Simulation and Optimization of the Throttle Releaser in Aerated Irrigation Systems

Abstract

Aerated irrigation is an emerging and efficient irrigation technique, and the throttle-squeeze releaser (TS releaser) is a commonly used key component in aerated irrigation devices. However, it has issues such as large bubble size, uneven distribution, and low dissolved-oxygen content in the irrigation water. Given these problems, this study optimized the valve chamber and throat structure of the releaser based on the TS releaser, designing three different types of releasers with W-shaped valve chamber, arc-shaped valve chamber, and multi-throat W-shaped valve chamber. The simulation results, obtained using the Fluent module with grid division in ANSYS 2022, show that high-pressure regions are formed inside the releaser with V-shaped and arc-shaped valve chambers that are detrimental to the formation of microbubbles in high-pressure dissolved-air water, while the fluid pressure reduction and energy dissipation are more balanced inside the releasers with a W-shaped valve chamber. Compared to a single-throat design, the multi-throat design allows high-pressure fluid to enter the valve chamber more uniformly, which aids in maximizing the functionality and performance of the valve chamber. To determine the effects of throat size, outlet size, and valve chamber angle on the pressure field, turbulent flow field, velocity field, and air-phase distribution within the multi-throat W-shaped valve chamber releaser, simulation interaction experiments were conducted. The results showed that the optimized releaser performed best when the throat diameter was 1 mm, the outlet size was 2 mm, and the valve chamber angle was 80°. Finally, a comparative performance evaluation between the conventional TS diffuser and the optimized multi-throat W-valve chamber releaser reveals that the latter achieves a maximum dissolved-oxygen content of 6.36 mg/L in the treated irrigation water, representing an approximately 3.5% improvement over the 6.14 mg/L recorded by the traditional releaser. Furthermore, when considering the thresholds of irrigation flow rates above 950 L/h and dissolved-oxygen levels exceeding 5.9 mg/L, the multi-throat W-valve chamber diffuser exhibits a broader operational range characterized by high flow rates and dissolved-oxygen levels.