Renewable Energy, Vol.163, 517-529, 2021
Pressure fluctuation characteristics of a model pump-turbine during runaway transient
The runaway transient of pump-turbine usually goes in an oscillating mode with large variations of flow parameters. In this work, dynamic flow characteristics during the runaway are numerically investigated, focusing on the variations of rotation speed, flow rate, torque, and the corresponding pressure fluctua-tions. The time-frequency relationship of pressure pulsations in major flow passage components is analyzed using fast Fourier transform (FFT) and short-time Fourier transform (STFT), where a few special frequency bands related to rotational frequency are presented. Low-frequency components of pressure oscillations are universal in the flow passage, and mainly due to the temporal changing of flow rate. Runner-stator interaction induced frequency bands show highest magnitude in the runner, accompanying with reversed flow. (C) 2020 Elsevier Ltd. All rights reserved.