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Chemical flow control for injection-type agricultural sprayers
Abstract
An injection sprayer stores agricultural chemicals separately from the liquid carrier and injects the chemicals into the carrier flowing to the nozzles. Injection sprayers have the potential to decrease excess spray mixtures resulting from applications and improve operator safely by reducing handling of chemicals. Peristaltic pumps are used to meter liquid chemical formulations on some current injection sprayers. Accuracies of two peristaltic pumps metering solution, emulsion and suspension liquid herbicide formulations were determined. The maximum error in the volumetric metering rate was 41% for a three-roller pump and 111% for a two-roller pump. To avoid exceeding a 5% error criterion, the pumps need to be calibrated for the chemical and temperature used. An experimental thermal flowmeter was developed and tested along with turbine and piston flowmeters. Flow rates of a solution and an emulsion herbicide formulation were measured successfully. The piston flowmeter had the best linearity and the smallest time constant. To avoid exceeding a 5% error criterion, each flowmeter needs to be calibrated for the chemical and temperature used. Each flowmeter had difficulties measuring a suspension formulation. Theoretical chemical application rates were derived for injection sprayers that provide constant spray mixture flow rates through the nozzles and a spray mixture concentration proportional to ground speed. Computer simulations predicted chemical application accuracies for injection sprayers accelerating from rest to a constant speed. Various plumbing systems downstream from the injection point were simulated. Plumbing systems with reduced hose diameters performed better than conventional plumbing systems for sprayers used by private applicators. A feedback system to control the liquid chemical formulation flow rate for an injection sprayer was proposed. A pressurized tank generates the flow and a microprocessor-based system controls the position of a flow control valve, based on the flow rate indicated by a piston flowmeter. The chemical flow rate overshoot was 1.46 mL/min following a transition from an acceleration of 1.6 (km/h)/s to constant speed. The controlled flow rate lagged the ground speed input by 0.13 s during the acceleration period.
Subject Area
Agricultural engineering|Chemical engineering|Mechanical engineering
Recommended Citation
Way, Thomas Roger, "Chemical flow control for injection-type agricultural sprayers" (1990). ETD collection for University of Nebraska-Lincoln. AAI9121942.
https://digitalcommons.unl.edu/dissertations/AAI9121942