bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the factors influencing the guide vane hydraulic torque of Francis turbine
Authors: Ji X Y , Xie M X , Song C K , Lai X
Published: June 2024

The model test is commonly used to measure the guide vane hydraulic torque. With the development of numerical simulation technology, it is possible that numerical simulation can substitute for model test to study guide vane torque. In order to study the characteristic of guide vane torque, numerical simulation of tandem cascade based on CFX software are performed for operation points under different guide vane openings. In this paper, numerical calculation of guide vane torque takes singly periodic tandem cascade with the refined mesh of the boundary layer as the research object, and hydraulic force and torque characteristic of guide vane are computed under different guide vane openings. Furthermore, the influence of stay vane profile, turbine rotational speed, guide vane periodicity and mass flow rate on guide vane torque has been researched and analysed. Considering all relative influences, the calculation results of guide vane torque with singly periodic tandem cascade were modified. The result shows the modified method is more reasonable to analyse the guide vane torque by numerical simulation.
Numerical simulation study of hydraulic performance of the ball valve implied in ultra-high head Pelton turbine
Authors: Liu J , Wang J J , Gong S , Wang Z N , Liang Q W
Published: June 2024

This paper is deal with the hydraulic performance of the ball valve served in ultra-high head Pelton turbine systems, the Moving Particle Simulation method is used for numerical simulation uncommonly instead of the Finite Volume method. A valve rotating range of 0 degree to 90 degree is simulated by the software Particleworks, according to the pressure change through the valve, we get the flow resistance coefficient which is consistent with those of other similar literature. The change of the internal flow distribution can be visually observed. At the small rotation degree, the flow velocity entering the ball valve is very high and the disturbance in flow field is large. With the rotation degree increases, the flow in ball valve and the outlet pipe is gradually stabilized, the pressure difference before and after the ball valve is gradually reduced. It brings reference value for the structure and size design of the ball valve in the future.
Analysis of Internal Flow and Vibration Characteristics of Tubular Turbine Considering Dynamic Change of Liquid Level in Reservoir Area
Authors: Zhao Yaping , Ren Yajing , Li Yanrong , Feng Jianjun , Luo Xingqi
Published: June 2024

The tubular turbine of the tidal power station is often affected by different incoming waves in the actual operation, which seriously affects the operation performance. Based on this, the real tubular turbine including upstream and downstream reservoir areas was selected as the research object, and numerical wave generation was conducted using the inlet wave generation method. The second-order Stokes wave was used to study the flow condition and vibration characteristics of the turbine in the upstream reservoir area. The results show that under the action of second-order Stokes wave, the pressure amplitude is obviously increased compared with that without liquid level fluctuation, and the flow velocity in the internal flow field is accelerated. During the wave periods, the pressure values at the runner outlet, the draft tube inlet and outlet all show periodic changes, wave energy decays and the pressure gradually decreases and weakens periodically with the shift of position. The vortex belt of draft tube has the spiral characteristics in the wave process, which will produce more axial vibration and affect the output of the unit in actual operation. These findings have theoretical significance for the actual operation, maintenance and hydraulic design of tidal tubular turbines.
Analysis of ultra-low frequency oscillation mechanism of hydraulic turbine governor under different control modes
Authors: Li G , Feng C , Zheng Y
Published: June 2024

As the southwest power grid with a high proportion of hydropower was transformed into UHV AC-DC network structure, some ultra-low frequency oscillations have appeared in the power grid. In this paper, according to the characteristics of the hydropower unit governor, a small disturbance model was established, and the influence of various parameters of the hydropower unit governor on the system stability in primary frequency modulation was discussed by using the eigenvalue analysis method, and the power mode and the opening mode were compared. The results showed that the parameter adjustable range of the opening mode was larger than that of the power mode. This paper lays a foundation for further research on suppression methods of ultra-low frequency oscillations.
Study on the hydraulic turbine modeling method based on IGSA-NN revision strategy
Authors: Chen Jinbao , Wang Yunhe , Hu Wenqing , Zou Yidong , Zheng Yang , Xiao Zhihuai
Published: June 2024

With the further increase of renewable energy such as wind power and photovoltaic in the power grid, the hydraulic turbine regulating system (HTRS) faces enormous challenges. As simulation modeling is the basis for studying the optimal control of HTRS, it is crucial to establish a high-precision model of HTRS. As the core component of the HTRS, the hydro-turbine contains extremely complex nonlinearity, which model accuracy directly affects the accuracy of the HTRS simulation platform. However, current modeling methods have certain disadvantages such as large modeling errors and making the structure of the HTRS simulation platform more complex. Therefore, this paper proposes a data modification strategy (IGSA-NN) based on the BP neural network (BPNN) and an improved gravity search algorithm (IGSA) and then achieves high-precision modeling of the hydro-turbine combining the BPNN and actual operation data. Finally, the accuracy of the hydro-turbine model is verified by the actual operation data, and the method to build the simulation platform of the HTRS which contains both real and virtual components is given. The research results have a certain guiding significance for hydro-turbine modeling.
Evaluation on structural characteristics of the spiral case influenced by external concrete
Authors: Lu Zhaohui , Luo Yutong , Guo Qiao , Zhang Shaozheng
Published: June 2024

As hydropower is developing vigorously, hydraulic-turbine units have to experience higher head to balance the large power production and consumption on the grid. It requests for higher level of structural strength and stability during operation. Water-filled and pressure-retaining spiral case is commonly used in the power houses of large-scale hydropower stations, which has a good joint bearing capacity of internal water pressure. In this paper, finite element models of the water-filled and pressure-retaining spiral case with and without external concrete under preloading pressure are established, which are used to simulate the structural characteristics when the water-filling process and concrete pouring process are completed. The results show that the maximum stress and deformation of the spiral case are significantly reduced by almost 50% under the support of concrete. Both of them are located at the inner edge and are about 200.80 MPa and 0.60 mm, respectively. The reason why the maximum stress and deformation positions of the spiral case changes after the external concrete being poured is the structural characteristics of concrete, which determine its stress and deformation distribution, and then affect the restraint effect of the corresponding area on the spiral case. The concrete can share parts of the preloading pressure from the spiral case that greatly improves the joint bearing capacity and stability of the overall structure. The conclusions in this paper can also be applied to evaluate the influence of external concrete on the spiral case structural characteristics for similar spiral case structure.
Research on the spiral case and external concrete structural response under limit operation state
Authors: Luo Yutong , Li Zonghua , Zhang Xiaopeng
Published: June 2024

As the key component of hydroelectric generating units, the spiral case is primarily responsible to make the fluid flow out in a uniform and axisymmetric way. The structural response of the spiral case and external concrete under hydraulic pressure will have an effect on the operational security and power generation efficiency of the whole unit. In this paper, a three-dimensional fluid-structure coupling model of the spiral case and concrete under limit operation state is established. Based on the computational fluid mechanics theory, the flow domain inside the spiral case is simulated to study the stress and deformation structural response of the spiral case and external concrete under the action of maximum inner hydraulic pressure. The value and position of the maximum stress and deformation are determined. The fluid-structure coupling simulation shows that severe turbulence occurs in the middle of the flow channel. The maximum equivalent stress of the spiral case is located near its tongue and there would possibly be a risk of local structural damage. The external concrete can effectively share part of the load from the spiral case, so as to keep the strength and stiffness of the overall structure being within safe levels under the limit state. The results can provide support to the structural optimization and construction of the spiral case, which is helpful for the safety and stability of station operation.
Effect of the operating head for hydraulic performance and flow of a Pelton turbine
Authors: Yanhao Li , Zishi Liu , Yexiang Xiao , Quanwei Liang , Jie Liu , Haijun Li
Published: June 2024

The unsteady multi-phase flow simulation in rotating buckets of a model Pelton turbine under various operating heads was performed with the SST-CC turbulence model. The hydraulic performance of the turbine and the flow pattern in the rotating bucket under different operating heads were discussed. The results showed that there was an optimal operating head for the Pelton turbine. The waste of the additional kinetic energy carried by the outflow under off-design heads accounted for the decline in the turbine efficiency. Moreover, the temporal and spatial distribution of the outflowing loss varied with operating head. In the case of high operating head, the outflowing loss last only a short period of time after the water sheet flow started to discharge, and the obvious region of loss was near the bucket root. In the case of low operating head, the outflowing loss occurred during the second half of jet-receiving for the bucket, with the position of high outflowing velocity distributed along the entire brim.
Analysis of the bucket surface cavitation characteristics of a model Pelton turbine
Authors: Jie Liu , Yexiang Xiao , Zishi Liu , Quanwei Liang , Nianhao Yang , Zongqiu Hu , Qingpin Du
Published: June 2024

The internal flow in the rotating bucket of high-head Pelton turbine is complex problem with features of multiphase flow and free surface. As the runner rotating, high speed water jets continuously impact the buckets, which would cause the cavitation on the bucket surface. As proved by field practice, cavitation and cavitation erosion surely exists in the Pelton turbine, which is harmful for the hydraulic performance and the unit. This paper investigated the unsteady 3D water-air-vapour multiphase cavitation flow on the bucket surface of a model Pelton turbine under a high operating head. Results showed cavitation occurred during the process of the bucket cut into the water jet on both sides of the bucket cutout edge. The cavitation on the bucket front surface last for about 20 transient steps with a maximum vapor volume fraction of about 3%, while severe cavitation occurred on the rear surface of the splitter with the duration twice of that on the front surface and a maximum vapour volume fraction of approximately 100%.
Numerical method analysis of the multi-nozzle distributor hydraulic performance for a Pelton turbine
Authors: Yilin Zhu , Jie Liu , Yexiang Xiao , Quanwei Liang , Haijun Li , Qingpin Du , Zhaoning Wang
Published: June 2024

The distributor hydraulic efficiency is very important for a Pelton turbine. In order to improve the turbine efficiency and the jet flow stability from the injector, it’s necessary to optimize the design of the distributor. In this paper, the flow behaviors and the hydraulic efficiency of a model Pelton turbine distributor with and without six-nozzle domain were conducted numerically. Comparison of numerical simulation results of different cases with different boundary condition settings and domain was analyzed. The predicted results show that the results of the distributor with six-nozzle domain are agree well with the measured results and the hydraulic performances is quite different from other cases.
Inversion Calculation and Analysis of Transient Process for Pumped Storage Power Station
Authors: Ma Yanmei , Zhang Hong , Fan Jiayi , Zhang Jian
Published: June 2024

In order to more accurately evaluate the transition process characteristics of pump turbine in pumped storage power station, this paper summarized a systematic inversion calculation and analysis method. Using this inversion calculation method, this paper calculated and analyzed the pressure changes for different load conditions of the same unit, similar conditions of other units in the same hydraulic unit and similar conditions of similar units in other hydraulic units based on the actual measured data of load rejecting test in a pumped storage power station. The inversion calculation results are in good agreement with the experimental measured data, which proves that it is feasible to predict the transient pressure by using this method for inversion calculation.
Effect of guide vane closing speed deviation on transition process in pumped storage power plant
Authors: Li Dongkuo , Zhang Fei , Ni Jinbing , Zhao Yifeng , Gui Zhonghua , Ding Jinghuan , Han Wenfu
Published: June 2024

The guide vane closing law is a crucial role in ensuring the hydraulic transients of pumped storage power plant. It is also essential for ensuring the safe operation of pumped storage power plant after long-term operation. Variations in the closing speed between simulated guide vane closing laws and on-site closing laws have been observed. This study first verifies the accuracy of the simulation model through load rejection tests conducted on two units. It then simulates the deviation in guide vane closing speed for these units. The deviation in guide vane closing speed does not impact the regulatory requirements for a single unit. However, variations in the closing speed between simulated guide vane closing laws and on-site closing laws have been observed. This study first verifies the accuracy of the simulation model through load rejection tests conducted on two units. It then simulates the deviation in guide vane closing speed for these units and proposes a reference range. The deviation in guide vane closing speed does not impact the regulatory requirements for a single unit. However, for two units in one pipe, opposite deviations in guide vane closing speed can result in key parameters failing to meet regulatory requirements.
The influence of the S shaped characteristics of high head pump-turbine on the minimum pressure of draft tube
Authors: Zhang Meiqin , Su Yanyi , Chen Jianfu , Zhang Shubang , Wang Wei , Wei Xianzhu
Published: June 2024

The S shaped characteristics of pump-turbines have an important impact on the minimum pressure of draft tube. The quality of the S shaped characteristics is one of the key indicators to determine the success of model runner development, and this indicator is particularly important for ultra-high head pump-turbines. In order to delve deeper into the inherent relationship between the S-shaped characteristics of the runner and the optimization design and minimum pressure of draft tube, this article first defines a method for fixed-point quantitative analysis of the S shaped characteristic curve. Then, different experimental characteristic curves obtained from multiple optimized designs of the runner are used to calculate the hydraulic transition process. At the same time, the S shaped curve is quantitatively analyzed, and the relationship between the three is explored through continuous analysis. The results show that the bending degree of the equal opening lines in the middle at the S shape characteristics curves has the greatest influence on the minimum pressure at the draft tube inlet. The greater the ratio of unit flow difference to unit speed difference in the S shape characteristics curves of the equal opening line, the greater the runaway unit flow on the same equal opening line, the more favorable it is to increase the minimum pressure at the inlet of the draft tube. The optimal design of blade type and guide vane airfoil can improve the minimum pressure value of draft tube to a certain extent. The conclusions obtained in this paper can be used for reference in the research and development design of high head pump-turbine runner and the optimization calculation of transition.
Spatial distribution of rigid vorticity in pump-turbine under turbine mode with different guide vane openings
Authors: Yan X T , Kan K , Zheng Y , Chen H X
Published: June 2024

Under non-design operating conditions, pump-turbines often exhibit notable instabilities within their runner regions. This study endeavors to investigate the spatial distribution patterns of vortex structures occurring between runner blade channels, focusing on different guide vane opening conditions in the turbine mode of a model pump-turbine. Based on rigid vorticity vectors, the large-scale vortex structures in the channels were analysed. Additionally, this study proposes a novel approach that utilizes the relative streamline coordinates of the blade skeleton to conduct flow analysis. This method offers a quantitative description of the spatial distribution of rigid vortices and associated physical quantities within the blade channels along the streamwise, circumferential, and spanwise directions. Finally, the causes of rigid vortices were analysed. The paper presents a pioneering and advanced theoretical tool and research methodology, serving as a valuable resource for the analysis and understanding of unstable flow structures within pump-turbines.
Study on the influence of pressure-balance pipe diameter on the volumetric efficiency of pump turbine
Authors: Lv Yue , Zhou Lingjiu
Published: June 2024

Hydraulic machinery experiences volume loss due to flow leakage from the clearance between rotating parts and the shell. For pump turbines, fluid leakage from high-pressure to low-pressure areas through the clearance between the upper crown and lower band sealing parts causes volume loss and reduces hydraulic efficiency. The pressure-balance pipe is crucial for balancing axial hydraulic thrust, and its starting end typically lies on the inner side of the upper crown clearance. In this study, we analyze a pump turbine with three flow rates (0.9Q, 0.75Q, and 0.5Q) to illustrate the impact of clearance flow on volumetric efficiency. We consider the effect of varying pressure-balance pipe diameters on volumetric efficiency and analyze the influence of diameter changes on clearance flow. Our findings indicate that changing pressure-balance pipe diameter affects volumetric efficiency and pressure distribution in the upper clearance, with different mechanisms for high and low flow conditions. This study has important implications for pressure-balance pipe design. While ensuring that axial hydraulic thrust balancing is maintained, resizing the pressure-balance pipe diameter can improve unit operation efficiency.
The method for identifying the potential of the fast response capability of a variable-speed pumped storage turbine in pump mode
Authors: Meng L , Zheng Y , Wang X , Zhang C Y , Tian Y J , He L
Published: June 2024

Variable-speed pumped storage technology was being increasingly adopted by new power system to improve the operating and regulating characteristics of the hydropower unit and to stabilize the grid fluctuations. By connecting to a frequency converter, the variable-speed pumped storage unit can respond to grid fluctuations at a speed of hundreds of milliseconds. The fast response capability of a variable-speed pumped storage turbine should be considered in the design stage, be identified during the model test and be used as prerequisite during the commissioning stage of the unit. This article described the method for identifying the fast response capability and methods for improving the power regulation potential of a variable-speed pumped turbine in pump mode. The pipeline hydraulic loss, the guide vanes opening, the energy, cavitation and hump characteristics of the pump are the key parameters and should be carefully considered during the selection of the variable-speed operating zone.
Model experimental study on special frequency of hydraulic pump working condition headcover for ultra-high head pump-turbine
Authors: Lin F Z , Wang X L , Guan Z W , Hu J Y , Wang Z N , Liang Q W
Published: June 2024

With the accelerated construction of pumped-storage power stations, high-head and high-capacity pumped-storage units are gradually becoming the mainstream of development. When operated on-site, the high-head and high-capacity pumped-storage units reflect the phenomenon of special frequency of the head cover vibration of the water pump, which has attracted widespread attention from the industry. In order to deeply reveal the flow mechanism of pumped-storage units, model experiments on the head cover were conducted through the similarity conversion principle between the model and the prototype. The experiment results show that the occurrence of specific frequency in the Head cover of the water pump during operation is due to the rotating flow separation in the vaneless area.
A Field Test Study on the Instability of a Pump-Turbine under Turbine Mode
Authors: Song X H , Xia M , Hu H P , Zhao W Q , Wang Z W
Published: June 2024

In the context of increasing demand for flexible operation of hydropower plants, this study analyses the factors leading to instability in a prototype pump turbine under turbine mode, based on experimental data collected on-site. Pressure sensors and accelerometers were installed to compare pressure signals and vibration acceleration signals. The test results show that the characteristics of pressure fluctuation are dominated by three specific factors under different output power. Vibration reaches its maximum value at approximately 30% of the rated output and its minimum value at around 70% of the rated output, and the causes of twice increases in vibration is not the same. These characteristics often indicate potential unsteady flow, vortex-induced vibration, and flow separation, subsequently affecting the stability of the pump turbine. Understanding the conditions and severity of the occurrence of instability characteristics in the unit is of great significance for power plant personnel to adjust the unit’s operation strategy and improve operational efficiency.
Study on the influence of guide vane - blade number matching relationship (20-9) on the phase resonance risk coefficient of pumped storage units
Authors: Zhang Tao , Li Jinwei , Yang Weibin , Liu Yanyan
Published: June 2024

In this paper, 19 pumped storage units put into operation or under construction in China (the matching relationship between the number of guide vanes and blades is 20-9, and the rated output of a single unit is not less than 200MW) were taken as the research object. Considering the risk of phase resonance caused by pressure wave propagation in the spiral casing of the unit, the phase resonance risk coefficients of units with different rotational speeds were analyzed. The concept of perimeter equivalent coefficient was proposed, and the design criteria for controlling the phase resonance risk coefficient within 25% was obtained, which provided references for optimal hydraulic design of pumped storage units.
Numerical analysis of the transient characteristics of internal flow in the acceleration process of variable speed regulation of a centrifugal pump
Authors: Zhang Haichen , Sun Jian , Dong Wei , Dong Yan , Li Peixuan
Published: June 2024

In this study, a method of combining Flowmaster and ANSYS CFX software was adopted. Based on the consistency between the numerical calculation results of the hydraulic performance of a centrifugal pump and the test results, an operating model of a centrifugal pump system is established, variation law of the external characteristic parameters in the transient process is obtained, and different acceleration times and modes are set. The change law of the transient external characteristics and the evolution mechanism of the internal flow field during the variable speed regulation and acceleration of the centrifugal pump are disclosed. By introducing a control system evaluation index, the effects of acceleration time and mode on performance and internal flow field of variable speed control process of the centrifugal pump are analysed in detail. The results show that the turbulent kinetic energy in the pump changes violently, and the high turbulent kinetic energy and high vorticity are widely distributed, which has an obvious transient effect. An exponential acceleration method can effectively reduce the peak value and overshoot of external characteristic parameters while reducing the speed regulation time.
Performance prediction of IS centrifugal pump based on improved BP neural network
Authors: Yu D H , Chen Y , Wang C , Yang Y C , Ma L L , Ma W S
Published: June 2024

The improved BP neural network was applied to establish prediction models for rated flow and rated head separately, the neural network structures were 8-11-1 and 5-6-1 respectively. 123 sets of pump experimental data were organized as training samples, and the other 15 sets of data were used as test samples. The results show that the training of the two networks converges quickly, the predictive values of the two performance parameters have good consistency with the experimental values, and the average testing errors of rated flow and rated head are 4.2% and 4.7%, respectively. The neural network prediction models established are accurate and effective, meeting the requirements of engineering applications.
Study on the form of sealing ring and its sealing characteristics of centrifugal pump
Authors: Yan Na , Wang Xiaohang , Wu Xidong , Zhu Jiwen
Published: June 2024

The sealing ring, also known as the leakage relief ring, is usually composed of a fixed part and a rotating part, which is used to reduce the gap leakage between the rotating part of the pump and the fixed part, and its structural form and clearance value have a great impact on the stability and efficiency of the pump set. In this paper, the sealing ring between the top cover impeller of a centrifugal pump is used as the research object, and the empirical analysis method and numerical simulation method are used to analyse the water sealing characteristics of the sealing ring structure commonly used in five projects from the aspects of leakage amount and energy consumption, and compare. The results show that the labyrinth, stepped and comb tooth sealing rings have good water sealing effect. Aiming at the matching of different sealing gaps and diffusion domains of stepped sealing rings, the influence of sealing structure size on water sealing characteristics was explored, which provided a technical basis for the selection of sealing ring structure and the determination of matching size of centrifugal pump.
Study of the Effect of Incoming Flow with Fluctuating Gas Void Fraction on Transient Characteristics of a Three-stage Multiphase Pump
Authors: Tan Zheng , Zhang Jinya , Zhou Wenbo , Zhang Yongxue
Published: June 2024

For the oil field with high gas content, the oil well produced has obvious gas content fluctuation characteristics. The unsteady flow of multiphase pump will be caused by the fluctuation flow into the pump. In this paper, the unsteady numerical simulation of the flow field in a three-stage multiphase pump is carried out by using Euler-Euler two-fluid model and SST turbulence model. The results show that the pressurization and torque of each impeller change with the fluctuation of the inlet gas content. The second stage impeller has the highest fluctuation due to the change of flow pattern. The inlet gas rate pulsation frequency and static and static interference have significant effects on the pressure pulsation in the impeller, and the dominant frequency is gas rate pulsation frequency or 11 times rotation frequency. The dominant frequency of the diffuser is the blade passing frequency and its double frequency, and the pulsation frequency of the gas content is the secondary frequency and the amplitude is relatively stable. The axial force increases with the increase of gas content, while the radial force changes in reverse.
Investigation on flow structure and pressure fluctuation of gas-liquid two-phase flow in a mixed flow pump
Authors: Han Yadong , Wu Guoying , Lin Yuanhang , Tan Lei
Published: June 2024

Mixed flow pump is characterized by high-efficiency operation and wide range of flow rate conditions, while research on transporting gas-liquid two-phase flow is quite limited. The present work investigates the energy performance, two-phase flow pattern and pressure fluctuations of a mixed flow pump, on basis of the numerical method of inhomogeneous Eulerian-Eulerian multiphase flow model. Results show that the pump head and efficiency decline with the increase of gas volume fraction. In impeller, gas phase is mainly distributed at the tip clearance, the blade pressure side and suction side, and the hub outlet. The low pressure of tip leakage vortex core leads to the gas phase concentration and the formation of gas strip. Moreover, X-shaped gas strip appears at high gas volume fraction (GVF). In guide vane, gas phase is mainly distributed at the leading edge of blade pressure side, the blade suction side, and the middle of passage. As the inlet GVF increases, the spatial-temporal evolution of the gas phase shows obvious differences. The strong gas-liquid interaction causes broad low-frequency fluctuations, and the rotor-stator interference causes significant blade passing frequencies in the mixed flow pump.
Research progress on hydraulic performance prediction method for large dredge pumps
Authors: Cao Lei , Guo Tao , Zhuang Haifei , Hu Jingzhao
Published: June 2024

The dredge pump is the core equipment in a dredger, which is used to transport dense dredged soil excavated by the dredger. However, the slurry performance of a dredge pump is usually calculated via empirical formula based on the clean-water performance data obtained by numerical simulation or model test, and the conversion accuracy is difficult to evaluate. This paper focuses on reviewing the present technologies of slurry performance test as well as numerical simulation for centrifugal solid-liquid pump. Research progress on special instruments required for testing slurry parameters as well as numerical models for simulating dense solid-liquid flows was summarized. An example was presented to illustrate the scale effect and possible error source in performance conversion between model and prototype pump and then technical difficulties and future research directions in hydraulic performance prediction for dredge pump were put forward.
Structural improvement of a dredge pump based on numerical analysis to prolong its service life
Authors: Hu J , Cao L , Guo T , Zhu Z , Wu Y
Published: June 2024

Dredge pumps are prone to irreparable damage during offshore constructions: the flow passage components are rapidly worn out, and pump shafts often break. It seriously affects the construction efficiency and progress. For the case of high concentration conveying of medium coarse sand, the flow in a dredge pump was numerically studied to analyze the flow force on the impeller and the trajectories of sand particles in the impeller. A discrete phase model was introduced to predict the wear on the impeller, and the life of the pump shaft was predicted using S-N curves and the Rain-flow counting method. A new blade profile and an endwall profile were proposed to use to reduce the wear on the impeller and the structure of the shaft head were optimized to reduce the stress concentration coefficient. The numerical results showed that these measures can significantly improve the service life of the pump.
Analysis of axial force pulsation in a high-pressure decoking pump
Authors: Lin Yanpi , Xu Shengjun , Chen Zhandong , Wei Zhicong , Li Xiaojun , Zhu Zhuchao
Published: June 2024

The high-pressure decoking pump of delayed coking plants in the petrochemical field is a horizontal multistage centrifugal pump. The axial force of the decoking pump is immense, and it needs to start intermittently in the delayed coking process, which will cause axial instability. Through the time domain and frequency domain analysis of the axial force fluctuation signal, the magnitude and stability of the decoking pump axial force under different flow rate and rotational speed conditions are examined in this study. And by introducing the definition of the pressure pulsation intensity coefficient (PPIC) and the Pearson correlation coefficient (PCCs), the correlation of axial force stability and pressure signal pulsation intensity is analyzed. The research can help to establish the rotor axial force instability evaluation system of multistage pump rotor and provide some guidance for the rotor design of the centrifugal pump.
Optimization and Improvement of Three-phase Asynchronous Motor Soft Starter Control Circuit
Authors: Jin Y , Dong J J , Yang X W
Published: June 2024

The soft starters of ABB company are used in a pumped storage power station. Sometimes, a phase absent fault was reported during the process of the motor starting and then led to starting failure. To solve this problem, this article first explained the working principle of the device, and then analyzed the design of the control circuit and the characteristics of the components. Combined with the actual inspection results to find the crux of the problem, It proposed optimization and improvement methods for the soft starter control circuit, and achieved the desired results.
Research on hydraulic characteristics’ sensitivity analysis of the hydraulic inclined shaft turning
Authors: Xuan Zhang , Jie Wei , Han Wu , Lu Zhao
Published: June 2024

The parameters of the hydraulic inclined shaft turning directly affects the flow field characteristics in the bending section and the construction difficulty of the bending section. Three-dimensional computational fluid dynamics (CFD) numerical simulation method was used to systematically study the hydraulic characteristics under different flow velocities, turning radii and turning angles. The results indicate that the flow velocities and the size of the turning radius have little influence on the flow velocity distribution in the bending section. The larger the turning angle, the larger the fast flow velocity area in the bending section. But the extreme values of fast flow velocity remain basically unchanged, and the length required for adjusting the flow velocity distribution after the curved section becomes longer. The faster the flow velocity, the smaller the turning radius, and the larger the turning angle, the greater the centrifugal force generated and the more pronounced the difference in pressure distribution between the inside and outside of the bend section. The head loss in the bending section is consistent with the empirical formula in the specifications. As the radius of curvature gradually increases from 1D to 3D, the head loss (primarily due to local head loss) decreases gradually. When the radius of the bending section continues to increase, the reduction in local head loss becomes less significant, but the increase in frictional head loss leads to a slight overall increase in head loss.
Analysis and Discussion on High Insulation Performance of 20 kV Generator Motor Stator in the Large Pumped Storage Unit
Authors: Zhou Z , Liu T , Chen H Y , Cao Z X , Li H C
Published: June 2024

The terminal voltage of 400 MW 500 r/min generator motor in a large pumped storage power station is 20 kV, in which the height of stator core is 3400 mm and the stator bar adopts less glue VPI (Vacuum Pressure Impregnating) process. The characteristic of this generator motor is high voltage level, large external size and high technical requirements. As the pumped storage unit with the highest voltage level that has been put into operation in China, its stator system of 20 kV generator motor shows excellent insulation performance during the test process. This paper analyzes and discusses from two perspectives of development and installation, and summarizes the key technologies in the process, which can be used for further reference in similar projects.
Analysis and research on the influence of stress relief structure on the grouting hole weld of hydraulic and hydropower penstock
Authors: Cao ZhengXin , Yan Feng , Zhang Xie , Zhou Zan , Liu LiAng , liu Tao
Published: June 2024

After the opening and grouting of the penstock in water conservancy and hydropower projects, the grouting hole needs to be sealed tightly, and the conventional plugging is required. There is large residual stress at the weld of the plugging hole, which is easy to produce welding cracks. In this paper, the sensitivity of stress relief groove added to the grouting hole plugging plug of hydraulic and hydropower penstock to the stress concentration of the plugging hole on the penstock is studied. Then a comparative experiment was carried out. The results of non-destructive testing, residual stress testing, mechanical property testing and metallographic testing of the test sample welds showed that the grouting hole plugging plug was equipped with a stress release structure, the overall strength of the grouting hole plugging weld was basically unchanged, and the stress concentration was significantly reduced. For the plugging and welding of grouting holes in hydraulic and hydropower penstocks, it is recommended to set a stress relief structure on the plugging plug to effectively reduce the impact of stress concentration on welding cracks[1].
Grounding Resistance Monitoring Device for Improved Construction Electricity Safety in Pumped Storage Power Station Construction
Authors: Wang H B , Zhang Z J
Published: June 2024

During the construction period of pumped storage power stations, there are prominent safety hazards in the use of electricity. Most of the underground chambers are in rocky environments, and it is difficult to meet the standard requirements for the grounding resistance of nearby distribution boxes. In addition, due to the high humidity and large amount of dust in the chambers, the grounding terminals are prone to oxidation. Furthermore, frequent blasting operations can cause poor contact of the grounding terminals, resulting in the inability to effectively guide the leakage current into the earth and causing electric shock injury. By using the TN-S wiring method, the leakage current of the equipment and distribution box is guided into the ground grid through the PE line. At the same time, a real-time monitoring system is established for the PE line, which monitors the integrity of the PE line resistance between the third-level distribution box and the transformer ground grid. When an integrity failure occurs, an alarm is quickly issued, enabling maintenance personnel to promptly detect and repair the fault, ensuring that all leakage currents have a good export channel, and further guaranteeing the safety of electricity users.
Effect of the number of orifice plate stages on cavitation characteristics
Authors: Li Dawe , Wang Chengjun , Ju Pengbo , Han Guihua , Jin Di , Wen Jiangbo
Published: June 2024

In order to study the influence of the number of stages of the orifice cavitator on the effect of hydraulic cavitation, this paper adopts the numerical simulation method, with the help of pressure cloud map, gas content cloud map and turbulent kinetic energy cloud map, to observe the distribution location of low pressure area, meteorological area change law, and take the average gas content and maximum gas content rate as the criteria for judging cavitation strength, and quantitatively analyze the influence of different stages on the cavitation characteristics of orifice plate. In this experiment, purified water was used as the medium, and the conductivity of water after cavitation was measured by lightning magnetic conductivity meter to study the characteristics of cavitators of different series of orifice plates and verify the laws of numerical simulation. The experimental results show that at the same inlet flow rate and the same outlet pressure, the number of stages of the cavitator gradually increases, and the cavitation effect is weakened. This is consistent with the numerical simulation results.
Experimental Study on the Movement Law of Solid-liquid Two-phase Flow in slurry Pump
Authors: Xing Jin , Cheng Shufeng , Guo Tao
Published: June 2024

The foundation for the research of two-phase flow pumps is the movement law of solid-liquid two-phase flow in the pump. Currently, research in this direction is mostly conducted through numerical simulation technology, while experimental research is less. In this paper, through the development of a transparent two-phase flow pump, a visual pump test platform with a pipe diameter of 150 mm has been built, and a large number of experimental studies have been conducted on the motion laws of solid-liquid two-phase flow in the pump. The motion laws of particles with different particle diameters in the pump under different flow rates and rotational speeds were obtained through high-speed cameras, including particle velocity and trajectory, and particle collision with the wall. Meanwhile, the wear tests on the pump were carried out with a cast steel and medium high concentration sand pump. The test results show that the location where particles collide with the wall surface more frequently is also the location where wear is more severe. Based on the above test research results, the optimization design direction for two-phase flow pumps is proposed.
Sludge solubilization method using hydrodynamic cavitation
Authors: Son Hyungjoon , Yong Yoon Joon , Sun Xun
Published: June 2024

This study investigates the effects of hydrodynamic cavitation(HC) on sludge solubilization using an advanced rotation hydrodynamic cavitation reactor(ARHCR), varying rotation speeds of rotor. The effectiveness was analysed by measuring biogas yield during anaerobic digestion(AD). The results show that AD performance with treated sludge was improved by HC, indicating that sludge was effectively solubilized. However, the much higher temperature formed by HC leads to the formation of refractory materials that lower AD performance. Overall, this study suggests that HC can be a promising technique to improve sludge solubilization, however, the issue of refractory materials needs to be addressed for optimal performance.
Experimental investigation into lock-in characteristics of the composite hydrofoils
Authors: Ji Miaomiao , Zhang Housheng , Wu Qin , Huang Biao , Wang Guoyu
Published: June 2024

This study experimentally investigates the lock-in characteristics of structural vibration of hydrofoils made of CFRP composite material. The synchronous experimental measurement system constituted of high-speed framing camera, LDV, velocity and pressure regulation systems are set up. It can be found that the Com+45° hydrofoil accelerates the cavitation inception, and the Com-45° hydrofoil defers it. The evolution of the dominant vibration frequency and cloud cavity shedding frequency are semblable. As the cavitation evolution gradually develops, the larger dominant frequency reduces, while the lower frequency remains unchanged. The scope of frequency lock-in meets the magnitude relationship Com+45° hydrofoil> Com-45° hydrofoil> Com0° hydrofoil. The wavelet transformation of structural vibration displacement and non-dimensional cavity area shows that both f
shed and f
shed,lock-in exist in the lock-in condition.
Analysis of propellant management performance in a tank with vertical vanes by drop tower test
Authors: Liu J T , Long J , Chen L , Qu Z , Yao C , Ye W X
Published: June 2024

A drop tower test system for microgravity experiment was established to analyze the performance of a propellant management device (PMD) with vertical vanes. The microgravity level was 10-3 g. Different volume fractions of liquid and different gravity directions were used to study the performance of the PMD. The changes in the gas-liquid interface were studied during the test. It was shown that the vane-type tank is suitable for reverse maneuvering process when volume fraction of propellant is more than 5%, and the propellant relocation time from high gravity condition to microgravity is less than 1.6 s. The inertia force weakens rapidly and the surface tension gradually plays a dominant role at the initial short time period (t<0.4s). The potential energy will be released during the initial short time period (t≤0.5s). The vane-type tank is not suitable for a lateral strong maneuvering process when the propellant volume fraction is less than 2%. The quantity and duration of thruster must be strictly controlled when the volume fraction is less than 10%. The above results provide a favorable reference for the further optimization of PMD designs.
Study on the Flow Characteristics of Piston Type Flow and Pressure Regulating Valve under Sand Containing Conditions
Authors: Fu Y , Du S M , An Z J , Deng L L
Published: June 2024

Based on numerical simulation, the flow characteristics of the valve under different opening degrees of sandy conditions are studied based on the Realizable k-ε turbulence model and Eulerian multiphase flow model, and the flow characteristic curves and flow coefficient-opening degree curves of the valve are obtained, and the influence of the sand rate on the valve flow is analyzed with the numerical calculation results. The results show that with the increase of sand content rate and valve opening, sediment deposition is easily formed in the throttle orifice area, which affects the normal flow inside the valve body and leads to a large deviation of the valve flow rate from the theoretical flow rate. In addition, the relationship between flow rate, sand content and flow coefficient is obtained by fitting the data to the numerical calculation results. The research results have certain reference value for the structural optimization and efficient operation of the valve.
Numerical simulation of gas-liquid interface in a blade type propellant tank
Authors: Chen L , Li Y , He X M , Yao C , Yang N J , Xue L
Published: June 2024

Currently, most of the satellite propulsion systems are mainly on chemical propulsion, and liquid propellant is the necessary power fuel for the propulsion system. The propellant tank of the satellite is a critical unit used to store and manage propellant. The hard core of the blade type tank is the Propellant Management Device (PMD), which serves to provide non entrained propellant for the propulser under specified flow and acceleration conditions during all phases of satellite operation. In this paper, the management performance of propellant under microgravity environment in the tank of a blade type is studied. Using the VOF model, the liquid management performance under microgravity environment in the tank is numerically simulated. The repositioning process is numerical simulated. The good management performance of the tank is verified, and the fluid distribution law is obtained, which can provide guidance for the design of the blade type tank.