本研究使用計算流體力學軟體Fluent，以及使Pro/Engineer、Gambit、 Tecplot進行具擴散器水平軸風車性能研究。 本研究主要分為兩大部分，第一部分為研究各種擴散器之參數，以尋找最佳加速效率之擴散器。其中研究項目包含擴散器(diffuser)與噴嘴(nozzle)之加速效率比較，以及擴散器主體長度、擴散器擴散角度、Flange、Inlet shroud等參數探討。第二部分為確認最適當之擴散器形式後，將擴散器與葉片做結合，計算其葉片所產生之扭矩( torque )與功率係數C_P值。 本研究結果顯示雙葉片與三葉片兩種形式之風車，使用本研究之擴散器形式皆能使風車提升不錯的效率。本研究所使用之小型水平軸風車其葉片之流場為層流，若設成紊流，則葉片上之摩擦阻力過大，使計算所得之扭矩過小，但效率較佳擴散器之流場皆為紊流，如何將這兩者結合在一起有待進一步研究。 This study used the computational fluid dynamics software, Fluent, and computer aided design softwares, Pro/Engineer, Gambit, and Tecplot to study the flow field of horizontal-axis wind turbine, HAWT, with diffusers. This study was divided into two parts. The first part studied the effects of various parameters on the acceleration performance of a diffuser. These parameters included diffuser body length, expansion angle, flange, and inlet shroud. The second part investigated the effects of combining the blades and diffuser. We calculated the torque generated by the blades and the corresponding power coefficient. The results of this study show that the addition of diffuser can improve the efficiency of small HAWTs. We also found that the flow field of small HAWTs is laminar flow. When a turbulent flow was assumed in Fluent, the calculated torque became too small, because the friction drag on the blades was too large. The flow in the diffusers which provide better acceleration is turbulent, but the flow in small HAWTs is laminar. How to combine these two flow fields together needs further study.
