额定流量与毛管位置对纽扣式滴头堵塞的影响及机理分析

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

    • 摘要: 为探究引用高含沙水滴灌时额定流量与毛管位置对纽扣式滴头堵塞风险的影响及相应机理,该研究对3种不同额定流量(2、4、8 L/h)的纽扣式滴头按照不同的毛管安装位置(毛管进水口处的支管长度分别为w、2w、3w,毛管间距w=204 mm;依次为内侧、中间和外侧)进行浑水堵塞试验。试验结果表明:滴头额定流量与毛管位置会影响毛管与支管内的断面平均流速,从而对管中沉积泥沙的起动产生影响,影响滴头堵塞进程。额定流量为4 L/h的滴头,其平均相对流量和灌水均匀度系数下降速率最慢,即抗堵塞性能最优,且其有效灌水次数最多,平均使用寿命比2和8 L/h的滴头分别提高了11.84%和49.11%。滴头额定流量越小,毛管位置对滴头使用寿命影响越明显,其毛管内滞留泥沙质量越大、沉积的大颗粒泥沙占比越多,大颗粒泥沙相对小颗粒泥沙更容易被滞留在毛管中。滴头额定流量越大、在单根毛管上的安装位置越靠近前段,其排出的泥沙粒径越大。毛管中沉积泥沙的起动是导致大流量滴头更快堵塞的主要原因。试验为滴灌系统堵塞机理的研究提供了思路,为实际应用中滴头额定流量的选用与滴头堵塞的预防提供了参考。

       

      Abstract: 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.

       

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