Motion Simulation And Experimental Study Of Agricultural Materials In 3-DOF Air-and-screen Cleaning Device

The cleaning of agricultural materials existed in all aspects of agricultural production,harvesting and reprocessing.With the continuous improvement of crop varieties and other conditions,the cleaning device was increasingly developing to high efficiency,high cleaning rate,low loss rate and low power consumption.The parallel vibrating screen was the key to significantly improve the screening quality and efficiency of agricultural material because it can achieve multi-dimensional vibration,which was conducive to efficient screening.Air-and-screen cleaning was the most common way in the agricultural material selection.The existing research on parallel vibrating screen mostly ignores the effects of airflow.In this dissertation,the airflow was introduced to participate in the screen process based on the study of three-dimensional parallel vibration screening,and the screening mechanism of agricultural materials on 3-DOF vibrating screen in gas solid two phase flow environment was studied.The reaearch work includes the following aspects:1.Dispersibility study of agricultural materials on multi-dimensional vibrating screen surface movement.Taken wheat as research objects,the dispersive effect of nine kinds of multi-dimensional vibration forms such as XYZ and Y?? was simulated and analyzed by two kinds of dispersion evaluation indexes.The results were that Y??,XYZ and Z?? have the better dispersions in the X-direction(the length of the screen)and the Y-direction(the width of the screen),X??,XYZ and XZ? have the better dispersions in the Z direction(the normal of screen surface).2.Study on screening performance of three-dimensional parallel vibration screen.Based on the XYZ vibration form which has the better dispersions,a three-dimensional vibration screen with different initial phases was proposed and the main mechanism of the screen was analyzed.The screening performance of this screen was simulated and analyzed by EDEM software without airflow,and the simulation test was validated on multi-dimensional vibrating screening test bench.It is concluded that the sieving grain increased first and then decreased with the increase of the initial phase of X,while the change of the initial phase in X has a significant effect on impurity and impurity was the highest when the phase was 45°.When the initial phase of Z was 90 °,the sieving grain was the lowest and the change was not obvious at other phases.The impurity increased first and then decreased with the increase of the initial phase.The sieving grain was higher when initial phase of Y was 30 ° and 60 ° while the impurity was lower than other levels and the difference was more obvious when the phase was 60°.With the increase of the sieve angle,the sieving grain showed the first increase and then decrease while the impurity showed the first decrease and then increase.The results of the bench test have the good agreement with the simulation results.3.Study on 3-DOF air-and-screen cleaning.Based on the three-dimensional parallel vibration screening,the 3-DOF air-and-screen cleaning model was established.The movement particles moving on the screen of 3-DOF air-and-screen cleaning device were simulated by CFD-DEM coupling technique.It was concluded that the velocity of wheat and short stalks in X increased with the increase of air speed and short stalks had been affected more by air,and the X-direction velocity of the grains decreased gradually along the X-direction,while the effect of airflow on the velocity of grain and short stalk in Y and Z direction was not obvious.In addition,the increase in wind speed will increase the material conveying speed which is conducive to the dispersion of materials,reduce the sorption rate but increase the sieve losses.The test results also have the good agreement with the simulation results.4.Experimental study on 3-DOF air-and-screen cleaning.The wind source equipment was designed on multi-dimensional vibrating screening test bench to establish the 3-DOF air-and-screen cleaning device and the average wind speed of the inlet was tested.The screening performance of the 3-DOF air-and-screen cleaning device was investigated by using the sieving speed and the heterogeneity.The wind speed,wind direction,amplitude and frequency of each branch were tested by orthogonal experiment.The results were analyzed to obtain mechanical working parameters' influence trend and degree on the screening by using variance analysis.The results showed that the amplitude of Y had the greatest impact on the sieving speed and the air speed had the greatest impact on the dirt percentage.The vibratory screen mechanical parameters were obtained by the integrated balance method when the screening performance was the best: the wind speed was 10m/s,wind direction was 26 °,X amplitude was 8mm,X frequency was 3Hz,Y amplitude was 2mm,Y frequency was 2Hz,Z amplitude was 6mm,Z frequency was 4Hz.Under optimal parameters,the screening speed was 132.18g/s,and the inclusion rate was 0.497%.