Estimation of explosion overpressure associated with background leakage in natural gas pipelines

Gathered natural gas (NG) clouds caused by background leakage from buried municipal gas pipelines or those used by gas stations pose potential threats to humans and the environment. If the leaked gas cloud (GC) ignited, significant injury caused by the explosion could occur. Therefore, the influences of the outside overpressure on the outside and inside of the building should be predicted to evaluate the damage level. Moreover, when the generated explosion overpressure is calculated, it is generally assumed that the entire GC is ignited, and its shape is hemispheric, which need further study and confirmation for background leakages. In this work, the actual explosion volume of a cubic leaked NG cloud is determined by establishing a generation model for the overpressure peak value with the help of numerical simulations and experiments, and the overpressure distribution outside and inside the building is evaluated by establishing a propagation model, using numerical simulations. The results show that for a cubic NG cloud, the actual explosion volume is 0.07 times the total volume of the leaked GC, by which the peak generation can be accurately predicted with errors smaller than 15%. Considering the influences of the building on the peak, the positive and negative peak outside and inside of the building can also be evaluated with small errors, which helps to identify safe places for people facing a VCE explosion.