The Studies of Shock Wave Structure of the Release from High Pressure Hydrogen

[[abstract]]近年受到全球溫室效應與能源議題的影響，各國迅速發展新替代能源，以取代現有的石化燃料，例如:太陽能、生質能、氫能等；其中氫氣為一清潔能源載體，具有能源轉換效率高、低汙染及完全不產生溫室效應等優點，廣泛應用在石化、半導體、光電等產業，但氫氣之爆炸界線很寬廣(4%~75%)，是為一高危害的易燃性氣體。氫氣雖不是自燃性氣體，但其在某特定高壓外洩的條件下卻會引燃，目前在各文獻其造成引燃之機制與條件尚未明確，但推論是因外洩氫氣所產生震波，使接觸面的溫度上升而造成引燃。 本研究設計一套氫氣外洩控制與量測系統，針對特定壓力在矩形測試管徑進行外洩測試，並使用高壓電磁閥快速開關，以有助於控制外洩條件的一致性，且利用高速攝影機與陰影法觀察高壓氫氣外洩時在管內與管外之震波的結構。 測試結果發現高壓氫氣噴射於特定排放的管徑與壓力時，在最小矩形的出口管徑中，發現在出口端產生震波傳遞現象，其震波與壓力明顯有關，顯示管徑和壓力皆與能否產生震波具有相關性，此研究所觀察的氫氣震波條件，對於爾後在發展氫氣產業的設計與操作技術上有所助益，進一步預防氫氣造成的意外事故。[[abstract]]In recent year the development of alternative energy such as solar biomass hydrogen etc has been growing significantly in each country owing to the increasing global warning and energy issues Among these hydrogen is a clean energy carrier with high energy-conversion efficiency low pollution and producing no greenhouse effect It is also widely used in petrochemical semiconductor optoelectronics and other industries However hydrogen has a very wide explosion limit (4% to 75%) and is a highly hazardous flammable gas Although hydrogen is not a pyrophoric gas it may ignite under certain high-pressure release conditions Current literatures on the ignition mechanism and condition remain unclear It is generally suggested that it is shock wave generated from the release that heated the air/hydrogen interface caused the ignition This study designed a hydrogen release control and measurement system to test the release in a rectangular duct at specific pressures A high pressure solenoid valve is used to control the release to ensure a consistent release A high-speed video camera and a shadowgraph system are used to visualize the shock wave structure inside and outside the test duct The results showed that shock wave propagation was observed for the high-pressure hydrogen release tests in the smallest duct diameter and some particular pressure but not in larger duct diameter tests It is clear that shock waves generation is strongly related to the duct diameter and the pressure This result should help to better understand the ignition mechanism benefit the design and operation in hydrogen related industries and prevent future incident from occurrin