Pump Turbine Research Articles

Digital twin modeling and operation optimization of the steam turbine system of thermal power plants

The increasing deployment of renewable energy sources necessitates peak regulation services from thermal power plants, impacting their energy efficiency. Central to these plants, the steam turbine system significantly influences their operational efficiency. A digital twin model of this system was developed, integrating mechanism-driven and data-driven modeling methods. The neural network data-driven approach was specifically utilized for parameters such as feedwater pump speed and steam flow rate to the pump turbine. Other parameters were modeled with mechanism data hybrid driven modeling method. This model computes vital metrics such as low-pressure turbine exhaust steam enthalpy, work done and heat absorption per unit mass of steam, system efficiency, feedwater mass flow rate, and water-coal ratio—key for evaluating and enhancing the system's energy efficiency. An investigation into a reference case showed a decline in efficiency below design levels due to aging. By optimizing the live steam pressure and the cold-end system, relative improvements in energy efficiency of 0.35 % and 0.14 %, respectively, were achievable.

Force Characteristics Analysis of Yixing Pump-Turbine Head Cover Bolts

This article conducts numerical calculations on the head cover bolts of the pump turbine in Yixing Pumped Storage Power Station under typical steady-state and transient conditions and analyses the force characteristics of the coupling bolts under turbine, pump, pump zero flow and load rejection conditions. On this basis, further evaluation of head cover bolts safety and reasonable suggestions for subsequent operation are provided.

Beyond fixed-speed pumped storage: A comprehensive evaluation of different flexible pumped storage technologies in energy systems

Traditional fixed-speed pumped storage (PS) has been a reliable measure to provide power system flexibility. However, the increasing need for flexibility of power systems due to adverse environmental events and amplified utilization of renewable sources necessitates the need for modernization of PS units. This paper studies the effect of five PS technologies with different operational flexibility in Qinghai Province's energy system. Firstly, PS models considering the difference in minimum stable generation & pumping, unit efficiency, configurations of turbine & pump are established. Then, the energy mixes, planning capacity, inflow, reservoir operation curve and other data are input into the energy system model. Finally, we quantify the effects of different PS forms on the energy system based on technical, economic, and emission indicators, also identify the optimal PS considering cost preference and emission preference. Results show that the investment costs for various pumped storage technologies depend on the motor type and pump capacity. Fixed-speed pump turbine technologies have a lower cumulative power variation of up to 11,225 GWh and the largest number of start-ups in pumping conditions, at 10,857 times. Increasing operational flexibility stabilizes the reservoir water level, and enhancing pump capacity reduces net load fluctuations for ternary PS and variable-speed quaternary PS. Improving wind-solar curtailment is limited by pump capacity, generating flexibility, and reservoir water level. Systems equipped with fixed-speed PS technologies emit more than carbon emissions other PS technologies. Our research outcomes have the potential to provide valuable insights, enabling stakeholders to optimize the deployment of pumped storage flexibility in low-carbon energy systems, taking into account the energy mix and hydrological conditions that are specific to each region.

A new design method for the vortex hydrogen circulating pump system

Against the backdrop of “carbon peak and carbon neutrality,” the hydrogen and fuel cell vehicle industry are rapidly developing. Within the on-board hydrogen supply system, the hydrogen circulation pump serves as an essential component of the hydrogen fuel cell system. The spiral disk, as a core part of the hydrogen fuel cell system’s vortex hydrogen circulation pump (VHCP), plays a crucial role in determining the performance of the hydrogen circulation system in hydrogen fuel cell vehicles. To meet the requirements for high-performance and high-reliability development of the hydrogen circulation pump, the VHCP scheme is adopted as the choice for the hydrogen pump solution. Through the magnetic suspension and no connection shaft structural design, the feasibility of applying the high speed and high flow hydrogen turbine was initially validated. Utilizing Fluent analysis software and high precision performance test bench, a comprehensive three-dimensional numerical simulation of the turbine design under various operating conditions was conducted and performance test verification, demonstrating that the performance meets the required specifications. By conducting research in both strength optimization design and performance requirement, two major technical challenges in turbine pump application were overcome. Combined with the experimental results of the turbine medium, it is concluded that the vortex pump can meet the flow and pressure rise under the premise of low power consumption in the hydrogen circulation system so as to perfectly increase the hydrogen return amount. Based on these findings, recommendations are proposed for the future development direction of hydrogen supply systems in hydrogen fuel cell vehicles.

FED evaluation in a small double-suction reversible pump turbine considering sediment erosion

Double-suction pump-turbines are a special type of reversible pump-turbine which serves the pumped storage hydro power plant. Enhancing the energy conversion efficiency of the power station can be effectively achieved by reducing the internal Flow Energy Dissipation (FED) within the pump-turbine. The key to addressing this challenge lies in the identification of high FED regions and conducting visualized analyses. In this study, computational fluid dynamics (CFD), thermodynamic calculation methods and the Finnie erosion model are combined to perform two-phase flow numerical simulations of a specific double-suction pump-turbine model under both pump and turbine operating modes. We analyzed the FED in different regions off wall. The energy loss distribution is provided within these five regions for the volute casing, suction chamber, and impeller separately, and conducted an analysis of component wear. The research findings revealed that, in the pump mode, FED primarily concentrates within the volute casing, while in the turbine mode, it is concentrated within the suction chamber, with both regions accounting for over 70 % of the total energy dissipation. The proportion of internal FED in five regions at varying distances from the wall for each component showed significant disparities under different operating conditions, closely related to the internal flow characteristics of the components. In pump mode, wear primarily occurs in the volute casing, while the wear in the suction chamber and impeller can be considered negligible. In turbine mode, each component experiences some level of wear. This provides a foundation for reducing flow energy losses and preventing sediment erosion.

An Ejector and Flashbox-Integrated Approach to Flue Gas Waste Heat Recovery: A Novel Systematic Study

In this study, a comprehensive examination was conducted to explore the technology involved in the recovery of waste heat from flue gas emitted by a 1000 MW unit. Traditional methods are constrained in their ability to harness waste heat from flue gas solely for the purpose of generating medium-temperature water. The system being examined not only recovers waste heat but also utilizes it to generate steam, thereby greatly improving resource efficiency. The process entails utilizing the flue gas to heat water to a certain temperature, followed by subjecting it to flash evaporation. This process leads to the generation of low-pressure waste heat steam. Within the steam ejector, the waste heat steam combines with high-pressure motive steam extracted from the source, resulting in the formation of medium-pressure steam. Within the steam ejector, the waste heat steam blends with high-pressure motive steam drawn from the source, forming medium-pressure steam that eventually feeds into the A8 steam extraction pipe (low-pressure turbine pumping pipe). The present study examines the fluctuation patterns in motive steam flow, suction coefficient, waste heat steam volume, and outlet temperature of the flue water heat exchanger when different motive steam sources are used. Additionally, the research calculates the reduction in CO2 emissions, the coal consumption for power supply, and the cost savings in fuel for the retrofitted system. The findings indicate that maximizing energy utilization can be achieved by operating the retrofitted unit at the lowest feasible waste heat steam pressure. The implementation of the new system has resulted in a substantial decrease in coal consumption for power supply. When employing main steam as the extraction steam source, the consumption of coal for power generation decreases in proportion to the decrease in waste heat steam pressure while maintaining a constant unit load. When the waste heat steam pressure reaches 0.0312 MPa, the recorded coal consumption for power generation varies between 289.43 g/kWh at 100% turbine heat acceptance (THA) and 326.94 g/kWh at 30%THA. When comparing this performance with the initial thermal power plant (TPP) unit, it demonstrates reductions of 2.26 g/kWh and 1.52 g/kWh, respectively. After implementing modifications to this 1000 MW unit, it is projected that the annual CO2 emissions can be effectively reduced by 6333.97 tons, resulting in significant cost savings of approximately USD 0.23 million in fuel expenses. This system exhibits considerable potential in terms of emission reduction and provides valuable insights for thermal power plants aiming to decrease unit energy consumption.

Towards the integration of distributed renewables: Operation analysis of pumped storage system under off-design condition based on CFD

Pumped storage plants are increasingly developing to cope with the rapid growth of renewable energy production. Micro-pumped storage (MPS) system is a new storage strategy for distributed energy integration. Centrifugal pump or axial pump replaces conventional pump turbines in this pumped storage system to ensure economic convenience and system flexibility. However, when MPS works in the generating operation mode, the limited high-efficiency range will result in complex hydrodynamic behavior and stability issues under off-design conditions due to renewable integration. At present, the instability mechanism of MPS under off-design conditions is not clear enough, and there is a lack of excellent research methods to analyze this problem. Therefore, this paper firstly introduces the entropy production theory considering the wall effect for visualizing the energy loss. Then the relationship between hydraulic performance and unsteady flow characteristics is established based on the loss characteristics. The results show that the entropy production theory with customized wall functions has higher accuracy and advantages in energy loss analysis compared to the default wall functions. Under partial loading conditions, the spatial-temporal instability of the flow separation point causes a rotating stall within the impeller, which in turn leads to destabilization and a significant reduction in hydraulic performance. Under overload conditions, despite slight changes in hydraulic performance, the most significant pressure fluctuation is six times stronger than the best efficiency point.

Design of Fire Risk Estimation Method Based on Facility Data for Thermal Power Plants.

In this paper, we propose a data classification and analysis method to estimate fire risk using facility data of thermal power plants. To estimate fire risk based on facility data, we divided facilities into three states-Steady, Transient, and Anomaly-categorized by their purposes and operational conditions. This method is designed to satisfy three requirements of fire protection systems for thermal power plants. For example, areas with fire risk must be identified, and fire risks should be classified and integrated into existing systems. We classified thermal power plants into turbine, boiler, and indoor coal shed zones. Each zone was subdivided into small pieces of equipment. The turbine, generator, oil-related equipment, hydrogen (H2), and boiler feed pump (BFP) were selected for the turbine zone, while the pulverizer and ignition oil were chosen for the boiler zone. We selected fire-related tags from Supervisory Control and Data Acquisition (SCADA) data and acquired sample data during a specific period for two thermal power plants based on inspection of fire and explosion scenarios in thermal power plants over many years. We focused on crucial fire cases such as pool fires, 3D fires, and jet fires and organized three fire hazard levels for each zone. Experimental analysis was conducted with these data set by the proposed method for 500 MW and 100 MW thermal power plants. The data classification and analysis methods presented in this paper can provide indirect experience for data analysts who do not have domain knowledge about power plant fires and can also offer good inspiration for data analysts who need to understand power plant facilities.

Design and numerical study of a pump-turbine for retrofitting of an existing francis turbine

Energy is the vital requirements of daily life. It is mainly concerned with production, storage, balance and distribution. Hydropower is a key sources of renewable energy. Regarding the storage of hydropower energy, pumped storage comes in the foremost choice. The runner is the main component of pump storage hydropower project. As the energy storage trend is shifting for pump storage hydropower project, the design methodology and operating range of reversible pump turbine play major role. The pump turbine has always compromise in efficiency due to the same machine operating in both turbine and pump mode. Similarly flow instability in the major hurdles in pump turbine. The initial cost for the pumped storage hydropower will certainly be high. Due to this, research trend has been now shifted in possibility of retrofitting of existing hydropower with pumped storage. This is also the true for the study presented here, where the retrofitting of reversible pump turbine in existing hydropower project. The basic dimension for the reversible pump turbine is taken from the existing model Francis Turbine. The blade profile has been changed by increasing blade passage area. Numerical analysis has been performed in both pump mode and turbine mode by at different guide vane angles. Finally the results are discussed with future recommendations.

Dynamic response of a pump-turbine runner during turbine's mode starting up

With an increase in head and rotational speed, pumped storage units, particularly the runner, experience higher pressure and centrifugal force. In this study, a combination of the 1D method of characteristics (MOC), 3D computational fluid dynamics (CFD) as well as computational structure dynamics (CSD) was employed to examine the dynamic response of a pump turbine runner during turbine's mode starting up. A detailed analysis of the transient characteristics during this process was conducted. Initially, the high-pressure zone concentrated on the pressure surface of the runner's inlet side. However, this zone gradually expanded over time and shifted to the suction surface. The time-frequency of pressure pulsation showed significant low-frequency and second harmonic frequency components. Different monitoring points exhibited different sensitivities to rotational speed and torque. It can be assumed that runner's blade stress is proportional to the square of the rotational speed. The sensitivity of blade stress related to runner speed and torque provides important results and analysis. P2 is the most sensitive to changes in rotational speed, while P1 is the most sensitive to changes in torque. These findings enhance our understanding of the dynamic behavior of the RPT runner and contribute to potential improvements in design and operation.

Design and Construction of a Turbine Pump as Laboratory Scale Micro Hydro Electricity Learning Media

Lack of understanding of students about renewable energy can be produced from pumps, namely electrical energy. The energy produced by this pump is beneficial for rural areas that do not have electricity. The purpose of this research is to modify the pump as a turbine for a micro-hydro power plant which can be used by students of the Mechanical Engineering Department, the University of Muhammadiyah Pontianak as learning media in the field of fluid machines and laboratory-scale energy conversion machines. The research subjects were 15 students of mechanical engineering and pumps that were converted into turbines to generate electricity. The data collected first comes from the performance test of a pump that has been converted into a pump as a turbine. Further data was obtained from students through a pretest with a conceptual type of pump used as a power plant. Then after the pretest, students were treated by using and operating a pump as a turbine as a learning media. From this media, students must also explain the concept and how the pump as a turbine can produce electrical energy in writing. The student's written results obtained were analyzed to determine the effect of the pump as turbine model on students' understanding of conceptual analysis. The result of this research is a pump that has been converted into a pump as the turbine. In addition, as a simple practical tool to test the performance of the pump as a turbine. There was an increase in students' understanding in terms of the ability to describe the concept of power generation sources from pumps and analyze the process and workings of the pump as a turbine to produce electrical energy.

Evolution mechanism of unsteady internal flow of an ultra-high head pump-turbine in pump mode

In this study, the unsteady flow of an ultra-high-head model pump turbine in pump mode is numerically investigated, revealing the evolution mechanism of unsteady flow diffusion and propagation. Under high-flow-rate and high-efficiency conditions, stable flow separation occurs in the channel of the stay vanes. As the flow rate decreases, the flow separation gradually spreads in the radial direction and expands from the stay vanes to the guide vanes. This causes a partial blockage in the channel of the guide vanes. Meanwhile, the flow separation gradually switches from stable to unstable with a low-frequency rotation (about 4.8 % of the impeller rotational frequency) in the circumferential direction. In addition, the correlation between the hump characteristics and unsteady flow is discussed. For an ultra-high-head pump turbine, the unstable flow initiates at static operating conditions from the pump performance curve with negative slope, which is significantly different from medium and low-head pump turbines.

Construction of the Dynamic Model and Control System for the Canadian Supercritical Water–Cooled Reactor Power Plant

Canada has proposed the supercritical water–cooled reactor (SCWR) concept as one of the Generation IV nuclear reactors. In the SCWR power plant, the supercritical water is heated in the reactor and then flows to the turbine directly. Therefore, knowledge of the dynamic behaviors of the system is necessary for the stable operation of the power plant. There is still a lack of study on the control system for the proposed SCWR power plant. In this study, a dynamic model for the entire SCWR power plant is constructed that includes the reactor, turbine, condenser, and feedwater pump. Based on the model, the open-loop characteristics of the system when subjected to perturbations in the inputs are analyzed. Subsequently, a feedback control strategy is adopted to regulate the outputs of the system when there are disturbances. The evaluation of the performance of the control system shows that the proposed control system can return the plant back to the operating conditions effectively.

Hydraulic Characterization of Variable-Speed Pump Turbine under Typical Pumping Modes

The pump turbine is a crucial component of pumped storage hydropower plants. When operated at a constant speed, it does not respond well to variations in the grid frequency. To improve the hydraulic efficiency of pumped storage units, variable-speed units have been introduced. However, the mechanism of variable-speed pump turbines has not been extensively studied numerically. In this study, the flow characteristics of a variable-speed pump turbine were computed under two typical pumping modes, the maximum head and minimum flow rate condition, as well as the minimum head and maximum flow rate condition. The computed results aligned with experimental results, and the changing trends of hydraulic thrust under these two pumping modes were discussed. The error for the Hmax, Qmin condition was 1.3%, and the error for the Hmin, Qmax condition was −1.9%. These error values fell within a reasonable range. The research findings indicate that in the Hmax, Qmin condition, the flow within the flow passage exhibited higher velocity, which was 84.87 m/s, increased flow turbulence, larger pressure fluctuations, and poorer unit stability. On the other hand, in the Hmin, Qmax condition, both the axial hydraulic thrust and radial forces were greater, and there were sudden changes in the extreme values of pressure fluctuations over a certain period of time. It is recommended to avoid operating the variable-speed pump turbine under these two conditions during pumping operations.

Energy loss analysis of transition simulation for a prototype reversible pump turbine during load rejection process

The dynamic behavior of a reversible pump turbine (RPT) during the load rejection process was investigated through numerical simulation and experimental testing. The study focused on various parameters, such as the operation of guide vanes, torque, flow, head, and runner forces. The pressure fluctuations at different monitoring points were analyzed using the time-frequency method, specifically the continuous wavelet transforms (CWT). The results revealed significant pressure pulsation amplitudes in the vaneless region. Additionally, the entropy production rate was employed to quantify energy loss in different domains, including direct dissipation, turbulent dissipation, and wall shear stress. Moreover, the study utilized the vorticity transport equation to examine vortex characteristics and transport in the stay vanes, guide vanes, and runner flow channels. The vortex characteristics were classified into relative vortex stretching (RVS), Coriolis force (CORF), and viscous diffusion (VISD). The findings highlight significant energy loss in flow patterns associated with high RVS and CORF regions. This study provides valuable insights into the transition process and energy loss of RPTs during load rejection, serving as a basis for future research aiming to enhance the safety and reliability of RPTs under load rejection conditions.

A Field Investigation of Stability Characteristics of Pressure Fluctuation and Vibration in Prototype Pump Turbine at Multiple Working Points

In practical operation, pump turbines typically operate far from their designed working points, which has a significant impact on the stability of the unit’s operation. In this paper, we conducted a field test to investigate the stability characteristics of prototype pump turbines at different working points. By adjusting the given power of the generator in a stepwise manner to control its working point, we obtained the statistical and spectral characteristics of pressure signals and acceleration signals. In turbine mode, the result shows that, at low, medium, and high power, the variation in pressure fluctuation characteristics is influenced by three different factors, while vibration generally reaches its maximum value at approximately 50 MW. In pump mode, variations in pressure were observed among different measurement points in the low-frequency range, and the characteristics of vibration acceleration were influenced by both the rotor–stator interaction (RSI) and the structural modal frequencies. We emphasized that the high-frequency bands have influences on the unit comparable in magnitude to those of the rotor–stator interaction, which has rarely been mentioned in previous studies. Through detailed testing and analysis of the unit’s actual operation, we can gain a better understanding of its behavior and performance in the turbine and pump modes, and these results hold significant importance for ensuring the stability and reliability of the unit.

Numerical Study on the Effect of Crown Clearance Thickness on High-Head Pump Turbines

In order to promote the development of new power systems and the consumption of clean energy, pumped storage hydropower stations tend to become increasingly larger in capacity and higher in head height. In this paper, a three-dimensional model of the full channel of a high-head pump turbine is established, and the influence of the gap thickness between the runner crown and the headcover on the internal flow field characteristics, pressure fluctuation characteristics and axial water thrust are studied by means of computational fluid dynamics (CFD). The results indicate that the area where the pressure and velocity vary greatly in the flow field of the crown clearance is at the seal of the labyrinth ring. In addition, the pressure balance pipe has a greater impact on the pressure and flow rate of the water passing through the clearance, and the crown clearance near the pressure balance pipe generates a vortex, resulting in energy loss. Decreasing the thickness of the clearance has no obvious effect on the pressure on the flow-passing components, and increasing the thickness of the clearance has a great change in the pressure values at the upper crown inlet, in front of the labyrinth ring of the crown and in front of the labyrinth ring of the band. The upper part of the vaneless area, the crown inlet and the lower ring inlet are close to the runner; hence, the interference from the rotating parts is the strongest. The effect of increasing the thickness of the crown clearance on the axial water thrust is greater than that of decreasing the thickness of the crown clearance. The pulsation frequency of the axial thrust on the crown, band and blade and the resultant force of the axial thrust increase with the increase in the crown clearance thickness.

Internal Flow Phenomena of Two-Way Contra-Rotating Axial-Flow Pump-Turbine with Various Numbers of Blades in Pump Mode

The focus of this paper is to investigate how various numbers of blades impact the performance of a two-way contra-rotating axial-flow pump-turbine when operating in pump mode. In order to meet the two-way operation of the pump-turbine, the front and rear impellers are mirror-symmetric with the same hydraulic model, which ensures the consistent performance of the forward and reverse working conditions. However, when the two-stage impellers have the same number of blades, the dynamic–dynamic interference can be severe, which can threaten the stability of the unit. The present study explores the use of two-stage impellers with varying numbers of blades as a means of enhancing the performance of tidal energy units. By conducting numerical simulations on the front and rear impellers under different flow rates in pump mode, the impact of increasing the number of blades in each stage on the external characteristics of the pump-turbine is revealed. The internal flow characteristics of different models are analyzed, and the impact of the number of blades on the vortex is studied. Different blade numbers will have a certain impact on the internal flow of the two-way contra-rotating axial-flow pump–turbine. Increasing the number of blades will affect the development of tip-leakage vortices and promote their intersection with the wake. In addition, changes in the number of blades will have an impact on the location of the leading edge (LE) water impact on the rear impeller, which in turn affects the contours of vorticity of the rear impeller near the LE and the location of the suction surface (SS) flow separation. The findings of this study offer valuable insights for future research on the operation of contra-rotating axial-flow pump-turbines.

Research on Gravity Energy Saving Reconstruction Technology of Circulating Cooling Water in Mechanical Ventilation Cooling Tower of a Steel Plant

There is a height drop in the rain area of the circulating cooling water in mechanical ventilation circulating cooling towers, resulting in the ineffective use of gravitational potential energy. High-level water collection is an effective way to reduce the energy consumption of the cooling tower. Based on this, aiming to solve the gravity energy waste problem of circulating water in the cooling tower of a steel plant, this paper innovatively puts forward the high-level water tank to utilize the energy-saving transformation technology of turbine power generation and pump power saving. Additionally, this paper explores the energy-saving effects of the two methods under different height drops. The results show that the maximum utilizable rain area height of the cooling tower is 5 m, while the annual electric energy output of turbine technology can reach 4.704 million kW·h. The high water collection technology can reduce pump power consumption and save up to 7.35 million kW·h per year of electric energy, maintaining a more significant energy-saving ability compared with the turbine power generation technology. In terms of performance, the design of a high-level water tank is to help eliminate rain areas and improve the heat exchange efficiency of water and gas, so that the water temperature of the outgoing tower is 0.13 °C lower than that of the conventional cooling tower. Meanwhile, the ventilation resistance in the rain area is weakened, the resistance coefficient can be reduced by about 40–50%, and the noise can be reduced by about 10 dB (A) under the action of the water collection device. According to the economic evaluation, the total cost of turbine power generation technology is 0.563 million dollars and the total cost of high-level water collection technology is 0.446 million dollars. The cost can be realized within two years, but the high-level water collection technology avoids additional pump maintenance costs and has better economy. This study provides a theoretical basis for the transformation and optimization design of mechanical ventilation cooling towers, and has important reference value.

Investigate the full characteristic of a centrifugal pump-as-turbine (PAT) in turbine and reverse pump modes

Large centrifugal pumps can generate electricity in reverse, reducing the power supply pressure of the power grid. However, S region may occurs during the operation and regulation of the pump as a steam turbine (PAT). The S region can cause unstable unit startup, not only causing hydraulic system oscillation, but also accompanied by strong vibration and noise. Understanding the characteristic curve of the S region is of great significance for improving unit stability and efficiency. Previously, the main research object in S area was small generator units. This article conducted unsteady numerical simulation and experimental research on a large centrifugal pump. Analysed the internal flow rate, blade load, entropy generation, and pressure pulsation under three special operating conditions: the optimal operating condition, runaway operating condition, and braking operating condition in the S region. In addition, a comparative analysis was conducted on three pairs of operating conditions: S region turbine mode and reverse pump mode, with opposite flow direction, similar flow rate, and the same speed. Research has found that in the S region of large centrifugal pumps, the flow chaos in the turbine mode mainly occurs in the impeller section, and the maximum pressure occurs in the stationary blade section. The flow chaos under reverse pump operation mainly occurs in the stationary blade section, and the maximum pressure occurs in the impeller section.