Design and experiment of sliding-cutting and anti-twining returning device for banana straw

Abstract: The banana stalks are rich in fiber, and the existing returning machines for banana straw and stubble crushed in China have generated a few problems such as overly severe cutting resistance, the fiber of banana straw winding crushing blade roller on the returning machine, working on the unstable condition and serious fuel consumption. In order to deal with the above problems which the existing choppers met with in the working process, with the help of theoretical study and the analysis on the planting model for banana in Hainan Province, this paper put forward a returning method that the moving knives on the front knife roller were used to crush banana straws and the flail knives on the back knife roller were used to break stubble under the earth. The rotational direction of stubble crushing roller in the returning machine was same to the forward direction of the machine providing power, while the rotational direction of straw crushing roller was contrary to that of stubble crushing roller. On the basis of establishing theoretical model and the analysis on the planting model for banana in southern China, the key shaped parameters of the sliding-cutting blade and the structural parameters of crushing blade rollers were determined respectively. Besides, the sliding-cutting and anti-twining returning device for banana straw was put forward. The overall structure and working principle of sliding-cutting and anti-twining returning device were described. The performance of crushing banana straw and the power consumption were evaluated by simulating the breaking operation of banana straw in farmland through a bench test driven by double electric motors. The machine was composed of electrical motors, a tractor powered by electricity, the frame of machines, the straw crushing device and the stubble crushing device. Through Design-Expert software, a quadratic orthogonal rotating experiment was performed. Based on the variance analysis and regression fitting, a multiple regression equation was gained, presenting the effects of the working speed of the returning device, the rotating speed of rotating roller of moving knives and the rotating speed of rotating shaft of stubble breaking on the qualified rate of straw crushing and power consumption. It could be seen that the rotating speed of rotating roller of moving knives had the most influential effect, followed by the rotating speed of rotating shaft of stubble breaking, and the working speed of the returning device had the least influence on the qualified rate of straw chopping. The operation condition was optimized by applying the response surface method. The optimum factors for straw and stubble crushing process were as follows: The rotating speed of rotating roller of moving knives was 1 600 r/min, the rotating speed of rotating shaft of stubble breaking was 500 r/min, and the working speed of the returning device was 1.39 m/s. Based on the theoretical analysis, the higher qualified rate of straw crushing was achieved under the faster rotating speed of rotating roller of moving knives. The smaller power consummation was obtained under the lower rotating speed of rotating roller of moving knives and the lower rotating speed of rotating shaft of stubble breaking. Under the optimal condition, the corresponding qualified rate of straw crushing and power consumption were 95.2%, and 4.96 kW, respectively. The differences between the experimental and the analytical values of the qualified rate of straw chopping and power consumption were 0.31 percentage points and 0.27%, respectively, which indicated that the software analytical value was in great agreement with the experimental value. And by field test, qualified rate of straw crushing of machine proposed in this paper was higher by 1.94 percentage points and power consumption was lower by 11.3%, compared with vertical flail banana stalk crushing machine. Its successful implementation can greatly improve the production efficiency for crushing banana straw and stubble on one hand, and on the other hand prevent the pollution brought by deserted banana straw putridity.