Experimental study on combustion and explosion characteristics of hydrogen-air premixed gas in rectangular channels with large aspect ratio

To assess the consequences of hydrogen leakage, subsequent combustion, and resulting explosions within confined spaces such as ducts and channels and to reveal the combustion and explosion characteristics and influencing mechanisms of hydrogen, a rectangular test tube with a pressure rating of 10 MPa and a large aspect ratio of 120 was designed. The purpose of this study was to simulate the flame propagation and overpressure characteristics of hydrogen -air mixtures ignited in rectangular channels with large aspect ratios under atmospheric pressure. The effects of the hydrogen volume fraction (20%-45 %) and pipe blockage ratio (0/0.4) on the hydrogen combustion and explosion processes were analyzed. The results show that, under both smooth tube and obstacle installation conditions, increasing the hydrogen volume fraction from 20 % to 25 % resulted in 367.6 % and 63 % increases in explosion overpressure, respectively. The presence of obstacles considerably increases the explosion overpressure, and the position of the highest overpressure moves from downstream to upstream of the explosion outlet. Within the range of 25%-45 % hydrogen volume fraction, the overpressure exceeded the theoretical detonation pressure. At a hydrogen volume fraction of 35 %, the highest overpressure reached 2899 kPa, which was approximately twice that of the smooth tube. At a hydrogen volume fraction of 40 %, the maximum range of overdriven detonation was observed in the tube.