| 摘要: | 本論文以實驗的方法，量測外岐管(external manifold)設計之平板式固態氧化物燃料電池(solid oxide fuel cell, SOFC)短電池堆(short-stack)之流場特性，並分析與改善其流場均勻度。利用自行建立之水力測試平台，配合二維雷射誘導螢光法(laser-induced fluorescence, LIF)以及染液觀測(dye visualization, DV)法，分別獲得電池堆內各層含12個以肋條分隔之矩型流道(rib-channels)的流場影像，再利用Matlab進行影像處理與分析，進而量測計算電池內堆各層間所有流道之速度分佈及其流場均勻度。相互比較後，我們發現由DV與LIF，在雷諾數為25到100範圍內(Re = VDh/??，V為電池堆之平均流速、Dh為單一流道之水力直徑、?為運動黏滯係數(kinematic viscosity)，之數據最大相差約10 %，顯示DV實驗法具備足夠的可靠度來進行相關之流場量測。電池堆進口區(feed header, FH)和出口區(exhaust header, EH)之流向配置為本研究重點，共有五種不同配置，含三種具同向之FH與EH以及兩種反向之FH與EH，分別依序簡述如下：(1) Conventional-type，即同向之FH與EH位於流道之流線方向(streamwise)；(2)Z-type，即同向之FH與EH位於流道之翼展方向(spanwise)；(3)TZ-type，即同向之FH與EH位於流道之橫向方向(transverse)；(4)U-type，即反向之FH與EH位於流道之翼展方向(spanwise)和(5)TU-type，即反向之FH與EH位於流道之橫向方向(transverse)。實驗結果顯示，反向FH與EH之U-type之單電池流場均勻度約為61 % ~ 66 %，電池堆間流率的差異性約為4.8 %，是前述五種設計中較佳的設計。為了更進一步改善U-type之設計，在FH處加裝三角柱型的導流裝置，此種改良型的設計可將單電池的流場均勻度及電池堆流場均勻度各提升至少12 %，達約75%之流場均勻度，為一是種簡單有效提升流場均勻度之設計。在過去有限的文獻中，僅有以數值模擬來討論單電池之流場均勻度，本研究首次以實驗的方法來討論電池堆的流場均勻度，冀望對未來電池堆的發展有所助益。 This thesis investigates experimentally flow distributions in a planar SOFC short-stack using various designs of external manifolds and thus increases flow uniformity of the short-stack. A hydraulic platform combined with laser-induced fluorescence (LIF) and dye visualization (DV) techniques are established to obtain flow fields in the short-stack including three layers, each layer having 12 rib-channels. A Matlab-based code is used to process these flow field images by the binary method and thus corresponding velocities in each of 12 channels for all three different layers can be extracted. Results from both LIF and DV methods are roughly the same with the largest difference up to 10 %, when the channel Reynolds number(Re = VDh/???are within 25~100, where V is the velocity, Dh is the hydraulic diameter of the rib channel, and ? is the kinematic viscosity of fluid. The focus is placed on the effect of different flow directions in both the feed header (FH) and the exhaust header (EH) to flow uniformity of the short-stack. There are five arrangements: (1) The Conventional-type, where both FH and EH are in the same streamwise direction of flow channels; (2) Z-type, where FH and EH are in the same spanwise direction of flow channels; (3) TZ-type, both FH and EH in the same transverse direction of flow channels; (4) U-type, similar to (2) but FH and EH are in opposite directions; (5) TU-type, similar to (3) but FH and EH are in opposite directions. These experimental results show that the fourth design (U-type) has the best flow uniformity among all different designs. In attempt to further improve flow uniformity of the U-type design, a triangular pyramid is placed in the feed header, which can further increase flow uniformity in each layer of the short-stack. Based on the best knowledge of the author, the present study is the first experimental measurement on the flow distributions in the short-stack of planar SOFC and should be useful for numerical simulations. |
