- 學位論文
單一極端海況下IEA 15-MW浮動式風機的繫泊系統之設計與分析
Design and analysis of mooring system for the IEA 15-MW floating offshore wind turbine for an extreme condition
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摘要
本研究旨在於系統化地設計IEA 15 MW浮動式風機 (floating offshore wind turbine, FOWT) 的繫泊系統，而後在完成繫泊系統設計後探討浮台運動和繫泊索軸向力響應之行為。在繫泊系統設計階段，利用了兩個檢查點以評估最初的21個繫泊系統模型。首先，第一檢查點進行1小時50年的極端事件模擬，用於快速消除超過其自身容許張力的不適合模型。在隨後的第二檢查點的50 年極端事件之模擬結果，則基於法國驗船協會 (Bureau Veritas, BV) 的NR-493設計規範，奠立了三項設計標準，分別檢驗與確保了繫泊索的強度、浮台的水平位移和錨碇點的垂直位移。透過本系統化設計，揀選出了僅有兩種繫泊系統模型能夠承受得住50年的極端事件，即M2L445d185 和 M2L445d162，其中M2L445d185 能夠在較低的繫泊索軸向力響應和浮台水平位移下承受該極端事件。 在設計階段中，造成最大軸向力響應增加的因素為較短的繫泊索長度、較重的繫泊錨鏈以及採用無冗餘繫泊模式。此外，從自由衰減模擬之結果可以得到。造成在縱移 (surge)、橫移 (sway)、平擺 (yaw) 方向上之浮台的整體系統運動的自然頻率增加的方式有較大的錨鍊直徑、較短的繫泊索長度、採用有冗餘餘繫泊系統以及水深的減少。 在分析階段中，由頻譜特徵值分析結果了解到，浮台運動以波浪尖峰頻率和各方向上的自然頻率為主，而與此同時，繫泊纜軸向力響應則與以一階波浪負荷和二階低頻波浪負荷為主。 透過本研究的系統化設計，海洋工程師們能夠快速縮小繫泊系統設計中與繫泊相關的變數範圍。其未來的發展可以拓展應用到半自動之目標導向的繫泊系統設計。
並列摘要
The objectives of this study were to systematically design the mooring system of the IEA 15-MW floating offshore wind turbine (FOWT) and then analyze the behaviors of the floater motions and the mooring line axial force responses. During the mooring system design phase, two checkpoints were carried out to assess the initial 21 mooring system models. First, checkpoint 1 with a 1-hr 50-yr extreme event simulation was to find out and quickly eliminate the improper models that exceeded their own allowable tensions. The subsequent checkpoint 2 with 3-hr extreme event simulations would ensure the strength of the mooring line, the horizontal displacement of the buoy and the vertical displacement of the anchor point in accordance with the Bureau Veritas (BV)’s NR-493 regulation. Through this systematic design, only two mooring system models could withstand the 50-yr extreme event, viz., M2L445d185 and M2L445d162. In addition, M2L445d185 was able to withstand this extreme event under lower mooring line axial forces and floater horizontal offsets. At the design phase, the factors to increase the maximum axial force responses was because of shorter mooring line lengths, heavier mooring chain, and the adoption of non-redundant mooring patterns. In addition, through free decay tests, the natural frequencies of floater motions in surge, sway, and yaw were particularly related to the configuration of mooring system models, such as larger chain diameter, shorter mooring line length, adoption of redundant mooring system, and reduced water depths. At the analysis phase, the results of spectral eigenvalue analysis showed that the floater motions were dominated by the wave peak frequency and each DoF-natural frequency, and meanwhile the mooring line axial force responses were dominated by the first-order wave loads and the second-order low frequency wave loads. Inspired from this systematic design procedure of this study, ocean engineers could quickly narrow down the scope of mooring-related parameters for mooring system design. The future development could be extended to the semiautomatic target-oriented mooring system design.
參考文獻
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