The application of twin-screw extrusion technology in the field of straw pretreatment is constrained by the closed nature of its structure, and the internal material flow characteristics have yet to be fully elucidated. This has resulted in a paucity of scientific theoretical support for screw configuration design. To address this issue, this study employed the discrete element method (DEM) in conjunction with physical tests to calibrate the simulation model parameters of rice straw powder. The calibration results demonstrate that the discrepancy between the simulation stacking test and the physical test results is 3.68%, thereby indicating that the simulation model parameters are accurate and reliable. Subsequently, an extrusion verification comparison test of rice straw powder was conducted. The results demonstrated that the relative errors between the simulated and actual quality in different regions ranged from 7.95% to 12.45%. This evidence substantiates the applicability and reliability of the established simulation model in simulating the extrusion process of rice straw powder. Furthermore, the variation rules of the parameters of particle motion and their correlation during the extrusion process of rice straw powder were investigated. It was found that the filling degree was significantly correlated with other parameters, and that the screw configuration had a direct influence on the filling degree. Finally, a bench test was conducted to ascertain the viability of the established simulation model in guiding the design of screw configurations. A linear regression equation was derived between the simulated power consumption and the average particle size of extruded samples under different screw configurations. The study offers a particle-scale understanding of the visualization of the extrusion process of rice straw powder and the scientific design of screw configurations, which is of great significance for the industrial application of the extrusion method.

In response to the problems of low efficiency, high labor intensity, and low mechanization in manual tobacco harvesting, a comb-off tobacco picking device for southern hilly tobacco areas was designed following the agronomic requirements and the principle of manual picking of tobacco harvesting in southern China. The device was composed of the power chassis, picking mechanism, and storage mechanism. This study involved the theoretical analysis, structural design, and modeling of the key components, such as chassis structure, combing-type picking mechanism, and power synchronization mechanism. The results of the motion analysis and calculation of the picking process demonstrated that the adjustment range of the comb chain elevation angles was from 12.4° to 20.9°, the comb rod installation distance was 76.2 mm, and the synchronizing mechanism transmission ratio was 3:10. One-factor test and three-factor three-level orthogonal test was performed with the forward speed of the chassis, the distance between the picking device baffles and the elevation angle of the chain with the combing bar as test factors, and the rate of broken and missed tobacco picking as evaluation indicators. It was revealed that the optimal combination of the forward speed of the chassis, the distance between the baffles, and the chain elevation angle were 1.5 km/h, 75 mm, and 12.4°, respectively. Moreover, verification tests suggested that the breakage rate of tobacco leaves was 9.99%, and the probability of missed tobacco picking was 7.31%, both of which satisfy the agriculture requirements and the operational requirements in the agricultural machinery certification syllabus.

In this study, the discrete element software EDEM was applied to establish a simulation model of non-uniform-sized particle units for Broussonetia papyrifera stalks, which aimed to address the low utilization rate of existing Broussonetia papyrifera harvesting machinery, the significant variation between the simulated model of Broussonetia papyrifera stalks and their actual appearance, as well as the absence of contact parameter calibration. Through a combination of the free-fall collision method, inclined plane sliding method, and inclined plane rolling method, numerical simulation was conducted to analyze the pattern of variations in contact parameters between Broussonetia papyrifera stalks and the steel material of the machinery. Accordingly, these parameters were calibrated. The results showed that the coefficient of restitution between Broussonetia papyrifera stalks and steel materials was 0.321, the static friction factor was 0.589, and the rolling friction factor was 0.078. With the parameters of contact between Broussonetia papyrifera stalks as variables and the experimentally measured pile angle as the objective of optimization, the steepest ascent experiment and the three-factor five-level rotation combination experiment were conducted. In this way, a second-order response model was constructed to analyze the relationship between the contact parameters and the pile angle. Through the optimization analysis of experimental data, it was determined that the coefficient of restitution between Broussonetia papyrifera stalks was 0.21, the static friction factor was 0.24, and the rolling friction factor was 0.03. Furthermore, the calibration results were validated through experimentation to show that the relative error between the obtained pile angle under the context of optimal parameter combination and the actual one was 4.11%. In addition, the relative error of mass flow rate in spiral transport was within a reasonable range, this study lays a foundation both theoretically and statistically for the simulation of contact parameters for Broussonetia papyrifera stalk harvesting processing, mechanical harvesting, and so on.