Calculation Method Of Head Loss Of Three-way Pipe And Its Application In Fertilizer Applicator

In order to reasonably match the specifications of the fertilizer injection pump in the integrated water and fertilizer fertilizer applicator,the problems of poor fertilizer absorption effect and large energy consumption caused by improper matching of the fertilizer injection pump will be solved.By studying the hydraulic characteristics of the three-way pipe in the fertilizer applicator,this paper puts forward a calculation method of the head loss of the three-way pipe,and applies it to the matching of the fertilizer pump in the fertilizer applicator.The main research progress is as follows:Firstly,the hydraulic characteristics of the three-way pipe are studied by numerical simulation and experimental research methods;secondly,the calculation model of the local resistance coefficient of the three-way pipe and the calculation model of the pressure and flow change of the main irrigation pipe before and after fertilization are established;finally,based on the pressure and flow of the main irrigation pipe and the inlet flow of the Venturi fertilizer applicator when no fertilizer is injected.According to the amount of fertilizer absorbed,the injection pressure of the three-way pipe was deduced.The conclusions of this paper are as follows:（1）The Realizable k-εturbulence model is used to simulate the water injection of three-way pipe.By comparing the experimental data with the simulation data,the average relative error of the inlet pressure of the main pipe is 0.11%,the average relative error of the side pipe is 0.23%,and the average relative error of the outlet flow of the main pipe is0.002%.By comparison,the average relative error of the inlet pressure of the tee pipe is0.12%,that of the side pipe is 0.24%,and that of the outlet flow of the tee pipe is 0.004%.The model is accurate and can accurately simulate the water and fertilizer injection conditions of the tee pipe.（2）In order to distinguish the influence of fertilizer injection and water injection on the local resistance coefficient of the three-way pipeline,density and viscosity are used to represent the different working conditions of water and fertilizer,and the influence law of different water and Fertilizer on the local resistance coefficient of the three-way pipeline is clarified.With the increase of the density of water and fertilizer injected into the side pipe of the tee pipe,the local resistance coefficientξ₁ increases gradually and the local resistance coefficientξ₂ decreases gradually.The effect of water and fertilizer viscosity on local resistance coefficient is basically unchanged.In order to ensure the normal operation of the fertilizer injection pump,the local head loss is calculated by selecting the water injection condition.（3）The local resistance coefficientξ₁ between the main inlet and the main outlet of the tee pipe is mainly affected by the flow ratio between the side inlet and the main outlet of the tee pipe.With the increase of flow rate ratio,the local resistance coefficientξ₁ first increases and then decreases.The local resistance coefficientξ₂ between the side pipe inlet and the main pipe outlet of the tee pipe is affected by the flow rate ratio and the diameter ratio between the side pipe and the main pipe.The local resistance coefficientξ₂ increases with the increase of flow ratio and decreases with the increase of pipe diameter ratio.The calculation models of local resistance coefficients（R²=0.996,R²=0.999）are established.The model can accurately obtain the inlet pressure of side pipe fertilizer injection in three-way pipe,and achieve the goal of matching the fertilizer injection pump.（4）The flow and pressure of the original main irrigation pipe will be affected by water and fertilizer injected into the main irrigation pipe.In order to match the fertilizer pump conveniently.Therefore,this paper establishes a regression model of main irrigation pipe flow change,its correlation coefficient R² is 0.999,and a regression model of main irrigation pipe pressure change is established,its correlation coefficient R² is 0.994.The experimental results show that the model has high accuracy and can be applied to the calculation of matching of fertilizer injection pumps.（5）Based on the calculation model of local resistance coefficientξ₂ and the calculation model of flow rate and pressure change of main irrigation pipe,the matching application of fertilizer injection pump on bypass fertilizer applicator is carried out.Comparing the experimental and calculated values of the pressure of the fertilizer injection tube of bypass fertilizer applicator:when the bypass fertilizer applicator opens a single fertilization channel,the average relative error of the pressure of the fertilizer injection tube is 1.39%;when the bypass fertilizer applicator opens two fertilization channels at the same time,the average relative error of the pressure of the fertilizer injection tube is 1.79%;when the bypass fertilizer applicator opens three fertilization channels at the same time,the average relative error of the pressure of the fertilizer injection tube is 0.86%.It shows that this method can match the fertilizer injection pump accurately.