Analysis On Key Components Of The Horizontal-axis Tidal Current Turbines' Variable Pitch Mechanism

Tidal current energy is a new renewable and no pollution energy source which is abundant and has high energy density.The tidal energy generation turbine is a conversion device of energy,the relevant research is expanded in recent years,horizontal-axis turbines are more common application form.The main research directions in the field of tidal energy generation include:Ensure the reliability and stability of generating units,enhance the viability of the harsh environment and improve energy utilization.The research results of traditional fixed-blade horizontal axis turbine have been very rich,but the shortcomings of poor starting performance and lower energy utilization limit its development.The Analysis and research of the variable pitch of a horizontal axis direct drive turbine are presented in this paper,variable pitch technology can be adapted to different flow rates and improve energy efficiency.The model is meshed in structured grid by using Pre-processing software ICEM,hydrodynamic performances under different speed and flow turbine are analyzed by using professional fluid analysis software CFX.The main design parameters such as turbine load,power factor,torque coefficient are calculated.The blade load of turbine is analyzed based on blade element theory,dynamics,and other related knowledge,which provide supported dates for the subsequent structure analysis of pitch.According to the actual working conditions and design requirements,the pitch mechanism of a 100kW tidal energy generation turbine is presented in this paper,which is mainly composed of pitch motor,reducer,wheel bearings and supporting connections.The turbine energy conversion principles are analyzed by using momentum theory and related hydrodynamic theory,and the theoretical maximum of energy efficiency is calculated.Installation of the blade and limit device are described in detail,based on the principle of pitch and pitch characteristics,and combined with the structure of the turbine hub and blades of this study.After the necessary simplification of the bolted structure,the contact problem finite element analysis model is establish based on nonlinear contact analysis theory and the role of contact relationship and bolt preload between parts is considered.The maximum deformation,stress,strain and pressure distribution of connecting structure are calculated.The maximum force of the bolt satisfies the design requirements.The pitch gear dynamics are strength analyzed by using the finite element method by the process of observation and analysis gear stress distribution.The feasibility of the finite element method and the reliability of the selected gear are verified by observing and analyzing the gear meshing process stress distribution.The parameters of gear and the life of the pitch bearing are calculated.The wet mode of turbine in water is analyzed by using the finite element method for fluid-structure interaction,the anterior 10 natural frequencies and corresponding mode shapes of dry and wet modal are calculated.The comparison results of dry-wet mode prove that,the fluid surrounding the turbine lower the natural frequency and there is no resonance phenomenon for this turbine,laid a foundation for further analysis and research.Dynamic response analysis is carried out under the load of unbalanced quality to further verify the reasonableness of the structure.