Numerical Simulation And Optimization Study On Plenum Chamber Used In Biaxially Oriented Plastics Film's Production

Bidirectionally oriented films have been widely used in various industries with their excellent properties.Temperature controlling technology is an important technology affecting the production of biaxially oriented films.Besides,it is also a key technology for the future development of the film industry.The uniformity of the outlet air of the plenum chamber is the key factor of the film temperature control,which affects the performance of the film.Therefore,the study of the air flow status and uniformity of the flow field inside and outside the plenum chamber is of guiding significance to its design and is also of great significance to the temperature control technology in the film production.The plenum chamber of transverse stretching section studied in this paper originates from the 8.2m biaxial stretching polypropylene film production line of Guilin Electrical Equipment Scientific Research Institute Co.,Ltd.In order to study the distribution characteristics of the flow field inside and outside the plenum chamber and the uniformity of wind speed of outlets,CFD software Fluent was used to solve the case with experimental conditions.The numerical model and boundary conditions are determined according to the experimental conditions.The simulation data solved out by Tianhe-2 are compared with the experimental data.The error of the two sets of data is less than 7.5%.The feasibility of model modeling,meshing and solution set is determined.Based on the calculation of the experimental model,the wind speed of outlets of the plenum chamber at different fan speed is calculated,as the fan speed at 900,1200,1500,1800 and 2100 rpm.The uniformity of the outlet air is evaluated by the velocity deviation of the single bellow,the overall velocity deviation and the diagonal deviation of the plenum chamber.The results show that the velocity deviation and diagonal deviation of the single bellows are good,and all the schemes can meet the engineering requirements.However,due to the existence of a diagonal phenomenon,when the fan speed exceeds 1200 rpm,the overall speed deviation of the plenum chamber will exceed the engineering requirements.Therefore,from the point of view of orifice plate structure design and air distribution box diversion structure design,this paper puts forward ideas and methods to improve the design of the plenum chamber.The influence of the structural parameters of the orifice plate on the uniformity of outlet air of plenum chamber was studied,three factors and two levels of the orthogonal experiment was used to carry out the experiment.Three factors of aperture,symmetry and hole shape were selected for modeling,the velocity deviation of single bellows,overall deviation of static pressure box and diagonal deviation were used to evaluate the model.The results show that for the influence of mass flow rate,the size of the influencing factors is aperture,symmetry and pore shape.In terms of uniformity of the air,the influence of the aperture is the largest,followed by the shape of the hole,and the minimum is whether the outlet hole is symmetrically arranged.In the original design,reduced the diameter of air outlet from 15 mm to 12 mm,the uniformity of air outlet meets all engineering requirements.In view of the design of diversion structure,the position and shape of diversion structure are changed.The calculation results show that the optimization of the diversion structure has an obvious effect on the uniformity of the outlet air of the plenum chamber.Diagonal deviation,velocity deviation of single bellows and overall deviation of plenum chamber were increased by 12%,9%,and 8.6% respectively.