Hydraulic performance experiment of lateral pipe jet-pulse tee

Abstract: Previous studies show that pulse drip irrigation can work under low pressure, and has the characteristics of good anti-clogging performance and high irrigation uniformity. In this paper, the hydraulic performance experiment of the lateral pipe jet-pulse tee was studied. Furthermore, the design method of the lateral pipe jet-pulse tee was put forward, an experiment was carried out in the laboratory: 6 sets of different lengths of lateral pipe were installed at the 2 outlet ends of jet-pulse tee, the length of unilateral capillary laying was 30, 40, 50, 60, 70 and 80 m respectively, and the lateral pipe length linking with 2 outlet were same; in addition, the hydraulic characteristics of 6 groups of capillary tubes with different lengths were tested under 5 different inlet pressure conditions, which were 5, 6, 8, 10 and 12 m waterhead respectively in each group. Hydraulic characteristics were measured by a turbine flowmeter and a pressure gauge, including the inlet pressure, the inlet discharge, and the maximum and minimum of the outlet head. The head loss, the irrigation uniformity coefficient and deviation ratio of flow rate were calculated. And the irrigation uniformity coefficient was calculated using the Christiensen formula, the deviation rate of flow rate was the ratio of the difference between the maximum and the minimum flow of emitter and the average flow rate of the dripper. The results showed that continuous and strong pulsed water flow could be observed under 5-12 m inlet head in the lateral pipe, pulse frequency stabilized 203-278 Hz, head amplitude 2.27-4.73 m, irrigation uniformity coefficient 96.58%-98.33%, and deviation ratio of flow rate 12.50%-19.88%. The pulse frequency was much higher than the low frequency generator with a frequency of 100 Hz or less controlled by the electronic device. The nonlinear equation describing the pulsed hydraulic performance and head loss of jet-pulse tee was established, and the nonlinear equation of the pulse performance and the irrigation uniformity coefficient was established too. The fitting degrees of the equations were above 0.96. The calculated results were verified by experimental data, the relative error were less than 1.5%, indicating that the nonlinear equations could well reflect the variation of the hydraulic performance and the head loss and the irrigation uniformity coefficient. On the basis of this, the author put forward the steps of calculating the inlet pressure of jet-pulse tee. The uniform coefficients of irrigation, based on the head amplitude and pulse frequency, were 98.13% and 98%, respectively, the absolute error was only 0.13%. The inlet pressure of jet-pulse tee could be easily determined for crops with different water requirement, and the uniform coefficient of irrigation could be predicted. The results would promote the further development of drip irrigation system, and provided the calculation method and theoretical basis for the research of lateral pipe jet-pulse tee and drip irrigation pulse development platform. In the future research, it is also necessary to carry out field experiment of pulse drip irrigation system based on jet-pulse tee, observe the distribution of pressure, flow and pulse performance in pipeline, and put forward the hydraulic design method of pulse drip irrigation system and further evaluate irrigation uniformity and anti-clogging ability. In a word, this paper only studies the pulse capillary, the irrigation uniformity of pulse branch and pulse irrigation area will be studied deeply in the future, which not only extends the drip irrigation equipment, but also is an effective way to establish high-performance drip irrigation systems.