Modelling and Scaling of Fireballs from Single -and Two-phase Hydrocarbon Releases

Numerical modelling of evolution, behaviour and radiation of fireballs occurring in the atmosphere as a result of hydrocarbon fuel releases is reported. Transient reacting flows developing upon vertical outflows are considered for the cases of single-phase releases (relevant to discharge of hydrocarbons in the case of low storage overpressure) and two-phase releases (relevant to discharge of pressure-liquefied hydrocarbons). The calculations performed are for methane and propane fireballs in a wide range of fuel masses from 1 g up to 1000 kg. The scaling of fireball size and lifetime as functions of fuel mass and release velocity is studied. Unified description of singleand two-phase cloud burning times in terms of Froude number is given. The internal structure of fireballs of different linear scales is obtained. The radiation characteristics of small (optically thin) and large (optically thick) fireballs are compared. Good agreement between the calculated results and experimental data available is demonstrated.