Flow Field Simulation And Experimental Study Of Bearing Elements Of Twin-screw Extruder

For those intermeshing co-rotating twin screw extruder of large length-diameter ratio,flexible deformation of the high-speed rotating screw in the barrel occurs by the force of its own gravity and centrifugal force.When the deflection is greater than the gap between the screw and the barrel,the wear between the screw and the inner wall of the cylinder occurs,which affects the quality of the product,reduces the life of the extruder,an addition of support measures to the extruder can improve this situation,the support measurea is to adopt the bearing elements in the screw configuration in this paper.Based on the principles of Rheology and Hydrodynamics,the flow field characteristics of two bearing elements and their screw configurations were researched in this paper.Based on the principles of Mechanics of Material,integrated using Analytical calculation and finite element simulation method,influence of the number and position of the bearing elements on the deflection of the screw were studied,and an optimization method of position combination when setting two bearing elements was put forward.Under the conditions of using two kinds of materials of different melt flow rate,three kinds of screw configurations and different operation parameters,the influence of setting sliding bearing element in the screw configuration on the extruder energy consumption were researched through experiments.The flow field simulation results show that:the two kinds of bearing elements are both pressure consuming elements while the pressure consumed can be compensated after combining with pressure building elements.The pressure consumption of sliding bearing element is greater than the same length of rolling bearing element.The two kinds of bearing elements have little effect on dispersive mixing and have certain distributive mixing property.The bearing elements are more suitable for processing high melt flow rate materials.The results of influence of the number and position of the bearing elements on the deflection of the screw suggested that:the deflection of screw is mainly caused by gravity while the deflection caused by centrifugal force and pressure of die are far less than gravity.Setting bearing elements in the screw configuration can significantly reduce the deflection.In order to minimize the friction or collision between the screw and the barrel,for those screws with the length-diameter ratio less than 68,one bearing element can be placed at the optimum position calculated from the fitting formula obtained and for those screws with the length-diameter ratio between 68 and 120,two bearing elements can be placed at the optimum position combination calculated from the fitting formula obtained.The experimental results show that:the energy consumption of screw configurations with bearing elements is slightly larger than those with conventional double-headed screw elements but less than 45° kneading block configuration,thus the effect of setting bearing elements in the screw configuration on the energy consumption is weak.The bearing elements are more suitable for processing high melt flow rate materials.The energy consumption increases with the increase of feeding amount and the rotating speed when the bearing element is placed.