新型单点系泊浮式潮流能装置耦合动力性能研究

Newly designed single-point mooring (SPM) floating tidal power plant, which is moored at a fixed site by the single point mooring system, makes use of the kinetic energy of moving sea water to generate power. Due to the weathercock effect, SPM floating tidal power plant is characterized by minimization of the floating body motion, adaptation for deeper sites, and low cost of installation and station keeping. And the turbine can automatically turn to the direction of the tidal current, therefore this type of floating turbine has higher power efficiency. The effects caused by harsh ocean environments, such as the coupling effects caused by waves and stream profile on floating tidal power plant must be take into account. The turbine moves with the wave-induced motion of the platform, which affects its hydrodynamic performance. And the huge turbines will also have influence on the motion of the floating platform, such as amplitude and frequency. These influence can not only cause the loss of power efficiency, but also threating the safety of the whole system..A combination of developed theoretical analysis, model tests and numerical simulations will be carried out to give fundamental investigations of the hydrodynamic performance of the floating horizontal-axis turbine power plant. The special focus will be given to the loading behavior on floating horizontal-axis marine current turbine (hereinafter known as HAMCT) caused by harsh ocean environments, such as nonlinear-waves, high turbulence intensity, and non-uniform stream profile. The effects of the load on the turbine blade will be discussed in detail. The wake behavior around floating HAMCT will be also discussed. The complex coupling effects among floating platform, HAMCTs, and SPM will be clarified in detail. Based on extended potential theory and blade element method, a developed analytical tool to suggest response amplitude operators (RAOs) of the wave induced motion response of the floating structure considering the coupling effects of HAMCT and mooring system will be set up. Physical experiment, which will be conducted in deep ocean basin and circulating water channel, will also be developed to validate and support the numerical simulations and analytical tool. By conducting the comprehensive fundamental investigations, supports and suggestions can be proposed for further floating horizontal-axis marine current turbine solution design and optimization.

新型单点系泊浮式潮流能发电装置，利用单点系泊系统将水轮机固定于海面上，采用该设计方案，利用风标效应，可有效减小浮体运动幅度，叶轮可自主正对潮流方向，进一步提高获能效率。但表层波浪-海流相互作用会显著影响叶轮载荷、能量输出性能。浮体、叶轮、系泊系统之间的复杂相互作用，不仅会造成叶轮偏离最佳工作状态，导致获能效率下降，也会影响浮体运动响应，威胁系统安全。.本项目研究波流相互作用下，旋转叶轮周围的流场结构与载荷特性。基于势流理论、非定常叶元理论等，建立浮式潮流能装置的水动力性能理论预报方法。叠加随机波浪条件，预报浮体运动响应、叶轮功率输出、系泊系统受力。开发并完善在海洋工程水池、循环水槽中开展浮式潮流能装置的物理模型试验方法。揭示浮体、叶轮、系泊系统之间的复杂相互作用机理，掌握在随机波浪、浮体运动作用下，叶轮进流流速、攻角的变化规律。为浮式潮流能发电装置的一体化优化设计提供科学依据。

潮流能水轮机在实际运营中遇到的海洋环境条件十分复杂，由于受到波浪、不均匀潮流、进流湍流等非定常因素的影响，潮流能叶轮上受到的非定常载荷十分显著，但目前为止，对潮流能叶轮非定常载荷的认识还非常有限，预报手段也很匮乏。.本项目对潮流能水轮机所遇到的非定常载荷问题，特别是波浪诱导载荷问题，综合运用数值模拟、理论分析和模型实验等手段开展研究，提出了1MW，三桨叶基准水平轴潮流能水轮机设计方案。基于叶素-动量模型，结合动态失速模型，动态进流模型，一阶波流耦合模型和单自由度的叶轮转动模型，建立了关于叶片波浪载荷的数值预报方法；在拖曳水池中开展了规则波作用下的叶片波浪载荷实验研究；以规则波下的载荷特征研究为基础，进一步地研究了在随机波浪条件下的叶片载荷响应特征。线性小波陡波浪不会对水下叶轮上的平均载荷造成影响，仅会造成载荷的周期性波动。基于长波假设，给出了准静态的叶轮载荷系数，用于载荷的快速估算。对于随机波浪，响应载荷以一阶波浪诱导载荷为主，同时二阶响应特征可以清晰地在响应曲线中被观察到，虽然二阶载荷的能量占比很小，但是高频载荷的峰值频率可能会与叶片的第一阶结构固有频率重合，可能会导致叶片共振。提出了一种基于半潜式平台的浮式潮流能水轮机概念设计方案，并对浮式潮流能装置的设计思路进行了讨论；基于叶素-动量理论和浮体在波浪上的运动理论，建立了全耦合的浮式潮流能叶轮的载荷与运动预报方法。叶轮载荷在考虑六自由度浮体运动情况下的两个响应峰值，分别由纵荡运动和纵摇运动诱导；浮体运动诱导载荷与波浪直接载荷存在一定的相位关系，在特定情况下，这两种作用可能相互抵消的。浮体的低频慢漂运动虽然会引起较大的位移，但是由于运动周期很长，运动速度较慢，因此对于叶轮载荷影响非常有限。.本项目针对浮式潮流能叶轮非定常载荷等亟待解决的科学问题，开展了大量基础性的研究工作，建立了涵盖叶轮直接波浪载荷预报，叶轮结构响应预报，浮体运动性能预报及系泊系统动力学预报的浮式潮流能水轮机预报理论方法，并开发了相应的数值预报程序，相关研究成果对于水平轴潮流能发电装备的理论与技术进步具有重要的意义。