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ObjectivesA multi-objective optimization algorithm is proposed to address the problem of the complex operating conditions of large horizontal axis hydraulic turbine blades. MethodsAn airfoil optimization model is established based on the multi-island genetic algorithm, the airfoil is parametrically fitted using the class shape function transformation (CST) function method, and the whole optimization process is integrated on the Isight platform to achieve automatic optimization. ResultsUsing the above method, NACA 63813/63815/63816 airfoils are selected as the initial airfoils for multi-objective optimization, CFD numerical validation is carried out on the obtained airfoils using the Fluent turning model, and the lift-to-drag ratios and lifting forces at the airfoil attack angle of 5° are selected as the optimization objectives, resulting in the optimized airfoils gaining increased lift coefficients of 14%, 15% and 20%, and increased lift-to-drag ratios of 14%, 16% and 28%, respectively. ConclusionsNumerical validation shows that the lift-to-drag ratios of the optimized airfoil is higher than those of the original airfoils with the same thickness under several operating conditions, and the structural strength of the blade is improved while ensuring good aerodynamic performance, making it more suitable than conventional airfoils for large-scale tidal current energy horizontal axis hydraulic turbines.

Objective. To set the parameters of the liquefied natural gas shipment system for various options for filling a gas tanker from large-capacity storage facilities during its bunkering.Method. Mathematical and numerical modeling of the liquefied natural gas shipment process for various tank-emptying modes during the shipment of liquefied natural gas to a largecapacity gas carrier by a submersible cryogenic pump.Result. The analysis of the modes of shipment of liquefied natural gas from large-capacity storage facilities has been carried out in order to ensure filling of a gas tanker within the permissible freight period with an upgraded design of a submersible pump of liquefied natural gas. Analytical dependencies have been obtained to describe the process of shipping liquefied natural gas for various operating options of the shipping system.Conclusion. The optimal option for the operation of the liquefied natural gas shipment system for filling a gas tanker within the permissible bunkering time has been determined.

In the past, researchers have done various attempts to improve hydraulic turbine precise speed control and use synchronization time between turbine/generator to grid as a test bench. These attempts were either based on improving the instant when phase difference between two systems becomes zero or to control speed precisely using mathematical model-based techniques. Due to highly nonlinear nature of the hydro turbines, the models presented in the past were never perfect. In this research work, a model free approach is adopted to improve the precise speed control of hydraulic turbines. The developed model free system outperformed old model-based techniques in both stable as well as unstable grids. As per results obtained, grid instability had negligible effect on the speed control and synchronization time. The developed system is able control the hydro turbine speed during synchronization up to a 5 mHz level. [ABSTRACT FROM AUTHOR]

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The water flow within the turbine passage of a hydropower station exhibits high-speed closed-pressure flow. The flow field characteristics will directly affect the turbine's operational efficiency and safety. To ensure the safe operation of the turbine and accurately monitor its flow state, the relationship between the flow characteristics in the turbine passage and its discharge noise must be established. In this study, the relationship between the flow field and the noise field of the turbine is explored using a combination of a model turbine passage discharge noise test and numerical simulation of flow field characteristics. Results show that the operating parameters are closely related to the discharge noise's characteristics, in which the operating head and discharge of the unit's operating parameters greatly influence the discharge noise in the flow passage. Hydrodynamic factors, such as fluctuation pressure and pressure in the flow field, show a strong correlation with the discharge noise characteristics. As the pressure and fluctuation pressure in the inlet area of the spiral case intensify, the sound pressure level (SPL) of the discharge noise increases and the main frequency decreases. A large-scale vortex easily forms in the spiral case and draft tube area, thereby causing low-frequency fluctuation and forming high-decibel noise. Also, the runner area is the main sound source region of the turbine passage. The research results will provide technical and theoretical support for the safe operation and accurate fault diagnosis of hydropower stations. [ABSTRACT FROM AUTHOR]

Abstract With the rapid development of large‐capacity hydraulic turbines and pumped‐storage power stations, hydraulic vibration analysis attracts increasing attention nowadays. To explore the influence of torque and speed variation on hydraulic vibration characteristics during transient processes and ensure the stability of hydropower stations, an improved analytical formula of turbine impedance involving the torque and speed variation was then derived. The free vibration analysis and forced vibration analysis using the transfer matrix method and the hydraulic impedance method were carried out. According to the numerical simulations, the obtained attenuation factors show differences in magnitude which illustrates that the torque variation and speed variation in transients do affect the damping rate of the vibration. In addition, the results indicated the natural angular frequencies of hydropower system were mainly dependent on the length of water conveyance system and pipe characteristics. It can be inferred form vibration mode shapes that for some specific frequencies, the magnitude of oscillatory pressure head and flow rate along the downstream tail tunnel are influenced by the hydraulic turbine. The correlation between the turbine impedance and guide vane openings tells that the hydraulic impedance is getting smaller as the opening increases. What's more, the corresponding free vibration analysis shows that the absolute value of the damping rate is closely related to the value of the flow rate.

To investigate the hydrodynamic noise characterization of hydraulic turbines with runner blade defects, this article establishes the intact machine model and three kinds of models with runner blade defects. Using the Computational Fluid Dynamic (CFD) and Computational Acoustic (CA) hybrid simulation computational methods, the hydrodynamic noise field of the hydraulic turbine is numerically simulated, and the results of the acoustic near field and acoustic far field are shown. 1. The double-row leaf grille and the runner are the primary sound source areas of the hydraulic turbine, and the intensity of sound radiation from these areas is positively correlated with the degree of runner blade defects. 2. As the runner blade defects develop, the sound power level (SWL) increases more significantly in the guide vanes near the nose of the spiral case in the double-row leaf grille. The most pronounced increase in the SWL is observed at the defective craters on the runner blades. 3. The frequency of the defective noise signal is primarily concentrated in the low-frequency band. The dominant frequency amplitude associated with runner blade defects increases and rises after the occurrence of defects. Secondary frequency changes are also observed, and the location of these changes varies at different receiving points. [ABSTRACT FROM AUTHOR]

Hydraulic stations often undertake the tasks of peak and frequency regulation of the power grid, due to the excellent performance and relatively low costs. Thus, operation conditions vary frequently in the turbine. These rapid changes in operating parameters within a short time can seriously affect the stable operation of the power station. In this study, the dynamic characteristics test of a prototype tubular turbine was implemented by the dynamic grid technology, in order to consider the gravity of free surface and water gravity during the transient process of load decrease and load increase under the same output range. The research results showed that: The flow distribution in the unit was different at the same output. The reason was that the different initial flow states were caused by the initial operating conditions in the transient process of load increase and decrease. In the process of load decrease, the center area of the draft tube inlet was affected by the water discharge cone. A low-velocity zone of the same diameter occurred as the water discharge cone. The area of this low-velocity zone was further expanded as the main flow flows downstream into the diffusion section of the draft tube. There were outstanding vortexes and refluxes at the outlet of the draft tube. The starting condition of the load increase process was a partial load condition with a low flow state. The flow state in the unit was more turbulent in the whole load increase process, compared with the load decrease process. The low-velocity areas in the tailpipe in the load increase process were outstandingly larger than those in the load decrease process for the same output. The vortex begins at the inlet area of the tailpipe and spreads into most of the entire tailpipe area. This vortex state in the draft tube posed a great impact on the stability of the turbine. The vortex area and intensity in the draft tube during the load decrease process were significantly smaller than those during the load increase process. Even there was no exception at the vortex scale in the draft tube. After that, the positive and negative back pressure difference between the load-increasing and load-decreasing process was outstandingly larger than that of the load-increasing process under the same output. The pressure of the blade head and suction surface in the load-decreasing process was much smaller than that of the negative pressure state in the load-increasing process, leading easy to cavitation. The water pressure pulsation in the turbine was mainly composed of 0.1fn low-frequency pressure pulsation caused by the vortex rope of the draft tube, and 3fn high-frequency pressure pulsation caused by the rotation of the runner. The amplitude of the pressure pulsation during the load increase process was much larger than that during the load reduction process. The main vibration area was concentrated on the runner of the tubular turbine for the combined action of the two pressure pulsations. Water pressure pulsation was transmitted to the runner area and then coupled with the cantilever beam structure of the runner, leading to the vibration of the runner, which in turn exacerbated the vibration of the water body. And the amplitude of pressure pulsation in the load-increasing process was much larger than that in the load-decreasing process, leading to the low stability of turbine operation in the load-increasing process. The findings can provide a strong reference to design and operate the tubular turbine, particularly for the multi-energy complementary system on the operation requirements. [ABSTRACT FROM AUTHOR]

With the rapid development of large‐capacity hydraulic turbines and pumped‐storage power stations, hydraulic vibration analysis attracts increasing attention nowadays. To explore the influence of torque and speed variation on hydraulic vibration characteristics during transient processes and ensure the stability of hydropower stations, an improved analytical formula of turbine impedance involving the torque and speed variation was then derived. The free vibration analysis and forced vibration analysis using the transfer matrix method and the hydraulic impedance method were carried out. According to the numerical simulations, the obtained attenuation factors show differences in magnitude which illustrates that the torque variation and speed variation in transients do affect the damping rate of the vibration. In addition, the results indicated the natural angular frequencies of hydropower system were mainly dependent on the length of water conveyance system and pipe characteristics. It can be inferred form vibration mode shapes that for some specific frequencies, the magnitude of oscillatory pressure head and flow rate along the downstream tail tunnel are influenced by the hydraulic turbine. The correlation between the turbine impedance and guide vane openings tells that the hydraulic impedance is getting smaller as the opening increases. What's more, the corresponding free vibration analysis shows that the absolute value of the damping rate is closely related to the value of the flow rate. [ABSTRACT FROM AUTHOR]

The hydraulic turbine has been used extensively in the field of energy conservation. For turbines that have low heads and large discharge, improving recovery efficiency and stability is crucial due to their significant hydraulic impact. This paper provides a detailed analysis of the correlation between the influence of radial guide vanes on the stability of low-head, large-discharge turbines focusing on hydraulic performance and energy dissipation before and after the implementation of guide vanes. Moreover, in this paper, two types of turbines, with and without guide vanes, were designed considering the desulfurization scenario. Hydraulic efficiency, radial force, and internal flow field mechanics were numerically studied, and validated through experiments. The results reveal that the working range of the hydraulic turbine could be widened and the energy recovery efficiency improved by a maximum of 3.11% in the small flow rate under the action of guide vanes. Furthermore, it results in a substantial reduction in the radial force of the impeller. Subsequently, the variation in entropy production of different components under full flow rate conditions was compared between the models with and without guide vanes. The total energy consumption decreases sharply under overall working conditions due to the flow control ability of guide vanes affecting the flow state. The entropy production rate of the impeller remains the largest regardless of the presence of a guide vane in the turbine. The vortices inside the guide vanes increase obviously with the flow rate increase. [ABSTRACT FROM AUTHOR]

The present work focuses on the evaluation, by best efficient point (BEP), Nash–Sutcliffe efficiency (NSE), mean square relative error (MSRE), relative mean error (RME) and residual bias (BIAS) of a prototype of a gravitational water vortex turbine. The analysis performed using computational fluid dynamics was experimentally validated to quantify the accuracy of the mathematical model. The estimation of the statistical parameters mentioned was made for different response variables, such as vortex height H v , torque T s , mechanical power P m and efficiency η t , in order to identify biases in different areas of the simulation. The BEP was determined for a flow rate of 6.0 l / s with an efficiency of 58.13% in the experimental part and 54.62% in the numerical modeling, with the vortex height as the critical parameter of the system due to its influence on performance. The NSE and MSRE indicators were positioned as the functions with the best adaptability for the response parameters by criteria and sensitivity. Meanwhile, the RME, MSRE and BIAS presented significant differences for the values of mechanical power and torque. Regarding the electrical efficiency of the generator, it was estimated at 27.68% for the BEP with an average decrease of 3.1% per unit of flow supplied from this point. Therefore, the turbine is subject to the conditions of the generator (torque and number of revolutions per minute) and vortex height, which control the optimization of the system. [ABSTRACT FROM AUTHOR]

The hydraulic turbine has been used extensively in the field of energy conservation. For turbines that have low heads and large discharge, improving recovery efficiency and stability is crucial due to their significant hydraulic impact. This paper provides a detailed analysis of the correlation between the influence of radial guide vanes on the stability of low-head, large-discharge turbines focusing on hydraulic performance and energy dissipation before and after the implementation of guide vanes. Moreover, in this paper, two types of turbines, with and without guide vanes, were designed considering the desulfurization scenario. Hydraulic efficiency, radial force, and internal flow field mechanics were numerically studied, and validated through experiments. The results reveal that the working range of the hydraulic turbine could be widened and the energy recovery efficiency improved by a maximum of 3.11% in the small flow rate under the action of guide vanes. Furthermore, it results in a substantial reduction in the radial force of the impeller. Subsequently, the variation in entropy production of different components under full flow rate conditions was compared between the models with and without guide vanes. The total energy consumption decreases sharply under overall working conditions due to the flow control ability of guide vanes affecting the flow state. The entropy production rate of the impeller remains the largest regardless of the presence of a guide vane in the turbine. The vortices inside the guide vanes increase obviously with the flow rate increase.

By combining computational fluid dynamics (CFD) and surrogate model method (SMM), the relationship between turbine performance and airfoil shape and flow characteristics at low flow rate is revealed. In this paper, the flow velocity tidal energy airfoil model is designed based on the Kriging model, and the original airfoil with a relative thickness of 12% and a relative curvature of 2.5% is obtained. The parameter optimization is carried out by setting the 4th CST equations through the surrogate model; the maximum lift-drag ratio is the optimization goal, the optimization design variable is 10, the maximum number of iterations is 100, and the maximum number of sub-optimization iterations is 200. The results show that the hydrodynamic performance of the airfoil with thinner thickness and more curvature is better, the maximum thickness part is shifted forward by 4.58%, and the lift-drag ratio is improved by 4.03%. The flow field and the efficiency are more stable, which provides an engineering reference for the optimal design of hydraulic turbine airfoils under low flow velocity. It supplements the research on the performance of turbine blades in low velocity. [ABSTRACT FROM AUTHOR]

To improve the identification accuracy of pressure fluctuation signals in the draft tube of hydraulic turbines, this study proposes an improved manta ray foraging optimization (ITMRFO) algorithm to optimize the identification method of a probabilistic neural network (PNN). Specifically, first, discrete wavelet transform was used to extract features from vibration signals, and then, fuzzy c-means algorithm (FCM) clustering was used to automatically classify the collected information. In order to solve the local optimization problem of the manta ray foraging optimization (MRFO) algorithm, four optimization strategies were proposed. These included optimizing the initial population of the MRFO algorithm based on the elite opposition learning algorithm and using adaptive t distribution to replace its chain factor to optimize individual update strategies and other improvement strategies. The ITMRFO algorithm was compared with three algorithms on 23 test functions to verify its superiority. In order to improve the classification accuracy of the probabilistic neural network (PNN) affected by smoothing factors, an improved manta ray foraging optimization (ITMRFO) algorithm was used to optimize them. An ITMRFO-PNN model was established and compared with the PNN and MRFO-PNN models to evaluate their performance in identifying pressure fluctuation signals in turbine draft tubes. The evaluation indicators include confusion matrix, accuracy, precision, recall rate, F1-score, and accuracy and error rate. The experimental results confirm the correctness and effectiveness of the ITMRFO-PNN model, providing a solid theoretical foundation for identifying pressure fluctuation signals in hydraulic turbine draft tubes. [ABSTRACT FROM AUTHOR]

In order to study the effect of splitter blades on the internal and external sound field of the hydraulic turbine, the paper chose a centrifugal pump with a specific speed n s= 33 reversed as a hydraulic turbine as the research object, and added the short blades on the original impeller to form a new splitter impeller. Based on the Re-Normalization Group (RNG) k-ε turbulence model to conduct numerical simulation for the hydraulic turbine, this thesis calculated the internal and external acoustic field by means of the acoustic boundary element (BEM) and finite element (FEM) and analyzed the noise radiation characteristics of the two models under different working conditions. The results show that the blade frequency is the main factor affecting the inlet and outlet sound pressure, and the optimized model decreases the inlet and outlet sound pressure levels by 6.84 and 7.24 dB in optimal working conditions. Rotor-stator interaction is the main reason for the flow-induced noise of hydraulic turbine volute appearing, the optimized model can effectively reduce the impeller and volute rotor-stator interaction and the flow-induced noise of volute. Outfield maximum sound pressure appears at the inlet and the volute tongue, which decreased by 1.84, 6.07, and 5.24 dB at each operating condition. To sum up, splitter blades can improve hydraulic characteristics and flow field noise in the hydraulic turbine. [ABSTRACT FROM AUTHOR]

In the present investigation, a modified Savonius hydrokinetic turbine of 0.245 m turbine diameter (D), 0.1 overlap ratio, 0.2 shape factor, and 0.002 m blade thickness (t) has been investigated numerically to study the influence of extension ratio on the performance of the turbine. The effect of vane end extension on the performance of the Savonius hydrokinetic turbine is investigated by numerical simulations. Two-dimensional transient simulations are done with a pressure-based solver by keeping the diameter of the turbine constant. The study is carried out in a finite-volume solver by using unsteady Reynolds Navier-Stokes equations with a k-ω shear stress transport turbulence model. The coefficient of torque is considered for the 12th revolution of the turbine for different extension ratios of 0, 0.041, 0.082, 0.122, 0.163, and 0.204. The maximum instantaneous coefficient of torque (Ct) is obtained for vane orientations of 100° to 130° and 280° to 310°. The maximum coefficient of power (Cp) of the turbine is 0.2441 for an extension ratio of 0.041, which is 15.5% higher than that of the turbine with a zero-extension ratio. [ABSTRACT FROM AUTHOR]

Earlier studies have shown that 30 L steel, used for the manufacture of hydraulic machinery equipment elements, has greater resistance to cavitation wear than 20 GL steel. This paper presents the results of experimental studies of the solid particle erosion resistance of 30 L structural steel samples with different surface modifications based on nitriding and boriding processes. The characteristics of the modified near-surface layers were determined. The results of the solid particle erosion resistance tests carried out according to the ASTM G76-13 standard are presented. The research results demonstrated that boriding processes worsen the solid particle erosion resistance of 30 L steel at flow impact angles of 30° and 90°. All the considered variants of surface nitriding at an impact angle of 90° do not worsen the solid particle erosion resistance of 30 L steel samples, while at an impact angle of 30°, they increase the solid particle erosion resistance by at least 10–20%. [ABSTRACT FROM AUTHOR]

Based on NACA63816, NACA63815 and NACA63813 airfoils, an airfoil for large hydraulic turbines is designed. The design optimization software iSight was used to establish an airfoil optimization model building on multi-island genetic algorithm, and the computational fluid dynamics numerical simulation approach was applied to analyze the flow field. The lift-to-drag ratio, drag coefficient and maximum thickness Tm at an airfoil angle of attack of 5° are selected as the optimization target parameters to derive the hydrodynamic coefficients of the airfoil. The optimized airfoil lift coefficients increased by 20%/15%/14% and the lift-to-drag ratios rised by 28%/16%/14%. [ABSTRACT FROM AUTHOR]

The crossflow turbine is a popular type of hydropower generator used to convert water energy into electricity. It offers several advantages, including a simple design, reliable performance, and suitability for low-head water flows. This study investigates the effect of runner solidity on the performance of a crossflow turbine. The designed turbine will operate at a three-meter head with a flow rate of 41.55 litters and a runner speed of 300 rpm. The runner design is straightforward, using blades made from four-inch pipes for easy availability and simple manufacturing and repair processes. Variations in runner solidity are achieved by adjusting the number of blades. The investigation uses runners with 15, 20, 25, 30, and 33 blades, representing solidities of 11.7%, 14.6%, 17.5%, and 19.2%, respectively. The results show that the runner developed from a set of blades produced by four-inch pipes, operating under the designed conditions, achieves maximum performance with an efficiency of 81.42% at a solidity of 17.5%, or 30 blades.

Abstract The hydraulic turbine in turbine mode (TMHT) has significant advantages in residual energy recovery, but rapid optimization of its runner parameters has always been a challenge. To address this issue, the optimization algorithm ISMA‐BPNN is proposed based on the improved slime mold algorithm (ISMA) and back propagation neural network (BPNN). First, an efficiency characteristic neural network (ECNN) and a water head characteristic neural network (HCNN), which take the geometric parameters of the runner as input, and the efficiency and water head as outputs, respectively, are constructed by combining the orthogonal test‐based sample data, computational fluid dynamics (CFD), and BPNN. Then, the slime mold algorithm is improved and the optimal runner geometric parameters are obtained based on the ISMA, ECNN, and HCNN, to achieve rapid optimization of the TMHT runner. Finally, the CFD‐based numerical calculation accuracy is verified through real machine tests, and the feasibility of the ISMA‐BPNN‐based rapid optimization strategy for TMHT performance is further verified through CFD numerical simulation.

Introduction. Swirling flows are widely used in hydraulic engineering particularly in the spillway systems of hydroelectric systems and kinetic energy absorbers. An experimental setup for the study of circulation flows by non-contact laser volumetric method is described. The principle of the method and the main characteristics of the recording equipment are given. This installation allows to carry out physical modelling of complex flows to obtain kinematic and dynamic characteristics of the flow.Materials and methods. The study of various physical phenomena requires compliance with certain modelling laws. When modelling hydrodynamic phenomena, it is necessary to observe geometric, kinematic and dynamic similarities. One of the most important concepts of any kind of modelling is similarity criteria. Based on these criteria, an experimental stand is designed. The air flow is generated by AeroLab wind tunnel. PIV system consisting of two Imager HS cameras and NL 200-15 laser is used as measuring equipment. To swirl the flow, a local mono-vortex axial type vane swirler is used. Synthetic oil is used as indicator particles for imaging.Results. An experimental stand for modelling studies of vortex flows in the flow path of a hydraulic turbine, an optimal scheme for the arrangement of measuring equipment was developed and velocity distribution diagrams along and across the flow were obtained.Conclusions. The developed scheme of instrumentation arrangement allows obtaining high-quality images of the flow suitable for further processing. The velocity distribution diagrams constructed as a result of the experiments correspond to those previously obtained by other researchers. The created experimental stand can be used to fulfill a wide range of tasks, for example, to study the possibility of using spiral chambers as spillways with counter-vortex energy dampers.

The water flow within the turbine passage of a hydropower station exhibits high-speed closed-pressure flow. The flow field characteristics will directly affect the turbine’s operational efficiency and safety. To ensure the safe operation of the turbine and accurately monitor its flow state, the relationship between the flow characteristics in the turbine passage and its discharge noise must be established. In this study, the relationship between the flow field and the noise field of the turbine is explored using a combination of a model turbine passage discharge noise test and numerical simulation of flow field characteristics. Results show that the operating parameters are closely related to the discharge noise’s characteristics, in which the operating head and discharge of the unit’s operating parameters greatly influence the discharge noise in the flow passage. Hydrodynamic factors, such as fluctuation pressure and pressure in the flow field, show a strong correlation with the discharge noise characteristics. As the pressure and fluctuation pressure in the inlet area of the spiral case intensify, the sound pressure level (SPL) of the discharge noise increases and the main frequency decreases. A large-scale vortex easily forms in the spiral case and draft tube area, thereby causing low-frequency fluctuation and forming high-decibel noise. Also, the runner area is the main sound source region of the turbine passage. The research results will provide technical and theoretical support for the safe operation and accurate fault diagnosis of hydropower stations.

Dilatometric experiments were conducted with the main purpose of measuring the transformation-induced coefficients of 13% chromium and 4% nickel, which are martensitic stainless steel base and filler materials used for hydraulic turbine manufacturing. To this end, a set of experiments was conducted in a quenching dilatometer equipped with loading capabilities. The measurement system was further improved by means of modified pushrods to allow for the use of specimens with geometries that are compliant with tensile test standards. This improvement allowed for the measurement of the materials' phases and respective yield strengths. The dataset was further used to determine the relationship between the applied external stress and the martensitic start temperature ( M s ) upon cooling. The TRIP coefficient's K values for both the S41500 steel and E410NiMo filler material were measured at 8.12 × 10 − 5 and 7.11 × 10 − 5 , respectively. Additionally, the solid phase transformation model parameters for both the austenitic and martensitic transformation of the filler material were measured. These parameters were then used to model austenitic-phase-transformation kinetics and martensite transformation, including transformation-induced plasticity effects. Good agreement was achieved between the calculation and the experiments. [ABSTRACT FROM AUTHOR]

Studies show that sediment erosion is one of the main factors attributing to hydraulic turbine failure. The present paper represents an investigation into acoustic vibration signals generated by the water flow impacting the hydraulic turbine runner under three different operating conditions. Collected signals were denoised using the ICEEMDAN-wavelet threshold method, and then the spectral characteristics and sample entropy characteristics of the signals for the three operating conditions were analyzed. The results show that when clean water flows through the hydraulic turbine, the sample entropy reaches its smallest values and the dominant frequency component in the spectrogram is 59.39 Hz. When transitioning from clean water to the flood flow containing 2–4 mm sediment particles, the sample entropy is increasing and a high-frequency component higher than 59.39 Hz becomes the prominent frequency of the spectrogram. Meanwhile, the formation of high-frequency components increases with the sand-containing particle size. Based on the spectral characteristics and sample entropy characteristics of the acoustic vibration signals under different operating conditions, it can provide a reference for the sand avoidance operation of the hydraulic turbine during flood season. In addition, it provides a supplement to the existing hydraulic turbine condition's monitoring systems and a new avenue for subsequent research on early warning of hydraulic turbine failure. [ABSTRACT FROM AUTHOR]

The hydraulic turbine in turbine mode (TMHT) has significant advantages in residual energy recovery, but rapid optimization of its runner parameters has always been a challenge. To address this issue, the optimization algorithm ISMA‐BPNN is proposed based on the improved slime mold algorithm (ISMA) and back propagation neural network (BPNN). First, an efficiency characteristic neural network (ECNN) and a water head characteristic neural network (HCNN), which take the geometric parameters of the runner as input, and the efficiency and water head as outputs, respectively, are constructed by combining the orthogonal test‐based sample data, computational fluid dynamics (CFD), and BPNN. Then, the slime mold algorithm is improved and the optimal runner geometric parameters are obtained based on the ISMA, ECNN, and HCNN, to achieve rapid optimization of the TMHT runner. Finally, the CFD‐based numerical calculation accuracy is verified through real machine tests, and the feasibility of the ISMA‐BPNN‐based rapid optimization strategy for TMHT performance is further verified through CFD numerical simulation. [ABSTRACT FROM AUTHOR]

Due to the complexity of working conditions and physical fields, the clearance flow field of the magnetic fluid sealing device for the main shaft of hydraulic turbine has always been a difficult point in the research of magnetic fluid seal. To study the flow characteristics of magnetic fluid in the clearance of the magnetic fluid sealing device for the main shaft of a hydraulic turbine, a numerical model of the flow field in the seal clearance of the main shaft was established and verified through experiments. The influence of the seal clearance, the width of the pole tooth, the height of the pole tooth and the width of the pole tooth slot on the flow of the magnetic fluid was studied by numerical calculation. The results show that the magnetic fluid near the pole tooth is not affected by the structural parameters and basically remains stationary. When the seal clearance is less than 0. 6 mm, the magnetic fluid in the clearance basically does not flow. When the seal clearance exceeds 0. 6 mm, the magnetic fluid near the pole slot and permanent magnet increases with the increase of the seal clearance, and the speed increases linearly. The flow of magnetic fluid near the pole tooth slot and permanent magnet decreases with the increase of the width of the pole tooth, and the velocity decreases linearly at first, decreases sharply at the width of the pole tooth from 3. 0 mm to 3. 5 mm, and finally tends to be stable. With the gradual increase of the height of the pole teeth and the width of the pole tooth slot, the magnetic fluid flow near the pole teeth and the permanent magnet will weaken. The magnetic fluid velocity near the pole teeth and slots will decrease sharply at the the height of the pole tooth from 1. 0 mm to 3. 5 mm and the width of the pole teeth from 3. 0 mm to 12 mm and finally become stable, while the magnetic fluid velocity near the permanent magnet has been decreasing linearly. [ABSTRACT FROM AUTHOR]

The hydraulic turbine in turbine mode (HTTM) with an ultra-low specific speed (HTTM-ULSS) has the advantages of a simplified structure, high efficiency, and good stability and has great application value in the industry. However, the influence of the runner inlet diameter (D1) on the performance of HTTM-ULSS has not yet been fully studied. Therefore, the three-dimensional models of Francis runners were established in the ultra-low specific speed range by examining D1 = 0.49 m, 0.5 m, and 0.51 m, and the two-stage hydraulic turbine models were constructed with flow passage components. Then, internal flow and energy characteristics were calculated using Fluent 16.0 software. Further, the influence of D1 on HTTM performance was studied by comparing numerical simulation results. The results show that the water head of the HTTM-ULSS can reach 540.87 m when D1 = 0.51 m, showing its powerful ability to recover the pressure energy in high-pressure water. Moreover, the head and efficiency are closely related to D1; when D1 increases, the circulation at the runner inlet increases, resulting in an enhancement in the ability to recover the water head and decreases in efficiency and in the operating range of the high-efficiency zone; with D1 increasing, the flow pattern inside the runner becomes better, but the high-pressure area of the blade increases. When selecting the D1, attention should not only be paid to the ability to recover the water head but also to the pressure of the runner blades and the internal water flow pattern. [ABSTRACT FROM AUTHOR]

In order to analyze the response of a hydraulic turbine to a variation in the operating conditions, different laws of variation in time of the mass flow rate have been considered. After validating the overall numerical framework through comparison with relevant experiments, the performances of the considered turbine have been analyzed from a fluid-dynamic point of view. The results show that different time profiles of the mass flow rate (in this work, for simplicity, referred to as "transition functions") have a varying influence on the transient behavior of the turbine. When a quadratic function is considered for the case of large flow, the transient head and torque increase gradually with time, the fluctuation amplitude of the transient hydraulic efficiency at the main frequency is the largest, and the fluctuation amplitude of the radial force is the smallest. For the small flow case, the time profile with exponential nature leads to the best results. The transient head and torque decrease gradually with time, the pulsation amplitude of the transient hydraulic efficiency is the largest at the main frequency, and the pulsation amplitude of the radial force is the smallest. [ABSTRACT FROM AUTHOR]

To address the problem that the hydraulic turbine governing system (HTGS) exhibits poor anti-disturbance ability and instability phenomena under traditional PID control, an improved new integral sliding mode control strategy based on a nonlinear disturbance observer (NISMC-NDO) is designed for the HTGS. This study first establishes a nonlinear mathematical model of HTGS and analyzes its dynamic characteristics. The uncertain disturbances of the system are then accurately estimated using a disturbance observer, and a suitable nonlinear gain function is designed to achieve feedforward compensation of the controller by ensuring that the disturbance observation error converges. To design the controller, a proportional-integral sliding mode surface is selected, and the sliding mode exponential convergence law is improved by using the nonlinear power combination function f a l   instead of s i g n or s a t . This improves the system's stability, convergence speed, and tracking accuracy. The simulation results demonstrate that the equilibrium point can be quickly reached and stabilized by the HTGS with chaotic phenomena under the influence of NISMC-NDO. Furthermore, this paper also verifies that the designed controller has good dynamic performance. The findings of this study can serve as a valuable reference for optimizing the operation of hydraulic turbine regulation systems in control applications. [ABSTRACT FROM AUTHOR]

The hydraulic turbine is considered as a heart of the hydropower plant because of its important function in the whole process of electrical energy production. Turbine´s efficiency calculation is analytically demanding and dependent on parameters that are often obtained only by a theoretical estimation. Therefore, using its accurate model, which takes into account its efficiency, is necessary to achieve realistic and relevant results. The article briefly surveys current knowledge and methods of designing the hydraulic turbine model. The new idea consists in that a fuzzy system was used to create turbine´s efficiency model based on a measured operating data of the turbine flow rate and its mechanical speed without any need of knowing exactly the turbine parameters. Such a model can be used in the design and development process of an optimal energy control of a hydraulic turbine, as well as in the effective process of determination the actual turbine’s wear rate. The achieved results were obtained using the computational tools of the Fuzzy Toolbox in the MATLAB.

To investigate the hydrodynamic noise characterization of hydraulic turbines with runner blade defects, this article establishes the intact machine model and three kinds of models with runner blade defects. Using the Computational Fluid Dynamic (CFD) and Computational Acoustic (CA) hybrid simulation computational methods, the hydrodynamic noise field of the hydraulic turbine is numerically simulated, and the results of the acoustic near field and acoustic far field are shown. 1. The double-row leaf grille and the runner are the primary sound source areas of the hydraulic turbine, and the intensity of sound radiation from these areas is positively correlated with the degree of runner blade defects. 2. As the runner blade defects develop, the sound power level (SWL) increases more significantly in the guide vanes near the nose of the spiral case in the double-row leaf grille. The most pronounced increase in the SWL is observed at the defective craters on the runner blades. 3. The frequency of the defective noise signal is primarily concentrated in the low-frequency band. The dominant frequency amplitude associated with runner blade defects increases and rises after the occurrence of defects. Secondary frequency changes are also observed, and the location of these changes varies at different receiving points.

The erosion of the fixed guide vane of a hydraulic turbine by sandy water is influenced not only by flow velocity and mud concentration but also by the direction and speed of the sandy water over the surface. This study aims to investigate the erosive effect of sediment-laden water on a specific type of hydraulic turbine's fixed guide vane, validate the efficacy of the discrete phase model (DPM) in simulating wear on the fixed guide vane, and identify the critical areas of wear on its surface. To achieve these objectives, the wear model and DPM model are employed to conduct numerical simulations on the fixed guide vane. Additionally, samples of sand are collected from the power station site, and laboratory tests are conducted on the hydraulic turbine's flow passage components using actual sediment concentration and sand-to-water ratio to determine the sediment wear conditions. The numerical simulation results of the guide vane's surface wear rate are compared with the experimental data to verify the wear condition of the fixed guide vane under its rated working condition. These findings serve as a reference for the later-stage design of erosion-resistant solid guide vanes for hydraulic turbines. [ABSTRACT FROM AUTHOR]

A specific example demonstrates the aspects of transient processes in hydropower plants with double-regulated turbines. To prevent malfunctioning of the unit blocks of hydropower plants, such as unit throwing up, recommendations are provided on the choice of modes of movement of the regulating unit to reduce the negative axial forces acting on the turbine impeller. [ABSTRACT FROM AUTHOR]

In this study, a multi-objective optimization design method was developed by combining, among other methods, single-phase flow analysis and the optimization method to simultaneously optimize the runner and collection device of an axial-flow hydraulic turbine with a collection device, using the power coefficient and axial thrust coefficient as objective functions. To verify the effectiveness of this design method, the characteristics of the optimized turbine were investigated through verification experiments and multiphase flow analysis, and were compared with the results of single-phase flow analysis. The results of single-phase flow analysis showed that the axial thrust coefficient of the optimized turbine was equivalent to that of the original turbine, while the power coefficient improved dramatically. However, the results of the multiphase flow analysis showed that although the axial thrust coefficient of the optimized turbine was increased compared to that of the original turbine, the power coefficient was significantly higher than that of the results in the single-phase flow analysis, due to a significant increase in the efficiency of the turbine, as well as an increase in the loading coefficient and the inlet velocity ratio, unlike the single-phase flow analysis. This indicates that this design method is effective in terms of output improvement. [ABSTRACT FROM AUTHOR]

The hydraulic turbine in turbine mode (TMHT) with ultra-low specific speed is a new type of energy recovery device for recovering energy stored in the high-pressure fluid. In order to solve the problem of insufficient consideration of runner geometric parameter optimization, this paper proposes an optimization strategy (OT-CFD), which is based on the orthogonal test method and computational fluid dynamics (CFD), to optimize the performance of the TMHT runner. Firstly, the orthogonal test schemes are established with 5 levels of runner inlet diameter, outlet diameter, inlet height, blade inlet angle, and blade number. Then 25 three-dimensional models of two-stage TMHT containing flow passage components such as Francis runner are built. Further, the internal flow characteristics and energy characteristics of TMHT are calculated and then verified by the real machine test. By comparing the numerical simulation results, the design schemes of runner geometry parameters corresponding to the highest head (H) and the highest efficiency (η) are determined, respectively. On this basis, the optimization effect of runner geometry parameters is analyzed by numerical simulation based on CFD. In conclusion, the inlet angle is the most important factor affecting the efficiency, and the runner inlet diameter is the most important factor affecting the water head. Compared with the comparison scheme, the optimal η scheme has a more stable flow pattern, which provides an efficiency increase of 10.9%, a water head increase of 26.75 m, and a power increase of 646.32kW, greatly reduces the energy loss in the process of residual pressure recovery; the optimal H scheme has an efficiency increase of 2.61%, but more stable and regular flow pattern. More importantly, the optimal water head scheme, which has a water head increase of 185.53 m and a power increase of 1518.3kW, greatly increases the capacity of recovering the water head.

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This article discusses the causes of vibrations depending on unbalanced hydraulic forces in rotating and non-rotating equipment in hydraulic plants within the scope of vibration measurement standards. The radial and axial positions of the turbine shaft, normal operating conditions, the absolute vibration of the signal output velocity during startup and shutdown during unbalance condition of the turbine, the proximity probes have been measured by TMO 793 accelerometer sensor and TMO 793 velocity sensor. The results obtained from the monitoring are analyzed and the first discussion is over the comparison of the current operating levels and vibration standards. Secondly, the comparison is analyzed in order to examine the improvement in vibration level of the elimination of hydraulic imbalance more comprehensively, considering the stability of the hydro turbine-generator unit, a proportional row damping force, proportional-order oil-film force and a hydraulic force and by creating a new non-linear proportional-order mathematical model. Changes in vibration levels and spectral bands for failure types are stated as well. The solution of this integrated and accurate mathematical model shows that it is useful and concise in the diagnosis and prediction of faults in hydropower plants. [ABSTRACT FROM AUTHOR]

The fatigue failure problem of parts of a hydraulic turbine after a long service life is considered. State analysis of elements of hydraulic power equipment and a method for assessing the residual resource of a part in the presence of cracking are presented. The assessment problem of reliability of operation and extending the service life of equipment is discussed. [ABSTRACT FROM AUTHOR]

The article presents information on technical situations during the commissioning of the technological equipment for a hydropower plant (HPP). [ABSTRACT FROM AUTHOR]

The hydraulic turbine is considered as a heart of the hydropower plant because of its important function in the whole process of electrical energy production. Turbine´s efficiency calculation is analytically demanding and dependent on parameters that are often obtained only by a theoretical estimation. Therefore, using its accurate model, which takes into account its efficiency, is necessary to achieve realistic and relevant results. The article briefly surveys current knowledge and methods of designing the hydraulic turbine model. The new idea consists in that a fuzzy system was used to create turbine´s efficiency model based on a measured operating data of the turbine flow rate and its mechanical speed without any need of knowing exactly the turbine parameters. Such a model can be used in the design and development process of an optimal energy control of a hydraulic turbine, as well as in the effective process of determination the actual turbine's wear rate. The achieved results were obtained using the computational tools of the Fuzzy Toolbox in the MATLAB. [ABSTRACT FROM AUTHOR]

By combining computational fluid dynamics (CFD) and surrogate model method (SMM), the relationship between turbine performance and airfoil shape and flow characteristics at low flow rate is revealed. In this paper, the flow velocity tidal energy airfoil model is designed based on the Kriging model, and the original airfoil with a relative thickness of 12% and a relative curvature of 2.5% is obtained. The parameter optimization is carried out by setting the 4th CST equations through the surrogate model; the maximum lift-drag ratio is the optimization goal, the optimization design variable is 10, the maximum number of iterations is 100, and the maximum number of sub-optimization iterations is 200. The results show that the hydrodynamic performance of the airfoil with thinner thickness and more curvature is better, the maximum thickness part is shifted forward by 4.58%, and the lift-drag ratio is improved by 4.03%. The flow field and the efficiency are more stable, which provides an engineering reference for the optimal design of hydraulic turbine airfoils under low flow velocity. It supplements the research on the performance of turbine blades in low velocity.

To improve the identification accuracy of pressure fluctuation signals in the draft tube of hydraulic turbines, this study proposes an improved manta ray foraging optimization (ITMRFO) algorithm to optimize the identification method of a probabilistic neural network (PNN). Specifically, first, discrete wavelet transform was used to extract features from vibration signals, and then, fuzzy c-means algorithm (FCM) clustering was used to automatically classify the collected information. In order to solve the local optimization problem of the manta ray foraging optimization (MRFO) algorithm, four optimization strategies were proposed. These included optimizing the initial population of the MRFO algorithm based on the elite opposition learning algorithm and using adaptive t distribution to replace its chain factor to optimize individual update strategies and other improvement strategies. The ITMRFO algorithm was compared with three algorithms on 23 test functions to verify its superiority. In order to improve the classification accuracy of the probabilistic neural network (PNN) affected by smoothing factors, an improved manta ray foraging optimization (ITMRFO) algorithm was used to optimize them. An ITMRFO-PNN model was established and compared with the PNN and MRFO-PNN models to evaluate their performance in identifying pressure fluctuation signals in turbine draft tubes. The evaluation indicators include confusion matrix, accuracy, precision, recall rate, F1-score, and accuracy and error rate. The experimental results confirm the correctness and effectiveness of the ITMRFO-PNN model, providing a solid theoretical foundation for identifying pressure fluctuation signals in hydraulic turbine draft tubes.

Earlier studies have shown that 30 L steel, used for the manufacture of hydraulic machinery equipment elements, has greater resistance to cavitation wear than 20 GL steel. This paper presents the results of experimental studies of the solid particle erosion resistance of 30 L structural steel samples with different surface modifications based on nitriding and boriding processes. The characteristics of the modified near-surface layers were determined. The results of the solid particle erosion resistance tests carried out according to the ASTM G76-13 standard are presented. The research results demonstrated that boriding processes worsen the solid particle erosion resistance of 30 L steel at flow impact angles of 30° and 90°. All the considered variants of surface nitriding at an impact angle of 90° do not worsen the solid particle erosion resistance of 30 L steel samples, while at an impact angle of 30°, they increase the solid particle erosion resistance by at least 10–20%.

Hydropower, wind power, and photovoltaic power generation are the most common clean energy sources and are important ways to achieve “carbon neutrality” and “carbon peak”. With the adjustment of China’s energy structure, wind power and photovoltaic power generation have entered the peak period of development, but the above two forms of power generation have a certain degree of instability, which has increased the risk of safe and stable operation of the power grid. In contrast, hydroelectric power generation has good stability, and giving full play to the excellent peak and frequency modulation functions of hydro-generator sets is of great significance to ensuring the safe and stable operation of the power grid. This requires the hydro-generator unit to have good reliability during the service period. Through the evaluation of the unit’s health status, the unit’s health status can be predicted, and the maintenance strategy can be given to eliminate the fault in the budding state. This article summarizes the health status assessment methods of hydro-turbine generator sets, and puts forward five health status levels: “healthy”, “good”, “attention”, “abnormal” and “dangerous”. This paper has carried out a quantitative calculation on the health status of a certain hydraulic turbine. The results show that the degree of health of the turbine is “healthy”, “good”, “attention”, “abnormal” and “dangerous” respectively and the degrees are 0.065, 0.632, 0.279, 0.024, 0. According to the principle of maximum membership, it can be judged that the turbine is in “good” status. The evaluation result is consistent with the actual operation of the unit, indicating that the evaluation method studied in this paper has a certain practicability and can provide scientific guidance for the health evaluation of the hydroelectric generating unit.

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Abstract Compared with the traditional reverse multistage pump as hydraulic turbine, hydraulic turbine in turbine mode (T‐type turbine) with low specific speed has higher single‐stage energy head, which can effectively reduce stages and increase the stability when it is used to recycle high residual pressure liquid. Blade number of runner is an important design parameter, which has great influence on the performance of T‐type hydraulic turbine and need to be further studied. Therefore, two‐stage T‐type turbine models with different blade numbers are established through numerical simulation. Then, the accuracy of numerical simulation is verified by test. Finally, the performance and pressure fluctuating characteristics of turbine with different blade numbers are obtained. The results show that: (a) Taking same blade numbers in both stages (traditional design method), the turbine efficiency can be higher with the blade number of primary runner and secondary runner are 14, but resulting the superposition of pulsation in secondary runner; (b) Taking different blade numbers in both stages, respectively, the superposition of pulsation can be effectively avoided, which also leads to the increase in efficiency, and up to 81.169%; (c) The method of using different number of blades in different stages can replace the traditional design method and effectively improve the hydraulic performance of T‐type hydraulic turbine.

Flux cored arc welding (FCAW) is a manufacturing process commonly used for hydro-turbine application, especially in the assembly of Francis runners made of 13%Cr – 4%Ni stainless steel. The welded connection between the blade and band/crown is particularly susceptible to high stress levels due to the design of the runner and the presence of welding defects which act as localized stress concentrations. This research aims to predict the effect of these defects on the performance of the runner during operating condition. To investigate the occurrence of the defects, the distributions of the observed discontinuity are measured and analyzed on T-shape joint specimens using metallographic and X-ray 2D images. The data obtained from these two methods of acquisition are compared to identify any discrepancy. Extreme Value Statistic (EVS) is used to estimate the likely occurrence of the largest defects within the welded runner zone. Based on these findings, a probabilistic Kitagawa–Takahashi diagram with the El-Haddad approximation is adopted to quantify the influence of the defects size in the fatigue assessment. [Display omitted] • Fatigue limit estimations of multi-pass 13%Cr – 4%Ni alloy for Francis runner application in hydroelectric turbines. • Comparison between X-ray and metallography observed defects. • Distribution of defects performed by Extreme Value Statistics (EVS) with competing risk approach. [ABSTRACT FROM AUTHOR]