方形容器内掺氢天然气爆炸抑制实验研究

Experimental study on explosion suppression of hydrogen-doped natural gas in a square vessel

为探究掺氢天然气在方形受限空间中的爆炸特性及七氟丙烷/二氧化碳对其爆炸抑制作用,在0.5 m×0.5 m×0.5 m的方形爆炸容器中进行掺氢天然气抑爆实验研究。首先进行掺氢体积分数0%~50%的掺氢天然气爆炸特性研究,结果表明:随着掺氢比例增大,最大爆炸超压和火焰传播速度都呈现上升趋势。随后在甲烷中掺入50%体积分数氢气开展二氧化碳或七氟丙烷抑爆实验,分析了最大爆炸超压、达到最大爆炸超压延迟时间、火焰传播速度等关键爆炸参数在不同抑爆剂体积分数下的演变规律。结果表明:随着抑爆剂体积分数增加,最大爆炸超压快速衰减,达到最大爆炸超压延迟时间延长。高速图像采集结果表明:火焰面拉伸明显,球形火焰传播速度显著减小。选取两种抑爆剂的不同体积分数下抑爆参数值进行对比,发现在二氧化碳体积分数是七氟丙烷2倍情况下,二者对最大爆炸超压的抑制效果相当;在10%体积分数七氟丙烷和20%体积分数二氧化碳作用下均可达到完全抑制,最大爆炸超压分别下降了98.0%和94.4%。两种抑爆剂都具有物理和化学抑爆作用,但七氟丙烷的抑爆效果明显优于二氧化碳。

[Objective]As a green energy resource,hydrogen-doped compressed natural gas(HCNG)is progressively gaining attention.A potential large-scale method of hydrogen transportation is mixing hydrogen with natural gas using the natural gas supply pipeline.However,owing to the difference in the properties of natural gas and hydrogen mixture,leakage and explosion accidents possibly occur during the transportation and utilization of HCNG.To ensure the safe promotion and utilization of HCNG,it is necessary to mix inert gas suppressants into HCNG.Therefore,this study aims to investigate the explosion characteristics of HCNG in a 0.5 m×0.5 m×0.5 m square explosion vessel.The suppressing explosion experiments are conducted using the explosion suppressants carbon dioxide and heptafluoropropane.[Methods]First,a study on the explosion characteristics of HCNG with a hydrogen volume fraction in the range of 0%to 50%is conducted.Subsequently,the HCNG with the 50%volume fraction hydrogen is selected to investigate the explosion suppression based on the suppressants,carbon dioxide and heptafluoropropane.The profiles of critical explosion parameters such as maximum explosion overpressure,maximum overpressure delay time,and flame propagation velocity are analyzed under different volume fractions of suppressants.[Results]Results show that the maximum explosion overpressure and flame propagation velocity increase with increasing hydrogen doping ratio.With increasing volume fraction of suppression gas,the maximum explosion overpressure rapidly decreases,and the delay time to reach the maximum overpressure is prolonged.The high-speed image acquisition results indicate significant stretching of the flame surface.The spherical flame propagation velocity is considerably decreased by the suppressant.Subsequently,the typical volume fraction interval of the two suppressants is selected for comparing their explosion suppression effects.The explosion suppression effects of carbon dioxide and heptafluoropropane on the HCNG are quantified.[Conclusions]The suppression effect of heptafluoropropane is found to be generally comparable with that of carbon dioxide at twice the volume fraction.Complete explosion suppression is attained using 10%volume fraction heptafluoropropane or 20%volume fraction carbon dioxide,and the maximum explosion overpressure is decreased by 98.0%and 94.4%,respectively.The reasons for the suppression effect of heptafluoropropane being considerably superior to that of carbon dioxide are discussed based on the physical and chemical differences between the two suppressants.In particular,heptafluoropropane demonstrates better abilities of oxygen isolation,combination of explosive reactive radicals,and absorption of reaction heat than those of carbon dioxide.The current results can serve as a guide for improving the transportation safety of HCNG.