PWM间歇喷雾变量喷施系统中的压力损失和液压冲击
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摘要
在PWM间歇喷雾式变量喷施系统中,流量变化会引起喷杆各管路中的压力损失的变化,电磁阀的快速启闭会在管路中形成液压冲击,致使各喷头的实际喷雾压力发生波动,导致其喷施流量和雾化特性出现畸变。为揭示其管路压力损失的变化特性和液压冲击特性,构建了一套PWM间歇喷雾式变量喷施系统,并对其进行了流体动力学分析,确定了不同喷雾流量下的管路药液流态,建立了压力损失和液压冲击的计算模型,分析了0.3 MPa设定喷杆压力下的管路压力损失变化范围和液压冲击幅度,并进行了实际试验测试。结果表明:在0.3 MPa设定喷杆压力下,同一喷头前端管路的压力损失的变化幅度可达140 kPa,不同喷头间的实际喷雾压力差异可达25 kPa,由于电磁阀快速启闭而引起的液压冲击幅值可达170 k Pa。
In PWM-based intermittent spraying variable rate application system, duct pressure loss changes with the variation of flow rate, and hydraulic impact arises concomitantly with the close of solenoid valves, all these causes the fluctuation of spraying pressure which affected the actual spraying flow rate and spray characteristics of nozzles. In order to disclose the fluctuating mechanism of the spraying pressure, a PWM-based intermittent spraying variable rate application system was developed, and hydrodynamics analysis was carried out on it. Flow regime of the liquid in different flow rate was determined, computational models of the pressure loss and hydraulic impact were deduced, variation range of the pressure loss and amplitude of the hydraulic impact under 0.3 MPa boom set pressure were analyzed, and corresponding experiment testing were conducted. Test results showed that variation extent of the pressure loss for a nozzle was up to 140 kPa,differences of pressure loss between nozzles were up to 25 k Pa, and hydraulic impact was up to 170 kPa under 0.3 MPa boom set pressure.
In PWM-based intermittent spraying variable rate application system, duct pressure loss changes with the variation of flow rate, and hydraulic impact arises concomitantly with the close of solenoid valves, all these causes the fluctuation of spraying pressure which affected the actual spraying flow rate and spray characteristics of nozzles. In order to disclose the fluctuating mechanism of the spraying pressure, a PWM-based intermittent spraying variable rate application system was developed, and hydrodynamics analysis was carried out on it. Flow regime of the liquid in different flow rate was determined, computational models of the pressure loss and hydraulic impact were deduced, variation range of the pressure loss and amplitude of the hydraulic impact under 0.3 MPa boom set pressure were analyzed, and corresponding experiment testing were conducted. Test results showed that variation extent of the pressure loss for a nozzle was up to 140 kPa,differences of pressure loss between nozzles were up to 25 k Pa, and hydraulic impact was up to 170 kPa under 0.3 MPa boom set pressure.
引文
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[6]魏新华,蒋杉,孙宏伟,等. PWM间歇喷雾式变量喷施控制器设计与测试[J].农业机械学报,2012, 43(12):87-93.
[7]张波,吴春笃,张伟,等.脉宽调制型喷头电磁阀内流动数值模拟[J].农业机械学报, 2008, 39(12):78-81.
[8] Han Shufeng, Hendrickson L L, Ni Bingcheng, Zhang Qin. Modification and testing of a commercial sprayer with PWM solenoids for precision spraying[J]. Applied Engineering in Agriculture, 2001,17(5):591-594.
[9]邓巍,何雄奎,丁为民.基于压力变量喷雾的雾化特性及其比较[J].江苏大学学报(自然科学版),2009,30(6):545-548.
[10]魏新华,蒋杉,张进敏,等.脉宽调制间歇喷雾变量喷施系统的施药量控制[J].农业机械学报,2013,44(2):87-90.
[11]王俊,祁力钧.喷雾机喷杆压力损失及对喷雾质量的影响[J].农业机械学报2006,37(3):42-45.
[12]孔珑.流体力学(Ⅰ)[M].北京:高等教育出版社,2003.
[2] Paice M. E. R., Miller P. C. H., Day W.. Control requirements for spatially selective herbicide sprayers[J]. Computers and Electronics in Agriculture, 1996(14):163-177.
[3] Tumbo S D,Salyani M,Miller W M,et al.Evaluation of a variable rate controller for aldicarb application around buffer zones in citrus groves[J]. Computers and Electronics in Agriculture,2007,56(2):147-160.
[4]邓巍,丁为民,何雄奎.PWM间歇式变量喷雾的雾化特性[J].农业机械学报,2009,40(1):74-78.
[5] Bennur P J,Taylor R K. Evaluating the response time of a rate controller used with a sensor-based,variable rate application system[J]. Applied Engineering in Agriculture,2010,26(6):1069-1075.
[6]魏新华,蒋杉,孙宏伟,等. PWM间歇喷雾式变量喷施控制器设计与测试[J].农业机械学报,2012, 43(12):87-93.
[7]张波,吴春笃,张伟,等.脉宽调制型喷头电磁阀内流动数值模拟[J].农业机械学报, 2008, 39(12):78-81.
[8] Han Shufeng, Hendrickson L L, Ni Bingcheng, Zhang Qin. Modification and testing of a commercial sprayer with PWM solenoids for precision spraying[J]. Applied Engineering in Agriculture, 2001,17(5):591-594.
[9]邓巍,何雄奎,丁为民.基于压力变量喷雾的雾化特性及其比较[J].江苏大学学报(自然科学版),2009,30(6):545-548.
[10]魏新华,蒋杉,张进敏,等.脉宽调制间歇喷雾变量喷施系统的施药量控制[J].农业机械学报,2013,44(2):87-90.
[11]王俊,祁力钧.喷雾机喷杆压力损失及对喷雾质量的影响[J].农业机械学报2006,37(3):42-45.
[12]孔珑.流体力学(Ⅰ)[M].北京:高等教育出版社,2003.