Abstract
In a hydraulic power plant, it is essential to provide a reliable, sustainable and flexible energy supply. In recent years, in order to cover the variations of the renewable electricity production, hydraulic power plants are demanded to operate with more extended operating range. Under these off-design conditions, a hydraulic turbine is subject to cavitating swirl flow at the runner outlet. It is well-known that the helically/symmetrically shaped cavitation develops at the runner outlet in part load/full load condition, and it gives severe damage to the hydraulic systems under certain conditions. Although there have been many studies about partial and full load conditions, contributions reporting the deep part load condition are limited, and the cavitation behaviour at this condition is not yet understood. This study aims to unveil the cavitation phenomena at deep part load condition by high speed visualizations focusing on the draft tube cone as well as the runner blade channel, and pressure fluctuations associated with the phenomena were also investigated.
Highlights
In a hydraulic power plant, it is known that cavitation has undesirable effects on the systems
The first report DERXWWKHSKHQRPHQDFDOOHG3SRZHUVZLQJREVHUYHGLQWKHK\GUDXOLFSRZHUSODQWZDVPDGHE\ Rheingans [1]. He reported that the amplitude of pressure fluctuations can be magnified in certain conditions, and it gives a violent effect to the systems
At full load operating condition of a Francis turbine, Jacob et al primarily performed the experimental survey on the pressure surge, and they investigated the pressure fluctuations induced by this instability in 1990s [3]
Summary
1. Introduction In a hydraulic power plant, it is known that cavitation has undesirable effects on the systems. The first report DERXWWKHSKHQRPHQDFDOOHG3SRZHUVZLQJREVHUYHGLQWKHK\GUDXOLFSRZHUSODQWZDVPDGHE\ Rheingans [1].
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