The objective of this study was to elaborate on the layer mixing characteristics of the reverse-rotational rotary tillers. This paper describes the layer mixing performances of different tillage blades and compares their soil mixing characteristics, using both the numerical simulation model and actual field tillage tests. This test compares two types of blades. The first is the standard blade called "Sukui-zume" in Japanese, which is installed on marketed reverse-rotational rotary tillers. The other is a newly designed short scoop surface blade. This blade has an advantage over the standard blade with respect to the tillage resistance. The difference between these blades is the length of the arc of the blade scoop surface. The field tillage test and the numerical simulation model were conducted with both these blades. In the field experiment, small plastic spheres were used as the medium of soil layer mixing. In the numerical simulation, the throwing trajectory and the order of tilled soil were calculated by the soil mixing model of the backward throwing of tilled soil based on particle kinetics. The results show the differences between the soil mixing characteristics of the two types of blades. Both types of blades produce uniform soil mixing in all soil layers. However, the sort scoop surface blade produces a turning between the middle and bottom soil layers. The numerical simulation model appears to offer valid results with respect to the actual tillage tests except in the translation of the bottom layer soil.
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