| Summary: | 碩士 === 國立虎尾科技大學 === 航空與電子科技研究所 === 102 === The vertical axis wind turbines have an advantage over the horizontal axis wind turbines such as easy installation, less susceptibility to wind shift and low noise. They are very suitable to be installed in urban and suburban region. The vertical axis-wind turbine has great potential for promoting green energy in residential life. Since the stall angle can be enhanced by increasing the roughness appropriately on blade surface. This study integrated the SST k-ω turbulence module into the computational fluid finite volume method to explore the aerodynamic characteristic of a three blade vertical axis wind turbine (VAWT) in different tip speed ratio and different roughness height (RH). It’s intended to find the optimal roughness height, to increase the efficiency of wind energy capture, and enhance the performance of the wind turbines.
In the 2D VAWT ,increase λ the maximum average torque coefficient (Cq) is occurred at λ=2.5; The Cq is increase with λ as λ<2.5, and then decrease with λ as λ>2.5. The average Cq are larger than the smooth blade case as λ≦2. The average Cq are lower than the smooth blade case as λ≧2.5. Compare the smooth blade case, adding roughness on top and bottom surface of blade, the best roughness height is at RH=1x10-3m obtained average Cq enhance 67.86%、25.55% and 20.38% as λ=1、1.5 and 2 respectively. Compare the smooth blade case, adding roughness on top surface of blade, the best roughness height is at RH=1x10-4m obtained average Cq enhance 76.48%、49.11% and 26.60% as λ=1、1.5 and 2 respectively. Compare the smooth blade case, adding roughness RH=1x10-4m on front surface of blade, obtained average Cqenhance 60.59%、40.73% and 23.24% as λ=1、1.5 and 2 respectively.
In the 3D VAWT ,increase λ the maximum average CQ is occurred at λ=2; The CQ is increase with λ as λ<2, and then decrease with λ as λ>2. The average CQ are larger than the smooth blade case as λ≦1.5. The average CQ are lower than the smooth blade case as λ≧2. Compare the smooth blade case, adding roughness on top and bottom surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 39.40% as λ=0.5. The best roughness height is at RH=5x10-4m obtained average CQ enhance 48.90% and 10.20% as λ=1.5 and 2 respectively. Compare the smooth blade case, adding roughness on top surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance17.75%、30.88% and 30.76% as λ=0.5、1 and 1.5 respectively. Compare the smooth blade case, adding roughness on front 1/3 c surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 41.87%、59.93% and 19.97% as λ=0.5、1 and 1.5 respectively. Compare the smooth blade case, adding roughness on top front 1/3 c surface of blade, the best roughness height is at RH=1x10-3m obtained average CQ enhance 35.42% and 3.79% as λ=1.5 and 2 respectively.
In each of these cases, adding roughness RH=1x10-3m on top front 1/3 c surface of blade in VAWT is the best, the maximum average CQ is occurred at λ=2, but also improve performance.
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