Experimental investigation on power generation efficiency and wake characteristics of a model wind turbine under periodic and oscillatory inflow conditions

Abstract

This study conducted wind tunnel experiments to study the power generation efficiency and wake characteristics of the model wind turbine under different unsteady inflow conditions Unlike most previous wind tunnel experiments with non-varying oscillatory inflow conditions this study emphasized measurements (including electrical current blade rotating speed and turbulent wake velocity components) under the inflow velocity with a sinusoidal variation (e g 5 to 8 2 m/s) The power coefficient under five resistances of 15 17 9 19 7 23 4 and 25 1 ohms is estimated with the instantaneous maximum mechanical power coefficient of 0 47 The electrical current blade rotating speed tip speed ration and power coefficient have varying distributions strongly associated with the sinusoidal inflow(periodic inflow)velocity variation that has a period of 30 seconds The magnitude of the variation in the electrical current and blade rotating speed (also associated with tip speed ratio) is found to decrease with an increase of the resistances which indicates that the inflow velocity variation causes a small effect on the turbine operation connected with a larger resistance The statistics of the wake measurements summarized two important points The first point is that the wind velocity of the periodic inflow changes from top to bottom so the turbulence intensity of its wake (TI = 0 055) is greater than twice that of the oscillating inflow (TI = 0 025) The second point is that the periodic inflow characteristics from 120-second instantaneous velocity components at each measurement point can be filtered out through Fourier transform at ±4 wavenumbers The filtered wake has characteristics similar to that under the oscillatory inflow condition

Date of Award	2020
Original language	English
Supervisor	Yu-Ting Wu (Supervisor)