动力输出系统(PTO)对集成波能转换装置式防波堤消波性能及波能捕获率影响研究

针对波浪能转换装置(WEC)研究重点主要集中在能量捕获效率方面,而忽略其附带的消波功能的问题。基于Open FOAM程序,建立垂荡浮子式波浪能发电装置与桩式约束的浮式防波堤的集成系统(OBC-FB)。主要研究WEC中的重要组件动力输出系统(PTO)对集成系统波能捕获效率及消波性能的影响。分析流体黏性影响下线性PTO系统的最优PTO阻尼特性。开发非线性电磁阻尼模型与线性PTO系统性能进行比较。结果显示,考虑黏性影响下线性的最优PTO阻尼系数略大于无黏的理论值;适当增大PTO阻尼系数可以获得更大的波能捕获宽度比(CWR),从而可以保证装置单位特征尺寸的波能转换效率更高,同时可以在更宽波况范围保证消波性能;相较于线性PTO阻尼系统,非线性电磁PTO阻尼系统可以更好地兼顾波能捕获效率和消波性能。因此,在OBC-FB集成系统的优化设计中,PTO阻尼系统是一个重要的优化参数。

Effect of the PTO damping force on the wave damping performance and wave capture efficiency of a WEC-type breakwater

The traditional studies of wave energy converters (WEC) mainly focus on how to improve the wave capture efficiency but neglect their coastal protection function. Based on the cost-share concept, an integration system of oscillating bouy WEC and a pilerestrained floating breakwater (OBC-FB) is built with OpenFOAM. The aim of the study is to evaluate the parametric effect of a power take-off (PTO) system that is an essential component of the WEC on both the wave energy capture efficiency and wave damping performance of this integration system. Detailed research is done on the optimal linear PTO coefficient under viscous effect. A nonlinear Coulomb type PTO system is developed to compare with the linear one. The results are shown below: the linear optimal PTO coefficient under viscous flow can be larger than the theoretical optimal coefficient in terms of the potential flow. A larger PTO coefficient can promise a better capture width ratio(CWR) value, which means higher wave energy capture efficiency in one unit typical length of the device and better wave damping performance in a wider wave frequency range. A comparison of the Coulomb damping model and the linear damping model also shows that the Coulomb type PTO system has a good performance in terms of both wave energy capture efficiency and coastal protection. Hence, the effect of the PTO system on such an integration system can be an essential factor to achieve an optimal design.