Residual film recovery is highly required for the high mechanical properties and picking-up rate with the low soil content of the recovered residual film. In this study, a roll-type picking component was designed to easily separate the soil. The rotary tillage blade was also used to throw up the membrane-soil agglomerate. The roll spring teeth were then selected to effectively pick up the residue film. The finite element method (FEM) and smoothed particle hydrodynamics (SPH) were coupled to establish the contact model between the roll spring teeth and the membrane-soil agglomerate. The finite element meshing was performed on the roll spring teeth and the residual film. The soil was assumed to the smooth particles. A microscopic analysis was made on the residual film stress and soil disturbance after the roll spring teeth were contacted on the membrane-soil agglomerate. It was found that the residual film stress was concentrated near the contact tip point of the roll spring teeth. The peak stress of residual film increased first and then decreased with the increase of the contact time. The maximum and average peak stresses of residual film were 0.2518 and 0.1319 MPa, respectively. The soil strain increased gradually with the increase of contact time, where the maximum soil strain was 3.271. The soil particles near the tip of the roll spring teeth were cracked to increase the soil disturbance. A three-factor five-level quadratic regression was conducted with the turning radius of roll, the diameter of spring teeth, and the top bend angle of spring teeth as the test factors, while the average peak stress of residual film and the maximum soil strain as the test indexes. A mathematical model was also established to clarify the influence of each influencing factor on the test indexes. At the same time, the optimal structure parameters of roll spring teeth were obtained as the roll turning radius was 100 mm, the spring teeth diameter was 5 mm, and the top bend angle of spring teeth was 42°. In this case, the average peak stress of residual film was 0.120 1 MPa, and the maximum soil strain was 3.758 4. The roll spring teeth were then fabricated using the optimal structural parameters after simulation. A new machine of residual film recovery was assembled to verify the influence of structure parameters of roll spring teeth on the picking-up performance. Field verification tests were conducted with the picking-up rate and soil content as the test indexes. A better performance was achieved in the picking up rate of 80.4% and soil content of 37.13%. There was no slip on the high-speed rotating of roll spring teeth. The residual film was constantly wound and indirectly punctured at the tip of the teeth. The roll spring teeth made it easier to crack the soil in the membrane-soil aggregate. The soil was then much easier to leave the residual film. The membrane-soil separation was gradually completed, indicating the soil no longer sticking to the residual film. Compared with the previous soil tank test, the picking-up rate increased by 8.74 percentage points, whereas, the soil content decreased by 12.18 percentage points, indicating the better performance of the machine. The finite element model can provide a strong reference for the structural optimization of the residual film recycling machine.

Residual film recycling machines cannot fully meet the requirements of large-scale production of residual film. Serious film entanglement and winding can often occur in the bearing part. The cotton straw cannot be completely broken, thus leading to the low film content of the recovered film. It is very necessary to improve the pick-up rate with less straw content from the recycling mixture in the residual film recycling machine. In this study, the double-roller residual-film recycling machine was designed suitable for surface residual film recycling after the autumn harvest. The pneumatic and mechanical collaborative film was unloaded to realize the operation using mechanical film picking. The key components were determined to better design the film recycling machine. The kinetic analysis of film picking and unloading was carried out to match the range of working speed, in order to overcome the interference among the machinery. The key structural parameters were determined for the film-picking and unloading device. The center motion trajectory of the roller and the forward and reverse cam orbits were optimized to determine the cam structure parameters. Mathematical and graphical analysis was used to obtain the conditions of no missing in the film-picking device. The film unload device was simplified in the software to divide the grid. The data was then imported into the flow analysis software. The flow field was simulated inside the film unloading device. A systematic investigation was implemented to explore the influence of the flow field on the transport of the residual film. The results show that the "O" shape rotation formed by the airflow was a benefit to the separation of residual film and impurities. Single-factor test was carried out with the rotating speed of the film picking and unloading roller as the test factors, according to the forward speed of the machine. The operating parameters of the machine were obtained, including the optimal operating range of the forward speed, the rotating speeds of the film picking and removing roller. The response surface test was then designed to verify the effectiveness of the machine, with the forward speed of the machine, the rotating speed of the film picking and unloading roller as the test factors, and the pick-up rate of the residual film and the straw content rate of the recovered mixture as the test indexes. The analysis of variance was performed after the test. The regression equations were obtained for the pick-up rate and straw content rate. The optimal working parameters were obtained to optimize the factors. The test results show that the operation performance was better, when the forward speed of the machine was 6.7 km/h, the rotating speed of the film-picking roller was 57 r/min, and the rotating speed of the film-removing roller was 570 r/min. A field verification test was carried out under the optimal combination of parameters, the results showed that the mean value of residual film pick-up rate was 86.1% and the straw content rate of the recycling mixture was 39.2%, compared with the existing film recycling machine, the residual film pick up rate isincrease 1.07 percentage pionts, and all indicators meet the requirements of the surface residual film recycling machine afterharvest.

In order to improve the screening performance and cleaning effect of the jujube harvesting machinery cleaning device, a vibrating curved screen device was designed in this study. By analyzing the structure mechanism of the curved sieve body, it was obtained that the arc-shaped mesh hole spacing S was 15-25 mm and the curved mesh hole curvature U was 90°-150°. By exploring the movement state and stress of jujube and impurities on the curved sieve body, it was determined that the horizontal spacing L of the curved layer sieve was 30 mm and the vertical spacing H was 45-65 mm. Taking the vertical spacing H of the curved layer sieve, the curvature U of the curved mesh hole, and the spacing S of the curved mesh hole as the experimental factors, considering the screening efficiency α and the impurity content β of the jujube as the response values, the three-factor three-level quadratic regression orthogonal experiment was designed, establishing the regression mathematical model of each factor and response value, and the multiple target optimization algorithm of Design-expert software was used to optimize various factors. The results showed that the influence factors on the screening efficiency were in the descending order as: the arc screen spacing, the vertical spacing of the curved layer screen, and the curved screen hole curvature; The significant factors affecting the impurity content of jujube were in the descending order as: the arc screen spacing, the curved screen hole curvature, and the vertical spacing of the curved layer screen. The experimental results were verified by the optimized combination of parameters: when the vertical spacing H of the curved layer screen was 65 mm, the curved screen hole curvature U was 110°, and the arc screen spacing S was 23 mm, the average screening efficiency α in the test was 91.09%. The relative error between the experimental verification value and the theoretical optimization value was 1.36%, which was less than 5%. The impurity content of jujube β in the test was 1.02%. The relative error between the experimental verification value and the theoretical optimization value was 2.00%, which was also less than 5%. The test results can provide a reference for the research and optimization of the subsequent air-suction-type jujube harvester cleaning device.