Study On Mixers For Plant Protection Machinery And Chemical In-line-mixing Performances

The mechanism of in-line-mixing inside the chemical mixers was first studied which is a critical component in the direct in-line injection systems to ensure that systems can apply pesticides uniformly to target areas. In light of that, the internal configurations and geometric dimensions were determined in the design of an in-line-mixing chemical mixer. Mixers with four different Venturi mixing chambers were then developed for tests: a C-type mixer with the injection point downstream of the constricted section, a B-type mixer with the injection point at the midpoint of the constricted section, a G-type mixer with an angled injection point downstream of the constricted section, and a D-type mixer with the injection point upstream of the constricted section.A computational fluid dynamics program (FLUENT) was used to assist the simulation of the internal flow field inside the in-line-mixing mixers. The computer simulations showed that among the four mixers the C-type mixer had the best performance in delivery of fluid to the mixing chamber, followed by the B-type and then G-type mixer while the D-type mixer had the worst performance. Test results agreed with predicted performances of the computer simulations.Machine vision technologies were used to analyze the chemical mixing process inside the mixing chamber and a special program was developed to acquire and process digital images of two-phase flow fields recorded by a camera. A water-based water-soluble liquid were used as simulated pesticides for the test. Experiments were conducted that fluorescent tracers were mixed with simulated pesticides enabling the camera to track the mixing process in the transparent chamber. The experimental result showed that except for the G-type mixer, all other three mixers had significantly constant injection flow rates and produced uniform mixtures for water-based simulated pesticide. However, the increase of water flow rate from the centrifugal pump reduced gradually the mixing performance.The in-line-mixing experiments for C-type mixer and different chemicals with oil-based water-soluble liquid and non-water-soluble liquid were conducted. For the oil-based water-soluble liquid (Prime oil) and non-water-soluble liquid (Silicon oil), the C-type mixer had the highest mixture uniformity index among the four mixers. Also, the C-type mixer had a high uniformity index for mixing the non-water-soluble liquid (Silicon oil) than the oil based water-soluble liquid (Prime oil).This research established relationships among mixture uniformity, amount of simulated pesticides injected, physical properties of simulated pesticides, configurations of in-line mixers, and sprayer operating conditions. It was demonstrated that mixture uniformity could be greatly improved by a proper mixer, injection point position, injection direction, and the ratio of water flow speed and the injection flow speed through the mixing chamber.