Brief introduction of solid conveying rate of plastic granulator
Brief introduction of solid conveying rate of plastic granulator When the polymer pellets enter the extruder from the hopper through the feed port tangential to the screw, the feeding section begins, and this section extends to the point where the surface temperature of the barrel reaches the melting point of the polymer. It is observed in the transparent barrel that the behavior of individual particles is random, and the particles do not necessarily advance in the same direction, but may rotate with the screw, "bridge" each other and turn over. In most cases, however, in general, the pellets are compacted into a cohesive bed shortly after entering the channel. The solid bed not only moves relative to the stationary screw, but also has a relative velocity with the rotating machine, and the two act on the surface of the bed with friction. These forces are usually expressed as the product of the coefficient of friction and the normal stress on the surface. The component of the machine speed along the direction of the screw groove is greater than the moving speed of the solid bed. The movement of the barrel gives thrust to the bed, and the friction between the lower surface of the bed and the screw is the resistance of the bed movement, so the friction coefficient between the polymer and the metal surface is of great significance. A comprehensive analysis of solids transport in a single screw extruder was made by D and M in 1956. In their study, the simplified assumptions were made as follows: The granular solid is a continuous medium; the solid bed contacts all surfaces of the screw groove (including the surface of the barrel, the bottom surface of the screw groove, the side surface of the screw flight, and the depth of the screw flight); the screw flight gap is ignored; The micro-element moves at the same speed, there is no internal deformation in the bed, the pressure is only a function of the distance along the direction of the media tank, and the barrier coefficient has nothing to do with the pressure, but is a function of the temperature, regardless of gravity, centrifugal force and density changes of active cold currents.
