Analytical Solution of Flow Balance Coefficient at the Outlet of Slit-combined Channel in Polymer Extrusion Process
For thin-walled plastic profile extrusion products,the channel of the extrusion die forming section is a slit-combined channel.In the extrusion process,the flow balance at the die outlet directly affects the forming quality of extruded products.The flow balance coefficient at the outlet of the slit-combined channel usually depends on numerical simulation,which has high technical threshold,great difficulty in solving,and limited scope of application.In view of the above problems,an analytical model of the flow balance coefficient at the outlet of the slit-combined channel is proposed.Firstly,the theoretical formula of the flow balance coefficient is expanded by the complete square formula,and the velocity dependent and independent term of the flow balance coefficient are obtained.Then,assuming that the power-law fluid is fully developed in the slit channel,the analytical formula of the flow balance coefficient at the outlet of the slit channel is obtained through theoretical derivation.Then,based on the region division of the combined-slit channel and the velocity ratio formula of different sub regions,the theoretical model of the flow balance coefficient at the outlet of the slit-combined channel is established.Finally,the analytical value of the flow balance coefficient is verified by numerical simulation for a typical slit-combined channel.The results show that when the width-height-ratio of each sub region is greater than 10,the error of the analytical solution and numerical solution of the flow balance coefficient is less than 5％,which meets the needs of practical application.
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