滴头抗物理堵塞性能测试的水源标准化研究

    Standardizing the irrigation water sources for emitter anti-clogging test

    • 摘要: 滴头的抗物理堵塞性能测试是滴头设计研发和选型应用工作中的重要内容,但该测试程序中统一化、标准化的试验水源研究仍处于探索阶段。针对此问题,该研究将市售石英砂和天然黄河沙作为致堵物质分别开展滴头抗堵塞性能测试,探究采用石英砂配制标准水源的可行性。将两种颗粒筛分为≤0.063 mm、>0.063 ~ 0.075 mm、>0.075 ~ 0.090 mm三个粒径范围,分别设计粒径质量比1:1:1、4:1:1、1:1:4和浓度1.0、2.0、3.0 g/L组合配制试验水源,开展5种滴头的抗堵塞性能测试,采用堵塞偏差评价试验期间两种颗粒条件下滴头平均相对流量的差距,利用堵塞结果区分度评价试验结束时5种滴头堵塞程度之间的差异情况,并从石英砂和黄河沙的粒径组成、外观形貌特征对试验结果进行分析。结果表明:1)黄河沙颗粒圆度高,黏粒含量极低,而石英砂颗粒圆度低、棱角多,黏粒含量高。两者粒径组成和外观形貌上的差异导致相同条件下石英砂的堵塞结果比黄河沙严重,继而导致石英砂的堵塞结果区分度在颗粒浓度低/高时分别呈现出高于/低于黄河沙的结果。2)1.0 g/L或>0.075 ~ 0.090 mm颗粒含量多时,石英砂与黄河沙的堵塞偏差大,3.0 g/L或≤0.063 mm颗粒含量多时,两者堵塞偏差小。3)从单个滴头流量变化特征来看,所有处理下的滴头单次流量降幅均呈现两个集中分布区(100%和20%左右),且黄河沙和石英砂条件下都存在相似的堵塞后流量恢复和流量过载(超过额定流量)的现象,但石英砂的流量过载时的流量平均值和最大值比黄河沙更大(2.0 g/L+1:1:4处理除外)。4)从滴头平均流量的堵塞偏差、单个滴头流量变化特征、堵塞结果区分度3方面综合考虑,当浓度为2.0 g/L、≤0.063 mm、>0.063 ~ 0.075 mm、>0.075 ~ 0.090 mm三个粒径组质量比为1:1:1时,石英砂可以替代黄河沙作为滴头抗堵塞性能测试的标准水源。本研究可为滴头抗物理堵塞性能测试的标准化提供科学依据。

       

      Abstract: Anti-clogging test is one of the most important steps to design the emitter and type selection. However, it is still lacking on the standardized irrigation water in the testing procedures. In this study, a series of emitter clogging tests were carried out with the commercially available quartz sand and natural Yellow River sand as the clogging substances. A comparison was also made on the emitter clogging characteristics of the quartz and natural sand using standard test. Five kinds of emitters clogging performance tests were conducted to prepare the test water: three ranges of particle size (0.075–0.090 mm, 0.063–0.075 mm, and <0.063 mm) and three mixing ratios (1:1:1, 2:0.5:0.5, and 0.5:0.5:2) at three concentrations (1.0, 2.0, and 3.0 g/L). The distribution of particle size and morphologies of both materials were analyzed at the same time. The results indicate: 1) Yellow River sand particles exhibited the high roundness and low clay content, while the quartz sand particles were characterized by the low roundness, sharp edges, and high clay content. These differences in particle size distribution and morphology led to more severe clogging with the quartz sand, compared with the natural sand. The deviation of clogging (Dc) was used to evaluate the difference between the average relative flow rate of Yellow River sand and quartz sand during the experiment period. And the Dc value was higher at 1.0 g/L or the predominant 0.075–0.090 mm particle fraction. However, the Dc value was the minimum at 3.0 g/L or with a predominance of particles smaller than 0.063 mm. 2) Both quartz sand and Yellow River sand exhibited the similar trends in the decrease of individual emitter flow rates, due to clogging. The drop from normal flow rate to complete clogged (flow rate reduced to 0) was usually completed within 8h. There were also the similar flow rate recovery and flow overload (exceeding the emitter rated flow rate) of clogging emitter in both particles conditions. However, the average and maximum of emitter relative flow rate (the maximum relative flow rate of 150.36%) with quartz sand were much larger, when the overload occurred, compared with Yellow River sand. 3) The clogging differentiation (Dcr) was used to evaluate the differences between the clogging behavior of the five kinds of emitters, indicating the even distribution. The clogging of quartz sand was more serious than that of Yellow River sand under the same conditions. Quartz sand demonstrated the higher Dcr at lower particle concentrations, but the lower Dcr at higher concentrations, compared with the Yellow River sand. 4) A systematic analysis was made to consider the clogging deviation of average emitter flow rate, individual emitter flow rate variation, and differentiation of clogging among five kinds of emitters. It was concluded that the quartz sand can be expected to replace the Yellow River sand as clogging substances, in order to prepare the standardized water for the emitter clogging performance tests, when using 1:1:1 mass ratio mixture of the three particle size ranges (0.075–0.090 mm, 0.063–0.075 mm, and <0.063 mm) at a concentration of 2 g/L. This finding can provide the scientific evidence to standardize the emitter anti-physical clogging tests. A viable approach can be offered to select the quartz sand as the substitute for the natural Yellow River sand, in order to optimize the water source for the emitter test.

       

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