抽水蓄能电站在电力系统中起着至关重要的作用，水泵水轮机是抽水蓄能电站中的核心机组。目前可逆式机组正朝着更高水头、更大容量的方向发展。较高水头水泵水轮机在运行中效率偏低、空化特性差、机组的过渡过程不稳定性较严重、运行振动等问题较为突出，而传统的转轮设计方法周期长、成本高、且需要反复校核。本文利用适用于水力机械叶轮设计的多目标优化设计系统设计了超高水头下的水泵水轮机转轮，并在优化计算基础上进一步探究了设计变量对转轮不同性能的影响。水泵水轮机的多目标优化设计系统将三维反问题设计方法、试验设计法、响应曲面法、CFD数值计算和多目标优化算法整合在一起，设计过程克服了传统转轮设计方法的缺点，大大缩减了设计时间和成本，且设计结果能够满足多种性能要求。文中利用此优化设计方法，完成了对超高水头水泵水轮机转轮的优化设计，选取叶片载荷分布规律和叶片高压边倾角为设计变量，叶片轴面形状、叶片厚度、叶片数量保持不变，对转轮在水泵工况下的效率、空化特性以及转轮在水轮机额定工况下的效率进行了优化，从优化计算结果中经过比较选择，得到了综合性能优良的优化转轮。根据遗传算法的优化计算结果进行了敏感性分析，敏感性分析分为局部敏感性分析和全局敏感性分析，局部敏感性分析适用于在个别设计点附近分析，全局敏感性分析的结果在整个设计空间范围内更具代表性，经过全局敏感性分析可知，在本次对超高水头水泵水轮机转轮的优化设计过程中，叶片载荷对转轮性能影响较大，而叶片高压边倾角对转轮性能影响较小。为探究设计变量对转轮性能影响机理，从多目标优化计算结果中筛选出多个转轮并重新设计和数值计算，将结果与优化转轮、初始转轮比较，可以看出，在上冠处叶片载荷设计为中间受力，下环处设计为后向受力能有效改善转轮的效率特性；大正倾角转轮的效率特性较好；叶片高压边倾角的大小对转轮的空化特性影响不大。通过比较分析得出了适用于超高水头转轮设计的结论，丰富了设计经验。
Pump turbines have been the key units in pumped storage plants, which play a significant role in modern power energy system. At present, there is a trend to develop pump turbines with higher head and greater capacity. The performances of pump-turbine runner have crucial importance for safe, stable and effective operation of the pump-turbine units. However, a lot of problems exist in real operations in units with ultrahigh head, such as lower efficiency, bad cavitation characteristics, etc. By using the design-amendment-test method, which is commonly used nowadays, it is hard to develop a pump-turbine runner that has good performances under multi-operation conditions simultaneously. In this paper, a multi-objective optimization design strategy is introduced and used to develop several pump turbine runners which can be applied to plants with ultrahigh head. What’s more, in this paper we research the difference design parameters make on design objectives.Design of experiments, response of surface method, 3D inverse design method, numerical simulation and multi-objective optimization technique are organically composed to build the multi-objective optimization design system for turbomachinery. The design system has many advantages over the traditional design process, such as reduced design period and less cost. It can optimize several targets at the same time.Meridional channel shape, blade’s thickness, blades number are set as constant in the design for this paper. Blade loading and blade lean angle at high pressure side are selected as optimized input parameters. Efficiency under pump and turbine modes, minimum pressure on blade surface under pump operation are optimized. At last, a runner with good overall performance is developed and verified by simulation.Sensitivity analysis of input parameters is also conducted, together with the analysis of influence that the input parameters have on optimal pump-turbine runner. Design guidance for ultrahigh head pump-turbine runner are summarized. There are two different sensitivity analysis – local sensitivity analysis and total sensitivity analysis that have relations with each other. The result of total sensitivity analysis suggests that blade loading distribution has larger influence on runner performance than blade lean angle.Several runners are selected from the result of multi-objective optimization technique and CFD simulations are conducted to verify the runner performance. These runners are selected as reference to research what kind of influence on runner efficiency and cavitation performance the input parameters have. Comparision suggests that if middle loading near hub is set during design process, the runner with good power performance could be obtained. The blade lean angle on blade high pressure side almost has no influence on runner cavitation characteristics. Through comparing, the design experience of ultrahigh head pump turbine runner has been enriched.Key words: ultrahigh head pump turbine, multi-objective optimization design system, runner efficiency, blade lean angle, blade loading
