The dynamic characteristics of running away pump turbines (PTs) with a large head variable amplitude have not been understood thus far, primarily because of two difficulties in simulation and analysis. The first is how to provide accurate time-varying boundary conditions for transient simulation of the turbine runaway process (TRP). The other is how to determine the specific appearance time of each frequency component of the complex pressure fluctuations. This study presented a one- and three-dimensional (1D-3D) coupled approach considering waterway dynamics to provide accurate unsteady boundary conditions for the transient flow simulation of a PT with a large head variable amplitude. The short-time Fourier transformation (STFT) approach was adopted to analyse the time-frequency characteristics of the transient pressures and impeller forces. The study found that the fluctuations of pressures and impeller forces during the TRP of the PT with a large head variable amplitude contained two exclusive fluctuation frequency components. The former was approximately three times the rated rotational frequency of the impeller. The later was a series of integer fold transient rotational frequencies of the impeller, which was irrelevant to the rotor-stator interactions. The findings have important value for controlling the pressure fluctuations during the TRP of PTs.

大水头变幅失控水泵水轮机(PT) 的动态特性迄今尚未了解，这主要是因为仿真和分析存在两个困难。首先是如何为涡轮失控过程 (TRP) 的瞬态仿真提供准确的时变边界条件。二是如何确定复杂压力波动的各个频率分量的具体出现时间。本研究提出了一种考虑水路动力学的一维和三维 (1D-3D) 耦合方法，为具有大水头变幅的 PT 的瞬态流动模拟提供准确的非稳态边界条件。采用短时傅里叶变换 (STFT) 方法分析瞬态压力和叶轮力的时频特性。研究发现，大水头变幅PT的TRP过程中压力和叶轮力的波动包含两个独有的波动频率分量。前者约为叶轮额定旋转频率的三倍。后者是叶轮的一系列整数倍瞬态旋转频率，与转子-定子相互作用无关。该发现对于控制 PT 的 TRP 期间的压力波动具有重要价值。后者是叶轮的一系列整数倍瞬态旋转频率，与转子-定子相互作用无关。该发现对于控制 PT 的 TRP 期间的压力波动具有重要价值。后者是叶轮的一系列整数倍瞬态旋转频率，与转子-定子相互作用无关。该发现对于控制 PT 的 TRP 期间的压力波动具有重要价值。