旋转流中预混合火焰高速传播现象—II.点火位置与燃烧过程

High Speed Propagation of Premixed Flame in Swirling Flow—II.Ignition Position and Process of Combustion

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上,围绕燃烧器的点火特性,对旋流场中的点火位置和稳定火焰形成进行了数值分析.结果表明,不适当的点火位置会影响稳定火焰的形成,在相同的燃烧工况下,在流场中点火位置不同,火焰的发展出现不同的趋势.在靠近中心轴附近的低速区点火时,火焰能够稳定;在靠近管壁的高速区点火时,撤离点火源后,火焰吹熄.本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.

The previous research of vortex-bursting shows that in the swirling condition, premixed methane-air combustion can be stable in the high inlet velocity gas. Based on the investigation of both the combustion efficiency of swirling premixed combustor and the effect of distribution of inlet velocity on enhancement of combustion efficiency in the previous paper, the numerical research of ignition position effect on the flame stability is carried on in this work. It is found that inappropriate ignition position can affect the process of flame evolution. Under the same condition, development of combustion will evolve in different trends if the flame is ignited at different positions in the flow field. A non-dimensional parameter is put forward for describing the ignition position. When ignition position is located on the axis and low velocity area of tube, the resulting flame will be stable. Instead, when ignition position is in high velocity area, the flame is finally blown out. In this work, the useful theoretical and applicable results for enhancing stability of premixed combustion are achieved.