高液壓成型機台之研發與其在燃料電池上之應用

Abstract

近年來隨著綠能科技崛起以及攜帶型3C產品需求增加，可攜式質子交換膜燃料電池逐漸受到矚目。而金屬材質的雙極板由於其具有低成本、優異的熱、電與機械性質以及能夠有較薄之厚度(0.1-0.5 mm)，因而成為了可攜式燃料電池中的主要零件。然而，以現有之成形技術仍無法在金屬薄板上有效成形出符合實際燃料電池所需具有高深寬比的流道結構。 本研究利用自行研發之高液壓成形機台，藉由提升成形製程中之成形壓力來達到提升微流道深寬比之目的。此設計包含了三個部分：一個能夠產生二段增壓的機械結構、一個能夠乘載高液壓的高壓承載筒，以及能夠將液壓密封的高壓密封元件。透過此研究，建立了一套完整的高液壓成形技術，並在現階段應用於可攜式燃料電池之金屬雙極板的製作上。 由實際實驗可知，此研發之高液壓成形機台不論在製程控制或是成形試片的重現性上均是合理且可接受的。在施加高達250 MPa之成形壓力下，其微流道之深寬比能夠達到0.392，比傳統液壓成形所能得到之深寬比(0.31)提升了26.5%。後續，再經過有限元素以及最佳化分析後，將可更有效率的利用此高液壓成形技術以獲得此成形機台的最佳成形能力，使成形試片上的微流道深寬比再提升4.8%。

Portable proton exchange membrane fuel cells (PEMFCs) have received considerable attention recently because of the suitable material of the development of 3C production processes and green energy techniques. For the key component of portable PEMFCs, bipolar plates, metals such as stainless steel are becoming popular because of their excellent mechanical, electrical, and thermal properties, as well as a low degree of thickness (0.1–0.5 mm). However, current forming techniques cannot efficiently fabricate micro-flow-channels with a high aspect ratio on thin metallic blanks to satisfy the practical demands on portable fuel cells. This study presents the development of a high-pressure hydroforming technique and explains the design and construction of an experimental high-pressure hydroforming apparatus. The apparatus is composed of a two-stage pressure-increase structure to provide high fluid pressure, a high-pressure container and high-pressure seals to maintain and seal the high fluid pressure. Conclusively, this research develops a complete high-pressure hydroforming technique and be applied in forming metallic bipolar plates for portable PEMFCs. The results of our investigation indicate that the process control for the developed apparatus and the repeatability for hydroformed specimens are reasonably acceptable. The aspect ratio of micro-flow channels formed using this apparatus can achieve 0.392 when a working pressure of 250 MPa is applied. Compared with the maximum channel aspect ratio of 0.31 formed using the traditional hydroforming process, the channel aspect ratio formed using the new technique and device is 26.5% higher. Furthermore, finite element and optimization analyses can be performed to boost the forming capability of the developed technique. Consequently, the aspect ratio of formed micro-flow channels can be further increased by 4.8%.