Design And Experimental Research Of Chopping Device For Rice Straw

Abstract:Rice straw is a very important kind of agricultural resources which can be used as animal feed, paper making raw material, building material, biomass energy, organic fertilizer raw material and so on. The mechanization of rice straw chopping and returning to field has some flaws which have undesirable effects on the utilization of these resouces such as big power consumption, machines mixing with grass, heavy piled-up earth, unsatisfied operation effect. On the basis of collecting a large number of bibliographies, the current utilization situation worldwide of straw were systematically introduced,as well as the merits and demerits of various kinds of device analyzed, the development tendency of rice straw returning to field studied.Due to long stubble remained in farmland after harvesting as well as hardened and impervious soil in southern farmland of China, the tillage and land preparation parts of multifunctional rape-planting machine tend to wind grass and obstruct with mud, which impair the working performance of ridging equipment and reduce the percentage of rapeseed seedling germination. In order to solve these problems, a rapeseed planting method is proposed combining the straw mulching cultivation with the direct seeding. The method is used to collect and cut the rice stubbles, and then the chopped rice stubbles evenly cover the inter-row space without involving the tillage apparatus. A multifunctional rape-planting mechanism is mounted to a rice combine-harvester by replacing screening mechanism, using the original harvester header to collect the rice stubble and replacing the threshing cylinder with the mechanism to chop and scatter the rice stubbles. In this paper, a air-assisted chopping mechanism is designed, in which the moving knives and the transplanting blades were coaxially installed. Finite element statics analysis of frame was made to optimize. Structural parameters of frame dynamics modal analysis was made to avoid resonance in the process is well.The performance of the air-assisted chopping mechanism was evaluated by simulating the chopping operation of "stalk-standing" and "crop residue" in farmland by a bench test driving by an electric motor. A quadratic orthogonal rotating experiment is designed by Design-Expert software. Based on the variance analysis and regression fitting, a multiple regression equation was obtained showing the effects of rotate speed of feeding press rolls, rotate speed of rotation shaft of moving knives and gaps between moving knife and stationary knife on the qualified rate of the length of chopped stalk and power attenuation. It is shown that the rotate speed of rotation shaft of moving knives has the most influential effect followed by the gaps between moving knife and stationary knife, and the rotate speed of feeding press rolls has the least effect on qualified rate of the length of chopped stalk and power attenuation. The response surface method was applied to optimize the operation conditions. The qualified rate of the length of chopped stalk and the power attenuation, and the power attenuation were significantly influenced by the rotate speed of press roll for feeding, the rotate speed of rotation shaft of moving knife and the gap between moving knife and stationary knife. The optimum factors for "stalk-standing" and "crop residue" chopping operation are as follows:the rotate speed of feeding press rolls with 399.2 r/min and 401.64 r/min, the rotate speed of rotation shaft of moving knives with 968.12 r/min and 977.23 r/min, and the gaps between moving knife and stationary knife with 0.52 mm and 0.49 mm, respectively. Under the optimal condition, the corresponding qualified rate of the length of chopped stalk for "stalk-standing" and "crop residue" are 95.89% and 97.09%, as well as the power attenuation of 3.04 kW and 2.6 kW, respectively. The difference between the experimental value and software analysis value of the qualified rate of the length of chopped stalk for both "stalk-standing" and "crop residue" are 0.11% and that of power attenuation are 0.05 kW and 0.08 kW, respectively, which indicates that the experiment value are in great agreement with the software analysis value. Based on the theory analysis, the higher the corresponding qualified rate of the length of chopped stalk could be achieved under the faster rotate speed of rotation shaft of moving knives and the smaller gaps between moving knife and stationary knife. Taking into consideration the existing form of rice straw in farmland, the rotate speed of feeding press roll is designed to be 401.64 r/min, as the rotate speed of rotation shaft of moving knife with 977.23 r/min, and the gap between moving knife and stationary knife with 0.49 mm. It can provide technical support for the design of rapeseed planter with the combination of the straw-mulching cultivation with the direct-seeding.