气送式播种机输种管长度影响管内气流分布的机理分析

Distribution Mechanism of Airflow in Seed Tube of Different Lengths in Pneumatic Seeder

为探索气送式排种系统输种管长度对排种性能的影响机理,在分析不同长度输种管管内气流平均流速变化规律的基础上,进行流体动力学(CFD)仿真,得到不同长度输种管管内气流速度流场分布图及排种量分布图。采用二次回归通用旋转组合设计试验,以播种量和风机频率为影响因素,以输种管管内气流平均流速、各行排量一致性变异系数、总排量稳定性变异系数为试验指标,进行了台架试验。试验结果表明:输种管长度增加,输种管管内气流平均流速降低,种子运动速度减慢,排种量减少,且当输种管长度小于2.50 m时,变化显著;当输种管长度在2.50~6.25 m时,气流平均流速降低速率减小,种子运动速度减慢变缓,排种量变化平缓,各行排量一致性变异系数为2.82%~3.88%,总排量稳定性变异系数为0.39%~1.28%,满足相关标准要求。因此设计时建议输种管长度选择在2.50~6.25 m之间。

A test stand about the pneumatic conveying system was conducted to explore the mechanism of the effect of seed tube length on the seeding performance of the pneumatic conveying system.On basis of analysis of law of average flow velocity in tubes with different lengths,computational fluid dynamics(CFD)simulation was conducted to get the map of speed flow field in tubes with different lengths.The quadratic regression general rotation combination design was used for the experiment,and the seed application rate and frequency of fans were taken as influential factors.Moreover,indexes of the test included variation coefficient of each row displacement consistency,variation coefficient of total displacement stability and the average velocity of airflow in the seed tube.A total of 24 seed transport tubes were used,with a gradient of 0.25 m and a length ranges from 0.50 m to 6.25 m.The analysis and test results showed that when seed tube length was increased,the gas average flow velocity was decreased,the seed movement speed was decreased,and the corresponding seed quantity discharge was decreased.Therefore,seed tube length had a significant influence on the seeding quantity.When seed tube length was 2.50~6.25 m,both the decrease of average flow velocity and the decline of the seed velocity were slowed down,and the seeding amount was changed smoothly.In addition,the variation coefficient of each row displacement consistency was 2.82%~3.88%,and the variation coefficient of total displacement stability was 0.39%~1.28%.Therefore,the seeding evenness was good and could meet the requirements of relevant standards.