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Research On Vortex-induced Swing Characteristics And Energy Harvesting Efficiency Of Energy Harvesting Column Of Bladeless Wind Turbine

Posted on:2021-01-10Degree:MasterType:Thesis
Country:ChinaCandidate:X H WuFull Text:PDF
GTID:2392330614953727Subject:Power Engineering
Abstract/Summary:PDF Full Text Request
The bladeless wind turbine captures wind energy through the vortex-induced oscillation of its energy harvesting column,and converts it into usable energy such as electrical energy through an energy conversion device.In order to investigate the vorticity induced oscillation characteristics and energy capture efficiency of the bladeless wind turbine energy capture column,based on the CFD/RBD coupling method,numerical simulation studies have been carried out on cylindrical energy harvesting columns,frustum energy harvesting columns and bladeless wind turbine variable natural frequency systems.The main research work of this paper is as follows:(1)Using the controlled variable method,three numerical calculation and comparison analysis schemes are designed for the influence parameters of bladeless wind turbines.Within the range of the studied damping ratio(0.04???0.1)and mass ratio(10?m~*?40),the peak swing of vortex-induced oscillation and the maximum energy capture efficiency both occur at the position of frequency ratio;reducing the damping ratio and mass ratio of the system can improve the peak swing and maximum energy capture efficiency,while increasing the natural frequency of the system can improve the peak swing and maximum energy capture efficiency of the capture column;the peak swing of the cylinder is related to the Reynolds number,the larger the Reynolds number is,the greater the peak swing is;In the process of vortex-induced oscillation,varying degrees of oblique vortex shedding occurs with the change of the height of the cylinder,which has a certain influence on the"locking"phenomenon of the vortex-induced oscillation frequency.(2)Under the condition of keeping the bottom diameter and wall thickness the same,the fluid-structure interaction study was carried out on energy harvesting columns with different taper ratios(?=0?0.08).The peak swing amplitude of the energy harvesting column is relatively stable with the increase of the taper ratio and then gradually increases,while the energy capture efficiency first decreases and then increases with the increase of the taper ratio;the locking region of the main frequency of the horizontal swing of the trapping column widens with the increase of the taper ratio,and the pendulum amplitude increases only when the main frequency component is close to the natural frequency of the system;at the peak swing amplitude,the phase difference between the swing angle of the energy harvesting column and the lift moment is around 90°;under the frequency-locked wind speed,the change of the trailing vortex shedding frequency of the frustum-shaped energy harvesting column with the height direction is smaller than that in the fixed and non-locked state.(3)The natural frequency of the non-linear restoring moment energy harvesting system is theoretically analyzed,and the numerical simulation of different energy harvesting systems is carried out.The slope of the nonlinear restoring torque energy harvesting system function controls the natural frequency of the system,and the greater the degree of nonlinearity of the restoring torque,the faster the change rate of the natural frequency of the system;when the initial value of the natural frequency of the variable natural frequency system is less than the fixed natural frequency system,the peak swing of the energy harvesting column and the energy capture efficiency decrease with the increase of the non-linearity of the restoring torque,and the corresponding wind speed moves in the direction of smaller Reynolds number;in the variable natural frequency energy harvesting system,the second frequency component bandwidth of the energy capture column increases,and selecting an appropriate variable natural frequency system can increase the lock interval of the main frequency and the high swing interval of the cylinder.This paper studies the vortex-induced oscillation characteristics and energy capture efficiency of the energy harvesting column of bladeless wind turbines,which can provide guidance for the structural design of the energy harvesting column and the parameter design of the bladeless wind turbine system.
Keywords/Search Tags:bladeless wind turbine, vortex-induced oscillation, energy harvesting efficiency, mass ratio, damping ratio, variable natural frequency
PDF Full Text Request
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