Model and prototype investigations of upper partial load unsteady phenomena on the Francis turbine designed for head up to 120 m

Kuznetsov, I. L.; Захаров, А. В.; Arm, V; Akulaev, R

doi:10.1088/1755-1315/22/3/032032

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…Yexiang et al (2010) indicated that as the load increases from small to large, the pressure pulsation in the draft tube first increases, then decreases, and then increases again. Nicolet et al (2010), Nicolet et al (2011) and Kuznetsov et al (2014) found that the vortex rope in the draft tube is the excitation source of resonance phenomenon, and due to the comprehensive excitation of rotation, cavitation, and fluid structure coupling effects of the vortex rope in the draft tube, a typical pressure pulsation characteristic of 1-3 times the rotational frequency was generated. Favrel et al (2014) found that the resonance phenomenon is mainly caused by the precession frequency of the vortex rope in the draft tube.…”

Section: Introductionmentioning

confidence: 99%

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Xiao,

Gui,

et al. 2024

Front. Energy Res.

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Pumped storage is an important component of electrified wire netting. The safe and stable operation of pump turbines is extremely important. Among them, pressure pulsation is one of the main causes of pump turbine vibration. The characteristics of pressure pulsation are relatively complex, and it is difficult to directly observe their temporal changes using commonly used FFT methods. The division of frequency characteristics is often vague. Meanwhile, it is difficult to explain some phenomena such as frequency doubling. This article focuses on a certain model of pump turbine and uses SST model to numerically simulate the runaway condition of the pump turbine. And the Hilbert Huang transform method is used to analyze the pressure pulsation in the vaneless region and draft tube. The results show that the main characteristic frequencies of the vaneless region are blade passing frequency 112.5 Hz and rotational frequency 12.5 Hz. The main characteristic frequencies of the draft tube are vortex rope frequency near 3 Hz which energy ratio is up to 50%, rotational frequency, and blade passing frequency. The pressure pulsation characteristics in the vaneless region have changed from a complex composition of double blade passing frequency and rotational frequency to a distribution dominated by blade passing frequency. In the passage of the guide vane, the pressure pulsation is almost only characterized by blade passing frequency. The frequency characteristics of the vaneless region between the runner and the guide vane become complex again. Meanwhile, the results show that the characteristic frequencies of the vaneless region and the draft tube propagate upstream and downstream.

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Section: Introductionmentioning

confidence: 99%

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Xiao,

Gui,

et al. 2024

Front. Energy Res.

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“…Among all operating points, and associated pulsation phenomena, one can distinguish the high part load (HPL) point with flow rate Q in the range 70-85% of Q opt . High frequency pressure pulsations of large amplitude, propagating along the whole hydraulic circuit can be observed in this point, see [1][2][3][4][5] among others. Experimental data, brought together in a recent paper of Dörfler [5], indicate that: 1079 (2022) 012088 IOP Publishing doi:10.1088/1755-1315/1079/1/012088 2 -HPL pulsations are longitudinal and synchronous; -the frequency of the pulsations is 1.5 to 4 times the runner rotation frequency f n ; -the amplitude and frequency of the pulsations depend on the Thoma number; in cavitation free regime no pulsations observed; -there is 180 degree phase shift between the entrance and the elbow of the draft tube; -the HPL pulsations were observed mainly in scale model tests, however in [4] they were reported also for a prototype machine.…”

Section: Introductionmentioning

confidence: 99%

Towards numerical simulation of high part load pulsations in Francis turbines

Чирков

Shcherbakov

Skorospelov

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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One of the most interesting operating points of Francis turbines is the high part load point, which is characterized by synchronous pressure pulsations of large amplitude. Physical mechanisms of these pulsations are not well understood. Experimental observations show that the frequency of the pulsations is 1.5 to 4 times higher than the runner rotation frequency and there exists a 180 degree phase shift of pressure signal measured in the spiral casing and in the draft tube. Numerical modeling this operating point is challenging as it has to account several complex phenomena: cavitation, rotating vortex rope and interaction of the turbine flow with the whole water system of the test rig. In the present paper we carried out a series of 1D-3D calculations of a model turbine in an attempt to simulate the high part load pulsations. 1D hydro-acoustic equations were used for the upstream waterways, while 3D Reynolds averaged Navier-Stokes model of two-phase mixture was used for the turbine. Although the main factors were taken into account, these computations were not able to capture the high part load pulsations. Namely, the frequency and amplitude of the pressure pulsations were significantly lower than those in the experiment, and there was no phase shift in turbine domain. In order to investigate the shortcomings of the present model, we considered a problem of propagation of disturbances in two-phase “liquid-gas” flows. Several 2D test cases were numerically investigated using both incompressible and compressible gaseous phase model. It was shown that in the absence of phase transfer the compressible model correctly represents the speed of sound in both homogeneous and stratified flow regimes. From the other hand, in case of phase transfer the model damps out propagation of pressure disturbances in upstream direction. This behavior explains the failure of the present 1D-3D model to correctly describe the acoustic properties of the two-phase flow in the draft tube, playing a crucial role in the development of high part load pulsations.

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“…As an example, free-form vortex-ropes are found in the draft tube with mainly low frequencies. [26][27][28][29] Hydraulic excitations are important indicators of the operation stability and security of hydraulic turbomachineries. As a result, the response of structures will be also crucial.…”

Section: Introductionmentioning

confidence: 99%

Influence of blade leaning on hydraulic excitation and structural response of a reversible pump turbine

Ouyang

Luo

Tao

2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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Blade leaning is commonly seen in the runner design of reversible pump turbines which operate under varying conditions. However, there is no certain law in determine the leaning mode and level. Considering performance, hydraulic excitation and structural response, five runners with strong rotational (RL+), rotational (RL), strong counter-rotational (CL+), counter-rotational (CL) and without (NL) blade leaning are compared under high-efficiency condition in pump mode and turbine mode. The head, efficiency, internal flow pressure pulsation and runner stress are comparatively studied. Among the five runners, CL+ runner is found has the highest efficiency as pump when RL+ runner has the highest efficiency as turbine. Pressure pulsation results show that the rotor-stator interaction region is the strongest pulsation source especially for runner and blade frequencies. In pump mode, pressure pulsation intensity decreases when blade leaning mode gradually changes from rotational to counter-rotational. In turbine mode, the NL runner has the strongest pressure pulsation intensity in runner and guide vane. Both rotational and counter-rotational leaning will reduce pressure pulsation. Velocity contours indicate that blade leaning will affect the velocity uniformity especially along rotational direction and cause stronger or weaker local hydraulic excitation. Under hydraulic excitation, RL+ runner suffers the highest equivalent stress as pump while CL runner suffers the highest equivalent stress as turbine. From rotational to counter-rotational blade leaning, the maximum stress moves on the crown from low pressure side to high pressure side. Considering hydraulic excitation and structural response, the strong counter-rotational leaning blade is found better in reversible runner design.

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Model and prototype investigations of upper partial load unsteady phenomena on the Francis turbine designed for head up to 120 m

Cited by 4 publications

References 1 publication

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Towards numerical simulation of high part load pulsations in Francis turbines

Influence of blade leaning on hydraulic excitation and structural response of a reversible pump turbine

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