Study On Energy Conversion Characteristics Of Magnetic Nonlinear Wave Energy Converter

Wave energy is one of the most abundant renewable and pollution-free energy sources in the ocean,which has great potential to be developed and utilized.But the development of wave energy power generation technology is limited due to the lower capture efficiency of wave energy conversion device.In this paper,the point absorption wave energy conversion device is choosen as the research object.For the lower capture efficiency of the linear point absorption wave energy conversion device,and narrow frequency band of wave energy capture,so the adaptability of the device is poor.Therefore,two kinds of magnetic bistable mechanisms are proposed that can be used to the point absorption type wave energy conversion device,and then the dynamic model and energy capture characteristics of the point absorption type magnetic bistable wave energy conversion device is studied under different wave conditions.Numerical simulation results show that the two kinds of magnetic bistable mechanisms can effectively improve the capture efficiency and significantly broaden frequency band of the point absorper wave energy conversion device as well.The main research contents are as follows:Firstly,the research background and research status of wave energy conversion device at home and abroad are introduced.Based on the linear wave theory,the mathematic models of the regular wave and irregular wave are established,the nonlinear dynamic model in time domain of the point absorption wave energy conversion device embed with the magnetic bistable mechanism is derived.In order to speed up the solution of dynamic equation,the state space model is used to replace the convolution integral term of wave radiation force,and then the evaluation parameters of wave energy capture performance of wave energy conversion device are given.Secondly,the energy capture characteristics of point absorption wave energy conversion device with a single magnetic rings bistable mechanism is analyzed.This bistable mechanism is mainly composed of a pair of permanent magnetic rings which are magnetized in the same direction.Based on the analytical method,the mechanism model of this device is derived.By analyzing the potential energy of the bistable device,the static characteristics of the wave energy device under different structural parameters are investigated,which provides a preliminary effective parameter field for the parameter design of the device.Then based on the numerical simulation analysis,the influence of system parameters and wave parameters on the wave energy conversion characterisics of the device embed with a single permanent magnetic rings mechanism is studied.Combined with phase diagram analysis and spectrum analysis,the mechanical mechanism of the wave energy conversion device embed with the bistable mechanism is revealed for improving capture efficiency and broadening frequency band of wave energy conversion.Finally,aiming at the inherent shortcoming that the lower efficiency of wave energy conversion of the traditional point absorption wave energy conversion device under the small wave excitation,a new double magnetic rings bistable mechanism is proposed.A pair of auxiliary permanent magnetic rings with opposite magnetization are added to the original bistable mechanism with a single magnetic rings to bulid this mechanism.According to the static analysis results of the point absorption wave energy conversion device with a double magnetic rings bistable mechanism,the double magnetic rings bistable mechanism can reduce the barrier height and widen the distance between the equilibrium points of the nonlinear system at the same time under appropriate parameters.Based on the numerical simulation analysis,the energy capture characteristics of three different wave energy conversion devices(linear wave energy conversion device,wave energy conversion device with single magnetic rings,wave energy conversion device with double magnetic rings)are compared and analyzed.Results show that the wave energy conversion device with double magnetic rings can effectively make up for the traditional bistable device in lower capture efficiency under small wave amplitude excitation,while maintaining the advantage of increasing capture efficiency and broadening frequency band under the larger wave amplitude excitation.