bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of axial hydraulic thrust and radial force characteristics of a variable speed pump-turbine unit
Authors: Wang Lei , Yu Shuang , Shang Linmin , Cao Jingwei , Wang Zhengwei , Liu Xiaobing
Published: June 2024

When the pump turbine does variable speed operation, it can improve the operation efficiency in the turbine mode, and it can improve the automatic frequency adjustment efficiency in the pump mode. However, the hydraulic thrust will also change when the speed changes, and the magnitude of the hydraulic thrust is crucial for the safe and stable operation of the unit. The work of this paper is to analyze the changes of the axial hydraulic force and radial force with the change of the speed by numerical simulation method. It is found that the fluctuation of axial hydraulic thrust can reach about 34 t at 398.57rpm speed, 37 t at 412.16rpm speed and 21 t at 428.6rpm speed. the fluctuation of radial force can reach about 13.78 t, 14.4 t and 12.4 t. The purpose of this paper is to use the simulation results to understand the hydraulic thrust characteristics and ensure the stability of the unit to select the appropriate speed range, provide the basis for stable operation of the unit under design conditions.
Evolution of Runner Forces during Simultaneous Pump-Trip Transient Process of Two Pump-Turbines
Authors: Ke Liu , Yongguang Cheng , Jinghuan Ding , Xi Wang
Published: June 2024

To ensure no cavitation and water column separation in pump-turbines, the suction heights of pump-turbines in high-head pumped-storage hydropower stations have to be decreased to about –100 m, which leads to high pressure in the draft-tube. During the pump-trip transient process of pump-turbines, the positive water hammer wave in draft-tube superposing the initial high pressure may cause an imbalance of rotating parts and even a lifting-up accident. To quantify the runner forces, two typical transient processes, with and without guide-vane closure after the simultaneous power-off of the two pump-turbines in one hydraulic system, were simulated by using the one-dimensional and three-dimensional coupled (1D-3D) computational fluid dynamics (CFD) method. The results show that the maximum upward axial force on the runner during the process without guide-vane closure (runaway) is significantly higher than that during the process with guide-vane closure. Two significant maximum upward axial forces were observed during the runaway process, and they were around the zero and the valley speed moments. The main causes are the pressure decrease in the runner’s high-pressure zone owing to high-speed bypass flows, and the spiral-case negative water-hammer wave and draft-tube positive water-hammer wave caused by discharge rise. However, the draft-tube positive water hammer wave superposing the high pressure did not cause the maximum axial force. The above two moments of highest axial forces during the runaway process and the proper guide-vane closure rule deserve special attention in the design and operation phases.
Numerical study of rotor-stator interaction in variable speed reversible pump-turbine in turbine mode at low head
Authors: Rode B R , Kumar A , Segoufin C , Laurant Y
Published: June 2024

Pumped storage hydropower (PSH) offers the cost-effective storage of large quantities of energy with high efficiency. Reversible pump-turbines (RPT) are used in PSPs having large head variations and where variable speed operation can enhance its efficiency and grid stability. The RPT may experience higher fatigue and vibrations due to hydraulic instabilities caused by pressure fluctuations in the vaneless space between runner blades and guide vane interaction, known as rotor-stator interaction (RSI). Because of this instability, the local components of the powerhouse vibrate severely. Therefore, there is a need to study the pressure fluctuations caused by RSI in the variable speed RPTs. The present numerical study focuses on the pressure fluctuations due to RSI in turbine mode conditions having low available head. The present study used a reduced scale high-head variable speed RPT model, and the SST k-ω turbulence model was used to carry out numerical calculations. The analysis was performed at the best efficiency point and low head operating conditions having optimized rotational speed. The analysis showed that the main source of pressure fluctuations in the RPT at all operating conditions is the RSI, where the dominant frequency is BPF and its harmonics.
Vibration and noise of a high head pump turbine: analysis and improvement
Authors: Guan Z W , Jia W B , Leng Z J , Chen J , Wang Z N , He Q Y , Liang Q W
Published: June 2024

In a high head pumped storage power plant with 9 blades and 20 guide vanes, vibration and noise problems occurred with characteristic frequency of 2 times the blade passing frequency (BPF). It is found that the first main frequency of pressure pulsation in the vaneless zone is also 2BPF with a two-nodal diameter mode by using three dimensional unsteady numerical method, which indicates that the main cause of vibration and noise is rotor stator interaction (RSI). By increasing the radial gap of the vaneless zone, the amplitude of pressure pulsation in the vaneless zone is reduced by 40%-50% according numerical results. One unit in the power station was refurbished. It was shown that the pressure pulsation in the vaneless zone was reduced by 40%, and the head cover vibration was also reduced, and the noise in the turbine pit was reduced by 6 dB according the field test results. So the numerical analysis and prediction here are very accurate, and the vibration and noise problems of this power station are caused by RSI.
Simulation analysis of runaway process of tubular pump and comparison of site test
Authors: Zhongwei He , Linfeng Shu , Chengjun Li
Published: June 2024

To investigate the transient characteristics of tubular pumps during runaway, we developed a three-dimensional model of the pump and its flow channel. Using this model, we conducted a CFD simulation to analyse the three-dimensional transient process of the tubular pump’s runaway, and obtained the internal and external characteristic parameters of the pump. By comparing the results of the site test and the numerical simulation, we verified the correctness of the speed, flow, pressure pulsation, and eccentric zone during the runaway process of the numerical simulation. This verification provides technical support for the subsequent pump station operation.
Numerical investigation on slip velocity characteristics of gas-liquid two-phase flow in a multiphase pump under different blade tip clearance
Authors: Li Chenhao , Wu Xitong , Luo Xingqi , Feng Jianjun , Zhu Guojun , Wang Xiaohang
Published: June 2024

It is significant to explore the slip velocity characteristics of two-phase in blade tip clearance (BTC) of multiphase pump for improving semi-open mixed-flow pump performance. On the ground of the Euler-Euler inhomogeneous model, a gas-liquid mixed-flow pump was taken as the research object. Using CFX software to simulate the flow field in the multiphase pump with conditions of the inlet gas void fraction (IGVF) are 10%, 20% and 30%. The slip velocity characteristics of gas-liquid two-phase in mixed-flow multiphase pump with different blade tip clearance sizes (BTCS) were analyzed. The results show that there is obvious slip velocity on blade leading edge (L.E.), trailing edge (T.E.) and pressure side (PS) of BTC of mixed-flow pump impeller. When BTCS is small, the slip velocity on the tip pressure side has little change along flow direction, but with the increase of BTCS, slip velocity on the tip pressure side will gradually increase. There is a positive correlation between slip velocity and the pressure gradient. The research results can provide significant guidance for optimization design of semi-open mixed-flow multiphase pump.
Coherent structures decomposition of internal flow in the double-suction centrifugal pump impeller
Authors: Zhang Wenlu , Deng Shuwen , Wang Tao , Jiang Bo , Wang Yuchuan
Published: June 2024

In order to understand the unsteady flow phenomenon of the centrifugal pump, the dynamic mode decomposition method (DMD) is introduced to extract the three-dimensional coherent structure of the rotating flow field in the impeller passage under three different working conditions of the double-suction centrifugal pump. The time series collection of flow field is constructed by CFD numerical simulation, and the approximate matrix characteristic parameters and different modal data are solved. The analysis results show that the position, form and spatial-temporal evolution of the coherent structure can be accurately captured by DMD method corresponding to a single frequency in the double suction pump. For the temporal evolution, the coherent structure corresponding to low frequency is the most stable and dominate the unsteady flow. For the spatial evolution, the coherent structure corresponding to even-fold rotational frequency mostly occurs near the pressure side of the blade at the outlet of the impeller, and the coherent structure corresponding to odd-fold rotational frequency is mostly located in the flow field inside the impeller or near the blade surface.
Transient vortical structure evolution under part-load condition in a high-power double-suction centrifugal pump based on Liutex method
Authors: Deng Qifan , Pei Ji , Wang Wenjie
Published: June 2024

In order to investigate the evolution of vortical structures inside a high-power double-suction centrifugal pump, the flow fields were solved numerically by the SST k-ω turbulence mode. After experimental validation, the Liutex/Rortex method was adopted for identifying vortices for each step from the numerical results, and the enstrophy was adopted to present the kinetic energy that vortical structures contained. The vortical structures at different seconds were obtained, and the vortices evolution was figured out. The results indicate that: the wake vortex was the dominant type inside the volute. Vortical structures at the impeller inlet evolve periodically. The interactions between the impeller leading edge with suction ribs and the blade trailing edge and volute tongues were critical factors for vortex evolution. Vortical structures mainly formed at the impeller inlet near the blade suction side. The suction rib would decrease the absolute rotational intensity around it, but the relative local rigid vortex would keep a high intensity. Due to the suction rib and volute tongues, the vortices variated with a period of 1/2T.
Effect of airfoil trailing edge up on the performance of gas-liquid multiphase pumps
Authors: Nan Haozhi , Han Wei , Li Rennian
Published: June 2024

In this study, the impact of blade trailing edge structure on the performance of multiphase pumps was investigated. The modification parameters of the impeller blade airfoil were characterized by defining and adjusting the chord length ratio l/l
0 and deflection k, based on the design methodology employed for wing flap lifting devices. The impeller blade airfoil was modified using the trailing edge up design approach. Comparative analysis was conducted to evaluate the effectiveness of elevating the trailing edge of the airfoil in improving flow channel blockage, reducing turbulent energy at the impeller outlet, minimizing energy dissipation, and ultimately enhancing the efficiency of multiphase pumps. Remarkably, a maximum efficiency improvement of up to 3.04% was observed when the inlet gas content reached 70%.
Numerical study on the flow-induced vibration of a high-pressure-jet pump on a dredger and corresponding impeller optimization
Authors: Hu Jingzhao , Cao Lei , Zhuang Haifei
Published: June 2024

Trailing suction hopper dredgers are usually equipped with high-pressure-jet pumps, which provide high pressure water to improve dredging efficiency. In a newly built trailing suction hopper dredger, the high-pressure-jet pump encountered serious vibration problem. In this study, unsteady Reynolds-averaged Navier-Stokes equations were solved with Shear Stress Transport k-ω turbulence model to carry out pump-pipeline matching analysis, and the causes of flow-induced vibration were discussed. The impeller was correspondingly optimized by increasing the blade number and moderately decreasing the blade inlet setting angle and wrap angle. The optimization results show that the high-pressure-jet pump works in the high-efficiency zone both for the high-speed dredging process and low-speed hopper discharging process, and the time-average value and amplitude of the hydraulic radial force drops by more than 30% under the required working condition, which effectively mitigates the flow-induced vibration.
Numerical Simulation of Unsteady Cavitation at the Tongue of a Centrifugal Pump
Authors: Zhou Wenbo , Zhang Yongxue , Yuan Zhiyi , Zhu Jianjun , Tan Zheng
Published: June 2024

The flow separation at the tongue of the centrifugal pump will cause a sharp reduction of local pressure, thus inducing the cavitation phenomenon, which hurts the stable operation of the pump. This article focuses on the centrifugal pump as the research object. The Delayed Detached Eddy Simulation (DDES) method based on the SST turbulence model was employed to numerically simulate the cavitation at the tongue of the centrifugal pump. The typical characteristics and unsteady changes of cavitation were observed and studied, and the pressure at the tongue position was monitored for flow rates of 1.36 Q
0 and 1.54 Q
0. The results show that, in the cloud cavitation stage, the area of the cavitation bubble presents periodic changes, the main frequency of the cavitation area pulsation is twice the axial frequency, the periodic shedding of the cavitation bubble is caused by the attached vortex (re-entrant jet) and the pressure gradient, and the wall attached vortex will periodically shed and break. The high intensity vortices generated by flow separation at the tongue will change periodically with the rotation of the blade. With the increase of inlet flow, the pressure pulsation at the tongue increases, and the shedding and collapse of the cavitation bubble will enhance the pressure pulsation.
The influence of the gap width of the blade on the performance of the mixing pump
Authors: Li R N , Xing Y F , Zhang W Y , Xue T Q , Hou Y Y , Zhao L L , Bai L , Yang T , Yang Y B , Dong Y F
Published: June 2024

The spiral axial flow gas-liquid mixed pump has some problems, such as unsteady flow and sharp decline in performance, when it runs in the biased condition with high gas content. Based on the principle of fluid flow and the design concept of slot drainage, a slit blade is proposed in this study to improve the degree of gas-liquid separation inside the mixing pump. The slit connects the pressure surface of the blade of the mixing pump with the suction surface. The pressure difference between the pressure surface and the suction surface leads to the generation of slit jet, which plays a “blowing” role in the adhesion of the gas phase on the suction surface inside the mixing pump. And make the stagnant air mass in the flow passage move again, so as to slow down the gas-liquid separation in the mixed transport pump. This study provides theoretical reference for the design and optimization of spiral axial flow gas-liquid mixed pump.
Influence of offset blade on pressure fluctuation in a centrifugal pump under different conditions
Authors: Zhang Yi , Li Guoping , Chen Changsheng , Ma Zhenlai , Chen Biwen , Gao Bo , Lu Yangping , Gao Yuhan , Tan Lei
Published: June 2024

In this paper, the pressure fluctuation under different working conditions of hydrofoil blade impeller (AF), offset blade impeller (SP) and offset winglet impeller (DAF) were measured and the influence of different structures on pressure fluctuation was analyzed. The results show that the discrete frequency caused by rotor-stator interaction (RSI) between impeller and tongue is the blade passing frequency (fBPF
) and its harmonic frequency. Pressure fluctuation amplitude of blade passing frequency is obviously suppressed by offset blade. The value of pressure fluctuation of DAF is small near the tongue under small flow rate, and the energy suppression effect is obvious. With the increase of flow rate, the fluctuation energy of DAF increases gradually, and that of SP decreases gradually.
Practice of first water filling operation of super-high head diversion channel in YangJiang storage power station
Authors: Zhen Peijiang , Cai Mingzhi , Yan Liang , Le Wang
Published: June 2024

In order to summarize the key points of the first water filling operation of 800-meter-class reinforced concrete waterway, and provide reference for the water filling operation of similar pumped storage power stations in subsequent power stations, this paper summarizes and analyzes the first water filling operation of Yangjiang pumped storage power station from the aspects of waterway characteristics, water filling procedure, operation key points and risk control, and explores the standardized flow of the first water filling operation of the pumped storage power station combined with practice to ensure the first success of water filling. This paper focuses on the optimization and implementation of the reverse water filling scheme of the lower adit in the upstream waterway. At the same time, the problems in the process of water filling operation are analyzed, and improvements and suggestions are put forward.
Anti-seepage measures for the upper reservoir of one pumped-storage power station
Authors: Cheng Yanan , Wang Jue , Zhao Long
Published: June 2024

Seepage control plays an important role in the design of pumped storage power station. In this paper, the seepage characteristics and geological conditions of the upper reservoir of a pumped storage power station are analyzed, and the natural seepage of the upper reservoir is calculated. According to the characteristics and amount of leakage, the upper reservoir can be controlled by local seepage control scheme, and the anti-seepage treatment scheme of the south reservoir bank is compared and analyzed. After the local anti-seepage treatment of upper reservoir, the daily seepage volume decreased from 5585m3/d to 2304m3/d, which indicates that the selected anti-seepage scheme is suitable. This paper can provide useful reference for similar projects in the future.
Research on hydraulic variable pressure pumped compressed air energy storage system
Authors: Yang Biao , Li Deyou , Fu Xiaolong , Liu Haibo , Wang Hongjie
Published: June 2024

To cope with the problems of large pressure variation, large throttling loss of the existing pumped compressed air energy storage system, a new hydraulic variable pressure pumped compressed air energy storage system is proposed in this paper. The key components include a variable-speed pump turbine, a hydraulic potential energy transfer device and a water-gas compatible tank. For the proposed system, a thermodynamic model is established. And its correctness is verified by comparing it with measured data. Then, the charging and discharging simulation is carried out. Finally, the variation process of each key parameter of the system is revealed. It is found that the energy efficiency of the system is high, reaching 58.2%, and the energy density is 0.36 kW·h/m3. Through the hydraulic potential energy transfer device, the pressure variation of 2.2 MPa in the tank is converted into the head variation of about 60 m (0.6 MPa) at the variable-speed pump turbine, which improves the operating efficiency of the hydraulic machinery. This technology can provide support for the development of energy storage technology.
On the Water Jet Quality at Part-Load Operation of Pelton turbines
Authors: Semlitsch Bernhard
Published: June 2024

Pelton turbines with multiple nozzles are characterised by their excellent performance over a wide operating range of mass flow rates. Thus, Pelton turbine manifolds must also be designed to deliver good flow quality to the nozzles at part-load operating conditions to accomplish the expectations. A reduced number of nozzles are opened at low mass flow rate operating conditions, where the choice of the open nozzles depends on the water jet quality generated at the individual nozzles. We investigate the flow phenomena occurring in the manifold with the operation of a reduced nozzle number employing numerical simulations to analyse beneficial nozzle opening selections. The turbulent two-phase flow is predicted by the Volume-Of-Fluid (VOF) approach and the k–ω SST turbulence closure model. Different nozzle operating scenarios are simulated, and the implications on the water jet quality, i.e. deviation and shape deformation, are reported. The results show that the free water jet quality criteria can change drastically at individual nozzle operating conditions because of the velocity changes at the branch line junctions.
Comparisons of oxygen increment in a micropump considering the dissolved and released processes
Authors: Ren Z P , Li Z P , Li D Y , Wang H J , Liu J T , Li Y
Published: June 2024

Space micropump are an important component of the on-orbit refuelling system. The gas-liquid behaviour transition induced by dissolved and released processes in the micropump has obtained considerable attention. Our proposed mathematical model achieved the bidirectional dissolved-released processes in an on-orbit space micropump for the first time. The performance characteristics of the micropump and the mathematical computational model used by the plug-discharge flow have been validated. Herein, the correlated mechanism between the flow, mass transfer and solution status were analysed. Under the pressurization of the micropump impeller, the gas was constantly dissolved into the solution, and the higher concentration caused the gas to evolve from the solution. The oxygen increment decreased rapidly when the initial dissolved oxygen centration exceeded 23 mg/L because of the gas evolution occurred. Focused on this sudden decreasing state of oxygen increment from 23 to 24 mg/L, four concentration conditions were discussed in depth including flow field, oxygen increment and mass transfer rate. In the impeller, the equilibrium concentration increases controlled by the pressure was obviously larger than the increase of the real-time concentration; thus, the unidirectional absorbed processes occurred inside the impeller. Two near-rate mass-transfer band were found near the short blades, exhibiting the dynamic equilibrium characteristic. Moreover, affected by the strong disturbance of the impeller outlet, the mass transfer rate was the highest here.
Numerical analysis of the unsteady cavitation performance and structural characteristics of composite propeller
Authors: Dong L , Wu Q , Huang B , Wang G
Published: June 2024

The hydrodynamic performance of a composite propeller under cavitation conditions is analyzed considering the bidirectional transient fluid-structure coupling. The structure field and the flow field are calculated using ANSYS Mechanical/CFX and the information is transferred between them by the interface. It indicates the unsteady cavitating flow features in the presence of the wake condition manifest periodic tendencies. Additionally, the hydrodynamic coefficients of the composite propeller display a phase delay. The composite propeller demonstrates decreased volume of cavitation and enhanced efficiency. The bend-twist coupled deformation in the propeller mitigates the effects of cavitation loads on the performance.
Estimating Wear Rate of Guide Vanes in High-Head Francis Turbines through Flow-Through Testing and DPM Simulation
Authors: Zeng Yongzhong , Liu Xiaobing , Jia Lu , Lai Zhenming , Zhou Bo , Wang Xueren , Yao Yanhua , Yao Bing , Yu Zhishun , Wang Haiqi
Published: June 2024

The development of high-head water resources poses a significant concern due to hydro-abrasive erosion caused by entrained sediment particles. This issue is particularly prevalent in the muddy rivers of the Xinjiang region, China, where Francis turbines are commonly used. With increased soil erosion and rapid sediment transport, the erosion of Francis turbines, especially the guide vanes of high-head turbines, has become increasingly severe. The paper explores key factors that influence the erosion process caused by sediment-laden water. In addition to flow velocity and mud concentration, the properties of the sediment-laden water, such as hardness and size of sand particles, and the concentration ratio of sand particles with different hardness, also play a crucial role in the erosion process. The study is focused on analyzing the erosive effects of sediment-laden water on a high-head Francis turbine’s guide vane. The efficacy of the discrete phase model (DPM) as a simulation method for assessing wear on the guide vane is validated. This model helps analyze critical wear areas on the surface of the vane, enabling the identification of regions most severely affected by erosion due to sediment-laden water. By pinpointing these critical wear areas, the study provides valuable insights into the potential damage caused to the guide vane, thus contributing to better understanding and potential mitigation of erosion in similar turbine systems.
Investigation on the effect of different groove depth and width on the tip clearance leakage flow of hydrofoil
Authors: Dong Liu , Chenhao Li
Published: June 2024

Due to the complexity of axial-flow hydraulic machinery structure and the difficulty of flow field analysis, this paper takes three-dimensional hydrofoil as the research object to analyse the flow characteristics of clearance flow and carry out research on clearance leakage control. The 3-D hydrofoil model with two kinds of gap widths was calculated by using the numerical model method, and compared with the experiment; the influence law of different groove depth and width on the gap leakage flow characteristics and energy characteristics was studied. The results show that with the increase of groove depth, the clearance leakage increases, the lift-drag ratio decreases, and the pressure coefficient increases. Higher axial velocity is shown with increasing groove depth under the small tip clearance, while the opposite is true for large gaps. The optimal groove depth is determined to be D=1mm. When the groove width is 2mm, the pressure coefficient of the hydrofoil is the highest and the vorticity coefficient is the smallest, so the hydrofoil has better performance. In summary, when groove depth D=1mm and groove width W=2mm, the clearance leakage flow rate is smaller and the lift-drag ratio is higher. This study provides a new method for improving the flow field and running stability of turbine-machines with tip clearance in practical engineering.
FSI simulation of a high-head pump-turbine during load rejection process
Authors: Tang M J , Cheng Y G , Liu D M , Chen H Y , Liu K
Published: June 2024

High-head pump-turbine suffers large centrifugal and hydraulic forces due to large rotational speed and severe pressure pulsations during transient processes, and the strong vibration may increase the risk of runner failure. Load rejection transient process is crucial for pumped-storage hydropower stations, and the evolution laws of the runner dynamic stress during this process need profound research. In this study, the evolution of the runner dynamic stress of a prototype pump-turbine during a load rejection transient process was simulated using the one-dimensional and three-dimensional coupling (1D-3D) method and the fluid-structure interaction (FSI) method. The results of this dynamic transient process were compared to the results of the static working points. It is shown that the rotational speed dominates the mean value of stress while the fluctuating amplitude of stress is dominated by pressure fluctuations, which are larger in the S-shaped region of characteristics. Compared with the static working point solutions, the transient process solutions can better reflect the stress fluctuations and should be used for safety assessment.
Study on noise characteristics of centrifugal fan based on blade loading distribution
Authors: Cui Wenhao , Feng Jianjun , Zhu Guojun , Ge Zhenguo , Wang Wei , Li Chenhao
Published: June 2024

In order to explore the influence of different blade loading distribution on the noise characteristics of centrifugal fan, this paper takes the blade loading distribution of the hub and shroud of the centrifugal fan as the design parameters, and establishes four centrifugal fan models with different blade loading distribution. The aerodynamic noise and radiation noise of the centrifugal fan are calculated by the transient results. The research shows that the noise characteristics of the fan change with the change of the blade loading distribution. The maximum aerodynamic noise is generated at the volute tongue, and the total sound pressure level of the gas along the flow direction shows a downward trend. The area with large vibration displacement on the surface of the volute occurs at the back cover plate of the volute, and the noise sound pressure level radiated outward is also higher. The purpose of noise reduction can be achieved by controlling the blade loading distribution.
Numerical prediction of erosion of Francis turbine in sediment laden flow
Authors: He Sanwei , Song Xijie , Wang Li , Zhao Mingliang , Wang Zhengwei
Published: June 2024

Francis turbine is adopted in many hydropower stations widely. Usually, the operating environment is sandy water flow, and the unit will suffer from sediment wear, affecting the operating life of the unit. This article focuses on the wear problem of hydraulic turbines and uses numerical simulation to conduct research on sediment wear. Lagrange model is adopted to predict the sediment concentration in the flowpassageof the unit, and Tabakoff model is used as the wear model. The results indicate that the guide vane blades, seat rings, end clearance, and runner blades and lower rings of hydraulic turbines are prone to sediment erosion. According to friction mechanics, these areas are mainly subjected to impact wear caused by particle impact at the inlet of the guide vane and the runner. The wear on the surface of the blade passage is mainly caused by frictional wear caused by particle sliding motion. The research results provide a certain help for the optimization of hydraulic turbine wear resistance in engineering.
Pressure Pulsation Analysis of 2D NACA66 Airfoil Based on Pulsation Tracking Network
Authors: Lu Jiahao , Liu Qiang , Pan Jiale , Guang Weilong , Tao Ran , Zhu Di , Xiao Ruofu
Published: June 2024

The NACA66 airfoil is used extensively in the design of turbine runners and as a core component, the airfoil plays a vital role in the operation of the turbine. In order to investigate the details of the effect of the NACA66 airfoil on pressure pulsation, this paper investigates and analyses the NACA66 airfoil with a work angle of 14°. This study combines computational fluid dynamics (CFD) with pulsation tracking network (PTN) technology to numerically simulate the NACA66 airfoil. The simulation results show that the dominant pressure pulsation frequencies in the computational domain are mainly 100hz, 3500hz, and 6900hz, and the pressure pulsation amplitude varies for different dominant frequencies. When the dominant frequency is 100hz and 3500hz, the pressure pulsation amplitude continues to decrease from the inlet to the outlet of the calculation domain, but a small increase in pressure pulsation amplitude occurs at the trailing edge of the airfoil. When the dominant frequency is 6900hz, the pressure pulsation amplitude decreases from the inlet to the outlet of the calculation domain and increases sharply below the airfoil, which is greater than the pulsation amplitude in the surrounding area. This paper reveals the dominant frequency of the NACA66 airfoil disturbance based on PTN technology and the variation of the pressure pulsation amplitude at different dominant frequencies. The content of this study can help to explore more deeply the pressure pulsation problem generated by airfoil winding and provide ideas for solving the pressure pulsation engineering problem.
Multivariate iterative nonlinear chirp mode decomposition: principles and applications
Authors: Huang Jie , Li Chaoshun
Published: June 2024

The rotor-bearing system (RBS) of a hydroelectric unit includes multiple components such as the rotor, rotor shaft, coupling, turbine, and main shaft. There is a strong coupling relationship between the vibration signals of multiple bearing sections. At the same time, the vibration signal of the RBS contains rich frequency components, which can effectively reflect the operating state of the shaft system of the unit. Therefore, synchronous signal analysis across multiple rotor bearing sections is required to completely grasp the operating status of the unit. In this study, the Multivariate Iterative Nonlinear Chirp Mode Decomposition (MINCMD) is proposed to analyze signals on multiple sections simultaneously. MINCMD follows the step-by-step extraction idea of Adaptive Multivariate Chirp Mode Decomposition (AMCMD), but it adopts a new algorithm framework by modifying the objective function. Furthermore, AMCMD does not converge well without a good initial instantaneous frequency (IF). Therefore, a method based on parameterized demodulation (PD) is introduced in MINCMD to solve the multi-channel frequency initialization problem. The effectiveness of the proposed algorithm is verified through a simulation test and real data from hydroelectric units.
Measuring uncertainty of hydraulic generator efficiency by calorimetric method
Authors: Guo Xinjie , Pan Chunqiang , Li Hongtao , Xu Xuhui , Jiang Cuiwei
Published: June 2024

Calorimetric method is generally performed on determination of hydraulic generator efficiency. Generator losses could be evaluated by measuring the heat taken by cooling medium or dissipated from a reference surface. To satisfy the requirements of measuring uncertainty in IEC 60034, special attention must be paid. An estimation method is proposed and performed on a hydraulic generator for calorimetric test. Estimation result shows that discharge of cooling water must be reduced to a rather low value to ensure the measuring uncertainty of calorimetry within 3%. Also, a lower cooling discharge can bring higher temperature rise then reduce the measuring uncertainty caused by temperature measurement. Furthermore, to reduce the measuring uncertainty of cooling discharge, flowmeters must be installed correctly.
Assessment of Fiber Bragg Grating sensors for monitoring induced strains on the draft tube cone of hydraulic turbines
Authors: Sánchez-Botello X , Roig R , de la Torre O , Madrigal J , Sales S , Mulu B , Högström C-M , Escaler X
Published: June 2024

In hydraulic turbines, several flow instabilities can take place inside the draft tube cone during off-design and transient operating conditions such as the rotating vortex rope which can severely damage the structure if sustained in time. In the frame of the AFC4Hydro H2020 research project, an extensive measurement campaign has been carried out to monitor and predict this rotating vortex rope phenomenon in a reduced scale Kaplan turbine model at the Vattenfall Research and Development facility in Älvkarleby, Sweden. The hydraulic turbine model has been operated in propeller mode with a fixed blade angle corresponding to its best efficiency point. Several sensors have been placed along the test stand to monitor vibrations, strains and pressures. Concretely, the present paper assesses the performance of using Fiber Bragg Grating sensors to measure the strains induced on the draft tube cone walls with high-spatial resolution in three different zones of influence: the upper and lower flanges and the vertical cone wall between the runner outlet and the elbow. To do so, a total of 3 arrays embedding a total of 48 Fiber Bragg Grating sensors were glued inside three grooves previously machined on these particular areas of the draft tube cone. Analysing the frequency response of the different Fiber Bragg Grating sensors, the strain patterns induced by the rotating and plunging components of the rotating vortex rope have been precisely determined. Moreover, their impacts at the different part load conditions tested have also been quantified.
Research of Model Characteristics based on Probability Statistics Method for Condition Evaluation of Hydropower Unit
Authors: Zhou Ye , Cao Dengfeng
Published: June 2024

The paper introduces the condition evaluation method of hydropower unit based on the health sample with the long time and massive condition monitoring data. By analysing the probability statistics characteristics of units’ status data, it designs the unit operating condition model, and makes the statistics analysis for two-dimension model, which consists of the unit feature value and single influence factor such as water head or active power, furthermore, it built and analyses the three-dimension condition model to get the different influence result by comparing the multi-dimension models. The statistical characteristics of unit operating condition model obtained can be the foundation and basis for implement of hydropower unit health condition evaluation.
Multi-channel deterioration trend prediction of pumping storage unit based on temporal graph convolution network
Authors: Xiao Xiangqu , Li Chaoshun
Published: June 2024

The safe and stable operation of pumped storage units is related to the integrity of the power grid, and it is necessary to study the prediction of unit deterioration trends. Traditional degradation trend prediction methods are mostly for single channel, without considering the interaction between different channels of the shaft system. Therefore, a multi-channel degradation trend prediction model for pumped storage units shaft system is proposed. Firstly, the healthy model is obtained by constructing the mapping relationship between the working parameters and the swing of the shaft system through the fully connected network. Secondly, the deterioration trend sequence of each channel is calculated based on the historical monitoring data of each channel of the unit shaft system and the corresponding healthy model. Finally, the correlation coefficient analysis method is used to calculate the correlation between each channel, and the temporality of the degradation sequence of each channel and the correlation between channels are learned through the spatio-temporal graph convolutional network to realize the prediction of multi-channel degradation trends. The proposed model is verified by using the data of a pumped storage power station. The results show that the proposed model can accurately predict the multi-channel deterioration trend.
Fault diagnosis method of rolling bearing based on MSSA-VMD algorithm
Authors: Yu Tian , Li Chaoshun
Published: June 2024

Early fault signals of rolling bearings are affected by environmental noise, which makes it challenging to extract fault characteristics. In this paper, a bearing fault diagnosis method based on Sparrow Search Algorithm (SSA) and Variable Modal Decomposition (VMD) is proposed to achieve adaptive signal decomposition and feature extraction. First, the fusion shock index is constructed based on the envelope spectrum pulse factor and correlation coefficient to measure the shock fault components. Then, the VMD parameters are adaptively optimized by the improved sparrow search algorithm MSSA, and the fusion shock index is established as the optimal modal component selection method of the fitness function. Finally, the envelope spectrum of the signal after noise reduction is analyzed to extract the fault characteristic frequency. By analyzing the bearing outer ring fault signal and inner ring fault signal under strong noise, the results show that this method can adaptively determine the mode number and penalty factor of VMD, effectively extract the fault signal characteristics, and realize rolling bearing fault diagnosis.
Research on low-carbon optimization methods for regional energy interconnection systems considering multi-energy coupling characteristics
Authors: Guo Feng , Dou Zhenlan , Sun Chen , Zhang Chunyan , Jiang Kuan , Guo Bingtao , Yang Zijie , Zhang Baihan
Published: June 2024

With the increasing application of multi-energy cogeneration, distributed renewable power generation, and multi-energy storage in various multi-energy systems, their efficient collaborative optimization has become the key to further improving emissions. This article utilizes energy hubs to integrate energy equipment with multi-energy coupling and multi-source supply characteristics and constructs a regional interconnected energy system that considers multi-energy coupling characteristics. A multi-objective optimization model for the above-mentioned energy system is established, including economic, low-carbon, and safe aspects such as operating costs, process emissions, and operational safety, and the raccoon optimization algorithm is applied to solve the model. The experimental results show that compared with classical scheduling algorithms, the proposed method can effectively reduce carbon emissions at a certain operating cost.
Research on photovoltaic energy storage capacity allocation considering distribution network reliability and economy
Authors: Liu Zhongjian , Li Qingxi , Jiang Shigong , Qian Ruixin , Ma Liang , Liu Xiaoming , Sun Donglei
Published: June 2024

The rapid development of renewable energy sources, such as solar cells, is creating major challenges for the reliable and economical operation of distribution networks. This paper proposes an optimal PV storage system configuration method that considers the life cycle cost of energy storage devices, establishes a multi-objective optimization model for PV storage system configuration to minimize overall system cost and selection factor, and achieves optimal system power configuration by solving the model using improved NSGA-III optimization algorithm. To compare and analyse optimization results, a regional PV storage system was developed as an example, and results show that when using an improved NSGA-III optimization algorithm to solve the PV storage system model and optimize system power configuration, compared with PV storage system using PSO algorithm, the total economic cost of the system is reduced by 10.4% and can be realized.
Geological engineering double sweet spot evaluation of thin coal seam reservoirs based on facies control: A case study of tight sandstone gas in the Shenfu block of the Ordos Basin
Authors: Xu Wei , Zhang Bing , Zhou Zhan , Wei Chao , Zhang Zhaopeng , Gong Ding
Published: June 2024

The development of thin coal layers within the Shenfu tight sandstone reservoirs significantly impacts the control of hydraulic fractures over the actual sweet spots, leading to considerable inter-well production variability. This paper establishes a connection between individual well sweet spots and block sweet spots through a refined lithofacies model and conducts a comprehensive double sweet spot secondary optimization in conjunction with the characteristics of thin coal layer development. The research findings indicate the following: Class I sweet spots ≥0.46, 0.37≥ Class II sweet spots <0.46, 0.3≥ Class III sweet spots <0.37; fractures will be captured by the coal layer if the thin coal layer is more than 5 m away from the perforation point or if the coal layer thickness exceeds 3 m; the secondary sweet spot optimization can eliminate the influence of thin coal layers and establish a three-dimensional comprehensive double sweet spot model suitable for the study area.
Integrated production simulation of renewable energy and transportation consumption
Authors: Wang Zhiwei , Lv Xiangyu , Li Dexin , Han Shuo , Yang Ziyue
Published: June 2024

In order to improve the reserve adequacy of high proportion new energy power systems and realize the efficient consumption of large-scale new energy, the source of reserve resources is expanded to the source network and load storage, and the operating reserve level that can be provided by the source network and load storage flexible regulating resources is quantified in terms of the direction of regulation and the mode of participation. Then, according to the regulation idea of “synchronous units bear the responsibility during regular hours and multiple types of resources share the responsibility during special hours”, a coordinated and participatory operating reserve capacity allocation strategy of source, network, load, and storage is proposed, and a reserve distribution optimization model incorporating multiple types of heterogeneous resources is constructed to achieve the optimization of reserve distribution of each type of reserve resource in the whole network. The optimization model of standby distribution is constructed to incorporate multiple types of heterogeneous resources and realize the step-by-step refinement of standby resources distribution among the whole grid - resources of the same type - units/stations. A case study is carried out based on a provincial power grid, and the effectiveness of the proposed strategy is verified by comparing it with the existing operational reserve allocation guidelines.
Performance study of air source heat pump system applying two types of distributors
Authors: Xu Chunwei
Published: June 2024

Air source heat pump heating is the most effective way to solve heating problems, and gas-liquid two-phase refrigerant in the uniform distribution and pressure drop problem of finned heat exchanger branch tube are the main factors affecting the heat transfer ability. To study the effects of two types of manifolds applied in air-source heat pumps on the system performance and pressure drop when the system is in operation, an engineering-based test system for the actual operation of air-source heat pumps was constructed. The study shows that the difference between the venturi distributor and the rectifier nozzle distributor in the impact on the system performance is relatively small, while the rectifier nozzle distributor compared to the venturi distributor in the pressure drop on the effect is obvious. The evaporator pressure drop will be transferred to the distributor part of the reduction of pressure drop losses in the evaporator on the impact of heat transfer performance. This paper summarizes the performance study of two types of distributors applied to air source heat pumps, which provides a meaningful reference for similar studies.
Research on air-fuel ratio of rotary engines based on variable universe fuzzy control
Authors: Chai Xiaocan , Liu Jinxiang , Pan Wenchao
Published: June 2024

A study on the air-fuel ratio control system for the Wankel rotary engine was conducted, where the overall model of the engine was developed in MATLAB/Simulink based on the mean value model. The variable universe fuzzy integral composite control algorithm was applied to feedback control, and the construction and simulation of the control algorithm were completed in MATLAB/Simulink. The results indicate that compared to PID control, variable universe fuzzy control reduced the engine’s fuel injection error by 60.37% and 35.7% under steady-state and transient conditions, respectively. This demonstrates the favorable control effectiveness of variable universe fuzzy control in rotary engines, providing insights and methods for future research on rotary engine control systems.
Optimized design of large-diameter directly buried heating pipe
Authors: Tang Chang , Yue Song , Qu Mingxin , Li Kun , Zhang Yifan
Published: June 2024

The elbow of a large-diameter directly buried hot water heating pipeline is the weak part of the whole pipe system. The foam cushion is often used to reduce the stress on the elbow. However, the foam cushion raises the temperature on the outer protective pipe’s surface, which may trigger thermal stress damage to the pipes. In this paper, the insulating pipe at the elbow section is designed with a variable diameter. The numerical simulation of the thermal stress for the outer protective pipe and the working pipe was conducted. The maximum stress for the outer protective pipe is about 3 MPa, and the average stress for the working pipe is 83 MPa, much smaller than the yield stress. Combined with the simulation results, the design ensures the reliability of the elbow and provides a reference for the design of large-diameter and high-temperature heat transfer pipelines.