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.