基于POD降阶模型和反问题设计方法的水泵水轮机叶轮优化设计研究

Hydraulic performances of pump-turbine are essential for safe, stable, and efficient operation of pumped storage units. The mechanism of the pump-turbine's "S" shape characteristics has not been completely understood yet. As a result it's difficult for existing design methods to eliminate this feature. In order to solve the problem, a multi-point, multi-object optimization design method will be constructed in this research to control the comprehensive performances of the pump-turbine's impeller effectively to improve or even eliminate the "S" shape characteristics during the design stage with smaller computation costs. To this end, the reduced order models for three-dimensional turbulence flows in the impeller under different operation points changing with different impeller geometries are established based on proper orthogonal decomposition method (POD). By applying the models the flow field information can be extracted fast and reliably. Then a three-dimensional turbulence inverse deign method is developed by combining POD reduced order models and blade geometry calculation method. On these basis, combining with a multi-objective Pareto genetic algorithm, the improvement or even elimination of the "S" shape characteristics may be achieved by setting the impeller shape parametres as optimization variables, and setting the energy， cavitation and stability performances of the bidirectional flow in pump-turbine under typical operation points as optimization objects and constraints. This study will not only provide new scientific methods for the optimization design of the impeller machinery, but also have important meanings for promoting the mechanism research of the "S" shape characteristics.

水泵水轮机水力性能对抽水蓄能机组安全、稳定、高效运行至关重要。由于水泵水轮机"S"特性产生的机理尚不完全清楚，现有设计方法难以消除这一不稳定特性，针对这一难题本项目拟构建水泵水轮机叶轮多工况、多目标优化设计方法，以较小的优化计算代价实现设计阶段对叶轮综合性能的有效控制，改善甚至消除"S"不稳定特性。为此，基于本征正交分解法（POD）建立不同工况下水泵水轮机叶轮三维湍流流场随叶轮形状变化的降阶模型，能够快速可靠的提取流场信息；将POD降阶模型与叶片形状计算方法结合，建立三维湍流反问题设计方法；在此基础上，结合多目标的Pareto遗传算法，以叶轮形状参数为优化变量，以水泵水轮机叶轮双向流场典型工况下的能量性能、空化性能和稳定性性能为优化目标和约束条件，实现水泵水轮机"S"不稳定特性的改善甚至消除。本研究不仅为叶轮机械的优化设计提供新的科学方法，对促进水泵水轮机"S"特性的机理研究也有重要意义。

水泵水轮机是抽水蓄能电站的关键设备之一，其水力性能对电站的安全稳定运行具有重要影响。水泵水轮机运行工况复杂、多变，如何保证水泵水轮机在多个工况下都具备良好的性能是研究的难点。本项目从水力设计方法的角度研究上述问题，开展了基于三维反问题设计方法的水泵水轮机叶轮多工况、多目标的水力优化设计研究，运用载荷分布参数表达叶片形状，利用三维反问题设计方法完成叶片形状设计，应用CFD技术评价叶轮水力性能并建立设计参数和性能参数的响应面函数关系，最后基于多目标的优化算法得到优化设计的Pareto前沿，完成优化设计。将上述方法应用到某一模型水泵水轮机的优化设计中，并进行了实验验证，证明了所建立的水泵水轮机叶轮多工况、多目标优化设计方法的有效性。本项目的研究成果不仅提高了水泵水轮机的设计水平，同时为其它叶轮机械的优化设计提供参考。