Computational Study of High-Pressure Hydrogen Storage Vessel Explosion and the Blast Wall Effects on Blast Pressure Mitigation

Abstract

High-pressure compressed hydrogen storage is one of the common and simple methods to store hydrogen gas for transport applications. The explosion risk is a significant concern in implementing high-pressure storage technology. Understanding the blast wave dynamics of high-pressure storage vessel explosion and an effective mitigation technique to reduce the blast wave impact on the surrounding humans and structures is crucial. The development of computational fluid dynamics (CFD) codes has offered a significant advantage in investigating hazardous accidents safely. Thus, a computational study has been performed to investigate the explosion dynamics of high-pressure hydrogen storage vessels and the effects of blast wall structures on blast pressure mitigation. A density-based compressible reacting flow numerical approach was implemented in an OpenFOAM CFD code to investigate the explosion dynamics of high-pressure hydrogen vessels. Initially, numerical approach prediction performance was validated by a numerical simulation for the previous experimental study of sudden failure of a 35 MPa, 72.4 L high-pressure hydrogen storage vessel in an open environment. The k-ω SST turbulence model, eddy dissipation concept (EDC) combustion model and the finite volume discrete ordinate method (FvDoM) radiation model were employed in the numerical simulation to resolve the turbulent combustion reaction and the thermal radiation effects in the explosion. The numerical simulation reproduced the blast over-pressure propagation and fireball formation reasonably. The numerical predictions of transient over-pressure, the maximum over-pressure and impulse along the radial and axial distances showed reasonable agreements with the experimental data. The performance plots showed that the accuracy of the numerical predictions is within the acceptable range. A worst-case scenario of a 95 MPa, 184 L hydrogen vessel explosion was considered to perform the numerical investigation using the validated numerical approach. The numerical simulation reproduced blast wave dynamics such as incident, reflected shock waves, Mach stem, triple point, and secondary blast wave. The maximum over-pressure and impulse predictions were compared against the analytical calculations and showed an exponential decay in the axial and radial directions. The temperature and hydrogen mass fraction distributions primarily occurred in the radial direction than in the axial direction. The blast wave mitigation performance of different blast wall shapes was investigated for the 95 MPa, 184 L hydrogen vessel explosion scenario. Flat, slanted, T-shape and Y-shape walls mitigation performance was investigated in this study. The blast walls were assumed to be non-deforming structures with dimensions of 10 m wide, 2 m high and 0.20 m thick and located 5 m away in the axial direction of the hydrogen vessel. The mitigation performance of different blast wall shapes was evaluated by comparing the maximum over-pressure and impulse. The numerical simulations provided valuable insights into blast-overpressure interaction with different blast wall structures and their mitigation effects on over-pressure and impulse decay behind the blast wall. The maximum over-pressure and impulse behind the blast wall were decreased significantly compared to the case without the blast wall. However, behind the blast wall, no significant difference was found in the over-pressure mitigation performance of each blast wall shape. A flat wall mitigated the blast impulse more effectively behind the blast wall. The maximum over-pressure and impulse relation behind the blast wall showed that blast wall structures could significantly decrease the damage to humans and civil structures.