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The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices. [ABSTRACT FROM AUTHOR]

The aim of this research was to improve the performance of vortex turbines by testing the performance of vortex turbines using experimental methods, with test variables including blade tilt, flow speed, and vortex turbine impeller material using PLA (polylactic acid). Tests were conducted on a laboratory-scale gravitational water vortex turbine (GWVT) with a pool diameter of 1 meter and a height of 0.8 meters. The test results showed that the turbine with 5 blades produced a maximum torque of 5.89 Nm and an efficiency of 51.10%. The turbine with 7 blades produced a maximum torque of 7.85 Nm and an efficiency of 58.51%. The highest efficiency, 64.69%, was achieved by the 9-bladed turbine, which also had a maximum torque of 8.83 Nm. Experimental tests showed that this laboratory-scale vortex turbine achieved a maximum power output of 87.28 watts, with an efficiency of 56.66% and a torque of 9.81 Nm, using a 9-bladed turbine at a water velocity of 2.5 m/s. These results certainly show an improvement compared to previous reference studies, where the use of materials with lower density, higher blade angle, and larger blade geometry can improve the performance of vortex turbines. [ABSTRACT FROM AUTHOR]

Epoxy resins are crucial for the production of GFRP/XPS foam sandwich structures used for hydraulic turbine extension stay vanes. The quantity and size of ATH fillers have a significant impact on the curing and post-curing characteristics of the epoxy resin. This paper presents the results of an experimental study of the effect of ATH fillers on the maximum temperature, polymerization time, shrinkage, viscosity, and flexural properties of the epoxy resin. The study also uses regression and neural network methods to develop models to predict these properties based on ATH mass fraction and particle size. The results showed that increasing the mass fraction of ATH with a smaller particle size delayed polymerization and reduced the maximum temperature. The addition of ATH resulted in an improvement of the flexural modulus; nevertheless, it caused a reduction in both the flexural strength and breakage strain. Adding ATH improved flexural strength, modulus, and breakage strain. The models developed in this study had a high correlation between predicted and measured responses, providing valuable information for the design and casting of the proposed sandwich structures. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) are highly susceptible to vibrations caused by wind and sea wave oscillations, necessitating effective vibration reduction strategies to ensure stability and optimal performance. This study investigates the effectiveness of a barge-type FOWT integrated with oscillating water columns (OWCs) in reducing oscillations, particularly in rotational modes. A hybrid FOWT-OWCs system was designed, and its vibration mitigation capabilities were assessed through both numerical simulations and experimental tests. The numerical approach focused on controlling airflow in the OWCs, while the experimental tests validated these results under similar conditions. A strong agreement between the simulations and experiments was observed, particularly in reducing platform pitch oscillations, even under irregular wave conditions. The open OWC-based platform outperformed the closed design, reducing pitch angle oscillations from 17.51° to 14.38° for waves with a 10-s dominant frequency. Benchmark tests confirmed this trend, with the open moonpool-based platform achieving a reduction from 18.41° to 12.23°. These findings demonstrate the potential of OWCs to improve the stability and performance of FOWTs, with experimental validation providing confidence in the numerical predictions. [ABSTRACT FROM AUTHOR]

In traditional short-term hydropower scheduling problems, which usually determine the optimal power generation schedules within one week, the off-design zone of a hydraulic turbine is modeled as a forbidden zone due to the significantly increased risk of turbine damage when operating within this zone. However, it is still plausible to occasionally operate within this zone for short durations under real-world circumstances. With the integration of Variable Renewable Energy (VRE) into the power system, hydropower, as a dispatchable energy resource, operates complementarily with VRE to smooth overall power generation and enhance system performance. The rapid and frequent adjustments in output power make it inevitable for the hydraulic turbine to operate in the off-design zone. This paper introduces the operating zones associated with various production costs derived from fatigue analysis of the hydraulic turbine and calculated based on the turbine replacement cost. These costs are incorporated into a short-term hybrid scheduling tool based on Mixed Integer Linear Programming (MILP). Including production costs in the optimization problem shifts the turbine's working point from a high-cost zone to a low-cost zone. The resulting production schedule for a Hydro-Solar hybrid power system considers not only short-term economic factors such as day-ahead market prices and water value but also lifetime hydraulic turbine cost, leading to a more comprehensive calculation of the production plan. This research provides valuable insights into the sustainable operation of hydropower plants, balancing short-term profits with lifetime hydraulic turbine costs. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for the modal analysis of slow-varying vibration structures based on vector autoregressive models. The basic idea of this method consists of using a short-time sliding window (STSW) to identify modal parameters for non-stationary vibrations. This method uses the recursive least-squares estimation for multivariable systems with the singular value decomposition (SVD) method to find the solutions within a segment of the data from each time window. Model identification is conducted by updating the SVD of the data matrix using the order and time from the previous computational window to monitor the modal parameters of a slow-varying system. Finally, this work was validated first by numerically simulating a system's gradual changes submitted to an exciting force and further by an experiment on a hydraulic turbine blade. [ABSTRACT FROM AUTHOR]

Fonseca, M.; McMahon, A.; Erickson, R.; Kelly, C.; Tiggelaar, J., II, and Graham, B., 2024. Effects of the Block Island Wind Farm on benthic and epifaunal communities. Journal of Coastal Research, 40(6), 1037–1054. Charlotte (North Carolina), ISSN 0749-0208. This study reports on monitoring surveys conducted at three of the five commercially operating turbines in U.S. waters off Block Island, Rhode Island, U.S.A., with an emphasis on the final, fourth year of a Bureau of Ocean Energy Management sampling program. The monitoring focused on changes to sediments and infaunal and epifauna species abundance, richness, and diversity caused by the presence of the turbine structure. As anticipated, based on a comparison with other study results, far-field changes in benthic conditions were not evident. Clear changes to the seabed sediments and faunal composition manifested only in the immediate footprint of the turbine foundations. Aside from a localized and sustained shift in particle size, little evidence of a temporally or spatially progressive pattern (as a function of distance away from the turbines) of change in seabed physical and biological composition, or on the turbine structures themselves, was found. The lack of a systematic pattern of influence suggests that many of the intra- and interannual differences may be attributed to natural fluctuations, especially the epifauna on the turbine structures. Notably, the faunal dynamics suggest a community in constant flux and, as seen in other studies, lacking a trend toward the formation of a climax community, which is characterized by stable faunal composition. For these dynamic communities, future sampling may consider using a fixed station, repeated measures approach, as has been done in similarly dynamic, intertidal communities to manage these scales of habitat variability. [ABSTRACT FROM AUTHOR]

Pumped storage is an important green, low-carbon, and clean flexible regulating power source in the power system, which can provide regulation services for the power system, promote the construction of a new type of power system, and facilitate the green transformation of energy. To improve the efficiency and stability of the centrifugal pump turbine under multiple operating conditions, a surrogate model combining radial basis functions with a high-dimensional model is used for performance optimization. Taking the active guide vane of the centrifugal pump turbine as the research object, the airfoil profile is parameterized, and the surrogate model's independent variables and training range are determined. Combining programming and numerical simulation software, an efficiency prediction model for the centrifugal pump and water turbine based on guide vane airfoil control variables is constructed. The particle swarm algorithm is used to globally optimize the constructed model to obtain the optimal efficiency point and corresponding airfoil-related parameters. Finally, numerical simulation and experimental research methods are used to validate the predicted data. The results show that under the premise of ensuring grid performance and operational stability, the numerical simulation efficiency of the pump turbine under the optimization scheme is increased by 1.6 and 0.32%, respectively, compared to the numerical efficiency of the prototype guide vane. In the experimental case, the efficiency of the water turbine and pump is increased by 0.76 and 0.14%, respectively, compared to the prototype guide vane. [ABSTRACT FROM AUTHOR]

Desanding facilities (DFs) limit particle sizes and reduce the suspended sediment load in hydropower plants. Multiple successive tranquilizing racks (TRs) at settling chamber inlets are a cost-efficient structural measure to homogenize the flow and reduce local velocities and turbulence in the chambers. We summarized the state of the art of TRs and conducted detailed flow velocity measurements in the settling chambers of a DF with TRs. In the first campaign, a pronounced flow concentration beneath the vertical bars of the TRs was found, resulting in flow velocities along the invert of up to 3.5 times the average cross-sectional velocity. Because this impairs the trapping efficiency, the TR bars were extended downward to achieve a more even distribution of the flow resistance over the entire flow section. A subsequent measurement campaign confirmed a more homogeneous flow field and a considerable reduction of the turbulence intensities and turbulent kinetic energy, which were the lowest compared to six other DFs. The results highlight the potential to modify existing TRs at other DFs with inhomogeneous flow fields and the practical importance of TR design for new DFs. Practical Applications: In hydropower plants (HPPs) with water intakes located at sediment-laden rivers, DFs are crucial for reducing the sediment load in the turbine water, consequently minimizing wear on the turbines. A DF usually consists of one or several chambers through which the water flows slowly, allowing sand particles to settle. However, for geometrical, hydraulic, and economic reasons, the flow at the chamber inlet is often not favorable for settling. In such situations, TRs can be installed to slow down and distribute the inflow more evenly. Because no general design guidelines for TRs are available, we reviewed the state of the art based on literature and present the field investigation of flow fields in a DF with TRs. We found an unfavorable flow concentration and modified the TRs to cover the whole flow section. This resulted in more favorable conditions for settling, also in comparison with other DFs. In DFs with inhomogeneous inflow conditions, suitably designed TRs enhance the trapping efficiency and contribute hence to the cost- and energy-efficient use of the hydropower potential at sediment-laden rivers. [ABSTRACT FROM AUTHOR]

With the increasing complexity of the industrial production process, the transmission medium of the hydraulic turbine is no longer satisfied, and the gas-liquid two-phase mixed medium has to be considered. The presence of gas in the transmission medium will alters the internal flow structure of the hydraulic turbine and affect its operational stability. Therefore, for the purpose of clarifying the influence of inlet gas content on the internal flow of PAT, the unsteady flow of the PAT is simulated in this paper using numerical simulation. Based on the numerical simulation results, the influence of inlet gas content on the internal flow characteristics, characteristics of pressure fluctuation in impeller and volute, and vortex evolution of flow field are analyzed. The accumulation of gas phase leads to the emergence of vortices, and regions with low pressure values appear at the vortex generation. The major factor of the periodic variation of pressure fluctuation between volute and cut-water is the dynamic and static interference of impeller. The increase of gas content causes more flow disorder in the cut-water region and the volute contraction section. Since the gas in the flow channel is predominantly on the suction side of blades, the flow field on the suction side is more complex than that on the pressure side, and the amplitude of pressure fluctuation increases appropriately. The vortex structure is mainly distributed on balance hole, inlet area of impeller and suction side of blade. As the blade rotates, there are new shedding and growth of vortices, and finally attached to the volute wall. Increasing gas content enhances the influence of blade rotation on the vortex evolution characteristics in the volute and impeller. [ABSTRACT FROM AUTHOR]

To analyze the effect of blade number on the performance of hydraulic turbines during the transient stage in which the flow rate is not constant, six hydraulic turbines with different blade numbers are considered. The instantaneous hydraulic performance of the turbine and the pressure pulsation acting on the impeller are investigated numerically by using the ANSYS CFX software. The ensuing results are compared with the outcomes of experimental tests. It is shown that the fluctuation range of the pressure coefficient increases with time, but the corresponding range for the transient hydraulic efficiency decreases gradually when the flow velocity transits to larger values. During the transition to small flow velocity, the fluctuation range of the pressure coefficient gradually decreases as time passes, but the corresponding fluctuation range of its transient hydraulic efficiency gradually becomes larger. The fluctuation range in the Z9 case is small during the transition. The main frequency of transient hydraulic efficiency pulsation is equal to the blade frequency. At the main frequency, Z7 has the largest amplitude of the hydraulic efficiency pulsation, Z10 has the smallest amplitude, and the difference between Z7 and Z9 is limited. As the number of blades grows, the pressure pulsation during the transition process gradually decreases, but the pressure pulsation of Z10 at the volute tongue is larger. In the steady state, Z9 has the highest efficiency and in the transient stage, the pressure coefficient fluctuation range is small. Accordingly, for the hydraulic turbine Z9, the performance is optimal. [ABSTRACT FROM AUTHOR]

For renovation and modernization of 200 MW steam turbine generator of LMZ design operating beyond their technical life, it is necessary to replace the mechanical governors with electronic governors. As the operating philosophy of modern electronic governors is different, simulation is carried out to check the impact on dynamic performance. In this paper, mathematical modeling approach and simulation results are presented. The study confirms that the controller configuration adopted in electronic governor gives better dynamic response for disturbances normally encountered in the operation. [ABSTRACT FROM AUTHOR]

Sediment erosion poses a significant challenge for hydraulic turbines in sediment-laden rivers. This paper investigates the erosion patterns in high-head Francis turbines using numerical simulations. It analyzes how sediment concentration, particle size, and operating conditions affect wear on turbine components. The results identify the trailing edges of the guide vanes, the intersection of runner blade trailing edge, and runner band as primary erosion zones. Higher sediment concentrations increase erosion intensity and extend the erosion range upstream. Small particles uniformly affect both pressure and suction sides of the blades, while larger particles concentrate erosion near the runner band trailing edges. The flow rate has a greater impact on runner blade erosion than water head, with lower flow rates reducing pressure side erosion but initially increasing, then decreasing suction side erosion. Additionally, the study proposes a multi-objective, multi-condition optimization design method that balances erosion resistance and energy efficiency. The optimized runner reduces the maximum erosion rate by 23.91% while limiting the weighted efficiency loss to under 0.1%. The improved runner design reduces high erosion areas on both blade sides, particularly decreasing particle impact speeds near the trailing edges. Sensitivity analysis reveals a trade-off between minimizing erosion and maintaining hydraulic efficiency, highlighting the importance of span height at 75% for controlling erosion. Changes in blade circumference angle generally reduce erosion but may also lower efficiency. Overall, this research demonstrates a successful reduction in Francis turbine erosion while preserving hydraulic efficiency, offering valuable guidance for anti-erosion turbine design in sediment-heavy environments. [ABSTRACT FROM AUTHOR]

Data‐driven assistant for the design of offshore jacket substructures As the power output of offshore wind turbines increases, more and more influencing factors in the different life phases of the support structure become relevant to improve feasibility, economic viability, and provability. Conventional design methods for offshore wind turbines are complex and expensive. Conventional conceptual designs often rely on the expertise and intuition of engineers, creating a risk of bias due to insufficient design information at the beginning of a project. To minimize this risk, this paper develops a data‐driven method to simplify conceptual support structure design. The method is realized by analyzing a self‐generated global database of existing wind farms. As an example, the data‐driven method is implemented and evaluated for the conceptual design of offshore jacket substructures. It shows that the rated power of the turbine and the water depth of the wind farm should be considered as two structural parameters for the conceptual design of jacket structures for offshore wind turbines. Thus, the process is simplified and made more economical. The result forms the basis for the overall offshore wind turbine's detailed design and structural implementation. [ABSTRACT FROM AUTHOR]

The demand for electricity is increasing tremendously globally with the development of countries. To fulfill the supply of electricity, many countries have already adopted renewable energy sources. The production of electricity from hydraulic energy sources is one of the oldest methods. The axial flow water turbine can efficiently generate energy from the water flow with a very low head. The current investigation is focused on enhancing the performance of the axial turbine by providing an enclosure around the rotor. The initial experiments were carried out with only the upstream enclosure. The optimized upstream enclosure was taken with different lengths of downstream enclosure for further investigations. The current investigation concluded that the maximum efficiency using only an upstream enclosure is 89.48%, which is around 3.20% higher compared with the bare turbine. The optimum efficiency was found at upstream-side length ratio (ULR)=0.46 (upstream enclosure length LU=40 mm). With using the optimum ULR=0.46 , the maximum efficiency for the downstream enclosure was found at downstream-side length ratio (DLR)=0.23 (downstream enclosure length LD=20 mm). The highest efficiency value for this axial runner was obtained at 90.89%, which is 4.83% higher compared with the bare turbine. [ABSTRACT FROM AUTHOR]

Suction bucket jackets have been used as foundations for offshore wind turbines in intermediate water depths where layered soil stratigraphies are often encountered. Although suction installation in layered soils has been studied, experimental data on the in-service response is scarce. During installation in stratigraphies containing a low permeability layer underlain by a high permeability layer, suction is transferred to the underlying layer when the pressure at the lid invert is sufficient to uplift the low permeability plug. This suction-transfer mechanism also affects the in-service response, albeit the load-sharing mechanism is not well understood. This paper presents data from centrifuge tests of suction buckets subjected to constant amplitude and varying amplitude cyclic vertical loading in two stratigraphies—a sand with an overlying clay layer and in a sand with a sandwiched clay layer. These experiments show that tensile stresses exceeding the vented tensile resistance can be withstood without significant uplift of the bucket in both stratigraphies, even under a zero mean stress. Plug uplift was shown to have an important effect on the amount of stress transferred to the skirts, with the load-sharing mechanism depending on the stratigraphy. Additionally, the load-sharing mechanism and the bucket in-service resistance was shown to depend on the effectiveness of the clay in sealing the soil plug within the bucket, with a more effective seal resulting in higher tensile resistance and therefore better performance. A limiting loading condition was not identified in the sand with a sandwiched clay layer, with the data indicating that the suction pressure to cause plug uplift during cyclic loading may be much higher than during suction installation. [ABSTRACT FROM AUTHOR]

The operational efficiency, stability, and lifespan of hydroelectric power plants operating on sediment-laden rivers are affected by sediment erosion. A numerical simulation of the sand–water flow in the water-intake components of a turbine at a specific power station was conducted using the Euler–Lagrange method. Additionally, sediment erosion tests were carried out on the water-intake components coated with epoxy mortar material. The results indicate that sediment erosion on the stay vane surface mainly occurs on the front face, with the most severe erosion at the head, while sediment erosion on the stay ring surface primarily occurs near the stay vane head. The extent of erosion is mainly influenced by the distribution characteristics of sediment particles. The wear of epoxy mortar coating material is minimally affected by the spraying thickness. Adding 30% hardener to the epoxy mortar material can significantly improve the erosion resistance of the stay vane surface by about 30%. The erosion rate on the frontside of the stay vane is approximately 2.6 times that of the backside. Based on the sediment erosion tests and numerical simulation results of the sand–water flow, an estimation formula for the sediment erosion rate of the epoxy mortar erosion-resistant coating was established. This formula can be used to predict the anti-sediment erosion performance of epoxy mortar materials applied to the water-intake components of this turbine and similar river turbines. [ABSTRACT FROM AUTHOR]

The increasing demand to harness offshore wind resources has pushed offshore wind turbines into deeper waters, making floating platforms more economically feasible than bottom-fixed ones. When the incident wind and wave forces act on the floating wind turbine, the floating platform will experience oscillations around its equilibrium position in six degrees of freedom (DOFs). Significant floater motions can affect the aerodynamic power output, increase the failure risk, and even shorten the operational lifetime, especially under a harsh offshore environment. To improve the dynamic behavior of the floating platform, this research designed a heave plate for an OC4-Deepcwind wind turbine. The dynamic performance of the wind turbine was specifically investigated based on a series of wave-basin model tests, including free decay tests, regular wave tests, and irregular wave with steady wind tests. The results show that the heave plate increases damping in heave and pitch motions. The weakening effect on the heave and pitch motion is obvious in the wave period of 15–20 s and 20–27 s, respectively. However, the arrangement of the heave plate may exacerbate the fluctuation of the force and moment at the bottom of the tower. [ABSTRACT FROM AUTHOR]

In the context of energy shortages and the development of new energy sources, tidal current energy has emerged as a promising alternative. It is typically harnessed by deploying arrays of multiple water turbines offshore. Vertical axis water turbines (VAWTs), as key units in these arrays, have wake effects that influence array spacing and energy efficiency. However, existing studies on wake velocity distribution models for VAWTs are limited in number, accuracy, and consideration of influencing factors. A precise theoretical model (Lam's formula) for wake lateral velocity can better predict wake decay, aiding in the optimization of tidal current energy array designs. Turbulence in the ocean, serving as a medium for energy exchange between high-energy and low-energy water flows, significantly impacts the wake recovery of water turbines. To simplify the problem, this study uses software ANSYS Fluent 2020 R2 for two-dimensional simulations of VAWT wake decay under different turbulence intensities, confirming the critical role of turbulence intensity in wake velocity decay. Based on the obtained data, a new mathematical approach was employed to incorporate turbulence intensity into Lam's wake formula for VAWTs, improving its predictive accuracy with a minimum error of 1%, and refining some parameter calculations. The results show that this model effectively reflects the impact of turbulence on VAWT wake recovery and can be used to predict wake decay under various turbulence conditions, providing a theoretical basis for VAWT design, optimization, and array layout. [ABSTRACT FROM AUTHOR]

In order to improve the dynamic performance during the startup process of hydropower units, while considering the efficient and stable speed increase and effective suppression of water pressure fluctuations and mechanical vibrations, optimization algorithms must be used to select the optimal parameters for the system. However, in current research, various multi-objective optimization algorithms still have limitations in terms of target space coverage and diversity maintenance in parameter optimization during the startup process of hydraulic turbines. To explore and verify the optimal algorithms and parameters for the startup process of hydraulic turbines, multiple multi-objective optimization strategies are proposed in this study. Under the condition of constructing a fine-tuned nonlinear model of the control system, this paper focuses on three key indicators: the absolute integral of the speed deviation, the absolute integral of the snail shell water pressure fluctuation, and the relative value of the maximum axial water thrust. Through comparative analysis of the multi-objective particle swarm optimization algorithm (MOPSO), variant multi-objective particle swarm optimization algorithm (VMOPSO), multi-objective sine cosine algorithm (MOSCA), multi-objective biogeography algorithm (MOBBO), multi-objective gravity search algorithm (MOGAS), and improved multi-objective particle swarm optimization algorithm (IMOPSO), the obtained optimal parameters are compared and analyzed to select the optimal multi-objective optimization strategy, and the most suitable parameters for actual working conditions are selected through a comprehensive weighting method. The results show that, compared to the local optimal solution problem caused by other optimization algorithms, the improved multi-objective optimization method significantly reduces water pressure fluctuations and mechanical vibrations while ensuring stable speed improvement, achieving better control performance. The optimization results have significant guiding significance for ensuring the smooth operation and safety of hydropower units, and provide strong support for making operational decisions. [ABSTRACT FROM AUTHOR]

Hydraulic turbine test stands represent an important link in the efficient utilization of the energy potential of water flows. The realization of these turbines begins with an approximate design, based on the differential equations of motion of ideal fluids, and continues with successive stages of performance testing in the laboratory, on small-scale models. Using different similarity criteria based on geometric, kinematic and dynamic similarities, the conclusions drawn from the operation of the model will also be valid for the real machine. The purpose of the paper is to present some points of view on the realization of three types of stands for small hydraulic turbines, of which two are patented and one is a patent application. These stands simulate real operating conditions on permanent flowing water with velocities, flows and falls for small hydraulic turbines that can be installed on the water line, in locations that do not use dams or other expensive water storage facilities. The main author of the patent documentation makes a synthesis of the constructive-functional characteristics of the respective stands through this article. [ABSTRACT FROM AUTHOR]

Investigating the flow performance of Francis turbines from model to prototype is a complex but essential process for ensuring reliable and efficient turbine operation in hydropower plants. It ensures that Francis turbine designs operate efficiently under various operating conditions, extending from laboratory reduced-scale models to full-scale prototype installations. In this investigation, a Francis turbine model was tested under different operating conditions, and its properties were measured, including torque, hydraulic efficiency, power output, cavitation coefficient, rotational speed, flow rate, and pressure pulsations. The results of the Francis turbine model test indicate that it achieved the maximum torque with the designed discharge and designed head. The cavitation coefficient consistently remained higher than the critical cavitation coefficient. The initial cavitation bubbles were observed at 50% partial load but disappeared at full load. Pressure pulsations under different operating conditions showed the maximum peak-to-peak amplitude appearing at the turbine inlet domain and the minimum amplitude occurring at the draft tube elbow. A hill chart shows that the model's best efficiency was 93.66%, and the estimated best efficiency of the prototype was 95.03% at the design head. The conclusions and methodology of this study can be generalized to other similar hydraulic turbines, especially prototype Francis turbines that lack experimental results. [ABSTRACT FROM AUTHOR]

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A typical wind system captures wind energy and converts it into electricity, which is then converted to DC for battery storage using an AC/DC converter; an inverter then supplies AC electricity at the grid frequency. However, this solution involves losses in electronic components and incurs costs and environmental impacts associated with battery storage. To address these issues, a different wind system layout configuration is considered, where the energy storage duties are assumed by a hydro storage system employing a reversible hydraulic pump (referred to as a Pump as Turbine). This solution utilises an elevated reservoir connected to the Pump as Turbine to compensate for fluctuations in wind and load; this approach offers lower costs, a longer lifespan, reduced maintenance, and a smaller waste management cost. This study focuses on a comprehensive sensitivity analysis of the new wind system power layout, considering multiple objectives. Specifically, the analysis targets the net change in the mass of water (potential energy) stored in the pumped hydro system, the captured wind energy, and the torque provided in hydraulic turbine mode. On the other hand, the design variables are represented by the Pump as Turbine-specific speed, the hydraulic system gearbox ratio, and the pump head. To assess how solutions are affected by random changes in wind speed and external load, the sensitivity analysis considers the multi-objective optimisation problem showing for both the wind speed and the external load a stochastic contribution. [ABSTRACT FROM AUTHOR]

Sediment erosion of hydraulic turbines is a significant challenge in hydropower plants in mountainous regions like the European Alps, the Andes, and the Himalayan region. The erosive wear of Pelton runner buckets is influenced by a variety of factors, including the size, hardness, and concentration of silt particles; the velocity of the flow and impingement angle of the jet; the properties of the base material; and the operating hours of the turbine. This research aims to identify the locations most susceptible to erosion and to elucidate the mechanisms of erosion propagation in two distinct designs of Pelton runner buckets. The Pelton runner buckets were subjected to static condition tests with particle sizes of 500 microns and a concentration of 14,000 mg/L. The buckets were coated with four layers of paint, sequentially applied in red, yellow, green, and blue. The two Pelton buckets, D 1 and D 2 , were evaluated for their erosion resistance properties. D 2 demonstrated superior erosion resistance, attributed to its geometrical features and material composition, lower erosion rates, less material loss, and improved surface integrity compared with D1. This difference is primarily attributed to factors such as the splitter's thickness, the jet's impact angle, the velocity at which particles strike, and the concentration of sand. D 2 exhibits a great performance in terms of erosion resistance among the two designs. This study reveals that the angle of jet impingement influences erosion progression and material loss, which is important to consider during a Pelton turbine's design and operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, analyses of Francis turbine failures for powerful Pumped Hydraulic Energy Storage (PHES) are conducted. The structure is part of PHES Chaira, Bulgaria (HA4—Hydro-Aggregate 4). The aim of the study is to assess the structure-to-concrete embedding to determine the possible causes of damage and destruction of the HA4 Francis spiral casing units. The embedding methods that have been applied in practice for decades are discussed and compared to those used for HA4. A virtual prototype is built based on the finite-element method to clarify the influence of workloads under the generator mode. The stages of the simulation include structural analysis of the spiral casing and concrete under load in generator mode, as well as structural analysis of the spiral casing under loads in generator mode without concrete. Both simulations are of major importance. Since the failure of the surface between the turbine, the spiral casing, and the concrete is observed, the effect of the growing contact gap (no contact) is analyzed. The stresses, strains, and displacements of the turbine units are simulated, followed by an analysis for reliability. The conclusions reveal the possible reasons for cracks and destruction in the main elements of the structure. [ABSTRACT FROM AUTHOR]

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]

Three forms of the mooring system in 60 m water depth are proposed for semi-submersible with partially inclined columns (SPIC) concept floating wind turbine (FWT). One is a simple form with only catenary lines, and the other two are hybrid forms including clump weights. The clumps are attached to the suspended section for Hybrid form1 and the bottom section for Hybrid form2. Hybrid form2 achieves the smallest line length and chain weight. Three alternative proposals can be evaluated through mooring line characteristics, dynamic responses, utilization factors, and simple cost analysis. Hybrid form2 allows for smallest pretension, and largest stiffness and nonlinearity only at large offsets. Under operational conditions, the mean surge for Hybrid form1 and Hybrid form2 is similar, but the fairlead tension is significantly smaller for Hybrid form2. Under the survival condition, the clumps of Hybrid form2 are lifted up and put down, leading to small mean offsets of FWT but large wave-frequency components of line tension. Among the three forms of the mooring system, the Hybrid form2 can limit the FWT to the smallest offset range while also controlling the mean mooring line tension to a level similar to the other two forms. Under normal working conditions and accidental conditions with single line broken, the maximal surge motions of FWT under the restraint of three mooring systems all meet the design requirements. The mooring line strength of the three mooring systems meets the requirements in ultimate limit state (ULS) and accidental limit state (ALS) analyses. Among them, the utilization coefficient of Hybrid form2 is closest to 1, demonstrating its best economic performance. [ABSTRACT FROM AUTHOR]

In this study, a vertical-axis helical-blade water turbine is innovatively proposed by drawing on the design scheme of the traditional straight-blade turbine, compared to which this blade form can effectively improve the self-starting capability and energy capture efficiency of the turbine. The study analyzes the hydrodynamic performance of the device under different parameters using CFD (computational fluid dynamics) software STAR-CCM+ and overlapping mesh technique, and the CFD simulation results are verified with published experimental work. First, the design concept of the hydraulic turbine is presented, focusing on the design of the blades and transmission mechanism to ensure the stability of the structure. Second, the effect of two-dimensional parameters on the flow field characteristics and efficiency is investigated, and then three-dimensional design parameters, such as blade helix angle and hub-to-tip ratio, are considered. The results show that a 20% increase in blade density results in a 10.74% increase in efficiency. Regarding flow velocity, a maximum output of 2.4 kW was achieved for four operating conditions (1.0, 1.5, 2.0, and 2.5 m/s). In addition, the average dynamic torque of the helical-blade turbine was 16.44% higher than that of the straight-blade turbine, indicating superior self-starting capability. It was also found that at an aspect ratio of 1.5–1.75 and a helix angle of 80°, the energy capture efficiency of the helical-blade turbine was 33.7%, which was 45.3% higher than that of the straight-blade turbine. Comparative analysis shows that the vertical-axis helical-blade turbine has favorable hydrodynamic performance, especially under low flow conditions, and the design scheme shows obvious advantages, which makes up for the defects of the traditional vertical-axis straight-blade turbine with poor self-starting ability and low efficiency, and fills up the research gaps of vertical-axis turbine design optimization, which is of certain research value. [ABSTRACT FROM AUTHOR]

The governor parameters affect the stability and regulation quality of hydropower system with two turbine units sharing a super long headrace tunnel (SLHT). To improve the transient process of hydropower system, this study investigates the optimization of governor parameters. First, the model of hydropower system with two turbine units sharing an SLHT is established. Second, the optimization scheme of governor parameters for transient process of hydropower system is designed by genetic algorithm. The mathematical formulation of genetic algorithm is illuminated. The implementation procedure of genetic algorithm is illustrated. Then, the optimization results of governor parameters by genetic algorithm are analyzed by illustrating the regulation quality of hydropower system under two operating conditions. Finally, the effect of asymmetrical factors on optimal governor parameters is revealed. The asymmetrical layout of bifurcated penstocks, asymmetrical layout of turbine units, and asymmetrical load disturbances are considered. The results indicate that the objective function of hydropower system is composed of the dynamic indexes for frequency oscillations of two turbine units and water level oscillation in surge tank. The fitness function evolves in the direction that makes the regulation quality of hydropower system become better. Under the symmetrical or asymmetrical bifurcated penstocks, turbine units, and load disturbances, the optimal parameters of governors are asymmetrical. The regulation quality of hydropower system under the governor parameters of genetic algorithm is obviously better than that under the governor parameters of Stein formula. The optimal governor parameters are directly affected by the asymmetrical factors of hydropower system. With the increase of the flow inertia of one bifurcated penstock, the optimal parameters of the other governor become greater. [ABSTRACT FROM AUTHOR]

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]

The development of hydroelectric technology and much of the "knowledge" on hydraulic phenomena derive from scale modeling and "bench" tests to improve machinery efficiency. The result of these experimental tests is mapping the so-called "hill chart", representing the "DNA" of a turbine model. Identifying the efficiency values as a function of the specific parameters of the flow and energy coefficient (which both identify the operating point) allows us to represent the complete behavior of a turbine in hydraulic similarity with the original model developed in the laboratory. The present work carries out a "reverse engineering" operation that leads to the definition of "an innovative research model" that is relatively simple to use in every field. Thus, from the experimental survey of the degree of efficiency of several prototypes of machines deriving from the same starting model, the hill chart of the hydraulic profile used is reconstructed. The "mapping" of all the characteristic quantities of the machine, together with the physical parameters of the regulating organs of a four-blade Kaplan turbine model, also made it possible to complete the process, allowing to identify not only the iso-efficiency regions but also the curves relating to the trend of the angle of the impeller blades, the specific opening of the distributor, and the identification of critical areas of cavitation. The development of the hill chart was made possible by investigating the behavior of 33 actual prototypes and 46 characteristic curves derived from the same reference model based on practical experiments for finding the optimal blade distributor "setup curve". To complete this, theoretical characteristic curves of "not physically realized" prototypes were also mapped, allowing us to complete the regions comprising the diagram. The study of the unified hill charts found in previous documentation of the most famous manufacturers was of great help. Finally, the validation of the "proposed procedure" was obtained through the experimental survey of the actual efficiency of the new prototype based on the theoretical values defined in the design phase on the chart obtained with the method described. [ABSTRACT FROM AUTHOR]

Hydraulic turbines have become indispensable for harnessing renewable energy sources, particularly in-pipe hydraulic turbine technology, which leverages excess energy within pipeline systems like drinking water distribution pipes to produce electrical power. Among these turbines, the propeller-type axial turbine with circular blades stands out for its efficiency. However, there is a notable lack of literature on fluid dynamics and structural behavior under various operational conditions. This study introduces a comprehensive methodology to numerically investigate the hydraulic and structural responses of turbines designed for in-pipe installation. The methodology encompasses the design of circular blades, followed by parametric studies on fluid dynamics and structural analysis. The circular blade's performance was evaluated across different materials, incorporating static, modal, and harmonic response analyses. Results showed that the circular blade achieved a peak hydraulic efficiency of 75.5% at a flow rate of 10 l/s, generating 1.86 m of head pressure drop and 138 W of mechanical power. Structurally, it demonstrated a safety factor exceeding 1 across the entire hydraulic range without encountering resonance or fatigue issues. This research and its methodology significantly contribute to advancing the understanding of designing and assessing the fluid dynamic behavior and structural integrity of circular blades in axial propeller-type turbines for in-pipe installations, serving as a valuable resource for future studies in similar domains. [ABSTRACT FROM AUTHOR]

This work compared the suitability of the k- ϵ standard, k- ϵ RNG, k- ω SST, and k- ω standard turbulence models for simulating a gravitational water vortex hydraulic turbine using ANSYS Fluent. This study revealed significant discrepancies between the models, particularly in predicting vortex circulation. While the k- ϵ RNG and standard k- ω models maintained relatively constant circulation values, the k- ϵ standard model exhibited higher values, and the k- ω SST model showed irregular fluctuations. The mass flow rate stabilization also varied, with the k- ϵ RNG, k- ω SST, and k- ω standard models being stabilized around 2.1 kg/s, whereas the k- ϵ standard model fluctuated between 1.9 and 2.1 kg/s. Statistical analyses, including ANOVA and multiple comparison methods, confirmed the significant impact of the turbulence model choice on both the circulation and mass flow rate. Experimental validation further supported the numerical findings by demonstrating that the k- ω shear stress transport (SST) model most closely matched the real vortex profile, followed by the k- ϵ RNG model. The primary contribution of this work is the comprehensive evaluation of these turbulence models, which provide clear guidance on their applicability to gravitational water vortex hydraulic turbine simulations. [ABSTRACT FROM AUTHOR]

The study aims to address the need for cleaner and more efficient combustion technologies in the context of global energy demand and sustainability goals. It focuses on microflame techniques to enhance the performance of gas turbines and water heating boilers. This research investigated, for the first time, the operation of a micromodular burner for hot water boilers and a microflame burner for gas turbines, based on patented inventions. Methods for assessing efficiency included analyzing heat flows, fuel conversion rates to thermal energy, and emission analysis. Using high-precision measuring equipment, such as TESTO 350-XL, thermocouples, flow meters, and others, optimal operating modes were determined for the gas turbine combustion chamber and hot water boiler. This resulted in achieving high efficiency and reducing harmful emission levels (NOx < 15 ppm, CO < 140 ppm). Theoretical calculations were compared with experimental data, confirming the reliability of the results obtained. [ABSTRACT FROM AUTHOR]

The paper presents the analysis of the gantry crane loading when travelling along the crane track, using a 3D model, which was used for the analysis of the gantry crane support construction under the loading. The gantry crane is designed to remove dirt that is in front of the turbine under the water surface. The gantry crane, which travels along a track, was subjected to investigation, and the directional and vertical unevenness at the time of travelling were determined and are given in graphic form in [mm] for A track and B track with a total track length of 450 m. Based on the knowledge of the unevenness of the rail track, four random functional dependencies, defining the unevenness of the individual rails, were used as input variables for the kinematic excitation of the individual wheels of the gantry crane. The stress analysis was performed for a travel speed of 30 m/min and a lift of 10 t. The results of the stress analysis are presented in graphic form. In addition to the operating load, the inherent frequencies of the crane construction are also an important factor, which, along with the excitation frequency, can affect the overall global loss of the crane stability. The stability of the crane during its operation is closely related to the load applied to the crane supporting construction. In computer simulations, stability is expressed by a critical force (Fcrit.) and when it is exceeded, local or global stability will be lost. In the paper, the first 10 eigenfrequencies of the crane are given in table form, and the first three eigenshapes are shown in graphic form. The overall loss of crane stability, which is expressed by the critical force (Fcrit.), is also shown in graphic form. [ABSTRACT FROM AUTHOR]

In this study, in order to promote the development of far-reaching marine aquaculture equipment in an intelligent direction and solve the problems related to power supply, a tidal current energy harvesting device for a low-velocity sea area is proposed. For low-velocity waters in farming areas, the device can effectively harness tidal energy to provide a stable power supply to open sea cages. A mathematical model of the Savonius turbine blade is established, and the influence of the distance between the impeller center and the water surface on the energy capture efficiency of the turbine is analyzed through numerical simulation. Using ANSYS2021R1 software, the velocity field of the floating body is simulated, and the overall structure and anchoring system of the power generation device is designed. In order to verify the effectiveness of the power generation device, a test model is built and a physical model test is carried out. The variation in parameters related to the relative distance between the impeller and the water under different flow velocities is tested, and the test data are analyzed. The test results show that the floating body can increase the flow speed by 10%. Optimizing the blade number and order of the S-turbine can capture more than 20% of the energy. Under different flow velocities, the capture power of the impeller first increases and then decreases with increasing distance from the water. When the center of the impeller is one-quarter of the impeller diameter higher than the water surface, the output power of the impeller is at the maximum. This indicates that the proposed power generation device can effectively use tidal energy under different water depth conditions and provide a stable power supply for far-reaching marine aquaculture equipment. [ABSTRACT FROM AUTHOR]

This study focuses on the problem of perturbation suppression and tracking control of nonlinear fractional order systems with time‐varying delay. To simplify the control process for such systems, the Takagi–Sugeno fuzzy model is used to describe the nonlinear fractional order delayed systems. Additionally, a modified repetitive controller is applied to develop an output feedback technique for the proposed systems. To ensure system stability, the study establishes new delay‐dependent stabilization conditions using a novel Lyapunov–Krasovskii functional (LKF). These stability conditions are expressed in formation of linear matrix inequalities (LMIs) by adopting a frequency‐distributed model transformation and some slack matrices. The proposed method demonstrates that the system output can track the desired input with ignorable error, while effectively rejecting disturbances. Finally, the efficacy of the proposed method is evaluated through simulations of the modified Chua circuit and the hydraulic turbine governing system (HTGS). [ABSTRACT FROM AUTHOR]