Effects of circular obstacle size on shock wave and spontaneous ignition following sudden release of pressurized hydrogen

Safety concerns remain a significant challenge to the sustainable development and application of hydrogen energy, particularly due to hazards associated with the accidental release of pressurized hydrogen, especially the spontaneous ignition of hydrogen leakage. This study delves into the effects of obstacles within a tube on the features of the shock wave, overpressure, and self-ignition during the sudden release of high-pressure hydrogen. It is found that the obstacle significantly changes the shock wave dynamics, generating reflected waves that propagate upstream and induce the sudden increase in the upstream overpressure. Concurrently, a notable decrease in overpressure is observed downstream the obstacle. These changes are contingent upon the diameter of the obstacle's hole. Specifically, a smaller diameter corresponds to a more intense reflected shock wave and a pronounced reduction in downstream overpressure. Additionally, reflections can trigger spontaneous ignition, with the ignition location shifting upstream in response to the obstacle's position. Close proximity to the obstacle can also lead to intensified flame burning in localized regions. However, flame intensity diminishes rapidly after passing the obstacle, increasing the likelihood of flame extinguishment both within and outside the tube. These findings provide valuable insights for advancing safety measures and design strategies in hydrogen energy applications.