Effects of rated flow rate and lateral position on the clogging of button-type emitter and its mechanism analysis

This study aims to investigate the effect of rated flow rate and lateral distance on the risk of clogging in the button-type emitter during drip irrigation using high-sediment sediment-loaded water. Three rated flow rates (2, 4, and 8 L/h) of button-type emitters were subjected to the muddy water clogging tests, corresponding to the different lateral positions (lengths of branch pipe at the inlet of the lateral w, 2w, and 3w, respectively, with lateral spacing w=204 mm; referred to the inside, the middle, and the outside, in that order). A two-factor full-scale test was then carried out with a total of nine combinations. Three combinations were tested at one time, and three tests were conducted as one round, where a total of two rounds of tests were conducted to ensure the reliability. The results show that the rated flow rate of the emitter and the lateral distance posed the great impacts on the full cross-section mean flow rate in the lateral and the branch pipe, leading to the initiation of sediment deposition in the pipe, even in the process of emitter clogging. The emitter with the rated flow rate of 4 L/h presented the slowest decrease in the average relative flow rate and the coefficient of irrigation uniformity, indicating the best anti-clogging performance, and the highest number of effective irrigation times. The average service life increased by 11.84% and 49.11%, respectively, compared with the emitters with a rated flow rate of 2 and 8 L/h, respectively. The smaller the rated flow rate of the emitter was, the more significant the impact of the lateral distance on the service life of the emitter was. The lower the rated flow rate of the emitter was, the greater the mass of sediment retained in the lateral was, the greater the proportion of large-particle sediment deposited was, and the greater the tendency for the large-particle sediment to be retained in the lateral relative to small-particle sediment was. The emitter with the rated flow rates of 8, and 2 L/h shared the highest and lowest number of particles in the initiating motion of sediment deposited in the lateral, as well as the largest and smallest upper limit of particle size, respectively. The higher the rated flow rate of the emitter and the closer to the front of the installation on a single lateral were, the larger the sediment particle size it discharged. The initiation of sediment deposits in the lateral was the main cause of faster clogging of high-flow emitters. The amount of sediment entered the emitter, due to the too too-large rated flow rate of the emitter, the large velocity of water flow in the lateral, and the strong sand holding. The sediment particles then failed to discharge from the emitter in time to be easily deposited inside the emitter or flocculation and sedimentation by collision, leading to the emitter more susceptible to clogging. The clogging was easier to be washed away, due to the rated flow rate of the emitter for the 8 L/h of the flow channel cross-section dimensions (1.60 mm×1.08 mm) and the flow velocity of the muddy water within the channel is maximum. Repeated clogging was more likely to occur in the 8 L/h emitter than in the 4 and 2 L/h ones. The finding can provide a strong reference for the selection of a rated flow rate to prevent the emitter clogging in drip irrigation.