LAYERED FUEL AIR MIXTURES EXPLOSION IN LOW-STRENGTH ENCLOSURE

The accidental release of fuel in a confined or partially enclosures leads to the formation of flammable clouds at variable concentration. Eventually, concentration gradients and stratified (to the floor) or layered (to the ceiling) flammable clouds are formed. In low-strength enclosures (buildings or equipments) even very small quantities of fuel can be able to produce overpressures sufficient to determine significant explosion hazard. Few indications are given in the literature for the vent sizing in such cases. Moreover, the entire combustion phenomenon is poorly understood. A CFD code for the simulation of stratified methane-air explosion is adopted to compute the relevant parameters to determine the explosion hazard from small quantities of fuel. The dependence of the pressure rise and the rate of pressure rise with respect to the partial filling of the entire volume with a stoichiometric homogeneous mixture of methane-air have been computed in enclosures of different volume. A theoretical analysis of the results has allowed the determination of a possible correlation for the deflagration index KG with respect to the partial filling parameter, to be used in the well-known correlations for vent sizing.