Stress Analysis Of Rotors Of Large-Scale Screw Extruders Based On Fluid-Structure Coupling Method

With rapid development of large-scale industry and urgent needs of localization of key equipment,it has been the focus and also difficult to design the large-scale twin screw extruders.As the key component of the large-scale twin screw extruder,the failure of the screw rotors has become the bottleneck of the localization of the large-scale extruders.However,research work on the extruder in domestic and abroad most has mainly focused on the mixing effect and the experiments about mechanical properties of the core shaft.Moreover,little work has been found to get the information of load-carrying for the screw rotor and the core shaft under running conditions,and little study concerned the stress analysis of the rotor based on fluid-structure coupling theory.Therefore,this paper developed an approach to analyze the screw rotor of the large-scale extruders based on fluid-structure coupling method.The main work and conclusions are listed as follows:(1)Based on POLYFLOW code and mesh superposition technique,the Fluid flow model of a large-scale twin screw extruder was established,and the results show the fluxion pattern of the internal melt in the barrel,and give the transport capacity and shear ability of the screw component had been revealed.(2)The flow rule of the fluid was investigated through adjusting the design parameters(the gap between the tip of rotor and the barrel,and the center distance of the assembly)and process parameter(the speed of the motor).The research results that the transport capacity is strengthen with the increasing of the speed,and the screw component holds more sensitive to the change of the speed than the kneading block.Moreover,it shows that the transport capacity of the screw rotor reaches the maximum when the gap reaches the 2.5 mm,or the center distance of the assembly is 268 mm.Under given conditions,the effect by changing of the gap is less than that by adjusting the center distance of the assembly.(3)Based on Solid Works and ANSYS/Workbench,the fluid-structure coupling model was created for the large-scale twin-screw extruder,and the mechanical properties of the rotor under different working conditions was analyzed.The results show that the dangerous zones are located at the shoulder the inlet and outlet of the shaft,and the first connection section between the screw thread and the kneading block.In addition,the center distance of the assembly should be great than 261.1 mm when the speed of the rotor reaches 185 rpm,or the two rotors will collide each other or even be locked against each other.The role of the pressure load of the melt on the screw rotor is greater than that of the torque load of the motor when the speed of the rotor is greater than 145 rpm,which means that the flow pressure of the fluid is an important load for the screw rotors.