Study On The Key Technologies Of Horizontal Axis Marine Current Turbine's Mechanics

With the development of economy and society, requirement for energy resource increases continuously. At the same time, people face serious environment problem, so how to realize the sustainable development of society and economy is an important issue which all countries of the world are facing. As a kind of ocean energy, ocean current energy is an abundant and renewable energy. But the harsh environment is disadvantageous for ocean energy exploitation, which induces the difficulties of turbines design, mechanical structures design and power output stability. The researches on the horizontal axis marine current turbine's feasibility in energy exploitation, and how to improve the viability and reliability of the equipment, and how to realize the stability of power output and the maximum of the captured energy, are the key technologies in the research of ocean current energy exploitation.Several key technologies need to be solved for the horizontal axis marine current turbine, which is an integrated innovative system using ocean current kinetic energy to generate electricity. Aiming at these items, this paper has done systematical research on it by theory analysis, simulation methods and field tests. At first the momentum theory is used for the analysis of the turbine's maximum power capture, and then hydrokinetic theory and numerical simulation methods are used for the analysis of airfoil hydrodynamic characteristic and its design. The semi-direct-driven unit that adopted three-split-power three-mergeing-power and the unit using hydraulic power transmission are mainly studied in the research of the power transmission system. Two kinds of transmission methods are analyzed by comparing the workshop test results, field test results of semi-direct-driven unit with the simulation results of hydraulic unit. The maximum of the captured power and the stability of the output power are key technologies of equipment design. After the electrical method is introdued briefly, the hydraulic power transmission system which adopts volumn timing is focused on the power stability and maximum power capture, and the results show hydraulic power transmission system that owns accumulator and volumn timing can well realize the power stability and maximum power capture. At last the pitch-adjusted system and control arithmetic are tested on the semi-phisical simulation test rig, and the result shows the pitch-adjusted system can stabilize the power when the current velocity exceeds the rated velocity.Besides, the corrosion resistance, sealing system, brake system, electrical devices and the field fixing of the equipment are also considered. The main research contents of the paper are as follows:In chapter 1, the background, targets and significance of the marine current turbine research are given. Then the research status of the MCT is introduced. At last, the issues to be solved are presented.In chapter 2, the momentum theory, hydrodynamic theory and angular momentum theory are utilized to analyze the maximum power capture of the MCT's turbine. The airfoil forces are analyzed using Blade element theory. At last the cavatation theory and the MCT's working principle and its structure are introduced.In chapter 3, the key technologies of the MCT are analyzed. The blade's hydrodynamic and configurations are researched through theory analysis and numerical simulation. Blade pitch-adjusted structure is calculated and designed. The semi-direct-driven transmission system is researched and the fluid power transmission system is introduced briefly. At last, the electric system and other accessories are researched.In chapter 4, researches are focused on the hydraulic power transmission system including its design and components selection. Then the system is modeled and simulated in the AMESim and Matlab/Simulink, and the results are compared with those of the MCT using semi-direct-driven unit.In chapter 5, the variable speed theory and blade pitch-controlled theory for MCT are introduced. The electric method and hydraulic method are researched for the realization of power maximum, and special attentions are given to the hydraulic volumn timing which can realize the maximum power capture. At last, the pitch-controlled way and algorithm for power stability is researched in the semi-physical simulation test-bed.In chapter 6, the field tests of the 5 kW prototypes are introduced, and the results are analyzed. Then the 25 kW prototype's workshop test and field test are carried on, and according to the test results, the device's efficiency and blade performances are analyzed.In chapter 7, this paper's research work and the outcomes are generalized, and the further investigations on MCT are pointed out.