Study of the severity of hybrid mixture explosions and comparison to pure dust-air and vapour-air explosions

The explosion behaviour of heterogeneous/homogeneous fuel/air (hybrid) mixtures is here analysed and compared to the explosion features of heterogeneous fuel/air and homogeneous fuel/air mixtures separately. Experiments are performed to measure the pressure history, deflagration index and flammability limits of nicotinic acid/acetone/air mixtures in a standard 20 L Siwek bomb adapted to vapour/air mixtures. Literature data are also used for comparison. The explosion tests performed on gas/air mixtures in the same conditions as explosion tests of dust/air mixtures, show that the increase in explosion severity of dust/gas/air mixtures has to be addressed to the role of initial level of turbulence prior to ignition. At a fixed value of the equivalence ratio, by substituting the dust to the flammable gas in a dust/gas/air mixture the explosion severity decreases. Furthermore, the most severe conditions of dust/gas/air mixtures is found during explosion of gas/air mixture at stoichiometric concentration.