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Soltani Dehkharqani, ArashORCID iD iconorcid.org/0000-0001-5143-7729
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Publications (10 of 12) Show all publications
Soltani Dehkharqani, A. (2020). An Experimental Investigation of a Prototype Kaplan Turbine and Numerical Analysis of Fluid Added Parameters on the Corresponding Model Turbine Runner. (Doctoral dissertation). Luleå: Luleå tekniska universitet
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: 2020-06-04Bibliographically approved
Soltani Dehkharqani, A., Engström, F., Aidanpää, J.-O. & Cervantes, M. (2020). An Indirect Measurement Methodology to Identify Load Fluctuations on Axial Turbine Runner Blades. Sensors, 20(24), Article ID 7220.
Open this publication in new window or tab >>An Indirect Measurement Methodology to Identify Load Fluctuations on Axial Turbine Runner Blades
2020 (English)In: Sensors, E-ISSN 1424-8220, Vol. 20, no 24, article id 7220Article in journal (Refereed) Published
Abstract [en]

Smooth integration of intermittent energy sources, such as solar and wind power, into the electrical grid induces new operating conditions of the hydraulic turbine by increasing the off-design operations, start/stops, and load variations. Therefore, hydraulic turbines are subject to unstable flow conditions and unfavorable load fluctuations. Predicting load fluctuations on the runner using indirect measurements can allow for optimized operations of the turbine units, increase turbine refurbishment time intervals, and avoid structural failures in extreme cases. This paper investigates an experimental methodology to assess and predict the flow condition and load fluctuations on a Kaplan turbine runner at several steady-state operations by performing measurements on the shaft in the rotating and stationary frame of references. This unit is instrumented with several transducers such as miniature pressure transducers, strain gages, and proximity probes. The results show that for any propeller curve of a Kaplan turbine, the guide vane opening corresponding to the minimum pressure and strain fluctuations on the runner blade can be obtained by axial, torsion, and bending measurements on the shaft. Torsion measurements on the shaft could support index-testing in Kaplan turbines particularly for updating the cam-curve during the unit operation. Furthermore, a signature of every phenomenon observed on the runner blade signals, e.g., runner frequency, rotating vortex rope components, and rotor-stator interaction, is found in the data obtained from the shaft.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
prototype Kaplan turbine, load fluctuation on the runner, pressure measurement, strain measurement, axial strain, torsion strain, bending strain, indirect measurement
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Machine Design
Identifiers
urn:nbn:se:ltu:diva-82030 (URN)10.3390/s20247220 (DOI)000603243400001 ()33339455 (PubMedID)2-s2.0-85098144932 (Scopus ID)
Note

Validerad;2021;Nivå 2;2021-01-04 (alebob);

Finansiär: Svenskt Vattenkraftcentrum

Available from: 2020-12-17 Created: 2020-12-17 Last updated: 2023-09-05Bibliographically approved
Soltani Dehkharqani, A., Engström, F., Aidanpää, J.-O. & Cervantes, M. (2020). Experimental Investigation of a 10 MW Prototype Axial Turbine Runner: Vortex Rope Formation and Mitigation. Journal of Fluids Engineering, 142(10), Article ID 101212.
Open this publication in new window or tab >>Experimental Investigation of a 10 MW Prototype Axial Turbine Runner: Vortex Rope Formation and Mitigation
2020 (English)In: Journal of Fluids Engineering, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 142, no 10, article id 101212Article in journal (Refereed) Published
Abstract [en]

The transient load fluctuations on the runner blades of prototype hydraulic turbines during load variations are one of the main causes of fatigue and eventual structural failure. A clear understanding of the dynamic loads on the runner blades is required to detect the source of the fluctuations. In this paper, an experimental investigation of vortex rope formation and mitigation in a prototype Kaplan turbine, namely, Porjus U9, is carried out. Synchronized unsteady pressure and strain measurements were performed on a runner blade during steady-state and load variation under off-cam condition. The normalized pressure fluctuation during load variations remained approximately within ±0.2 Pref for all the pressure transducers installed on the blade pressure side and is even slightly lower during the transient cycle. Higher pressure fluctuations were found on the blade suction side, approximately four times higher than that of on the pressure side. The synchronous and asynchronous components of the vortex rope were clearly observed at the low discharge operating point and transient cycles. The spectral analysis of the pressure signals showed that the synchronous component appears before the asynchronous component during the load reduction, and it lasts longer during the load increase. These frequencies slightly change during the load variation. In addition, the results proved that the strain fluctuation component on the runner blade arises from the synchronous component of the vortex rope at low discharge while the asynchronous component influence is negligible.

Place, publisher, year, edition, pages
American Society for Mechanical Engineers (ASME), 2020
Keywords
prototype Kaplan turbine, pressure measurement, strain measurement, Vortex rope
National Category
Other Mechanical Engineering Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics; Machine Design
Identifiers
urn:nbn:se:ltu:diva-80915 (URN)10.1115/1.4047793 (DOI)000567334100012 ()2-s2.0-85098222274 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-09-24 (alebob)

Available from: 2020-09-24 Created: 2020-09-24 Last updated: 2023-09-05Bibliographically approved
Soltani Dehkharqani, A., Engström, F., Aidanpää, J.-O. & Cervantes, M. (2019). Experimental Investigation of a 10 MW Prototype Kaplan Turbine during Start-Up Operation. Energies, 12(23), Article ID 4852.
Open this publication in new window or tab >>Experimental Investigation of a 10 MW Prototype Kaplan Turbine during Start-Up Operation
2019 (English)In: Energies, E-ISSN 1996-1073, Vol. 12, no 23, article id 4852Article in journal (Refereed) Published
Abstract [en]

An increase in the start/stop cycles of hydraulic turbines due to the penetration of intermittent renewable energy sources is important. Hydraulic instabilities that occur in hydraulic turbines during start/stops may cause structural issues in the turbine components. High-stress fluctuations on the runner blades are expected during start-ups due to the unsteady pressure loading on the runner blades. This paper presents experiments performed on a 10 MW prototype Kaplan turbine at the Porjus Hydropower Center during a start-up cycle. Synchronized unsteady pressure and strain measurements on a runner blade and axial, bending (in two directions) and torsion strain measurements on the shaft were performed. In addition, the general parameters of the turbine (e.g., rotational speed, guide vane opening and runner blade angle) were acquired. Low-frequency fluctuations (0–15 Hz) were observed in the pressure data on the runner blade after opening the guide vanes from the completely closed position. A higher strain value was observed on the strain gauges installed on the runner blade near the hub (200–500 μm/m ) compared to the ones near the shroud at the leading and trailing edge. The strain fluctuation level on the shaft decreased after loading the generator by further opening the guide vanes. Higher fluctuations were observed in the torsion strain compared to axial and bending strain. In addition, the torsion strain peak-to-peak value reached 12 times its corresponding value at 61% guide vane opening.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
prototype Kaplan turbine, start-up, pressure measurement, strain measurement, axial strain, bending strain, torsion strain
National Category
Fluid Mechanics and Acoustics Other Mechanical Engineering
Research subject
Fluid Mechanics; Computer Aided Design
Identifiers
urn:nbn:se:ltu:diva-77053 (URN)10.3390/en12234582 (DOI)000508355500008 ()2-s2.0-85076238316 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-01-03 (johcin)

Available from: 2019-12-03 Created: 2019-12-03 Last updated: 2023-09-05Bibliographically approved
Soltani Dehkharqani, A., Aidanpää, J.-O., Engström, F. & Cervantes, M. (2019). Fluid added polar inertia and damping for the torsional vibration of a Kaplan turbine model runner considering multiple perturbations. In: IOP Conference Series: Earth and Environmental Science. Paper presented at 29th IAHR Symposium on Hydraulic Machinery and Systems, 17-21 September 2018, Kyoto, Japan.. Institute of Physics (IOP), 240, Article ID 062007.
Open this publication in new window or tab >>Fluid added polar inertia and damping for the torsional vibration of a Kaplan turbine model runner considering multiple perturbations
2019 (English)In: IOP Conference Series: Earth and Environmental Science, Institute of Physics (IOP), 2019, Vol. 240, article id 062007Conference paper, Published paper (Refereed)
Abstract [en]

A water turbine runner is exposed to several perturbation sources with differentfrequencies, phases, and amplitudes both at the design and off-design operations. Rotor-statorinteraction, cavitation, rotating vortex rope, and blade trailing edge vortices are examples of suchperturbations which can disturb the runner. The rotor dynamic coefficients require beingdetermined to perform a reliable dynamic analysis. Fluid added inertia, damping, and stiffnesshave previously been investigated for individual perturbation frequencies for the torsionalvibration of a Kaplan turbine model runner. However, a number of perturbation sources mostlytake place simultaneously and alter the dynamics of the runner. Soltani et al. [1] have evaluatedthe torsional added parameters for a Kaplan turbine runner using numerical simulationsconsidering single perturbation frequency. In the present work, the fluid added parameters areassessed in the presence of multiple perturbation sources. A similar methodology is used. Asingle-degree-of-freedom (SDOF) model for the dynamic model and unsteady ReynoldsaveragedNavier–Stokes approach for the flow simulations are assumed. Perturbations withdifferent frequencies are applied to the rotational speed of the runner to determine the fluid addedparameters for the torsional vibration. A number of previously investigated frequencies arechosen and their combinations are investigated. In addition, two different phase shifts areconsidered between the applied perturbations to study the effect of phase. Two more test caseswith higher perturbation amplitude are also conducted to investigate its influence on the fluidadded inertia and damping. The results are compared with the previous study and the interactionof multiple perturbations on the added parameters is investigated.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
National Category
Mechanical Engineering Fluid Mechanics and Acoustics Other Mechanical Engineering
Research subject
Fluid Mechanics; Computer Aided Design
Identifiers
urn:nbn:se:ltu:diva-72503 (URN)10.1088/1755-1315/240/6/062007 (DOI)000560282601091 ()2-s2.0-85063961671 (Scopus ID)
Conference
29th IAHR Symposium on Hydraulic Machinery and Systems, 17-21 September 2018, Kyoto, Japan.
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2023-09-05Bibliographically approved
Cervantes, M. & Soltani Dehkharqani, A. (2019). Prototype Kaplan turbine measurements: Instrumentation overview. In: : . Paper presented at 2nd IAHR-Asia Symposium on Hydraulic Machinery and Systems, Busan, Korea, September 24-25, 2019.
Open this publication in new window or tab >>Prototype Kaplan turbine measurements: Instrumentation overview
2019 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

This paper presents the instrumentation of a full-scale Kaplan turbine and some preliminary results from a measuring campaign. Miniature pressure sensors and strain gauges were installed on a runner blade as well as strain gauges on the shaft. The goal is to investigate the machine at different operating conditions and find a relation between the sensors on the blade and the shaft. The preliminary results indicate a successful strategy to instrument the Kaplan turbine.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76675 (URN)
Conference
2nd IAHR-Asia Symposium on Hydraulic Machinery and Systems, Busan, Korea, September 24-25, 2019
Available from: 2019-11-11 Created: 2019-11-11 Last updated: 2021-04-28Bibliographically approved
Soltani Dehkharqani, A., Aidanpää, J.-O., Engström, F. & Cervantes, M. (2018). A Review of Available Methods for the Assessment of Fluid Added Mass, Damping, and Stiffness With an Emphasis on Hydraulic Turbines. Applied Mechanics Review, 70(5), Article ID 050801.
Open this publication in new window or tab >>A Review of Available Methods for the Assessment of Fluid Added Mass, Damping, and Stiffness With an Emphasis on Hydraulic Turbines
2018 (English)In: Applied Mechanics Review, ISSN 0003-6900, E-ISSN 1088-8535, Vol. 70, no 5, article id 050801Article in journal (Refereed) Published
Abstract [en]

Fluid added mass, damping, and stiffness are highly relevant parameters to consider when evaluating the dynamic response of a submerged structure in a fluid. The prediction of these parameters for hydraulic turbines has been approached relatively recently. Complex fluid-structure analyses including three-dimensional flow and the need for experiments during operation are the main challenges for the numerical and experimental approaches, respectively. The main objective of this review is to address the impact of different parameters, for example, flow velocity, cavitation, nearby solid structure, and rotational speed on the fluid added mass and damping of Kaplan/Propeller and Francis turbine runners. The fluid added stiffness is also discussed in the last section of the paper. Although studies related to hydraulic turbines are the main objective of this paper, the literature on hydrofoils is also taken into consideration to provide valuable information on topics such as individual runner blades. In this literature survey, the analytical, numerical, and experimental approaches used to determine fluid added parameters are discussed, and the pros and the cons of each method are addressed.

Place, publisher, year, edition, pages
American Society for Mechanical Engineers (ASME), 2018
Keywords
fluid added mass, fluid added damping, fluid added stiffness, Francis turbine, Kaplan turbine, hydrofoils
National Category
Fluid Mechanics and Acoustics Other Mechanical Engineering
Research subject
Fluid Mechanics; Computer Aided Design
Identifiers
urn:nbn:se:ltu:diva-72502 (URN)10.1115/1.4042279 (DOI)000458511300001 ()2-s2.0-85059957623 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-29 (svasva)

Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2023-09-05Bibliographically approved
Soltani Dehkharqani, A., Cervantes, M. & Aidanpää, J.-O. (2017). Numerical analysis of fluid-added parameters for the torsional vibration of a Kaplan turbine model runner. Advances in Mechanical Engineering, 9(10), Article ID 1687814017732893.
Open this publication in new window or tab >>Numerical analysis of fluid-added parameters for the torsional vibration of a Kaplan turbine model runner
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
National Category
Fluid Mechanics and Acoustics Other Mechanical Engineering
Research subject
Fluid Mechanics; Computer Aided Design
Identifiers
urn:nbn:se:ltu:diva-66314 (URN)10.1177/1687814017732893 (DOI)000413891200001 ()2-s2.0-85033435074 (Scopus ID)
Note

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

Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2023-09-05Bibliographically approved
Dehkharqani, A. S., Amiri, K. & Cervantes, M. (2015). Steady and transient pressure measurements on the runner blades of a Kaplan turbine model (ed.). Paper presented at IAHR meeting of the Working Group “Cavitation and dynamic problems" : 09/09/2015 - 11/09/2015. Paper presented at IAHR meeting of the Working Group “Cavitation and dynamic problems" : 09/09/2015 - 11/09/2015.
Open this publication in new window or tab >>Steady and transient pressure measurements on the runner blades of a Kaplan turbine model
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The development of renewable energy sources has increased the need for power regulation. Power system regulation is mainly performed by hydropower plants through load variations. Additional forces are exerted on the runner blades during these load variations. This paper deals with pressure measurement performed on the blades of a Kaplan turbine model under steady state and load variation conditions. Flow behavior and frequency content of the pressure are investigated and compared to find critical condition in terms of pressure fluctuation. The results show that at various operating points and conditions, different regions of the blade are important. During load rejection, a considerable amount of pressure fluctuations are exerted on the runner blades. These results will be used to define experiments to be performed on the corresponding prototype. On the prototype, the loads acting on the runner blades will be investigated at various operation points similar to the model. In addition, the relation between the frequency content on the blades and loads on the main shaft will be investigated. Comparing results from model and prototype eventually would be valuable to explore the flow characteristics in prototype since CFD simulation of prototype is challenging.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-26989 (URN)0483c990-33a4-4860-b187-6204b09379e3 (Local ID)0483c990-33a4-4860-b187-6204b09379e3 (Archive number)0483c990-33a4-4860-b187-6204b09379e3 (OAI)
Conference
IAHR meeting of the Working Group “Cavitation and dynamic problems" : 09/09/2015 - 11/09/2015
Note
Godkänd; 2015; 20150918 (arasol)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2023-09-06Bibliographically approved
Dehkharqani, A. S., Boroomand, M. & Eshraghi, H. (2014). A Numerical Investigation of Loss Coefficient Variation in Various Incidence Angles in Tandem Blades Cascade (ed.). In: (Ed.), (Ed.), A Numerical Investigation of Loss Coefficient Variation in Various Incidence Angles in Tandem Blades Cascade: . Paper presented at ASME 2014 International Mechanical Engineering Congress & Exposition : 14/11/2014 - 20/11/2014.
Open this publication in new window or tab >>A Numerical Investigation of Loss Coefficient Variation in Various Incidence Angles in Tandem Blades Cascade
2014 (English)In: A Numerical Investigation of Loss Coefficient Variation in Various Incidence Angles in Tandem Blades Cascade, 2014Conference paper, Published paper (Refereed)
Abstract [en]

There is a severe tendency to reduce weight and increase power of gas turbine. Such a requirement is fulfilled by higher pressure ratio of compressor stages. Employing tandem blades in multi-stage axial flow compressors is a promising methodology to control separation on suction sides of blades and simultaneously implement higher turning angle to achieve higher pressure ratio. The present study takes into account the high flow deflection capabilities of the tandem blades consisting of NACA-65 airfoil with fixed percent pitch and axial overlap at various flow incidence angles. In this regard, a two-dimensional cascade model of tandem blades is constructed in a numerical environment. The inlet flow angle is varied in a wide range and overall loss coefficient and deviation angles are computed. Moreover, the flow phenomena between the blades and performance of both forward and afterward blades are investigated. At the end, the aerodynamic flow coefficient of tandem blades are also computed with equivalent single blades to evaluate the performance of such blades in both design and off-design domain of operations. The results show that tandem blades are quite capable of providing higher deflection with lower loss in a wide range of operation and the base profile can be successfully used in design of axial flow compressor. In comparison to equivalent single blades, tandem blades have less dissipation because the momentum exerted on suction side of tandem blades confines the size of separation zone near trailing edges of blades.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:ltu:diva-32430 (URN)10.1115/IMECE2014-39881 (DOI)2-s2.0-84926298722 (Scopus ID)6ec6ea71-e553-4ff5-b292-0a503e4f1e1b (Local ID)6ec6ea71-e553-4ff5-b292-0a503e4f1e1b (Archive number)6ec6ea71-e553-4ff5-b292-0a503e4f1e1b (OAI)
Conference
ASME 2014 International Mechanical Engineering Congress & Exposition : 14/11/2014 - 20/11/2014
Note
Upprättat; 2014; 20150331 (arasol)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2022-11-08Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5143-7729

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