Design and experiment of combine machine for deep furrowing, stubble chopping, returning and burying of chopped straw

Abstract: Returning and deep burying of crop straw into soil is an effective way to utilize and recycle the resource of straw, to decrease pollution and increase soil fertility. Deep furrowing is the key operation of the technology. The burying quality of present machine is decreased for there is no stubble breaking device and large soil blocks are lifted together with the undetached stubbles, and the operation cost increases for the shattering of stubbles and soil blocks after straw burying. A combine machine for deep furrowing, stubble chopping, returning and burying of chopped straw was developed in this study to solve above problems. The machine thus combined the functions of stubble cleaning and furrow opening. The machine consisted of a furrowing plow, a guide shovel and a stubble breaking unit. The furrowing plow was designed to cut at different depths into the soil. Critical components of the machine, such as furrowing plow of beak type, shovel guide and stubble breaking unit, were designed to withstand the tillage resistance. The 3D (three-dimensional) models of shovel guide and furrowing plow were set up and the structural strength analyses were carried out using Solidworks and ANSYS software respectively. A gear reduction transmission system was designed to control the rotational speed of the smasher shaft from the PTO (power take off). Field performance evaluation test was carried out in Jilin Province. An orthogonal experiment of 3 factors with 3 levels was conducted to investigate the effects of depths of guide shovel, rotary speed of stubble breaking blade and depth of stubble breaking on tillage resistance and rate of stubble cutting and soil breaking. The depth of guide shovel was selected as 100, 150 and 200 mm; the rotary speed was set at 260, 300 and 340 r/min and the depth of stubble smasher was at 60, 70 and 80 mm respectively. Analysis of variance (ANOVA) showed that the rotary speed of stubble breaking blade had significant effect on the rate of stubble cutting and soil breaking at probability level of 1%; the depths of guide shovel and stubble breaking had significant effects on the resistance force at 1% level of significance as well. So, it could be inferred from the statistical analysis result that the rotary speed of stubble breaking blade had no influence on the tillage resistance, while the depths of soil cut of both guide shovel and stubble breaking influenced the resistance, and consequently affected the tillage power requirement of the machine. The evaluated results further showed that the optimum tillage resistance and the rate of stubble cleaning and soil breaking were 21.6 kN and 96.3% respectively at a rotary speed of 340 r/min and depths of the guide shovel and stubble cleaning of 100 and 60 mm respectively. Results of the strength analysis showed that the structural strength of the machine was adequate for the service condition. It could be concluded that the developed combine machine is efficient in deep furrowing, shattering soil, breaking stubble and burying chopped corn straw with a good operation quality.