Numerical Experiment and Optimized Design of Pipeline Spraying On-Line Pesticide Mixing Apparatus Based on CFD Orthogonal Experiment

Pipeline spraying can be adopted for greatly improving spraying efficiency in hillside orchard spraying operations. However, residual phytosanitary product still remains in the pipeline after the completion of pipeline spraying operations. Currently, residual phytosanitary liquid is handled according to the following general method: pipeline flushing with fresh water. The method can easily lead to pesticide waste and environment pollution. On-line pesticide mixing technology can be adopted for reducing pesticide waste and environmental pollution. However, on-line pesticide mixing technology is not applied in pipeline spraying operations. Therefore, the mixing principle of jet-mixing apparatus is adopted as a reference in the paper for designing the basic structure of on-line pesticide mixing apparatus based on pipeline spraying. The structure is mainly composed of a constricted tube, suction chamber, Venturi, and diffusion tube. An analysis method based on the CFD orthogonal experiment is adopted for studying the influence of the changes of four key structure parameters on on-line pesticide mixing apparatus, pesticide dissolution performance, and pesticide mixing performance; the four parameters include constricted tube falloff angle, diffusion tube divergence angle, Venturi diameter, and Venturi length. Since there may be interaction among them, three experiment evaluation indexes of lifting height, turbulent kinetic energy, and pressure recovery distance are set for judgment. The change of three evaluation indexes with change of constricted tube falloff angle, diffusion tube divergence angle, Venturi diameter, and Venturi length, respectively, is revealed through single-index variance analysis; the three indexes include lifting height, turbulent kinetic energy, and pressure recovery distance. The primary and secondary sequences of respective influences of all structure parameters and their interaction on all evaluation indexes are obtained. Analysis results of all evaluation indexes are comprehensively considered in order to finally discover the comprehensive optimal pesticide mixing apparatus structure parameters, namely: constricted tube falloff angle is 22°, diffusion tube divergence angle is 9°, Venturi diameter is 2 mm, Venturi length is 6 mm, and pesticide mixing apparatus structure parameters are optimized. Theoretical reference is provided in the paper for on-line pesticide mixing apparatus prototype production on the basis of pipeline spraying.