Design and Experiment of Segmented Vibrating Screen in Cleaning Device of Maize Grain Harvester

In view of the fact that the cleaning rate and loss rate of maize grain could not meet the requirements of national standards for maize grain harvester, a cleaning device with segmented vibrating screens whose holes were round was designed. The CFD-DEM coupled method was used to simulate the gas-solid two-phase motion in cleaning device with traditional reciprocating vibrating double screens. Based on the law of grain penetration along the longitudinal area of the upper screen and the length of the upper screen, the suitable length of the front screen was determined and the rear screen was designed. The maize mixture could be dispersed and layered by the combination air from the upper and lower of the front screen before they fell on the rear screen from the end of the front screen. The cleaning rate of the grains could be increased and the loss rate of the grains could be decreased. Under the condition that the cleaning performance of the front screen remained constant, the frequency, amplitude of the rear screen, the vertical and horizontal distances between the front and rear screens were taken as the experimental factors. The cleaning rate and loss rate of the maize grains were taken as the performance indexes. The quadratic orthogonal rotational-combinational simulation tests were designed. The regression mathematical models between factors and indexes were founded. The optimal parameter combination was obtained by using the multi-objective optimization algorithm of Design-Expert 8.0.6 software. The best combination of parameters were the frequency of rear screen of 4.44 Hz, the amplitude of rear screen of 15.65 mm, the vertical distance between the front and rear screens of 114 mm, horizontal distance between the front and rear screens of 18.53 mm. Under the condition of inlet air velocity of 12.8 m/s and the air direction angle of 25°, when the feed rate of maize mixture at the inlet of the cleaning device was 5 kg/s, the cleaning rate of maize grain was 98.34% and the loss rate of maize grain was 1.45%. Compared cleaning device with traditional reciprocating vibrating double screens, the cleaning rate of maize grain of the cleaning device with segmented vibrating screens was increased by 1.26 percentage points and the loss rate of maize grain was decreased by 0.81 percentage points, which could meet the requirements of technical specification for quality evaluation of screening in China. © 2020, Chinese Society of Agricultural Machinery. All right reserved.