氢气对预混甲烷/空气燃爆过程的影响

Impact of hydrogen addition on the premixed methane/air deflagration process

为研究氢气的加入对不同体积分数甲烷/空气预混爆炸过程影响的规律,在尺寸为150 mm×150 mm×1 000 mm的管道中通入体积分数为8%、9.5%和11.5%的甲烷/空气预混气体,然后加入一定体积分数的氢气。氢气所占体积分数分别为0、0.74%、1.48%、2.95%、4.40%。分别对加入不同体积分数的甲烷爆炸过程中爆炸压力、火焰图像和爆炸温度进行测量、分析。结果表明:只有在8%纯甲烷爆炸时能够形成完整的郁金香火焰。8%和9.5%甲烷体积分数试验中,氢气的加入使火焰面由上下对称变得不对称,火焰阵面上移,火焰速度加快;爆炸中的最大超压增大并且最大超压时刻点提前。在11.5%的甲烷加氢试验中,随加氢量增加,爆炸压力、温度、火焰速度分别略微降低。这表明氢气的加入在体积分数为8%的爆炸反应中较大地促进了反应,而体积分数为11.5%时加氢后爆炸反应减弱。通过理论分析计算了半封闭管道中体积分数为9.5%甲烷爆炸温度和实测温度之间的差异。爆炸压力和温度的变化能很好地反映加入氢气对甲烷爆炸的影响。

This paper is aimed to introduce the experimental results on the deflagration characteristics of different volumes of fraction premixed methane-air in the duct. In order to study and determine the extent and regularity of the reaction process under the influence by adding small amounts of hydrogen,we have managed to conduct an experiment with a tube with its inner size of150 mm × 150 mm × 1 000 mm. When filling the methane-air premixed gases in with the different volume percentages of 8%,9. 5% and 11. 5%,the tube should be added by part of hydrogen in different percentages as shown respectively below： 0. 0%,0. 74%,1. 48%,2. 95% and 4. 40%. When all of the gases added were mixed uniformly,the premixed gas is likely to get ignited and then the explosion data can be recorded. And,then,it would be possible for the explosion pressure,the flame image and explosion temperature to be measured and analyzed when the the explosion process is going on. The experimental results we have gained show that only when the added pure methane reaches 8%and 9. 5%,and forms a complete ＂ tulip＂ flame,the front of the flame would turn to be asymmetrical and tends to go upward.With the increase of volume fraction of added hydrogen,the maximum explosion overpressure increases,too,so that the moment of maximum pressure may arrive at in advance. In our experiments with 11. 5% concentration rate of methane participant,with the volume fraction of the explosion pressure,temperature and flame speed slightly decrease with the increase of the volume of hydrogen,respectively. This indicates that the hydrogen additions has promoted the reactions in the volume fraction of 8% and 9. 5%,thus weakening the explosion reaction of methane fraction by11. 5%. In the semi-closed duct of 9. 5% methane explosion,there exists some difference between the theoretical temperature and the actual experimental temperature,which change can clearly reflect the influence of the hydrogen addion to the methane explosion. And,consequently,the flame can be expected to be speeded up with the addition of hydrogen.