Development And Experimental Research On Vibration Grading Equipment For Machine-picked Fresh Tea Leaves

China is a big tea-producing country,and the tea industry is a characteristic and advantageous industry.By the end of the 13 th Five-Year Plan period,the area of tea gardens in 18 major tea-producing provinces in our country has reached more than 46 million hectares,the output of dry tea has reached more than 2.8 million tons,and the output value has reached more than 240 billion yuan.While the scale of the tea industry is growing rapidly,Chinese tea industry is generally faced with a problem of difficulty in picking tea.In traditional manual tea picking,the shape of the buds and leaves picked is complete,and the grades of fresh leaves are distinct,but the picking efficiency is low,and it is easily affected by the shortage of picking labor,bad weather,and the tea picking cycle.Changing the traditional way of picking fresh tea leaves is a key step for the transformation and upgrading of the tea industry.Mechanization of picking fresh leaves is the general trend,which meets the requirements of the tea industry to realize the development of smart tea gardens.At present,the tea picking machines commonly used in tea gardens use the non-selective rigid pic king principle,and adopt the method of reciprocating cutting with serrated blades or breaking fresh leaves with rotating blades.There are fresh tea leaves of all levels in the picked fresh leaves,ranging from single bud,one bud and one leaf,to one bud with three leaves,one bud and four leaves,and even broken leaves,tea stalks and non-tea fresh leaves.If the fresh leaves are not graded by machine,it will affect the tea withering,rolling,fermentation and other processing techniques,and affect the quality of the finished tea;and the tea leaves of different grades are mixed,so the tea resources cannot be fully utilized,and the price of the finished tea will be reduced,thus affecting the income of tea farmers.Therefore,the development and upgrading of fresh leaf grading equipment with the characteristics of good performance,high grading efficiency and accurate grading is very important.This paper takes the vibration classifier as the research object,expounds the classification principle of the classifier,and determines the key physical properties of tea leaves.The simulation test of the fresh leaf classification process of the classifier is carried out,and the influence of vibration parameters on the sieving rate of the classifier is analyzed.The prototype and the classification effect verification test were carried out.The main research contents are as follows:(1)A vibrating fresh leaf grading equipment was developed,and its grading principle was described.Combined with the grading principle,the relevant physical parameters such as the required fresh tea leaf size,shear force,compression force,friction coefficient were experimentally determined;Determine the vibration source and transmission mode;analyze the movement of fresh leaves on the screen surface under the action of vibration,and obtain the limiting conditions of the relevant vibration parameters of the classifier required for the classification of fresh leaves by machine.(2)A fresh tea leaf model based on the HWB contact model was proposed.According to the test results of the physical properties of fresh tea leaves,the parameters required for establishing the fresh leaf model and the simulation parameters were determined.The fast filling method was used to fill the internal particles of the fresh leaf model.A single factor simulation test was carried out on the three factors of amplitude,vibration frequency and vibration direction angle,and the optimal level interval of the three factors was obtained.The BBD method was used to design a quadratic regression orthogonal test with 3 factors and 3 levels.The results were analyzed and the results were optimized by the Design-Expert11.0 software.The optimal parameters were obtained: vibration frequency 29.0Hz,amplitude 9.0mm,vibration direction the angle is 34.7°.(3)A prototype of a vibrating fresh leaf classifier was built,and the inertial force incomplete balance method was used.The analysis and calculation showed that a balance block with a radius of 85 mm and a mass of 7.1kg should be installed on the crankshaft to debug the prototype.(4)The comparison and verification test of the classification effect of the classifier is carried out.The test results show that the classifier has a good classification effect on the fresh leaves collected by the machine,and the screening rate reaches more than 70%.It can reach more than 90%,which also verifies that the simulation test based on EDEM software has high reliability,and the correlation between the simulation value and the test value of the sieving rate is more than 93%.