水泵水轮机运行中的若干典型过渡过程

为了深入研究水泵水轮机不良过渡过程对机组产生的不利影响及其相应的改善措施,综述了水泵水轮机特性曲线的特有性质和重要的典型过渡过程的研究进展.详细说明了水泵水轮机过渡过程中的迟滞现象,发现水泵水轮机的运行工况点不仅与系统的当前输入有关,而且与系统过去的历史有关,因此在特定区域内水泵水轮机在同一转速时对应的流量并不相同,从而导致水泵水轮机机组的水头下降、效率降低、机组振动和产生噪声.综述了迟滞现象产生的条件,转速的影响以及改变转轮叶片进口角和叶片后掠角等改善措施;转轴应力测量的试验研究进展以及转轮叶片和导叶间的动静干涉对动态应力测量信号分析的影响,给出了相关现象的主要特征和影响因素;针对水轮机启动时的空载不稳定现象和导叶关闭时的不稳定现象可采取的改善措施,并比较了各种方法的优越性和弊端.

Several typical transient processes of pump turbine

In order to study the negative effects of abnormal transient processes on the pump turbine and the corresponding improved measures, the inherent feature of performance curve of the pump turbine(named S-shaped characteristics),together with the recent research progress in several typical transient processes of the pump turbine, is introduced. The S-shaped characteristics shown in the performance curve of the pump turbine along the guide vane opening line are briefly introduced, with its physical origins and negative effects. A detailed introduction to the hysteresis phenomenon of the pump turbine is performed and it is found that the present discharge of pump turbine at the fixed rotational speed is not a unique value because the operational condition of the pump turbine depends not only on the current input of the system but also on the history of the system and hence the hysteresis phenomenon leads to the drop of water head,low efficiency, vibrations and noise. The generation condition of the hysteresis phenomenon, the influence of rotational speed and the improved methods based on changing runner inlet and outlet angles are set forth. Measurement of the dynamic stress on the shaft and influences of the rotor-stator interaction on the measured signal analysis are both elaborated,giving the corresponding phenomena, basic characteristics and paramount influencing parameters. The instability of the pump turbine working with no load at start-up as well as the instability at the guide vanes closure, and the solutions to them are also expounded. Mereover, the advantage and the disadvantage of different methods are compared.