Impact of Different Operating Conditions on the Dynamic Excitation of a High Head Francis Turbine

2016 ◽  
Author(s):  
Markus Eichhorn ◽  
Eduard Doujak
Keyword(s):  
Fatigue Analysis ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Fluid Structure Interactions ◽  
Cfd Simulations ◽  
Dynamic Excitation ◽  
Hydropower Plants ◽  
Rotor Stator Interaction ◽  
High Head ◽  
Strain Gauge Measurements

Fatigue analysis becomes more important in the design phase of Francis turbine runners due to the changing requirements on hydropower plants, affected by the increasing amount of volatile energy sources. Francis turbines are operated more often and over longer periods of time at off-design conditions to provide regulating power to the electric grid. The lifetime of a Francis runner depends mainly on the dynamic excitation induced by unsteady pressure pulsations like the rotor-stator interaction or draft tube vortex ropes. An approach using one-way coupled fluid-structure interactions has been developed and is now extended using unsteady CFD simulations as well as harmonic and transient FEM computations. The results are compared to strain gauge measurements on the according high head Francis turbine to validate the overall procedure. The investigations should be further used to perform a fatigue analysis and to examine the applicability for lifetime investigations on Francis machines with different specific speeds.

Numerical analysis of unsteady flow under high‐head operating conditions in Francis turbine

2010 ◽  
Vol 27 (3) ◽  
pp. 365-386 ◽  
Author(s):  
Xiao Yexiang ◽  
Wang Zhengwei ◽  
Yan Zongguo ◽  
Li Mingan ◽  
Xiao Ming ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Unsteady Flow ◽  
Operating Conditions ◽  
Francis Turbine ◽  
High Head

Investigations of Compressible Turbulent Flow in a High-Head Francis Turbine

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Chirag Trivedi
Keyword(s):  
Compressible Flow ◽  
Incompressible Flow ◽  
Draft Tube ◽  
Francis Turbine ◽  
Accurate Estimation ◽  
Compressibility Effect ◽  
Numerical Errors ◽  
Rotor Stator Interaction ◽  
High Head ◽  
Runner Design

Dynamic stability of the high-head Francis turbines is one of the challenging problems. Unsteady rotor–stator interaction (RSI) develops dynamic stresses and leads to crack in the blades. In a high-head turbine, vaneless space is small and the amplitudes of RSI frequencies are very high. Credible estimation of the amplitudes is vital for the runner design. The current study is aimed to investigate the amplitudes of RSI frequencies considering a compressible flow. The hydro-acoustic phenomenon is dominating the turbines, and the compressibility effect should be accounted for accurate estimation of the pressure amplitudes. Unsteady pressure measurements were performed in the turbine during the best efficiency point (BEP) and part load (PL) operations. The pressure data were used to validate the numerical model. The compressible flow simulations showed 0.5–3% improvement in the time-averaged pressure and the amplitudes over incompressible flow. The maximum numerical errors in the vaneless space and runner were 6% and 10%, respectively. Numerical errors in the instantaneous pressure amplitudes at the vaneless space, runner, and draft tube were ±1.6%, ±0.9%, and ±1.8%, respectively. In the draft tube, the incompressible flow study showed the pressure amplitudes up to eight times smaller than those of the compressible. Unexpectedly, the strong effect of RSI was seen in the upper and lower labyrinth seals, which was absent for the incompressible flow.

Experimental and Numerical Studies for a High Head Francis Turbine at Several Operating Points

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Chirag Trivedi ◽  
Michel J. Cervantes ◽  
B. K. Gandhi ◽  
Ole G. Dahlhaug
Keyword(s):  
Power Generation ◽  
Entire Range ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Head Model ◽  
Numerical Studies ◽  
Pressure Time ◽  
Advection Schemes ◽  
High Head

Experimental and numerical studies on a high head model Francis turbine were carried out over the entire range of turbine operation. A complete Hill diagram was constructed and pressure-time measurements were performed at several operating conditions over the entire range of power generation by installing pressure sensors in the rotating and stationary domains of the turbine. Unsteady numerical simulations were performed at five operating conditions using two turbulent models, shear stress transport (SST) k-ω and standard k-ε and two advection schemes, high resolution and second order upwind. There was a very small difference (0.85%) between the experimental and numerical hydraulic efficiencies at the best efficiency point (BEP); the maximum difference (14%) between the experimental and numerical efficiencies was found at lower discharge turbine operation. Investigation of both the numerical and experimental pressure-time signals showed that the complex interaction between the rotor and stator caused an output torque oscillation over a particular power generation range. The pressure oscillations that developed due to guide vanes and runner blades interaction propagate up to the trailing edge of the blades. Fourier analysis of the signals revealed the presence of a vortex rope in the draft tube during turbine operation away from the BEP.

Fatigue analysis of a prototype Francis turbine based on strain gauge measurements

2019 ◽  
Vol 109 (S1) ◽  
pp. 66-71 ◽  
Author(s):  
Julian Unterluggauer ◽  
Eduard Doujak ◽  
Christian Bauer
Keyword(s):  
Strain Gauge ◽  
Fatigue Analysis ◽  
Francis Turbine ◽  
Strain Gauge Measurements

scholarly journals Investigation of a High Head Francis Turbine at Runaway Operating Conditions

Energies ◽  
2016 ◽  
Vol 9 (3) ◽  
pp. 149 ◽  
Author(s):  
Chirag Trivedi ◽  
Michel Cervantes ◽  
B. Gandhi
Keyword(s):  
Operating Conditions ◽  
Francis Turbine ◽  
High Head

The Strength Analysis of Francis Turbine Runner Based on the Fluid-Solid Coupling

2014 ◽  
Vol 709 ◽  
pp. 41-45
Author(s):  
Kan Kan ◽  
Yuan Zheng ◽  
Xin Zhang ◽  
Bin Sun ◽  
Hui Wen Liu
Keyword(s):  
Water Pressure ◽  
Eastern China ◽  
Static Stress ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Strength Analysis ◽  
Maximum Deformation ◽  
The North ◽  
North Eastern ◽  
Turbine Runner

This paper does unidirectional fluid-solid coupling calculation on the runner strength under three designed head loading conditions of a certain Francis turbine in the north-eastern China. The water pressure on the blade in the flow fields of different operating conditions is calculated by means of CFD software CFX. With the help of ansys workbench, the water pressure is loaded to the blade as structural load to conclude the static stress distribution and deformation of the runner under different operating conditions. The results show that the maximum static stress increases with the rise of the flow and appears near the influent side of the blade connected to the runner crown; the maximum deformation increases with the rise of the flow and appears on the band. The results provides effective basis for the structural design and safe operation of the Francis turbine.

scholarly journals Aerodynamic Analysis of Multistage Turbomachinery Flows in Support of Aerodynamic Design

1999 ◽  
Author(s):  
John J. Adamczyk
Keyword(s):  
Unsteady Flow ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Environment ◽  
Cfd Simulations ◽  
Average Flow ◽  
Flow Models ◽  
Time Average ◽  
Semi Empirical ◽  
Future Work

This paper summarizes the state of 3D CFD based models of the time average flow field within axial flow multistage turbomachines. Emphasis is placed on models which are compatible with the industrial design environment and those models which offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models which are free of aerodynamic input from semi-empirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial flow multistage machinery are presented along with procedures which can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines which help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time average flow models.

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