经考虑了许多情况。层流燃烧速度和火焰厚度随压力的变化导致流动和湍流雷诺数随压力的增加而增加。这也引起这些火焰的达姆科勒数和卡洛维茨数的变化，因此它们在状态图上占据不同的位置。出于这个原因，在最低压力的两个额外的情况下，已被模拟，以匹配最高压力的情况下，通过改变归一化的均方根速度在一种情况下，而在另一种情况下，修改的积分长度尺度的湍流雷诺数。已经发现，压力和湍流雷诺数的变化不具有显着的影响的反应进展梯度（即表面密度函数）和流体动力学法向应变率的大小的平均行为。然而，喷嘴直径和火焰厚度之间的长度尺度分离随着压力的增加而增加，这使得Darrieus-Landau（DL）不稳定性的发生非常可能在高压下的火焰。DL不稳定性的存在会影响火焰曲率统计，这反过来又会影响膨胀率和流体动力学切向应变率的平均行为。(C)2018爱思唯尔有限公司版权所有
Three-dimensional simple chemistry Direct numerical simulations (DNS) of Bunsen burner flames have been carried out for different pressure values. A number of cases have been considered for the same set of values of mean and root-mean-square inlet velocities normalised by the laminar burning velocity and the integral length scale normalised by the nozzle diameter. The modifications of laminar burning velocity and flame thickness with pressure lead to an increase in both flow and turbulent Reynolds numbers with increasing pressure. This also gives rise to changes in Damkohler number and Karlovitz numbers for these flames and thus they occupy different locations on the regime diagram. For this reason, two additional cases at the lowest pressure have been simulated to match the turbulent Reynolds number of the highest-pressure case by changing the normalised root-mean-square velocity in one case, whereas the integral length scale is modified in the other case. It has been found that pressure and turbulent Reynolds number variations do not have significant influences on the mean behaviours of the magnitude of the reaction progress gradient (i.e. Surface Density Function) and fluid-dynamic normal strain rate. However, the length scale separation between the nozzle diameter and flame thickness increases with increasing pressure, which makes the occurrence of the Darrieus-Landau (DL) instability highly likely for the flames at elevated pressures. The presence of the DL instability affects the flame curvature statistics, which in turn influence the mean behaviours of the dilatation rate and fluid-dynamic tangential strain rate. (C) 2018 Elsevier Ltd. All rights reserved.