Mechanization of field experiments is the only way to improve crop breeding and seed propagation effects. In order to further clarify and improve the working performance of tapered threshing device for plot breeding, and reduce the remaining seeds in the device, the numerical simulation was carried out on the motion process of materials in the longitudinal-axial tapered cylinder threshing and transmission device of the plot wheat breeding combine harvester based on CFD-DEM method. Simulation results showed that, threshing and transmission of particles and short stalks at axial direction could be realized under the influence of air flow. Meanwhile, the material transference and distribution rule and stream field distribution rule of air flow in the threshing and transmission device were obtained, the variations of velocity and displacement of particles and short stalks with time were obtained; the motion trajectories and forms of particles in different types of retention were also studied. At rotating speed of 1300-1600 r/min for the tapered threshing cylinder in the verification test, the particle retention rate in the enclosure was 0-0.13%, while in the simulation the particle retention rate in the enclosure was 0-0.11%, only a 0.02% difference between them. The results proved a favorable feasibility to simulate the working performance of the tapered threshing and transmission device for plot breeding through gas-solid coupling method. Keywords: particle threshing and transmission, tapered threshing and transmission device, hydromechanics calculation, discrete element, numerical simulation, test DOI: 10.25165/j.ijabe.20191201.4458 Citation: Dai F, Song X F, Zhao W Y, Han Z S, Zhang F W, Zhang S L. Motion simulation and test on threshed grains in tapered threshing and transmission device for plot wheat breeding based on CFD-DEM. Int J Agric & Biol Eng, 2019; 12(1): 66–73.

Livestock dung, discarded crop straws, and residual plastic film are the primary agricultural non-point sources of pollution. For livestock dung and discarded crop straw, the general treatment focuses on compost, animal fodder, industrial raw material, and new energy. The development of degradable mulch film is the main way to solve pollution from residual plastic film. However, an effective way to solve the above three types of pollution simultaneously and use them for ecological circular agriculture has been less studied. In this study, using cow dung and flax straw wastes as raw materials, we prepared natural, fibre-based paper mulch using the rapid-Kothen method and analysed the film-forming mechanism. Based on the Van Soest method, the cow dung and flax straw waste contain abundant cellulose fibres: 36.75% and 54.69%, respectively. The tensile strength and tear strength of fibre paper mulch are 1.87 kN/m and 19.91 N/mm, respectively. To enhance the adaptability of the fibre paper mulch in humid environments, the surface of the mulch was treated with alkyl ketene dimer (AKD). The AKD-coated fibre paper mulch displays hydrophobic properties, indicated by a contact angle of 128° ± 2°. It has a wet tensile strength of 0.64 kN/m and a wet tear strength of 8.23 N/mm. Additionally, it exhibits a dry tensile strength and a tear strength of 2.13 kN/m and 16.43 N/mm, respectively. Notably, the dry tensile strength is increased by 16.31%. In this way, the livestock dung and discarded crop straw can be reused, reducing dung pollution and straw burning in livestock farms, and the final products can alleviate the residual film pollution simultaneously.

Fertilizer particles have strong hygroscopicity and agglomeration often occurs during their storage, which leads to a blocked phenomenon during the operation of the external grooved wheel fertilizer discharger. In this study, the bond model of fertilizer block was constructed based on the discrete element method (DEM) to further explore the effect of different working parameters of the spiral grooved wheel on the fertilizer discharge characteristics. According to the Box–Behnken experimental design principle, a three-factor and three-level simulation experiment was carried out with the factors of grooved wheel speed, grooved wheel section shape, and spiral rise angle. The simulation results showed the variation coefficient of fertilizer uniformity was affected, from important to secondary, mainly by the rotating speed of the grooved wheel, the cross-sectional shape of the grooved wheel, and the spiral rise angle. The broken rate of fertilizer block bond was affected, from important to secondary, mainly by the spiral rise angle, the cross-sectional shape of the grooved wheel, and the rotational speed of the grooved wheel. The optimal combination of working parameters was obtained by optimizing and analyzing the data; the rotating speed of the grooved wheel was 21 r/min, the scoop section, and the spiral rise angle was 70°. Under the best working parameters, the variation coefficient of fertilizer uniformity was 8.56%, and the broken rate of fertilizer block bond was 97.67%. The validation experiment results showed that the variation coefficient of fertilizer uniformity was 9.23%, the broken rate of fertilizer block bond was 94.28%, and the relative data error was less than 10%. The experimental results are close to the simulation results. The research results can provide a reference for the structural design and parameter optimization of spiral grooved wheel fertilizer discharger.

Simulation and test on separating cleaning process of flax threshing material based on gas-solid coupling theory

During maize production and transportation, maize kernels frequently interact with mechanical components. To accurately simulate the interaction process between maize and mechanical components, it is essential to establish a reliable maize kernel model and input precise contact parameters. This study established polyhedral discrete element models of different maize kernels and calibrated the contact parameters between maize kernels and steel plates using the inclined plane method. The coefficients of restitution, static friction, and dynamic friction between maize and steel sheets were measured to be 0.5, 0.545, and 0.213, respectively. Subsequently, the contact parameters between maize kernels were determined through steepest climb tests and central composite design response surface tests. Then, the above parameters were optimized using Design-Expert software. The coefficients of restitution, static friction, and dynamic friction between maize kernels were measured to be 0.318, 0.182, and 0.232, respectively. Finally, the optimized parameters were validated using the angle of repose experiment, which found that the relative error between the experiment and the simulation was only 1.24%. The results indicated that the obtained contact parameters were accurate and reliable.