| Roof box have beautiful appearance and convinient to drink,which is favored by many consumers.However,because the roof box is often used for pasteurized milk packaging,the shelf life of the product is short and the cost of sales is high.The introduction of aseptic filling technology into the production of roofing carton products can significantly extend the shelf life of products,reduce the cost of sales and promote the sales of roofing carton packaging products.Aseptic filling environment can avoid secondary contamination of packaging materials and food during filling,guarantee product quality and prolong product shelf life.Therefore,research on the establishment and maintenance of aseptic environment in the filling room of rooftop carton filling machine has important engineering application and economic value for the production and sales of rooftop carton products.This paper takes BHWD6000 type enclosed aseptic filling machine as the research object,mainly studies the aseptic air flow on the establishment and maintenance of the aseptic environment in the filling room of the filling machine.Firstly,Fluent software was used to simulate the particle flow distribution in the filling room and the influence of aseptic air velocity on the particle removal efficiency in the filling room.Then,based on the dynamic grid technology,the influence of the roof carton movement on the air flow in the filling room was explored to obtain the relevant influence law.Finally,the flow field in the filling room was optimized.Combined with the response surface test method,the optimal aseptic flow process parameters for establishing the aseptic environment of the filling chamber were obtained.The specific research contents and results are as follows:(1)Analysis of airflow and particle flow characteristics and study on the influence of airflow velocity on particle removal efficiency under pre-cleaning conditions.Based on Fluent fluid simulation software,the gas-solid two-phase flow simulation was used to analyze the flow characteristics of air and particles in the filling chamber and the distribution of particles,and the removal efficiency of particles in the filling chamber by three different air velocities of 0.5m/s,1.0m /s and 1.5m /s was analyzed.The results show that the flow of air in the filling chamber has this backflow.The flow of air and particles is greatly affected by the structure of the filling chamber.Most particles settle at the bottom of the filling chamber.At 0.5 m/s,1.0 m/s and 1.5m/s,the particle removal efficiency is 31.97 %,59.9 % and 63.99 %.(2)Analysis of the influence of roof box on the maintenance of aseptic environment in the filling room during filling.The dynamic grid technique was used to analyze the influence of the process of entering the filling chamber from the packing material sterilization chamber to the external static pressure on both sides of the filling chamber.Firstly,UDF was used to compile the boundary motion of the roof box,and then the three specifications of 250 m L,500 m L and1000 m L were numerically simulated to fill the roof box under three inlet air velocities.Taking1000 m L roof box as an example,the influence of roof box movement on the static pressure at both sides of the filling chamber was analyzed.The results show that the larger the size of the roof box,the smaller the static pressure on both sides of the outlet.When the roof box enters the filling chamber and gradually occupies the conveying chain of the filling chamber,the static pressure at both sides of the outlet decreases gradually.The outlet pressure on both sides increases with the increase of inlet flow velocity.The moving speed of the roof box has no effect on the air flow in the filling room.What affects the air flow is the obstruction of the roof box itself.(3)The influence of different air inlet ratio on the uniformity of flow field in the filling chamber of roof box filling machine.Study and analyze the influence of different filling ratios on flow field uniformity.Set up five different filling ratios of 60%,70%,80%,90% and 100%,three filling chambers with different sizes and the same internal structure within a certain range.In a certain range,filling chambers with different space sizes have a certain universality of the full ratio.When the full ratio of air inlet is 70%,the flow field uniformity is the best and the air utilization efficiency is the highest.(4)Optimal design of air flow at the top inlet of filling chamber of roof box filling machine.The air flow was guided by installing a baffle under the air flow inlet,and the interaction among the baffle Angle,air velocity,ventilation time and other factors affecting the efficiency of particle removal was analyzed by response surface analysis.The regression equation was established,and the process parameters of the optimal particle removal efficiency were obtained under the minimum flow rate: the Angle of the left baffle was 52°,the Angle of the right baffle was 42°,the inlet air was 1.17 m/s,the inlet air was 18.8 s,the particle removal efficiency was increased to 91.87 %,and the particles were completely removed in the filling chamber.The minimum inlet air velocity required to maintain the aseptic environment in the filling area was studied in three kinds of roof boxes.The minimum air velocity required to maintain the aseptic environment in 250 m L,500 m L and 1000 m L roof boxes was 0.851 m/s,1.014 m/s and 1.328m/s. |
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