Performance of a Chemical Injection Sprayer System

Abstract

The dynamic and steady state performance of a commercial chemical injection system was evaluated to determine if the system could be modified for variable-rate herbicide application. A helium-neon (He-Ne) laser system was used to quantify concentration uniformity across the spray pattern, along with the response characteristics of the system controller, the injection pump module, and the overall system. A range of operating conditions were created by changing system pressure and simulated sprayer travel speed. There was little variation in nozzle output distribution (CV < 10.5%) and chemical concentration (CV < 7.0%) across the spray path. The delay of the injection controller was slightly more than 1 s and injection pump delay was approximately 4 s. Controller and pump responses were rapid enough to qualify these components for use in a variable-rate application system. The long delay time (14 to 21 s) for chemical concentration response after a step change in travel speed was attributed to transport delays in the mixing chamber and spray boom. Accurate variable-rate application will require reduction of this delay and/or development of control algorithms to compensate for the delay.