Numerical Investigation For Dynamics Of Mooring System Of Counter-rotating Marine Current Turbine

With the depletion of traditional fossil energy and the increasing attention to environmental protection,the research and development of new renewable and clean energy has become an important issue in the development of human society.Among many clean energy research directions,ocean energy has large reserves and high cleanliness.With the progress of technology,more and more attention has been paid to it.Among them,marine current energy is an important form of ocean energy.Current power generation technology has gradually been put into commercial development.Specific forms are: stable seawater flow in waterways or straits,or water kinetic energy caused by tides to promote impeller rotation,and then speed-up system to drive generators to generate electricity.Mooring system and blade structure are two important components in the whole system of ocean current generator.Different blade types will be affected by different loads in the current environment,which will produce different power generation effects.Specific mooring systems will also have different dynamic characteristics,and the two feedback each other.Considering the complexity of marine environment and generator structure,it is of great significance to design a suitable mooring system for a specific generator to maintain the stability of the whole generator system and improve the generation efficiency.This paper summarizes the marine current energy industry situation and related research progress of current generator industry,introduces the blade design theory of ocean current turbine and hydrodynamic calculation theory of floating structure,which lays a theoretical foundation for subsequent MCT model design and mooring calculation.Then,based on the introduction of Orcaflex software and the summary of mooring system design specifications,a new type of two-machine current generator and its corresponding tension mooring system are designed.Firstly,the motion performance and mooring tension response of two-machine current generator and single-machine system under the same mooring system conditions are compared to measure the stability of the two systems.Then,in order to consider the influence of blade load on mooring system,the blades with different fineness foils were modeled in Orcaflex,and the numerical simulation results of single hydrofoil/three hydrofoils/nine hydrofoils were compared.Combined with the airfoil parameters optimized by M-BEMT software,the simulation results of the generator using original airfoil blades are compared,and the effects of fine blades and optimized airfoils on the stability of the current generator and the performance of the mooring system are explained.Finally,the positioning performances of different mooring modes for the current turbine system in this study are compared,and the mooring system with better mooring tension and positioning capability is selected.The mooring line tension and platform motion performances under different inflow environments are simulated to provide reference for the future design of current generator array.