Rotating vortex rope formation and mitigation in draft tube of hydro turbines – A review from experimental perspective

Abstract

Hydropower is a clean and renewable source of energy which is widely used to generate electric power and stabilize the power grid. It can respond quickly to any change in demand with the flexibility to operate over a wide range of time scales. At steady-state part-load operation, a flow structure known as precessing vortex rope develops in the draft tube of singly regulated reaction turbines, which causes large pressure pulsations. The vortex rope develops pressure pulsations in the draft tube cone, structural vibrations, power swings, pulsative pressure recovery, which are the main concerns in the hydropower sector. Studies were carried out to understand the inception as well as mitigation of these detrimental effects due to the rotating vortex rope (RVR) development. The primary focus of the present study is to comprehensively review the experimental investigations carried out to study the formation of RVR, its effects on turbine performance, and the methodologies developed to mitigate its impact. © 2020