Flamelet effects on local flow in turbulent premixed bunsen flames
Flamelet effects on local flow in turbulent premixed bunsen flames
复制标题
小火焰对湍流预混本生火焰局部流动的影响
DOI：
10.1080/713713113
复制
发表时间：
2003
影响因子：
1.9
通讯作者：
F. Williams
中科院分区：
文献类型：
--
作者：
J. Furukawa;F. Williams
在圆柱形燃烧器上研究了丙烷-空气湍流预混火焰在反应层区的流动。采用双色四光束激光多普勒测速系统和三元件静电探针，对湍流火焰刷中中心线和离轴两个位置的气体速度和火焰前缘运动进行了同步测量。第一次记录了取决于火焰是否在燃烧到未燃烧或未燃烧到燃烧方向上穿过测量体积的结果差异。在中心线上，火焰前锋运动的速度矢量相对于燃烧器轴线对称分布，与小火焰通道的方向无关，因为它们必须对称，但是当火焰前锋在未燃烧到燃烧的方向上通过时，这些矢量偏离轴线，主要指向燃烧器轴线，当火焰前锋在燃烧到未燃烧的方向上通过时，这些矢量远离燃烧器轴线。当前缘沿燃烧-未燃方向通过时，未燃混合气中的气体速度轴向分量较小，而当前缘沿未燃-燃烧方向通过时，已燃气中的气体速度轴向分量较小。在中心线上，气体速度的径向分量在与火焰面运动相反的方向上增加，但离轴它总是在远离燃烧器轴线的方向上增加。在燃烧后的气体中，斜坡被视为在LDV的气体速度的向上分量的痕迹，这不断增加，随着时间的小火焰通道之间的时间。有人建议，这些燃烧器稳定的湍流火焰是由近似垂直的火焰具有大致正弦形状，快速向上移动，而来回移动更慢，并通过测量位置交替在燃烧到未燃烧，然后未燃烧到燃烧的方向。这被解释为是起源的有关方面的气体速度变化在每个火焰前锋。还建议浮力可能在观察到的斜坡中发挥作用。
Turbulent premixed propane-air flames in the reaction-sheet regime are examined on a cylindrical burner. A two-color, four-beam laser Doppler velocimetry (LDV) system and a three-element electrostatic probe are employed to simultaneously measure gas velocities and flame-front movement at two positions in a turbulent flame brush, one on the centerline and the other off axis. Differences in results that depend on whether flamelets traverse the measurement volume in the burned-to-unburned or unburned-to-burned direction are recorded for the first time. On the centerline, velocity vectors of the flame-front movement are distributed symmetrically with respect to the burner axis, irrespective of the direction of flamelet passage, as they must be by symmetry, but off axis these vectors are directed mainly toward the burner axis when the flame front passes in the unburned-to-burned direction and away from the burner axis when it passes in the burned-to-unburned direction. When the front passes in the burned-to-unburned direction, the axial component of gas velocity is smaller in the unburned mixture, but when it passes in the unburned-to-burned direction, this component is smaller in the burned gas. On the centerline, the radial component of gas velocity increases in the direction opposite that of the flamelet motion, but off axis it always increases in the direction away from the burner axis. In the burned gas, ramps are seen in the LDV traces of the upward component of gas velocity, which continually increases with time between the times of flamelet passage. It is suggested that these burner-stabilized turbulent flames are composed of approximately vertical flamelets having roughly sinusoidal shapes, rapidly moving upward while moving back and forth more slowly, and passing the measuring position alternately in the burned-to-unburned then unburned-to-burned directions. This is explained to be the origin of the relevant aspects of the gas-velocity change across each flame front. It is also suggested that buoyancy may play a role in the observed ramps.