scholarly journals Three-Dimensional CFD Simulations of Start-Up Processes of a Pump-Turbine Considering Governor Regulation

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8507
Author(s):  
Zhiyan Yang ◽  
Yongguang Cheng ◽  
Ke Liu ◽  
Xiaoxia Hou ◽  
Xiaoxi Zhang ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Three Dimensional ◽  
Load Condition ◽  
Internal Flow ◽  
Pump Turbine ◽  
Characteristic Region ◽  
Start Up ◽  
Speed Fluctuation ◽  
Pumped Storage ◽  
Cfd Method

The pumped-storage power station is an efficient stability regulator of the power grid. However, due to the instability of the pump-turbine in the S-shaped characteristic region, rotational speed fluctuation is easy to occur in the speed no-load condition, making synchronization with and connection to the grid difficult. To investigate the key factors of these difficult grid connections, the start-up processes of a practical pump-turbine under the lowest head condition were simulated by using the three-dimensional CFD method, in which the governor regulating equations with different regulating parameters were integrated successfully. The results show that the working points oscillate with the fluctuations of rotational speed, discharge, and torque, and different regulating parameters have a significant influence on the dynamic histories. In addition, the internal flow patterns, especially the backflows at the runner inlet, keep apparent values at the middle span (0.5 span) but have regular transitions near the shroud side (0.7–0.8 span). The faster the guide vanes adjust, the faster the backflows change, and the larger the macro parameters fluctuate. Overall, the instability of the start-up is the result of the periodical evolutions of backflows at the runner inlet, because the trend and period of the radial velocities at different inlet span locations are consistent with those of the discharge.

scholarly journals Computational Analysis on Numerical Simulation of Internal Flow Physics for Pump as Turbine in Renewable Small Hydro Energy Generation

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Du Jianguo ◽  
Daniel Adu ◽  
Emmanuel Acheaw ◽  
Shakir Hafeez ◽  
Eric Ofosu Antw
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Human Life ◽  
Three Dimensional ◽  
Internal Flow ◽  
Hydroelectric Power ◽  
Small Hydropower ◽  
Speed Increase ◽  
Blade Thickness ◽  
The Impact

Energy contributes significantly in almost all aspects of human life as well as economic activities and plays a crucial role in the infrastructural development of a county to alleviate poverty. Generating energy from a renewable source such as small hydropower through the application of pump operating as a turbine mode called Pump as Turbine is one of the best alternatives to provide clean and inexpensive energy. Using Pump as Turbine helps in generating reasonably priced hydroelectric power for communities in underdeveloped counties. This study investigates the effects of internal flow behaviour and performance of Pump as Turbine under different rotational speed and flow rate. The rotational speed is an essential physical parameter as it affects the Pump as Turbine operation. A model-specific speed centrifugal pump model with head 32 (m), flow rate of 12.5 (m3/h) and the rotational speed of 2900 rpm, has been selected for the study. Numerical simulations have been conducted using the k-ω turbulence model to solve three-dimensional (3D) equations. The pump mode experimental data were used to confirm the results for better analysis. The results predicted that vortex and turbulent kinetic energy increase per rotational speed increase. Also, at the higher rotational speed, very high recirculation of flow is detected at the blade suction chamber, although the pressure side has a smooth flow. This study provides beneficial information which will serve as a reference to help improve PAT performance along with selecting PAT for a small hydropower site. Future works will consider the impact of blade thickness and cavitation in Pump as Turbine.

Deriaz Type Reversible Pump-Turbine Installation at Sir Adam Beck-Niagara Forebay Pumped Storage Project

1959 ◽  
Vol 81 (4) ◽  
pp. 505-515
Author(s):  
A. E. Aeberli
Keyword(s):  
Mechanical Design ◽  
Operating Conditions ◽  
Pump Turbine ◽  
Niagara River ◽  
Performance Requirements ◽  
Start Up ◽  
Pumped Storage ◽  
Tail Water ◽  
Power Project ◽  
Turbine Installation

This paper describes the new adjustable blade, single-speed, vertical, single-runner reversible pump-turbine units recently developed and placed into service at Ontario Hydro’s forebay storage pumping-generating station at the S.A.B. Power Project on the Niagara River. The units operate under unusual variations in head. In the pumping sequence the limits are 59 and 90 ft and in the turbine cycle from 45 to 85 ft. Tailwater depression is not required on start-up. Change-over from turbine to pumping sequence is accomplished in a matter of minutes and occurs several times each day. Data are given on the performance requirements for capacity and efficiency versus hydraulic operating conditions of head, tail water, and forebay reservoir levels. Information in the paper includes unusual features of mechanical design.

Flow Analysis of the Guide Vanes Region of Pump Turbine at the Slight Opening in the Pumping Startup Process

2016 ◽  
Author(s):  
Honggang Fan ◽  
Qingfeng Ji ◽  
Weili Liao ◽  
Haixia Yang
Keyword(s):  
Guide Vane ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Main Flow ◽  
Three Dimensional Model ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Abrupt Changes ◽  
Dimensional Simulation ◽  
Pumped Storage

The unit of a Pumped Storage Power Station experienced abnormal noise and vibration in the guide vanes at the slight opening when the pump turbine was in the process of startup in the pumping mode. Based on this phenomena, the three dimensional model of the pump turbine was established, RNG k-epsilon two equations turbulence model was selected for the flow numerical simulation in the pump turbine because this model can simulate both the flow separation and vortex dynamics, and it is more accurate in the near wall areas. The governing equations were discretized with the finite volume method. The computation was carried out with three steps, 1.steady calculation, 2.unsteady calculation with constant guide vane opening, 3.unsteady calculations with the increase of the opening of guide vanes, by using the results of the last step as the initial condition. According to the three dimensional simulation results, the main flow between the guide vanes was deflected from attaching to the one vane to the other vane with the opening of the guide vanes. The calculation of complete 3D flow indicated that the deflections of the flows between the different adjacent guide vanes were basically the same, however, the deflections starting times had a few differences. The variation of the torque on the guide vane was also investigated, and the results shown the abrupt changes occurred during the deflection process of the main flow. When the torque produced by the servomotor cannot adapt quickly enough to the abrupt changes, the vibration and loud scrape noise might occur.

scholarly journals Investigation on Dynamic Stresses of Pump-Turbine Runner during Start Up in Turbine Mode

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 499
Author(s):  
Funan Chen ◽  
Huili Bi ◽  
Soo-Hwang Ahn ◽  
Zhongyu Mao ◽  
Yongyao Luo ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Unsteady Flow ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Leading Edge ◽  
Complex Flow ◽  
Dynamic Stresses ◽  
Start Up ◽  
Pumped Storage ◽  
Turbine Mode

The startup process occurs frequently for pumped storage units. During this process, the rotating rate that changes rapidly and unsteady flow in runner cause the complex dynamic response of runner, sometimes even resonance. The sharp rise of stress and the large-amplitude dynamic stresses of runner will greatly shorten the fatigue life. Thus, the study of start-up process in turbine mode is critical to the safety operation. This paper introduced a method of coupling one dimensional (1D) pipeline calculation and three-dimensional computational dynamics (3D CFD) simulation to analyze transient unsteady flow in units and to obtain more accurate and reliable dynamic stresses results during start up process. According to the results, stress of the ring near fixed support increased quickly as rotating rate rose and became larger than at fillets of leading edge and band in the later stages of start-up. In addition, it was found that dynamic response can be caused by rotor stator interaction (RSI), but also could even be generated by the severe pressure fluctuation in clearance, which can also be a leading factor of dynamic stresses. This study will facilitate further estimation of dynamic stresses in complex flow and changing rotating rate cases, as well as fatigue analysis of runner during transient operation.

Mechanism and influence factors of hydraulic fluctuations in a pump-turbine

2021 ◽  
pp. 095765092110285
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Xianzhu Wei
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Influence Factors ◽  
Simulation Method ◽  
Power Station ◽  
Pump Turbine ◽  
Available Energy ◽  
Exciting Forces ◽  
Pump Storage Power ◽  
Pumped Storage

Pumped-storage power technology is currently the only available energy storage technology in the grid net, and its reliability is receiving attention increasingly. However, when a pump-turbine unit undergoes runaway transitions, hydraulic fluctuations intensively affect the reliable operation of a pumped-storage power station. To reduce hydraulic fluctuations, this study investigated the formation mechanism of hydraulic fluctuations and explored its influence factors. In this study, a developed one-dimensional and three-dimensional (1 D-3D) coupling simulation method was adopted. Transient runaway transitions of a pump-turbine with three different inertias (0.5 J, 1 J, and 2.0 J) at three different guide vane openings (21°, 15°, and 12°, respectively) were simulated and compared. The results suggest that, at smaller guide vane openings (15° and 12°), water hammer owing to the increase in rotational speed is the primary unstable issue compared to the pulsation of radial hydraulic exciting forces on the runner. However, at a larger guide vane opening (21°), the latter owing to the back-flow near the runner inlet is the primary unstable issue. Moreover, it is found that a sufficiently large inertia improves the hydraulic fluctuations of the pump-storage power station, particularly in reducing the pulsation of radial hydraulic exciting loads on the runner. The findings of this study provide a valuable reference for determining suitable rotor inertia.

Energy Analysis in a Pump-Turbine During the Load Rejection Process

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Zhenggui Li ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Energy Conversion ◽  
Rotational Speed ◽  
Draft Tube ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Hydraulic Loss ◽  
Pump Turbine ◽  
Hydraulic Losses ◽  
Load Rejection Process

Complex energy conversion and energy dissipation occur in pump-turbines during the load rejection process. However, the underlying fluid mechanism is not clear. In order to solve these problems, in this study, a three-dimensional (3D) transient turbulent flow in a pump-turbine, with clearance during the load rejection process, was simulated using the method of coupling of the rigid rotor motion with flow and dynamic mesh technology. The simulated rotational speed shows good agreement with the experimental data. Most of the differences of rotational speed between simulations and experiments are very small and lower than 5%. Based on the numerical simulation, the energy conversion process, loss distribution, and flow mechanism in a pump-turbine were analyzed using the method of coupling of the entropy production analysis with the flow analysis. The results indicate that the load rejection process of a pump-turbine is an energy-dissipation process where the energy is converted among various energy forms. After load rejection, the hydraulic loss in the reverse pump process distributes primarily in the stay/guide vanes (GV), the vaneless space, and near draft tube inlet. While the hydraulic losses in the runaway process and the braking process are distributed mainly in the elbow section of the draft tube, the clearance of runner (RN), and the vaneless space, the hydraulic losses are mainly caused by viscous dissipation effects of the vortex flows, including the flow separation vortices, the shedding vortices of flow wake, the secondary flow, and the backflow.

Numerical Simulation and Experiment Research on Aerodynamic Characteristics of a Multi-Blade Centrifugal Fan

2011 ◽  
Vol 317-319 ◽  
pp. 2157-2161
Author(s):  
Yong Chao Zhang ◽  
Qing Guang Chen ◽  
Yong Jian Zhang ◽  
Xiang Xing Jia
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Cfd Method

The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

Study of flow characteristics in the S-shaped region of a pump-turbine at Baoquan pumped storage power station

2015 ◽  
Vol 10 (2) ◽  
pp. 242-249
Author(s):  
Jun Li ◽  
Yongmei Cao ◽  
Lei Wang ◽  
Xiaochong Chen
Keyword(s):  
Cfd Simulation ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Modern Society ◽  
Stable Operation ◽  
Power Station ◽  
Pump Turbine ◽  
Research Findings ◽  
Computational Fluid Dynamics Cfd ◽  
Pumped Storage

Pumped storage power plays increasingly important roles in modern society but requires some complex equipment. The characteristics of the S-shaped region of a reversible pump-turbine caused significant difficulties in the stable operation of the unit. In this paper, the 1# pump-turbine at Baoquan storage power station is studied. The basic variations of the internal flow were understood using Computational Fluid Dynamics (CFD) simulation, and the relationship between head variation and the ‘S’ characteristic was analyzed. It was found that the basis of the ‘S’ characteristics was channel congestion caused by vortices. Methods that might be used to eliminate the effects of the ‘S’ characteristic are also given. The authors believe that the research findings in this paper could provide the technical support needed for stable operation of such units, as well as further studies of the ‘S’ characteristic.

scholarly journals Rotational Speed Fluctuation and Internal Flow in a Variable-filling Fluid Coupling

1981 ◽  
Vol 24 (187) ◽  
pp. 109-116
Author(s):  
Kyohichi UCHIYAMA ◽  
Takeo TAKAGI ◽  
Tsutomu OKAZAKI
Keyword(s):  
Rotational Speed ◽  
Internal Flow ◽  
Speed Fluctuation ◽  
Fluid Coupling
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