Design of air-stream impulse threshing device based on the law of grain arrangement

Abstract. Maize is the main food in most parts of the world and the third most important cereal grain worldwide, after wheat and rice. The disadvantages in using the traditional method to thresh maize are grain loss, increase of unviable seeds and others. This paper therefore used a low damage threshing method which is based on the principles of pre-dispersion and post-threshing to study the working principles of a threshing device. These include beak-like units of a discrete roller and two row air impulse spray nozzle. Two varieties of maize with similar moisture content, Luodan 998 and Denghai 9, were used for the test. The results showed that there was equal distribution of forces between the maize grains, with the grains arranged according to cyclic rules in the ear. The discrete roller had excellent ability to insert into maize grains, and disperse grains with low damage. Maize variety had little effect on air-stream impulse threshing. However the threshing result was positively correlated with the pressure of the air-stream. Air-stream impulse provided a low damage threshing. The verification test with only air impulse test resulted in zero number of threshed grain. However, the air impulse in combination with the discrete roller had a significant effect on threshing maize ear with low damage rate. The study has provided a new idea on designing maize threshing system with low damage.