2020
Wang, Wenjie; Pavesi, Giorgio; Pei, Ji; Yuan, Shouqi
Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode Journal Article
In: Renewable Energy, vol. 145, pp. 1817-1830, 2020, ISSN: 09601481.
Abstract | Links | BibTeX | Tags: Closure of Wicket Gate, Dynamic Mesh, Energy storage, Francis-type Reversible Turbine, PHES, power reduction scenario, Pumped-hydro energy storage plant, transient flow
@article{Wang2020,
title = {Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode},
author = {Wenjie Wang and Giorgio Pavesi and Ji Pei and Shouqi Yuan},
url = {https://doi.org/10.1016/j.renene.2019.07.052},
doi = {10.1016/j.renene.2019.07.052},
issn = {09601481},
year = {2020},
date = {2020-01-01},
journal = {Renewable Energy},
volume = {145},
pages = {1817-1830},
abstract = {To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.},
keywords = {Closure of Wicket Gate, Dynamic Mesh, Energy storage, Francis-type Reversible Turbine, PHES, power reduction scenario, Pumped-hydro energy storage plant, transient flow},
pubstate = {published},
tppubtype = {article}
}
To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.
2018
Xiuli, Mao; Giorgio, Pavesi; Yuan, Zheng
Francis-Type reversible turbine field investigation during fast closure of wicket gates Journal Article
In: Journal of Fluids Engineering, Transactions of the ASME, vol. 140, iss. 6, pp. 061103, 2018, ISSN: 00982202.
Abstract | Links | BibTeX | Tags: Dynamic Mesh, Francis-type Reversible Turbine, Load rejection, transient flow
@article{Xiuli2018a,
title = {Francis-Type reversible turbine field investigation during fast closure of wicket gates},
author = {Mao Xiuli and Pavesi Giorgio and Zheng Yuan},
doi = {10.1115/1.4039089},
issn = {00982202},
year = {2018},
date = {2018-01-01},
journal = {Journal of Fluids Engineering, Transactions of the ASME},
volume = {140},
issue = {6},
pages = {061103},
abstract = {Flexible electricity demand and variability of the electricity produced by wind turbines and photovoltaic affect the stable operations of power grids. Pump-Turbines are used to stabilize the power grid by maintaining a real-Time electricity demand. Consistently, the machines experience transient conditions during the course of operation, such as startup, load acceptance, load rejection, and shutdown, which induce high amplitude pressure pulsations and affect operating lifespan of the components. During the closure of the wicket gates, the transient flow characteristics is analyzed for a Francis-Type reversible pump-Turbine in generating mode by three-dimensional (3D) numerical simulation with a moving mesh technique and using detached eddy simulation (DES) turbulent model. Mesh motion is carried out in the region of wicket gates during the load rejection by a moving, sliding mesh, which makes dynamic flow simulation available, instead of building various steady models with different guide vanes angles. The transient flow characteristics are illustrated by analyzing the flow, torque, and pressure fluctuations signals by frequency and time-frequency analyses. The flow field analysis includes the onset and strengthening of unsteady phenomena during the turbine load reduction. The flow pattern in return channel maintained a quite stable flow field, whereas the flow pattern in the runner and draft tube emphasized its instability with the flow rate decreased. Influence of 3D unsteady flow structures on runner is determined, and its evolution is characterized spectrally during fast closure of wicket gates. © 2018 by ASME.},
keywords = {Dynamic Mesh, Francis-type Reversible Turbine, Load rejection, transient flow},
pubstate = {published},
tppubtype = {article}
}
Flexible electricity demand and variability of the electricity produced by wind turbines and photovoltaic affect the stable operations of power grids. Pump-Turbines are used to stabilize the power grid by maintaining a real-Time electricity demand. Consistently, the machines experience transient conditions during the course of operation, such as startup, load acceptance, load rejection, and shutdown, which induce high amplitude pressure pulsations and affect operating lifespan of the components. During the closure of the wicket gates, the transient flow characteristics is analyzed for a Francis-Type reversible pump-Turbine in generating mode by three-dimensional (3D) numerical simulation with a moving mesh technique and using detached eddy simulation (DES) turbulent model. Mesh motion is carried out in the region of wicket gates during the load rejection by a moving, sliding mesh, which makes dynamic flow simulation available, instead of building various steady models with different guide vanes angles. The transient flow characteristics are illustrated by analyzing the flow, torque, and pressure fluctuations signals by frequency and time-frequency analyses. The flow field analysis includes the onset and strengthening of unsteady phenomena during the turbine load reduction. The flow pattern in return channel maintained a quite stable flow field, whereas the flow pattern in the runner and draft tube emphasized its instability with the flow rate decreased. Influence of 3D unsteady flow structures on runner is determined, and its evolution is characterized spectrally during fast closure of wicket gates. © 2018 by ASME.
Pavesi, Giorgio; Xie, Zhanshan; Zheng, Yuan; Ge, Xinfeng; Mao, Xiu-li; Zheng, Yuan
A new method of dynamic mesh used in continuous guide vane closure of a reversible pump-turbine in generating mode Journal Article
In: Journal of Hydrodynamics, vol. 30, iss. 5, pp. 828-836, 2018, ISSN: 1001-6058.
Abstract | Links | BibTeX | Tags: Dynamic Mesh, Flow characteristics, Francis-type Reversible Turbine, Guide Vane Closure
@article{Pavesi2018b,
title = {A new method of dynamic mesh used in continuous guide vane closure of a reversible pump-turbine in generating mode},
author = {Giorgio Pavesi and Zhanshan Xie and Yuan Zheng and Xinfeng Ge and Xiu-li Mao and Yuan Zheng},
doi = {10.1007/s42241-018-0146-y},
issn = {1001-6058},
year = {2018},
date = {2018-01-01},
urldate = {2018-01-01},
journal = {Journal of Hydrodynamics},
volume = {30},
issue = {5},
pages = {828-836},
publisher = {Springer Nature},
abstract = {In this paper, a new method of dynamic mesh based on two functional controls is used in continuous guide vane closure, three-dimensional numerical simulation is carried out to investigate the transient flow characteristics for a Francis-type reversible pump-turbine under turbine mode in the load regulation scenario. Detached Eddy Simulation (DES) turbulent model is adopted. The transient flow characteristics during the closure of guide vanes are illustrated by analyzing the signals of mass flow, torque and pressure fluctuations in frequency and time-frequency domains. It is shown by simulating results that continuously assessment of the transient flow characteristics during guide vane closure is available by using the new method of dynamic mesh. Furthermore, the flow field analysis contains both the onset and the development of unsteady phenomena progressively based on an organized guide vane closure law. The flow pattern in return channel maintains a relatively stable flow field before the last stage of closure, compared with the unstable flow field in other domains. To identify the fluid-dynamical conditions causing unit variation, the influence of three-dimensional unsteady flow structures in passage is analyzed and its evolution during this transient process is characterized fluid-dynamically and spectrally.},
keywords = {Dynamic Mesh, Flow characteristics, Francis-type Reversible Turbine, Guide Vane Closure},
pubstate = {published},
tppubtype = {article}
}
In this paper, a new method of dynamic mesh based on two functional controls is used in continuous guide vane closure, three-dimensional numerical simulation is carried out to investigate the transient flow characteristics for a Francis-type reversible pump-turbine under turbine mode in the load regulation scenario. Detached Eddy Simulation (DES) turbulent model is adopted. The transient flow characteristics during the closure of guide vanes are illustrated by analyzing the signals of mass flow, torque and pressure fluctuations in frequency and time-frequency domains. It is shown by simulating results that continuously assessment of the transient flow characteristics during guide vane closure is available by using the new method of dynamic mesh. Furthermore, the flow field analysis contains both the onset and the development of unsteady phenomena progressively based on an organized guide vane closure law. The flow pattern in return channel maintains a relatively stable flow field before the last stage of closure, compared with the unstable flow field in other domains. To identify the fluid-dynamical conditions causing unit variation, the influence of three-dimensional unsteady flow structures in passage is analyzed and its evolution during this transient process is characterized fluid-dynamically and spectrally.
