Numerical study of large-scale LNG vapour cloud explosion in an unconfined space

Abstract

Present work aims to predict the explosion characteristics of LNG (Liquefied Natural Gas)-air clouds in a model receiving terminal. Due to the limitations in integral/phenomenological models to include the higher cloud density effects, different terrain, obstacles and wind conditions correctly, advanced 3D CFD (Computational Fluid Dynamics) based techniques are used to model different scenarios of LNG releases. Validation against the similar experiments proved the ability of CFD code to reproduce the results with reasonable accuracy. Simulations revealed that introducing atmospheric boundary layer confines the LNG cloud with a higher level of concentrated vapour densities. The predicted flame speed in LNG-air mixture is found to be almost 35 % higher than that of a corresponding LPG (Liquefied Petroleum Gas)-air mixture leading to a higher explosion overpressure. In all considered worst-cases it is found that the predicted explosion overpressure was above 3 bar and a high value of parameter DPDX (Spatial pressure gradient) was indicating the high likelihood of occurrence of DDT (Deflagration to detonation transition). The outcome of such a detailed study on the occurrence of DDT in an LNG plant is beneficial for setting the gas detectors layout, land-use planning and mitigation measures.