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Numerical analysis of fluid-added parameters for the torsional vibration of a Kaplan turbine model runner
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-5143-7729
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. Waterpower Laboratory, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.ORCID iD: 0000-0001-7599-0895
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0001-6016-6342
2017 (English)In: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 9, no 10, article id 1687814017732893Article in journal (Refereed) Published
Abstract [en]

The impact of fluid on the runner of a hydraulic turbine is a recurrent problem. Fully coupled fluid-structure simulations are extremely time consuming. Thus, an alternative method is required to estimate this interaction to perform a reliable rotor dynamic analysis. In this paper, numerical estimations of the added inertia, damping and stiffness for a Kaplan turbine model runner are presented using transient-flow simulations. A single-degree-of-freedom model was assumed for the fluid-runner interaction, and the parameters were estimated by applying a harmonic disturbance to the angular velocity of the runner. The results demonstrate that the added inertia and damping are important, whereas the stiffness is negligible. The dimensionless added polar inertia is 23-27% of the reference value (ρR5). Damping significantly contributes to the moment at low excitation frequencies, whereas the inertia becomes dominant at higher frequencies.

Place, publisher, year, edition, pages
Sage Publications, 2017. Vol. 9, no 10, article id 1687814017732893
National Category
Fluid Mechanics and Acoustics Other Mechanical Engineering
Research subject
Fluid Mechanics; Computer Aided Design
Identifiers
URN: urn:nbn:se:ltu:diva-66314DOI: 10.1177/1687814017732893ISI: 000413891200001Scopus ID: 2-s2.0-85033435074OAI: oai:DiVA.org:ltu-66314DiVA, id: diva2:1153364
Note

Validerad;2017;Nivå 2;2017-11-09 (andbra)

Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2019-11-26Bibliographically approved
In thesis
1. An Experimental Investigation of a Prototype Kaplan Turbine and Numerical Analysis of Fluid Added Parameters on the Corresponding Model Turbine Runner
Open this publication in new window or tab >>An Experimental Investigation of a Prototype Kaplan Turbine and Numerical Analysis of Fluid Added Parameters on the Corresponding Model Turbine Runner
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Among the renewable energy sources, hydropower plays an important role by providing approximately 60% of the renewable electricity. Globally, there is a growing installed capacity of renewable energy sources. This, along with the energy policies to reduce greenhouse gas emissions promotes the development of alternative renewable energy sources such as solar and wind power. The penetration of intermittent energy sources seriously impacts the energy balance as well as the stability of the electrical grid. Therefore, it is required to guarantee a smooth integration of this share into the existing power grids. Hydraulic power plants are one of the key components to stabilize the electric grid. As a result, the extended operations and flexibility of hydraulic turbines increase, and hydraulic turbines are subject to unstable flow conditions and unfavorable load fluctuations at off-design operations. A better understanding of off-design and transient effects, particularly in full-scale hydraulic turbines, has the potential to provide new methodologies to predict the sources of load fluctuations on the runner and to mitigate issues associated with them. Such knowledge can increase turbine refurbishment time intervals and avoid structural failures in extreme cases.

This thesis aims to develop methodologies (i.e., experimental and numerical) to assess Kaplan turbines flow conditions and flow effects on the structure under different operational conditions. The work is divided into two parts; an experimental measurement campaign performed on a full-scale Kaplan turbine, Porjus U9, and a numerical investigation of fluid-structure interaction in the corresponding model turbine. In the measurement campaign, several operational conditions ranging from start-up, speed-no-load, steady-state, load variations, emergency shutdown, runaway, and stop were examined. Steady-state and load variation measurements were carried out under on-cam and off-cam conditions. The main objective was to investigate the effect of the operation conditions on the pressure and stain fluctuations on the runner as well as the strain variations on the shaft. This would lead to propose a measurement methodology in which the blade loading can be predicted by strain measurements on the shaft. The pressure and strain measurements on the runner showed that different sources of fluctuations corresponding to a specific operating condition, e.g. part load and start-up, resulted in load fluctuations on the runner blade. The region in the proximity of the runner blade hub was observed as the most critical in terms of high strain value. During a start-up sequence, the strain measurement on the shaft revealed that both guide vane opening, and runner blade’s angle have a great effect on the strain value on the shaft. A correlation between the blade and shaft measurements seems to exist.

The numerical simulations performed on the Porjus U9 model demonstrated that the added inertia and damping were important, whereas the stiffness was negligible. The dimensionless added polar inertia was 23%–27% of the reference value. Added damping significantly contributed to the moment at low excitation frequencies, whereas the inertia became dominant at higher frequencies. Considering the presence of multiple perturbations in the simulations, the added polar inertia could be assumed independent. Whereas, the interaction of the harmonics modified the added damping value, particularly at high perturbation frequencies.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2020
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76869 (URN)978-91-7790-504-2 (ISBN)978-91-7790-505-9 (ISBN)
Public defence
2020-01-31, 00:00 (English)
Opponent
Supervisors
Available from: 2019-11-26 Created: 2019-11-26 Last updated: 2020-01-10Bibliographically approved

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Soltani Dehkharqani, ArashCervantes, MichelAidanpää, Jan-Olov

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