Vortex-induced energy loss and pressure fluctuations in a closed sump under various conditions: An experimental investigation

Abstract

The roof-attached vortices (RAVs), floor-attached vortices (FAVs), and complex combined submerged vortices (CSVs) excited in a closed pump sump will induce irregular pressure fluctuations that can decrease the energy efficiency of the pump and the stability of its input flow. This article presents an experimental investigation of the energy loss and pressure fluctuations induced by these vortices under various conditions. A transparent closed-loop test rig was used for high-speed visualization and pressure-fluctuation tests. The findings demonstrate that as the flow rate is increased, the head and efficiency of the pump device significantly decrease. A CSV, which is composed of an RAV and an FAV, has the highest head-loss value, reaching 0.21 m, with an efficiency decrease in up to 2.8%. The typical evolution stages of RAV are divided into newborn, developing, fully developed, and dissipative collapsing. The typical evolution stages of FAV are divided into germinating, growing, maintaining, decaying, and disappearance. The maximum diameter of the FAV core is approximately 0.05 times the maximum vortex-core scale of the RAV. Based on the proposed vortex-identification method, as the bellmouth height decreases, the strength of the FAV increases during the CSV period, and the degree of pressure fluctuation becomes more severe. In addition, regardless of the flow rate, the strength of the FAV structure is always much greater than that of the RAV.