Effect of Offset Distance of the Central Axis of Diffusion Section on Fertilizer Absorption of Asymmetric Venturi Injector

Abstract

【Objective】 The asymmetric Venturi fertilizer injector is a device to simultaneously supply water and nutrients to crops through a drip irrigation system. Its performance is influenced by various factors. In this paper, we experimentally study the impact of the offset distance of the central axis in the diffusion section on fertilizer adsorption. 【Method】 Five asymmetric Venturi injectors with different diffusion sections were studied. Their fertilizer absorption was experimentally and numerically studied. The fertilizer absorption rate, critical pressure difference and the critical pressure at the inlet for fertilizer absorption were compared and analyzed between the five injectors. 【Result】 Under normal working conditions, the fertilizer absorption rate linearly increased with the inlet pressure. When the pressure difference between the inlet and outlet was 0.15 MPa, the fertilizer absorption rate maximized. The critical pressure difference and critical inlet pressure both increased with the increase in the outlet pressure. Compared with original asymmetric Venturi injector (F1), the asymmetric Venturi injector with eccentric downward diffusion section (F5) increased fertilizer absorption rate and efficiency by 13.03%~40.16% and 12.09%~39.13%, respectively. The increase, however, gradually decreased with the increase in the inlet pressure. Compared with F1, F5 increased the maximum fertilizer absorption rate by up to 13.03% and reduced the critical pressure difference by 7.69%. 【Conclusion】 When working at normal conditions, reducing the outlet pressure was beneficial to reducing the critical pressure at the inlet for fertilizer absorption. Moving the diffusion section away from the side of the fertilizer suction pipe can reduce local water head loss, make pressure at the throat more negative, thereby increasing the flow rate of fertilizer into the injector and reducing the critical pressure difference for fertilizer absorption. Our findings can help improve the design of the Venturi fertilizer injector for drip irrigation-fertigation systems.

Keywords

• venturi injector
• diffusion structure
• fertilizer absorption performance
• fertilizer absorption flow