scholarly journals Numerical prediction of pressure pulsation amplitude for different operating regimes of Francis turbine draft tubes

2009 ◽  
Vol 2 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Andrej Lipej ◽  
Dragica Jost ◽  
Peter Meznar ◽  
Vesko Djelic
Keyword(s):  
Pressure Pulsation ◽  
Numerical Prediction ◽  
Francis Turbine ◽  
Pulsation Amplitude ◽  
Draft Tubes ◽  
Operating Regimes

Two Phase PIV Measurements at the Runner Outlet in a Francis Turbine

2003 ◽  
Author(s):  
Monica Sanda Iliescu ◽  
Gabriel Dan Ciocan ◽  
Franc¸ois Avellan
Keyword(s):  
Francis Turbine ◽  
Cavitation Flow ◽  
Two Phase ◽  
Piv Measurements ◽  
Turbine Runner ◽  
Physical Insight ◽  
Complex Phenomena ◽  
Hydro Turbines ◽  
Operating Regimes ◽  
Averaging Techniques

Part load operation of hydro turbines with fixed pitch blades causes complex instable cavitation flow in the diffuser cone. Application of PIV systems provides the opportunity to investigate the flow velocity and turbulent fields in the case of development of cavitation vortex, the so-called turbine rope, at the outlet of a Francis turbine runner. The synchronization of the PIV flow survey with the rope precession allows to apply phase averaging techniques in order to extract both the periodic velocity components and the rope layout. The influence of the turbine setting level on the volume of the cavity rope and its center is investigated, providing a physical insight on the hydrodynamic complex phenomena involved in the development of the cavitation rope at Francis turbine operating regimes.

Comparison of Axial Water and Air Injections in the Draft Tube of a Francis Turbine for RVR Mitigation

2021 ◽  
Author(s):  
Subodh Khullar ◽  
Krishna M. Singh ◽  
Michel J. Cervantes ◽  
Bhupendra K. Gandhi
Keyword(s):  
Pressure Pulsation ◽  
Draft Tube ◽  
Water Injection ◽  
Air Injection ◽  
Flow Instabilities ◽  
Pressure Recovery ◽  
Francis Turbine ◽  
Tube Flow ◽  
Pressure Pulsations ◽  
Jet Injection

Abstract The presence of excessive swirl at the runner outlet in Francis turbines operating at part load leads to the development of flow instabilities such as the rotating vortex rope (RVR). The presence of RVR causes severe pressure pulsations, power swings, and fatigue damage in the turbine unit. Air and water injection in the draft tube have been reported to reduce the detrimental effects of RVR formation in the Francis turbines. Air injection is one of the oldest and most widely used methods. In contrast, water jet injection is a relatively new methodology. The present work reports the numerical simulations performed to compare the respective effectiveness of these methods to mitigate the RVR and the related flow instabilities. The efficacy of the two methods has been compared based on the pressure pulsations and pressure recovery in the draft tube cone. The results show that the air and water injection influence the draft tube flow field in different ways. Both air and water injection led to a reduction in pressure pulsation magnitudes in the draft tube cone. However, the air injection led to a negative pressure recovery while the water injection improved the draft tube action.

Effects of Trailing Edge Position of Splitter Blade on the Pressure Pulsation in a Low Specific Centrifugal Pump

2019 ◽  
Author(s):  
Jinfeng Zhang
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Pressure Fluctuation ◽  
Relative Velocity ◽  
Pressure Pulsation ◽  
Suction Side ◽  
Maximum Pressure ◽  
Trailing Edge ◽  
Flow Rates ◽  
Pulsation Amplitude

Abstract A combination of experimental and numerical simulation was carried out to analyze influence of trailing edge position of splitter blade on the pressure fluctuation in low specific pumps with and without splitter blades under different flow rates. Performance experiments and PIV tests were performed to verify the results of numerical calculation. Several monitor points were placed in the calculation model pump to collect the pressure fluctuation signals, which were processed by Fast Fourier Transform to obtain the frequency results for further analysis. Besides, turbulence intensity and relative velocity distribution were also analyzed in regions of impeller and volute. The results showed that compared with prototype without splitter blade and the splitter blade schemes, when the trailing edge of splitter blade deviates to the suction side of main blade, the maximum pressure pulsation amplitudes are the lowest at different monitoring points of model pump. And the variation of pressure pulsation amplitude in this scheme is relatively stable with the change of flow rates compared with other schemes. Furthermore, the splitter blade scheme with an appropriate trailing edge position has the lowest average turbulence intensity and optimal relative velocity distribution in main flow passage component. Therefore, this paper proposes a reference scheme of the trailing edge position of the splitter blade to effectively decrease predominate pressure pulsation amplitude.

Numerical Prediction of Cavitation Erosion on a Francis Turbine Runner

2013 ◽  
Vol 655-657 ◽  
pp. 449-456
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Cavitation Erosion ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Numerical Prediction ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Transfer Model ◽  
Cavitation Damage ◽  
Turbine Runner

The paper presents numerical prediction of cavitation erosion on a Francis turbine runner using CFD code. The SST turbulence model is employed in the Reynolds averaged Navier–Stokes equations in this study. A mixture assumption and a finite rate mass transfer model were introduced. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations of the mixture model and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators(PISO) procedure. Comparison the numerical prediction results with a real runner with cavitation damage, the region of higher volume fraction by simulation with the region of runner cavitation damage is consistent.

scholarly journals Effect of Air Admission on Pressure Pulsation in a Francis Turbine

2014 ◽  
Vol 10 (4) ◽  
pp. 9-15
Author(s):  
Yunheung Jeon ◽  
Sihoon Park ◽  
Hansu Choi ◽  
Jungwan Park
Keyword(s):  
Pressure Pulsation ◽  
Francis Turbine

Numerical investigation of the effects of splitter blade deflection on the pressure pulsation in a low specific speed centrifugal pump

2019 ◽  
Vol 234 (4) ◽  
pp. 420-432 ◽  
Author(s):  
Jinfeng Zhang ◽  
Guidong Li ◽  
Jieyun Mao ◽  
Shouqi Yuan ◽  
Yefei Qu ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Pressure Fluctuation ◽  
Relative Velocity ◽  
Pressure Pulsation ◽  
Maximum Pressure ◽  
Flow Rates ◽  
Pulsation Amplitude ◽  
Low Specific Speed ◽  
Specific Speed

A combination of experimental and numerical simulation was carried out to analyze the influences of the splitter blade deflection on the performance and pressure fluctuation in low specific speed pumps with and without splitter blades under different flow rates. Performance experiments and particle image velocimetry (PIV) tests were performed to verify the results of the numerical calculation. Several monitoring points were placed in the calculation model pump to collect the pressure fluctuation signals, which were processed by Fast Fourier Transform to obtain the frequency results for further analysis. In addition, turbulence intensity and relative velocity distribution were also analyzed in the regions of the impeller and volute. The results showed that compared with a prototype without a splitter blade and the splitter blade schemes, the maximum pressure pulsation amplitudes are the lowest at different monitoring points of the model pump when the splitter blade deflects to the suction side of the main blade. The variation of pressure pulsation amplitude in this scheme is relatively stable with the change of flow rates compared with other schemes. Furthermore, the impeller scheme with an appropriate deflection of the splitter blade has the lowest turbulence intensity and optimal relative velocity distribution in the main flow passage. Therefore, this paper proposes a reference scheme of the impeller with the splitter blade to effectively decrease the predominate pressure pulsation amplitude.

scholarly journals An Experimental Study on the Jet Pressure Performance of Organ–Helmholtz (O-H), Self-Excited Oscillating Nozzles

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 367
Author(s):  
Xiaochuan Wang ◽  
Yueqin Li ◽  
Yi Hu ◽  
Xiaolong Ding ◽  
Meijing Xiang ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Peak Pressure ◽  
Structural Parameters ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Target Distance ◽  
Pulsation Amplitude ◽  
Excited Oscillation ◽  
Organ Pipe ◽  
Pump Pressure

To make a better application of the self-excited oscillation jet, a compound organ–Helmholtz oscillation nozzle (OH nozzle) was designed to generate better pulse effects in the present study. The effects of geometric parameters on pressure characteristics of self-excited oscillation jets were investigated experimentally. The geometric parameters of OH nozzles were determined based on the design principle of the organ-pipe and Helmholtz nozzles. Various types of OH nozzles were tested to obtain the relationship between oscillation pressure and geometric parameters. Experimental results showed that some structural parameters are sensitive to the pump pressure, while others are not. The optimum geometric optimum parameters were obtained based on experimental results. The peak pressure and pressure pulsation amplitude are closely related to the target distance. The peak pressure decreases sharply with target distance at first and decreases with a further increase of the target distance. The peak pressure becomes stable beyond a certain range of target distance. With the increase of the target distance, the pressure pulsation amplitude increases at first and then decreases. The optimum target distance was determined based on experimental results to achieve better pulsation performance and has a value of 20 mm in the present study.

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