Entrained air characteristics and coupling mechanism during simultaneous unloading of double material heaps in industrial workshops

Abstract

The simultaneous unloading of double material heaps is a common occurrence in industrial workshops. This process causes dust escape to increase due to the interaction of entrained air between material heaps. In order to understand the coupling mechanism, a mathematical and physical model of the simultaneous unloading process of double material heaps is established in this paper. The DEM-CFD coupling method was validated using experimental data. The effects of material heap height, particle velocity and hopper outlet diameter on the entrained air characteristics of double material heap unloading process are analyzed. The “effective entrainment area” index was proposed for the first time to evaluate the coupling mechanism of entrained air between material heaps. The results indicate that: as the height of the material heap increases, the maximum velocity of the entrained air after collision of particles in different cross-sections gradually decreases from 1.4 to 1 m/s. With the increase in particle velocity and hopper outlet diameter, the maximum velocity of the entrained air generated between the material heaps increases. As the heap height, particle velocity, or hopper outlet diameter increases, the rate of change in entrained air velocity gradually decreases. The diameter of the hopper outlet has the greatest effect on the velocity of entrained air at the vertical axis between material heaps. The diameter of the hopper outlet has the most obvious effect on the height of the vortex core, with a maximum height difference of 33 mm. The effective entrainment area increases with heap height, particle velocity, or hopper outlet diameter, reaching a minimum of 568 mm² at 2 m/s and a maximum of 1884 mm² at 30 mm.