Effect of Air Injection Holes Intrusiveness on Internal flow Phenomena of a Draft Tube Inside a Francis Turbine Model

Shahzer, Mohammad Abu; Kim, Seung Jun; Cho, Yong; Kim, Jin‐Hyuk

doi:10.5293/kfma.2022.25.4.005

Cited by 3 publications

(2 citation statements)

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Section: Numerical Workmentioning

confidence: 99%

“…The authors claimed that reduction in pulsation was due to reduction in swirl strength at this injection level, but the mechanism of changes per se has not been explained. Later, Shahzeret et al [50] tested mounting air injection holes in anti-swirl fins, but their findings showed this option to be undesirable in terms of turbine efficiency and pressure pulsations. One of the more recent numerical studies in which the authors tried to explain the mechanism of vortex rope mitigation and pressure pulsation suppression can be found in the paper by Sun et al [51].…”

Section: Numerical Workmentioning

confidence: 99%

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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: Numerical Workmentioning

confidence: 99%

Section: Numerical Workmentioning

confidence: 99%

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

et al. 2023

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Peripheral air jet injection at part load operation of a low head Francis turbine

KUMAR,

GANDHI

2024

Sādhanā

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Effect of water jet area on mitigation of vortex rope in a Francis turbine

Kumar,

Gandhi

2023

Physics of Fluids

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The rotating vortex rope (RVR) is normally formed at part load operating conditions, which develops flow instability in the draft tube (DT) cone of a Francis turbine. The detrimental effects of RVR reduce the life and performance of the turbine. The present work mitigates RVR through axial water jet injection in the DT cone. This paper extends the author's previous work on water injection with a 50% reduction in the water jet area through two nozzles with a diameter of 12.7 mm. The effect of area reduction is analyzed by spectral analysis like power spectrum density and spatial harmonic decomposition of the pressure field measured at the wall of the cone. The effect of water jet injection on synchronous and asynchronous pressure pulsations is analyzed at both measurement planes of the cone. The improvement in pressure recovery in the cone and turbine efficiency due to water jet injection is also analyzed. The water is injected at 0.5%–2% of the turbine inlet flow at 22.10° guide vane opening.

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Effect of Air Injection Holes Intrusiveness on Internal flow Phenomena of a Draft Tube Inside a Francis Turbine Model

Cited by 3 publications

References 0 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

Peripheral air jet injection at part load operation of a low head Francis turbine

Effect of water jet area on mitigation of vortex rope in a Francis turbine

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