To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River, which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge, research on the crushing mechanism of caking compound fertilizer was performed. Considering that it is difficult to measure the bonding force between caking fertilizer particles directly, a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software. To decrease error between the simulation and physical test results, the normal contact stiffness, tangential contact stiffness, critical normal stress, critical tangential stress, bonding radius, and other parameters of the bonding model of caking composite fertilizer were calibrated. The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning, the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer, and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test, steepest ascent test, and Box-Behnken test. The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296% and 0.343%, respectively. Using the crushing rate of caking compound fertilizer as an evaluation index, the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape. The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81% and 5.06%, respectively, indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model. These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.

Existing rape combine harvester with a cyclone separation cleaning device has the challenge that the loss rate and the cleaning rate increase and decrease simultaneously. A cleaning process route was proposed, which involves the cyclone separation cleaning device removing light and tiny impurities, and the cylinder sieve device removing coarse and long impurities such as pod shells and short stems. A novel cleaning system combining the cyclone separation cleaning device and cylinder sieve cleaning devices was designed. The ranges of the structure and operation parameters for each component were analyzed based on kinematics and dynamic analysis. A four-factor five-level quadratic orthogonal test was carried out, in which the loss rate and cleaning rate were taken as the evaluation indexes. The velocity at the suction port, the rotation speed of the cylinder sieve, the screw pitch of the spiral blade and the diameter of the sieve hole were taken as the influencing factors. The orthogonal test results showed that the cleaning system performed best at a rotation speed of the winnower is 600 r/min, an airflow velocity at the suction port is 18.25 m/s, a rotation speed of the cylinder sieve is 87 r/min, a screw pitch of the spiral blade is 440 mm and a diameter of the sieve hole is 4.48 mm. At this time, the loss rate of the cleaning system is 3.22%, and the cleaning rate is 95.67%. Compared to the conventional cyclone separation cleaning device, the loss rate is reduced by 2.17% and the cleaning rate is increased by 1.05%. This study can provide a reference for the optimal cleaning system design for rape combine harvesters.

The relationship between the parameters of the bonded-particle model and the macroscopic properties of oilseed rape shoot stalk provides valuable insights into the interaction between the stalks and harvesting machinery. In this study, a discrete element model of oilseed rape shoot stalk was constructed using a method that combined ordered and bimodal distribution filling. The model’s six contact and five bonding parameters were calibrated based on physical and simulated diametral compression tests. The Plackett-Burman design was employed to screen the effects of the parameters on the rupture force. The range of significant parameters was determined using the steepest ascent test. Furthermore, by calculating the second-order regression model and analyzing the significance of parameter combination using the central composite design method, the optimal parameter combination was identified, including a bonded disk radius of 0.78 mm, a normal stiffness per unit area of 4.61×10⁷ Pa, a shear stiffness per unit area of 5.21×10⁷ Pa, and a coefficient of static friction between particles of oilseed rape shoot stalk of 0.47. The simulated rupture force (58.80 N) differed by 6.5% from the average value of the physical test (62.92 N), and the deformation of the compression process was consistent. The results demonstrate that the model effectively reflects the mechanical failure properties of oilseed rape shoot stalk during the diametral compression, providing a reference for modeling other crop stalks and aiding in the study of interactions between clamping-transporting devices and stalks during harvesting.