推拉板式波能轉換器之端板效應

EXPERIMENTAL INVESTIGATIONS ON THE END-PLATE EFFECTS OF FLAP-TYPE WECS

推拉板式（flap-type）波能轉換器（wave energy converter, WEC）為利用本身之板體在波浪衝擊方向（surge）上形成振盪運動，進而驅動功率輸出系統（power take-off）將能量輸出至後端發電機。推拉板前後面流體壓力差所形成的推力造成板體來回振盪，故若增加此流體壓力差即可提高波能捕獲。本文在板體側邊加入不同長度的端板來形成不同大小的低壓跡流（wake）區，嘗試找到端板效應與能量捕獲係數（capture factor, CF）之間的關聯。波浪水槽實驗同步整合高速相機與應變規兩方的瞬時數據以得到板體的CF，並以二維推拉板勢流理論所計算出的理論CF進行正規化。結果顯示當端板長度越長則CF越低，代表端板雖能擴大板體低壓跡流區的範圍，但板體後面繞射（diffraction）效應被端板抑制，反而更多縮減板體前後流體壓力差，造成CF下降。這些結果將可成為日後推拉板板體外形設計之重要依據。 The prime mover of a flap-type wave energy converter (WEC) oscillates to drive the power take-off (PTO) system, converting wave energy into mechanical energy and transmitting it into electricity generation. The pressure difference across the prime mover makes it oscillate. Consequently, increasing this pressure difference makes more capture of wave energy. In this paper, the flap body is installed with end plates of different lengths in order to generate differentsize, low-pressure wake zones to affect the capture factor (CF) of the WEC. Experiments in a wave flume are conducted with synchronized high-speed camera and strain gauges to obtain the WEC's CF normalized with the CF derived from the 2D potential flow theory. The results indicate that the CF decreases with longer end plates, and thus imply that the wave diffraction effect near the rear face of the flap is suppressed to decrease the pressure difference across the flap and the CF. All these results can be used as guidelines for designing the flap body's shape.