Response characteristics of a stretched cylindrical diffusion flame to periodic oscillation of air flow velocity (Influences of velocity oscillation amplitude on flame response)
Response characteristics of a stretched cylindrical diffusion flame to periodic oscillation of air flow velocity (Influences of velocity oscillation amplitude on flame response)
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DOI：
10.1299/transjsme.17-00444
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Yosuke Suenaga;H. Yanaoka;M. Kikuchi;S. Sasaki
中科院分区：
文献类型：
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作者：
Yosuke Suenaga;H. Yanaoka;M. Kikuchi;S. Sasaki
实验研究了拉伸圆柱形扩散火焰对正弦气流速度振荡的频率特性。火焰相对于气流具有凸曲率。燃料是用氮气稀释的甲烷和氧化剂空气。火焰形成于滞止面的气流侧。振荡频率f的范围为10 Hz至250 Hz。为了明确气流速度的振幅A对火焰响应的影响，选择了三种振幅。用高速摄像机拍摄火焰图像，分析火焰半径rf、火焰厚度δ和火焰亮度Lf。用粒子图像测速仪测量了喷嘴出口处的气流速度va。尽管空气流ga的速度梯度快速响应于变化的va而与f和A无关，但是燃料流gf的梯度随着f和A的增加而延迟。这里，ga与火焰拉伸效应相关，gf影响燃料输送。rf对变化va的响应也随f和A的增加而延迟。与火焰曲率效应有关的δ/rf随f和A的变化而变化。Lf的振荡幅度相对于f具有最大值，而与A无关。在相同的风速波动范围内，这些最大值大于稳定火焰的最大值。Lf相对于f的这种复杂变化与δ/rf和gf的相应时间变化的相位差以及这些值的幅度密切相关。
An experimental study investigated the frequency characteristics of a stretched cylindrical diffusion flame in response to sinusoidal air flow velocity oscillation. The flame has a convex curvature with respect to the air stream. The fuel was methane diluted with nitrogen, and oxidizer air. The flame was formed in the air stream side from the stagnation surface. The oscillation frequency f ranged from 10 Hz to 250 Hz. In order to clarify the influence of an oscillation amplitude A of the air flow velocity on the flame responses, three kinds of amplitude were chosen. The flame was photographed by the high speed video camera, and flame radius rf, flame thickness δ, and flame luminosity Lf were analyzed. The air flow velocity va at the nozzle outlet was measured by using particle image velocimetry. Though velocity gradient of the air flow ga responds quickly to the changing va regardless of f and A, the gradient of the fuel flow gf delays with increasing f and A. Here, ga correlates to the flame stretch effect, and gf impacts the fuel transportation. Response of rf to varying va also delays with increasing f and A. δ/rf, which relates to the flame curvature effect, responds complicated with the change in f and A. Oscillation amplitudes of Lf have maximum values with respect to f regardless of A. These maximum values are greater than those of a steady flame, over the same air velocity fluctuation ranges. This complex change in the Lf with respect to f is closely related to the phase difference in the respective time variations in δ/rf and gf, and the magnitude of these values.