Numerical Simulation Study Of Screw Conveying Process For Non-spherical Material Based On DEM

Screw conveying is an important form of continuous conveying in modern industry and has great advantages in conveying bulk materials.Therefore,an in-depth understanding of the material motion law is of great significance for optimizing the related industrial transportation process.At present,along with the development of computer technology,numerical simulation has become a key method to study the complex flow mechanism of particle system,among which Discrete Element Method(DEM)is an effective numerical simulation method to study the continuous material conveying process.However,most of the current DEM numerical simulations of screw conveyors are based on the spherical particle model,and the study of non-spherical material conveying process is still lacking.In this paper,the flow characteristics of materials,particle collisions,conveying performance and wear of equipment are studied using a DEM model that can accurately describe the motion of non-spherical particles and a linear elastoplastic model that can accurately determine the contact of viscoplastic particles,within a horizontal screw conveyor commonly used in screw conveying.The main studies are as follows.(1)The influence law of particle sphericity and operating parameters on conveying process when conveying non-spherical materials is explored.The accuracy of the super-ellipsoid model used in this paper is demonstrated by experimental verification of the super-ellipsoid particle model through screw conveying experiments and simulation results.The flow characteristics of nonspherical materials in the equipment are obtained by analyzing the velocity distribution and force distribution of particles with different sphericity in the conveyor,and the influence mechanism of particle sphericity and operating parameters on the conveying performance of the equipment is determined.Based on the analysis of the results of particle collision energy,the relationship between particle sphericity and energy dissipation rate is explored and the main causes of particle fragmentation are revealed.Based on this,the SIEM wear model is coupled to analyze the wear of the equipment,and the wear distribution of the spiral blades and the total wear of the equipment are predicted.(2)The influence of particle aspect ratio on the conveying process is revealed in the screw conveying process of rod-shaped materials.The experimental validation of the rod particle model is carried out through relevant experiments and simulations,and the validation results show that the model has high precision and accuracy.The motion characteristics of rod-shaped particles in the spiral conveying process and the influence of the length-to-diameter ratio on the volumetric efficiency and throughput of the equipment when conveying different rod-shaped particles are investigated.By studying the orientation and flow characteristics of rod-shaped particles under different operating conditions,the preferential orientation range and velocity distribution of rodshaped particles in spiral conveying were obtained,and the relationship between rod-shaped particle aspect ratio and operating parameters and particle breakage was investigated.(3)The influence law of plasticity and viscosity parameters on material conveying process when the conveyor belt is viscous and plastic material is studied and obtained.The experiments use the lift-cylinder method to measure the rest angle of soil with different moisture content to compare with the simulation results,which proves the accuracy of linear elastic model for contact detection of materials with viscous and plastic.Based on the simulation results of inter-particle flow characteristics,force distribution and overlap amount,the mechanism of the influence of viscous and plastic stiffness on inter-particle agglomeration phenomenon was obtained.By analyzing the collision spectrum and energy consumption of the equipment,the process parameters with lower inter-particle collision energy and lower energy consumption of the equipment are obtained.Synthesizing the above,this paper has conducted a systematic study on screw conveying of non-spherical and viscous materials and the influence mechanism of flow properties and equipment conveying performance during material conveying,and the research results can provide theoretical guidance for screw conveying equipment.