生物质热解气/空气预混爆炸动态传播特性试验研究

Experimental study on unsteady dynamic propagation characteristics of biomass pyrolysis gas/air premixed explosion

利用自行搭建的垂直透明圆管气体爆炸试验平台,通过改变化学当量比、CH4体积分数开展生物质热解气在透明圆管内爆炸动态传播特性研究。结果表明,随着工况条件变化,火焰逐渐呈球状、胞状、湍流等不同火焰结构,并演变为3种火焰传播状态,分别为仅含有初级不稳定现象、次级不稳定现象以及同时出现初级和次级不稳定现象的火焰传播状态,且3种火焰传播状态的火焰锋面及超压曲线出现显著振荡特性。随着化学当量比增大,火焰锋面和超压曲线的振荡幅度更剧烈。当量比在0.9~1.1范围时,火焰锋面速度峰值和超压峰值变化相对较小,但火焰锋面速度峰值临界时间和超压峰值临界时间变化较大。随着CH4体积分数增大,火焰锋面位置振荡强度减弱,但超压曲线振荡却表现出增大趋势。

In this paper,a vertically placed transparent round tube test platform was built.By changing the equivalent ratio and CH 4 volume fraction,flame images and overpressure curves collected by high-speed cameras and overpressure sensors were collected,and factors such as flame structure,flame propagation process,overpressure curve,and overpressure oscillation were compared and explored.In this paper,the unsteady dynamic propagation characteristics of biomass pyrolysis gas exploded in a transparent tube were studied.The equivalent ratio ranges from 0.6 to 1.2,and the volume fraction of CH 4 ranges from 30%to 70%.The results show that with the change in working conditions,the flame presents different propagation states,and the corresponding overpressure curves of the flame are also different.In this paper,three different flame propagation states are found,namely,the flame propagation state with only primary instability,the flame propagation state with both primary and secondary instability,and the flame propagation state with only secondary instability.Besides,it is found that the critical S L of biomass pyrolysis gas is around 40.30 cm/s.In addition,with the increase of equivalent ratio,the time required for the flame to pass from the open end to the closed end becomes shorter,the time of the peak flame front velocity and overpressure peak appears earlier,and the maximum flame front velocity and overpressure also become larger.When the equivalent ratio is 1.2,the maximum flame front velocity and maximum overpressure appear,which are 50.82 m/s and 34.97 kPa,respectively.With the increase of the CH 4 volume fraction,the time required for the flame to pass from the open end to the closed end becomes longer,and the longest flame propagation time(285 ms)occurs when the CH 4 volume fraction is 70%.The peak of flame front velocity and overpressure appears later,and the maximum flame front velocity decreases.But the maximum overpressure shows a trend of increasing.When the CH 4 volume fraction is 70%,the maximum overpressure peak value is 50.21 kPa.