贯流式水轮机转轮叶片的多学科优化设计

Optimal design of runner blade in bulb turbine base on multidisciplinary feasible method

为了变革传统的转轮优化设计方法,在缩短转轮研发周期的同时能确保转轮安全、高效的运行,有必要开展转轮的多学科优化设计方法研究。该文基于多学科可行性优化策略(multidisciplinary feasible method,MDF)提出了一种能兼顾水力性能和强度应力的贯流式转轮叶片多学科优化设计方法。该方法以转轮叶片的几何形状参数作为优化变量,以转轮叶片的水力效率以及叶片上的最大静应力值作为优化目标,并通过MDF策略构建整个多学科优化求解系统,同时引入NSGA-II算法作为寻优算法开展了贯流式叶片的多学科优化设计。优化过程中,采用弱耦合方法完成每个优化个体的多学科性能分析以缩减整个优化流程的计算时间,提升了该方法的工程实用性。采用该方法对某电站的贯流式水轮机模型转轮进行优化,优化后水轮机的水力效率提高了0.3%,转轮叶片的最大应力值降低了16.3%,表明该方法是有效的,并具有实际的工程应用价值。

The design of a hydro turbine＇s runner involves many disciplines, such as fluid, structure, strength and so on. As the hydro turbine＇s capacity increases, the owner of a power plant has strengthened the demand for the turbine＇s stability. But the traditional sequence design method has difficulty meet ing the demand of the design requirements. So it is necessary to establish a new optimization design method called the multidisciplinary design optimization method, which can consider the interaction of each discipline. At present, the optimal design method of a hydro turbine＇s runner still can not combine each discipline perfectly in design process. It is necessary to carry out the research about multidisciplinary design optimization （MDO） design method of hydro turbine＇s runner. Based on the research findings of other fields about multidisciplinary optimization, this paper draws the MDO design method into hydro turbine＇s runner design, and carries out a preliminary study on the turbine runner＇s MDO design method. On the basis of design characteristics of a hydro turbine, an optimization design system has been established according to the multidisciplinary method in this paper. This optimization design system could improve the runner blade＇s hydraulic performance and structural strength simultaneously. In addition, a parameterized module based on the Bezier curve, auto mesh module, computational fluid dynamic module, and finite element analysis module were integrated in the system. The system automatically completes geometry modeling, mesh generation, and multidisciplinary performance analysis. This system uses the geometric shape parameters of a runner blade as optimization variables, and the hydraulic efficiency and maximum stress of runner blade were used as objective functions. The NSGA-II algorithm was used to carry out the optimization. In order to reduce the time of optimization and increase this method＇s practicability, the calculation method of weak coupling was used for multidisciplinary analysis during optimization. After the multidisciplinary optimization system had been built, a bulb model turbine＇s runner was optimized using this system. After optimization, the Pareto solution was selected as the optimum solution. The optimum solution was then compared with the initial blade. The comparison results showed that after optimization, the efficiency of blade in optimum operating conditions had been improved 0.3%, and the maximum static stress on blade had been decreased 16.3%. The stress gradient on blade became more uniform, which showed that the optimum blade has better stress performance. In order to comprehensively compare the optimum blade with the initial, performance of initial and optimum blade in other conditions was also calculated and compared. The comparison showed that the optimum blade not only performs better in optimum conditions, but also performs better in other conditions. The comparison results verify that the idea of multidisciplinary optimization design of a hydro turbine runner is feasible, and the optimization system is effective.