Abstract
The paper presents an experimental study of oscillatory response in the Francis turbine of hydraulic unit. The experiment was performed on large-scale hydrodynamic test-bench with impeller diameter of 0.3 m. The effect of air injection on the intensity of pressure pulsations was studied at the maximum pressure pulsations in the hydraulic unit. It was revealed that air delivery into the water-conveyance system of the turbine results in almost two-fold reduction of pressure pulsations.
Highlights
IntroductionWhen changing load of hydraulic unit, the latter repeatedly undergoes off-design modes of operation
Power control in the energy system is an important task of hydropower plant
The pressure head and the degree of opening of the guide vanes were varied in the experiment
Summary
When changing load of hydraulic unit, the latter repeatedly undergoes off-design modes of operation. In these modes, the flow remains essentially swirling after passing through the water turbine runner. The instability of swirling flow results in the appearance of intense low-frequency hydrodynamic pulsations, which threaten the safety and reliability of turbine design [1,2,3,4]. The main reason for the occurrence of low-frequency pressure pulsations is the precessing vortex core generated in the diffuser of the draft tube due to essential residual swirl of the flow. The effect of air delivery on the oscillatory response of the flow was experimentally investigated on the model hydrodynamic Francis turbine test-bench
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