NaHCO_3抑制瓦斯爆炸火焰与压力的耦合分析

Coupled relationship between flame and overpressure of gas explosion inhibited by NaHCO_3

为研究粉体作用下瓦斯爆炸火焰与压力的耦合规律,在5 L石英管道中开展了不同浓度NaHCO_3抑制瓦斯爆炸的实验。结果表明:随着粉体浓度的升高,瓦斯爆炸压力波形逐渐由单峰曲线向双峰曲线过渡;高浓度粉体抑爆下,单位体积内粉体小颗粒较多,小颗粒快速分解抑制火焰传播,使粒径较大的粉体有较长的时间吸热分解,进一步抑制火焰的发展;火焰传播中后期,大颗粒粉体沉降造成空间内粉体分布不均,形成粉体浓度较低的燃烧区、浓度较高的粉体沉降汇集区和低浓度的小颗粒悬浮区,影响粉体中后期的抑爆效果;火焰前锋速度与爆炸超压随时间变化曲线的线形相似,火焰前锋速度能一定程度上反映管内燃烧强度,但瓦斯爆炸超压的升降并不完全取决于火焰前锋速度的变化;当火焰前锋速度较大时,短暂的速度降低不会立刻造成爆炸超压的减小。

To study the coupled relationship between the flame propagation and the pressure built-up of gas explosions,the test was carried out in a 5 L quartz duct with different concentrations of NaHCO3.The results showed that the pressure waveform of gas explosions gradually changed from a single-peak curve to a bimodal curve with the increase of the mass concentration.Moreover,there are more small particles per unit volume as the suppressant concentration was large enough,which would inhibit the flame propagation firstly and then prolonged the endothermic time of larger powders,making the flame front be further inhibited.In the middle and late stages of the flame propagation,the settlement of large particles resulted in the uneven distribution of powders in space,which significantly affected the inhibition efficiencies.The distribution of powders in the duct can be divided into three regions:the combustion zone with low powder concentration,the sedimentation and collection zone of large particles with high mass concentration and the suspension zone of small particles with low powder concentration.The time dependence of the flame front velocity was similar to that of overpressure.Although the flame front velocity can reflect the intensity of the combustion to some extent,the rise and fall of the overpressure cannot determine entirely by the trend of the flame front velocity.The explosion overpressure wouldn’t decrease immediately with the transient reduction of the flame front velocity when the flame front velocity was large enough.