水轮机尾水管肘管的多工况优化设计

Multi-point optimization design of draft tube elbow

尾水管是中、低水头轴流式水轮机中非常重要的部件,它对转轮出口动能的回收以及水轮机的整机效率有重要影响。而肘管段作为尾水管中的核心部件,其形状对尾水管的性能有决定性影响。该文提出了一种尾水管肘管的多工况优化设计方法。该方法采用Bézier曲线参数化技术将肘管断面中线形状以及肘管断面的高度、宽度分布规律曲线以10个形状参数进行表达,以最优工况和额定工况下的尾水管平均静压回复系数作为目标函数,以NSGA-II算法作为寻优工具开展了尾水管肘管段的多工况优化设计。将该方法应用于某轴流式电站模型机尾水管肘管的优化,结果显示,含有优化后尾水管的水轮机整机效率在最优工况点提高了0.3%,在额定工况点提高了0.21%。

Draft tube is an important part of Kaplan turbine with low and medium water head, and it influences the recovery of kinetic energy in runner outlet and the overall efficiency of the hydraulic turbine. Elbow is the core component of the draft tube, which has decisive influence on draft tube＇s performance. Consequently, an optimization method for elbow has been presented in this paper. Firstly, the midline of elbow section and the distribution curve of section＇s height and width are described by ten parameters based on Bezier curve parametric technology. Secondly, using the average static pressure recovery factor in best efficiency point （BEP） and rated point as the objective function, the geometric variables of elbow are optimized in multi-point by NSGA-II algorithm. This method has been used to optimize a model Kaplan Turbine＇s elbow. After the optimization of draft tube, the overall efficiency of hydraulic turbine which contains optimal draft tube is increased 0.3% in BEP and increased 0.21% in rated point.