遗传算法在水平轴洋流机叶片优化设计中的应用

水平轴洋流机是捕获洋流能的主要设备,其叶片外形直接影响捕能效率。通过Bezier参数化曲线描述定速定桨距洋流机的叶片弦长和扭角分布规律,采用叶素-动量理论计算其水动特性。以额定流速下能量利用系数系数最大为目标,基于遗传算法建立了叶片外形优化模型。同时,为了避免因汽蚀导致功率输出不稳定的现象,在优化过程中以汽蚀作为约束条件,与经典设计方法Wilson理论设计叶片进行了比较。结果表明:优化叶片在叶根处的扭角更小,具有更佳的抗扭性能;叶根和叶尖处弦长均更小,节省了材料;在设计流速范围内,优化叶片在低流速下效率更高,平均提高了4.6%,具有更好的启动性能。

Application of Genetic Algorithm to the Optimization Design of Horizontal Axis Tidal Turbine Blade

Horizontal axis tidal turbine is the key equipment to capture energy of the current.The blade shape can directly affect the capture efficiency.In this paper,the distribution of chord length and twist angle for tidal turbine blade with fixed speed and pitch was described by Bezier parametric curves.Blade-element momentum theory was applied to calculate its hydraulic dynamic characteristics.With the goal of maximizing the power coefficient at the constant flow velocity,the optimization model of blade shape was built based on genetic algorithm.Meanwhile,in order to avoid the instability of power output caused by cavitation,the cavitation resistance was used as constraints in the optimization model.Compared with the classical Wilson theory of blade design,the results showed that the torsional angle has reduced in the hub of the optimized blade and the better torsion properties was achieved.The root and tip chord length of the blade decreased,which could save materials.Within the range of designed flow rate,higher efficiency was achieved for the optimized blade under low flow rate.The efficiency increased by 4.6% on average.The better startup performance was achieved as well.