Abstract
The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an existing wind speed spectral model. We found that the rotor power predicted by the average wind speed of the hub height is higher than the actual power in relatively weak and shallow LLJ inflow conditions, especially when the LLJ height is located inside the rotor-swept area. In terms of aerodynamic loads, when the LLJ height is located inside the rotor-swept area, the root mean square (RMS) rotor thrust coefficient and torque coefficient increase, while the RMS rotor unbalanced aerodynamic load coefficients, including lateral force, longitudinal force, tilt moment, and yaw moment, decreased. This means that the presence of both positive and negative wind shear in the rotor-swept area not only increases the rotor power but also reduces the unbalanced aerodynamic loads, which is beneficial to the operation of wind turbine. Power spectrum analysis shows no obvious difference in the power spectrum characteristics of the rotor torque and thrust in LLJ inflow conditions with different heights.
Highlights
Low-level jets (LLJs), frequently defined as wind speed maxima occurring within the lowest several hundred meters above the ground [1], are important factors to consider for wind energy, due to the increased kinetic energy available within the rotor-swept area, and for the increased potential for aerodynamic loads due to the corresponding increases in wind speed and direction variability occurring during LLJs
We studied the influence of the wind shear change caused by the change of LLJ height on rotor power and aerodynamic loads of large-scale horizontal axis wind turbines (HAWTs)
In LLJ and shear inflow conditions, the root mean square (RMS) actual rotor power obtained from FAST was compared with the RMS predicted rotor power, which was calculated by the average hub-height wind speed, as shown in Equation (11)
Summary
In the LLJ inflow condition, the simulated LLJ wind fields with heights of 87, 119, 150, 181, and 213 m to the position the of rotor bottom-tip, the middle of theheights lower half of119, the rotor, the and hub Incorrespond the LLJ inflow condition, simulated. LLJ wind fields with of 87, 150, 181, height, the middle of the upper half of the rotor, and the rotor top-tip, respectively. To quantify the 213 m correspond to the position of rotor bottom-tip, the middle of the lower half of the rotor, the hub height, the middle of the upper half of the rotor, and the rotor top-tip, respectively. 2019, 10, 132 to the position of rotor bottom-tip, the middle of the lower half of the rotor,. 9 ofthe hub height, the middle of the upper half of the rotor, and the rotor top-tip, respectively.
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