Flame Generates Turbulence in Turbulent Premixed Flames

目前的工作测量了三种不同当量比的湍流火焰刷中不同位置处的单个速度变化和穿过小火焰的湍流变化，以与理论进行比较。测量采用三元件静电探针 (EP) 和二元件激光多普勒测速仪 (LDV)。 LDV 测量局部气体速度的轴向和径向分量，而 EP 的三个传感器位于穿过燃烧器轴线的垂直平面（包含 LDV 速度分量的平面），测量火焰在该平面中三个点的到达时间。根据到达时间，可以获得火焰方向和速度在平面上的投影。所有 EP 和 LDV 传感器均位于直径约 1 mm 的固定体积元件内，以提供本地时间分辨信息。该技术具有快速响应和良好灵敏度的 EP 优点，以及侵入性和解释复杂性的 EP 缺点，但它非常适合此处寻求的数据类型。理论预测，与局部平面小火焰表面相切的速度分量在穿过小火焰时保持恒定。在测量精度范围内，数据与该预测一致。数据还表明，如预期的那样，相对于小火焰测量的垂直于小火焰的速度分量在穿过小火焰时趋于增加。由此，小火焰可以在最初的各向同性湍流中产生各向异性。它们还产生以未燃烧或燃烧气体为条件的湍流光谱的差异。因此，实验证明了小火焰对湍流的局部改变。湍流火焰刷中不同位置处的修改在数量上不同，但在质量上相似，因为在这些火焰中的所有位置处，径向方向上的湍流比轴向方向上的湍流增强得更强烈。较少的

The present work measures individual velocity changes and changes in turbulence across flamelets at different positions in the turbulent flame brush for three different equivalence ratios, for comparison with theory. The measurements employ a three-element electrostatic probe (EP) and a two-component laser-doppler velocimeter (LDV). The LDV measures axial and radial components of the local gas velocity, while the EP, whose three sensors are located in a vertical plane that passes through the burner axis, containing the plane of the LDV velocity components, measures arrival times of flamelets at three points in that plane. From the arrival times, the projection of flamelet orientation and velocity on the plane are obtained. All of the EP and LDV sensors are located within a fixed volume element of about 1 mm diameter to provide local, time-resolved information. The technique has the EP advantages of rapid response and good sensitivity and the EP disadvantages of intrusiveness and comple … More xity of interpretation, but it is well suited to the type of data sought here. Theory predicts that the component of velocity tangent to the surface of a locally planar flamelet remains constant in passing through the flamelet. The data are consistent with this prediction, within the accuracy of the measurement. The data also indicate that the component of velocity normal to the flamelet, measured with respect to the flamelet, tends to increase in passing through the flamelet, as expected. The flamelets thereby can generate anisotropy in initially isotropic turbulence. They also produce differences in turbulent spectra conditioned on unburnt or burnt gas. Local modifications of turbulence by flamelets thus are demonstrated experimentally. The modifications are quantitatively different at different locations in the turbulent flame brush but qualitatively similar in that the turbulence is enhanced more strongly in the radial direction than in the axial direction at all positions in these flames. Less