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To reduce the injury caused by hydrogen explosion accident, numerical simulation study is carried out to study the characteristics of hydrogen explosion in confined space under different venting conditions. The results show that in the process of the flame passing through the side vent, the position of the side vent can affect the leading role of the side venting on the flame front distortion. When the flame front is in front of the side vent, the flame is accelerated by the traction of co-flow. When the flame front passes through the side vent, the flame propagation speed under various working conditions is greatly reduced due to the combined action of reflected wave and vertical flow field. When the front of the flame is located behind the side vent, the flame propagation speed fluctuates greatly only when the side vent is 1 m away from the ignition end, and the flame propagation to the end of the pipe is kept at a low speed in other venting conditions. The pressure relief effect of the side vent is positively related to the size of the side vent. When the side vent is located in the middle of the pipe, the pressure relief effect is the best. When the size of the vent is small, the pressure relief effect is greatly affected by the location of the vent. The peak overpressure in h-1-40, h-3-40, h-5-40 decreases by 49.21%, 83.89%% and 78.03%, respectively. With the increase of the size of the side vent, the pressure relief effect of the side vent is almost not affected by its size. The peak overpressure in H-1-80, H-3-80, H-5-80 only decreases by 90.17%, 94.99% and 92.78%, respectively. [ABSTRACT FROM AUTHOR]

An experimental apparatus was built to study the external pressure caused by vented explosions of methane and air mixtures. In some circumstances, two peak points of external pressure induced by vented explosion appear. One of the peaks is caused by the vented flow from the vessel while the other one is due to the vented flow from the vessel or external explosion. Both the maximum external pressure and pressure rising rate increase with initial pressure, explosion venting pressure and vent diameter of the vented vessel. The maximum external pressure and pressure rising rate decrease with the volume of the vessel. The maximum pressure and the maximum pressure increase rate occur when the methane concentration is 9.5%. Compared with explosion outside one single big vessel, explosion outside the connected vessels is more severe. The external pressure caused by ignition in the center of the small vessel is higher than that in the center of the big vessel while the external pressure rising rate caused by ignition in the center of the small vessel is lower than that in the center of the big vessel. © 2014 American Institute of Chemical Engineers Process Saf Prog 33: 385-391, 2014 [ABSTRACT FROM AUTHOR]