Step Regulation Mechanism And Method Of Sediment In Drip Irrigation System With The Yellow River Water

The emitter clogging problem has been an international problem of drip irrigation research.The problem is more prominent in drip irrigation system with the Yellow River,which has the high sand content and complex water quality.This paper aimed to solve the emitter clogging problem in drip irrigation system with the Yellow River.A sediment regulation mechanism by step,which was based on discharging sand by emitter,flushing sand by pipe/belt and intercepting sand by filter,was established to control the transporting and moving of fine sand particles in the drip irrigation system.The high-cost sand treatment status by depositing and filtering was completely changed through the process of"reverse design-forward construction".A new and autonomous emitter design theory and method was established and new series emitter products with high anti-clogging performance were developed.The main conclusions were as followings.(1)Determine the optimal simulation model of the internal flow in the emitter.The internal flow visualization of emitter was realized by means of the three-dimensional flow-free field-disagreement test method.The water movement specialty and particles transport characteristics within flow path were analyzed.By comparing the macroscopic hydrodynamic characteristics and the microfluidic motion characteristics,the optimal simulation model of the internal flow in the emitter was the RNG k-ε turbulence model.(2)Establish the hydraulic design method and control criterion for designing emitter.The selection method of flow path configuration with the aim of increasing the turbulence intensity and the design method of structural unit by multi-designed optimization were put forward.The flow path configuration of toothed flow path and the fractal flow path were relatively optimal.The optimal design of the toothed flow path structure unit had the tooth height of 1.3mm,tooth angle of 60° and tooth interval of 1.8mm.The control threshold of the toothed flow path structure parameters were 0.8-1.2mm in width,27.5mm-42.5mm in length,and less than 1.0mm in depth.The different flow products can be designed by adjusting the depth within the control threshold.(3)Put forward the anti-clogging design method of the emitter.The new optimization design method for emitter flow path of washing the wall with a vortex was established.The included angle area of flow path wall was optimized by suitable arc,aimed to control the formation of the complex primary membrane on the flow path wall of emitter.Compared with the optimization design method of main channel,the optimization design method in this paper could significantly improve the flow velocity near wall by 13.1-21.4%,under the premise of ensuring the hydraulic performance of the emitter,which could greatly improve the self-cleaning-and anti-clogging ability of the emitter.(4)Developed a new series of anti-clogging emitters and verify the performance.A new flow-oriented structure design method of cycle optimization for emitter flow path was established and new series emitter products with high anti-clogging performance were developed.Test and compare the clogging occurrence characteristics of new products and representative products at home and abroad.It was found that the emitter clogging occurrence had the characteristic of randomness,recoverability and persistence.The energy dissipation efficiency of the new product was improved remarkably and the anti-clogging performance was significantly better than that of Israel Netafim company products by 4.8-9.0%,which realized the synergy improvement of hydraulic performance and anti-clogging ability.While the emitter length and weight was reduced by about 40%.(5)Explore the suitability of different emitter types for flushing and the effect of flushing on the growth kinetics process of clogging materials.A large-scale anti-clogging performance test platform of emitter in original location was constructed based on the principle of stratified adjusting pressure and controlling pressure by flow diversion.It was found that the effect of flushing on the different indexes of system operation was the most significant when it was the middle of the whole system operating time.The characteristic components of the clogging material showed a "fast-slow-fast" growth trend with the cumulative operation of the drip irrigation system.Flushing did not change the overall variation of the clogging occurrence characteristics and could effectively reduce the clogging material formation within the emitter flow path.(6)Clarify the best filters combination and operation mode in drip irrigation system with the Yellow River water.An on-site comprehensive test platform of hydraulic performance and sediment treatment capacity for different types of filters was independently designed.The best filters combination and operation mode was a sand filter with filter particle size of 1.70-2.35mm,filtration flow rate of 0.018m/s and backwashing flow rate 0.022m/s.The filter type and the mesh number of screen filter or laminated filter should be chosen based on the actual project situation.