Structural Analysis Of Twin-Screw Extruder Barrel And Numerical Simulation Of Flow And Heat Transfer Of Polymer

Twin-screw extruder is a kind of mechatronics advanced equipments in chemical industry, and it is mainly used for plastics modification and granulation production of chemical raw materials. The large-scale pelleting machine system has always relied on imports, so there is an urgent need to develop and produce them by ourselves and ensure quality.The barrel is the important part of the large-scale pelleting machine system. This paper focuses the structural analysis of twin-screw extruder barrel and the numerical simulation of flow and heat transfer of polymer. The work is divided into three parts:(1) A finite element model is established for the twin-screw extruder barrel with two heating pipelines in axial direction. The finite element analyses of four work conditions such as pressure test, normal, critical conditions and critical conditions without heat transfer are completed in order to predict the distributions of temperature, stress and the deformation of the barrel. The results of loads of the coupled thermal-force for the three work conditions show that the present design of the twin-screw extruder barrel with two heating pipelines is reasonable to satisfy the requirements of the strength and heating. Finite element analysis provides a solution to obtain the stress, strain and temperature under the load of the coupled thermal-force, which is help for the strength check of the barrel structure and the optimization design of the heating pipeline.(2)Three-dimensional models of the flow and heat transfer have been established for polymer in barrel. The temperature distribution, velocity distribution, pressure distribution and temperature profile are obtained. Numerical results show that the polymer have both axial velocity and circumferential velocity. The pressure of polymer increases along the extrusion direction. The temperature of polymer increase with the time.(3) An unsteady model of heat transfer in twin-screw extruder including barrel, polymer, and screws during preheating is established in order to predict distribution and variation of temperature in extruder, and situaton of melting of polymer in groove of screw. Numerical results show that temperature in the middle of barrel and close to the heating pipeline is higher than those in other places by the influence of distribution of heating pipeline as well as melting of polymer is faster. Average temperature of 8-type surface of barrel, polymer, and screw increase with preheating time. The temperature of 8-type surface of barrel during early preheating increases faster than those of others, and reaches steady fastest in end of the preheating, while the situation of screw is opposite to that of "8" surface of barrel. The melting speed of polymer in barrel decreases with the preheating time cooperating with the change of temperature. When the flow rate of thermal oil decrease by half, the time for preheating increase mostly.Finite element analysis of barrel is help for the strength check of the barrel structure and the optimization design of the heating pipeline. The research of the polymer in barrel could be helpful for choosing the work condition and ensuring quality. The results of numerical analyses for preheating have signification to guide design and optimization of heating pipeline in barrel, and exactly predict safety time of preheating.