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Shiraghaee, S., Sundström, J., Raisee, M. & Cervantes, M. J. (2024). Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation. Renewable energy, 225, Article ID 120232.
Open this publication in new window or tab >>Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation
2024 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 225, article id 120232Article in journal (Refereed) Published
Abstract [en]

The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load operation is particularly detrimental since the development of a rotating vortical structure termed rotating vortex rope (RVR) in the draft tube leads to periodic pressure pulsations that jeopardize turbine performance. This paper experimentally explores a novel solution involving the protrusion of flat plates into the turbine draft tube. Three flat plates equally separated by 120° were vertically installed on the draft tube wall. The plates were protruded up to 83% of the draft tube local radius under four different part-load conditions. Their impact was observed through time-resolved pressure measurements in the draft tube and vaneless space, as well as efficiency measurements. The results demonstrated successful RVR mitigation, achieving a maximum 85% reduction in pressure oscillation amplitudes. Protruding flat plates disrupted RVR periodicity and coherence, confining its orbit to the draft tube center. This approach proved particularly effective at lower part-load conditions, enhancing turbine hydraulic efficiency by increasing torque extraction. Reducing the adverse effects under part load, the proposed method appears promising in extending the operational range of hydraulic turbines.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Hydropower, Part-load, Pressure measurement, Rotating vortex rope, Turbine efficiency, Vortex rope mitigation
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104627 (URN)10.1016/j.renene.2024.120232 (DOI)2-s2.0-85187203326 (Scopus ID)
Funder
EU, Horizon 2020, 814958
Note

Validerad;2024;Nivå 2;2024-03-18 (hanlid);

Full text license: CC BY

Available from: 2024-03-18 Created: 2024-03-18 Last updated: 2024-03-18Bibliographically approved
Kalantar Neyestanaki, M., Dunca, G., Jonsson, P. & Cervantes, M. J. (2024). Extending the pressure-time method to bend using 3D-CFD. Flow Measurement and Instrumentation, 96, Article ID 102535.
Open this publication in new window or tab >>Extending the pressure-time method to bend using 3D-CFD
2024 (English)In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 96, article id 102535Article in journal (Refereed) Published
Abstract [en]

According to the IEC 60041 standard, the pressure-time method (1D PTM) can be employed to determine the flow rate in hydraulic turbines. This method assumes a one-dimensional flow and applies to straight pipes with uniform cross-sections, with specific restrictions on the pipe length, fluid velocity, and distance between the measurement sections from any irregularities in the pipeline. However, challenges arise when applying this method in low-head hydropower plants due to the short lengths, irregularities like bends and developing flows in the intake. The present paper aims to improve the performance of the method in the presence of a bend. To this end, a test rig has been developed and measurements performed, including such geometry. The data are evaluated using the development of a newly proposed approach combining the 1D PTM based on an energy balance formulation and three-dimensional computational fluid dynamics (3D CFD) developed for axis-symmetrical accelerating flows. The updated methodology includes a correction of the experimental pressure measurements used in the 1D PTM to account for the effects of the Dean vortices present after the bend as well as the kinetic energy correction factors which deviate from known values in transient conditions. The results obtained under conditions involving the presence of bends either between or in close proximity to one show a significant improvement compared to the standard one-dimensional pressure-time method.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
3D CFD, Bend, Low-head hydraulic turbine, Pressure-time method out of IEC 60041
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-103997 (URN)10.1016/j.flowmeasinst.2024.102535 (DOI)2-s2.0-85182870156 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-02-26 (joosat);

Full text license: CC-BY

Available from: 2024-01-29 Created: 2024-01-29 Last updated: 2024-02-26Bibliographically approved
Kalantar Neyestanaki, M., Dunca, G., Jonsson, P. & Cervantes, M. J. (2024). Extending the Pressure-Time Method to Pipe With Variable Cross-Section With Three-Dimensional Numerical Simulations. Journal of Fluids Engineering, 146(2), Article ID 021305.
Open this publication in new window or tab >>Extending the Pressure-Time Method to Pipe With Variable Cross-Section With Three-Dimensional Numerical Simulations
2024 (English)In: Journal of Fluids Engineering, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 146, no 2, article id 021305Article in journal (Refereed) Published
Place, publisher, year, edition, pages
ASME Press, 2024
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-102519 (URN)10.1115/1.4063491 (DOI)001147728000011 ()2-s2.0-85182877054 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-11-20 (joosat);

Available from: 2023-11-20 Created: 2023-11-20 Last updated: 2024-03-11Bibliographically approved
Kumar, S., Cervantes, M. J. & Gandhi, B. (2024). Flow Field Analysis of Francis Turbine Draft Tube using POD at Design and Part Load Operating Conditions. Journal of Applied Fluid Mechanics, 17(4), 770-784
Open this publication in new window or tab >>Flow Field Analysis of Francis Turbine Draft Tube using POD at Design and Part Load Operating Conditions
2024 (English)In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 17, no 4, p. 770-784Article in journal (Refereed) Published
Abstract [en]

The hydraulic turbines, especially Francis turbines, frequently run at part load (PL) conditions to meet the dynamic energy needs. The flow field at the runner exit changes significantly with a change in the operating point. At PL, flow instabilities such as the Rotating Vortex Rope (RVR) form in the draft tube of the Francis turbine. The present paper compares the features of the velocity and vorticity field of the Francis turbine draft tube at the best efficiency point (BEP) and PL operations using the Proper Orthogonal Decomposition (POD) of the 2D-PIV data. The POD analysis decomposes the flow field into coherent and incoherent structures describing the spatiotemporal behavior of the flow field. A visual representation of the coherent structures and the turbulent length scales in the flow field is extracted and analyzed for BEP and PL, respectively. The study highlights the salient features of the draft tube flow field, which differentiate the BEP and PL operation. The fast Fourier transform of the temporal coefficients confirms the presence of RVR frequency (0.29 times the runner frequency) at PL. The phase portraits of different modes elucidate the relationship between different harmonics of the RVR frequency at PL.

Place, publisher, year, edition, pages
Isfahan University of Technology, 2024
Keywords
POD, Part load, Vortex rope, Dissipation, Francis Turbine
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104298 (URN)10.47176/jafm.17.4.2274 (DOI)001156482800010 ()
Note

Full text license: CC BY-NC-ND 4.0; 

Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-02-19
Seifi, Z., Raisee, M. & Cervantes, M. J. (2024). Linear global stability analysis of a transient swirling flow leading to the formation of a helical precessing vortex breakdown in a straight diffuser. European journal of mechanics. B, Fluids, 103, 43-57
Open this publication in new window or tab >>Linear global stability analysis of a transient swirling flow leading to the formation of a helical precessing vortex breakdown in a straight diffuser
2024 (English)In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 103, p. 43-57Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Part-load, Rotating vortex rope, Stability analysis, Turbomachinery, Turbulence, Transient simulation
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-101663 (URN)10.1016/j.euromechflu.2023.08.004 (DOI)001075975400001 ()2-s2.0-85170645395 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-10-16 (joosat);

Available from: 2023-10-16 Created: 2023-10-16 Last updated: 2023-10-16Bibliographically approved
Khullar, S., Kumar, S., Singh, K. M., Cervantes, M. J. & Gandhi, B. K. (2024). Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations. Sadhana (Bangalore), 49(1), Article ID 81.
Open this publication in new window or tab >>Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations
Show others...
2024 (English)In: Sadhana (Bangalore), ISSN 0256-2499, E-ISSN 0973-7677, Vol. 49, no 1, article id 81Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Springer Nature, 2024
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104492 (URN)10.1007/s12046-023-02366-y (DOI)2-s2.0-85185560933 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-03-07 (hanlid);

Funder: Central Power Research Institute (CPR-1133-MID, CPR-1799-MID)

Available from: 2024-03-07 Created: 2024-03-07 Last updated: 2024-03-07Bibliographically approved
Kalantar Neyestanaki, M., Dunca, G., Jonsson, P. & Cervantes, M. J. (2023). A Comparison of Different Methods for Modelling Water Hammer Valve Closure with CFD. Water, 15(8), Article ID 1510.
Open this publication in new window or tab >>A Comparison of Different Methods for Modelling Water Hammer Valve Closure with CFD
2023 (English)In: Water, E-ISSN 2073-4441, Vol. 15, no 8, article id 1510Article in journal (Refereed) Published
Abstract [en]

Water hammer is a transient phenomenon that occurs when a flowing fluid is rapidly decelerated, which can be harmful and damaging to a piping system. Three-dimensional computational fluid dynamics (CFD) with three-dimensional geometry is a common tool for studying water hammer, which is more accurate than numerical simulation with one-dimension approximation of the geometry. There are different methods with different accuracy and computational costs for valve closure modelling. This paper presents the result of water hammer 3D simulation with three main technics for modelling an axial valve closure: dynamic mesh, sliding mesh, and immersed solid methods. The variation of the differential pressure variation and the wall shear stress are compared with experimental results. Additionally, the 3D effects of the flow after the valve closure and the computational cost are addressed. The sliding mesh method presents the most physical results compared to the other two methods. The immersed solid method predicts a smaller pressure rise which may be the result of using a source term in the momentum equation instead of modelling the valve movement. The dynamic mesh method adds fluctuations to the primary phenomenon. Moreover, the sliding mesh is less expensive than the dynamic mesh method in terms of computational cost (approximately one-third), which was the primary method for axial valve closure modelling in the literature.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
CFD, dynamic mesh, immersed solid, sliding mesh, water hammer
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-97162 (URN)10.3390/w15081510 (DOI)000979578300001 ()2-s2.0-85156220314 (Scopus ID)
Funder
Luleå University of TechnologySwedish Energy AgencySwedish National GridKTH Royal Institute of TechnologyChalmers University of TechnologyUppsala University
Note

Validerad;2023;Nivå 2;2023-05-16 (hanlid)

Available from: 2023-05-16 Created: 2023-05-16 Last updated: 2024-02-01Bibliographically approved
Goyal, R., Cervantes, M. J., Masoodi, F. A. & Sahu, P. (2023). A Study of the Velocity Field During Mitigation of Vortex Breakdown in Model Francis Turbine at High Load. Journal of Fluids Engineering, 145(4), Article ID 041203.
Open this publication in new window or tab >>A Study of the Velocity Field During Mitigation of Vortex Breakdown in Model Francis Turbine at High Load
2023 (English)In: Journal of Fluids Engineering, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 145, no 4, article id 041203Article in journal (Refereed) Published
Abstract [en]

Off-design operation leads to the development of flow instabilities like vortex breakdown phenomenon which manifests as an enlarged vortex core in the draft tube at high load operating conditions. These flow instabilities are known to potentially have detrimental effects on turbine performance necessitating investigations on their formative and mitigation mechanisms. This work clarifies the evolving velocity maps characterizing vortex breakdown seen in a model Francis turbine draft tube during the transition from high load to best efficiency point. Velocity measurements have been performed inside a draft tube cone using a 2D particle image velocimetry system. Results show a wake-like velocity profile characterizing the vortex core in the draft tube cone at high load condition. The vortex core is a centrally located flow feature embodying a quasi-stagnant flow with recirculation regions. Surrounding the core, an axial outflow is seen with shear layers arising at the interface of core and outflow due to a substantial velocity gradient. Mitigation of this vortex core through a load rejection operation was further investigated. It is seen that as the flowrate approaches the best efficiency point, the shear layers between the outflow and central stagnation region break. The breakup leads to an axially dominated and streamlined flow. This is enabled by the reduction of the swirl until no central flow separation at the stagnation point occurs. The flow at the best efficiency point is thus devoid of the vortex core due to the absence of flow stagnation, the primary instability causing the core development.

Place, publisher, year, edition, pages
Asme, 2023
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-97290 (URN)10.1115/1.4056614 (DOI)000971891800005 ()
Note

Validerad;2023;Nivå 2;2023-05-23 (joosat);

Funder: Ministry of Education, India; Swedish Water Power Center; Norwegian Hydropower Center

Available from: 2023-05-23 Created: 2023-05-23 Last updated: 2023-05-23Bibliographically approved
Shiraghaee, S., Sundström, J., Mehrdad, R. & Cervantes, M. J. (2023). Characterization of The Rotating Vortex Rope Pressure Oscillations in a Kaplan Model Turbine Draft Tube. International Journal of Fluid Machinery and Systems, 16(2), 204-218
Open this publication in new window or tab >>Characterization of The Rotating Vortex Rope Pressure Oscillations in a Kaplan Model Turbine Draft Tube
2023 (English)In: International Journal of Fluid Machinery and Systems, ISSN 1882-9554, Vol. 16, no 2, p. 204-218Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Korean Society for Fluid Machinery, 2023
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-103336 (URN)10.5293/ijfms.2023.16.2.204 (DOI)
Note

Godkänd;2024;Nivå 0;2024-01-01 (hanlid);

Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2023-12-18Bibliographically approved
Raisee, M. & Cervantes, M. J. (2023). Determination of all hydrodynamic added properties resulting from fluid structure interactions using singular value decomposition. Journal of Fluids and Structures, 120, Article ID 103898.
Open this publication in new window or tab >>Determination of all hydrodynamic added properties resulting from fluid structure interactions using singular value decomposition
2023 (English)In: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 120, article id 103898Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-97891 (URN)10.1016/j.jfluidstructs.2023.103898 (DOI)001011896100001 ()2-s2.0-85160004874 (Scopus ID)
Projects
Swedish Hydropower Centre (SVC)
Funder
Luleå University of TechnologySwedish Energy AgencySwedish National GridKTH Royal Institute of TechnologyChalmers University of TechnologyUppsala University
Note

Validerad;2023;Nivå 2;2023-06-08 (hanlid);

Funder: Elforsk

Available from: 2023-06-08 Created: 2023-06-08 Last updated: 2024-03-07Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7599-0895

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