| 概要 |
The present study scrutinized the impacts of terrain-induced turbulence on wind turbine blades, examining actual measurement data regarding wind conditions and strains of wind turbine blades, which we...re obtained at the #10 wind turbine of the Kushikino Reimei Wind Farm (established in November of 2012) in Hashima Ichikikushikino City, Kagoshima Prefecture, Japan. In the measurement period (November 3, 2015, 0:00–March 17, 2016, 7:00 AM JST), a time period of 9:40–9:50 AM JST on November 13, 2015 was identified as being when the maximum value of 2.03 in the Fatigue Damage Equivalent Load (DEL) on wind turbine blades was shown due to an easterly wind. It was revealed that if airflow with the property of DEL 2.03 continued for 5.88 years, the total load on wind turbine blades would reach the design load for the designed service life. We performed a high-resolution numerical simulation based on Large-Eddy Simulation (LES) and identified the three-dimensional airflow structure of terrain-induced turbulence that had been considered to be generated due to the proximity of Mt. Benzaiten (elevation 519 m), located 300 m upriver of the #10 wind turbine, when an easterly wind occurred. We also defined the Uchida–Kawashima Scale 1 (U–K scale_1), which is an index regarding wind conditions, as the value obtained by a calculation where the standard deviation assessed at the wind turbine hub height was normalized by the wind speed at the maximum height above the ground point of the flow boundary, and thus, clarified the existence of the terrain-induced turbulence quantitatively. The threshold value of the U–K scale_1, the wind condition index, was determined as 0.2, and this index was confirmed to not be dependent on the height direction distributions of inflow wind speed, the influences of the horizontal grid resolution, and the influences of the computed azimuth. A linear trend was recognized in wind turbine operation at a wind speed of 4 m/s or higher between nacelle wind velocity (and its standard deviation) and the DEL. It was shown that both the nacelle wind speed (and its standard deviation) and the fatigue equivalent load (DEL) can be approximated by the regression line. In the present study, Fatigue Damage Evaluation Index, the U–K scale_2 was defined. The U–K scale_2, which is an index regarding load, was obtained by the calculation using two types of regression lines calculated on the basis of the following actual measurement values, and the design value obtained on the basis of BLADED: one regression line was the northerly wind results as the Low-Turbulence Flow Case and the other was that of easterly wind as the High-Turbulence Flow case. The U–K scale_2 was equal to the ratio of the integrated value in measured DEL to the integrated value in design DEL (BLADED). Data of both northerly and easterly winds were extracted from actual measurement data for the one-year period from April of 2015–March of 2016, corresponding to a 4 m/s or higher wind speed in the wind turbine operation. Subsequently, using these extracted data and the U–K scale_2, the influence of terrain-induced turbulence on age-related degradation of wind turbine blades was evaluated quantitatively. Consequently, the following results were revealed: the northerly wind was within the designed value, the U–K scale_2 = 0.86 < 1.0. Contrarily, the value of the easterly wind was the U–K scale_2 = 1.60 > 1.0 and exceeded the designed value. Furthermore, the integrated value of Fatigue Damage was approximately 1.9 times greater in the case of the easterly wind than in the case of the northerly wind. Based on this result, it was revealed that the blades of the #10 wind turbine were directly and strongly affected by the terrain-induced turbulence when easterly winds occurred.続きを見る
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