| Objective: Drip irrigation transmits the water flow to the soil near the root of crops slowly,uniformly,and with low flow through pipes and drippers,which has the characteristics of water saving and fertilizer saving,and improving crop yield and quality.Drip irrigation is one of the current efficient and watersaving irrigation methods.Its core equipment is the drip irrigation emitter located at the end of the drip irrigation system.In the face of China’s increasingly scarce water resources and the huge proportion of agricultural water in the whole society,it is necessary to develop advanced drip irrigation equipment to improve the technical content of China’s agricultural science and technology equipment.In addition,it is also conducive to further comprehensively promoting the implementation of efficient water-saving irrigation,which is of great significance to improving the efficiency of water resource utilization and agricultural production in China.In this study,a shunt-hedging flow channel and a drip irrigation emitter based on the flow channel is designed by combining various energy dissipation methods.The shunthedging drip irrigation emitter has a simple structure and excellent hydraulic and anti-clogging performance.However,its energy dissipation and anti-clogging mechanism have not been effectively explored,and there is scope for the shunt-hedging flow channel’s anti-clogging performance to improve further.Methods: This study analyzes the hydraulic and anti-clogging performance of shunt-hedging flow channels by combining physical tests and numerical simulation,and structural optimization is carried out.The inlet pressure range of the hydraulic performance test is set at 0.05-0.20 MPa,the flow values corresponding to 16 pressure nodes are obtained,the flow index of the shunt-hedging flow channel is fitted,and its local head loss coefficient is calculated.The anti-clogging test was carried out under the fixed inlet pressure of 0.10 MPa.Take local river sand to carry out short-cycle single particle size test and mixed particle size muddy water test,and the relative flow change of the drip emitter was obtained and the sand sensitive particle size range that was easy to cause the flow channel blockage was divided.The CFD numerical simulation technology is used to study the flow channel’s flow field distribution,velocity and pressure distribution,sand particle movement trajectory,sand particle and surrounding fluid velocity variation,sand particle’s followability,and the division of sensitive areas on the channel boundary.Finally,combined with the physical test and numerical simulation results,the shunt-hedging flow channel’s hydraulic characteristics,energy dissipation,and anti-clogging mechanism are analyzed.The structural optimization research based on the sand movement characteristics is carried out also.Results:(1)The hydraulic performance of the shunt-hedging drip irrigation emitter is excellent.The flow rate range is 4-8 L/h under the inlet pressure range of 0.05-0.20 MPa,and the flow index before and after optimization is 0.479 and 0.486,respectively.The average local head loss coefficient of each channel unit in the shunt-hedging flow channel is 4.04-4.29,1.7-2.1 times that of the traditional labyrinth and zigzag flow channel.(2)According to the muddy water test results,D1 and D2 are divided into sand particle size groups that are easy to block the flow channel.D3-D5 is divided into sand particle size groups that is easy to block the flow channel.And D6 is the sand particle size group that is difficult to block the channel.(3)The larger the sand particle diameter is,the worse the followability is,the more the transportation distance required to pass through the channel and the number of times to enter the vortex area,and the greater the velocity deviation with the surrounding fluid.(4)There are sensitive areas on the boundary of the flow channel.After the sand particles collide with the sensitive area,their movement direction will change suddenly,increasing the risk of entering the vortex area.After structural optimization for the sensitive area of the flow channel’s boundary,the anti-clogging performance of the flow channel is improved by30%-60% by losing 1.5% of its hydraulic performance.Conclusion: The energy dissipation modes of the shunt-hedging flow channel are varied,and its main energy dissipation mechanism is the shunt-hedging of the water flow.Before optimization,the large vortex at the corner of the flow channel easily aggregates sand particles,which is the primary location causing the blockage of the flow channel.The larger the sand particle size,the easier it is to enter the vortex area for aggregation.In addition to its physical properties,there are sensitive areas in the flow channel’s boundary that significantly affect the movement characteristics of the sand particles,which is also an important reason for the sand particles to enter the vortex area.The structural optimization scheme based on the sand movement characteristics can significantly improve the anti-clogging performance of the flow channel under the premise of less hydraulic performance loss,which is feasible. |
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