Research on the Law of Head Loss of Jet Pumps in the Cavitation State

Abstract

Liquid flow is subject to head loss because of viscous force, surface tension, friction force, and so on. Part of the energy is irreversibly converted into heat, which then dissipates into the environment. Head loss intensifies in the turbulent state. At present, few studies explore the law of head loss caused by secondary flow, cavitation intensity, and turbulence intensity. In this study, the head losses in different sections of a jet pump were studied by controlling the cavitation number σ, the secondary flow rate Qs, and the inlet pressure pi. The experimental results were analyzed with the aid of computational fluid dynamics. The results show that an increase in Qs can weaken the variations of Qs and suction pressure ps in the transitional stage of cavitation. Besides, σ, Qs, and pi influence head loss to varying extents. Cavitation intensity and turbulence intensity are the main factors for head loss and jet temperature difference. In particular, the influence of Qs on head loss provides guidance both for reducing the energy loss of the quantitative adding device and jet aerator and for expanding the stable adding range of the jet. More importantly, the main factors of energy loss caused by jet cavitation were analyzed in detail, which can effectively facilitate the pipeline design to reduce the local and frictional head loss.