【作者】 张伟；

【导师】 吴春笃；

【作者基本信息】 江苏大学 ， 农业机械化工程， 2006， 硕士

【摘要】 该文首先介绍了精确农业及变量喷雾技术在国内外的进展，并特别介绍了脉宽调制型可变量喷雾技术，结合脉宽调制型可变量喷雾的特点，进一步分析了脉宽调制型可变量喷雾技术所存在的问题，根据这些问题作者首先使用电工电子学基础理论设计了一套斩波横流型功率放大电路，并使用EDA技术对该电路进行的仿真模拟，在此基础上设计完成了驱动电路，并将之应用于喷杆喷雾机实验上，采用称重法对其流量性能进行了验证。其次利用CFD软件Fluent对电磁阀内瞬态的流动性能进行了仿真。最后结合所设计装置及雾量分布实验台，对脉宽调制型可变量喷雾的雾量时空分布进行了计算机仿真及实验研究，提出了一套简化的脉宽调制型可变量喷雾的雾量时空分布的数值算法，并在此基础上对几种喷头的雾量时空分布展开了研究，此基础上寻找其雾量时空分布规律。并得出以下结论： 1) 使用本文所设计斩波恒流型功率放大电路可以将电磁阀的电流上升时间缩短至4.5ms，下降时间缩短至9ms。提高了电磁阀中电磁回路的响应速度。 2) 使用本文所设计斩波恒流型功率放大电路进行脉宽调制型可变量喷雾作业，当频率不高于5Hz时，流量和占空比之间的关系可近似看作Q=τ×Q_max；而在实验中频率为6.6Hz，占空比超过60％时流量达到峰值且不再随占空比的变化而变化。流量随着频率的增加而略有增加。 3) 当电磁阀开启的瞬间，电磁阀出口形成负压区，负压时间约为10ms，会使得在出口处产生气体的回流。 4) 电磁阀开启过程约存在2ms的开启延时时间，在该时间段内，还会伴随倒吸气体的排放，因此在这个时间段内的雾化质量受到损坏。 5) 电磁阀开启状态时，除电磁阀开启后和关闭前的瞬间存在压力和流量的激增外，电磁阀出口处压力（即喷头入口压力）等于电磁阀入口压力，此时流量达到峰值流量。 6) 电磁阀关闭存在着约2ms的关闭延时时间，因此与开启过程一样会产生雾化不完全的过渡过程。 7) 对于整个周期而言存在约4ms的过渡时间段，但在开启延时和关闭延时中流量的增加和衰减并不是线形的，而是在开启时或者关闭后的一个较短的瞬间陡峭，而在整个开启延时和关闭延时中都是较为接近峰值，并由于关闭延时的存在更多还原

【Abstract】 With the introduction of the precision agriculture and its development in the world, especially in modulation spray system, Author has made the analysis on the problem which the modulation spray system is still faced on. First of all, with the help of the basis knowledge of electronic, a special circus is designed in the job, which can be approved to be useful by simulating in EDA tools. With this drive, an experiment system of modulation spray has been made. A laboratory report by the method of weighting is given here in the paper. Secondly it is have done in this job to do some transient numerical simulation of high speed valve by using CFD software FLUENT, At last author has introduced a simulation manner to simulate the spray pattern of modulation spray system in temporal and spatial, with this mathematical model an analysis job is done in this paper which gives the law of spray pattern of modulation spray system. And the conclusion is here:1) With the circuits in this paper the response speed has been increasing that the rising edge can be cut down to 4.5ms, which is 9ms of trailing edge.2) Using the PWM spray with the circuits in this paper, the flow rate can be calculated by Q = τ×Q_max as the frequency is not higher then 5Hz, when the value is 6.6Hz andthe duty cycle is higher than 60%,it meet the dead zone.3) It is find a 10ms long suction pressure, which will result in air-sucking.4) A 2ms time lapse in open period of the valve have been found in the paper, in this two microsecond, the atomization quality is not so good5) When the valve is opening both the pressure and flow rate meet the maximal level, with two zones which increase sharply.6) A 2ms time lapse is also in the shut down time of the valve. It is also harmfulness for the atomization7) The open and shut down time lapse makes 4ms transition time of a cyclic. In this 4ms the flow rate is increasing with the piston position but not linearity which is increasing quickly to the near maximal value when piston is valve is just opening or closing. As the result of shut down time lapse the actual flow rate will higher then presumption.8) With the movement of piston in the valve the vortex is created, developed and transport to the spray, which will affect atomization.9) As result of the simulation, flat fan nozzle will be better then cone jet. The更多还原