A wind-tunnel study on the power production and the wake characteristics of a small wind turbine under different yaw conditions

Abstract

A wind-tunnel experiment was carried out to examine the power generation efficiency of a stand-alone miniature wind turbine and its wake characteristics under different yaw conditions The yaw conditions involved the variability of yaw angle from -45° to 45° with an angle interval of 5 degrees for power generation measurement under the same freestream inflow velocity of 6 1 m s-1 Two resistors were used in the series circuit to study changes in the blade angular speed and power generation in the different yaw conditions As expected the maximum power output appears at the non-yaw condition and in the circuit with a lower resistor with a maximum power coefficient approximately 0 23 The amount of power generation decreases with the magnitude increase of the turbine yaw angle with a slightly fast reduction in the negative yaw angle condition The normalized power output decreases to 90-96% 68-79% 20-55% as the magnitude of the yaw angle increases to 15 30 and 45 The turbine wake characteristics at those yaw angle magnitudes are investigated through collecting the complex wake velocity components with the calibration-free cobra probe The turbulence statistics showed that the wake velocity deficit is decreased under the increased yaw angle condition and its deflecting angle is proportional to the yaw condition within the yaw angle -30° to 30° The other wakes deflecting not only does not increase instead decreases under the large yaw angle (±45°) Also the vertical velocity turbulence intensity and momentum flux are inversely proportional to yaw angle conditions On the other hand the wake characteristic is changed by the resistance value in the loaded circuit where the smaller the resistance value can obtain the obvious streamwise velocity deficit wake deflection vertical velocity and turbulence intensity

Date of Award	2019
Original language	English
Supervisor	Yu-Ting Wu (Supervisor)