| Linear vibrating screen is one of the most commonly used screening equipment in material grading operations,and is widely used in food,chemical,building materials,medicine,and other industries.Screening efficiency and screening processing capacity are two important performance indicators of screening equipment.The improvement of one performance indicator is restricted to some extent by the other.However,research on screening performance optimization mainly focuses on the improvement of screening efficiency,while there is relatively little research on taking both indicators into account,which affects the overall performance optimization of the screening machine.In addition,the study of the laws of material movement on the screen surface,as well as the mapping relationship between screening parameters and screening performance,are key to effectively improving screening performance.Based on the discrete element method model and the coupled model of computational fluid mechanics-discrete element method,the numerical simulation of the screening process of the particles on the screen surface of linear vibrating screen was carried out.The influence of the air flow generated by sieve plate vibration on the motion characteristics and screening performance of the dry fine particles on the screen was studied,and the relationship between the screening parameters and different screening performance indexes was analyzed.According to the screening results obtained based on the coupled model of CFD-DEM,the mathematical model of screening parameters and screening performance was established to optimize the comprehensive performance of screening equipment.The main contents are:(1)The motion and penetration probability of the particles in the screening process are analyzed comprehensively.Based on the basic principles of discrete element method and computational fluid mechanics method,a CFD-DEM coupling simulation model of linear vibrating screen was established.The evaluation indexes of screening performance are defined.(2)Through the simulation of sieve plate vibration process,it is found that sieve plate vibration generates airflow,and the airflow velocity changes with the screening process.Three parameters of single particle size,particle group feeding rate and particle shape were selected for single factor test to explore the changing rule of material particle movement on the screen,and determine and analyze the influence of air flow on material particle movement on the screen in the process of screening.The material screening experiment was carried out by the experimental prototype with adjustable parameters,and the simulation results were compared and analyzed,which proved the reliability of the simulation model.(3)The amplitude,vibration frequency,vibration direction angle,screen surface angle and feed rate as the five main parameters of the linear vibrating screen,the design of single factor test to explore the impact of the screen parameters under the air flow on the screening performance,and analyze the relationship between the screening parameters and screening performance.At the same time,the main and secondary order of sieving parameters’ influence on sieving performance was analyzed by orthogonal experiment.(4)According to the simulation results,the sparrow search algorithm(SSA)was used to optimize the weight and threshold of BP neural network,and the prediction model of SSA-BP neural network with higher prediction accuracy was obtained,so as to obtain the prediction model of screening parameters on screening efficiency and processing efficiency.Then,multi-objective genetic algorithm is used to optimize the screening performance of the screening machine,and a parameter combination scheme for comprehensive performance was obtained. |
