The Research Of The Multi-bar Type Vertical-axis Variable-pitch Turbine For Tidal Current Energy Conversion

In recent years, conventional energy is reducing sharply on the earth and theenvironmental damage is growing. Ocean energy has been extensively researched to ease thepressure on energy and the damage to our environment. One of these green energy transferequipments is ocean current turbine which is very popular. Vertical-axis tidal current turbinecan work well without the influence of the direction of flow, and is of catholic concern for itsgood mechanical properties. Variable-pitch mechanism determines the turbine’s ability ofself-start and energy capture efficiency as the key of a vertical-axis tidal current turbine.Vertical-axis tidal current turbine has been deeply studied to develop a high energycapture efficiency variable-pitch mechanism. Main steps include mechanical design ofvariable-pitch mechanism, hydrodynamics analysis, kinematics and dynamic analysis, modalanalysis.Based on the analysis of variable-pitch theory, the multi-bar type mechanism on the baseof spatial lever principle is taken as the basic plan. Then the main parts of variable-pitchmechanism are designed in detail and its degree of freedom is analyzed. Then the wholedesign of the variable-pitch mechanism is finished and be modeled with PRO/E software.After modeling the variable-pitch mechanism, the analysis of hydrodynamics is done.Use CFD method to analyze the stress situation during the rotation of the turbine blades indifferent eccentricities with FLUENT software. Get the torque of the turbine for the dynamicanalysis of the variable-pitch mechanism later. Also, get the velocity and pressure distributingfigures for the flow field around the blades.To prove the rationality and correctness of the variable-pitch mechanism, use PRO/Esoftware to do motion simulation and compare the simulation result with theoretical result.Use power bond graph method to analyze the dynamic characters of the variable-pitchmechanism, the result shows that the variable-pitch turbine has higher energy captureefficiency.Modal analysis of three key parts of the variable-pitch mechanism is done to get theanterior10ranks of natural frequencies and corresponding mode shapes of these three keyparts. It shows that the resonance phenomenon would not happen between these three keyparts and the tidal current load or impeller load by comparing their frequencies.