scholarly journals Study of the vortex-induced pressure excitation source in a Francis turbine draft tube by particle image velocimetry

2015 ◽  
Vol 56 (12) ◽  
Author(s):  
A. Favrel ◽  
A. Müller ◽  
C. Landry ◽  
K. Yamamoto ◽  
F. Avellan
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Draft Tube ◽  
Excitation Source ◽  
Francis Turbine ◽  
Image Velocimetry ◽  
Pressure Excitation

scholarly journals Analysis of the Cavitating Draft Tube Vortex in a Francis Turbine Using Particle Image Velocimetry Measurements in Two-Phase Flow

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Monica Sanda Iliescu ◽  
Gabriel Dan Ciocan ◽  
François Avellan
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Francis Turbine ◽  
Ensemble Averaging ◽  
Two Phase ◽  
Physical Knowledge ◽  
Image Velocimetry ◽  
Constant Pitch ◽  
Turbine Runner ◽  
Complex Phenomena

Partial flow rate operation of hydroturbines with constant pitch blades causes complex unstable cavitating flow in the diffuser cone. A particle image velocimetry (PIV) system allows investigating the flow velocity field in the case of a developing cavitation vortex, the so-called vortex rope, at the outlet of a Francis turbine runner. The synchronization of the PIV flow survey with the rope precession allows applying the ensemble averaging by phase technique to extract both the periodic velocity components and the rope shape. The influence of the turbine setting level on the volume of the cavity rope and its centerline is investigated, providing a physical knowledge about the hydrodynamic complex phenomena involved in the development of the cavitation rope in Francis turbine operating regimes.

Numerical Investigation of Flow in a Runner of Low-Head Bulb Turbine and Correlation With Particle Image Velocimetry and Laser Doppler Velocimetry Measurements

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
David Štefan ◽  
Sébastien Houde ◽  
Claire Deschênes
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Laser Doppler Velocimetry ◽  
Particle Image ◽  
Draft Tube ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Image Velocimetry ◽  
Low Head ◽  
Bulb Turbine

It is a well-known fact and a much studied problematic that the performance of low-head hydraulic turbines is highly dependent on the runner–draft tube coupling. Around the optimal operating conditions, the efficiency of the turbine follows closely the performance of the draft tube that in turn depends on the velocity field exiting the runner. Hence, in order to predict correctly the performance of the draft tube using numerical simulations, the flow inside the runner must be simulated accurately. Using results from unique and detailed particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) measurements inside the runner channel of a bulb turbine, this paper presents an extensive study of the predictive capability of a widely used simulation methodology based on unsteady Reynolds-averaged Navier–Stokes equations with a k-epsilon closure model. The main objective was to identify the main parameters influencing the numerical predictions of the velocity field at the draft tube entrance in order to increase the accuracy of the simulated performance of the turbine. This paper relies on a comparison of simulations results with already published LDV measurements in the draft tube cone, interblade LDV, and stereoscopic PIV measurements within the runner. This paper presents a detailed discussion of numerical–experimental data correlation inside the runner channel and at the drat tube entrance. It shows that, contrary to widely circulated ideas, the near-wall predictions at the draft tube entrance is surprisingly good while the simulation accuracy inside the runner channels deteriorates from the leading to the trailing edges.

scholarly journals Particle Image Velocimetry Test for the Inter-Blade Vortex in a Francis Turbine

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1968
Author(s):  
Lianchen Xu ◽  
Xiaohui Jin ◽  
Zhen Li ◽  
Wanquan Deng ◽  
Demin Liu ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Load Condition ◽  
Specific Model ◽  
Francis Turbine ◽  
Stable Operation ◽  
Suction Surface ◽  
Partial Load ◽  
Image Velocimetry ◽  
Unit Speed

Hydropower units are usually operated in non-design conditions because of power grid requirements. In a partial-load condition, an inter-blade vortex phenomenon occurs between the runner blades of a Francis turbine, causing pressure pulsation and unit vibration, which hinder the safe and stable operation of power stations. However, the mechanism through which the inter-blade vortex generation occurs is not entirely clear. In this study, a specific model of the Francis turbine was used to investigate and visually observe the generation of the blade vortex in Francis turbines in both the initial inter-blade and vortex development zones. Particle image velocimetry was used for this purpose. In addition, we determined the variation law of the inter-blade vortex in the Francis turbine. We found that the size and strength of the inter-blade vortex depend on the unit speed of the turbine. The higher the unit speed is, the stronger the inter-blade vortex becomes. We concluded that the inter-blade vortex of such turbines originates from the pressure surface or secondary flow and stall of the blade at the inlet side of the runner at high unit speeds, and also from the backflow zone of the suction surface of the blade at low unit speeds.

Experimental and Numerical Analysis of the Cavitating Part Load Vortex Dynamics of Low-Head Hydraulic Turbines

2011 ◽  
Author(s):  
Se´bastien Houde ◽  
Monica S. Iliescu ◽  
Richard Fraser ◽  
Se´bastien Lemay ◽  
Gabriel D. Ciocan ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Draft Tube ◽  
Experimental Methodology ◽  
Flow Measurements ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Vortex Rope ◽  
Part Load ◽  
Image Velocimetry

The draft tube flow is a two-sided challenge for the operation of a hydraulic turbine. On one side, it is an important component for the performance of low to medium head turbines, where it can provide up to 40% of the extracted energy from the flow. On the other side, being a diffuser with a complex vorticity distribution at the inlet, vortex breakdown instability can occur at part load and generate a corkscrewed precessing vortex that can be associated with cavitation. The cavitating vortex rope, may generate undesired power output fluctuation and/or structural vibration. Therefore, draft tubes are much studied components but hard to tackle both numerically and experimentally. Within the framework of the AxialT project, the flow in the draft tube of a propeller turbine model operating at part load was studied using a combination of two-phase Particle Image Velocimetry (PIV) measurements and Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations. The paper main focus is on the experimental methodology and results. It explains how Particle Image Velocimetry measurements were implemented, validated and post-treated to provide flow measurements in the draft tube cone at part load in the cavitating and non-cavitating regimes. It also describes various image processing techniques used to extract the velocity field around the cavitating vortex rope and to estimate the location of the water-vapour interface of the cavitating region. In the spirit of feeding experimental data to numerical simulations, an analysis of measured velocity profiles just under the runner is presented. Comparison between PIV measurements and preliminary URANS simulations is also illustrated.

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