不规则波激励下磁力双稳态波浪能转换装置的能量捕获特性研究

该研究提出了一种新型磁力双稳态机构,主要由一对同向充磁的负刚度磁环,附加一对异向充磁的正刚度磁环组成,可通过调整磁环参数有效改变双稳态装置的势垒高度,从而克服传统型双稳态装置在小幅波浪激励下转换效率低的难题。基于Cummins方程建立了系统的时域非线性动力学模型,其中采用状态空间模型替代了辐射力的卷积积分项用于加快计算速度。采用四阶龙格库塔方法求解动力学方程,获得系统响应解。采用Jonswap波浪谱,研究了不规则波激励下波浪能转换装置的转换效率随双稳态结构参数以及波浪激励参数的变化规律。结果表明,新型磁力双稳态机构在合适参数下可以达到降低势垒高度和拓宽平衡点间距的效果,从而显著提高波能捕获效率,拓宽波能捕获频带,尤其是大幅提高了系统在小波高激励下的捕获宽度。

Study on energy capture characteristics of magnetic bistable wave energy conversion device under irregular waves

In this paper, an improved magnetic bistable mechanism is proposed, which is mainly made up of a pair of negative stiffness magnetic rings with the same direction of magnetization and a pair of positive stiffness magnetic rings with the opposite direction of magnetization. The potential energy barrier of bistable system can be adjusted by choosing the structural parameters. Then the problem of low conversion efficiency of the traditional bistable device under the condition of small wave amplitude can be overcome. The nonlinear dynamic model of system in the time domain is established based on the Cummins function. The state space model is used to replace the convolution integral term of the radiation force for expediting calculation speed. The fourth-order Runge Kutta method is used to solve the dynamic equation and obtain system dynamic responses. The Jonswap wave spectrum is adopted to analyze the effect of the structural parameters and wave excitation parameters on the efficiency of wave energy conversion device under irregular wave excitation. The results show that the improved magnetic bistable mechanism can reduce the potential barrier and widen the distance of equilibrium points under reasonable parameters. It can significantly improve the wave energy capture efficiency, effectively broaden wave energy capture frequency band, and dramatically improve the performance of wave energy conversion device under the low amplitude wave excitation.