Strain gauge measurements on a full scale tidal turbine blade

Large-scale cooling system fans often operate under distorted inlet air flow conditions due to the presence of other fans and the prevalent wind conditions. Strain gauge measurements have been used to determine the blade loading as a result of the unsteady aerodynamic forces. However, these measurements are of the blade’s response to the aerodynamic forces and include the deformation as a result of the first natural frequency being excited. When considering the dominant first natural frequency and bending mode of the fan blade, one can approximate the fan blade as a cantilever beam that acts as a single degree-of-freedom system. The response of a single degree-of-freedom system can be calculated analytically for any excitation if the system’s properties are known. The current investigation focuses on using these equations to create an algorithm that can be applied to the measured response of a fan blade to then extract the aerodynamic forces exciting it. This is performed by using a simple non-linear, least-squares optimization algorithm to fit a complex Fourier series to the response and using the coefficients of each harmonic term to determine the Fourier series representing the excitation function. The algorithm was first tested by applying it to the response of a finite element cantilever beam representing a simplified model of the fan blade. Good results were obtained for a variety of excitation forces and as such the algorithm was then applied to the measured response of a full-scale fan blade. The full-scale blade was excited with a shaker where the forcing function could be accurately controlled. Once validated, the algorithm was applied to a set of strain gauge measurements that were recorded at a full-scale fan while in operation. The reconstructed aerodynamic loading showed increased forces when the blade passed beneath the fan bridge as well as when it approached the windward side of the casing.

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Rotor Loading Characteristics of a Full-Scale Tidal Turbine

Energies ◽

10.3390/en12061035 ◽

2019 ◽

Vol 12 (6) ◽

pp. 1035 ◽

Cited By ~ 6

Author(s):

Magnus Harrold ◽

Pablo Ouro

Keyword(s):

Turbulent Flows ◽

Mechanical Loading ◽

Full Scale ◽

Design Stage ◽

Flow Profile ◽

Expected Return ◽

Tidal Turbines ◽

Theoretical Predictions ◽

Tidal Turbine

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively over-engineer the device at additional cost. Both of these scenarios have consequences on the expected return from the project. Despite an extensive amount of research on the mechanical loading of model scale tidal turbines, very little is known from full-scale devices operating in real sea conditions. This paper addresses this by reporting on the rotor loads measured on a 400 kW tidal turbine. The results obtained during ebb tidal conditions were found to agree well with theoretical predictions of rotor loading, but the measurements during flood were lower than expected. This is believed to be due to a disturbance in the approaching flood flow created by the turbine frame geometry, and, to a lesser extent, the non-typical vertical flow profile during this tidal phase. These findings outline the necessity to quantify the characteristics of the turbulent flows at sea sites during the entire tidal cycle to ensure the long-term integrity of the deployed tidal turbines.

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Assessment of the strain gauge technique for measurement of wind turbine blade loads

Wind Energy ◽

10.1002/1099-1824(200001/03)3:1<35::aid-we30>3.0.co;2-d ◽

2000 ◽

Vol 3 (1) ◽

pp. 35-65 ◽

Cited By ~ 17

Author(s):

K. Papadopoulos ◽

E. Morfiadakis ◽

T. P. Philippidis ◽

D. J. Lekou

Keyword(s):

Wind Turbine ◽

Turbine Blade ◽

Strain Gauge ◽

Wind Turbine Blade ◽

Blade Loads

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A New Modified Contrast Method for Life Prediction in Combined Cycle Fatigue Test

Volume 7A: Structures and Dynamics ◽

10.1115/gt2017-64435 ◽

2017 ◽

Cited By ~ 1

Author(s):

Lei Han ◽

Cao Chen ◽

Xiaoyong Zhang ◽

Xiaojun Yan

Keyword(s):

Turbine Blade ◽

High Cycle Fatigue ◽

Aerodynamic Force ◽

Low Cycle Fatigue ◽

Fracture Morphology ◽

Combined Cycle ◽

Full Scale ◽

Cycle Fatigue ◽

Contrast Method ◽

Ultra High Cycle Fatigue

The combined high and low cycle fatigue (CCF) test on full scale turbine blade in the laboratory is an important method to evaluate the life. In fact, the low cycle fatigue which is usually caused by the centrifugal force can be confirmed easily. While, the high cycle fatigue which is usually caused by the vibration and aerodynamic force is often hard to determine. So the previous scholar has proposed the contrast method to determine the high cycle load in the field. This method utilizes the new and used blades to determine the high cycle within certain limits. While it can’t be applied effectively in the whole life range with the low cycle-high cycle-ultra high cycle fatigue theory raised. So this paper put forward the modified contrast method to realize the optimization. Firstly, the CCF tests are carried out on the turbine blade systematically. Then, the CCF damage properties, including the crack propagation, the fracture morphology and the dynamic characteristic are analyzed. Lastly, the new modified contrast method is proposed with the new coordinate axes, new fitting criterions and amend method. Through comparisons we conclude that: the new method is slightly complicated, but the evaluate precision has significantly increased. So it could be used to deal with data for CCF tests on full scale turbine blade in the future.

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A method of determining test load for full-scale wind turbine blade fatigue tests

Journal of Mechanical Science and Technology ◽

10.1007/s12206-018-1006-y ◽

2018 ◽

Vol 32 (11) ◽

pp. 5097-5104 ◽

Cited By ~ 2

Author(s):

Qiang Ma ◽

Zong-Wen An ◽

Jian-Xiong Gao ◽

Hai-Xia Kou ◽

Xue-Zong Bai

Keyword(s):

Wind Turbine ◽

Turbine Blade ◽

Fatigue Tests ◽

Full Scale ◽

Wind Turbine Blade ◽

Test Load

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Strain Gauge Measurements from Bone Surfaces

Mechanical Testing of Bone and the Bone-Implant Interface ◽

10.1201/9781420073560.ch20 ◽

1999 ◽

pp. 305-320

Author(s):

John Szivek ◽

Vasanti Gharpuray

Keyword(s):

Strain Gauge ◽

Strain Gauge Measurements

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Experimental analysis of the shear flow effect on tidal turbine blade root force from three-dimensional mean flow reconstruction

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2020.0001 ◽

2020 ◽

Vol 378 (2178) ◽

pp. 20200001 ◽

Cited By ~ 1

Author(s):

B. Gaurier ◽

Ph. Druault ◽

M. Ikhennicheu ◽

G. Germain

Keyword(s):

Turbine Blade ◽

Dimensional Space ◽

Three Dimensional ◽

Tidal Energy ◽

Velocity Shear ◽

Reconstruction Method ◽

Mean Flow ◽

Blade Root ◽

Image Velocimetry ◽

Tidal Turbine

In the main tidal energy sites like Alderney Race, turbulence intensity is high and velocity fluctuations may have a significant impact on marine turbines. To understand such phenomena better, a three-bladed turbine model is positioned in the wake of a generic wall-mounted obstacle, representative of in situ bathymetric variation. From two-dimensional Particle Image Velocimetry planes, the time-averaged velocity in the wake of the obstacle is reconstructed in the three-dimensional space. The reconstruction method is based on Proper Orthogonal Decomposition and enables access to a representation of the mean flow field and the associated shear. Then, the effect of the velocity gradient is observed on the turbine blade root force, for four turbine locations in the wake of the obstacle. The blade root force average decreases whereas its standard deviation increases when the distance to the obstacle increases. The angular distribution of this phase-averaged force is shown to be non-homogeneous, with variation of about 20% of its time-average during a turbine rotation cycle. Such force variations due to velocity shear will have significant consequences in terms of blade fatigue. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

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