Discrete Element Model of Different Moisture Hygroscopic Fertilizer Particles

The discrete element computer simulation method is an effective tool that enables the study of the interaction mechanism between the fertilizer discharge device. However, the lack of accurate fertilizer models for hygroscopic fertilizer particles (HFP) has limited the application and development of the discrete element method in research precision fertilizer discharge device. Taking HFP as the research object, this research aims to establish the discrete element model of different moisture hygroscopic fertilizer particles, and to develop a method for predicting the discrete element parameters of HFP based on moisture content. The Hertz–Mindlin with JKR discrete element model was selected as the contact model for the HFP. The repose angle of HFP was used as the test index to select nine discrete element models for the HFP. Firstly, a mathematical model characterizing the relationship between fertilizer moisture content and the repose angle was established. Subsequently, the Plackett–Burman test identified the surface energy of hygroscopic fertilizer particles (HFP), the restitution coefficient between fertilizer and PC board, and the shear modulus as significant factors influencing the test index. The value range of the above parameters were determined by the steepest ascent test results. The Box–Behnken test obtained the regression model between the significant factors and the test index. The optimal combination of parameters of 2%, 4%, and 6% moisture contents of HFP were predicted based on the regression model and the HFP repose angle. The parameters were optimized using the repose angle error as the target. In order to further verify the accuracy of the HFP discrete element model, a fertilizer discharging simulation test was conducted. The results show that, compared with the actual fertilizer discharge amount, the simulation fertilizer discharge amount error of different moisture HFP was below 8.32%. The collective results indicated this method could reliably and precisely establish the discrete element model of various moisture content HFP. This model can be applied to the analysis of hygroscopic fertilizer discharging processes and the design of precision fertilizer discharge technology devices.