Research And Development Of Small Flow Emitters And Optimization Of Drip Irrigation Network

Drip irrigation technology has been applied in large areas around the world due to its advantages of saving water and energy,increasing production and working efficiency,and the applied area is still increasing year by year.Along with this situation,the types of emitters and the layouts of dripline network are constantly updated and optimized,which makes the drip irrigation technology more efficient.In recent years,as China’s land intensive management and large-scale management models have gradually become a trend,how to reduce the average investment in high-efficiency water-saving projects has become one of the bottleneck problems to be solved urgently.As one of the key components of the drip irrigation system,the laying distance of driplines under the condition of satisfying the irrigation uniformity becomes one of the key factors for the investment of irrigation system.For a certain scale of project,the large increase of the laying distance of the dripline means that the reduction of the amount of materials such as branch pipes and valves and the reduction of the construction cost,which wouldl help to reduce the project investment.Therefore,it is very urgent to develop emitters and dripline which are suitable for long dripline for meeting industry development and engineering application.In this paper,the internal water flow characteristics,anti-clogging performance and their differences of different typical tooth structure emitters are analyzed using Fluent software(CFD),and the idea of structural optimization design for emitters is put forward based on the analysis results,and based on the test and verification of the hydraulic performance of the developed emitters,two kinds of emitters with better hydraulic performance are provideded.At the end of the paper,the optimization of the long dripline network in the field is discussed.The main conclusions are as follows:(1)In the process of numerical simulation of labyrinth channel,the simulation accuracy of the tetrahedral with boundary layer mesh or the mixed polyhedral mesh was the highest.The simulated accuracy could be controlled within the range of 6.00%using the standard k-ε model,which could be recommended as the reference setup mode for the numerical simulation of the tooth labyrinth emitter.In the range of the experimental channel depth,the channel depth is positively correlated with the flow coefficient and flow index;the flow index decreases with the increase of the tooth height,and the flow coefficient increases first and then decreases with the increase of the tooth angle;based on the numerical simulation results of the orthogonal experimental scheme,the flow index and flow coefficient are respectively constructed with the key structural parameters of the tooth type emitter Multiple linear regression equation.(2)The anti-clogging performance of the dental labyrinth emitter is closely related to the fluid velocity in the low velocity zone in the flow channel and the turbulent kinetic energy in the flow passage.Areas with high flow rates and turbulent energy are less likely to be clogging.The maximum value of turbulent kinetic energy appears in the mainstream and reaches the maximum value at the water-facing area in the flow passage.The turbulent dissipation rate has similar distribution rules with turbulent kinetic energy,and the region with the most turbulent kinetic energy dissipation is located at the tip of the teeth.The research result showed that the dental structure plays a key role in the energy dissipation effect.And the range of turbulent kinetic energy was increased by 52%-200%compared with the other four dental structures,and the optimized dental structure increased the particle transport velocity,and reduced the transport distance and retention time of the particle,which improved the anti-clogging performance of dental labyrinth emitter.(3)Both the N-channel emitter and the trapezoidal channel emitter have good anti-clogging performance.Compared with the trapezoidal emitter,the N-channel emitter has better anti-clogging performance;The structure design of N-channel water inlet greatly reduces the possibility of sand entering the channel and the probability of clogging the emitter.For the two kinds of emitters,the rated flow rate is 0.861/h and 0.61/h respectively,and the flow state index is 0.45 and 0.48 respectively.The limit laying distance for N-channel emitter and trapezoid structure emitter is 180m and 155m respectively.The laying distance is more than twice that of the conventional driplines.(4)Long dripline used in drip irrigation system can reduce the investment of network.Considering the most unfavorable engineering conditions,for the rectangular irrigation network with a length width ratio of 1:2,comparison of three main laying methods,it can be seen that the network investment is the smallest under the"Gui"layout mode;and the investment of the water source distribution on the symmetrical axis in the center of the irrigation area is smaller than that of the corner point.The long dripline can reduce the pipe network investment per mu about 9-13.79%;for the existing drip irrigation system,due to the influence of engineering facilities and plot shape,the application of long dripline can reduce the pipe network investment by about 15.32%under the conditions of not changing the laying spacing.