Experimental Investigation And Numerical Simulation Into Characteristics Of Aluminum Dust Explosion

It is significative to study Aluminum dust explosion venting mechanism and characteristics for the industrial dust explosion protection. At present, a lot of explosion venting research has been carried out, there is no literature to report the comparative study among confined space, ductless and duct venting explosion in the same device. In addition, the maximum pressure Pmax and the maximum rate of pressure rise (dp/dt)max were paid much attention. The description of its internal mechamism and the development of the flame and preesure wave depend on the numerical simulation.Based on the above situlation, this paper did lots of experiment of the Aluminum dust explosion venting and meanwhile made use of CFD software Fluent to simulate the process. The work and conclusions of this paper are as follows.(1) 1.3L Hartmann device was established and improved. Aluminum dust explosion in the confined space, ductless and duct venting explosion were researched. The factors of the maximum pressure Pmax and the maximum rate of pressure rise (dp/dt)max were obtained.(2) The numerical models of the confined space explosion, ductless venting explosion and duct venting explosion, control equations of the fluid dynamics and combustion were estanlished. The method using the finite volume discrete equations is proposed. The blowing dust, confined space explosion and venting explosion process were respectively simulated.The independence analysis of the four kinds of number grids 3 mm×3mm,2mm×2mm,1mm×1mm wrer conduced adopted. Considering the accuracy and economics, 1mm×1mm grid was used to simulate. It is determined to be feasibility to simulate the process of confined space, ductless and duct venting explosion.(3) It is found in the experiment that the effect of blowing dust in Hartmann bomb isn't good, which results in Aluminum dust can't adequately combust. Because of the dust incomplete combustion, The best optimum dust concentration from the experiment 500 g·m-3 is in the poor oxygen area. Pmax and (dp/dt)max decrease with dust particle diameter dp increasing due to the micron dust gravitation effect. Dust diameter effect to Pmax and (dp/dt)max isn't obvious when dust particle diameter is up to nanometer class.It is found in the simulation that the combustion of the Aluminum dust is a typical deflagration combustion process in 1.3L Hartmann bomb. Compared with the gas balsting, due to the interaction of dust and turbulence, the flame shape is very irregular and the combustion is more complex. The dust properties are gradually close to the gas phase when dust diameter is smaller or nanometer class. Therefore, using two-phase flow model to simulate the discrete phase exists evident error.(4) It is found in the experiment of the ductless venting process that Pmax increases with venting opening pressure increasing. The smaller venting diameter and the thinner venting membrane, the bigger (dp/dt)max. Compared to the confined space explosion, Pmax and (dp/dt)max of ductless venting explosion is decreasing as the combustible medium is less because of venting. The best optimum dust concentrationis still 500 g·m-3.It is found in the simulation that the dust is well-proportioned when raising. After ignition, the flame surface spreads to the Hartmann both sides in the form of the irregular shape. The venting hatch is opening at opening pressure value and the pressure wave circularity spreads outwards to form pressure relief channel.(5) It is found in the experiment that venting duct can discharge medium effectively, but intensify the pressure in Hartmann bomb. The pressure wave propagation velocity and intensity in the venting duct are gradually weakened. With the venting opening pressure Pv increasing, Pmax of both Hartmann bomb and venting pipe increase.It is found in the simulation that compared to the pressure wave, the flame promulgation is lag. The venting hatch played strong disturbance on the flame shape when the flame was up to the venting opening. The front flame changed cuniform and entred the venting channel. Compared with the ductless venting simulation, the disturbance of the duct venting is more strong and the values of Pmax are bigger.