Numerical simulation and optimization design of a novel longitudinal-flow online fertilizer mixing device

Abstract

To enhance the mixing uniformity and real-time performance of orchard fertilizer blending and application systems based on prescription fertilization maps, a novel longitudinal-flow online Fertilizer Mixing Device (FMD) was designed based on the convective mixing mechanism. Using the Discrete Element Method (DEM), an numerical model of structural parameters for the FMD was established. Moreover, a Central Composite Design (CCD) simulation experiment was conducted, with blending blade speed (A), blade pitch (B), and blade width (C) as experimental factors. The Coefficients of Variation (CV) for the urea (N), diammonium phosphate (P), and potassium sulfate (K) mixing fertilizers were selected as response indicators. A quadratic polynomial regression model was fitted to describe the relationship between experimental factors and indicators. Through model optimization, a group of optimal operating parameters for the device were determined to be: A = 1200 rpm, B = 90 mm, and C = 17 mm. The research introduced the Lacey index to evaluate mixing performance. Experimental results revealed that the fertilizer in the device reached a highly uniform mixing state within a response time of 1 s. Bench-scale validation tests under optimal parameters showed that the FMD achieved performance indicators of CV_N = 8.54 %, CV_P = 9.04 %, and CV_K = 10.61 %. The error between the experimental results and the simulation model was less than 5 %, indicating high predictive accuracy of the model. The findings provide valuable references for the mechanical structure design and parameter optimization of orchard online fertilizer blending and application systems based on prescription maps.