Comparison and Evaluation of Spray Characteristics of Three Types of Variable-Rate Spray
1C. Zhao, 1J. Zhou, 2W. Deng
1. National Engineering Research Center for Information Technology In Agriculture, China
2. National Engineering Research Center for Information technology in Agriculture, China
For the present developing direction of "low-input sustainable agriculture", variable-rate technology is increasingly concerned in agricultural engineering field. The technology of variable-rate precision chemical application is the typical of variable-rate technology. In China, agro-chemical production technology has reached the international advanced level, but the chemical application technology is still relatively backward, which has caused serious problems such as excessive utilization of agro-chemical, environmental pollution, food security, and so on. The current situation showed that continued deep research on variable spray technology and its spray characteristics is necessary and significant. In this research, three variable-rate spray equipments, PWM-based (namely, based on Pulse Width Modulation (PWM) technology) intermittent variable spray, PWM-based continuous variable spray, and pressure-based variable spray, were set up and their spray characteristics were studied in terms of flow-rate regulating range, spray distribution pattern, spray angle, spray droplet size, spray droplet velocity, spray specific energy and spray kinetic energy median diameter. The spray characteristics of the three kinds of variable spray methods were compared. Besides, a set of evaluation methodology for studying variable spray characteristics was put forward to provide a reference method of systematic study on variable spray characteristics. The results show that the influence of PWM-based intermittent variable spray on spray characteristics is the slightest. The flow regulating range of PWM-based continuous variable spray is the widest, which can reach 7:1 for flat-fan nozzle. The flow regulating range of pressure-based variable spray is the narrowest, which is just about 2:1. And the influence of pressure-based variable spray on its characteristics is the most serious. For the variable spray on fixed-width linear row crops, PWM-based intermittent variable spray should be the first choice. Yet, when the transverse width needs to be considered in spatially variable application, PWM-based continuous variable spray can be an alternative method.
