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

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.

scholarly journals Pressure Pulsation in a High Head Francis Turbine Operating at Variable Speed

2018 ◽  
Vol 1042 ◽  
pp. 012005
Author(s):  
D. B. Sannes ◽  
I. Iliev ◽  
E. Agnalt ◽  
O. G. Dahlhaug
Keyword(s):  
Pressure Pulsation ◽  
Francis Turbine ◽  
Variable Speed ◽  
High Head

scholarly journals Analysis of Flow Field Characteristics and Pressure Pulsation in Horizontal Axis Double-Runner Francis Turbine

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2671
Author(s):  
Chunxia Yang ◽  
Jiawei Wu ◽  
Dinge Xu ◽  
Yuan Zheng ◽  
Xueyuan Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Horizontal Axis ◽  
Francis Turbine ◽  
Back Surface ◽  
Average Efficiency ◽  
Flow Field Characteristics ◽  
The Relationship

Horizontal axis double-runner Francis turbines have great advantages in the development of small hydropower plants, but the arrangement of double runners aggravates the complexity of the water flow between runners, and the mutual influence of the two runners cannot be ignored. In order to explore the relationship between the performance and the internal flow field and investigate the pressure pulsation characteristics of the double-runner Francis turbine, the steady and unsteady numerical analysis of the full flow channel of a prototype turbine was carried out based on the Realizable k-epsilon model and the polyhedral mesh method. The results show that the relationship between the average efficiency of the two runners and the flow difference between the runners is negatively correlated. As the flow rate difference between the runners on both sides increases, the average efficiency of the runners decreases. The draft tube flow of a horizontal-axis turbine has a profound effect on the flow field characteristics in the runner. When the working conditions change, the turning and converging timing of the mainstream at the outlet of the two runners will change. The movement of the mainstream promotes the change in location of the dead water zone. The existence of the vortex zone makes the pressure distribution at the outlet of the runner uneven, which is an important reason for the asymmetry of the flow in the runner. The analysis of pressure pulsation and its frequency spectrum shows that when the working conditions change, the low-frequency, strong pressure pulsation area on the surface of the guide vane will regularly migrate between the two runners, while the high-frequency pressure pulsation that occurs in the bladeless zone will dissipate in the runner. The doubling of the blade frequency on the pressure surface and back surface of the blades gradually attenuates with the increase of frequency. The pressure pulsation attenuation on the surface of the high-position blade conforms to the linear law, and the attenuation of the pressure pulsation on the surface of the low-position blade conforms to the exponential law. The research in this paper provides a certain reference value for revealing the flow field mechanism and pressure pulsation characteristics of the double-runner Francis turbine.

scholarly journals Research on Unsteady Hydraulic Features of a Francis Turbine and a Novel Method for Identifying Pressure Pulsation Transmission Path

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1216 ◽  
Author(s):  
Shuo Wang ◽  
Liaojun Zhang ◽  
Guojiang Yin ◽  
Chaonian Guan
Keyword(s):  
Pressure Pulsation ◽  
Guide Vane ◽  
Fluid Pressure ◽  
Flow Channel ◽  
Transfer Entropy ◽  
Francis Turbine ◽  
Transmission Path ◽  
Hydropower House ◽  
Entire Flow ◽  
Novel Method

It is of significant value to understand the unsteady hydraulic features and pressure pulsation transmission path in the flow channel through a turbine for providing technical support for turbine design and optimization, as well as laying a foundation for analysis of the stability and the coupled vibration of the hydropower house. In this paper, a three-dimensional mechanics–hydraulics–concrete structure coupled numerical model was established to accurately simulate Francis hydraulic machinery, including the high-rotating turbine runner and fixed guide vane, the unsteady flowing water, the structure of the entire flow channel, as well as the dynamic interaction between them. Turbulent hydraulic features of flow condition and pressure pulsation in design operation were explored using the detached eddy simulation (DES) turbulence model. Then, a novel method was proposed to identify the fluid pressure pulsation transmission path based on the time-delayed transfer entropy method and wavelet theory. On basis of time and frequency analysis of pressure calculation results, investigation into identification of pressure pulsation transmission path was performed using the method of traditional transfer entropy and the method adopted in this paper. The pressure pulsation transmission features in the entire flow channel were revealed during operation of the large-scale Francis turbine. The research method and results could not only lay a basis for exploring the structural vibration regularity of the hydropower house but also provide a scientific reference for vibration reduction design of the hydropower house.

Experimental and Numerical Analysis of Pressure Pulsation in Francis Turbine

2008 ◽  
Author(s):  
Yexiang Xiao ◽  
Zhengwei Wang ◽  
Zongguo Yan ◽  
Yongyao Luo ◽  
Ruofu Xiao ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Flow Pattern ◽  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Draft Tube ◽  
Flow Distribution ◽  
Internal Flow ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Spiral Case

The pressure fluctuation taking place at the whole passage of a prototype Francis hydraulic turbine is studied by carrying out both experimental and numerical simulation. Unsteady wall pressure measurements at six different typical operating conditions are performs to thoroughly investigate pressure fields in the spiral case and straight draft tube dynamically. 3-D unsteady turbulent simulations are performed and compared to the experimental data. The computed flow domain includes the spiral case, stay vanes, guide vanes, rotating runner and the draft tube. The characteristic of unsteady flow and the pressure pulsation as well as their relationships are discussed in this paper, which also analyzed the correlation between the unsteady flow pattern and the pressure fluctuation at different parts of the turbine. In order to optimize the internal flow distribution in Francis turbines at partial loads, this paper presents some preliminary methods to control the unsteady flow pattern.

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