Optimizing mechanized cleaning of Corcyra cephalonica eggs for stored-product biocontrol via DEM parameter calibration and enhanced vibratory separation

Efficient mechanized separation of Corcyra cephalonica eggs from impurities (appendages, scales, and dust) remains a major bottleneck in the mass production of Trichogramma wasps for the biocontrol of pests such as Chilo suppressalis. Here, discrete element method (DEM) parameter calibration is integrated with vibratory screening optimization for egg–impurity mixtures. Multi-factor experiments were conducted to quantify the intrinsic properties of C. cephalonica eggs (density: 1.043 g·cm⁻3, elastic modulus: 3.34 MPa) and to determine key pneumatic separation thresholds. Based on suspension velocities, a feasible air velocity window of 0.4–4.6 ms⁻1 was identified (eggs: 0.8–2.3 ms⁻1, appendages: 2.4–4.6 ms⁻1, scales: 0.4–0.8 ms⁻1). DEM contact parameters (egg–egg dynamic friction, egg–steel static friction, and surface energy) were calibrated using the angle of repose as the response variable, yielding good agreement between experiments and simulations (22.37° vs. 23.19°, relative error: 3.7%). To our knowledge, this parameter set constitutes the first DEM database tailored to C. cephalonica eggs. Using the calibrated model, EDEM simulations were performed to evaluate key vibratory screening factors. The screening rate exhibited a non-monotonic dependence on vibration frequency, with an optimum at 12 Hz (78%·s⁻1). It peaked at an amplitude of 1 mm (77%·s⁻1), and optimization of the cone pendulum angle (defined as the inclination angle of the conical pendulum) showed a maximum screening rate of 81%·s⁻1 at 1.2°. Moreover, ultrasonic assistance improved the screening rate by up to 15% (at 12 Hz and 1.5 mm), likely by reducing particle agglomeration. Overall, the calibrated DEM parameters and the identified operating windows (airflow velocity, vibration frequency/amplitude, and pendulum angle) provide quantitative guidance for the design of vibratory screens and pneumatic separators for host egg cleaning, thereby supporting the automation and scalability of Trichogramma-based biocontrol for stored-product pests.