植保机在线混药系统的设计及混药性能试验

Design of online mixing system and performance test of mixed pesticides for the plant protection machine

为提高植保机喷雾作业中的农药利用率,设计了一种在线混药系统。混药系统主要包括取水单元、取药单元、混合器和控制单元。系统工作时,控制单元控制取水单元和取药单元抽取水溶液和农药,注入混合器混合,混合液经隔膜泵加压后经过喷头喷施。基于计算流体力学理论,建立内置7块扰流板且注药口和注水口沿边壁垂直分布并正对第1块扰流板的圆柱形静态混合器模型,运用Fluent软件对模型进行数值分析,结果常压(0.1MPa)时,混合器出口处药水混合均匀性变异系数为2.2%,药水混合效果最佳,但注药口有药剂回流现象,故提出药剂加压的模拟方案。药剂加压1MPa时,注药口无药剂回流现象,药水混合均匀性变异系数为2.0%,药水混合效果优于常压。用胭脂红溶液替代农药进行试验,加压状态下,混药系统喷头处混药稳定性最大相对误差为4.301%,药水混合变异系数最大,为3.989%,混药性能优于常压,与仿真结果基本吻合;对在线混药系统进行隔膜泵变工况试验,结果水流量在35~140 L/min时,药水配比为(1∶300)^(1∶3 000)时,在线混药系统混合均匀性系数最大,为4.670%。

An online mixing system was designed to improve the effective utilization of pesticides in spray operations. The pesticide mixing system mainly includes a water taking unit, a pesticide taking unit, a mixer and a control unit. When the system is working, the control unit controls the water extraction unit and the pesticide extraction unit to extract the required dose of the water and the pesticide into the mixer. The mixed liquid is pressurized by the diaphragm pump and sprayed by the nozzle. Based on the theory of computational fluid dynamics, a cylindrical static mixer model with 7 builtin spoilers was established for numerical simulation analysis. The pesticide injection ports and the water injection ports of static mixer vertically distributed along the side wall and the pesticide injection ports facing the first spoiler. The test results show that when the normal pressure of the pesticide is 0.1 MPa, the variation coefficient of the pesticide in the nozzle is 2.2%. At this time, the best mixing effect of the mixer is obtained, but there is a phenomenon of pesticide backflow in the injection port. Therefore, a simulation scheme is proposed for drug pressurization. Under the pressurized 1 MPa state, there is no reflux of the pesticide in the injection port, the variation coefficient of the pesticide mixture is 2.0%, and the mixer mixing effect is better than normal pressure. The carmine red solution was used to replace the pesticide, and the test was carried out by the ultraviolet spectrophotometry. The results showed that the maximum relative error of the mixed pesticide stability under pressure was 4.301%, and the variation coefficient of the pesticide was 3.989%.The mixing effect of the online mixing system under pressure is better than that under the normal pressure. The variation coefficient obtained by the test is basically consistent with the simulation results, and the online mixing system meets the design requirements. The diaphragm pump variable working condition test is carried out. When the ratio of the pesticide to water is varied from(1∶300) to(1∶3 000) with the water flow rate of 35-140 L/min, the mixing uniformity coefficient of the online mixing system is 4.670%.