To address the competing relationship between tuber damage and soil removal in potato combine harvesting, this study investigated the operating mechanism of a belt-rod type separator of a small-scale self-propelled potato combine harvester and the separation performance between tuber and soil. The main factors affecting the tuber-soil separation characteristics were derived from a theoretical analysis of the belt-rod angle, belt-rod linear velocity, and harvester forward speed. A simulation model based on DEM (Discrete Element Method)-MBD (Multibody Dynamics) coupling was constructed and single-factor simulation tests were carried out. Then a three-factor, three-level Box–Behnken test was conducted using the coefficient of force on the tuber and soil clearing rate as response indicators. The optimal combination of parameters resulting in low tuber damage and high soil clearing rate was obtained by solving the regression equations. The optimal parameters were a belt-rod angle of 17.5°, a belt-rod linear velocity of 1.37 m/s, and a harvester forward speed of 0.80 m/s. The simulation model was validated by field experiments and the error between the simulation model and the field harvest was found to be 3.81%. The results can be used as a reference for parameter optimization of small-scale potato combine harvesters and coupled DEM-MBD simulation of tuber-soil separation.

Mulching technology has created a major problem of agricultural plastic pollution. This is because the mulch is severely degraded by UV (ultraviolet) irradiation and the mechanical properties deteriorate, which makes mechanical recycling or manual recycling difficult. This study was conducted on m-LLDPE (metallocene linear low-density polyethylene) mulch films. The difference in mechanical properties of specimens in the TD (transverse direction) and PD (parallel direction) was investigated, and the changes in the mechanical properties after UV irradiation were compared. Finally, an initial mulch mechanical property evaluation model was developed to adapt to different recovery machines and crop agronomic requirements. The results suggest that the mechanical properties of m-LLDPE mulch films were strongly influenced by the film thickness, and also showed directional differences in tensile and tear properties. After UV irradiation, the mechanical properties of the specimens were enhanced after a short period of time, but the overall trend was a non-linear decay which gradually slowed down with time.

Most potato harvesting in China requires haulm removal. The properties of the tubers change after haulm removal. Investigating the effects of different haulm removal times on the physical mechanics and collision damage characteristics of potato tubers during the harvest period can provide a reference for reducing the damage rate of potato tubers during mechanical harvesting. The Longshu No. 7 potato, which is widely grown in northwest China, was selected as the experimental object in this study. The tuber parameters of the physical mechanics and collision damage characteristics for four different haulm removal dates (0, 7, 10 and 14 days before harvesting) were experimentally determined. The results showed that with the increase in haulm removal time before harvesting, the rupture pressure, Young’s modulus, and shear modulus increased significantly. The coefficient of restitution decreased significantly. Additionally, when multiple potato tubers fell on the steel plate in the EDEM simulation test, the maximum force of a single tuber with the largest resultant force and the maximum contact force of all tubers were affected significantly. Both showed significant downward trends. The results of this study can provide a reference for discrete element simulation parameters related to potato harvesting machinery. It can also provide a reference for determining the time to haulm removal during the actual harvest.

Uniform crushed straw throwing and seed-sowing machines can achieve the processes of straw chopping, straw transport, sowing, fertilization, and straw mulching at the same time, which is widely used in many areas of China. Conveying device is one of the important components used to convey, elevate and throw straw. However, the problems of high power consumption and congestion affect the promotion of the machine. Therefore, the conveying device of uniform crushed straw throwing and seed-sowing machine was analyzed in order to determine its device operation mechanism. Kinematic and dynamic analyses of particles of crushed rice straw during lifting and dispersion are used to develop a flexible-body model of rod-shaped and agglomerate-shaped crushed straw and a coupling model including the mechanical structure of the device. By integrating computational fluid dynamics and the discrete element method, the gas-solid coupling theory in numerical simulations and motion analysis of crushed straw particles is used to determine how the flow field and motion characteristics affect the conveying performance. Besides, regression equations to describe the relationships between the factors and each assessment index were established by using the regression analysis and response surface analysis with the software Design-Expert. The effect of throwing blade speed X1, conveying volume of crushed straw X2, and pipeline diameter X3 on the throwing speed of crushed straw Y1 and specific power consumption Y2 were investigated. The highest throwing speed of crushed straw and lowest specific power consumption are the optimization goal .The results of optimization showed that the predict the best optimal parameters were 2000 r/min throwing blade rotational speed, 1.4 kg/s conveying volume, and 220 mm pipeline diameter, the planter achieved a throwing speed of 12.2 m/s and specific power consumption of 9179 m2/s2. And then a field test verification was conducted. The planter achieved a throwing speed 12.4 m/s and specific power consumption 9070 m2/s2 while selecting the best optimal parameters. Thus, the optimal parameters can provide a high-performance operation and satisfy the actual operation requirements The results provide a theoretical basis and data support for seeding technology innovation and equipment optimization to ensure uniform crushed straw throwing in dense rice stubble fields. Keywords: rice straw stubble, uniform crushed straw throwing, coupled CFD-DEM, response surface analysis DOI: 10.25165/j.ijabe.20231606.7057 Citation: Gu F W, Zhao Y Q, Hu Z C, Shi L L, Wu F, Xu H B, et al. Operation analysis and parameter optimization of the conveying device for uniform crushed straw throwing and seed-sowing machines. Int J Agric & Biol Eng, 2023; 16(6): 28–36.