Transient simulation of a pump-turbine with misaligned guide vanes during turbine model start-up

Xiao, Yexiang; Xiao, Ruofu

doi:10.1007/s10409-014-0061-6

Cited by 28 publications

(11 citation statements)

References 7 publications

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“…In addition, the hydraulic system in Figure 2 is modified to the equivalent system consisting of eight different pipes. The various pipes in series (1-6), (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), (17,19,21), (18,20,22), (23,25,27,29,31), (24,26,28,30,32), (33,34), and (35-38) of the original system shown in Figure 2 were substituted by their respective single equivalent pipes [30]. The sensitivity analysis was carried out with the equivalent system for OS 2 and OS 3 .…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…The mitigation of S-shaped characteristics has also been the major area of research for several decades. In many currently operating pumped storage plants, inlet valve throttling [23,24], anti S-shaped characteristic governor [25], and misaligned guide vane [26,27] are various techniques deployed to countermeasure the aftermaths of S-shaped characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic Oscillation and Instability of A Hydraulic System with Two Different Pump-Turbines in Turbine Operation

Palikhe

Zhou

Bhattarai

2019

Water

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Hydraulic oscillation mainly reveals the undesirable pressure fluctuations which can cause catastrophic failure of any hydraulic system. The behavior of a hydraulic system equipped with two different pump-turbines was investigated through hydraulic oscillation analysis to demonstrate severe consequences induced in turbine operation, including S-shaped characteristics. The impedance of a pump-turbine has an essential role in the determination of the instability of the hydraulic system. The conventional way to determine the instability solely using the slope of a characteristic curve was improved, including the effect of guide vane opening in pump-turbine impedance, which consequently modified the instability expression. With this pump-turbine impedance, hydraulic oscillation analysis, including free oscillation analysis and frequency response analysis, was carried out. The free oscillation analysis entails the computation of complex natural frequencies and corresponding mode shapes of the system. These computations provided necessary information about the vulnerable position of vital hydraulic components and the scenario for self-excited oscillation. Further, the analysis illustrates the significant role of guide vane opening to prevent the system from becoming unstable. Lastly, frequency response analysis was performed for the system with an oscillating guide vane to obtain the frequency response spectrum, which revealed that the resonating frequencies are consistent with natural frequencies, and it supported free oscillation results.

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Section: Sensitivity Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydraulic Oscillation and Instability of A Hydraulic System with Two Different Pump-Turbines in Turbine Operation

Palikhe

Zhou

Bhattarai

2019

Water

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“…In addition, especially during the startup or shutdown process, the resonance of the units also frequently occurs, which is usually caused by rotor-stator interference (RSI) [15], self-excitation [16], or pressure pulsation [17]. To improve the stability and guarantee the successful startup of the units, misaligned guide vanes (MGVs) have been implemented and have achieved the expected results [18].…”

Section: Introductionmentioning

confidence: 99%

Flow Deflection between Guide Vanes in a Pump Turbine Operating in Pump Mode with a Slight Opening

Liao

et al. 2022

Energies

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During the startup and shutdown processes of a reversible-pump turbine (RPT) working in pump mode, abnormal sounds and vibrations usually occur in the distributor when the guide vanes (GVs) are at a slight opening (max opening of about 6%). The objective of this paper is to apply a three-dimensional numerical CFD method to study the unsteady flow behavior in the guide vane region of a pump turbine operating in pump mode. The dynamic meshing technique is introduced to simulate the startup and shutdown processes, and it is shown to be critical in accurately capturing the details of the flow pattern variations. In addition, the RNG k-epsilon two-equation turbulence model is applied and the governing equations are discretized with the finite volume method. Moreover, the boundary conditions are set through the calculation of the transient process of the power station. The results show that the main flow between the GVs is deflected during the startup and shutdown processes. In the shutdown process, the deflection occurs when the guide vane opening (GVO) is between 1.99 and 5.32 degrees, on average. In the startup process, the deflection occurs when the GVO is between 2.83 and 4.11 degrees, on average. In these processes, the velocity field and pressure field change dramatically. Simultaneously, the hydraulic torque (HT) on the GVs has a sharp change. The abrupt change in the HT leads to vibrations and abnormal sounds.

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“…The development of pumped storage plants is very fast in China, and many pump storage plants adopted the Misaligned Guide Vanes (MGV) method to eliminate the S-shaped characteristics and improve the stability. Therefore, it makes the guide vanes operating system more complex and leads to serious pressure pulse in rotating runner [3][4][5][6][7] . Recently, Chinese new pumped storage power station under construction is not recommended the MGV method.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode

Xiao

Zhu

Wang

et al. 2016

Engineering Computations

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2016),"Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode", Engineering Computations, Vol. 33 Iss 2 pp. 543 -561 Permanent link to this document: http://dx.(2016),"A new strain-based finite element for plane elasticity problems", Engineering Computations, Vol. 33 Iss 2 pp. 562-579 http://dx.(2016),"A computational and experimental study for the optimum reinforcement layout design of an RC frame", Engineering Computations, Vol. 33 Iss 2 pp. 507-527 http://dx.If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services. AbstractPurpose -The purpose of this paper is to numerically analyze the flow characteristic and to explore the hydrodynamic mechanism of the S-shaped region formation of a Francis pump-turbine. Design/methodology/approach -Three-dimensional steady and unsteady simulations were performed for a number of operating conditions at the optimal guide vanes opening. The steady Reynolds averaged Navier-Stokes equations with the SST turbulence model were solved to model the internal flow within the entire flow passage. The predicted discharge-speed curve agrees well with the model test at generating mode. This paper compared the hydrodynamic characteristics of for off-design cases in S-shaped region with the optimal operating case, and more analysis focusses particularly on very low positive and negative discharge cases with the same unit speed. Findings -At runaway case toward smaller discharge, the relative circumferential velocity becomes stronger in the vaneless, which generates the "water ring" and blocks the flow between guide vane and runner. The runner inlet attack angle becomes larger, and the runner blade passages nearly filled with flow separation and vortexes. The deterioration of runner blade flow leads to the dramatic decrease of runner torque, which tends to reduce the runner rotation speed. In this situation, the internal flow cannot maintain the larger rotating speed at very low positive discharge cases, so the unit discharge-speed curves bend to S-shaped near runaway case. Originality/value -The analysis method of four off-design cases on S-shaped region with the comparison of optimal operation case and the calculated attack angles are adopted to explore the mechanism of S characteristic. The flow characteristic and quantitative analysis all explain the bending of the unit discharge-speed curves.

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Transient simulation of a pump-turbine with misaligned guide vanes during turbine model start-up

Cited by 28 publications

References 7 publications

Hydraulic Oscillation and Instability of A Hydraulic System with Two Different Pump-Turbines in Turbine Operation

Hydraulic Oscillation and Instability of A Hydraulic System with Two Different Pump-Turbines in Turbine Operation

Flow Deflection between Guide Vanes in a Pump Turbine Operating in Pump Mode with a Slight Opening

Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode

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