富氧条件下甲烷爆燃火焰传播特性试验研究

Experimental study on flame propagation characteristics of methane deflagration under the oxygen-enriched condition

为了研究富氧条件下甲烷爆燃火焰的传播特性,自搭建了一套半开管道的试验装置,结合高速摄影机,通过试验研究了不同富氧系数及点火位置条件下甲烷的燃烧特性。结果表明:随富氧系数增大,火焰的传播速度明显上升;同时在火焰传播过程中,火焰结构的变化会导致火焰的传播速度发生变化。调整点火位置到试验管道的中部,火焰的传播会发生振荡,随富氧系数增大,火焰的振幅及每次振荡传播的距离增大,但火焰的振荡频率变化不大。

This paper studied the effects of oxygen enrichment coefficient and ignition position on the flame propagation velocity of methane deflagration in a semi-open pipe.The experimental system used in this paper is composed of a combustion pipe,a high-speed camera,a gas distribution system,and an ignition device.The combustion pipe is made of transparent plexiglass,placed horizontally and perpendicular to the camera.The left side of the pipe is closed by a stainless steel plate,and there is an air inlet on it.The right side of the pipe is closed by PVC film,which makes the pipe a closed space in the inflation stage.During the combustion process,the PVC film on the right side breaks and forms an explosion vent.Besides,the ignition devices are respectively arranged on the closed surface of the left side of the pipeline and in the middle of the pipe to study the influence of different ignition positions on the flame propagation velocity.After connecting the rear pipe of the experimental platform,the combustion pipe is inflated according to the requirement of gas equivalent ratio and then ignited.The whole flame propagation process is recorded by a high-speed camera.The experimental results show that when the ignition position is on the left side and the oxygen enrichment coefficient is 0.21,the flame propagation speed increases first,then decreases for a while,and increases again.The reason for this phenomenon is related to the tulip flame structure and the heat transfer between the flame and the wall.With the increase of oxygen enrichment coefficient,the flame propagation speed increases significantly.Meanwhile,the tulip flame structure disappears,and the flame propagation speed increases gradually.When the ignition position is in the middle of the pipe,the combustion of methane oscillates obviously due to the combustion-induced Rapid Phase Transition.The amplitude of flame oscillation increases with increasing the oxygen enrichment coefficient while the frequency of flame oscillation does not change.