Design And Optimization Of New Fruit Tree Root Emitter

Underground irrigation can improve the irrigation water utilization efficiency of deep-rooted fruit trees,According to the advantages and disadvantages of existing underground irrigation technology and irrigator for fruit trees,this paper proposes a new root irrigator for fruit trees suitable for forestry in arid areas.In order to make the infiltration characteristics of fruit tree root irrigator closer to the characteristics of annular distribution of fruit tree root system and to make the outflow flow more stable in different pressure range,this paper adopts a combination of experimental research,numerical simulation and theoretical analysis to design the root irrigator,and conducts a detailed study on its infiltration characteristics,hydraulic performance,energy dissipation mechanism,flow prediction and flow channel parameter optimization,etc.The design criteria and optimal parameters of the root irrigator are obtained,the findings of the study provide a theoretical basis and data support for the application of root irrigators in engineering practice,The main research results are as follows:(1)The design flow rate of the pre-buried irrigation ring under sandy loam soil conditions is 15 L/h.It is feasible to simulate the infiltration process of subsurface ring multi-point source under sandy loam soil conditions using HYDRUS-3D software.The wetting front before the intersection can be expressed by the equation of the upper and lower semi-elliptic curves relative to the infiltration point,and there is a good power function relationship between the wetting front and the influencing factors in each direction after the intersection,and the shape of the wetting body after the stabilization of infiltration is a rotating body formed by the vertical wetting front plane around the central axis of the irrigation ring.The most significant influence on the horizontal and vertical wetting front irrigation ring parameters are irrigation ring radius,irrigation ring depth of burial,the number of orifices can be ignored.The size of the transport rate of the wetting front in each direction is ranked as follows: vertical downward > horizontal > vertical upward,and the transport distance of the wetting front in each direction increases with the increase of the initial water content.The design guidelines of the irrigation ring were established.It was suggested that the burial depth of the irrigation ring was slightly greater than 1/3 of the depth of the main water-absorbing root system of the fruit tree,and 1/2 of the horizontal distribution range of the main water-absorbing root system of the fruit tree could be taken as the radius of the irrigation ring,and 4-8 outlet orifices were set on the irrigation ring according to the demand.In practice,according to the distribution range of the root system of fruit trees and the method of determining the irrigation ring,the appropriate radius and burial depth of the irrigation ring are selected,and then the irrigation system of root irrigation of fruit trees is reasonably formulated according to the mathematical model relationship between the irrigation water volume,infiltration flow and infiltration wetting body.(2)The coefficient of variation of flow rate decreases and then increases with the increase of diversion angle,flow channel width and number of flow channel units,and the influence of straight section length,convergence section length and bend radius on the coefficient of variation of flow rate can be ignored.The energy loss coefficient decreases,increases and then decreases with the increase of manifold angle,manifold width and number of manifold units,and the influence of straight section length,convergence section length and bend radius on energy loss coefficient can be ignored.There is a significant interaction between the main flow channel parameters(divergence angle,flow channel width and number of flow channel units)on the flow variation coefficient,and there is a significant quadratic function relationship between the main flow channel parameters and the flow variation coefficient in the low pressure area and high pressure area,and there is a significant interaction between the main flow channel parameters on the energy loss coefficient,and there is a significant quadratic function relationship between them.(3)SST k-ω is more suitable for simulating and calculating the flow in the helical hedge flow channel.The sudden increase in flow rate after the start of the supply pressure causes the water flow to produce a transient impact on the flow channel,which decreases rapidly and then gradually stabilizes,with the increase of the inlet pressure,the more obvious the pulsation phenomenon,and the smaller the average flow rate increase with the increase of the pressure.The beginning of the straight section of the flow stabilizer,the beginning of the convergence section,the end of the bend section is easy to form a low-speed vortex area.The wider the flow channel,the greater the energy loss,and the easier the low velocity flow area in the straight section is to siltation.The smaller the diversion angle,the easier to produce backflow in the unit flow channel,the larger the diversion angle,the greater the diversion flow in the bend section.The confluence section at the end of each stage unit has a large pressure drop,the energy loss coefficient decreases with the increase of the diversion angle,the energy loss increases with the increase of the inlet pressure,the head loss along the flow stabilizer only accounts for 0.06%-0.47% of the local head loss,the head loss along the head loss is negligible,the main form of energy loss is the local head loss,the flow channel mainly uses the water flow formed in the internal diversion,the Rapid turn,convergence,vortex and impact on the wall to make it turbulent,resulting in local head loss for energy dissipation,the flow channel by increasing the number of flow units in the high-pressure area bend section of the mainstream to reduce the sensitivity of the flow rate with the change in pressure,so as to achieve the function of stable flow.(4)Among the flow prediction models established by support vector machines,the linear model has the lowest accuracy and the nonlinear model has higher prediction accuracy,among which the power function has higher prediction accuracy than the quadratic polynomial and cubic polynomial,indicating that the flow channel geometric parameters,pressure and flow are more consistent with the power function relationship.The design criteria of the flow stabilizer are proposed according to the principle of minimum flow coefficient of variation,and the optimal design of the flow channel parameters of the flow stabilizer is thus obtained,and the optimal combinations of flow channel parameters are obtained for the low pressure zone(50k Pa-150 k Pa)and high pressure zone(150k Pa-250 k Pa)under different design flow rates(9L/h,12L/h,15L/h,18L/h,21L/h)The optimal flow path parameters can be selected according to the design flow rate corresponding to the water supply pressure and the soil for practical application.The prediction accuracy of the coefficient of variation of the optimized scheme is 95.37%-99.25%,and the coefficient of determination of the predicted flow rate value by support vector machine and the validated flow rate value is 0.927-0.994.The coefficient of variation of the flow rate of the optimized scheme in the high-pressure area is smaller than that in the low-pressure area,and the irrigation effect of the larger design flow rate in the high-pressure water supply condition is better if energy consumption is not considered.In practice,the design flow rate is first determined according to the soil texture,and then the appropriate flow path parameters are selected according to the water supply pressure.