In view of the lack of accurate model in the discrete element study during straw comprehensive utilization (crushing, mixing, and baling), wheat straw was taken as the research object to calibrate the simulation parameters using EDEM 2023. The intrinsic and contact mechanical parameters of wheat straw were measured, and a test of the angle of repose (AOR), extrusion test and bending test were carried out. On this basis, a discrete element model (DEM) of hollow flexibility by using cylindrical particles was developed. The optimal combination of contact mechanical parameters was obtained through AOR tests based on the Box–Behnken design (BBD), coefficients of static friction, rolling friction, and restitution between wheat straw and wheat straw-45 steel are separately 0.227, 0.136, 0.479, 0.271, 0.093, and 0.482, AOR is 18.66°. Meanwhile, optimal combinations of bond contact parameters were determined by the BBD. The calibrated parameters were used to conduct extrusion and bending tests. Results show that the average values of peak extrusion force and peak bending pressure are 23.20 N and 3.92 N, which have relative discrepancy of 3.25% and 3.59% compared to physical test measurements. The results can provide model reference for the optimization design such as feed processing equipment, baler, and mixer.

The hopper is an important piece of basic equipment used for storing and transporting materials in the agricultural, grain, chemical engineering, coal mine and pharmaceutical industries. The discharging performance of hoppers is mainly affected by material properties and hopper structure. In this work, the flow capacity of cylindrical pellets in the hopper with the unloading paddle is studied. A series of numerical simulation analyses with the aid of the discrete element method (DEM) platform are carried out. Then, the discharging process is illustrated, and the flow capacity of pellets in the hopper is analyzed by the mass flow index (MFI), the dynamic discharging angle (DDA) formed in the discharging process and porosity among pellets. Furthermore, the effect of parameters such as hopper half angle, rotation speed of the unloading paddle and outlet diameter of the hopper is investigated. The results show that MFI increases with an increase in hopper half angle or outlet diameter and a decrease in rotation speed. Meanwhile, DDA and porosity decrease with the increase in the hopper half angle or outlet diameter and the decrease in the rotation speed. Finally, the MFI ~0.24 is identified as the criterion to distinguish the mass flow from the funnel flow for the hopper with an unloading paddle, and the optimization results are decided as follows: hopper half angle greater than 60°, outlet diameter greater than 60 mm and rotation speed between 45 rpm and 60 rpm. These results should be useful for providing a theoretical reference for the optimization design of feeding devices for swine feeders.

Aiming at the problems of low efficiency and poor cleaning quality in the cleaning process of harvested tiger nuts (Cyperus esculentus) with lots of soil and fibrous roots on the surface to meet the demand for mechanized harvesting of tiger nuts in the Yellow River, Huaihe River, and Haihe River regions in China, a pulsating roll-cleaning device was devised. The analytical software for meshing the transmission of pitch curves of elliptical gears with arbitrary orders was developed based on Visual Basic 6.0, thus obtaining a pair of elliptical gears that meet the steady transmission requirement. The meshing of this pair of elliptical gears enables pulsating variable-speed rotation of a brush roller, which reduces the breakage and accumulation of tiger nuts. Circular screen holes are distributed uniformly on the upper and lower cylindrical walls. Tiger nuts are cleaned under friction with the brush roller and the circular screen holes, while residues (including soil) fall in the settlement and accumulation tank through the screen holes, which realizes the rapid discharge and collection of residues, including soil, and reduction of dust. The separation process of soil from tiger nuts in the cleaning device was studied using RecurDyn 2023-EDEM 2022 simulation software. Taking the rate of rotation of the brush roller, order of elliptical gears, and eccentricity of the elliptical gears as the test factors while taking the cleaning efficiency, breakage rate, and impurity rate as the evaluation indices, a test bench for the cleaning performance of tiger nuts was established. Design-Expert V8.0.6 was applied to carry out a three-factor three-level Box–Behnken design (BBD) using response surface methodology (RSM), thus ascertaining the optimal parameter combination of the cleaning device. When the rate of rotation of the brush roller, order of elliptical gears, and eccentricity of the elliptical gears are, separately, 280 rpm, 2, and 0.122, the cleaning efficiency, breakage rate, and impurity rate of tiger nuts are 1.83 t·h⁻¹, 0.15%, and 0.16%, respectively. This satisfies the cleaning requirement of tiger nuts and provides a basis for the design of cleaning machines for tiger nuts.

Design and optimization of the seedling needle and push device for a mechanical transplanter of seedlings from bowl-type trays made of paddy straw