離心式高轉速鼓風機設計與數值模擬研究

Abstract

鼓風機為燃料電池發電系統中重要零組件。鼓風機除負責提供燃料電池中陰極氣體之供應外，在燃料電池系統內耗上亦佔有最大之比例，對於系統效率影響極大。因此，如何設計出高靜壓、高效率、低耗能、體積小的專用鼓風機，成為燃料電池系統發展上的重要課題。 本研究針對燃料電池系統之高轉速鼓風機提出一套有效設計方法，除歸納相關經驗公式進行風機雛形設計外，亦可藉由CFD軟體的輔助觀察內部流場變化，提出改良策略進行討論。 根據分析歸納出的結果，可發現於設計流量（0.5cmm）下，增加葉片弦長、對渦殼進行縮小將可加強引導氣體、減緩壓力梯度變化，可有效提升靜壓與風機效率。增加葉片數目將可使葉輪出口逆流減少，改善出口氣流流動。縮小葉輪與渦殼厚度將大幅降低耗能、使效率獲得最大之提升。 掌握這些設計策略針對5kW燃料電池進行設計改良之初步結果擁有良好性能表現，於設計流量下，將可提供12,486Pa之高靜壓，效率可達64.2％，而耗能卻僅約需219W。此性能可媲美AMETEK產品之優良性能，證實本研究之設計方法將可有效設計出高性能之高速鼓風機。

Blowers play key roles in the operation of fuel cells system. Fuel cells rely on blowers to supply air to the cathode in the stack and the blower efficiency is a critical factor in maximizing the overall efficiency of a system. For these reason, how to find out the blower which can provide high pressure, high efficiency, low power consumption and minimum volume is vitally important in design of fuel cells system. In this study, we create the effective design method of high speed blower for fuel cells system. We use the empirical formulas to make up prototype. Then we can observe the inner flow change in blower with CFD software and put forward some strategies to improve the problem found in inner flow region. According to analysis, there are some strategies to promote blower efficiency at the design point flow rate（0.5cmm）. To increase length of blades and reduce the volume of casing will promote the air be better guided, and ease the pressure change of air. To increase the number of blades will reduce the reverse flow near the outlet of impeller. They all will results in the rise of static pressure and performance. Finally, to decrease the height of impeller and casing will reduce electric power costed and result in the substantial rise of performance. By using these strategies, we design the grate shape of 5kW fuel cells blower which can provide 12,486Pa in static pressure, 64.2% in efficiency, and only requires about 219W at the design point flow rate. It is nearly as good as the performance of AMETEK fuel cells blower products. The design method created in this study is proved to be useful to design the high performance, high speed blower.