Numerical Simulation Of Coupling Cooling Air Flow To Film Blowing Model

Blown film is an important film production process,which is complex.In order to achieve stable continuous production of the film,the equipment and process parameters needed to be adjusted repeatedly.Blowing film forming process and external cooling air flow field are coupled with each other,using numerical simulation method to study blow molding film forming process to understand its forming mechanism is important.In the past,the numerical simulation of blown film assumed that the melt outlet velocity and the cooling air outlet velocity are evenly distributed in the circumference.The study can be classified into two types,fix bubble shape to study the external cooling flow field and the heat transfer.The other used experimental or calculated data of the heat transfer coefficient,to study the film shape and temperature,this one-direction simulation method is low accuracy.In order to enhance the accuracy of the simulation,this paper uses the computational fluid dynamics software Polyflow and Fluent to simulate the blown film and the external cooling air flow field.In this paper,it is assumed that the flow rate in outlet of melt and cooling air outlet flow rate films are evenly distributed along the circumference,to find out the influence of the air outlet gap,he inclination angle,the cooling air inlet flow rate and the blowout ratio on the cooling of the blown film.The results showed that: When the flow rate of the cooling air inlet is fixed,increasing the gap of the air ring outlet,the maximum value of the heat transfer coefficient is reduced and the inflation ratio of the film is reduced in the region in the height of wind ring.The increase of the outlet angle,the maximum heat transfer coefficient increase,but the film blowing ratio changes less.When air ring outlet gap is fixed,increase the cooling air inlet flow rate,the maximum heat transfer coefficient increases,the ratio of the film in the air ring height area increases;When cooling conditions unchanged,the film blowing ratio increased,the position of the heat transfer coefficient maximum value will become lower,the film temperature drop faster in the height area of wind ring.Based on the study of the melt outlet flow rate and the cooling wind speed along the circumference,this paper studies the effect of the melt flow rate in outlet along the circumferential fluctuation and the cooling air volume on the film velocity and temperature uniformity.The results show that when the air volume is uniform in the circumferential,the film is thicker and the temperature is higher with higher flow rate of the melt in the circumferential.The fluctuation of the film thickness in the circumferential increases rapidly in the height of air ring height,and gradually reduced above the air ring.When the melt outlet flow rate is evenly in the circumferential direction,the thickness of the film is larger and the temperature is lower if the cooling air volume is larger in the circumferential.The fluctuation of the film thickness in the circumferential direction is small in the height area of the air ring and increase above the region.Then,by adjusting the fluctuation of the cooling air volume in the circumferential direction,the circumferential thickness fluctuation of the film caused by the flow rate of melt reduces,so that the uniformity of the film thickness is optimized.This research provided an effective reference for the understanding blown film process,the optimization design of cooling air ring and processing parameters with a certain practical significance.