Dynamic response evaluation of hydraulic performance based on sediment deposition sensitivity to flow rate of dripper emitter

Abstract: The performance of dripper irrigation emitter is of great concern in the emitter design and use. Generally, there are two important methods to estimate the performance of dripper emitters: their hydraulic performance and their anti-clogging performance. The hydraulic performance is always calculated in rinsing experiments; but in practice, although deposition and filtration techniques are adopted, fine sand particles can still penetrate into dripper emitters. This may change the forms and roughness of the flow channel. As a result, the hydraulic performance of dripper emitters in the field may greatly differ from initial rinsing tests. In addition, inlet pressures of dripper emitters may differ with different position in the field pipe network because of the influence of the topographical height difference and the head loss. So it is not particularly accurate to use the decrease in the rate of discharge under a fixed working pressure as usual to estimate the anti-clogging performance of dripper emitter. In order to overcome this discrepancy, we proposed a method to estimate the performance of dripper emitters that accounted for the influence of inlet pressure changes and sediment deposition on their hydraulic performance. We selected 3 bidirectional flow channels and 1 labyrinth channel for our study. Rinsing experiments were carried out at 50, 75, and 100 kPa to calculate the flow index of the dripper emitters. Periodic intermittent drip irrigation tests were also carried out to measure the changes of flow discharge using muddy water containing sediment particles with different sizes (all less than 0.125 mm); the sediment particles were formulated to 30 g/L of muddy water. The results showed that the flow indexes of selected dripper emitters in the muddy water experiment were bigger than the values in the rising experiment. This means that the hydraulic performance of the 4 types of dripper emitters got worse, which indicated, not surprisingly, that sediment deposits worsened the hydraulic performance. The increase in flow rates of No.0, No.1, No.2, and No.3 dripper emitters were 74.85%, 38.47%, 41.26%, 46.25%, respectively. After the muddy water experiment, the hydraulic performances of the bidirectional flow channels were still better than the contrastive labyrinth channel because the anti-clogging performance of bidirectional flow channels were better. The hydraulic performance of the 4 types of dripper emitters got worse and worse as muddy water irrigation frequency increased, which indicated that the larger the cumulative effect of sediment deposition could result in the greater influence on hydraulic performance. When the inlet pressure increased from 50 kPa to 100 kPa, the rates of discharge changes of No.0, No.1, No.2, and No.3 dripper emitters in the muddy water experiment were 40.43%, 17.23%, 19.43%, 22.33% higher than those in the rinsing experiment. The sensitivity of discharge to inlet pressure changes of the 4 types of drip emitters got bigger, which caused the hydraulic performance to drop. There were significant differences in hydraulic performance and anti-clogging performance among the bidirectional flow channels with different structural parameters; this indicated that structural parameters were the main factors affecting the overall performance of dripper emitters. Our method, using the dynamic response of hydraulic performance to sediment deposition in muddy water irrigation to evaluate the overall performance of dripper emitters, can improve dripper emitter development and provide a method guidance for measuring the overall performance of dripper emitters.