| The melt extruded by the extruder reaches to every die through the filteration and distributary device in the multi-dies extrusion blow molding equipment. This equipment has been widely used in the production of small and medium-sized plastic parts because of its high productivity and simple mold structure. But it still has some problems, such as pressure and velocity fluctuation in the process of the filteration and melt distribution unbalance. Filtration and distributary device is a key structure which can affect the production efficiency and product quality in the multi-dies extrusion blow molding equipment. In this paper, the structural design and flow field analysis of the filtration and distributary device are studied. The flow situation in the work process of melt filter is analyzed and a new-type filteration structure is put forward. Besides, this paper presents the overall balanced runner unit, studies the effect of the structure and process parameters on the pressure drop and flow balance on the basis of the numerical simulation, and optimizes by the response surface method and particle swarm algorithm.The main contents of this dissertation are as follows:In the first chapter, the current research status on the structural design and flow analysis of the filtration and distributary device in the multi-dies extrusion blow molding equipment is summarized. The deficiencies of the current research are pointed out. In the end, the research background, main content and structural frame are given.In the second chapter, the structure of the filtration and distributary device is studied and the simulation model and the mathematical model of its flow field analysis are established. Aimed at the melt distribution problem at the occasion of dies arranged side by side in a straight line, the overall balanced flow unit is proposed. This unit can apply to the layout with the branch number which is not2to the power of n, that can make up for the shortage of the natural balanced runner with limited branch number in the situation of dies abreast layout. In terms of calculating the runner diameters, the variation balance coefficient is introduced on the basis of the diameter calculation formula in natural balanced runners.In the third chapter, changes on the pressure and velocity of fluid flow in the melt filter are analysed, and the main factor (inlet flow)that influences the fluid pressure field and velocity field is studyed. In view of the instability problem of melt pressure and velocity in the process of changing filter layers in a traditional filter, this paper designs a new-type loop-screen self-cleaning filter, and puts its performance compared with traditional filters. In the fourth chapter, the influence of the distributary runner structure parameters on the pressure change and melt flow balance is comprehensively evaluated. By orthogonal experiment method, the influence of main structure parameters on the fluid pressure drop and flow balance can be analysed, and the impact weight of the structure parameters on pressure drop and flow balance can be judged through the range analysis; Against the difficulties of processing and manufacturing of "variable cross-section" method in the unbalanced runner,"variable runner location" method is presented to improve the performance of flow balance on the overall balanced runner unit. At last, the influence of the main process parameter on the melt flow is analyzed.In the fifth chapter, the Latin hyper-cube method is used to carry out sampling of parameters. The response surface model is established based on the least-square method, reflecting the mapping relation between design variables and objects. And the particle swarm optimization (PSO) algorithm is adopted to optimize the runner structure and process parameters. Finally, the research object is verified by simulation tests.In the sixth chapter, main works and innovation of this dissertation are summarized so as to put forward aspects for the improvement and further research. |
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