實船螺槳空化觀測系統之規劃與設計

Development and Design for Full-Scale Cavitation Imaging System

船舶螺槳之設計目標不外乎在滿足船速要求下，螺槳出力能達到高效率表現且避免發生空化現象。螺槳的測試常常都是在控制良好的實驗室環境中進行，以縮小尺寸的物理模型來觀測，因此測試結果會受制於未知的尺度律，而無法真正呈現實尺寸的狀況；這也是實船空化觀測愈來愈受到重視的原因。本論文先參考公開文獻中之實船空化觀測技術的案例，藉以列出系統發展之重點項目，包括觀測窗位置之選擇、觀測窗之設計、光源與拍攝系統之組建等等。發展過程中包括分析與設計觀測窗以滿足在靜態與動態負荷下之結構強度需求、設計燈罩以改善LED光源之照度與測試選擇可遠端控制焦距、快門、光圈之工業用相機做為影像拍攝系統之主體。最後於水槽中進行水下拍攝情境模擬，而拍攝結果合理地驗證了本系統之適用性。 It is the design goal for marine propellers to deliver highly efficient performances while remaining free of cavitation. Toexamine the performance of a propeller, its down-sized, physical model is usually used for the test in a well-controlledlaboratory environment. Therefore, the test result shall be governed by some unknown scaling law and cannot truly reflect thefull-scale situation. This fact also serves as the reason why the imaging of full-scale cavitation is receiving more and moreattentions. This paper first examines previous cases of full-scale cavitation imaging in open literatures, resulting in a list of keyitems for the system development that includes the position choices and the design of imaging windows, and the construction oflighting and imaging system. In the development process, we analyze and design imaging windows to meet the structuralstrength requirements under static and dynamic loadings, design a focusing cover cap installed in front of a LED light source toimprove its luminance, and test an industrial camera whose focal length, shutter speed, and aperture are remotely-controllablefor building the major block of the imaging system. Finally, the under-water imaging scenario is simulated in a water tank andthe results reasonably verify the suitability of the system.