针孔管式小麦匀播机构气力损耗特性数值分析与试验

Numerical Analysis and Experiment on Pneumatic Loss Characteristic of Pinhole-tube Wheat Uniform Seeding Mechanism

针孔管式小麦匀播机构的气道结构复杂、排布密集、截面积多变、弯折狭长,对气流的流通造成阻碍。为优化机构参数、减少气力损耗、提高气力利用效率,本文通过对流体域内可导致气力损耗的区域(变截面狭长圆柱区域、输气管弯折区域、气室汇流区域及负压口气室连接区域)进行分析,明晰了各区域产生气力损耗的原理及类型,得出横向输气管直径、输气管夹角及负压口直径是影响气力损耗的关键参数。以上述参数为试验因素,以吸种孔平均气流速度、吸种孔最低气流速度及吸种孔速度标准差为试验指标,利用Fluent软件进行三因素三水平正交仿真试验,得到各参数对指标的影响程度,并确定气力损耗最小的参数组合为:横向输气管直径8 mm、输气管夹角105°、负压口直径36 mm。在此参数组合下,吸种孔平均气流速度为86.4 m/s,吸种孔最低气流速度为75.16 m/s,吸种孔速度标准差为7.35 m/s。样机试验结果略小于仿真结果,但趋势一致,验证了数值分析的可靠性。

Aiming to the problem of pneumatic loss caused by the complex structure,dense arrangement,variable cross-sectional area,bending,narrow and long characteristics of air passage on the pinhole-tube wheat wide-width precision uniform seeding mechanism.The fluid domain was divided into four regions according to the type of pneumatic transformation:variable-area long-narrow cylindrical zone,air pipeline curved zone,air chamber confluent zone and negative pressure port and air chamber connection zone.By analyzing the regions in the fluid domain that can lead to the pneumatic loss one by one,the principle and types of the pneumatic loss in each region were clarified.It was concluded that the diameter of the transverse air pipeline,the angle of the air pipeline and the diameter of the negative pressure port may have significant impact on the pneumatic loss.The above three parameters were taken as test factors,and the mean airflow velocity of seed hole,the minimum airflow velocity of seed hole and the standard deviation of seed hole velocity were taken as test indexes.The Fluent software was used to conduct the orthogonal simulation test of three factors and three levels.The influence degree of each parameter on the index was obtained by range analysis and variance analysis,and the best combination of parameters was determined as follows:the diameter of transverse air pipeline was 8 mm,the angle of air pipeline was 105°,and the diameter of negative pressure port was 36 mm.Under these parameters,the average air velocity of seed hole was 86.4 m/s,the minimum air velocity of seed hole was 75.16 m/s,and the standard deviation of seed hole velocity was 7.35 m/s.Under the optimal parameters mentioned above,pinhole-tube wheat wide-width precision uniform seeding mechanism was verified,and the test result was slightly smaller than simulation result,but the trend was consistent,which proved the reliability of the numerical analysis.