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Numerical Investigation of the Aeroelastic Behavior of a Wind Turbine with Iced Blades
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.ORCID-id: 0000-0001-8216-9464
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.ORCID-id: 0000-0002-6025-2280
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.ORCID-id: 0000-0001-7599-0895
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.ORCID-id: 0000-0001-6016-6342
2019 (Engelska)Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 12, artikel-id 2422Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
MDPI, 2019. Vol. 12, nr 12, artikel-id 2422
Nyckelord [en]
wind turbine, icing, simulation, aeroelastic behavior, CFD
Nationell ämneskategori
Energiteknik Strömningsmekanik och akustik Annan maskinteknik
Forskningsämne
Datorstödd maskinkonstruktion; Strömningslära
Identifikatorer
URN: urn:nbn:se:ltu:diva-71180DOI: 10.3390/en12122422ISI: 000473821400195OAI: oai:DiVA.org:ltu-71180DiVA, id: diva2:1255437
Anmärkning

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

Tillgänglig från: 2018-10-12 Skapad: 2018-10-12 Senast uppdaterad: 2019-10-21Bibliografiskt granskad
Ingår i avhandling
1. Impact of Icing on Wind Turbines Aerodynamic
Öppna denna publikation i ny flik eller fönster >>Impact of Icing on Wind Turbines Aerodynamic
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Alternativ titel[sv]
Påverkan av isbildning på vindkraftverk aerodynamik
Abstract [en]

Wind energy covered 11.6% of Europe electricity demand in 2017. Region with cold climates represent a strong potential for wind energy companies because of their sparse population and proper wind conditions. The global wind energy installations in cold climate regions is forecasted to reach a capacity of 186 GW by the end of 2020. But wind turbines installed in cold climate regions are prone to the risks of ice accumulation which affects their aerodynamics behavior, as well as the safety, and structural loads.

The aerodynamic forces on wind turbine can be affected in two main ways: ice accretion changes the blade profile, and thus the flow path curvature, and the surface roughness. The importance of these two parameters depend on the ice type. The target ice type for this thesis is the smooth leading-edge glaze ice with horn shape. The aerodynamic consequences of the blade profile change because of the mentioned ice type are studied in detail. 

The findings of this thesis are classified in five main sections. The first section considers the methodology to model the performance of a wind turbine. The wake behind the turbine is also explored. Different aspects of the simulation methods with computational fluid dynamics using the Reynolds-averaged Navier-Stokes equations are investigated in both steady state and transient. In the second section, the time-dependent effects of icing are studied, exploring the moving vortices created by the irregularity of the ice and their frequencies and amplitudes. The main frequency modes of the flow dynamics were analyzed. In the third section, three-dimensional simulation of icing is implemented and the fluid flow arrangement through the rotor is investigated. Two well-recognized approaches are applied and compared, which are Blade Element Momentum (BEM) and CFD. An automated setup is programmed and launched to implement multiple CFD simulations to provide the aerodynamic data for structural analysis in the fourth section. The developed methodology is illustrated on a large-scale wind turbine. In section five, the effects of the uncertain level of ice-accretion is studied through an uncertainty quantification method. The aerodynamic losses are statistically discussed. Then, a scenario study is conducted according to the obtained polynomial chaos expansion, in which the probability distribution of wind power loss due to icing is inspected.

The achievements of this thesis can be used in to design of a wind turbine which is supposed to work in a cold climate, as well as assess the economics of a predesigned wind turbine working in a cold region.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå tekniska universitet, 2018
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nationell ämneskategori
Energiteknik Teknisk mekanik Strömningsmekanik och akustik
Forskningsämne
Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-71186 (URN)978-91-7790-228-7 (ISBN)978-91-7790-229-4 (ISBN)
Disputation
2018-12-06, E231, Luleå, Luleå, 13:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2018-10-15 Skapad: 2018-10-12 Senast uppdaterad: 2020-01-07Bibliografiskt granskad
2. 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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