Effects of hydrogen status and compartment structure on hydrogen explosion propagation in utility tunnels

To ensure the safe application of hydrogen energy in utility tunnels, it is crucial to study the propagation process of hydrogen explosion. In this paper, the explosion propagation process of non-premixed hydrogen-air mixture in gas compartments with different bending angles and with various hydrogen status was investigated. By analyzing overpressure, flame evolution state and flame velocity, the characteristics of the hydrogen explosion in utility tunnels were revealed. The results show that the explosion overpressure, flame velocity and flame brightness all first increase and then decrease with the increase of hydrogen concentration, due to the suppression effects in both fuel-lean and fuel-rich environments. Moreover, it was found that, in 90 degrees, 120 degrees and 150 degrees bending compartments, the maximum overpressure values of hydrogen were respectively 28.52%, 3.52% and 8.53% higher than that in the straight compartment, while the average flame velocity values were respectively 34.19%, 11.96% and 34.13% lower than that in the straight compartment. This was closely related to the intense reflection of shock waves in the bending section, where the accumulation of reflected shock waves not only increased the maximum overpressure but also slowed down flame velocity. This research provides valuable guidance for the design and safety management of hydrogen transportation in utility tunnels and similar confined spaces.