Study On The Mechanism Of Needle-shaped Tea Leaves Based On Discrete Element Metho

Tea stripping is an important process in the process of tea processing,which is the key to tea shaping,and the crushed tea produced during the processing of tea strips seriously affects the quality and grade of tea.How to reduce the rate of tea stripping is an important problem that needs to be solved urgently in tea processing research.Therefore,it is urgent to carry out in-depth research on the mechanism of tea stripping,explore the movement law of tea strip particles in the pot groove,and reveal the mechanism of tea strip formation,which is of great significance for optimizing the structure of the tea strip strip and reducing the crushed tea rate.In this paper,needle-shaped single-bud tea processed by tea strips is taken as the research object,the motion law of tea in the pot is studied,the motion equation is established,and the influence of the structural parameters of the pot on the movement of tea particles is analyzed.By calibrating the contact parameters of needle tea particle discrete element simulation,univariate dynamics simulation was carried out,and combined with the needle tea particle bonding model,the influence of different factor parameters on the tea crushing rate in the process of tea stripping was analyzed.The main research contents and conclusions are as follows:(1)The tea particle model,its motion law and collision characteristics in the pot groove were analyzed.Three stages of the movement of tea particles in the pot were determined:the movement stage along the inner wall of the pot groove,the throwing stage and the collision stage;The force model of tea in the pot is established,and through the force analysis,the motion relationship of tea along the inner wall of the pot groove,the trajectory of the throwing motion and the collision effect are determined,and it is concluded that the reciprocating frequency of the pot groove,the angle between the pot baffle and the horizontal plane and the radius of curvature of the pot groove have significant effects on the movement of tea particles in the pot groove.(2)Study the discrete element simulation parameters of needle-shaped single-bud tea particles.Taking the needle-shaped tea particles in the process of tea strip processing as the research object,the needle-shaped tea particle model was established based on the approximation method of slicing technology,and the discrete element simulation contact parameters of needle-shaped tea particles were calibrated by combining the resting angle physical test and simulation test of the funnel injection method,and the optimal contact parameter combination was obtained by the Box-Behnken test optimization:the collision recovery coefficient between tea particles was 0.28,the static friction coefficient between tea particles was 0.15,and the rolling friction coefficient between tea particles was 0.10.(3)Based on EDEM software,the dynamic simulation of the strip movement of tea leaves in the pot trough was carried out.EDEM discrete element software was used to numerically simulate the process of tea in the pot groove,and the movement trajectory of tea leaves in the pot groove was obtained,as well as the average velocity and average force of tea particles in the pot under different factor parameters(pot groove reciprocating frequency,angle between pot groove baffle and horizontal plane and radius of pot groove curvature radius),which provided a theoretical basis for tea particle formation.(4)Study on the crushed tea rate of needle-shaped single-bud tea based on Bonding model.The needle-shaped single-bud tea particle bonding model was established,and the replacement of tea particles was realized by compiling the particle replacement API file,and combined with the relationship between the replacement object and the simulation time,it was determined that the single tea grain was composed of 388 small balls with a diameter of0.2mm and bond-bonds with certain mechanical properties between each other;The average ultimate breaking force of a single tea strip was 0.054N,and a simulation experiment was established in EDEM,and the bond-bond parameters were calibrated according to the principle of Bond-bond parameter calibration,and the normal stiffness coefficient,tangential stiffness coefficient,critical normal stress,critical tangential stress and bonding radius of tea grain bond bond were obtained according to the principle of bond parameter calibration,which were 6.12×10~7 N/m~3,5.16×10~7 N/m~3,8.12×10~4Pa,6.10×10~4Pa and 0.25mm,using local simulation,the effects of different pot groove reciprocating frequency,pot groove baffle angle and horizontal plane and pot groove curvature radius on tea crushed tea rate were studied,and the factor parameters were optimized through three-factor and three-level orthogonal test,and the optimal combination was obtained:pot groove reciprocating frequency 137.6r/min,pot groove curvature radius 42.79mm,pot groove baffle angle between pot baffle and horizontal plane 83.89°,tea crushed tea rate of 2.64%,the results met the requirements of the stripping mechanism.At the same time,in order to verify the accuracy of the simulation optimization results,the average tea crushing rate of the improved U-shaped pot trough strips was 2.76%,and the relative error with the optimization results was 4.35%,indicating that the test results and the optimization results had high consistency.