| Irrigation water is becoming more and more scarce in arid and semi-arid areas of China.Using the surface water source with high sediment content as the source of drip irrigation has become one of the effective ways to alleviate the shortage of irrigation water.However,the geometric structure of drip irrigator is complex and the flow channel is narrow(only 0.5～1.2mm).Many kinds of deposits in the water can easily lead to irrigator blockage,directly affect the irrigation uniformity of drip irrigation,and even make the whole drip irrigation system invalid.For this reason,this study takes the labyrinth channel irrigator as the main research object,flushing frequency,flushing velocity and water pressure model as the main research factors,through the combination of theoretical analysis,muddy water irrigation experiment and numerical simulation.the method of flushing drip irrigation system with clear water.The effects of different flushing frequencies(2 days,4 days,7 days,10 days and no irrigation),and different flushing rates(0.25,0.50,0.75m/s)on the anti-clogging performance of emitters were studied,and in muddy water irrigation without flushing.The control effect of different water pressure modes(constant water pressure,step waveform water pressure,trigonometric function waveform water pressure)and different working pressure(50,80,100,130KPa)on emitter blockage.In addition,the laser particle size analyzer was used to analyze the sediment gradation and particle size composition of the sediment discharged from the emitter and the sediment trapped in the labyrinth channel.This paper attempts to reveal the anti-blocking mechanism of the labyrinth channel emitter,and puts forward the filtration requirements of the first part of the system in the drip irrigation system of muddy water irrigation and suggestions for optimizing the structure of the labyrinth channel.Through the above research,the main conclusions of this paper are as follows:(1)The anti-clogging performance of the embedded tooth labyrinth irrigator in muddy water irrigation was significantly improved by flushing the capillary with clean water.Flushing can reduce the deposition of large particles of sediment in the pipeline,maintain the cleanliness of the inner wall of the capillary,reduce the probability of flocculation of small particles and adsorption on the entrance of the labyrinth and the inner wall of the channel,reduce the risk of blockage of emitters,and prolong the service life of emitters.12 kinds of flushing treatments increase the service life of emitters by 39.58% on average.(2)both flushing frequency and flushing flow rate have significant influence on the flow rate of emitter.In low speed flushing,frequent capillary flushing is needed to effectively control blockage,while in high speed flushing,the flushing frequency can be appropriately reduced,but it should not be lower than F1 max 7.When the capillary enters the flushing ineffective period for more than 7 days,the changes of flushing velocity and flushing frequency have little influence on the flushing effect,and flushing can not effectively prevent drip clogging.In muddy water irrigation,the changes of irrigation uniformity and relative flow are synergistic.In the whole irrigation period,there is an obvious linear correlation between them.(3)in muddy water irrigation without flushing,the anti-clogging performance of labyrinth emitters under pulsating water pressure treatment is better than that of constant water pressure,and dynamic pressure irrigation prolongs the service life of emitters by 58.29%.The waveform change of pulsating water pressure has little influence on the anti-clogging performance of emitters,and the difference in service life of emitters is only 5.96% under two different waveform pulsating water pressures.(4)under constant water pressure,most of the blockages of labyrinth emitters are inlet blockage,and the entrance blocking rate is as high as 64.15%.Under pulsating water pressure treatment,most of the blockages of labyrinth emitters are channel blockage and outlet blockage,accounting for more than 78.27% of the total blockage of the emitters.(5)the application of dynamic water pressure drip irrigation can appropriately reduce the filtration requirements of the first part of the drip irrigation system,and the sand particle size of irrigation water can be appropriately relaxed.Pulsating water pressure treatment is more conducive to the discharge of large-size sediment(particle size less than 60 μ m)from the emitter,and the maximum particle diameter of the emitter under dynamic pressure treatment is 44.34% higher than that under constant pressure.(6)in the drip irrigation system with high sediment content,the working pressure of low-pressure irrigation should be controlled above 80 KPa.When the working pressure is greater than 80 KPa,the process of emitter clogging and the accumulation of deposits in emitters are relatively slow.After 17.87-27.96 days of operation of the irrigation system,the emitters are suddenly clogged.When the working pressure is less than 80 KPa,the process of emitters clogging is accelerated,the accumulation of deposits in emitters is faster,and the emitters are clogged prematurely.(7)the sediment with particle size less than V25 has less sediment content in the emitter under four different working pressures,and the sediment of this size has better follow-up behavior and is not easy to cause irrigator blockage.The coarse sediment with particle size range of V75 and V90 is easy to cause emitter blockage,and the increase of working pressure has little effect on the deposition of this kind of sediment.The blockage of the sediment with a particle size range of V50 is between the two.The working pressure has a great influence on this kind of sediment,and the increase of working pressure is beneficial to reduce the retention of this kind of sediment. |
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