可逆式水泵水轮机“S”特性的内流激励机制及控制策略研究

The "S" characteristics area of reversible pump-turbine is an extremely unstable region. The area directly impacts the stability of pump-turbine when it starts without load in the working condition of generating electricity, which will eventually lead to some difficulties when the unit operation starts and the grids connect. Ultimately it will affect the stability and reliability of the unit operation seriously. In this study, the flow characteristics of reversible pump-turbine in hydraulic transient process is considered from the beginning, aiming to put forward the speed-flow coupled mathematical model for calculating concerning the control of guide vanes during the starting process of the reversible pump-turbine unit. Then, this hydraulic transients process can be simulated by means of The grid generation technique of three-dimensional solid motion boundary grid generation technique. In addition, The numerical method can be examined by PIV visual testing technology. The "S" characteristics for the formation of three-dimensional spatio-temporal evolution of transient flow structures, laws and mechanisms will be researched, as well as the flow-excited mechanism of the "S" characteristics. Besides, the influence of putting the misaligned guide vanes (MGV) on the "S" characteristic and necessary internal flow characteristics for the elimination of the "S" characteristics are explored. The coupling calculation model of considering the "S" characteristics with MGV is put forward. Finally, a reference and a basic theory for the "S"-field behavior control of the reversible pump-turbine will be provided.

可逆式水泵水轮机的“S”特性区是一个极不稳定区。“S”特性区直接影响水泵水轮机发电工况启动时空载稳定性，导致机组启动并网困难，严重影响机组的运稳定性与可靠性。本项目从可逆式机组水力暂态过程的内流特性出发，参照工作点轨迹，建立在导叶调节作用下，启动-并网过程流量-转速的自耦合计算数学模型；应用三维固体运动边界按规律大错变网格再生成技术，实现启动-并网水力暂态过程的数值模拟；通过PIV可视化测试实验，对数值方法进行验证；在此基础上，研究可逆式水泵水轮机“S”特性产生过程对应的三维瞬变流动结构的时空演化过程、规律和作用机理，分析“S”特性产生的内流激励机制；同时研究投入非同步导叶装置对“S”特性改善的作用机理，提出“S”特性关于非同步导叶布置方式、开启对数和开启角度的耦合计算模型，为可逆式水泵水轮机“S”区特性的控制提供理论参考和依据。

可逆式水泵水轮机“S”特性区引起的机组运行不稳定问题，已经成为当前可逆式水泵水轮机设计、运行环节中最重要的问题，直接影响可逆式水泵水轮机发电工况空载启动时的稳定性，如果处理不好，甚至会引起整个电力系统的崩溃，带来巨大的经济损失。. 本项目针对可逆式水泵水轮机“S”特性与内流激励机制和控制测略开展了相应研究，主要研究内容及结论。以模型可逆式水泵水轮机为研究对象，建立了计算模型，进行了网格划分，进行了可逆式水泵水轮机全流场三维湍流数值模拟。从可逆机组水力暂态过程的内流特性出发，参照工作点的轨迹，建立在导叶调节作用下，启动-并网-过程流量-转速的自耦合计算数学模型；应用三维固体运动边界按规律大错变网格在生技术，实现启动-并网水力暂态过程的数值模拟；通过VIP可视化测试实验，对数值方法进行验证；在此基础上，研究可逆式水泵水轮机“S”特性产生过程对应的三维瞬变流动结构的时空演化过程、规律和作用机理，分析“S”特性产生的内流激励机制；数值模拟结果与模型试验结果对比得到综合特性曲线基本趋势一致，吻合度较高，表明三维全流道非定常数值计算的可信、可靠；针对可逆式水泵水轮机的“S”特性区域特殊流动问题，围绕机组内部流动特征、湍流结构的时空演变机制，着重分析计算了水泵水轮机水轮机工况同步启动过渡过程中的内流特性及其演化过程，得出了“S”特性内流诱导机理，探讨了“S”特性改善的内流控制方法。. 同时，通过数值模拟得到投入MGV装置下，可逆式水泵水轮机“S”特性区单位转速与单位流量的关系曲线，探讨了同步导叶与MGV不同布置方式对“S”特性的影响，得出两对非同步导叶均匀分散对称布置为最优MGV布置方式的结论；同时通过对可逆式水泵水轮机非同步导叶工况下的全流场三维定常和非定常流动分析，得到了可逆式水泵水轮机最优MGV布置工况的内流特性及改善机理，为可逆式水泵水轮机综合水力性能的改善提供参考。