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Response of lean premixed swirl tubular flame to acoustic perturbations
Experimental Thermal and Fluid Science ( IF 3.2 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.expthermflusci.2020.110199
Kang Ma , Xiao Yu , Xiaoyao Zhao , Xinyan Li , Shuiqing Li , Dan Zhao , Baolu Shi

Abstract This study experimentally examined the response of a lean premixed methane/air swirl tubular flame to the longitudinal acoustic perturbations. Experiments were conducted by varying the acoustic frequency (f0), acoustic power (P0) and inlet air flow rate (QA) to systematically study the acoustic-excited flame dynamics, including the flame stability, flame structure, heat release rate and acoustic pressure fluctuations. The results demonstrated that the lean tubular flame was much sensitive to longitudinal perturbations below 210 Hz. Even at low power of P0, the flame was forced to oscillate intensively when the perturbation was operated in two discontinuous frequency ranges of f0 = 150–200 and f0 = 50–100 Hz, while a weakened oscillation regime was observed in the middle range of f0 = 100–150 Hz; a lower frequency (less than 50 Hz) would extinguish the flame. An increase in P0 intensified the flame oscillation under the perturbations of 50–100 Hz, and even resulted in flame lift-off and blow off with f0 between 150 and 200 Hz. In comparison to f0 and P0, the effects of air flow rate (QA) seemed to be weaker. The proper orthogonal decomposition (POD) analysis was performed to interpret the contributions from the mean mode and fluctuating axial and circumferential modes that led to combustion instability. It was found that as the energy fraction of the axial mode exceeded 5.0%, the flame lift-off appeared in the lean swirl tubular configuration.

中文翻译:

贫预混旋流管状火焰对声扰动的响应

摘要 本研究通过实验检验了贫气预混甲烷/空气涡流管状火焰对纵向声扰动的响应。通过改变声频(f0)、声功率(P0)和进气流速(QA)进行实验,系统研究了声激发火焰动力学,包括火焰稳定性、火焰结构、放热速率和声压波动. 结果表明,贫管状火焰对低于 210 Hz 的纵向扰动非常敏感。即使在 P0 的低功率下,当扰动在 f0 = 150-200 和 f0 = 50-100 Hz 两个不连续频率范围内操作时,火焰也被迫强烈振荡,而在中间范围观察到减弱的振荡状态f0 = 100–150 Hz;较低的频率(小于 50 Hz)会熄灭火焰。P0 的增加在 50-100 Hz 的扰动下加剧了火焰振荡,甚至导致火焰在 150 和 200 Hz 之间的 f0 升起和吹散。与 f0 和 P0 相比,空气流量 (QA) 的影响似乎更弱。执行适当的正交分解 (POD) 分析以解释平均模式和波动的轴向和周向模式的贡献,这些模式导致燃烧不稳定。发现当轴向模式的能量分数超过 5.0% 时,火焰升起出现在稀薄涡流管状配置中。与 f0 和 P0 相比,空气流量 (QA) 的影响似乎更弱。执行适当的正交分解 (POD) 分析以解释平均模式和波动的轴向和周向模式的贡献,这些模式导致燃烧不稳定。发现当轴向模式的能量分数超过 5.0% 时,火焰升起出现在稀薄涡流管状配置中。与 f0 和 P0 相比,空气流量 (QA) 的影响似乎更弱。进行适当的正交分解 (POD) 分析以解释平均模式和波动的轴向和周向模式的贡献,这些模式导致燃烧不稳定。发现当轴向模式的能量分数超过 5.0% 时,火焰升起出现在稀薄涡流管状配置中。
更新日期:2020-11-01
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