Design And Experiment Of Double Non Parallel Vibrating Screens

As an important part of grain combine harvester,the function of cleaning device is to use airflow and vibrating screen to realize the separation of grain,to obtain clean grain,and to reduce the labor intensity of labors.Nowadays,the vibrating screen can be roughly divided into planar reciprocating vibrating screen and multi-DOF vibrating screen.Most of the existing grain vibrating screens use parallel installation of double screen for grain screening,and mostly focus on single screen of grain screening effect of the study,the screening performance of double non parallel planar vibrating screen has not been reported.The motion state of vibrating screen directly affects the movement of the material on the screen,and then affects the screening effect.In order to improve the cleaning performance of maize grain harvester,a multi-DOF double non parallel vibrating screen is designed based on the bias crank slider mechanism.Under the condition that the screen is the same as that of the traditional parallel planar reciprocating vibrating screen and the installation position is consistent,the circular hole screen with high grain cleaning rate after cleaning is selected as the upper and lower clearance screen,and the shell screen with good performance of miscellaneous residual push is selected as the tail screen.The influence of the mechanism factors of double non parallel vibrating screens on the movement and screening performance of the material on the screen is investigated by means of experimental analysis and optimized.The research process is supported by the National Natural Science Foundation of China(51475090),the National Key Research and Development Program(2018YFD0300103),Heilongjiang Science Foundation(E2017004)and the Key Laboratory of Heilongjiang Province for Modern Agricultural Equipment in Northern Cold Areas.The main research contents and conclusions of this paper are as follows:(1)In view of the parallel mounting mode of the upper and lower screen of the planar reciprocating vibrating screen,the screening movement form is unitary and effective utilization rate of the screen is low,a double non parallel vibrating screen which can be flattened along 3 directions of space and swung around the hinge contact in front of the screen is designed based on the bias crank slider mechanism.By using matrix analytic method,the motion equation of screen is obtained,and the influencing factors of screening performance are determined.(2)By comparing the MATLAB numerical simulation results of the motion law of the screen with the simulation results of ADAMS virtual prototype,the correctness of the motion equation of the screen is verified,and it is determined that the screen movement of the vibrating screen driven by this mechanism is a non-harmonic form,which has different motion characteristics along the longitudinal points of the screen.(3)Through single factor experiment study,the influence of various influencing factors on grain loss rate and cleaning rate after screening is determined,and the parameter range selection of multi-factor experiment is provided.The results showed that the grain loss rate increased gradually with the increase of the mounting inclination of the upper screen,decreases first and then increases with the increase of the installation spacing of the screen,decreases first and then increases with the increase of the transverse amplitude of the screen.The grain cleaning rate increases first and then decreases with the increase of the mounting inclination of the upper screen,rises first and then decreases with the increase of the installation spacing of the screen,rises first and then decreases with the increase of transverse amplitude of screen.(4)According to GB/T 21962-2008 maize harvesting machinery technical conditions,the grain loss rate and cleaning rate were selected as the experiment index.The experiment data of each factor is analyzed by the response surface method,and the regression mathematical model of the index is determined.Using Design-Expert software,the regression mathematical model is optimized by multi-objective,and the optimal parameters of the mechanism are combined as: the mounting inclination of the upper screen 3.0°,the installation spacing of the screen is 293.0 mm,and the transverse amplitude of the screen is 5.6 mm.(5)According to the optimized parameter to carry out the experiment,the results show that: when the feeding amount of maize extract is 5.05 kg/s,the grain loss rate and cleaning rate after screening of the double non parallel vibrating screen are 1.61% and 97.83% respectively.Compared with the traditional parallel planar reciprocating vibrating screen cleaning device,the grain loss rate decreased by 1.59% and the grain cleanliness rate increased by 0.18%.In this paper,presents a double non parallel vibrating screen driven by the bias crank slider mechanism,accurately analyzes the actual motion form of the screen,and reveals the influence of the mounting inclination of the screen,the installation spacing of the double screen and the transverse amplitude of the screen on the screening performance of the double non parallel vibrating screen.