Room:
Diesel Hall
Topic:
C. Aeroservoelasticity, loads, structures and materials
Form of presentation:
Oral
Duration:
120 Minutes
Chaired by: G. van Kuik, M.H. Hansen
09:00
Structural integrity of wind turbines impacted by tropical cyclones: A case study from China
Dr. Xiao Chen | Institute of Engineering Thermophysics, Chinese Academy of Sciences | China
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Authors:
Dr. Xiao Chen | Institute of Engineering Thermophysics, Chinese Academy of Sciences | China
Chuanfeng Li | China
Jing Tang | China
This study presents a case study on wind turbines impacted by tropical cyclones in China. A quantitative investigation is conducted by integrating aerodynamic, aero-elastic and structural analysis to provide insights into structural integrity of wind turbines under extreme wind conditions. Local mean wind profiles at each turbine site are reconstructed using three-dimensional CFD calculation considering terrain topography of the wind farm. Failure modes and failure locations of rotor blades and tubular towers are predicted using finite element analysis. “The lesser of two evils†principle in the turbine design is addressed regarding the criticality of blade fracture and tower collapse. Referring to the current IEC standard for wind turbine design, it is suggested that the partial safety factor associated with failure of turbine tower should be larger than, instead of equal to, the one for the rotor blade to reduce the risk of the total loss of wind turbines in extreme wind conditions.
09:20
Gust response of aeroelastically tailored wind turbines
Dr. Alberto Pirrera | University of Bristol | United Kingdom
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Authors:
Dr. Alberto Pirrera | University of Bristol | United Kingdom
Paul M. Weaver | United Kingdom
Marco Capuzzi | United Kingdom
Samuel Scott | United Kingdom
David Langston | United Kingdom
Ervin Bossanyi | United Kingdom
Graeme McCann | United Kingdom
Some interesting challenges arise from the drive to build larger, more durable rotors that produce cheaper energy. The rationale is that, with current wind turbine designs, the power generated is theoretically proportional to the square of blade length. One enabling technology is aeroelastic tailoring that offers enhanced combined energy capture and system durability. The design of two adaptive, aeroelastically tailored blade configurations is considered here. One uses material bend-twist coupling; the other combines both material and geometric coupling. Each structural design meets a predefined coupling distribution, whilst approximately matching the stiffness of an uncoupled baseline blade. A gust analysis shows beneficial flapwise load alleviation for both adaptive blades, with the additional benefits of smoothing variations in electrical power and rotational speed.
09:40
Developing a passive load reduction blade for the DTU 10 MW reference turbine
Dr. Jacobus De Vaal | Institute for Energy Technology | Norway
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Authors:
Dr. Jacobus De Vaal | Institute for Energy Technology | Norway
Tor Anders Nygaard | Norway
Roy Stenbro | Norway
This paper presents the development of a passive load reduction blade for the DTU 10 MW reference wind turbine. Passive load reduction is achieved by introducing sweep to the path of the blade elastic axis, so that out-of-plane bending deflections result in load alleviating torsional deformations of the blade. The passive load reduction capability of a blade design is evaluated by running a selection of fatigue- and extreme load cases with the analysis tool 3DFloat and determining equivalent fatigue loads, fatigue damage and extreme loads on the tower and blade roots. The rotor flutter speed of swept blade design is also investigated. Blade designs are evaluated by varying the parameters defining the sweep path of a blade's elastic axis. Results show that a moderate amount of sweep can effectively reduce equivalent fatigue damage and extreme loads, without significantly reducing the flutter speed, or compromising annual energy production.
10:00
Effect of linear and non-linear blade modelling techniques on simulated fatigue and extreme loads using Bladed
Alec Beardsell | DNV GL | United Kingdom
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Authors:
Alec Beardsell | DNV GL | United Kingdom
William Collier | United Kingdom
Tao Han | United Kingdom
There is a trend in the wind industry towards ever larger and more flexible turbine blades. Historically, the dynamic response of wind turbine blades has been analysed using linear models of blade deflection which include the assumption of small deflections. For modern flexible blades, this assumption is becoming less valid. In order to continue to simulate dynamic turbine performance accurately, routine use of non-linear models of blade deflection may be required. In this paper, Bladed is used to compare load predictions using single-part (linear) and multi-part (non-linear) blade models for several turbines. The study examines the impact on fatigue and extreme loads through reduced sets of load calculations based on IEC 61400-1 ed. 3. Differences in edgewise-torsional coupling and in edgewise damping between the multi-part and single-part models are noted, and a causal link is identified between torsional blade dynamics and changes in ultimate load results.
10:20
Extreme load alleviation using industrial implementation of active trailing edge flaps in a full design load basis
Dr. Athanasios Barlas | DTU | Denmark
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Authors:
Dr. Athanasios Barlas | DTU | Denmark
Vasilis Pettas | Denmark
Drew Gertz | Denmark
Helge Madsen | Denmark
The application of active trailing edge flaps in an industrial oriented implementation is evaluated in terms of capability of alleviating design extreme loads. A flap system with basic control functionality is implemented and tested in a realistic full Design Load Basis (DLB) for the DTU 10MW Reference Wind Turbine (RWT) model and for an upscaled rotor version in DTU's aeroelastic code HAWC2. The flap system implementation shows considerable potential in reducing extreme loads in componets of interest including the blades, main bearing and tower top, with no influence on fatigue loads and power performance. In addition, an individual flap controller for fatigue load reduction in above rated power conditions is also implemented and integrated in the general controller architecture. The system is shown to be a techology enabler for rotor upscaling, by combining extreme and fatigue load reduction.
10:40
Aeroelastic Design and LPV Modelling of an Experimental Wind Turbine Blade equipped with Free-floating flaps
Dr. Jan-Willem van Wingerden | Delft University of Technology | Netherlands
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Authors:
Dr. Jan-Willem van Wingerden | Delft University of Technology | Netherlands
Lars Bernhammer | Netherlands
Jurij Sodja | Netherlands
Kees Slinkman | Netherlands
Gijs van Kuik | Netherlands
Sachin Navalkar | Netherlands
Trailing edge flaps located outboard on wind turbine blades have recently shown considerable potential in the alleviation of turbine lifetime dynamic loads. The concept of the free-floating flap is specifically interesting for wind turbines, on account of its modularity and enhanced control authority. Such a flap is free to rotate about its axis; camberline control of the free-floating flap allows for aeroelastic control of blade loads. This paper describes the design of a scaled wind turbine blade instrumented with free-floating flaps, intended for use in wind tunnel experiments. The nature of the flap introduces a coupled form of flutter due to the aeroelastic coupling of flap rigid-body and blade out-of-plane modes; for maximal control authority it is desired to operate close to the flutter limit. Analytical and numerical methods are used to perform a flutter analysis of the turbine blade. It is shown that the potential flow aeroelastic model can be recast as a continuous-time Linear-Parameter-Varying (LPV) state space model of a low order, for which formal controller design methodologies are readily available.