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Gantasala, S. & Aidanpää, J.-O. (2019). A Preliminary Experiment to Excite and Identify Modal Frequencies of a Rotor in the Rotating Frame of Reference. In: Katia Lucchesi Cavalca, Hans Ingo Weber (Ed.), Proceedings of the 10th International Conference on Rotor Dynamics – IFToMM: . Paper presented at 10th International Conference on Rotor Dynamics – IFToMM, SEP 23-27 2018 (pp. 265-277). Cham: Springer
Åpne denne publikasjonen i ny fane eller vindu >>A Preliminary Experiment to Excite and Identify Modal Frequencies of a Rotor in the Rotating Frame of Reference
2019 (engelsk)Inngår i: Proceedings of the 10th International Conference on Rotor Dynamics – IFToMM / [ed] Katia Lucchesi Cavalca, Hans Ingo Weber, Cham: Springer, 2019, s. 265-277Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The current work uses two types of excitation on a rotating shaft to identify its modal frequencies. The first one is a non-contact excitation where an oscillating magnet is placed near the shaft, eddy currents generated by the oscillating magnetic field excites vibrations in the shaft. In the second type of excitation, a miniature electrodynamical exciter powered by a decoder amplifier board is placed on the shaft to excite vibrations with predefined frequencies in a signal (mp3 format) stored on the USB flash drive connected to the board. The shaft is rotated at different speeds and vibration accelerations are measured using a small data logger placed on the shaft while excited using these two excitation systems. These two types of asynchronous excitation on the shaft excites both forward and backward whirl vibration modes of the rotor system. The modal frequencies are identified at the peak amplitudes in the waterfall plots of the measured vibration accelerations to a chirp excitation of the shaft. A Campbell diagram is plotted with the identified modal frequencies of the shaft in the rotating frame of reference.

sted, utgiver, år, opplag, sider
Cham: Springer, 2019
Serie
Mechanisms and Machine Science, ISSN 2211-0984 ; 62
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-70522 (URN)10.1007/978-3-319-99270-9_19 (DOI)2-s2.0-85051798726 (Scopus ID)978-3-319-99269-3 (ISBN)978-3-319-99270-9 (ISBN)
Konferanse
10th International Conference on Rotor Dynamics – IFToMM, SEP 23-27 2018
Tilgjengelig fra: 2018-08-21 Laget: 2018-08-21 Sist oppdatert: 2018-08-29bibliografisk kontrollert
Gantasala, S. & Aidanpää, J.-O. (2019). A Preliminary Experiment to Excite and Identify Modal Frequencies of a Rotor in the Rotating Frame of Reference. In: Cavalca, Katia Lucchesi; Weber, Hans Ingo (Ed.), Proceedings of the 10th International Conference on Rotor Dynamics: IFToMM. Paper presented at 10th International Conference on Rotor Dynamics, 23-27 September 2018, Rio de Janeiro, Brazil (pp. 265-277). Springer, 3
Åpne denne publikasjonen i ny fane eller vindu >>A Preliminary Experiment to Excite and Identify Modal Frequencies of a Rotor in the Rotating Frame of Reference
2019 (engelsk)Inngår i: Proceedings of the 10th International Conference on Rotor Dynamics: IFToMM / [ed] Cavalca, Katia Lucchesi; Weber, Hans Ingo, Springer, 2019, Vol. 3, s. 265-277Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The current work uses two types of excitation on a rotating shaft to identify its modal frequencies. The first one is a non-contact excitation where an oscillating magnet is placed near the shaft, eddy currents generated by the oscillating magnetic field excites vibrations in the shaft. In the second type of excitation, a miniature electrodynamical exciter powered by a decoder amplifier board is placed on the shaft to excite vibrations with predefined frequencies in a signal (mp3 format) stored on the USB flash drive connected to the board. The shaft is rotated at different speeds and vibration accelerations are measured using a small data logger placed on the shaft while excited using these two excitation systems. These two types of asynchronous excitation on the shaft excites both forward and backward whirl vibration modes of the rotor system. The modal frequencies are identified at the peak amplitudes in the waterfall plots of the measured vibration accelerations to a chirp excitation of the shaft. A Campbell diagram is plotted with the identified modal frequencies of the shaft in the rotating frame of reference.

sted, utgiver, år, opplag, sider
Springer, 2019
Serie
Mechanisms and Machine Science, ISSN 2211-0984, E-ISSN 2211-0992
Emneord
Modal frequency, Rotor Excitation, Campbell diagram, Rotating frame of reference
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-70964 (URN)10.1007/978-3-319-99270-9_19 (DOI)978-3-319-99269-3 (ISBN)978-3-319-99270-9 (ISBN)
Konferanse
10th International Conference on Rotor Dynamics, 23-27 September 2018, Rio de Janeiro, Brazil
Tilgjengelig fra: 2018-09-25 Laget: 2018-09-25 Sist oppdatert: 2019-11-22bibliografisk kontrollert
Gantasala, S. (2019). Detection of blade icing and its influence on wind turbine vibrations. (Doctoral dissertation). Luleå University of Technology
Åpne denne publikasjonen i ny fane eller vindu >>Detection of blade icing and its influence on wind turbine vibrations
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Wind turbine installations in extreme conditions like cold climate have increased over thelast few years and expected to grow in future in North America, Europe, and Asia regions due to good wind resources and land availability. Their installed capacity could reach 186 GW by the end of 2020. The cold climate sites impose the risk of ice accumulation on turbines during the winter due to the humidity at low temperatures. Since the atmospheric and operating conditions of the wind turbine leading to blade icing vary stochastically in space and time, the resulting ice accumulation is completely random, it is even different for turbines within the same site. Ice accumulation alters aerofoil shapes of the blade, affecting their aeroelastic behavior. The icing severity at different locations of the blade and their non-uniform distribution on blades have a distinct influence on turbine power output and vibrations. The current thesis proposes a methodology to investigate such behavior of wind turbines by considering the structural and aerodynamic property changes in the blade due to icing. An automated procedure is used to scale simulated/measured ice shape on aerofoil sections of the blade according to a specified ice mass distribution. The aeroelastic behavior of the blades is simulated considering the static aerodynamic coefficients of the iced aerofoil sections. The proposed methodology is demonstrated on the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine model. The method can be leveraged to analyze the influence of icing on any wind turbine model. De/Anti-icing systems are installed on the turbines to mitigate the risks associated with icing. It is essential to detect icing at the early stage and initiate these systems to avoid production losses and limit the risks associated with ice throw. Ice accumulation increases blade mass and its spatial distribution changes natural frequencies of the blade. A detection technique is proposed in this thesis to characterize ice mass distribution on the blades based on its natural frequencies. The detection technique is validated using experiments on a small-scale cantilever beam and 1-kW wind turbine blade set-ups and its effectiveness is also verified on large-scale wind turbine blades using numerical models. The proposed technique has the potential for detecting ice masses on large wind turbines operating in cold climate as it requires only first few natural frequencies of the blade. These natural frequencies are usually excited by the turbulent wind in operation/standstill conditions and they can be estimated from the vibration measurements of the blade.

sted, utgiver, år, opplag, sider
Luleå University of Technology, 2019
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-76460 (URN)978-91-7790-482-3 (ISBN)978-91-7790-483-0 (ISBN)
Disputas
2019-12-06, E632, Lulea, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2019-10-22 Laget: 2019-10-21 Sist oppdatert: 2019-11-14bibliografisk kontrollert
Gantasala, S., Tabatabaei, N., Cervantes, M. & Aidanpää, J.-O. (2019). Numerical Investigation of the Aeroelastic Behavior of a Wind Turbine with Iced Blades. Energies, 12(12), Article ID 2422.
Åpne denne publikasjonen i ny fane eller vindu >>Numerical Investigation of the Aeroelastic Behavior of a Wind Turbine with Iced Blades
2019 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 12, artikkel-id 2422Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Wind turbines installed in cold-climate regions are prone to the risks of ice accumulation which affects their aeroelastic behavior. The studies carried out on this topic so far considered icing in a few sections of the blade, mostly located in the outer part of the blade, and their influence on the loads and power production of the turbine are only analyzed. The knowledge about the influence of icing in different locations of the blade and asymmetrical icing of the blades on loads, power, and vibration behavior of the turbine is still not matured. To improve this knowledge, multiple simulation cases are needed to run with different ice accumulations on the blade considering structural and aerodynamic property changes due to ice. Such simulations can be easily run by automating the ice shape creation on aerofoil sections and two-dimensional (2-D) Computational Fluid Dynamics (CFD) analysis of those sections. The current work proposes such methodology and it is illustrated on the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine model. The influence of symmetrical icing in different locations of the blade and asymmetrical icing of the blade assembly is analyzed on the turbine’s dynamic behavior using the aeroelastic computer-aided engineering tool FAST. The outer third of the blade produces about 50% of the turbine’s total power and severe icing in this part of the blade reduces power output and aeroelastic damping of the blade’s flapwise vibration modes. The increase in blade mass due to ice reduces its natural frequencies which can be extracted from the vibration responses of the turbine operating under turbulent wind conditions. Symmetrical icing of the blades reduces loads acting on the turbine components, whereas asymmetrical icing of the blades induces loads and vibrations in the tower, hub, and nacelle assembly at a frequency synchronous to rotational speed of the turbine.

sted, utgiver, år, opplag, sider
MDPI, 2019
Emneord
wind turbine, icing, simulation, aeroelastic behavior, CFD
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-71180 (URN)10.3390/en12122422 (DOI)000473821400195 ()
Merknad

Validerad;2019;Nivå 2;2019-07-05 (johcin)

Tilgjengelig fra: 2018-10-12 Laget: 2018-10-12 Sist oppdatert: 2019-10-21bibliografisk kontrollert
Tabatabaei, N., Gantasala, S. & Cervantes, M. (2019). Wind Turbine Aerodynamic Modeling in Icing Condition: Three-Dimensional RANS-CFD Versus Blade Element Momentum Method. Journal of energy resources technology, 141(7), Article ID 071201.
Åpne denne publikasjonen i ny fane eller vindu >>Wind Turbine Aerodynamic Modeling in Icing Condition: Three-Dimensional RANS-CFD Versus Blade Element Momentum Method
2019 (engelsk)Inngår i: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 141, nr 7, artikkel-id 071201Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Icing limits the performance of wind turbines in cold climates. The prediction of the aerodynamic performance losses and their distribution due to ice accretion is essential. Blade element momentum (BEM) is the basis of blade structural studies. The accuracy and limitations of this method in icing condition are assessed in the present study. To this purpose, a computational study on the aerodynamic performance of the full-scale NREL 5 MW rotor is performed. Three-dimensional (3D) steady Reynolds-averaged Navier–Stokes (RANS) simulations are performed for both clean and iced blade, as well as BEM calculations using two-dimensional (2D) computational fluid dynamics (CFD) sectional airfoil data. The total power calculated by the BEM method is in close agreement with the 3D CFD results for the clean blade. There is a 4% deviation, while it is underestimated by 28% for the iced one. The load distribution along the clean blade span differs between both methods. Load loss due to the ice, predicted by 3D CFD, is 32% in extracted power and the main loss occurs at the regions where the ice horn height exceeds 8% of the chord length.

sted, utgiver, år, opplag, sider
ASME, 2019
HSV kategori
Forskningsprogram
Strömningslära; Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-73824 (URN)10.1115/1.4042713 (DOI)000470845800013 ()2-s2.0-85063888524 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-05-03 (johcin)

Tilgjengelig fra: 2019-05-03 Laget: 2019-05-03 Sist oppdatert: 2019-07-01bibliografisk kontrollert
Gantasala, S., Luneno, J.-C. & Aidanpää, J.-O. (2018). Identification of ice mass accumulated on wind turbine blades using its natural frequencies. Wind Engineering: The International Journal of Wind Power, 42(1), 66-84
Åpne denne publikasjonen i ny fane eller vindu >>Identification of ice mass accumulated on wind turbine blades using its natural frequencies
2018 (engelsk)Inngår i: Wind Engineering: The International Journal of Wind Power, ISSN 0309-524X, E-ISSN 2048-402X, Vol. 42, nr 1, s. 66-84Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This work demonstrates a technique to identify information about the ice mass accumulation on wind turbine blades using its natural frequencies, and these frequencies reduce differently depending on the spatial distribution of ice mass along the blade length. An explicit relation to the natural frequencies of a 1-kW wind turbine blade is defined in terms of the location and quantity of ice mass using experimental modal analyses. An artificial neural network model is trained with a data set (natural frequencies and ice masses) generated using that explicit relation. After training, this artificial neural network model is given an input of natural frequencies of the iced blade (identified from experimental modal analysis) corresponding to 18 test cases, and it identified ice masses’ location and quantity with a weighted average percentage error value of 17.53%. The proposed technique is also demonstrated on the NREL 5-MW wind turbine blade data.

sted, utgiver, år, opplag, sider
Sage Publications, 2018
Emneord
Wind turbine blade, ice detection, natural frequency, experimental modal analysis, artificial neural network
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-65213 (URN)10.1177/0309524X17723207 (DOI)000419838000005 ()2-s2.0-85040450029 (Scopus ID)
Prosjekter
Wind power in cold climates
Forskningsfinansiär
Swedish Energy Agency
Merknad

Validerad;2018;Nivå 2;2018-01-23 (andbra)

Tilgjengelig fra: 2017-08-21 Laget: 2017-08-21 Sist oppdatert: 2019-10-21bibliografisk kontrollert
Tabatabaei, N., Cervantes, M. J. & Gantasala, S. (2018). Wind turbine aerodynamic modelling in icing condition: 3D RANS-CFD vs BEM method. Journal of energy resources technology
Åpne denne publikasjonen i ny fane eller vindu >>Wind turbine aerodynamic modelling in icing condition: 3D RANS-CFD vs BEM method
2018 (engelsk)Inngår i: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994Artikkel i tidsskrift (Fagfellevurdert) Submitted
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-71181 (URN)
Tilgjengelig fra: 2018-10-12 Laget: 2018-10-12 Sist oppdatert: 2018-10-16
Gantasala, S., Luneno, J.-C. & Aidanpää, J.-O. (2017). Investigating How an Artificial Neural Network Model Can Be Used to Detect Added Mass on a Non-Rotating Beam Using Its Natural Frequencies: A Possible Application for Wind Turbine Blade Ice Detection. Energies, 10(2), Article ID 184.
Åpne denne publikasjonen i ny fane eller vindu >>Investigating How an Artificial Neural Network Model Can Be Used to Detect Added Mass on a Non-Rotating Beam Using Its Natural Frequencies: A Possible Application for Wind Turbine Blade Ice Detection
2017 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, nr 2, artikkel-id 184Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Structures vibrate with their natural frequencies when disturbed from their equilibrium position. These frequencies reduce when an additional mass accumulates on their structures, like ice accumulation on wind turbines installed in cold climate sites. The added mass has two features: the location and quantity of mass. Natural frequencies of the structure reduce differently depending on these two features of the added mass. In this work, a technique based on an artificial neural network (ANN) model is proposed to identify added mass by training the neural network with a dataset of natural frequencies of the structure calculated using different quantities of the added mass at different locations on the structure. The proposed method is demonstrated on a non-rotating beam model fixed at one end. The length of the beam is divided into three zones in which different added masses are considered, and its natural frequencies are calculated using a finite element model of the beam. ANN is trained with this dataset of natural frequencies of the beam as an input and corresponding added masses used in the calculations as an output. ANN approximates the non-linear relationship between these inputs and outputs. An experimental setup of the cantilever beam is fabricated, and experimental modal analysis is carried out considering a few added masses on the beam. The frequencies estimated in the experiments are given as an input to the trained ANN model, and the identified masses are compared against the actual masses used in the experiments. These masses are identified with an error that varies with the location and the quantity of added mass. The reason for these errors can be attributed to the unaccounted stiffness variation in the beam model due to the added mass while generating the dataset for training the neural network. Therefore, the added masses are roughly estimated. At the end of the paper, an application of the current technique for detecting ice mass on a wind turbine blade is studied. A neural network model is designed and trained with a dataset of natural frequencies calculated using the finite element model of the blade considering different ice masses. The trained network model is tested to identify ice masses in four test cases that considers random mass distributions along the blade. The neural network model is able to roughly estimate ice masses, and the error reduces with increasing ice mass on the blade.

sted, utgiver, år, opplag, sider
MDPI, 2017
Emneord
artificial neural network, ice mass, detection, wind turbine blade, natural frequency
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-61885 (URN)10.3390/en10020184 (DOI)000395469200038 ()2-s2.0-85014095862 (Scopus ID)
Prosjekter
Wind power in cold climates
Forskningsfinansiär
Swedish Energy Agency
Merknad

Validerad; 2017; Nivå 2; 2017-02-15 (andbra)

Tilgjengelig fra: 2017-02-09 Laget: 2017-02-09 Sist oppdatert: 2019-10-21bibliografisk kontrollert
Thiery, F., Gantasala, S. & Aidanpää, J.-O. (2017). Numerical evaluation of multilobe bearings using the Spectral Method. Advances in Mechanical Engineering, 9(7)
Åpne denne publikasjonen i ny fane eller vindu >>Numerical evaluation of multilobe bearings using the Spectral Method
2017 (engelsk)Inngår i: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 9, nr 7Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Hydropower rotors and pumps have the specificity to be oriented vertically, meaning that the bearing forces have to be evaluated at each time-step depending on the position of the rotor for dynamical analyses. If the bearing forces cannot be evaluated analytically, a suitable numerical method should be used to calculate the pressure distribution over the bearing domain. This process can be computationally expensive as it should be performed for each discrete time-step. As a result, a comparison between the spectral method, the finite difference method, and the finite element method is performed to investigate which method is more adapted to dynamical analysis of the bearing. It is observed that the spectral method has the advantage of having a reasonable simulation time for any eccentricity magnitude with a moderate number of interpolation points. However, this method should be restricted to simple bearing models such as plain bearings or multilobe bearings due to the advantage of finding a global numerical solution directly on the entire bearing/pad domain

sted, utgiver, år, opplag, sider
Sage Publications, 2017
HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-63122 (URN)10.1177/1687814017707135 (DOI)000405521000001 ()2-s2.0-85026484512 (Scopus ID)
Merknad

Validerad; 2017; Nivå 2; 2017-08-16 (andbra)

Tilgjengelig fra: 2017-04-24 Laget: 2017-04-24 Sist oppdatert: 2018-07-10bibliografisk kontrollert
Gantasala, S., Luneno, J.-C., Aidanpää, J.-O. & Cervantes, M. (2016). Aeroelastic simulations of wind turbine using 13 DOF rigid beam model (ed.). Paper presented at International Symposium on Transport Phenomena and Dynamics of Rotating Machinery : 10/04/2016 - 15/04/2016. Paper presented at International Symposium on Transport Phenomena and Dynamics of Rotating Machinery : 10/04/2016 - 15/04/2016.
Åpne denne publikasjonen i ny fane eller vindu >>Aeroelastic simulations of wind turbine using 13 DOF rigid beam model
2016 (engelsk)Konferansepaper, Oral presentation only (Fagfellevurdert)
Abstract [en]

The vibration behavior of wind turbine substructures is mainly dominated by their first few vibration modes because wind turbines operate at low rotational speeds. In this study, 13 degrees of freedom (DOF) model of a wind turbine is derived considering fundamental vibration modes of the tower and blades which are modelled as rigid beams with torsional springs attached at their root. Linear equations of motion (EOM) governing the structural behavior of wind turbines are derived by assuming small amplitude vibrations. This model is used to study the coupling between the structural and aerodynamic behavior of NREL 5 MWmodel wind turbine. Aeroelastic natural frequencies of the current model are compared with the results obtained from the finite element model of this wind turbine. Quasi-steady aerodynamic loads are calculated considering wind velocity changes due to height and tower shadow effects. In this study, vibration responses are simulated at various wind velocities. The derived 13 DOF simplified model of the wind turbine enables to simulate the influence ofchange in parameters and operating conditions on vibration behavior with less computational effort. Besides that, the results of the simplified models can be interpreted with much ease.

HSV kategori
Forskningsprogram
Datorstödd maskinkonstruktion; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-32570 (URN)71b9860a-5951-4f01-890c-78a58cd41753 (Lokal ID)71b9860a-5951-4f01-890c-78a58cd41753 (Arkivnummer)71b9860a-5951-4f01-890c-78a58cd41753 (OAI)
Konferanse
International Symposium on Transport Phenomena and Dynamics of Rotating Machinery : 10/04/2016 - 15/04/2016
Merknad
Godkänd; 2016; 20160512 (sudgan)Tilgjengelig fra: 2016-09-30 Laget: 2016-09-30 Sist oppdatert: 2019-10-21bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0001-8216-9464