Evaluation of a carrier control valve for a direct nozzle injection system

Abstract

Environmental friendly pesticide application technologies, utilising direct injection systems and simple patch spraying, have become more important in recent years. During site-specific application, sprays are turned off over areas to be excluded and on over areas to be treated. Thus, to obtain spatially accurate applications, the spray patterns from nozzles have to be rapidly established. An electro-pneumatic carrier valve, in combination with a direct nozzle injection system, has been tested to determine its suitability for site-specific application. Also, the effect of interrupting the flow of carrier fluid on the injection process has been assessed. A high-speed camera was used to study the valve response time and the development of the spray pattern. The increase in concentration of pesticide in the direct nozzle injection system was simulated by a NaCl solution, which was measured using a conductivity sensor. The reaction time of the electro-pneumatic valve was less than 32 ms operating at 400 kPa air pressure. The response time of the valve was less than 23 ms for a standard nozzle body and less than 31 ms for a direct injection nozzle body with integral mixing chamber. The influence of interrupting the flow of carrier fluid on concentration was insignificant compared to the effect of injection on continuous carrier flow. In the direct injection nozzle body, the development time for the spray pattern was less than the transport and mixing time. Therefore, the feasibility of carrier switching in the direct nozzle injection process was demonstrated.