bluuebunny/crossref_metadata_2025 huggingface dataset:
Design, construction, and dosimetry of 3D printed heterogeneous phantoms for synchrotron brain cancer radiation therapy quality assurance
Authors: Bustillo John Paul O , Paino Jason , Barnes Micah , Cayley James , de Rover Vincent , Cameron Matthew , Engels Elette E M , Tehei Moeava , Beirne Stephen , Wallace Gordon G , Rosenfeld Anatoly B , Lerch Michael L F
Published: June 2024

Objective. This study aims to design, manufacture, and test 3D printed quality assurance (QA) dosimetry phantoms for synchrotron brain cancer radiation therapy at the Australian synchrotron. Approach. Fabricated 3D printed phantoms from simple slab phantoms, a preclinical rat phantom, and an anthropomorphic head phantom were fabricated and characterized. Attenuation measurements of various polymers, ceramics and metals were acquired using synchrotron monochromatic micro-computed tomography (CT) imaging. Polylactic acid plus, VeroClear, Durable resin, and tricalcium phosphate were used in constructing the phantoms. Furthermore, 3D printed bone equivalent materials were compared relative to ICRU bone and hemihydrate plaster. Homogeneous and heterogeneous rat phantoms were designed and fabricated using tissue-equivalent materials. Geometric accuracy, CT imaging, and consistency were considered. Moreover, synchrotron broad-beam x-rays were delivered using a 3 Tesla superconducting multipole wiggler field for four sets of synchrotron radiation beam qualities. Dose measurements were acquired using a PinPoint ionization chamber and compared relative to a water phantom and a RMI457 Solid Water phantom. Experimental depth doses were compared relative to calculated doses using a Geant4 Monte Carlo simulation. Main results. Polylactic acid (PLA+) shows to have a good match with the attenuation coefficient of ICRU water, while both tricalcium phosphate and hydroxyapatite have good attenuation similarity with ICRU bone cortical. PLA+ material can be used as substitute to RMI457 slabs for reference dosimetry with a maximum difference of 1.84%. Percent depth dose measurement also shows that PLA+ has the best match with water and RMI457 within ±2.2% and ±1.6%, respectively. Overall, PLA+ phantoms match with RMI457 phantoms within ±3%. Significance and conclusion. The fabricated phantoms are excellent tissue equivalent equipment for synchrotron radiation dosimetry QA measurement. Both the rat and the anthropomorphic head phantoms are useful in synchrotron brain cancer radiotherapy dosimetry, experiments, and future clinical translation of synchrotron radiotherapy and imaging.
Recovering energy from door opening and closing process using a parallel crank-slider harvester in buildings
Authors: Ren Limin , Wang Shuqing , Zhang Wenqiang , Cao Yubao , Zhang Pan , Wang Xinyu , Tan Yisong
Published: June 2024

Recovering kinetic energy from the environment is mostly focused on the natural environment, while there is also a huge energy in the human living environment. The swing door is an indispensable equipment in the human living environment. The bidirectional swing of the door opening and closing process is rich in energy generated by human motion and thus has a large potential for energy recovery. An energy harvester for recovering bidirectional kinetic energy of the door in buildings is proposed, fabricated, analyzed, and tested. The energy harvester consists of a parallel crank-slider mechanism, a transmission mechanism and a power generation module. The external linkage is used to connect the door and the energy harvester to transmit the bidirectional swing of the door. The parallel crank-slider mechanism is coupled with two one-way bearings. This can realize the conversion of the bidirectional swing of the door to the unidirectional rotation of the central shaft. The final mechanical rectification effect is achieved. Kinematic and dynamic analyses are performed to determine the factors affecting the power generation performance. A prototype is fabricated, and experiments are conducted on it by simulating the process of opening and closing the door. The experimental results are consistent with the simulation ones. At a normal opening velocity of 90° s−1, the maximum open-circuit voltage of the harvester is 7.06 V and the average output power is 1.03 W. The highest efficiency of the harvester can reach 69.65%. The recovered energy is capable of powering the smart door lock for at least 150 s, as well as powering devices such as door lights and doorbells. This can meet the power supply needs of most electronic devices on doors in human life.
Noise analysis and optical response of microwave kinetic inductance detectors with an optical stack
Authors: Nicaise Paul , Hu Jie , Chaumont Christine , Bonifacio Piercarlo , Piat Michel , Geoffray Hervé , Boussaha Faouzi
Published: June 2024

We report on the experimental investigation of optical coupling for superconducting microresonators known as microwave kinetic inductance detectors (MKIDs) in the visible and near-infrared bands. MKIDs are photon-counting, time and energy-resolving detectors that still suffer from a poor quantum efficiency. To improve this efficiency, we propose to add a superconducting reflective layer below the absorbing part of the detector separated by a transparent Al2O3 layer with a quarter-wavelength thickness optimized around a single wavelength λ = 405 nm. We have first fabricated samples patterned from stoichiometric TiN (

T
c

∼
4

K), one with the full optical stack, one without for reference and one with a partial optical stack in order to characterize the noise influence of each layer individually. We observe that the full optical stack geometry has the most impact on the resonator’s noise and quality factors. A second design was fabricated to characterize the optical response to short pulses of the optical stack and we show from both the frequential noise and optical response that a strong signature of TLS is still present in the optical stack sample. We have finally obtained single-photon response with the optical stack using a more sensitive tri-layer TiN/Ti/TiN absorber (

T
c

∼
1.3

K) for which a maximum energy resolving power of

R
=
E

/

Δ
E
∼

1.3 was achieved using 405 nm laser pulses at 225 mK. The quality factors of both the reference and optical stack samples are similar but the frequency noise is still a tenfold higher for the optical stack sample which degrades the energy-resolving power of the detector.
Development of a multi-pancake HTS magnet operated in persistent current mode based on superconducting joint of REBCO coated conductors
Authors: Huang Daxing , Dong Hao , Wang Tongxin , Gu Hongwei , Ding Fazhu
Published: June 2024

Developing closed-loop magnets that operate in a persistent current mode (PCM) is crucial for achieving higher resolution and sensitivity in NMR and MRI devices. To the best of our knowledge, we report a novel closed-loop multi-pancake (MP) HTS magnet operated on PCM based on a novel jointless winding method with superconducting joints of REBCO coated conductors (CCs). The in-field characteristics of the CC and the joints were investigated to determine the operating parameters of the magnet. The steady central field of the magnet reached ∼408.4 mT at 77 K with an operating current of 16.5 A. The joint resistance was inferred from a higher excitation current of 17 A to be at least less than 2.5 × 10−10Ω. Although the I
c value of the joint was considerably lower than that of the CC at self-field, it could maintain similar comparable or even higher in-field I
c compared to the CC, which is immensely beneficial for magnet applications. This study provides some insights into the design and construction of closed-loop MP magnets operating in PCM.
Connecting quantum cities: simulation of a satellite-based quantum network
Authors: Yehia Raja , Schiavon Matteo , Marulanda Acosta Valentina , Coopmans Tim , Kerenidis Iordanis , Elkouss David , Diamanti Eleni
Published: June 2024

We present and analyze an architecture for a European-scale quantum network using satellite links to connect Quantum Cities, which are metropolitan quantum networks with minimal hardware requirements for the end users. Using NetSquid, a quantum network simulation tool based on discrete events, we assess and benchmark the performance of such a network linking distant locations in Europe in terms of quantum key distribution rates, considering realistic parameters for currently available or near-term technology. Our results highlight the key parameters and the limits of current satellite quantum communication links and can be used to assist the design of future missions. We also discuss the possibility of using high-altitude balloons as an alternative to satellites.
Velocity selective multiple two-photon dark and bright resonances in Potassium vapor
Authors: Pal Gourab , Dutta Gupta Subhasish , Chaudhuri Saptarishi
Published: June 2024

We report the observation of two additional sub-natural line width quantum interferences in the D
2 manifold of 39
K vapor, in addition to the usual single Electromagnetically Induced Transparency (EIT) peak. In a typical three level Λ-type system, only one EIT peak is observed. However, here we report observation of two additional line shapes riding on top of the absorption profile. The fact that the hyperfine splitting is smaller than the Doppler width in 39
K allows the probe and control beams to swap their transition pathways in different velocity groups of atoms even when their frequencies are kept constant. Our observations are in striking contrast to standard EIT measurements. These findings are in quantitative agreement with density matrix formalism taking into account velocity-selective two-photon resonances. Owing to the favorably low ground hyperfine splitting (Δ
hf
) in 39
K, which allows a significantly large number of atoms with a Doppler shift greater than or equal to the Δ
hf
, the strength of these additional resonances is strong compared to that of other alkali atoms such as 87
Rb, 133
Cs where these resonances can not be observed. The control photon detuning to atomic transition captures the nature of the coherence; therefore an unusual phenomenon of conversion from perfect transparency to enhanced absorption of the probe photon is observed and explained by utilizing the adiabatic elimination of the excited state in the Master equation. Controlling such dark and bright resonances leads to new applications in quantum technologies such as frequency-offset laser stabilization and long-lived quantum memory.
The PTA Hellings and Downs correlation unmasked by symmetries
Authors: Kehagias A. , Riotto A.
Published: June 2024

The Hellings and Downs correlation curve describes
the correlation of the timing residuals from pairs of pulsars as a function of their angular separation on the sky and is
a smoking-gun signature for the detection of an isotropic stochastic background of gravitational waves. We show that it can be easily obtained from
realizing that Lorentz transformations are conformal transformations
on the celestial sphere and from the conformal properties of the two-point correlation of the timing residuals. This result allows several generalizations, e.g. the calculation of the three-point correlator of the time residuals and the inclusion of additional polarization modes (vector and/or scalar) arising in alternative
theories of gravity.
Beta-band power classification of go/no-go arm-reaching responses in the human hippocampus
Authors: Martin del Campo Vera Roberto , Sundaram Shivani , Lee Richard , Lee Yelim , Leonor Andrea , Chung Ryan S , Shao Arthur , Cavaleri Jonathon , Gilbert Zachary D , Zhang Selena , Kammen Alexandra , Mason Xenos , Heck Christi , Liu Charles Y , Kellis Spencer , Lee Brian
Published: June 2024

Objective. Can we classify movement execution and inhibition from hippocampal oscillations during arm-reaching tasks? Traditionally associated with memory encoding, spatial navigation, and motor sequence consolidation, the hippocampus has come under scrutiny for its potential role in movement processing. Stereotactic electroencephalography (SEEG) has provided a unique opportunity to study the neurophysiology of the human hippocampus during motor tasks. In this study, we assess the accuracy of discriminant functions, in combination with principal component analysis (PCA), in classifying between ‘Go’ and ‘No-go’ trials in a Go/No-go arm-reaching task. Approach. Our approach centers on capturing the modulation of beta-band (13–30 Hz) power from multiple SEEG contacts in the hippocampus and minimizing the dimensional complexity of channels and frequency bins. This study utilizes SEEG data from the human hippocampus of 10 participants diagnosed with epilepsy. Spectral power was computed during a ‘center-out’ Go/No-go arm-reaching task, where participants reached or withheld their hand based on a colored cue. PCA was used to reduce data dimension and isolate the highest-variance components within the beta band. The Silhouette score was employed to measure the quality of clustering between ‘Go’ and ‘No-go’ trials. The accuracy of five different discriminant functions was evaluated using cross-validation. Main results. The Diagonal-Quadratic model performed best of the 5 classification models, exhibiting the lowest error rate in all participants (median: 9.91%, average: 14.67%). PCA showed that the first two principal components collectively accounted for 54.83% of the total variance explained on average across all participants, ranging from 36.92% to 81.25% among participants. Significance. This study shows that PCA paired with a Diagonal-Quadratic model can be an effective method for classifying between Go/No-go trials from beta-band power in the hippocampus during arm-reaching responses. This emphasizes the significance of hippocampal beta-power modulation in motor control, unveiling its potential implications for brain–computer interface applications.
The setting criterion of the downstream surge chamber for pumped storage power station
Authors: Wang Jue , Ding Jinghuan , Han Wenfu , Zhao Long , Du Kenan
Published: June 2024

This paper aims to explore and overcome the limitation of the existing criterion of downstream surge chamber without considering the influence of the head loss in the long waterway system, and deduce the change process of the flow with time (opening) of the unit. On this basis, the setting criterion of downstream surge chamber is derived, which takes into account the water hammer vacuum caused by water inertia in the tailwater system, the velocity head vacuum at the inlet of the draft tube and the friction vacuum of the water delivery system, and the mathematical model of the limit length of the tailwater system is established. The criterion presented in this paper can be used as a preliminary criterion to determine whether the downstream surge chamber is set up or not, and can provide reference for the preliminary design of similar projects in the early stage.
Numerical Investigation of Wake Properties of a Propeller Using Immersed Boundary Method
Authors: Li Haoyu , Kan Kan
Published: June 2024

A level-set based sharp-interface immersed boundary method (IBM) was applied with large eddy simulation to simulate the complex flow field around a marine propeller. The wake characteristics under the open-water conditions including velocity, pressure and turbulent kinetic energy were analyzed. Additionally, the comparative analysis of the axial Reynolds stress of the propeller operating beneath incident waves and that under the open-water condition indicates that the nonlinear interaction between waves and wake leads to the increase in Reynolds stress within the radial range of r/D=0.35 to r/D=0.55 in the far-wake region. The obtained numerical simulation results confirmed the feasibility of the IBM for the numerical simulation of complex flows through hydraulic machinery such as propellers.
Numerical Investigation of Performance and Flow Characteristics of Francis Turbine in Part Load Condition
Authors: Umar Baig Mirza , Huang Xingxing
Published: June 2024

Due to the complexity of the flow phenomena inside Francis turbines, it is very time-consuming and expensive to determine their performance and flow characteristics under different operating conditions through model tests and field measurements. The use of computational fluid dynamics (CFD) to improve turbine design and performance is a more cost-effective alternative to traditional methods of forecasting flow characteristics in different flow domains across the whole turbine channel. The performance and flow characteristics of the turbine under various part load working circumstances are studied by numerical simulations employing the shear stress transfer SST (k − ω) turbulence model. Four different operating conditions from 50%,70%,80% and 100% of the maximum and minimum power were analyzed, and the flow characteristics across the entire turbine channel were investigated in detail. The study results shows the calculated efficiencies of four operating condition have good agreement with measured ones, and the efficiency differences between numerical simulation and measurement are below 0.44%. Visualization of velocity and pressure in the whole Francis turbine shows that output torque, output power, and performance are in good agreement with experiment results. This study’s findings can be utilized to improve the design, efficiency, and hydraulic stability of Francis turbines.
Stability analysis of hydropower unit operation conditions considering hydro-turbine nonlinearity
Authors: Lu Xueding , Li Chaoshun
Published: June 2024

This paper aims to study the law that the stability of hydropower systems changes with the system operating point and clarify the impact of hydro-turbine nonlinearity and hydraulic nonlinearity on the system stability. Firstly, the piecewise linearized model of the hydro-turbine regulation system (HTRS) at various operating points is established. Then, the HTRS stability domain is calculated and analyzed under various working heads and guide vane openings, and the impact of head variation on system stability is researched from the perspectives of discharge and power. Finally, the stability of various operating conditions under ideal hydro-turbine conditions and rated hydraulic parameter conditions are and compared to clarify the role of the water system and turbine nonlinearity on the stability. The results show that hydro-turbine nonlinearity helps to improve the system stability of the overall operating conditions, but the stability of the HTRS is relatively weak during high-load and low-head operations. Moreover, the hydro-turbine nonlinearity plays a dominant role in the process of stability changing with the operating head. This paper provides a comprehensive analysis of the system stability at different operating points, which can help guide the control optimization of hydropower systems.
Analysis of the impact of Tibet Plateau environment on the operating conditions of water turbine machine
Authors: Luo Hongying , Xie Jiuming , Liang Quanwei , Wang Zhengwei
Published: June 2024

Tibet has rich water conservancy resources, and the focus of hydropower development has gradually shifted to Tibet. The primary condition for the stable operation of the water turbine is to satisfy and adapt to the environment. On the basis of investigating the environmental characteristics of the Tibet Plateau, this paper analyzes the impact of its harsh conditions such as altitude, temperature, air density, and sediment. The results show that with the elevation increasing, the minimum inlet pressure of draft tube should be used as elevation correction, and the cavitation volume shows the maximum value at 20°C, and the cavitation velocity decreases when it is larger than 20°C, the decrease of air density makes it difficult to use air convection as the main cooling equipment. The problem found during the maintenance process are analyzed, and the research look forward to providing relevant data and basic technical support for the development of Water resources in Tibet.
Experimental study on draft tube of a model kaplan turbine
Authors: Xu Lianchen , Kan Kan , Zheng Yuan , Liu Demin
Published: June 2024

To obtain the flow characteristics inside the draft tube of the model Kaplan turbine, a model test method was developed and carried out in this paper. The method includes introducing the model test system, test method, and parameters of model Kaplan turbine. Subsequently, experiments are conducted under different operating conditions and the results are analyzed. The result shows that, for the same blade angle and unit speed, operating conditions with larger guide vane openings (GVO) generally have higher axial velocities and lower tangential velocities than those with smaller GVO. In addition, particularly at higher flow velocities, a low velocity or backflow zone can occur in the center of the draft tube. Vortex rope is found to have a significant impact on the turbulence intensity in the mid-section of the draft tube, resulting in an unstable flow state. Also, under higher unit speed operating conditions, the turbulence intensity in the middle of the measurement area is greater and has a larger sphere of influence. Finally, the tangential pulsation intensity at the same measuring point under the same operating conditions is larger than the axial pulsation intensity, showing that vortex ropes have a more significant influence in the tangential direction.
Data-model Interactive Health Condition Assessment for Hydropower Unit
Authors: Liu Yujie , Liu Jie , Zhang Fengyuan , Gao Hua , Li Yuxin , Yuan Xiaohui
Published: June 2024

The health condition assessment (HCA) of hydropower unit plays an important role in enhancing safe operation of hydropower stations and reducing maintenance costs. Due to the harsh environment, there are some problems of sensor data during the unit operations, including abnormal data, missing data and high-noise data. Also, it is difficult to obtain complete monitoring data during run-to-failure maintenance. These issues definitely cause the low-confidence HCA. Thus, a data-model-interactive HCA for hydropower unit was proposed. First, a high-fidelity 3D mechanism simulation model, interacting with the actual unit, was built using unit drawing data provided by manufacturers. Average values of the volute inlet pressure and draft tube outlet pressure were fed into the dynamics simulation model to obtain the simulated pressure pulsation data under working conditions (water head H and power P). Then, a long short-term memory based healthy condition model was constructed using the power parameters, simulation and normal pressure pulsation. After model construction, difference values between simulated pressure pulsation dataset and degradation state pressure pulsation dataset were calculated to build the performance degradation index (PDI), describing the HCA of units. Finally, the PDI was fed into the convolutional neural networks and long short-term memory model to achieve degradation trend prediction. Validation experiment was conducted to verify the effectiveness of proposed method using actual monitoring data and operating parameters of 6# unit in the hydropower station.
Effect of uneven inflow on hydrodynamic performance of bulb turbine
Authors: Liu H , Cheng Y G , Yang Z Y , Zhang J , Fan J Y , Li W X
Published: June 2024

Bulb turbine unit is characterized by its low head, large discharge, and short flow passage. The guiding wall separating the power house section from the flood discharge section may cause uneven inflow before its neighbor units when the power house section is located off the river’s mainstream. In this study, selecting a bulb turbine hydropower station in China as the subject, we establish a three-dimensional CFD model that contains the full flow passage of the turbine unit and partial upstream reservoir, to analyze the effects of uneven inflow on the hydrodynamic performance of the bulb turbine. The results show that under this power station layout, flow separation occurs on the left side of the guiding wall, resulting in a low pressure zone and causing the flow in a three-dimensional vortical pattern. The low pressure and flow energy loss lead to the reduction of the neighbor units’ head, causing the discharge decreasing, and the output cannot reach the expectations. This situation can be improved by shortening the guiding wall, indicating that the unit’s performance is strongly related to the hydraulic structure arrangement. The results can provide some references for the design and operation of the related project.
Experimental analysis of the pressure fluctuations for a prototype pump-turbine at different operating conditions
Authors: Guo Bao , Yu Ran , Ye Ye , Li Xiushu , Xiao Yexiang
Published: June 2024

The pressure fluctuations are one of the crucial instabilities detrimental to the stable operation of pump turbines. The fluctuations are periodic and stochastic. They naturally exist in all kinds of operating conditions and cannot be eliminated. Many studies have been conducted on the pressure fluctuations for pump-turbines. However, detailed analysis of the characteristics of the prototypes is relatively rare and needs further investigation. In this study, six pressure sensors from the spiral inlet to the draft tube outlet have been mounted on a prototype pump-turbine. The recorded pressure values for these sensors were analysed at four different operating conditions from 25% to 100% of BEP (Best efficiency point) loads. Results show the relative fluctuations of vaneless space is only 2.8% at BEP load, showing the prototype operation is stable at the rated power. However, for off-design conditions, the amplitude of dominant frequencies is greatly enhanced. The amplitude is about 18 times at 25% loads compared to that at the BEP load. In addition, the dominant frequencies in the draft tube inlet are characterized by low-frequency components originating from the vortex rope. The current work provides a preliminary understanding of the instability in a prototype pump-turbine and can be used as a reference to minimize the negative effects of pressure fluctuations.
A review of the experimental techniques research progress of the Pelton turbine
Authors: Zhonghua Gui , Yexiang Xiao , Dongkuo Li , Hao Lin , Wei Xiao , Yilin Zhu
Published: June 2024

The Pelton turbine internal flow is by far the most complex of all hydraulic turbo-machinery, which consists of confined flow, free jet flow, free-surface water sheet flow and dispersed flow. The efficiency of Pelton turbine is closely related to these flow phenomena, thus knowing the dynamic behaviour of these flow patterns is of high interest to the optimization of Pelton turbine hydraulic flow parts. The experimental techniques were used to analyse the relationship between the connect of the turbine performance and flow patterns for the earlier researches. The present paper reviewed the development of experimental techniques of Pelton turbines, summarized the emerging test means and discussed the internal flow mechanism.
The model test research of medium-low specific speed Francis pump-turbine
Authors: Guo Y F , Guo Q B , Liu Z L
Published: June 2024

In the last few years, the pumped storage power station grows vigorously. As a result, the higher demand have been put forward in relevant technical fields. This article mainly discusses the model test research of medium-low specific speed Francis pump-turbine. Furthermore, the pump-turbine model test method of performance, cavitation, pressure pulsation, complex characteristics, and the rest auxiliary test is expounded and studied, with a view to optimizing pump-turbine model test method and further improving test rate. It can provide the favorable condition for the pump-turbine unit design and power station continuously operation.
Analysis of self-oscillation stability of a pump-turbine in the S-shaped regions of characteristic curves
Authors: Chen X W , Lai X , Chen H Y , Lin Y F , Liu K , Cheng Y G
Published: June 2024

The hydraulic oscillation of pumped-storage power station (PSPS) affects the safe and stable operation of the power station. The S-shaped characteristic curves of pump-turbine may sometimes result in instability in speed-no-load operation. To investigate the instability mechanisms and identify the main factors that affect stability, this paper used the overall matrix method to establish a self-excited oscillation calculation model of a PSPS and analyzed the stability characteristics and influencing factors of the S-shaped regions of the speed-no-load opening. The results show that when the slope of the characteristic curve is negative, the natural frequency attenuation factors of the system are negative, demonstrating stability. When the slope of the characteristic curve is positive, the system remains stable if the slope is large. However, if the slope of the characteristic curve is below a certain value, which may lead to instability. Increasing the inlet valve resistance and appropriately changing the valve layout position can enhance the stability of the system. The damping surge chamber fluctuations have no impact on system stability. The study also found that the stability regions of the S-shaped regions are related to the slope of the characteristic curve, the unit operating discharge, and the value resistance coefficient.
The Pump-turbine Hydraulic Performance Research, Model Test and Operation in Yangjiang Pumped Storage Power Station
Authors: Xiaolong Yang , Huanmao Wang , Ming Liu , Chao Wang
Published: June 2024

The Yangjiang Pumped Storage Power Station (PSP) is the largest unit rated output PSP that has been built in China, with a maximum water head of nearly 700m and a unit capacity of 400MW. The ultra high water head and its large range of the PSP means a significant difficulty during the dydraulic research and development of the pump-turbine. In this paper, it is introduced on model test and results in the EPFL and IWHR. It is studied on energy performance, cavitation, pressure pulsation and “S” characteristic of pump-turbine with splitter blade. The unit data analys after put into operaton indicat highly hydraulic stability and relative tiny vibration, which just verify the model test. As the model and prototype results show that Yangjiang pump-turbine is outstanding in various indexes and quite excellent in comprehensive hydaulic performance.
Analysis of flow characteristics of a pump turbine under the transient condition of 75% load rejection
Authors: Zhao Qiang , Jin Faye , Cao Jiali , Wu Huanyu , Luo Yongyao
Published: June 2024

In this study, the flow calculations for a pump turbine under the transient condition of 75% load rejection was conducted. The model incorporated a boundary layer on the surface of the guide vane, with the node coordinates of each element in the boundary layer region being updated. This approach ensured the stability of the boundary layer mesh. Experimental measurements provided parameter curves for inlet pressure, outlet pressure, runner speed, and guide vane opening over time. The pressure fluctuation at each monitoring point was compared with the experimental data, and a good agreement was found. Additionally, the variation curve of the axial hydraulic thrust of the head cover and the pressure distribution nephogram of the head cover at typical moments were analysed. The results of this study could be used as a reference for the safe and stable operation of pumped-storage power stations.
Numerical study on the performance characteristics of a high-head pump turbine based on the GEKO model
Authors: He L , Gao Z X , Zhao L C , He L , Wang W P , Meng L , Liao C L
Published: June 2024

As the most mature large-scale energy storage facility in the world, the core equipment of pumped storage power stations, the pump-turbine, is currently developing towards high head and large capacity. And the computational fluid dynamics method (CFD) is one of the most important means to research the internal flow mechanism of pump turbines and optimize the hydraulic performance. Turbulence models play an important role in the study of the flow field. Many high-performance RANS turbulence models (such as SST) cleverly combine the advantages of various models to achieve high precision, but they are not universal and their applicability and accuracy for complex flows are still limited. The Generalized k-ω (GEKO) model model may be a good choice among eddy viscosity models as users can adjust the free parameters according to their specific applications. In this study, the internal flow field of pump turbine is numerically simulated by GEKO model with various values of the separation parameter C
SEP and the curvature correction parameter C
CURV compared with experimental results. The calculation results show that the parameter settings of C
SEP and CCURV in GEKO model have a direct impact on the numerical calculation results. The parameter modification of GEKO model has the potential to improve the adaptability and accuracy of turbulence model, and is useful for improving the engineering application of turbulence model.
A Review of the Recent Research on Hydraulic Excitation-induced Vibration in Hydropower Plants
Authors: Yu Xianhao , Zhang Shaozheng , Zhang Xianyu , Yin Xilong , Qiu Wei , Wang Zhengwei , Lin Qianqian
Published: June 2024

Hydraulic excitation force has an important influence on the operation of pumped storage power station. The hydraulic excitation force acting on the structural components of the unit will not only cause the vibration of the unit and affect the stability of unit operation, also cause the vibration of the power plant and the geological structure, resulting in adverse effects such as noise. Based on the research on the unit and geological vibration caused by hydraulic excitation of pumped storage power station, the causes, classification methods and examples of the influence on the operation of pumped storage power station are analysed. The mechanism of hydraulic excitation force acting on different operating conditions of the unit is compared, then the research progress on the vibration of power house considering loading hydraulic excitation force is summarized. The study on geological vibration of pumped storage power station is listed. Meanwhile, it is pointed out that the development of the method of taking the unit, plant and geological structure as the overall research object has an important impact on the construction of pumped storage power station.
The Influence of Blade Wrap Angle on the Internal Flow Field and Hydraulic Performance of Double-Suction Pump for Yellow River Pumping
Authors: Yan L M , Han W , Tian Y P , Yang X , Zhou J P
Published: June 2024

Analyzing the influence of blade wrap angle on the internal flow field and hydraulic performance of the pump, five different blade wrap angles were designed. Based on RNG k-ε and DPM were used to conduct a steady-state numerical simulation of impellers under the same conditions and different sand volume fractions, respectively. The results show that as the blade wrap angle increases, the flow separation and vortices in the impeller flow passage also decrease, and the flow is closer to the blade profile, but the friction loss in the impeller flow passage also increases. There is an optimal blade wrap angle to maximize the pump head and efficiency. By increasing the wrap angle of blade, the low-pressure zone at the blade inlet area increases, the high-pressure zone at the outlet decreases, and the low-speed zone within the impeller decreases, increasing the outlet velocity. When the sand volume fraction is less than 5%, the effect of sand volume fraction on the hydraulic performance of the pump is not obvious. When the sand volume fraction is more than 5%, the change of wrap angle of blade has a significant effect on the hydraulic performance of the pump.
Rotor-dynamic study for high pressure multistage centrifugal pump
Authors: Liu X F , Ma W S , Chen Y , Xiao F , Su J D
Published: June 2024

Rotor-Dynamic behavior were closely related to the reliability, operability and cost effective for high pressure multistage centrifugal pump. The middle sealing sleeve, high-pressure sealing sleeve, front and rear rings of the impeller of the pump set were studied in this paper, by establishing a theoretical calculation model, numerical calculation methods. The leakage, radial force and tangential force of those seals under different working media and different sealing gaps were ccalculated in detail. The results showed that the sealing performance and dynamic characteristics were influenced by working medium and the sealing gap. The working medium had little effect on the radial force and tangential force of the middle sealing sleeve and high-pressure sealing sleeve, while with a greater effect on the front and rear rings of the impeller. The radial force of the middle shaft sleeve was closed with the sealing clearance. As the seal gap was 0.5mm, negative stiffness at low and high frequency whirlpools was more easily occured. With the gap increasing, the unbalanced response of the rotor increased significantly.
Effect of Blade Thickening Law on the Internal Flow Field and Hydraulic Performance of Double Suction Pumps for Yellow River Pumping
Authors: Yang Xiang , Rennian Li , Tian Yaping , Zhou Juping , Yang Shiqi
Published: June 2024

The thickness of the blades is a fundamental parameter of the impeller and has a substantial impact on the performance of the pump. With the other geometric parameters of a centrifugal pump fixed, six kinds of impellers with different blade thickness were designed. Numerical simulations of the pumps were performed with Fluent under six different operating conditions based on the RNG k-epsilon equation and the SIMPLE algorithm. The hydraulic performance of the pump and its external characteristics were analysed based on the internal flow field to understand the relationship between blade thickness and performance. The results have showed that the hydraulic performance of the pump increases with the backward movement of the maximum thickness of the blade; Under the same sand concentration, the efficiency increases slightly with the increase of blade thickness within a certain range;With the increase of blade thickness, the turbulent kinetic energy loss of the pump under design operating conditions increases continuously; The thickening rules of schemes A1 and B can improve the hydraulic performance of the pump and the transport capacity of the sediment laden two-phase flow. That is, on the premise of meeting the structural strength of the blades, selecting a reasonable blade thickness can ensure that the double suction pump has good hydraulic performance.
Analysis of pressure pulsation in a multi-stage double suction centrifugal pump
Authors: Peng Wenjie , Pei Ji , Yuan Shouqi , Wang Wenjie
Published: June 2024

Pressure pulsation is a common phenomenon, which results from different causes. The intenser pressure pulsation occurs in the pump, the severer the damage to the pump. In the paper, with the assistance of detached eddy simulation method, the characteristic of pressure pulsation in the multi-stage double suction centrifugal pump is studied to understanding the internal flow circumstance. The results reveal that the pressure pulsation intensity reaches the maximum at blade trailing edge, which propagates to the tongue region of forward flow channel and double-volute under the low rates. Furthermore, it can be concluded that the pressure pulsation of region with obvious rotor–stator interaction between rotating impeller and stationary volute is generally larger at low flow rates. The pressure pulsation near the suction side of blade trailing edge shows the feature of broadband frequency and with increasing flow rate the bandwidth of broadband decreases drops rapidly except BP1. Due to the influence of the number of impeller blades, the dominant frequency of monitoring points in the inter-stage flow channel and the volute is basically located at a frequency that is twice the blade frequency. Meanwhile, because of the symmetry of the geometric structure of the reverse flow channel, the pressure pulsation curve changes of its internal monitoring points are similar under the same flow rate.
Analysis of Flow Fluctuation of Confined Backward-Facing Step Based on Pulsation Tracking Network Method
Authors: Liu Qiang , Lu Jiahao , Pan Jiale , Guang Weilong , Tao Ran , Zhu Di , Xiao Ruofu
Published: June 2024

Backward-facing step is a common flow model in hydraulic machinery. Its main feature is that there is a sudden expansion structure at the downstream of the flow channel, which causes the flow instability and is easy to form a vortex behind the sudden expansion section. At present, there are many studies on backstage step flow, but the dominant frequency fluctuation of its flow information has not been noticed. Based on the pulsation tracking network (PTN) method, the numerical simulation of a typical backstage step flow is carried out in this paper. The numerical simulation results are in good agreement with the experimental results. The results of numerical simulation are analyzed in frequency domain by using FFT to obtain the main frequency distribution of flow information on the typical section of the backstage step flow and the distribution of pulsation amplitude at each frequency. It explores a new direction for future research.
Investigation of flow-induced sound source generation in a centrifugal pump
Authors: Yuan Zhiyi , Zhang Yongxue , Zhou Wenbo , Zhang Jinya , Zhu Jianjun
Published: June 2024

This study investigates the mechanism of sound source generation in a centrifugal pump under different flow conditions. The calculated results are in good agreement with experimental data by employing the delayed detached eddy simulation and flow-acoustic coupling method to compute the flow-induced noise. Based on the vortex sound theory and vorticity binary decomposition, the sound source (STA) is divided into a shear-induced source (STS) and a rigid rotation-induced source (STR). The results show that the sound source induced by shear is the main factor. The fluctuation amplitude of STS can be nine times larger than STR at monitor point near the tongue under the design flow rate condition. There is a mutual cancellation effect between the STS and STR. The fluctuation amplitude of STA at the blade passing frequency is 86% of STS at monitor point near the tongue under high flow rate conditions, indicating that sometimes rigid rotation can suppress noise generation.
Design and Performance Prediction of a Vortex Pump Based on CFD for High Concentration Sludge Dredging
Authors: Zhuang H F , Liu M M , Cao L
Published: June 2024

Aiming at solving the problems of clogging and severe wear of the delivery pump in the sludge dredging project, a design method for a vortex pump was summarized. An open impeller and a cross shaped blade was designed with good passing ability, simple structure, and easy maintenance. The volute flow path profile of the vortex pump was designed as a spiral, and the relationship between the width of the vaneless cavity and the diameter of the impeller was established. Based on CFD, the external characteristics of the DRC45-200-VLS vortex pump were simulated and predicted, with a flow rate of 600 m3/h, a head of 20 m, and a water efficiency of 50%. The effects of medium viscosity, solid phase distribution, and gas phase distribution on the flow field of the vortex pump were analyzed. The results showed that the designed vortex pump had good adaptability to transport high concentration sludge and aerated sludge. Combined with a municipal sludge dredging project, a vortex pump transportation scheme for high concentration sludge dredging was formed.
Numerical Simulation of Solid-Liquid Two-Phase Flow in Pump
Authors: Xia Guosheng , Zhang Haili , Zhang Yang , Jiang Wei , Fan Honggang
Published: June 2024

This paper is based on EDEM-FLUENT coupling calculation, the solid-liquid two-phase flow at pump is analyzed. Three kinds of solid phase volume concentration and three solid phase particle diameters are given respectively, and the solid-liquid two-phase flow numerical simulation of the internal flow field of the pump is carried out. The position distribution of solid particles in the flow field and the change of particle average velocity with time and the distribution of particle velocity are analyzed. The results show that the inlet of the runner and the pressure surface of the blade are the concentrated distribution areas of particles. With the increase in particle concentration, the particle distribution at the outlet of the volute is more uniform. The average velocity of particles at different particle concentrations varies similarly with time, but the average velocity of particles increases with the increase of concentration. With the increase in particle size, the average velocity of particles decreases, but the velocity value with the largest proportion of particles becomes larger.
Study on the coupling vibration characteristics of vertical unit and plant of large underground pumping station for water transfer project
Authors: Lu Shaopeng , Wang Tao , Zhang Haili , Wang Yuchuan , Fan Honggang
Published: June 2024

To investigate the coupled vibration characteristics of vertical pumping unit and plant structure of large underground pumping station for water transfer project, the coupled vibration differential equations are established. The structure nodes of are simplified from horizontal direction and vertical direction respectively by force. The structural parameters and load parameters of the model are analyzed and calculated, and the vibration response of each node are calculated by solving the vibration differential equations. A spectral analysis of white noise is applied to the coupled model, and the natural frequencies and vibration structures of dominant vibration modals are obtained. Research indicates that the vertical vibration modes of the system exhibit a relatively low coupling degree with the plant structure. The shaft system and the plant structure mainly display combined vertical vibrations, while the plant structure predominantly exhibits independent vertical vibrations. This implies that vertical vibrations are jointly influenced by shaft system stiffness and plant structure properties. In horizontal vibration modes, a strong coupling characteristic is observed between the upper structure of the pump station unit and the plant structure. This is primarily manifested as coupled vibrations between the support and the plant structure, which are collectively influenced by support constraints, shaft system stiffness, and plant structural properties.
Validation of the steady and unsteady simulation based on an axial-flow pump
Authors: Nguyen Duc-Anh , Kim Sung , Jeong Soon-Young , Kim Jin-Hyuk
Published: June 2024

An axial-flow pump offers high flow rates and efficiency with low power consumption, making it ideal for applications that require transferring the large volume of fluid. Applying the numerical simulation in predicting hydraulic performance, analyzing the phenomena, and optimizing the design of the axial flow pump is very cost-effective and flexible. This study is performed to clarify the difference between steady and unsteady simulations based on the axial flow pump. Numerical simulations are carried out using the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) equations and a shear stress transport reattachment modification turbulence model with small y+ values at all wall surfaces. To show the accuracy, numerical simulations are analyzed and compared with testing results. The difference in steady and unsteady simulations is presented by a detailed analysis of the flow field under the deep stall condition. The result shows that the numerical and testing results are in good agreement with each other. However, the unsteady results are more accurate than the steady results, especially in the saddle zone. Under deep stall condition, it is difficult to accurately predict the hydraulic performance and fluid flow characteristics inside the axial flow pump through steady simulation because of the time-dependent flow.