Influence of geometrical shapes on unconfined vapor cloud explosion

Abstract

The vapor cloud explosion (VCE) usually results in large financial and environmental damages. There are many methods to evaluate the consequences of VCE and one of them is the TNO Multi-Energy method (MEM). In the practical applications, the MEM has some weaknesses. For example, it is assumed that the explosion model is hemispherical, which is usually inconsistent with the actual situations. In order to examine the effect of the geometrical shapes on explosion characteristics, a constant volume of clouds with different height-width ratios and length-width ratios were studied. For the vapor cloud with a given volume (32 m3), the geometrical shapes have a great influence on the explosion overpressure, but little on the explosion temperature. When the height-width ratio is 0.5 (the corresponding geometrical shape is 4 m × 4 m × 2 m), the explosion peak overpressure reaches the maximum of 1.57 bar, which is 3.6 times of that (0.44 bar) for the 2 m × 2 m × 8 m vapor cloud. For a constant volume of clouds with the four different height-width ratios in this paper, the MEM predictions correspond to three different initial explosion strengths. As effect of the geometrical shapes on the vapor cloud explosion was not taken into account in the MEM, its predicted results have a greater deviation, especially in the far field. For the scenarios calculated in this study, the relative error for the explosion overpressure predicated in the MEM reaches 150%.