Numerical simulation by the molecular collision theory of two-phase mixture explosion characteristics in closed or vented vessels

The aim of this work consists in presenting a simple modelling (the molecul ar collision theory), easily usable in an industrial environment in order t o predict the evolution of thermodynamical characteristics of the combustio n of two-phase mixtures in a closed or a vented vessel. Basic characteristi cs of the modelling have been developed for ignition and combustion of prop ulsive powders and adapted with appropriate parameters linked to simplified kinetics. A simple representation of the combustion phenomena based on ene rgy transfers and the action of specific molecules is presented. The model is generalized to various mixtures such as dust suspensions, liquid fuel dr ops and hybrid mixtures composed of dust and a gaseous supply such as metha ne or propane in the general case of vented explosions. The pressure ventin g due to the vent breaking is calculated from thermodynamical characteristi cs given by the model and taking into account, the mass rate of discharge o f the different products deduced from the standard orifice equations. The a pplication conditions determine the fuel ratio of the used mixtures, the na ture of the chemical kinetics and the calculation of a universal set of par ameters. The model allows to study the influence of the fuel concentration and the supply of gaseous additives, the influence of the vessel volume (24 00l less than or equal to V-b less than or equal to 250000l) and the influe nce of the venting pressure or the vent area. The first results have been c ompared with various experimental works available for two phase mixtures an d indicate quite correct predictions.