Periodic motion of a Bunsen flame tip with burner rotation
Periodic motion of a Bunsen flame tip with burner rotation
复制标题
本生火焰尖端随燃烧器旋转的周期性运动
DOI：
10.1016/s0010-2180(03)00082-8
复制
发表时间：
2003
影响因子：
4.4
通讯作者：
R. Cheng
中科院分区：
文献类型：
--
作者：
H. Gotoda;K. Maeda;T. Ueda;R. Cheng
在正常重力和微重力条件下，对燃烧器旋转对预混本生火焰形状和动力学的影响进行了实验研究。CH 4-空气和C3 H8-空气的混合物以平均流速U = 0.6 m/s从燃烧器管排出。燃烧器管旋转至1400 rpm（涡流数S = 1.58）。在刘易斯数Le > 1的条件下（富CH 4-空气和贫C3 H8-空气混合物），锥形火焰和平台火焰之间形成大振幅的振荡火焰。而对于Le ≤ 1的混合气（贫甲烷-空气和富丙烷-空气），在相同的旋流数范围内，形成不对称、偏心或倾斜的火焰。在微重力条件下，振荡火焰没有形成，表明振荡是由浮力引起的不稳定性与热产品和环境空气之间的不稳定界面。当S = 0.11时，火焰闪烁频率ν对燃烧器旋转不敏感< 0.11. For S >，ν随S的增大而线性减小。当S超过0.11时，由于流动发散，沿中心线uj，m的轴向平均速度沿着有一个极小值，它与ν成线性关系。这一结果表明，uj，m直接控制振荡频率。当S接近1时，与锥形火焰的闪烁幅度相比，火焰振荡幅度增加5倍。这是伴随着一个滞后变化的火焰曲率从正到负和热扩散区的厚度从小到大的变化。当S > 1.3时，平台火焰具有与S = 0时相同的小闪烁幅度。结果表明，离心力和浮力的相互作用以及刘易斯数的非统一效应对火焰尖振荡的放大起着重要的作用。
Effects of burner rotation on the shapes and dynamics of premixed Bunsen flames have been investigated experimentally in normal gravity and in microgravity. Mixtures of CH4-air and C3H8-air are issued from the burner tube with mean flow velocity U = 0.6 m/s. The burner tube is rotated up to 1400 rpm (swirl number S = 1.58). An oscillating flame with large amplitude is formed between a conical-shape flame and a plateau flame under the condition of Lewis number Le > 1 mixtures (rich CH4-air and lean C3H8-air mixtures). In contrast, for Le ≤ 1 mixtures (lean CH4-air and rich C3H8-air), asymmetric, eccentric flame or tilted flame is formed under the same swirl number range. Under microgravity condition, the oscillating flames are not formed, indicating that the oscillation is driven by buoyancy-induced instability associated with the unstable interface between the hot products and the ambient air. The flame tip flickering frequency ν is insensitive to burner rotation for S < 0.11. For S > 0.11, ν decreases linearly with increasing S. As S exceeds 0.11, a minimum value of axial mean velocity along the center line uj,mdue to flow divergence is found and it has a linear relationship with ν. This result shows that uj,mhas direct control of the oscillation frequency. When S approaches unity, the flame oscillation amplitude increases by a factor of 5, compared to the flickering amplitude of a conical-shape flame. This is accompanied by a hysteresis variation in the flame curvature from positive to negative and the thermo-diffusive zone thickness varying from small to large. With S > 1.3, the plateau flame has the same small flickering amplitudes as with S = 0. These results show that the competing centrifugal and buoyancy forces, and the non-unity Lewis number effect, play important roles in amplifying the flame-tip oscillation.