Structure optimization and experiment of sugarcane chopper harvester extractor

Abstract: Machine-harvested sugarcane usually contains too many impurities, and subsequently the cane loss often occurs when the impurities were separated by the extractor. These problems make it difficult for the mechanized harvesting of sugarcane to be recognized by sugar mills and farmers, which seriously restricts the promotion of mechanized harvesting in China. In this study, taking the extractor of a segmented sugarcane harvester (model: 4GZQ-180) as the optimization object, a CFD method was used to explore the aerodynamic performance of a extractor, and thereby to propose the improvement scheme, finally to manufacture a prototype for the test. The impurity rate and cane loss rate were used as the main indexes to evaluate the performance of the extractor before and after optimization. The commercial CFD software Fluent was selected to analyze the airflow field nearby the whole extractor and the blade, in order to investigate the performance and defects of the prototype extractor. The SST k-ω model and the realizable k-ε model were utilized to calculate the turbulence near the blade and the turbulence in the extractor, respectively. The simulation results of flow field near the blade showed that the cusp of leading edge and trailing edge of blade can lead to the decrease of the lift, while, the increase of the drag. The simulation results of extractor flow field showed that: the discharge hood changed dramatically, and the airflow was blocked by the main shaft. These defects led to the serious separation of flow in the extractor. In the numerical simulation, the shape of blade was improved, and the maximum lift-to-drag ratio of the improved blade was significantly higher than that of the current blade. The cusp of discharge hood was eliminated after optimization, and the axis direction of main shaft was the same as the air flow direction. In order to further eliminate the flow separation, the cowl was installed outside the hydraulic motor, whereas, the cross-section shape of support frame was set to a streamline. The numerical simulation results showed that the air flow rate and efficiency of optimized extractor were greatly improved. The flow rate and power were selected as evaluation indexes to verify the accuracy of numerical simulation, indicating that the error between the calculated and measured value was about 10%. The experiments related to the impurity rate and cane loss rate were carried out to evaluate the performance of the extractor. The determination of impurity rate showed that the impurity rate of the optimized extractor was similar to the prototype extractor at a high speed (1 650 r/min), but it was significantly lower than that of the prototype extractor at medium (1 350 r/min) and low (1 050 r/min) speed. The determination of cane loss rate show that the cane loss rate of the optimized extractor was similar to that of the prototype extractor at low speed, but the cane loss rate was significantly reduced at medium and high speed.