Design and experiment of banana straw crushing and returning machine with anti-wrapping device supported by flailing blade

Abstract: Banana straw is usually broken into pieces to degrade naturally in the farmland. However, severe entanglement of knife roller easily causes the wear of blades, leading to a short service life and low crushing efficiency in the conventional banana straw-crushing and returning machine. A great challenge has also been posed on the effective coordination of fixed knives during operation, especially in the case of high toughness after the aging of banana straw. Therefore, this study aims to improve the smashing rate of banana straw up to the standard requirement, thereby avoiding the winding of banana straw in pulverizers. An anti-wrapping device with a fixed flailing knife was also designed to reduce the entanglement for the banana straw-crushing and returning machine. Specifically, the movable and fixed knife was effectively coordinated in the machine. Three-point support was also formed using the crushing fixed knife and the Y-shaped flailing knife in high-speed crushing operation for the banana straw. As such, the highly efficient straw-crushing was realized to avoid straw entanglement. Among them, the Y-shaped flailing knife was composed of two L-shaped blades combined with a Y-shaped flailing knife and a flail. A systematic investigation was made on the optimization of structural parameters for the key components of crushing, the arrangement and combination of fixed knives, as well as the force analysis of banana straw during crushing. Correspondingly, the main test factors were determined as the forward speed of the returning machine, the speed of the crushing knife roller, and the bending angle of the Y-shaped flailing knife. A three-level three-factor orthogonal field test was then carried out, where the evaluation indicators were set as the crushing qualification rate of banana straw, and the unevenness of throwing. An optimal parameter combination was achieved, where the forward speed was 1.85 m/s, the knife roller speed was 1 500 r/min, and the bending angle of the Y-shaped flailing knife was 140°. In this case, the crushing qualification rate of banana straw was 95.1%, and the unevenness of throwing was 14.6%, indicating suitable for the actual situation of banana straw crushing. A comparison test was also conducted to verify the performance of the improved pulverizer. It was found that the qualified rate of straw smashing increased by 1.7 percentage points in the fixed-blade anti-wrapping banana straw crushing and returning machine, where the anti-wrapping device performed better. Consequently, the anti-wrapped banana straw crushing and returning machine with a fixed flailing knife can be expected to realize the sliding cooperation of the flailing and fixed knife for a better crushing effect, thereby reducing the entanglement of crushing knife roller. As such, the higher squeezing force of the cutter on the straw greatly contributed to effectively improving the crushing performance under the optimal operation requirements in the southern banana areas. The finding can provide strong technical support to the straw crushing and returning to the field in the banana areas.