Experimental research on a propeller blade fertilizer transport device based on a discrete element fertilizer block model

In organic fertilizer application, it is difficult for existing chain-type fertilizer transport devices to cut and break organic fertilizer blocks during operation. The fertilizer transport process does not effectively disturb the fertilizer group, and it is easy to cause fertilizer overhead, which makes the subsequent fertilizer spreading and deep application process unable to operate normally. In addition, the lack of a solid organic fertilizer numerical simulation model restricts the innovation of organic fertilizer application equipment. Because of the above problems, based on the physical characteristics of the manure, this paper establishes a simulation model of a manure block through the Hertz-Mindlin with bonding (HMB) contact model in the discrete element method (DEM), calibrates the bonding parameters of the organic fertilizer by combining the uniaxial compression physical test and the simulation test, and verifies the calibrated bonding parameters by the load–displacement test and the deformation test of organic fertilizer. Through parameter optimization, the unit normal stiffness (UNS) is 11.27 × 107N/m3, unit shear stiffness (USS) is 4.17 × 107N/m3, critical normal stress (CNS) is 3.40 MPa, critical shear stress (CSS) is 1.25 MPa, and bonding radius (BR) is 2.80 mm. The relative error of the maximum load (ML) is 8.7%, and the relative error of the displacement is 3.2%, as verified by the bench test. This paper proposes a propeller blade (PB)-type organic fertilizer crushing and transporting device, and the structural parameters of the PB are simulated based on the calibrated organic fertilizer model. The optimal parameter combination after the optimization of the PB is obtained as follows: the blade inclination angle is 42°, the blade spacing is 227 mm, the blade speed is 89 r/min, and the blade height is 205 mm. The machine is processed, and the field test is carried out. The results show that the average oil pressures of the stable fertilizer crushing process under the half-speed and full-speed modes are 11.06 MPa and 12.01 MPa, respectively. The minimum oil pressure is 8.89 MPa and 10.90 MPa, respectively, the average energy consumption is 2.71 kW and 5.42 kW, respectively, and the proportion of the particle size of the organic fertilizer after crushing is more significant than 92.4%. The quality of the crushed fertilizer is high and can be used in crushed fertilizer applications.