Performance Of Pump Turbine Research Articles

Research on Automatic Testing of Pump Turbine Model Test Based on Intelligent Technology

Abstract In order to test the performance of pump turbine, it is necessary to collect and analyze the performance indexes such as energy characteristics, stability performance, cavitation performance and force characteristics of the unit through the pump turbine model test test system. however, the current test systems all use manual operation based on the standard specification requirements to handle the data collection and analysis of the test, and the accuracy of the data relies on human experience and the efficiency is not high. The method described in this paper uses emerging computer test technology means such as big data technology, noise and image recognition technology to automatically and efficiently complete the test data test, and quickly complete the test test, while the test results are more accurate.

Effects of guide vane shape on the performances of pump-turbine: A comparative study in energy storage and power generation

Pumped storage unit is a typical energy storage system in electric power grid system. Flow energy dissipation (FED) is a key factor affecting energy utilization efficiency. Guide vane has an important influence on the hydraulic performance and system stability. This study compares the FED difference of two typical guide vanes in turbine mode and pump mode based on Computational Fluid Dynamics (CFD) and entropy production method. The results show that at the same head, the flow rates in energy storage and power generation are different. In pump mode, FED concentrates in runner, guide vane, stay vane and volute. FED concentrates in runner and draft tube in turbine mode. The sources of FED in pump mode and turbine mode are different, including flow separation, jet wake, wall loss, vortex rope and back-flow. Guide vane with oval leading edge can better enhance the flow rate compared with that with sharp leading edge in turbine mode, which decreases FED at small flow rate condition by improving the matching of blade profiles and flow direction. This paper provides a reference for improving the performance of pump turbine through design.

Numerical study on the energy evaluation characteristics in a pump turbine based on the thermodynamic entropy theory

Pumped storage power stations have attracted more and more attention in recent years. As the core component, the performance of pump-turbine has a strong connection with the station's economic effectiveness. The energy evaluation characteristics in a pump turbine are deeply investigated based on the entropy generation theory which has a great advantage to the traditional pressure drop method. The multiphase flow in the pump-turbine under several classical operating conditions are simulated using a modified turbulence model. Cavitation's contribution in energy loss is also considered in the entropy generation theory. Compared with the traditional differential pressure method, the accuracy of entropy generation method is verified. Then, the internal energy loss distribution along the pump-turbine passage at different flow rates are obtained. According to the result, the hydraulic loss mainly occurs in the runner, followed by guide vanes and stay vanes. In the runner, most of the energy loss is distributed in the channel near the lower ring, and the pressure surface is lower than that of the suction surface. The results also show that the stable attached cavity can wrap the blade and reduce friction resistance, and then reduce the wall entropy production value.

Influence of runner leading edge radius on the pump-turbine performance

Abstract In pump-turbines, serious fluid oscillations were reported. It is known that the performance curves of the pump-turbines have an S-shape. In order to reduce the flow oscillation, we investigated the relation between the leading edge radius and the S-shaped characteristics. The effects of the radius on the pump-turbine performance is investigated by the experiments, the numerical calculations and theoretical analyses. The numerical and experimental results agree well. The theoretical loss coefficients were calculated based on the numerical results. The leading edge vorticity causes the inner blade loss. Vortices expand with an increase of the radius.

Investigation of the Flow Instabilities of a Low Specific Speed Pump Turbine Part 1: Experimental and Numerical Analysis

Abstract This is the first part of a two-part paper focusing on the flow instabilities of pump turbines. In this first part, results of the experiments and computational fluid dynamics (CFD) simulations of the research carried out on a low specific speed model pump turbine at HSLU (Lucerne University of Applied Sciences) Switzerland are presented. The requirements of a stable and reliable pump turbine operation, under continuously expanding operating ranges, challenge the hydraulic design and demand new developments. This paper presents the results of experimental (model pump turbine at the test rig) and numerical (CFD) investigations of the pump turbine instabilities of a low specific speed (nq = 25) pump turbine in the turbine operating mode. Four-quadrant characteristics of a low specific speed pump turbine with two similar runners differentiating in the size (diameter) are measured. Testing of both runners with the same guide vane system provided information about the effects of the increased vaneless space on the pump turbine performance and stability. A CFD methodology is developed by applying several turbulence models to accurately predict the characteristics of the reversible pump turbines in the S-shaped region (speed no load conditions) as well as to analyze the flow features especially at off-design conditions. This CFD model is validated against the experimental data at 6 deg and 18 deg guide vane openings in turbine operating mode. Using the data of the unsteady pressure measurements and detailed investigation of unstable ranges on the pump turbine characteristics, flow instabilities in the low-specific speed model pump turbine are analyzed. Relevant frequencies such as rotating stall, steady and unsteady vortex formations are determined.

Numerical Simulation and Computational Flow Characterization Analyses of Centrifugal Pump Operating as Turbine

Using a pump in reverse mode as a hydraulic turbine remains an alternative for hydropower generation in meeting energy needs, especially for the provision of electricity to remote and rural settlements. The primary challenge with small hydroelectric systems is attributed to the high price of smaller size hydraulic turbines. A specific commercial pump model, with a flow rate of 12.5 m3/h, head 32 m, pressure side diameter of 50 mm, impeller out, and inlet diameters of 160 mm and 6 mm, respectively, was chosen for this research. This research aimed to investigate a pump’s flow characteristics as a turbine to help select a suitable pump to be used as a turbine for micro- or small hydropower construction. Numerical methodologies have been adopted to contribute to the thoughtful knowledge of pressure and velocity distribution in the pump turbine performance. In this study, the unsteady flow relations amongst the rotating impeller and stationary volute of the centrifugal pump made up four blades and four splitters. Intermittent simulation results of pressure and velocity flow characteristics were studied considering diverse impeller suction angles. The study was conducted by considering a wide range of rotational speeds starting from 750 rpm to 3250 rpm. From the results, it was found that PAT operation was improved when operated at low speeds compared to high-speed operation. Thus, speeds between 1500 rpm and 2000 rpm were suitable for PAT performance. This research helps to realize the unsteady flow physiognomies, which provide information for future research on PAT. This study makes useful facts available which could be helpful for the pump turbine development. Future studies should focus on cost analysis and emission generation in energy generation.

Hydraulic Optimization of Two-Way Counter-rotating Axial Flow Pump Turbine

The two-way counter-rotation technology is mainly applied to the tidal power station. In this paper, the hydrodynamic optimization of the two-way counter-rotating axial-flow pump turbine is carried out. Under the premise of realizing the forward and reverse power generation and the forward and negative pumping basic function, it has important engineering significance and academic value for improving the pump turbine performance of various working conditions. The main contents are as follows: hydraulic design of “S”-shaped blade for the two-way counter-rotating axial-flow pump turbine is conducted, and the influence of the gap between different impeller stages on the performance is calculated and analyzed, and the variation law of head and efficiency of the pump turbine under different inter-stage clearances is obtained. And the influence of the inter-stage gap on the unit is summarized from the vorticity distribution and the axial section pressure cloud diagram analysis, and the range of the best inter-stage gap of the unit performance is determined.

J-Groove를 이용한 펌프터빈 흡출관 유동 불안정성 억제

In the present study, J-Groove has applied in the diffuser for swirl intensity suppression. The swirl flow mostly occurred at the draft tube of the hydro turbine. The swirl flow is an undesirable flow phenomenon, which is a cause of pressure fluctuation, mechanical vibration, and noise. The performance analysis of the pump turbine was conducted by experiment and CFD analysis. In the pump turbine, the swirl flow is significant in the turbine mode rather than pump mode. The swirl intensity is high at partial load conditions. Pump-turbine performance has deteriorated in off-design conditions due to the high swirl intensity. The J-Groove installation helps to decrease the swirl intensity at the partial load condition without affecting the performance of the pump turbine.

Influences of wear-ring clearance leakage on performance of a small-scale pump-turbine

Wear-ring clearance leakage would affect performance of pump-turbine significantly. In this paper, the variation of the leakage and efficiency of flat ring seal and labyrinth seal are numerically studied on one pump-turbine when the width of clearance is 0.2 mm and 0.5 mm. The result shows that the effect of leakage flow cannot be neglected. The pump-turbine performance affected by leakage in turbine mode is more than that in pump mode at the same sealing structure and width of clearance. Each component’s proportion of total pressure loss hardly varies with flow rate at pump mode, which is opposite to that at turbine mode. Leakage does not change proportionally with system flow rate. When the width of clearance decreases to 0.2 mm, the leakage is reduced obviously because the maximum entropy occurs in the front pump chamber. The mixing of leakage flow and mainstream at impeller inlet at pump mode will increase the total pressure and decrease the flow angle and relative flow angle. Finally, it reduces the impeller’s work capacity.

Effect of lean mode of blade trailing edge on hydraulic performance for double-suction centrifugal pump

For three-dimensional inverse design of water pump, both blade-loading distribution and stacking condition of high-pressure side are important factors affecting the quality of design. For example, inclined trailing edge of blade can suppress the pressure fluctuation and reduce the sound pressure level and sound power of noise for single-suction centrifugal pump. And the lean mode of blade trailing edge can influence hydraulic performance of pump-turbine in pump mode. However, there is no clear view on the effect of lean mode of blade trailing edge on hydraulic performance for double-suction centrifugal pump. Therefore, three different linear lean modes, namely positive lean(+20°), zero lean(0°) and negative lean(-20°), are adopted to simulate the transient flow field respectively for a middle specific speed double-suction centrifugal pump. Concretely, results show that different lean modes of blade trailing edge have little effect on the external characteristics of the pump, and all three schemes can meet the requirements of basic performance. And in operating range of 0.6Q0∼1.2Q0, positive blade lean can suppress the jet-wake structure better. In the vicinity of rated condition, both positive blade lean and negative blade lean can suppress the pressure fluctuation to a certain degree. But with the changes of flow rate, the effect of positive blade lean on pressure fluctuation is unstable. In addition, when pumping sediment-laden water, both positive blade lean and zero blade lean are not conducive to improving the anti-erosion performance of the blade, and especially for the positive blade lean. In summary, in order to improve the integrated performance of low and middle specific speed double-suction centrifugal pump, under the condition of guaranteeing good blade-loading distributions firstly, negative lean mode of blade trailing edge is suggested.

Oxygen dissolution via pump-turbine – Application to wastewater treatment

Large eddy simulations of a ventilated pump-turbine were conducted using LES-mixture model. Peripheral and central aeration were applied to study the effectiveness of oxygen dissolution and the pump-turbine performance. The peripheral draft tube aeration was performed by air injection through (1) a continuous orifice and (2) a series of discrete orifices along the surface of the draft tube. The simulations were performed when the system is operating in the turbine mode. Peripheral aeration was more effective for the achieved dissolved oxygen level and the oxygen dissolution efficiency. The mean dissolved oxygen concentration and the dissolution efficiency inside the draft tube were predicted to be 1.8 mg/l and 80% using the continuous or discrete peripheral aeration and 1.4 mg/l and 25% using the central aeration. A mean value ranging from 1.0 mg/l to 2.0 mg/l was considered to be sufficient for aerobic bacteria to treat the wastewater. Aeration resulted in a minor penalty on the power generation, while it provided a significant reduction in the flow-induced vibration. The central aeration was more effective in reducing the amplitude of pressure fluctuations and yielded more stable turbine operating conditions.

Unsteady numerical analysis of the rotating stall in pump- turbine geometry

Main challenges in energy sector nowadays are storing and recovering of a large amount of energy in a short time. Pumped Storage Power Plants (PSP), using reversible pump- turbines are among the most cost-efficient solution to answer these needs. To provide a rapid adjustment to the electrical grid, pump-turbines are subjects of quick switching between pumping and generating modes and to extended operation under off-design conditions. To maintain the stability of the grid, the continuous operating area of reversible pump-turbines must be free of hydraulic instabilities. One of the main sources of pumping mode instabilities is the presence of the rotating stall that occurs at the part load. It can be observed as periodic occurrence and decay of recirculation zones in the distributor regions. Consequently, the machine can be exposed to uncontrollable shift between the operating points with the significant discharge modification and the drop of the efficiency. The phenomenon is very complex, three-dimensional and demanding for the investigation. The paper presents cost- efficient numerical methodology that enables the accurate prediction and analysis of the rotating stall. The investigations were made on a reduced-scaled high head pump-turbine design. Unsteady numerical calculations were performed using code FINE/TurboTM and URANS equations. Local flow study was done to describe in details the governing mechanisms of the rotating stall. The analyses enable the investigations of the rotating stall frequencies, the number of stalled cells and the intensity of the rotating stall. Moreover, the unsteady calculations give very good prediction of the pump-turbine performance for both, stable and unstable operating regions. Numerical results show very good qualitative and quantitative agreement with the available experimental data.

Analysis of the Unstable Behavior of a Pump-Turbine in Turbine Mode: Fluid-Dynamical and Spectral Characterization of the S-shape Characteristic

The most common mechanical equipment adopted in the new generation of pumped-hydro power plants is represented by reversible pump-turbines (RPT), required to rapidly switch between pumping and generating modes in order to balance the frequent changes in electricity production and consumption caused by unpredictable renewable energy sources. As a consequence, pump-turbines are required to extend their operation under off-design conditions in unstable operating areas. The paper presents a numerical analysis of the unstable behavior of a pump-turbine operating in turbine mode near the no-load condition. To study in depth the unsteady phenomena which lead to the S-shape of the turbine characteristic, a load rejection scenario at constant and large guide vane opening (GVO) was numerically analyzed by running through the flow-speed characteristic up to the turbine brake region. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating stall (RS) (65.1% of the runner rotation frequency) during the turbine brake operation. These phenomena were characterized by frequency and time–frequency analyses of several numerical signals (static pressure, blade torque, mass flow rate in blade passages). The influence of the development of these unsteady phenomena on the pump-turbine performance in a turbine operation was also analyzed, and the potential causes that generated the S-shaped characteristic curve were also investigated.

Optimization for Cavitation Inception Performance of Pump-Turbine in Pump Mode Based on Genetic Algorithm

Cavitation is a negative factor of hydraulic machinery because of its undesirable effects on the operation stability and safety. For reversible pump-turbines, the improvement of cavitation inception performance in pump mode is very important due to the strict requirements. The geometry of blade leading edge is crucial for the local flow separation which affects the scale and position of pressure drop. Hence, the optimization of leading edge shape is helpful for the improvement of cavitation inception performance. Based on the genetic algorithm, optimization under multiple flow rate conditions was conducted by modifying the leading edge ellipse ratio and blade thickness on the front 20% meanline. By using CFD simulation, optimization was completed with obvious improvements on the cavitation inception performance. CFD results show that the pressure drop location had moved downstream with the increasement of the minimum pressure coefficient. Experimental verifications also got an obvious enhancement of cavitation inception performance. The stability and safety was improved by moving the cavitation inception curve out of the operating range. This optimization is proved applicable and effective for the engineering applications of reversible pump-turbines.

The hydraulic design of pump turbine for Xianyou pumped storage power station

This paper presents the hydraulic design of pump turbines for Xianyou pumped storage power station. The method of improving the hydraulic performance of pump turbine with CFD analysis is given. The results of model test indicate that the final hydraulic design of pump turbine for Xianyou pumped storage power station is of high efficiencies, good