Affecting Factors About Anti-clogging Performance On Emitter With Labyrinth Channel

As an efficient water-saving irrigation technology, drip irrigation is an effective way to achieve the goal that can save irrigation water. However, the narrow channel and complex structure always make emitters easily to occur clogging, which led to the serious consequences, such as the decline in the quality of the irrigation and crop production and so on. In this paper, the hydraulic performance, anti-clogging performance and numerical simulation of inlaid column emitters with labyrinth channel were studied. Inlet pressure evenly selected within the range 0-0.2MPa. During the emitter anti-clogging performance test, two different irrigation ways were short-term continuous irrigation and long period intermittent irrigation, sediment particle size range 0.0308-0.045 mm, 0.045-0.075 mm, 0.075-0.098 mm and 0.098-0.125 mm, three kinds of inlet pressure are 0.075 MPa, 0.105 MPa and 0.15 MPa, muddy water concentration is 0.5g/L. Also, the anti-clogging property about the water with fertilizer was texted. Then, numerical simulation of φ 8 emitter channel was learned using the standard k-ε model with FLUENT. Then the following main conclusions were reached.(1)Through the hydraulic performance test about the two different inlaid column emitter with labyrinth channel, it showed that labyrinth channel can make well effective turbulence, irrigation uniformity coefficient is more than 90%, that will meet the requirement of daily irrigation quality.(2)According to sediment anti-clogging test, it showed that while muddy water with low concentration with particle size less than 0.105 mm, inlet pressure has minimal impact to emitter clogging than particle. Different inlet pressures correspond to different size sensitive that caused emitter clogging easily, At the pressure 0.150 Mpa and 0.105 MPa, size sensitive of φ 16 emitter is from 0.045 to 0.075 mm, at the pressure 0.075 MPa, size sensitive is from 0.0308 to 0.045 mm. The particle size of 0.075~0.098 mm should be removed under the actual irrigation when using φ 8 emitter. To some extent, turbulence by sediment can increase emitter flow. Emitter blockage occurs at the moment of irrigation system running. Blocking position occurred in the first half of channel, or the entire channel. The main type is physical deposition.(3)The test about the water with fertilizer showed that fertilizer which was not discharged with water was deposited in the pipe terminus, instantly accumulate a large number of poorly soluble substances, than lead to clog the emitter which is the terminus ofφ16 drip irrigation. However, φ 8 tube diameter is only half of φ 16 drip irrigation, poorly soluble substances have made emitter clogging before it arrived terminus of drip irrigation. That means, emitter clogging of φ 16 is from back to front, while emitter at the latter part of the drip irrigation clog first and gradually extend to the upstream and downstream. The plugs of phosphate and potash tests are gray powders and pink powder. During the phosphate test of φ 8 drip irrigation, Cu is only 50% after 8 times irrigation, with emitter effective rate is 75%. During the potash test of φ 8 drip irrigation, Cu is almost 0%, with emitter effective rate is 50%. It is seriously affecting the quality of irrigation. In the process of fertilization with water, anti-clogging performance and fertilizer uniformity of φ8 drip irrigation are weaker than φ16 drip irrigation. Clogging is always happened at the moment of drip irrigation running during fertilization with water. Physical blockage is the most reason. Clogging happened was always at the channel inlet.(4)The numerical simulation result of hydraulic performance showed that there is a big relative error between simulated and measured results during 0-0.04 MPa, after that, relative error decreased, CFD method can effectively simulate the flow- pressure curve. The pressure distribution characteristic is reduced gradient along the channel, most changes are at the bend of the channel maze unit, not the straight section of the channel. Velocity within the high-speed region is mainly greater than 1/3 of maximum velocity, velocity within the low-speed region is 0-0.8m/s. Phase flow simulation using FLUENT showed that, velocity of solid particle is less than the liquid velocity, The larger the particle is, the greater the speed gap is. The velocity of channel unit vortex is almost the same as the velocity of channel wall, 0m/s. With the particle diameter of 0.045 mm, velocity gradient is the maximum at the bend, and decreased with the increasing size. Velocity gradient densely distributed near the high-speed region, evacuated far away from the high-speed region, even velocity contours is self-closing at the low-speed region. In addition to the wall velocity, vortex velocity is lowest at the low-speed-region center. As can be seen by the concentration distribution of the particles along the channel, while the process of sediment with water flowing, they didn’t deposited in the bottom of channel surface with gravity. Particles are mostly deposited in the runner corner.