The development and evaluation of aircraft chemical injection principles

Abstract

Research was conducted to develop and evaluate a chemical injection system for aerial spraying. A high pressure injection system was installed on the aircraft and performance was evaluated. Chemical formulation rate was controlled independent of spray rate by variation of formulation concentration within the spray mixture. Experiments were conducted to evaluate mixing uniformity and accuracy with respect to injection equipment and locations. Two different metering pumps (peristaltic and plunger) and three different injection locations (pump intake, boom supply line and nozzle body) were tested on a sprayer test stand. The time required to displace the liquid volume between the injection point and the nozzle with a new concentration, response time, was determined using a water soluble dye and colorimeter. For the different configurations tested, injection at the nozzle provided the fastest response to change in dye concentration. A chemical injection system was installed on a spray aircraft and tested for performance and accuracy. A dye concentrate was injected into the boom supply line just before to the y-strainer. Metering pump flow rate was based on aerial application parameters of speed, swath width and formulation rate. Injection accuracy and mixing uniformity were compared for the injection system and for conventional tank mixing and fell within the [plus or minus] 10% desired accuracy range. However, response time of the system did cause application errors on initial start-up and during on/off spray valve operation. During testing, no dye contaminated the spray tank hopper and the aircraft spray delivery system could be easily purged of dye mixture.