| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 98 === This study is aimed to study the characteristic of a VAWT by Wind Tunnel Experiment. Experiments were first carried out to compare the VAWT working in uniform flow and turbulent flow generated by a grid upstream, and discuss the difference of power generation and performance. The result indicates that turbulent flow has better performance. The main difference occurs at the high wind speed, the power generator is proportional to the power of wind velocity. The exponent obtained under the turbulent flow condition is higher than that under the uniform flow condition, and slightly higher than the cube of wind velocity.
Experiments were made to study the velocity fluctuations produced by the rotating blades. The result indicates the turbulence flow field contained higher fluctuation energy, meanwhile it suppresses the aerodynamic characteristic, such as the vortex shedding of trailing edge. The variation of angle of attack is much smaller during the high tip speed ratio, the time period is much shorter between two blades passes through the same azimuth angle, it causes the vortex shedding of trailing edge have no enough time to develop. The ensemble average results of wind fluctuation around VAWT is highly similar between turbulence flow and uniform flow.
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