预混火焰胞状不稳定性研究

Study on Instability of Outwardly Propagating Spherical Premixed Flame

采用高速纹影系统和定容燃烧弹对预混球形膨胀火焰的胞状不稳定性进行研究,分析火焰胞状不稳定性的表现、原因以及影响因素。研究结果表明:火焰胞状不稳定性主要指不等扩散不稳定和流体力学不稳定;流体力学不稳定的原因为,曲率的关系会使其流线发散或汇聚,因而相应地降低或增加了流场的速度,其主要影响因素为火焰厚度和密度比,表现为火焰前锋面产生裂纹随后出现规则的胞;不等扩散不稳定的原因为前锋面包络的控制体由于热质不等扩散的缘故,主要影响因素为刘易斯数,表现为火焰表面布满不规则的胞。

A research on cellular instability of outwardly propagating spherical premixed flame was carried out on constant volume combustion bomb with schlieren method by using high speed camera and data acquisition. The developing process, causes and influ- ence factors of flame cellular instabilities was analyzed. The results showed that the cellular instabilities mainly included unequal diffu- sion instability and hydrodynamic instability. The cause of hydrodynamic instability was that stream lines integrated or diverged due to curvature reason, so the velocity of the flow field increases or decreased. The flame thickness and density ratio of burned to unburned zone were the main influence factors of hydrodynamic instability. The cracks and regular distortions of the flame surface was the main phenomenon. The cause of unequal diffusion instability was that thermal-mass unequal diffusion of the flame front control volume. The Lewis number was the main influence factor, and the phenomenon of unequal diffusion instability was un-regular distortions of the flame surface.