电磁阀开关模式下文丘里施肥器吸肥特性研究

水肥一体化技术是提高化肥有效利用率的重要手段之一,而基于脉宽调制的电磁阀控制模式是调节吸肥量的主要技术手段,但关于电磁阀连续开关模式下的文丘里施肥特性缺乏详细的阐述。该文在5通道的管道式在线混合的水肥一体化试验平台上,采用霍尔流量传感器测试了单一通道在0.3、0.5、1、2 s的开阀时间内瞬时吸肥量变化、不同开关阀时间下单次开关的平均吸肥量变化、不同关阀时间下10次连续开关下的平均吸肥量变化,采用脉冲修正法计算吸肥流量。试验结果表明,在电磁阀连续开关模式下,基于脉冲修正法的测量精度比基于有效脉冲数法更高,在开阀持续时间为0.3～2 s时间内,其相对误差均低于4%。在最大蓄能和放能时间内,文丘里施肥器的吸肥量随开阀时间变长而减小,随关阀时间的变长而增大。单次开关下的施肥器吸肥特性试验结果显示,施肥器的最大蓄能时间(抽真空)为10 s,而最大放能时间(吸肥量稳定的时间)为1 s。该研究可为智能变量水肥一体机设计及应用提供技术支撑。

Suction characteristics of venturi injector in solenoid valve switch ON&OFF mode

Abstract: The integration of fertilizer and water technology is one of the important means to improve the effective utilization rate of chemical fertilizers. The solenoid valve control mode based on pulse width modulation is the main technical means to adjust the amount of suction flow. But at present, the researches of scholars at home and abroad mainly focus on these 3 aspects: Water-fertilizer coupling effect test, venturi structure optimization and performance analysis, water and fertilizer machine pipeline design. And the venturi suction characteristics in the solenoid valves switch on and off mode was little concerned. In this paper, on the 5-channel pipeline online mixed water and fertilizer integration test platform, the hall flow sensor was used to test the instantaneous flow of single channel in the valve opening time of 0.3, 0.5, 1 and 2 s. The average flow of single switch under different valve opening and closing time. The average flow under 10 consecutive switches was calculated by pulse correction method. All the pulses and the time elapsed for each pulse were collected and recorded, and the flow rate was calculated according to the pulse total number, effective pulse number and the pulse correction respectively. The actual flow was measured by the electronic scale and compare with the calculated values of the 3 methods respectively. The results showed the relative error of the flow rate calculated by the total pulse number method was much larger than the effective pulse method and the pulse correction method, but the relative error decreases with the increase of the valve opening time. Compared with the total pulse number method, the measurement accuracy of the effective pulse method was greatly improved. The accuracy of the pulse correction method was the highest, the relative error was less than 4% during the valve opening duration of 0.3-2 s, and the pulse correction method was more advantageous when the valve opening duration was shorter. The suction characteristics test results showed that in the continuous switch mode of the solenoid valve, the shorter the valve closing time, the smaller the total number of pulses and the average flow rate. The average flow rate of each valve decreased rapidly with the valve opening time increasing. when the valve opening time was longer than 5 s, the average flow rate of fertilizer absorption tended to be stable at 10 L/min. In the combined structure of venturi and fertilization pump, the greater the fertilization pressure, the smaller the suction flow, but no significant effect on the energy storage and discharge process of the venturi injector. During the maximum energy storage and discharge time, the amount of suction flow by the venturi injector decreased with the prolonging of the valve opening time, and increased with the prolonging of the valve closing time. The test results of the venturi injector under the single switch showed that the maximum energy storage time (vacuum) of the venturi injector was 10 s, and the maximum energy release time (the time when the suction flow was stable) was 1 s. This research can provide technical support for the design and application of intelligent variable water and fertilizer machine.