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Influence of Icing on the Modal Behavior of Wind Turbine Blades
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. (Computer Aided Design)ORCID-id: 0000-0001-8216-9464
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.ORCID-id: 0000-0001-6016-6342
Antal upphovsmän: 32016 (Engelska)Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, nr 11, artikel-id 862Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Wind turbines installed in cold climate sites accumulate ice on their structures. Icing of the rotor blades reduces turbine power output and increases loads, vibrations, noise, and safety risks due to the potential ice throw. Ice accumulation increases the mass distribution of the blade, while changes in the aerofoil shapes affect its aerodynamic behavior. Thus, the structural and aerodynamic changes due to icing affect the modal behavior of wind turbine blades. In this study, aeroelastic equations of the wind turbine blade vibrations are derived to analyze modal behavior of the Tjaereborg 2 MW wind turbine blade with ice. Structural vibrations of the blade are coupled with a Beddoes-Leishman unsteady attached flow aerodynamics model and the resulting aeroelastic equations are analyzed using the finite element method (FEM). A linearly increasing ice mass distribution is considered from the blade root to half-length and thereafter constant ice mass distribution to the blade tip, as defined by Germanischer Lloyd (GL) for the certification of wind turbines. Both structural and aerodynamic properties of the iced blades are evaluated and used to determine their influence on aeroelastic natural frequencies and damping factors. Blade natural frequencies reduce with ice mass and the amount of reduction in frequencies depends on how the ice mass is distributed along the blade length; but the reduction in damping factors depends on the ice shape. The variations in the natural frequencies of the iced blades with wind velocities are negligible; however, the damping factors change with wind velocity and become negative at some wind velocities. This study shows that the aerodynamic changes in the iced blade can cause violent vibrations within the operating wind velocity range of this turbine.

Ort, förlag, år, upplaga, sidor
2016. Vol. 9, nr 11, artikel-id 862
Nyckelord [en]
wind turbine blade, icing, natural frequency, damping
Nationell ämneskategori
Annan maskinteknik
Forskningsämne
Datorstödd maskinkonstruktion
Identifikatorer
URN: urn:nbn:se:ltu:diva-59951DOI: 10.3390/en9110862ISI: 000388580000004Scopus ID: 2-s2.0-84994344839OAI: oai:DiVA.org:ltu-59951DiVA, id: diva2:1040031
Projekt
Wind power in cold climates
Forskningsfinansiär
Energimyndigheten
Anmärkning

Validerad; 2016; Nivå 2; 2016-11-15 (andbra)

Tillgänglig från: 2016-10-26 Skapad: 2016-10-26 Senast uppdaterad: 2019-10-21Bibliografiskt granskad
Ingår i avhandling
1. Detection of blade icing and its influence on wind turbine vibrations
Öppna denna publikation i ny flik eller fönster >>Detection of blade icing and its influence on wind turbine vibrations
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Luleå University of Technology, 2019
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nationell ämneskategori
Teknisk mekanik Annan maskinteknik
Forskningsämne
Datorstödd maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-76460 (URN)978-91-7790-482-3 (ISBN)978-91-7790-483-0 (ISBN)
Disputation
2019-12-06, E632, Lulea, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-10-22 Skapad: 2019-10-21 Senast uppdaterad: 2019-11-14Bibliografiskt granskad

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Gantasala, SudhakarLuneno, Jean-ClaudeAidanpää, Jan-Olov

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