To demonstrate the influence of cavitation on pressure fluctuation in a pump-turbine, one- and three-dimensional coupling numerical simulations were conducted on a typical runaway process that occurs when the turbine rejects the load. Transient flow in the pipelines was simulated using a one-dimensional single-phase flow model. The unsteady three-dimensional turbulence flow in the pump-turbine was calculated using the single- and two-phase flow models. The numerical method was validated with available experimental data. The maximum simulation errors of the rotational speed and fluctuating pressure were 3 and 10%, respectively. Local backflow vortices leading to the cavitation were identified at the high-pressure runner inlet. The cavitation interacted with the vortices during the runaway process when the turbine rejected the load. These interactions increased the existing duration and action range of the backflow vortices at the runner inlet. Under the excitation of the local cavitation backflow vortices and the shock pressure induced by the instantaneous cavity collapse, the amplitudes of the pressure and hydraulic thrust fluctuations using the two-phase flow model increased significantly to approximately thrice that obtained using the single-phase flow model. While using the single-phase flow model, severe fluctuations occurred near the no-load condition. The occurrence instants of severe fluctuations while using the two-phase flow model were delayed by a specific duration compared to the no-load condition; this is attributed to the duration of cavitation development from the inception of cavitation to the maximal cavity volume. This finding is valuable for the accurate prediction and optimization of pressure fluctuations in the turbine runaway process.

为了证明气蚀对泵-涡轮机中压力波动的影响，对涡轮机拒绝负载时发生的典型失控过程进行了一维和三维耦合数值模拟。使用一维单相流模型模拟管道中的瞬态流。泵涡轮中的非定常三维湍流是使用单相和两相流模型计算的。数值方法通过可用的实验数据进行了验证。转速和脉动压力的最大模拟误差分别为 3% 和 10%。在高压流道入口处发现了导致空化的局部回流涡流。当涡轮机拒绝负载时，空化在失控过程中与涡流相互作用。这些相互作用增加了流道入口处回流涡流的现有持续时间和作用范围。在局部空化回流涡的激发和瞬时空腔坍塌引起的冲击压力下，两相流模型的压力和水推力波动幅度显着增加，约为单相流模型的三倍。 . 在使用单相流模型时，在空载条件附近出现剧烈波动。与空载条件相比，使用两相流模型时发生剧烈波动的时刻延迟了特定的持续时间；这归因于从空化开始到最大空腔体积的空化发展持续时间。