Effects of Gust and Turbulence on Transient Loads and Performance of 5MW Wind Turbine Using the IEC Model and Constrained Stochastic Simulation

• Main Authors: Lyu-RanWang, 王律然
• Other Authors: Jen-Fin Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/24052806698152175472

碩士 === 國立成功大學 === 機械工程學系 === 102 === SUMMARY The effects of gust and turbulence on wind turbines are discussed using IEC model and constrained stochastic simulation. The transient effects of gust are characterized as two parameters, tendency and turbulence intensity. Choosing some sets of tendency and turbulence intensity, generate four different transient velocity series, called NewGust. Including IEC gust, there are five transient velocity series as inlet boundary conditions of wind tunnel in CFD simulation. From results of simulations, the thrust, torque, and mechanical power of rotor are similar to transient inlet velocity series. By observing pressure coefficients on blade surface, as wind velocity comes to maximum, there is no change in boundary layer state on the blade surfaces of location 30%,60%,90%. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. It is showed that the velocity deficit is higher at downstream distance 0.5DR and 1DR behind wind turbine. And the velocity deficit decrease dramatically at downstream distance 2DR. The largest difference in averaged TI occurs at downstream distance 1DR ~1.5DR , it is showed that the vortex structure breakdown at this region. INTRODUCTION In order to design more efficient and high stability wind turbines, the Aerodynamics simulation of wind turbine is the important topic. Currently, the large -scale wind turbines is the main tendency of wind energy development. From some articles, CFD simulation of wind turbines is almost for the small-scale wind turbines. However, there are few research of CFD simulation for the large-scale wind turbines. And there no research about gust effects on large-scale wind turbines. In view of this, the effects of gust and turbulence on large-scale wind turbines are discussed using CFD simulation. MATERIALS AND METHODS The transient effects of gust are characterized as two parameters, tendency and turbulence intensity. Choosing some sets of tendency and turbulence intensity, generate four different transient velocity series, called NewGust. Including IEC gust, there are five transient velocity series as inlet boundary conditions of wind tunnel in CFD simulation. From pressure and velocity field, the loading and performance of wind turbines in transient velocity series can be calculated. Next, the flow character and transient loading series can do more analysis. RESULTS AND DISCUSSION From results of simulations, the thrust, torque, and mechanical power of rotor are similar to transient inlet velocity series. As wind velocity comes to maximum, the thrust and torque of rotor in IEC gust are higher than those in NewGust. As Ten is 17%, TI increasing, the thrust and torque of rotor increase. However, As Ten is 65%, TI increasing, the thrust and torque of rotor decrease. By observing pressure coefficients on blade surface, as wind velocity comes to maximum, there is no change in boundary layer state on the blade surfaces of location 30%,60%,90%. Because of transient effect of wind velocity rapidly increasing, the negative pressure coefficients of blade surface decrease suddenly. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. The direction of loading frequently changes with time, which cause more fatigue damages on structure compared with steady wind condition. It is showed that the velocity deficit is higher at downstream distance 0.5DR and 1DR behind wind turbine. And the velocity deficit decrease dramatically at downstream distance 2DR. The largest difference in averaged TI occurs at downstream distance 1DR ~1.5DR , it is showed that the vortex structure breakdown at this region. Consequently, the wake of the region from wind turbine to downstream distance 1DR is classify as near wake. And the wake of the region behind downstream distance 1.5DR is classify as far wake. CONCLUSION As Ten is 17%, TI increasing, the thrust and torque of rotor increase. However, As Ten is 65%, TI increasing, the thrust and torque of rotor decrease. Because of transient effect of wind velocity rapidly increasing, the negative pressure coefficients of blade surface decrease suddenly. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. The direction of loading frequently changes with time, which cause more fatigue damages on structure compared with steady wind condition. Consequently, the wake of the region from wind turbine to downstream distance 1DR is classify as near wake. And the wake of the region behind downstream distance 1.5DR is classify as far wake.