Effects of aerodynamic fairing on full scale blade fatigue test

Pan, Zujin; Wu, Jian; Sun, Yuanrong; Liu, Jian

doi:10.1088/1757-899x/207/1/012083

Cited by 5 publications

(3 citation statements)

References 6 publications

(6 reference statements)

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“…This occurs due to high aerodynamic damping resulting from the flapwise motion. Combining the biaxial test with aerodynamic fairings, as proposed by Pan et al (2017), the damping may be reduced and less force would be needed.…”

Section: Discussionmentioning

confidence: 99%

A novel rotor blade fatigue test setup with elliptical biaxial resonant excitation

Melcher¹,

Bätge²,

Neßlinger³

2019

Preprint

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Abstract. The full-scale fatigue test of rotor blades is an important and complex part of the development of new wind turbines. It is often done for certification according to the current IEC (2014) and DNV GL AS (2015) standards. Typically, a new blade design is tested by separate uniaxial fatigue tests in both main directions of the blade, i.e. flapwise and lead-lag. These tests are time consuming and rather expensive due to a high number of required load cycles, up to 5 million. Therefore, it is important to run the test as efficiently as possible. During fatigue testing, the rotor blade is excited at or near its resonant frequency. The trend for new rotor blade designs is toward longer blades, leading to a significant drop in their natural frequencies, and a corresponding increase in test time. In order to reduce the total test time, a novel test method aims to combine the two consecutive uniaxial fatigue tests into one biaxial test. The biaxial test excites the blade in both directions at the same time and at the same frequency, resulting in an elliptical deflection path of the blade axis. Using elliptical loading, counting of damage equivalent load cycles is simplified in comparison to biaxial tests with multiple frequencies. In addition, the maximum loads in both main directions remain separated, while off axis loading is introduced. To achieve such a test, specific load elements need to be arranged to equalize the natural frequencies of the test setup for both test directions. This is accomplished by adding stiffness or inertial effects in a specific direction.

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Section: Discussionmentioning

confidence: 99%

A novel rotor blade fatigue test setup with elliptical biaxial resonant excitation

Melcher¹,

Bätge²,

Neßlinger³

2019

Preprint

View full text Add to dashboard Cite

show abstract

“…The statistical gradient of the bending moment is 2%. The frequency distribution of each bending moment is converted into a cumulative equivalent bending moment according to Equation (16). Figure 15 depicts the comparison of the spatial damage distribution with the target distribution for single-point excitation and dual-point excitation.…”

Section: Fatigue Test Of the Equivalent Life Cyclementioning

confidence: 99%

“…White [14,15] developed a new hybrid fatigue testing system called the Blade Resonance Excitation (B-REX) test system, which used 65% less energy to test large wind turbine blades in half the time of NREL's (National Renewable Energy Laboratory) dual-axis forced-displacement test method, with lower equipment and operating costs. Pan [16] found that aerodynamic fairing installed in the tip of the blade could reduce air resistance; the results showed that the required exciting force could be decreased by 45.4% when the target equivalent fatigue damage was reached. Zarouchas [17] numerically and experimentally investigated the prismatic composite I-beams and the mechanical behavior of adhesive bond lines.…”

Section: Introductionmentioning

confidence: 99%

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

Pan

2017

Energies

Self Cite

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Wind turbine blades have to withstand the rigorous test of 20-25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter and saves testing energy consumption. The amplitude, phase, and frequency characteristics of the fatigue test system and, moreover, the relationship between the excitation force, damping, and the amplitude variation of the blade, are analyzed by the Lagrangian equation and the finite element simulation method. The full-scale fatigue test of an equivalent full cycle life in the flapwise direction is carried out by multi-excitation. When the frequency and phase of the multi-point exciters are consistent, the maximum vibration effect can be exerted. When the phase difference of the dual exciters is 180 • , the vibration effect produced by the dual exciters can be equivalent to each other. The blade amplitude is proportional to excitation forces, while inversely proportional to the damping ratio. The bending moment deviation of the blade is controlled within 9.2%; moreover, the energy consumption is 40% lower than that of the single-point excitation. The use of multi-point excitation allows loading the blade with high precision, stable operation, and low cost, which provides the theoretical and experimental basis for the fatigue test of large wind turbine blades.Keywords: fatigue test; wind turbine blade; multi-point excitation; damage distribution; the equivalent fatigue life cycle Highlights: (1) The multi-point excitation fatigue testing method renders an equal fatigue damage distribution with a higher degree of fidelity; (2) The program fits the fatigue damage distribution by adjusting the parameters of multi-point exciters rather than tuning masses, which could reduce each exciter power and save energy; (3) The multi-point excitation has the characteristics of high loading accuracy and stable operation, which are able to meet the large blade fatigue test requirements by adding exciters.

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Damping mechanism model for fatigue testing of a full-scale composite wind turbine blade, Part 2: Application of fairing

Lee

2018

Composite Structures

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Effects of aerodynamic fairing on full scale blade fatigue test

Cited by 5 publications

References 6 publications

A novel rotor blade fatigue test setup with elliptical biaxial resonant excitation

A novel rotor blade fatigue test setup with elliptical biaxial resonant excitation

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

Damping mechanism model for fatigue testing of a full-scale composite wind turbine blade, Part 2: Application of fairing

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