Assessment of chemical concentration accuracy and mixture uniformity of premixing in-line injection system

Authors: ZHANG, ZHIHONG - Kunming University Of Science And Technology; Zhu, Heping; SALCEDO, RAMON - The Ohio State University; WEI, ZHIMING - Shandong Academy Of Agricultural Sciences

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2020
Publication Date: 10/21/2020
Citation: Zhang, Z., Zhu, H., Salcedo, R., Wei, Z. 2020. Assessment of chemical concentration accuracy and mixture uniformity of premixing in-line injection system. Computers and Electronics in Agriculture. 176. Article 105670. https://doi.org/10.1016/j.compag.2020.105670.
DOI: https://doi.org/10.1016/j.compag.2020.105670

Interpretive Summary: In constant- and variable-rate sprayer operations, pesticide concentrates are mixed with a carrier in a large tank before field applications. However, this tank mixture preparation process has caused problems such as inaccurate pesticide application rate, applicator exposure to concentrated pesticide, and excess spray mixture leftover disposal. To solve these problems, a premixing in-line injection system was developed. In this research, spray mixture concentration accuracy and mixture uniformity discharged from variable flow rate nozzles were investigated for the premixing in-line injection system attached to a variable rate orchard sprayer. Investigations included the effects of viscosities of simulated pesticides and duty cycle combinations of variable-rate nozzles on chemical concentration accuracy and spray mixture uniformity at different nozzle positions. Test results illustrated that the new inline injection system mixed pesticides with water adequately for variable-rate sprays and ensured proper chemical dilutions and concentrations from individual nozzles. The premixing inline injection system would be an additional advanced implement for variable-rate orchard sprayers to further reduce chemical waste and environmental pollution.

Technical Abstract: A premixing in-line injection system was developed and attached as a retrofit to a laser-guided variable-rate orchard sprayer. Chemical concentration accuracy and mixture uniformity of the premixing system was investigated with various viscosities of simulated pesticides and duty cycles of pulse-width-modulated (PWM) nozzles at different positions on the sprayer. The chemical concentration accuracy was accessed by calculating the relative error (RE) between measured concentration and nominal concentration, and mixture uniformity was evaluated by the coefficient of variation (CV). Test results showed that the measured concentration was consistent across different nozzle positions, and RE and CV were observed within desirable ranges (<5.0%) for all nozzle positions and nominal concentrations. The average measured concentration slightly decreased as the viscosity of simulated pesticide increased. This phenomenon was more obvious under higher nominal concentrations. In addition, effects of PWM duty cycle combinations on the chemical concentration accuracy and mixture uniformity varied with number of active nozzles. It was found that RE and CV were larger than the desirable level (>5.0%) but were lower than the acceptable level (<10.0%) under conditions that nozzles were partially activated. For other treatments which all nozzles were activated, RE and CV were under the desirable level (<5.0%) for all nominal concentrations and nozzle positions. Laboratory tests demonstrated that the premixing in-line injection system was able to adequately mix the simulated pesticides with water, and could provide accurate and consistent uniformity of spray mixtures for the variable-rate spray nozzles to discharge different viscosities of simulated pesticides at different duty cycle combinations.