Parameter Optimization Of Tea Plane Circular Screen Based On EDEM

The tea plane round screen machine is one of the tea refining and processing equipment.It can remove the fine impurities such as leaf dust and leaf stalk in the downward spiral motion track along the screen surface through the plane circular motion and the inclined screen surface with a certain size of screen holes,according to the different overall dimensions of tea particles,tea dust and tea stems,so as to improve the quality of finished tea.At present,the design of tea plane round screen mostly relies on traditional experience,and the key structural parameters have not been optimized,which affects the screening performance.Therefore,this subject uses EDEM software to quantify the force and motion law in the tea screening process,simulates and analyzes the key structural parameters of the round screen,and verifies the simulation results through single factor tests.Taking the structural parameters that have a great impact on the screening performance,such as the net screening rate and the error screening rate,as the optimization variables,the quadratic orthogonal rotation combination test is designed to optimize the independent variable parameters,in order to obtain the best working parameter combination that is conducive to the tea screening process of the round screen machine,and to provide a theoretical basis for improving the screening quality of the tea leaf plane round screen machine.The main work of this paper is as follows:1)The physical parameters such as water content,angle of repose,density,static friction angle and dynamic friction coefficient of tea were measured.The results showed that the water content was 6%-7%,the angle of repose was 30.7~o,the density was 481.8 kg/m~3,the static friction angle was 30.2~oand the dynamic friction coefficient was 0.348.2)The three-dimensional model of the tea plane round screen machine is designed and established by Solidworks software.The modal analysis of the frame of the round screen machine is carried out by using ANSYS Workbench software to test whether the frame will resonate with the screen surface.Taking the tea particles as the research object,the force and motion law of the tea on the screen surface are analyzed,and it is concluded that the motion trajectory of the tea is spirally downward along the screen surface.According to the technological conditions that the tea needs to continuously produce relative movement with the screen surface without throwing movement,the optimal value range of the rotating speed of the round screen machine is obtained.3)The EDEM software is used to model the tea particles,tea powder and tea stems,and the numerical simulation of the screening process is carried out with the imported virtual model of the screen body.The velocity,acceleration and force of the tea movement on the screen surface are quantified,and the kinematics and dynamic curves under different structural parameters are obtained.Combined with the curves,the influence of different parameters on the screening performance indexes of the circular screen machine,such as the net screening rate and the error screening rate,is analyzed,The screening mechanism of the circular screen is further revealed.4)The single factor test is designed to verify the simulation results,and the quadratic orthogonal rotation combination test of 3 factors and 3 levels is designed by using the design expert software to optimize the key structural parameters of the circular screen machine.The interaction between the factors and the significance order of influencing the screening performance are analyzed by combining the response surface.The test results show that the interaction between independent variables is significant,and the order of influence on the screen clearance is the turning radius,turning frequency and screen surface inclination;The order of influence on the error screening rate is screen surface inclination,turning radius and turning frequency.Taking the maximum screening rate and the minimum false screening rate as the optimization objectives,the multiple quadratic regression equation is solved.It is obtained that when the optimal parameter combination is the turning radius of 39 mm,the turning frequency of 3.1 Hz,and the inclination angle of the screen surface of 5.8~o,the screening rate is 98.5%and the false screening rate is3.47%.At this time,the screening effect is the best.The validation test of tea plane circular screen machine is designed with the optimal combination of structural parameters,and the test results are basically consistent with the parameter optimization results.