• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Combustion Science and Technology >Insights into the Bending Effect in Premixed Turbulent Combustion Using the Flame Surface Density Transport
【24h】

Insights into the Bending Effect in Premixed Turbulent Combustion Using the Flame Surface Density Transport

机译：利用火焰表面密度传递对预混湍流燃烧弯曲效应的认识

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The bending effect of turbulent flame speed variation (i.e., the deviation from the linear increase of flame speed with increasing root-mean-square turbulent velocity fluctuation) has been investigated based on a Direct Numerical Simulation database of statistically planar turbulent premixed flames propagating into forced unburned gas turbulence. The validity of Damkohler's first hypothesis has been utilized to analyze the bending effect in terms of generalized Flame Surface Density (FSD) evolution. The volume-integrated value of the tangential strain rate term of the FSD transport equation remains positive, whereas the volume-integrated value of the curvature term assumes negative values. Under statistically stationary state, the positive value of the volume-integrated tangential strain rate term remains in equilibrium with the negative value of the volume-integrated curvature term. It has been found that the contribution of the normal strain rate to the flame surface area remains negative for small turbulence intensities, which eventually become positive for large turbulence intensities. This is a consequence of the change of collinear alignment of the reaction progress variable gradient from the most extensive principal strain rate direction to the direction of the eigenvector associated with the most compressive principal strain rate with increasing turbulence intensity. An increase in turbulence intensity increases the width of the probability density functions of flame curvature, and thereby increases the surface-averaged curvature squared values. This eventually makes the FSD curvature term due to the tangential diffusion component of displacement speed as the major contributor to the negative contribution of the volume-integrated curvature term in the FSD transport equation for large turbulence intensities. However, the negative contribution of the volume-integrated FSD curvature term does not increase indefinitely with increasing turbulence intensity and the inner cut-off scale, which also limits the maximum possible value of the volume-integrated FSD strain rate term under statistically stationary state, governs the maximum possible destruction of flame surface area. It has been argued that the upper limits of the flame surface area generation and destruction are responsible for the bending effects in the variations of turbulent flame speed and flame surface area.
机译：基于直接平面模拟数据库，研究了湍流火焰速度变化的弯曲效应（即，偏离火焰速度随线性均方根湍流波动增加而线性增加的偏差）未燃烧的湍流。 Damkohler的第一个假设的有效性已被用来分析广义火焰表面密度（FSD）演变过程中的弯曲效应。 FSD传递方程的切向应变率项的体积积分值保持为正，而曲率项的体积积分值为负。在统计稳定状态下，体积积分切向应变率项的正值与体积积分曲率项的负值保持平衡。已经发现，法向应变率对火焰表面积的贡献对于小湍流强度仍然是负的，而对于大湍流强度最终是正的。这是反应过程变量梯度从最广泛的主应变率方向到与最大压缩主应变率相关的特征向量方向的共线排列随湍流强度增加而变化的结果。湍流强度的增加增加了火焰曲率的概率密度函数的宽度，从而增加了表面平均曲率平方值。由于位移速度的切向扩散分量，这最终使FSD曲率项成为大湍流强度的FSD输运方程中体积积分曲率项的负贡献的主要贡献者。但是，体积积分FSD曲率项的负贡献不会随着湍流强度和内部截止尺度的增加而无限增加，这也限制了在统计平稳状态下体积积分FSD应变率项的最大可能值，控制火焰表面积的最大可能破坏。有人认为，火焰表面积产生和破坏的上限是湍流火焰速度和火焰表面积变化中的弯曲效应的原因。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号