- 學位論文
數值方法研析Gurney式襟翼應用於葉片在三維垂直軸風力機氣動力特性與性能提升之研究
Numerical Study on the Aerodynamic Characteristics and Performance Enhancement of the Gurney Flap Applied on Blade in the Vertical Axis Wind Turbine
摘要
垂直軸風力機具有較水平軸風力機不受風向轉變影響、架設容易與噪音小等優點，且可安裝於市區、市郊的建築使用，在提倡綠色能源於住宅生活的前提下，垂直軸式風力機成為極具發展潛力的項目。葉片加裝Gurney 式襟翼會在襟翼的後方產生渦流結構，使得機翼附近流場改變。為了滿足類似Kutta Condition的效用，使得整個機翼的停滯點向下遊延伸後，將造成類似機翼翼弦增長或弦弧增加的效應，使得機翼的升力增加。故本文以數值方法搭配SST k-ω紊流模組研析風機葉片加裝Gurney式襟翼在不同尖速比(TSR)下之三葉片垂直軸風機氣動力性能，並探討三種安裝型式(Upward、T-type、Downward)及襟翼高度(H)對垂直軸風力機效率影響，找出各種尖速比下安裝Gurney式襟翼之最佳襟翼高度，來提升小型垂直軸風力機性能，進而增加風能擷取效率，提高風力機的發電效率，以達成提升性能的目標。 由二維三葉片風機結果顯示，Gurney式襟翼高度以在H/c≦2%c時表現較佳，在大部分安裝型式以及TSR中有正向的效果，隨著TSR的增加，平均扭力係數最大值會發生在TSR=2.5時；平均扭力係數在TSR<2.5時呈增加趨勢。T-type型式在TSR=1和TSR=1.5時表現較佳，TSR≧1.5後增加的效能較少。Upward型式在三種安裝型式中表現較差，僅在TSR=1.5有較佳的平均扭力係數。Downward型式相較於其他兩種安裝型式以TSR=2時平均扭力係數最佳，在TSR=1.5時表現最差，其餘皆僅次於T-type型式。在我們的探討範圍內(TSR=1~TSR=2.5之間，Gurney式襟翼高度在1~4% c之間)平均扭力係數最好約可提升88.5%。在三維風機部分，Gurney式襟翼高度以在H/c≦2%c時表現較佳，在大部分安裝型式以及TSR中有正向的效果，平均扭力係數最大值會發生在TSR=2時；平均扭力係數在TSR<2時呈增加趨勢。在三種安裝型式中，以T-type型式表現最佳，在TSR=1和TSR=1.5時平均扭力係數增益值較高，TSR≧2後增加的效能較少。Upward型式在TSR=1和TSR=1.5以及襟翼高度為1%c和2%c時有正向的表現，其中在TSR=1.5有較佳的平均扭矩係數。Downward型式在大部分的條件下皆無有效提升效能，其中在TSR=1以及flap高度≦2%c時有正向的表現；在我們的探討範圍內三維風機平均力矩係數最好約可提升28.6%。
並列摘要
The vertical axis wind turbines(VAWT) 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 VAWT has great potential for promoting green energy in residential life. This study intends to investigate the flow structure and aerodynamic characteristics by installing the Gurney flap on the turbine blades of a three straight-blades VAWT system. The efforts of this study are devoted to the influences of the installation types (Upward, Downward, T-type), height of the flap, and tip speed ratio (TSR) on the torque and efficiency of the wind turbine. In the 2D VAWT, Gurney flap with height H/c≦2% has better performance improvement in most case of different TSR and installation types. In the three installation types, T-type is the best installation type. The maximum average Cq is occurred at TSR=2.5; The Cq is increase with TSR as TSR<2.5, and then decrease as TSR>2.5. The performance of T-type is good when TSR=1 and TSR=1.5. Upward is better only at TSR=1.5. Upward type is the worst of the three installation types. The best performance of Upward is occurred when TSR=1.5. The performance of Downward type is better than others at TSR=2 and worst in TSR=1.5. Within the scope of our investigation, the best average torque coefficient can improve about 88.5%. (TSR=1~TSR=2.5, Gurney-flap height 1~4%c) In the 3D VAWT, Gurney flap with height H/c≦2% has better performance improvement in most case of different TSR and installation types. In the three installation types, T-type is the best installation type. The maximum average CQ is occurred at TSR=2; The CQ is increase with TSR as TSR<2, and then decrease as TSR>2. The performance of T-type is good when TSR=1 and TSR=1.5.The performance is going down when TSR≧2. Upward has optimal performances occurred only when TSR=1 and TSR=1.5 with flap height is 1%c and 2%c. The best performance of Upward is occurred when TSR=1.5. Downward is not going well in 3D cases. It has better performances occurred only when TSR=1 and flap height ≦2%c. Within the scope of our investigation, the maximum average torque coefficient enhancement of the wind turbine for the situations with and without Gurney flap on the blades is higher as TSR=1.5 and can be up to 28.6% for T-type flap with 4% c height.