The Mechanical Characteristics Of Al-dust/gas Explosion Under Flow Stage

With the widespread use of organic solvents and dust in the industry production, the explosions of combustible gas(vapor)/dust multiphase mixture are increasing gradually. Hybrid mixture typically refers to dust/air mixtures containing flammable gas or vapors. The turbulence, various components, concentration and composition of mixtures all have important influences on hybrid explosion and complicate explosive characteristics. In order to provide theoretical basis for industrial production, accident prevention, safety assessment and accident investigation, in the work reported here, the dispersal process of aluminum dust and the explosive process of aluminum dust/air mixtures, JP-10 vapor/air mixtures, IPN vapor/air mixtures, JP-10 vapor/IPN vapor/air mixtures, JP-10, and aluminum dust/JP-10 vapor/IPN vapor/air mixtures in a 20 L spherical confined chamber were numerically simulated by the computational fluid dynamic software ANSYS-FLUENT.By numerical simulation, we found the variation regularity of turbulence and concentration of aluminum dust in time and space dimensions, and revealed the interrelation between blowing pressure, particle size and turbulence distribution. Under different blowing pressure, turbulence rapidy rises to a peak then descreases sharply, and the greater the blowing pressure is, the higher the peak turbulence reachs in blowing period; but turbulence decreases slowly, and the difference of each turbulent kinetic energy corresponding different blowing pressure is quite modest in static period. Nevertheless, particle size has litter impact on turbulence in a whole period. The concentration distribution of aluminum dust can hardly be uniform and at the calculation conditions of this paper, it can be relatively uniform in 60 ms to 120 ms period. These researches can provide a basis to determin ignition time and analyze result of the dust explosion experiment.The coupling effects of turbulence and concentration on aluminum dust explosion parameters were obtained by simulating aluminum dust/air explosion in flow state. The optimum ignition delay time increases with the increasing of concentration of aluminum dust at low concentration, but at high concentration, it remains unchanged. The study lays a key foundation for quantitatively investigating the influence of turbulence on dust explosion.We found the pmax of JP-10 vapor explosion was obviously higher than IPN vapor, but the(dp/dt)max was one magnitude lower by simulating the explosions of JP-10 vapor/IPN vapor/air multicomponent mixture. The pmax rises with the rising of JP-10 vapor proportion in the mixture. These defined optimal direction and method for fuel design.The variation regularity of explosion pressure of aluminum dust/JP-10/IPN vapor/air mixtures were studied by changing concentration and dust-gas mass ratio. The study indicates that the influence of dust-gas mass ratio depends on concentration. When concentration is relatively low, the pmax and(dp/dt)max of hybrid mixture decreases with the rising of dust-gas mass ratio; otherwise, the pmax increases with the rising of dust-gas mass ratio, and the(dp/dt)max rises first, then falls.