Abstract: In the operation of returning liquid fertilizer to the field, the uniformity of the flow rate of each pipeline outlet of the distributor is the key condition for quantitative application of fertilizer. However, although the imported horizontal distributor and vertical distributor can achieve high fertilizer delivery accuracy, they are costly and difficult to maintain. Although the existing rectangular distributor has low cost and simple structure, the uniformity of flow rate at the outlet of each fertilizer outlet pipe is poor, which affects the fertilizer application precision and controllability. In order to solve these problems, numerical simulation of fluid flow in the rectangular distributor was carried out based on FLUENT fluid simulation software, and the structure of the rectangular distributor was improved. The results show that when the position of the fertilizer inlet is located on one side of the rectangular distributor, the difference between the flow rate on the left side and the right side of the rectangular distributor reaches 10.27%, the difference between the mass flow rate of the maximum flow rate outlet and the minimum flow rate outlet is 0.26 kg/s, and the standard deviation of the mass flow rate of the outlets is 0.088 95, and the flow rate variability of the fertilizer outlet ports is large, which has a large negative impact on the uniform application of liquid fertilizer. By changing the layout of the fertilizer inlet pipeline, redesigning the distributor structure, and setting the fertilizer inlet port in the middle of the distributor, the uniformity of flow distribution can be effectively improved on the basis of not increasing the manufacturing difficulty and manufacturing cost. After the improvement of the rectangular distributor, the difference of mass flow rate between the outlet of the largest flow rate and the outlet of the lowest flow rate was reduced from 0.26 kg/s to 0.12 kg/s, the difference between the left and right flow rates was reduced from 10.27% to 0.18%, and the standard deviation of the mass flow rate of the outlets was reduced from 0.088 95 to 0.038 7. The improved rectangular distributor has achieved a great improvement of the homogeneity of the distribution of fluids.

Key words:  liquid fertilizer, computational fluid dynamics, rectangular distributor, uniform distribution, numerical simulation

摘要： 在液肥还田作业中，分配器各管路出口流量的均匀性是定量施肥的关键条件。虽然进口的卧式分配器和立式分配器能够实现较高的输肥精度，但成本高、维护难。现有的矩形分配器成本低、结构简单，但各出肥管出口流量均匀性差，影响施肥精度与可控性。为解决这些问题，基于FLUENT流体仿真软件开展矩形分配器的流体流动数值模拟，对矩形分配器结构进行改进。结果表明，入肥口位置位于矩形分配器一侧时，矩形分配器左侧和右侧流量差异达到10.27%，最大流量出口与最低流量出口质量流率的差值为0.26 kg/s，各出口质量流率的标准差为0.088 95，各出肥管口的流量差异性较大，这对液肥的均匀施用有较大的不利影响。通过改变入肥管路布局，重新设计分配器结构，将入肥口设置在分配器中部，在不增加制造难度和制造成本的基础上能够有效提升流量分配的均匀性。矩形分配器经过改进后，最大流量出口与最低流量出口质量流率的差值由0.26 kg/s降为0.12 kg/s，左侧和右侧流量差异由10.27%降至0.18%，各出口质量流率标准差由0.088 95降为0.038 7。改进后的矩形分配器在流体分配的均匀性方面取得较大改善。

关键词: 液肥, 计算流体力学, 矩形分配器, 均匀分配, 数值模拟