Parameter optimization of pneumatic conveying air inlet device in apple picking pipeline

Abstract:【Objective】China is the largest apple producing country in the world. Pcking is the most time-consuming work in apple production and labor cost for apple harvesting would account for 40% of the whole operation spending. Unreasonable picking and conveying methods would cause apple damage, and the quality of picking operation also could directly affect the transportation, processing and sales of apples. The labor force engaged in orchard operations had gradually decreased as the acceleration of urbanization. In addition, the traditional manual picking has low working efficiency, high labor intensity and high cost. Therefore, mechanical picking is urgently needed for modern apple industry in China. Pneumatic conveying device for convey apples after picking is necessary for mechanical picking. Ventilation in the conveying pipeline could reduce the bumping damage of apples and realize continuous picking and low-loss conveying of apples. The air inlet device could have great influence on the distribution of wind field and the change of wind pressure in the pipeline, so it is of great significance to study the air inlet device.【Methods】In this experiment, high-quality Fuji fresh fruits were used as raw materials, and a self-built pneumatic conveying device test-bed for apples was tested. The number of air inlets, the distance between pipe outlet and air inlet, the inclination angle of the air inlet and the inner diameter of the air inlet were taken as test factors, and the pressure difference between fan and pipe inlet and apple damage volume were taken as evaluation indexes. In the single factor test, we analyzed the influence of the number of the air inlets and the distance between the outlet and the air inlet on the air pressure in the conveying pipeline by simulation method. We analyzed the influence law of the inclination angle of the air inlet and the inner diameter of the air inlet on the pressure difference and damage volume by the bench test method. Based on the results of a single factor experiment, the orthogonal experiment of four factors and three levels were carried out. The range analysis method was used to determine the primary and secondary relationship of each factor, the variance analysis method was used to judge the significance of each factor, and then the SPSS software was used to analyze the interaction of each factor, so as to obtain the optimized structural parameter combination of the air intake device, and carry out the verification test.【Results】The single factor experiment showed that the maximum pressure decreased when the number of the air intakes increased. And as the pipe length increased, the wind pressure in the pipe increased first and then decreased. The orthogonal test results showed that the primary and secondary order of the factors affecting the mechanical damage of apples transported by pipeline were the number of the air inlets ＞ the inner diameter of the air inlets ＞ the inclination angle of the air inlets ＞ the distance between the outlet of pipeline and the air inlets, and each factor had significant influence on the test indexes, and there was interaction between each factor. The optimized parameter combination should be that the number of air inlets was 1, the distance between the fan and pipe inlet was 50 mm, the inclination angle of the air inlet was 30, and the inner diameter of the air inlet was 44 mm. Through the verification test, the pressure difference and damage volume under the optimized combination would be 82.341 6 Pa and 85.670 2 mm³ , and the test results were better than the index values in the orthogonal test.【Conclusion】The parameter optimization method of the air inlet device of the apple pipeline pneumatic conveying proposed in this study is reliable, The optimization effect is obvious, and the test steps are controllable, which would provide a reference for the pipeline pneumatic device to convey apples with high efficiency and low consumption.