Effect of Passive Inserts on the Granular Flow from Silos Using Numerical Solutions

Author： DING S. DE SILVA S. R. ENSTAD G. G.

ISSN： 0272-6351

Source： Particulate Science and Technology, Vol.21, Iss.3, 2003-07, pp. : 211-226

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Abstract

Experimental investigations indicate that placing a passive insert in a silo is a method for influencing the discharging flow pattern. These inserts have consisted of an inverted cone, a cone-in-cone, and a double cone. However, providing unequivocal guidelines on where those inserts should be placed for an optimum effect has not been possible experimentally. A numerical approach was therefore developed to predict material flow in the presence of such inserts in silos. Simulation results showed that all these inserts could make a funnel-flow silo perform in mass flow under certain circumstances if positioned correctly. The inserts should be installed at higher levels close to the transition rather than at lower positions close to the outlet, especially with the cone-in-cone insert and the inverted inserts; the maximum diameter of the inverted cone and the double cone should, however, be below the transition of the silo. Among the three inserts investigated, the double cone appeared to be the best, although even with this insert mass flow could not always be obtained if the hopper had an inclination angle as large as 45°. In such a situation, more simulations revealed that the extension of the lower part of the double cone had the potential to improve the flow pattern in the hopper. This potential could be utilized by a combination of extending the lower cone of the double cone insert and reducing the friction between the material and the hopper wall. To ensure improvement, further simulations illustrated that a ratio of 2:7 between the maximum diameter of the insert and the diameter of the silo was also crucial for the best effect.