Structural Design And Experimental Study Of Air Curtain Residual Film Barrier Device

Xinjiang is the largest cotton producing area in China and the world.In 2022,Xinjiang ’s cotton production will reach 5.977 million tons,accounting for 90.2 % of the country ’s cotton production.With the large-scale planting and high yield of cotton in Xinjiang,mechanized picking has been widely promoted and used in Xinjiang cotton fields.Compared with traditional manual picking,mechanized picking has the advantages of high efficiency and low cost,but the problems of increasing impurity rate of seed cotton and reducing cotton quality also need to be solved urgently.At present,the removal of residual film is mainly carried out after picking,but after multiple loosening of seed cotton and multi-channel foreign fiber cleaning process,the residual film becomes smaller and difficult to remove.The air curtain residual film blocking device based on jet air curtain blocking technology can reduce the mixing amount of residual film during cotton harvesting and reduce the cleaning pressure of the back-end process.In this thesis,combined with the research status of the existing air curtain residual film barrier device,aiming at the problems of complex structure and inconvenient installation of the device,an air curtain residual film barrier device with simpler and more reasonable structure and more stable jet air curtain performance is designed,which can reduce the mixing amount of residual film during cotton harvesting and reduce the cleaning pressure of the back-end process.The main research contents are as follows :1.In order to better meet the design requirements of the air curtain residual film barrier device in terms of structure,airflow distribution,energy loss,etc.,the working principle of the device is described,and the theoretical analysis of the overall structure of the device and the wall thickness of the shell is carried out.Finally,the key structure-airflow distribution chamber is designed.2.As the key structure of the residual film barrier device,the air distribution chamber is the key structure of the residual film barrier device,which has the function of optimizing the flow field structure and uniform jet air curtain.Under the condition that the external structure of the airflow distribution chamber is difficult to be further optimized due to the limitation of the assembly space,the design of the structural parameters of the jet slot has a positive effect on improving the uniformity of the airflow distribution in the airflow distribution chamber.In order to improve the uniform stability of the jet air curtain of the residual film barrier device,the velocity non-uniformity coefficient was used as the evaluation index,and the single factor test was carried out by Fluent to determine the range of influencing factors.Combined with the second-order response surface method and the second-generation non-dominated sorting genetic algorithm(NSGA-Ⅱ),the optimal parameter combination was obtained.According to this parameter combination,a threedimensional model is established to analyze the distribution characteristics of internal and external flow fields.The results show that the air curtain at the jet slit is offset,the velocity distribution in the flow channels on both sides of the interior is uneven,and the velocity gradient at the jet slit is large.3.According to the analysis results of flow field distribution characteristics,a deflector is introduced to improve the working performance of the air curtain residual film barrier device.Firstly,the influence of various influencing factors on the performance of air curtain residual film barrier device was investigated by single factor test.Then,the optimal structural parameters of the device were obtained by orthogonal test design : the bluff body angles were 60 ° and 150 ° respectively,the guide plate was arranged in the middle,the shape of the guide plate was curved,the central angle was 70 °,the number of guide plates was 1,and the turning radius was 50 mm.The computational fluid dynamics-discrete element(DEM-CFD)coupling method was used to verify the barrier performance of the air curtain residual film barrier device.The results show that the air curtain residual film barrier device can effectively block the residual film.4.The air curtain residual film barrier device was trial-produced,and the jet slit wind speed test and the performance verification test of the air curtain residual film barrier device were carried out.The experimental results show that the maximum velocity deviations of the left and right sides of the two jet slits and the air curtain forming nozzle are 8.3 %,14 %,13 % and 10.7 %,respectively.The distribution trend of the jet slit velocity test value and the simulation value is in good agreement.The performance verification test of the air curtain residual film barrier device shows that the average residual film barrier rate is 82.75 %,and the residual film barrier rate obtained by DEM-CFD is 87.9 %,which proves that the previous simulation test can provide theoretical guidance and basis for the bench test,and the air curtain residual film barrier device can effectively block the residual film.