Influence of draft tube water injection system on cavitation behaviour in a full-scale Francis turbine with visual access

Vilberg, Ingrid Kristine; Kjeldsen, Morten; Escaler, Xavier; Ekanger, Jarle V.; Nielsen, Torbjørn Kristian

doi:10.1088/1755-1315/240/2/022015

Cited by 2 publications

(2 citation statements)

References 3 publications

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“…These techniques include flow injection inside the draft tub as well as alterations of the draft tube geometry. Water and air injection have been investigated at the tip of the runner crown and the walls of the draft tube [8][9][10][11][12][13]. Bosioc et al [6] studied water injection from the runner crown into the vortex region.…”

Section: Introductionmentioning

confidence: 99%

An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine

Shiraghaee

Sundström

Raisee

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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The present work examines the effects of the radial protrusion of four cylindrical rods at different lengths within the flow field of a down-scaled turbine draft tube under part-load operating conditions. Four rods were placed on the same plane 90 degrees apart. The protrusion length was varied from zero to approximately 90 % of the draft tube radius. Time-resolved pressure measurements were performed to quantify the effect of the rod protrusion, using two pressure sensors at the same vertical level 180 degrees apart. Such sensor configuration enabled the decomposition of the signals into rotating and plunging components of the rotating vortex rope (RVR). The results show that different levels of mitigation are achieved for the rotating and plunging components depending on the protrusion length. The effects on the plunging component differ from the ones on the rotating component. The RVR plunging pressure pulsations slightly increase with the initial rod protrusion and then significantly drop after a certain length. On the contrary, the rotating component of the pressure pulsation amplitudes immediately decreases with the onset of rod protrusion. However, an optimum length is obtained in both cases where the highest mitigation occurs before reaching the maximum protrusion. This observation falls in line with the previous investigations conducted for oscillatory rod protrusions, further approving the point that a closed-loop controller should accompany the mitigation technique to achieve optimum mitigation.

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Section: Introductionmentioning

confidence: 99%

An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine

Shiraghaee

Sundström

Raisee

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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show abstract

“…Hence, extensive investigations have been performed to inject water from the shaft to introduce momentum into this region [20][21][22][23][24][25]. Moreover, peripheral injection is another method aimed at reducing the swirl close to the draft tube wall [26]. Experimental investigation of cone water injection in a swirl generator showed significant rotating mode mitigation, pressure recovery improvement, and notable plunging mode aggravation for injection rates above 11.5% [21].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine

Shiraghaee,

Sundstrom,

Raisee

et al. 2024

Journal of Fluids Engineering

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The present paper investigates the rotating vortex rope (RVR) mitigation on an axial turbine model by the radial protrusion of four cylindrical rods into the draft tube. RVR mitigation is of particular interest due to the unfavorable pressure pulsations it induces in the hydraulic circuit that can affect turbine life and performance. The protrusion lengths, which were the same among the four rods, were varied according to a pre-defined sequence. The experiments were performed under four part-load regimes ranging from upper part load to deep part load. Time-resolved pressure measurements were conducted at two sections on the draft tube wall along with high-speed videography and efficiency measurement to investigate the effect of the mitigation technique on the RVR characteristics and turbine performance. The recorded pressure data were decomposed and studied through spectral analyses, phase-averaging, and statistical analyses of the RVR frequency and peak-to-peak pressure amplitude distributions. The results showed different levels of pressure amplitude mitigation ranging from approximately 10% to 85% depending on the operating condition, protrusion length, and the method of analysis. The hydraulic efficiency of the turbine decreased by a maximum of 3.5% that of the best efficiency point (BEP) with the implementation of the mitigation technique. The variations in the obtained mitigation levels and efficiencies depending on protrusion length and operating condition indicate the need for the implementation of a feedback-loop controller. Thus, the protrusion length can be actively optimizes based on the desired mitigation target.

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Influence of draft tube water injection system on cavitation behaviour in a full-scale Francis turbine with visual access

Cited by 2 publications

References 3 publications

An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine

An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine

Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine

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