Design and structural optimization of the automatic flushing valve with exhaust function

Abstract: Dripline flushing has been widely expected to control the emitter clogging in drip irrigation systems. In this study, a new type of automatic flushing valve with the exhaust function (AE flushing valve) was developed to improve the duration and water volume of flushing. Four parameters were set, including the dentation length and dentation width of the delay channel, upper cavity volume, and water pressure before flushing valve. Eighteen AE flushing valves were designed by L18 (37) orthogonal test. Four flushing valves without an exhaust device (NE flushing valve) were set as the control treatment. A hydraulic performance test was performed on the 22 3D printed AE flushing valves to verify the effect of the exhaust device. The response characteristics of AE flushing valve performance to test parameters were also investigated. The results showed that the duration, water volume, and velocity of the AE flushing valve were 18.2-67.7 s, 3 904-12 367 mL, and 0.94-1.4 m/s, respectively when the water pressure at the flushing valve inlet was 0.06-0.14 MPa. The flushing duration and water volume were positively correlated with the dentation length, dentation width, and upper cavity volume, but negatively correlated with the water pressure. The flushing velocity was positively correlated with the water pressure only. According to the significance level of 0.05, the dentation length, dentation width and upper cavity volume posed significant effects on the flushing duration and water volume. The water pressure at the flushing valve inlet presented significant effects on the flushing duration and flushing velocity. The AE flushing valve automatically discharged the air in the upper cavity to improve the flushing duration and flushing water volume, which increased by more than 83.5% and 75.4%, respectively, compared with the NE flushing valve. Considering the anti-clog performance of the delay channel inside the flushing valve, and the minimum size of the flow section of the delay channel should be less than the sensitive clogging size of the emitter of 0.6-0.7mm, the dentation length, dentation width, upper cavity volume and water pressure with the longer flushing duration and larger flushing water volume were 1.2 mm, 2.2 mm, 19.1 mL and 0.06 MPa, respectively, while the corresponding flushing duration and flushing water volume were 67.7 s and 12 194 mL, which were 2.8 and 2.7 times larger than those of NE flushing valve, and 7.4 and 7.0 times larger than those of Israel imported ones. A regression model was established for the hydraulic, structural, and operation parameters of the AE flushing valve. In three AE flushing valves different from the above 18 structural parameters, the root mean square error of measured and predicted values for the flushing duration, flushing water volume, and flushing velocity were 2.1 s, 334 mL and 0.02 m/s, respectively, and the relative error ranges from -9.4% to 8.5%. It infers that the regression equation can be used to predict the structural and operation parameters of the flushing valve. This finding can provide the basis for the development of the automatic flushing valve with the function of exhaust during irrigation.