Computational fluid dynamics modeling of vapor cloud explosion, cold bleve and hot bleve in a large scale tunnel

Abstract

In the present work, Computational Fluid Dynamics (CFD) explosion simulations are performed in a large scale tunnel. The length of the tunnel is approximately equal to one kilometer. Three different cases of explosion are studied: Vapor Cloud Explosion (VCE), Cold BLEVE (Boiling Liquid Expanding Vapor Explosion) and Hot BLEVE. The main purpose of this study is the calculation of the generated overpressures inside the tunnel and the comparison of the pressure dynamics among these type of explosions. Realistic scenarios are chosen for each explosion based on the traffic of the tunnel. In the Vapor Cloud Explosion case, the release and dispersion of 23100 kg propane into the atmosphere are simulated in order to calculate the concentration distribution in the tunnel. Both external wind and piston effect due to vehicles’ movement was taken under account in the dispersion process. Then the mixture is ignited and the deflagration process is simulated in order to calculate the generated overpressures. In the Cold BLEVE case the total loss of confinement of a 29 m3 high pressure (57 bar) carbon dioxide storage tank is simulated, whereas in the Hot BLEVE case the total loss of confinement of a 46 m3 propane storage tank (at 18 bar) is considered. The total loss of confinement of the tanks lead to a violent expansion due to evaporation. As a result high overpressures are generated. The transient three dimensional Navier-Stokes equations of the multispecies mixture along with the continuity equation, the conservation equation of species and the energy equation are solved. Turbulence is modelled with the standard k-ε model. In the Vapor Cloud Explosion case a Multi- Phenomena turbulent burning velocity combustion model is used. In the Hot BLEVE case, fire is modeled using the Eddy Dissipation Concept (EDC) model. The simulation results reveal that the modeling approach that is used is capable of reproducing physical realistic results. Differences in pressure dynamics among the scenarios are revealed due to the different physics of the explosions.