抽水蓄能电站过渡过程中输水系统与水泵水轮机水力振荡动态响应机理研究

Severe vibrations, even the extreme accidents—turbine-generator unit lifting-up and generator rotor-stator crash—frequently occurred during hydraulic transient processes in many of the pumped-storage plants in China. The mechanism yet is unclear, though we know that the waterway system may amplify pressure pulsations of pump-turbines and possibly cause resonance. Therefore, the dynamic response of hydraulic oscillations between the hydraulic waterway system and the pump-turbine is the topic needing urgent and intensive study. Try to reveal the mechanisum and developing process of unit lifting-up accidents, this project investigates the dynamic response and resonance between the oscillating waves in the long waterway system and the pressure pulsations in the pump-turbines, along with the extreme consequences undergoing water column separation, vapor cavity collapse and inverse water hammer processes during violent hydraulic transients. The coupled approaches of the one-dimensional (1D) waterway system with the three-dimensional (3D) pump-turbines, combined with theoretical analysis and model tests, are applied to analyze the processes and laws of the transient phenomena.Different conditions, namely with or without waterway system, transient or stationary operation, are compared. The influence factors of hydraulic oscillation and resonnse are investigated by varying layouts of water conveyance system, working conditions of units, and operating trajectories of transient processes. We strive to answer why the vibration of pump-turbine is serious when consider the contribution of waterway system, why it becomes much more serious during transient process, and how the phenomena of water-column separation, vapor cavity collapse and reverse water hammer occur. A numerical simulation technique of coupling the 1D Method Of Characteristics for the water conveyance system and the 3D Computational Fluid Dynamics for the pump-turbine will be developed and verified by the model tests in the newly built Model Test System for Transient Processes of Pumped-Storage Plants, which is actually a micro pumped-storage plant. The hydraulic response mechanism of the waterway system with pump-turbines, the formation mechanism of draft tube cavitation and reverse water hammer, and the algorithms for accurately simulating the 3D hydraulic transients in pumped-storage plants will be the main results after conducting this study. These achievements will provide theoretical basis and knowledge for engineering practice to control the serious pressure pulsations in pump-turbines and prevent the violent accidents of reverse water hammer and up-lifting of turbine-generator units.

抽水蓄能机组在过渡过程中剧烈振动，导致抬机、扫膛等重大事故频繁发生，其机理亟待研究，其中输水系统对机组压力脉动的放大或共振问题值得关注。本项目将一维输水系统和三维水泵水轮机耦合起来，研究过渡过程中输水系统与机组水力振荡的动态响应，分析水力系统振荡与共振、尾水管气液两相流、转轮受力演变，力图揭示抬机事故发生发展机理和规律。利用一维输水系统耦合三维水泵水轮机的过渡过程CFD模拟技术，结合已建微型抽水蓄能电站实验平台和理论分析，对比有无输水系统、稳态与过渡态，研究输水系统特性、过渡过程路径等对水泵水轮机压力脉动的影响及共振条件，探索极端过渡过程工况尾水管水柱分离弥合现象，回答过渡过程压力脉动比稳态剧烈、带输水系统比不带输水系统剧烈的原因。成果是输水系统与机组耦合振荡机理、反水锤形成机理、准确模拟过渡过程水泵水轮机三维瞬变流特性的模型和算法，为工程中控制压力脉动和振动、防止反水锤和抬机奠定基础。

本研究旨在揭示水泵水轮机水力振荡及其与输水系统相互作用机理。研究内容包括3项：（1）稳态运行工况水泵水轮机水力振荡及输水系统动态响应；（2）过渡过程水泵水轮机水力振荡及输水系统动态响应；（3）极端过渡过程中水柱分离弥合反水锤气液两相流。..取得明显进展的方面：水泵水轮机S特性形成机理、水泵水轮机S区流动和压力脉动分布特性、抽水蓄能电站输水系统水力振荡可能性分析、水泵水轮机过渡过程动态特性机理及其影响、水泵水轮机飞逸中压力脉动和转轮受力演变机理、一维输水系统与三维水轮机耦合的过渡过程模拟方法、计入调速系统的过渡过程三维数值模拟方法、球阀关闭抑制过渡过程水泵水轮机S区不稳定振荡的机理、飞逸工况尾水管空泡形成溃灭反水击模拟、甩负荷过程水柱分离弥合问题模拟。..最重要的贡献是：将水电站过渡过程计算模型从一为发展到三维，揭示了水泵水轮机不稳定S特性的机理和过渡过程中动态特性的机理，明确了水轮机流态、压力脉动和转轮受力的变化规律，为后续深入研究抽水蓄能电站抬机、扫膛等事故，保证电站安全奠定了坚实基础。..共发表成果33项，其中期刊论文28篇，会议论文2篇，专利2项，软件著作权1项。毕业博士2人，硕士13人。..项目结题后，将继续深化相关研究还并发表相应成果。