Deng Kai, Xue Chenyang, Liu Zhenyu, Hu Jinlin, Zhong Yingjie
Institute of Energy and Power Engineering, College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China.
ACS Omega. 2023 Feb 22;8(9):8664-8674. doi: 10.1021/acsomega.2c07987. eCollection 2023 Mar 7.
A method for determining combustion instability using flame structure parameters is presented. A speaker is used to provide controllable external excitation for the combustion system. The experimental object is a methane-air swirl premixed flame. The flame structure parameters such as height, width, and flame surface density extracted from the hydroxyl planar laser-induced fluorescence image were used to analyze combustion instability at different equivalence ratios (0.8-1.2) and inlet flow rates. It is confirmed that the inflection point of the flame structure parameters corresponds to the evolution of combustion instability verified by the flame transfer function. The results show that with the increase of inlet velocity , the flame aspect ratio /, average OH* concentration, and surface density Σ gradually decrease. The thickness δ of the flame brush shows an increasing trend under the same conditions. With the increase of equivalence ratio Φ, the average OH* concentration and flame surface density Σ increase continuously. The changing trend of flame brush thickness decreases first and then increases to a peak. Finally, it continues to decline after reaching the peak. The flame responds strongly to the sound field when the equivalence ratio is 0.9 and 1.0. In the range of 80-240 Hz, the flame response near 110 and 190 Hz is stronger at each equivalence ratio (0.8-1.0). When the equivalent ratio is 0.9 and 1.0, the amplitude fluctuations of the flame transfer function are much larger than those under other conditions. Meanwhile, the specific performances of the flame structure parameters are that the flame height, average OH* concentration, and flame surface density decrease, and the flame brush thickness increases. These results can be used as a basis for judging combustion instability. This method proves that the parameter information monitored during the flame combustion process can be used to judge the changes in combustion conditions and can adjust the corresponding conditions more accurately and quickly.
提出了一种利用火焰结构参数确定燃烧不稳定性的方法。使用扬声器为燃烧系统提供可控的外部激励。实验对象是甲烷 - 空气旋流预混火焰。从羟基平面激光诱导荧光图像中提取的火焰高度、宽度和火焰表面密度等火焰结构参数，用于分析不同当量比（0.8 - 1.2）和入口流速下的燃烧不稳定性。证实了火焰结构参数的拐点对应于由火焰传递函数验证的燃烧不稳定性的演变。结果表明，随着入口速度的增加，火焰纵横比 /、平均OH浓度和表面密度Σ逐渐减小。在相同条件下，火焰刷厚度δ呈增加趋势。随着当量比Φ的增加，平均OH浓度和火焰表面密度Σ持续增加。火焰刷厚度的变化趋势先减小后增加至峰值，最后在达到峰值后继续下降。当当量比为0.9和1.0时，火焰对声场响应强烈。在80 - 240 Hz范围内，每个当量比（0.8 - 1.0）下，110和190 Hz附近的火焰响应更强。当当量比为0.9和1.0时，火焰传递函数的幅值波动比其他条件下大得多。同时，火焰结构参数的具体表现为火焰高度、平均OH*浓度和火焰表面密度减小，火焰刷厚度增加。这些结果可作为判断燃烧不稳定性的依据。该方法证明了在火焰燃烧过程中监测到的参数信息可用于判断燃烧条件的变化，并能更准确、快速地调整相应条件。
