Research On The Horizontal Axis Tidal Stream Turbine

Ocean energy is a kind of renewable energy that reserves are huge, developing value is great and is friendly to environment. The tidal current energy is one kind of the most regularly and easily developed. Studying on marine energy is significant to China’s sustainable development, energy saving and emission reduction. The content of this thesis is around the design of blade which is adapted to the low speed, the bidirectional flow and avoided cavitation and so on. It includes theoretical analysis, numerical simulation and experiment. The content is as follws:(1) Study the design theory of turbine. It is the first time to apply the Schmitz to design and analyz the tidal stream turbine. It is different from the traditional BEM theory and Glauert theory; it is more convenient to obtain the optimal design in working condition.(2)Study the relationship between the parameters of turbine including chord length, pitch angle, solidity and the performance of turbine including the startup ablity and power cofficioent. Do the reparation for the experiment.(3)Design many kinds of model to verify the consequence of theory analysis. Seven kinds of blade and fifteen kinds of turbine are designed for experiments.(4)Research the pressure distribution, streamline behind the turbine and cavatitation of the blade through the towing experiment of 2.5k W turbine and consequence of CFD. Some measures are provided to prevent cavitation.The conclusion mainly contains:(1) Chord length distribution had a great impact on the start-up ability of turbine. The relationship between the start-up ability of turbine and the chord-length distribution is studied through theoretical analysis and model test. Researches show that the start-up performance of twisted blade is improved greatly by changing chord length distribution. The start-up performance of straight blade has little relationship with the chord length distribution.(2) The start-up torque and the efficiency of the turbine are depended on the pitch angle of the blade. For the straight blade, enlarging blade solidity can increase the start-up torque; increasing the pitch angle will increase the starting torque also.(3) In order to adapt to the reciprocating flow, a novel type of passive self-variable pitch blade is designed in this thesis and it is a feasible design scheme proved by experiments.(4) Pressure coefficient distribution of blade is predicted by Xfoil and Fluent in the initial stage of blade design. This method is very effective verified by the towing experiment. To prevent cavitation, appropriate pitch angle should be selected, solidity should be increased and the tip speed ratio should be decreased.The research on the horizontal axis turbine by theory, experiment and numerical simulation, conclusions can be applied to design the blade which is adapted to China’s low tidal current velocity and the bidirectional flow. Also measurements are proposed to avoid the cavitation. In addition, the boundary effect in test is modified through Fluent.