Dynamical motion of Bunsen flame tip with flow rotation

本文对本生火焰在气流旋转作用下的动态运动进行了实验研究。预混合物（甲烷/空气混合物或丙烷/空气混合物）从内径为12 mm的管式燃烧器向上喷射。燃烧器以任意转速旋转。由于蜂窝体安装在燃烧器中，所获得的流动旋转可以假设为刚体旋转。当燃烧器不旋转时（旋流数S=0），形成公知的锥形本生火焰。当预混混合气的刘易斯数大于1时，随着S的增加，在S=1.04附近，锥形火焰向振荡火焰转变。随着S的进一步增加，火焰向平台火焰转变。火焰尖端运动频率随S的增大而减小。这是由于轴向速度随着流动旋转引起的离心力效应的增加而减小。锥形火焰和平台火焰的火焰尖端运动的幅度与没有火焰旋转的锥形火焰的火焰尖端运动的幅度一样小，而振荡火焰的火焰尖端运动的幅度与没有流动旋转的锥形火焰的火焰尖端运动的幅度相比增加了五倍。火焰尖端振荡幅度的这种显著增加是由于浮力和在刘易斯数影响下火焰强度变化的综合作用。当燃烧器喷射速度和燃烧器转速增加时，保持S=1.04，振荡火焰转变为准振荡火焰。随着喷射速度和燃烧器转速的进一步增大，准振荡火焰向复杂振荡火焰转变。复杂振荡火焰具有混沌特性。这些结果表明，时间序列混沌分析是有用的，以量化复杂的火焰运动的特性。

The dynamic motion of Bunsen flame tip with flow rotation has been investigated experimentally. The premixed mixture (methane/air mixture or propane/air mixture) is injected upwards from a tube burner with inner diameter 12 mm. The burner is rotated with arbitrary rotation speed. Since the honeycomb is installed in the burner, the flow rotation obtained can be assumed as a rigid body rotation. When the burner is not rotated (the Swirl number S=0), well known conical Bunsen flame is formed. When the Lewis number of the premixed mixture is more than unity, the cone shape flame shifts to the oscillating flame at around S=1.04 with increasing S. With further increase in S, the flame shifts to the plateau flame. The frequency of the flame tip motion decreases with increasing S. This is due to a decrease in the axial velocity with increasing the effect of centrifugal force by a flow rotation. The amplitude of the flame tip motion of the conical flame and plateau flame is as small as that of the conical flame without flame rotation, while that of the oscillating flame increases by a factor of five compared to the conical flame without flow rotation. This significant increase in the amplitude of the flame tip oscillation is due to the combined effect of the buoyancy force and the variation in flame intensity under the influence of the Lewis number. When the injection velocity from the burner and the rotating speed of the burner are increased, keeping S=1.04, the oscillating flame shifts to a quesi-oscillating flame. The quesi-oscillating flame shifts to a complex oscillating flame with further increase in the injection velocity and the burner rotating speed. The complex oscillating flame shows chaotic characteristics. These results elucidated that the time series chaotic analysis is useful to quantify characteristics of complex flame motion.