| 摘要: | 為解決化石能源衍生之各項問題，各國莫不積極尋求替代能源與解決之道，而氫能作為一種潔淨能源已漸受重視，儲氫合金即是伴隨氫能發展而被看好的新型功能材料，此乃以儲氫合金儲存氫具有體積儲存密度高、安全性高、儲存時間長、無損耗等優點。儲氫合金之儲氫原理是使大量氫氣為金屬吸收後轉變成金屬氫化物形式儲存，氫以固態結合形式儲存於其中，與金屬氫化物間進行可逆反應，當外界施予金屬氫化物熱量時，即可分解為儲氫合金並釋放出氫氣。儲氫合金以粉末之物相形成與作用，應用之際尚需一套具備控制氫氣出入口之密閉性裝填容器（本計畫稱為儲氫合金罐）作為反應平台。當氫原子擴散進入儲氫合金並造成相變態後，會引起晶格膨脹，使儲氫合金晶格體積變大，晶格被撐大甚至變形破裂，此時體積膨脹所產生之應力容易造成儲氫合金粉碎化現象，而罐體將承受罐內氫氣壓力及金屬氫化物體積膨脹之總合作用力，若罐體結構設計不良，即可能產生變形及破損，所以儲氫合金吸氫之體積膨脹應變及對罐體造成之影響為儲氫合金罐結構設計所需考量之首要因子。本研究計畫將以未來極具商業化潛力之高儲氫量鎂鎳合金做為研究對象，針對其應用上所需之高溫儲氫合金罐，於結構設計所應掌握之合金及罐體膨脹行為模式進行深入探討，開發有效之設計分析技術，作為設計高效率、高安全性、低成本儲氫合金罐之用。本研究規劃以三年時間，進行實驗量測和數值模擬分析二部分，從改變吸放氫反應溫度、合金粒徑、循環次數、罐體壁厚、合金裝填量及內裝構型設計等實驗條件著手，瞭解合金體積膨脹率演化、粉末細化堆疊模式及相對應於罐體所產生應力應變之變化情形；同時建立分析模式和演算方法，運用商用有限元素分析（FEA）軟體進行模擬計算和罐體結構設計分析，並依分析結果調製最適化之設計參數製作雛型實體進行實驗驗證，以確立應變及應力模擬分析方法之適用性，並提供未來高溫型儲氫合金罐結構設計和耐久壽命評估之參考。各分年研究重點為：(1)第一年，設計與建構高溫型Mg2Ni 儲氫合金罐吸放氫反應實驗裝置，並進行儲氫合金罐膨脹應變量測與建立膨脹應力分析模式；(2)第二年：建構儲氫合金罐吸放氫反應及罐體膨脹應變之FEA 數值模擬分析模型，改變罐體結構設計，進行模擬分析與實驗量測驗證；(3)第三年：進行儲氫合金罐體結構設計最適化分析及雛型製作驗證，並探討罐體耐久壽命評估模式。 ; Problems related to the use and depletion of fossil fuels have led to significant research effort on alternative and cleaner fuels in which hydrogen is considered one of the most promising candidates. World wide interest in the use of hydrogen has led to much research on its storage and usage. Recently, using metal hydrides for hydrogen storage has been receiving more and more attention thanks to advantageous characteristics such as low operating pressure, high level of safety, and high volumetric density. Metal hydrides can provide a reversible way of storing hydrogen from the gaseous phase within a solid material. One of the concerns with the use of metal hydrides is the container, or called storage vessel. Metal hydrides expand, possibly 20 to 35% in volume, during the hydriding step and create a large stress on the alloy and the storage vessel. The alloy powders tend to fragment into smaller particles through a pulverization mechanism, as a result of this stress. This leads to material movement and segregation in the storage vessel, which generate large internal pressure. Also, as the alloy powders become smaller, there is an increasing tendency for the hydride fines to flow in the gas streams. Therefore, the storage vessel system must accommodate these small particles and the resulting expansion. Strain in the vessel wall should not be overlooked when assessing the practical use of hydrides for hydrogen storage. If uncontrolled, these strains can result in vessel failure. Therefore, it is important to study the structural design requirements for a safe and cost-effective hydride storage vessel. The aim of this proposal is to develop effective analysis tools for assessment of the vessel wall strain variation during the hydriding process and to propose an optimal design of storage vessel structure for use with a high hydrogen-storage-capacity alloy, Mg2Ni, which is a promising candidate for commercial usage. In order to develop a highly efficient and reliable high-temperature metal hydride storage vessel, several issues need to be studied for critical design considerations. Both experimental and theoretical approaches will be implemented in this study. In the experimental program, simple-shaped (pilot size and laboratory scale) storage vessels filled with alloy powders will be designed, fabricated and tested in the first year to investigate the alloy pulverization and expansion characteristics and their influence on vessel wall strain during high-temperature hydriding/dehydriding cycles. Effects of reaction temperature, vessel structural design and dimensions, alloy powder size, alloy powder packing fraction, and cycle number on vessel wall strain variation will be systematically studied for improving design of a storage vessel. In the theoretical program, mathematical models to describe the expansion and pulverization behavior of metal hydrides will be developed and numerically solved in the second year. In particular, an attempt will be made to create in such mathematical models a relationship between the formation of lattice strain during hydrogen absorption in an alloy and the expansion behavior in a porous metal hydride bed. The numerical results will be compared with the experimental data to validate the mathematical models. Based on the experimental and numerical results, an optimal design of a metal hydride storage vessel with reliable structural integrity hopefully can be proposed in the third year to make a prototypical high-temperature hydrogen storage vessel for use with the high hydrogen-storage-capacity Mg2Ni alloy. ; 研究期間 9808 ~ 9907 |
