DROPLET VELOCITY AND ENERGY CHARACTERISTICS OF PWM-BASED CONTINUOUSLY VARIABLE SPRAY
In precision chemical application, a variable spraying system continuously monitors the features of spray targets, optimizes spraying according to target features, and determines appropriate spray characteristics to achieve desirable spray deposition. Thus, the effectiveness and precision of chemical application processing can be improved. With a complicated and changing field situation, various variable spraying equipment with different spray characteristics are needed to implement precision spraying in order to be environmental-friendly and economical. This makes it necessary to develop or improve equipment in terms of spray volume control with different spray characteristics. A kind of Pulse Width Modulation based (PWM-based) continuously variable sprayer was developed by the authors. The equipment of PWM-based continuous variable spray control mainly consists of an electromagnetic proportional regulating valve (EPRV) and a PWM control circuit. Through driving the EPRV using a square electrical signal with 24 kHz frequency and adjustable duty cycle, the continuous variable spray flow was achieved based on PWM technology. The flow-rate regulating range for PWM-based continuously variable spray can reach 7:1.In this article, the equipment of PWM-based continuously variable spray is introduce, and its spray dynamic characteristics are investigated in terms of spray droplet velocity, specific energy (SE) and kinetic energy median diameter (KEMD) for flat-fan nozzles, hollow-cone nozzles, and solid cone nozzles. We used a Phase-Doppler Particle Dynamic Analyzer (PDA) manufactured by Dantec Dynamics Company to measure spray droplet size and velocity using spot measurement method. The advantages of this device are high precision, undisturbed measurement, and needing no temperature correction and pressure correction. Its measurement principle is to calculate velocity according to the frequency of Doppler signal and calculate droplet diameter according to the phase difference of Doppler signals received from different places. As a result, PDA can measure droplet velocity and diameter synchronously. The key findings are: (a) the spray droplet velocity and the specific energy both decrease with a decreasing flow-rate, and especially when duty cycle is less than 75％, the decrement of spray droplet velocity is significant; (b) KEMD decreases with a decreasing flow-rate, which is the same as the VMD trend, which indicates KEMD is related to spray droplet size.
Spray droplet velocity specific energy kinetic energy median diameter Pulse Width Modulation (PWM) continuously variable spray
Deng Wei Ding Weimin He Xiongkui
National Engineering Research Center for Information Technology in Agriculture,Beijing 100097,China College of Engineering,Nanjing Agricultural University,Nanjing 210031,China College of Science,China Agricultural University,Beijing 100193,China
国际会议
北京
英文
1-7
2009-10-14（万方平台首次上网日期，不代表论文的发表时间）