An Experimental Investigation of the Air Injection Effect on the Vortex Structure and Pulsation Characteristics in the Francis Turbine

Platonov, D. V.; Минаков, А. В.; Dekterev, Dmitry; Maslennikova, Aleksandra V.

doi:10.5293/ijfms.2020.13.1.103

Cited by 5 publications

(2 citation statements)

References 23 publications

(28 reference statements)

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“…The findings reported by Platonov et al [38] demonstrated a significant effect of air injection on the intensity of pressure fluctuations obtained when operating a mediumscale hydrodynamic test bench with a Francis turbine. It was found that when air was injected at operating conditions close to the optimal regimes, a substantial increase in pressure pulsations was observed, while when air was injected under conditions with the maximum pulsations, it could significantly reduce the surge.…”

Section: Air Addition 21 Experimental Workmentioning

confidence: 89%

An Overview of Active Control Techniques for Vortex Rope Mitigation in Hydraulic Turbines

et al. 2023

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This review addresses the current state of research into active control and suppression of vortex rope in hydroturbines under off-design operating conditions. Only active control methods that can be “switched on” when required under off-design operating conditions are considered in this work. The review focuses on air addition into the flow, as well as various auxiliary fluid jets. It includes all the best practices for vortex rope suppression in numerical and experimental studies. It can be inferred from the review that a modern flow control system should be comprehensive, designed for a specific hydroturbine geometry, and obtain feedback from the flow. Injecting ~2% of air from the impeller fairing cone appears optimal for suppressing pressure pulsations without significant efficiency loss. The cost of air injection is rarely estimated, but the use of an automatic venting system can minimize overheads and potentially improve efficiencies at low gas contents. Fluid jets ranging from 3% to 12% of the main flow rate can efficiently suppress pressure pulsations, but their high energy requirements limit their use. Azimuthal perturbation of the flow appears promising as it does not require significant energy loss, but practical implementation remains challenging as one needs to accurately know the system dynamics and be capable of real-time manipulation of the flow.

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Section: Air Addition 21 Experimental Workmentioning

confidence: 89%

An Overview of Active Control Techniques for Vortex Rope Mitigation in Hydraulic Turbines

et al. 2023

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“…Several studies have focused on suppressing the flow instabilities associated with the vortex rope in the DT of a Francis turbine. Platonov et al [7] conducted an experimental study on the impact of air injection on the vortex flow pattern and the pressure pulsation under maximum load conditions. The air was injected into the spiral casing of a Francis turbine model, and pressure pulsations were reduced by almost 50% due to the injection.…”

Section: Introductionmentioning

confidence: 99%

Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

2021

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Under low flow-rate conditions, a Francis turbine exhibits precession of a vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration of the turbine performance as manifested by torque and power output fluctuations. In order to suppress the rope with precession and a swirl component in the tube, the use of anti-swirl fins was investigated in a previous study. However, vortex rope generation still occurred near the cone of the tube. In this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted with a scale-adaptive simulation shear stress transport turbulence model. This model was used to observe the effects of the injection in the draft tube on the unsteady internal flow and pressure phenomena considering both active and passive suppression methods. The air injection affected the generation and suppression of the vortex rope and swirl component depending on the flow rate of the air. In addition, an injection level of 0.5%Q led to a reduction in the maximum unsteady pressure characteristics.

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Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations

Khullar,

Kumar,

Singh

et al. 2024

Sādhanā

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An Experimental Investigation of the Air Injection Effect on the Vortex Structure and Pulsation Characteristics in the Francis Turbine

Cited by 5 publications

References 23 publications

An Overview of Active Control Techniques for Vortex Rope Mitigation in Hydraulic Turbines

An Overview of Active Control Techniques for Vortex Rope Mitigation in Hydraulic Turbines

Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations

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