HighlightsAccording to the physical characteristics of the millet, the double-layer mesh vibrating screen was used as the cleaning screen to prolong the cleaning time of the millet in the cleaning room, prevent the blocking of the vibrating screen, and improve the cleaning performance of the millet cleaning device.As the air flow produced by centrifugal fan was continuously attenuated on the screen surface, the draft chaser cannot completely discharge the chaffs, stalks and other sundries outside the machine. The cross-flow fan designed at the tail of the vibrating screen worked well for increasing the air flow field, improving the cleaning performance.In order to reduce the unthreshed grain-codes in the threshed mixture, a re-threshing device was installed for the millet cleaning device that transported sundries at the end of the screen to the main threshing roller for re-threshing, which improved the cleaning rate and reduced the loss rate effectively.The mathematical model of four factors quadric regression between the rotating speed of centrifugal fan, cross-flow fan, frequency of vibrating screen, width of sundry outlet and the cleaning performance of the device was established, which was meaningful and had high fitting degree. The results of indoor test shown that the cleaning rate was 98.8% and the loss rate was 1.3%.The results of bench test and field test shown that when the size of the upper screen was 12×12 mm, the size of the lower screen was 6×6 mm, the diameter of the suction port of the cross-flow fan was 15 mm, the rotating speed of the centrifugal fan was 1406 r/min, the rotating speed of the cross-flow fan was 713 r/min, the frequency of the vibrating screen was 5.9 Hz, and the width of the sundry outlet was 178 mm, the cleaning rate of the millet cleaning device was 98.75%, and the loss rate was 1.34%.Abstract. The cleaning device is an important part of the millet combine harvester, which directly affects the performance of the whole machine. Aiming at the problems of low cleaning rate and high loss rate in the traditional air-and-screen cleaning device, a vibrating screen millet cleaning device with double-fan was designed. The structure and relevant parameters of the vibrating screen millet cleaning device with double-fan were analyzed and determined. The effects of the rotating speed of centrifugal fan, the rotating speed of cross-flow fan, the vibrating frequency of vibrating screen and the width of the sundry outlet on the millet cleaning rate and the loss rate were studied by single factor test and the orthogonal combination test of four element quadratic rotation. The regression equation between the rotating speed of centrifugal fan, the rotating speed of cross-flow fan, the vibrating frequency of vibrating screen and the width of the sundry outlet and the millet cleaning rate and the loss rate are constructed was used to optimize and obtain the operation parameters of the cleaning device. The indoor test results showed that when the centrifugal fan speed was 1406 r/min, the cross-flow fan speed was 726 r/min, the vibrating screen frequency was 5.9 Hz, and the width of the sundry outlet was 178 mm, the millet cleaning rate was 98.8%, and the loss rate was 1.3%. The result of field test showed that the cleaning rate and loss rate of the vibrating screen millet cleaning device with double-fan were 98.75% and 1.34%, respectively. Keywords: Double-fan, Double-layer mesh vibrating screen, Field test, Millet.
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