Study of the grain particle-conveying performance of a bionic non-smooth-structure screw conveyor

The screw conveying of agricultural materials is an important part of agricultural production that affects the operational efficiency of combine harvesters. The friction between materials and screw blades is an important factor hindering the improvement of conveying performance. The drag reduction effect of bionic non-smooth (BNS) surfaces has been verified in many fields, but its effect in granular material conveying is unknown. In this research, two kinds of BNS structures, namely concave and convex structures, were designed on traditional smooth spiral blades. Virtual simulation experiments were carried out with EDEM (2020, DEM-Solutions Ltd., UK) software by establishing a virtual model of the screw conveyor. By comparing the conveying performance of screw conveyors installed with conventional smooth blades and BNS blades, the best-performing concave shape was selected as the BNS structural unit. Based on the orthogonal test method, the conveying performance of models with different structural parameters was compared. The best conveying performance was achieved with the pit diameter D of 4 mm, the pit axial distance Dx of 10 mm, and the radial pit distance Dy of 3 mm. In this case, compared with the conventional structure (CS), the average axial velocity of the particles was increased by 16.07%, the filling coefficient was increased by 6.89%, the mass flow rate was increased by 26.39%, the average power was reduced by 80.34%, and the average squeezing force on the particles was reduced by 72.49%. On this basis, a test rig and signal monitoring system were built, and the results of the test were found to be consistent with the simulation results. The concave BNS structure changes the flow state of particles and effectively improves the grain-conveying performance of the screw conveyor. This study provides new ideas and methods to improve the performance of screw conveyors for conveying granular materials.