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Mechanism of Fast Transition of Pressure Pulsations in the Vaneless Space of a Model Pump-Turbine during Runaway

journal contribution
posted on 2019-12-01, 00:00 authored by X Zhang, Wei Zeng, Y Cheng, Z Yang, Q Chen, J Yang
The pressure pulsations in the vaneless space of pump-turbines are extremely intense and always experience rapid time variations during transient scenarios, causing structural vibrations and even more serious accidents. In this study, the mechanism behind the rapid time variations of the vaneless space pressure pulsations in a model pump-turbine during runaway was analyzed through three-dimensional (3D) numerical simulations. These results show that the high-frequency pressure pulsation components originating from rotor–stator interactions (RSI) are dominant during the whole process. These components fluctuate significantly in frequency when the working point goes through the S-shaped region of the characteristic curve, with the amplitudes increasing. Meanwhile, some low-frequency pulsations are also enhanced and become obvious. These features can be attributed to the transitions of the inter blade vortex structures (IBVSs) to the forward flow vortex structures (FFVSs) and the back flow vortex structures (BFVSs) at the impeller entrance, when the pump-turbine operates in the region with S-shaped characteristics. The FFVSs mainly cause decreases in frequency and introduce low-frequency pulsations, while the BFVSs are responsible for the unstable fluctuations. These findings contribute to the understanding of how transient flow patterns evolve and may provide new ideas about avoiding severe pressure pulsations caused by rotating stalls in the pump-turbine during transient scenarios.

History

Journal

Journal of Fluids Engineering, Transactions of the ASME

Volume

141

Issue

12

Article number

ARTN 121104

Pagination

1 - 13

Publisher

American Society of Mechanical Engineers

Location

New York, N.Y.

ISSN

0098-2202

eISSN

1528-901X

Language

English

Publication classification

C1.1 Refereed article in a scholarly journal

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