Study on the Mechanism of Urea Arch Breaking in Vibrating Fertiliser Dischargers Based on EDEM

Urea discharge can become unstable as interparticle cohesion increases under moisture-affected conditions. This study combined bulk-solid mechanics, discrete element method (DEM) simulations, contact parameter calibration, and bench testing to investigate urea arching and vibration-assisted discharge. Dry-contact parameters for urea particles and a polypropylene (PP) hopper were calibrated using angle-of-repose and sliding tests. The calibrated simulations differed from the physical target values by 1.71% for the angle of repose and 3.98% for the sliding friction angle. In a separate DEM sensitivity analysis, JKR surface energy was prescribed at 0, 0.05, 0.15, and 0.30 J·m−2 as an effective adhesion parameter rather than as a calibrated moisture state. The maximum EDEM-exported Total Force signal increased from 2.283 N at 0 J·m−2 to 2.704 N at 0.30 J·m−2 (18.5%), whereas the mean particle velocity during the common 5–18 s pre-discharge interval decreased from 0.0613 to 0.0397 m·s−1 (35.3%). Two combined excitation settings were evaluated: 29.17 Hz/0.2 mm and 58.33 Hz/1.2 mm. Because frequency and amplitude changed simultaneously, their individual effects could not be isolated. The bench tests yielded mean discharged masses of 566.808, 492.435, and 464.305 g for the 58.33 Hz/1.2 mm, 29.17 Hz/0.2 mm, and non-vibrating conditions, respectively. The 58.33 Hz/1.2 mm setting increased the mean mass discharged during the 30 s collection interval by approximately 22.1% relative to the non-vibrating control. The corresponding between-run coefficients of variation were 3.628%, 3.580%, and 4.303%; these values describe repeatability between replicate runs rather than temporal or spatial discharge uniformity. Overall, increasing prescribed adhesion reduced particle mobility in the DEM simulations, whereas the 58.33 Hz/1.2 mm combined excitation increased discharged mass under the tested conditions. The experiments do not directly demonstrate crystal bridge rupture or isolate an independent frequency effect.