Multi-objective Optimization Of Coat-hanger Die Based On Fluid-structure Coupling Analysis

Coat-hanger die is the molded part of the extruder which is located in the lithium battery separator production line.The function is to obtain good flow distribution of the melt polymer in the die cavity from the extruder,thereby controlling the thickness uniformity of the film.Importantly,the quality of the internal flow channel design also affects the production efficiency and the quality of film directly.Among all "flat seam extrusion dies",the coat-hanger die has advantages of strong adaptability and good extrusion quality which is widely used.In the current die design process,seldom consideration is given to fluid-structure interaction,more numerical simulation,less experimental verification and insufficient systematicness of optimization theory.In this paper,simulation,algorithm research and related experimental analysis are carried out for the coat-hanger die based on fluid-structure coupling and multiobjective optimization,in order to obtain the optimal die structure and process parameters.Based on physical mapping and literature research,conducting the die structure formula.Based on two design criteria,the same average residence time and the same shear rate,threedimensional parametric model of the coat-hanger die is established in Solidworks.At the same time,using the professional Fluent software,CFD flow field comparison simulation of the two models is carried out.Qualitative and quantitative analysis of the pressure and velocity field are carried out according to simulation results.Using similar theory to design experiment,make a 2:1 scale-down hanger type die,measure the rheological parameters of the experiment fluid HPMC using a TA rotary rheometer,simultaneously measure the velocity distribution of polymer melt using PIV technology.The flow velocity distribution data(CV%)on the outlet centerline for simulation is compared with experiment condition,and the coincidence is good,thus verifying the correctness of the simulation model.Solid deformation has great influence on the uniformity of the crack in the relaxation region.Based on fluid-solid coupling analysis,the deformation laws of rectangular,trapezoidal and curved die are discussed.Taking the variation coefficient of outlet flow velocity,average pressure drop from inlet to outlet and the differential deformation of the relaxation region as the optimization objectives,the orthogonal experimental design method was used to screen five initial variables and determine the variable optimization range.38 parameter combination schemes were designed by DOE method,fit numerical model by respond surface method and create the optimization objective function.Multi-objective genetic algorithm is used to globally optimize the fitted model in the variable space.The optimization system and related rules used in this paper have certain significance for structure design,development process and optimization algorithm of similar products.