Investigation of the gas-solid two-phase motion in the cleaning device with imitating the pigeon feather sieve based on the CFD-DEM method

Screening is crucial in combine harvesters. To clean maize mixture at a high feed rate, a bionic sieve inspired by pigeon feather microstructure was designed. Using computational fluid dynamics (CFD)-discrete element method (DEM), results revealed the airflow above the bionic sieve increased, then decreased, then increased from front to rear, and was enhanced by 0.07, 0.06, and 0.1 m s⁻¹ at the front, middle, and tail compared to the plane sieve. Single-factor tests evaluated the influence of height of sieve shaft, velocity of inlet airflow, and angle of inlet airflow on process indices of stratification degree and separation degree of maize grains and impurities, and final indices of cleaning percentage of maize grains (CPMG), loss percentage of maize grains (LPMG) and velocity ratio of grains penetrating sieve holes (VRGPSH). Results showed parameters of sieve structure and inlet airflow significantly affected final indices (P < 0.05), except angle of inlet airflow on VRGPSH (P = 0.06179). The separation degree of maize grains and impurities showed strong positive correlations with CPMG and LPMG, but only showed medium positive correlations with VRGPSH. The stratification degree of maize grains and impurities showed weak positive correlations with CPMG, weak negative correlations with LPMG, and medium positive correlations with VRGPSH. At a high maize mixture feed rate of 7 kg s⁻¹, the bionic sieve improved CPMG by 2.02 % and reduced LPMG by 0.53 % compared to the plane sieve. This study proved the feasibility of using the bionic structure to optimise the cleaning device of separating large-fed mixtures.