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The potential wind speed in Indonesia is generally low at 3 m/s to 7 m/s, so this type of vertical axis turbine is considered very suitable for use in wind conditions in Indonesia. There are several types of vertical-axis wind turbines. One type of vertical axis wind turbine is the Savonius wind turbine. This type of wind turbine has many advantages, such as receiving wind from all directions, being easy and cheap to manufacture, and rotating at a relatively low angular speed. This test was carried out to determine the performance of conventional and modified Savonius turbines with 2 and 3 blades variables in each turbine blade shape. The modification is made by changing the shape of the blade twisting by 45o. The turbine is carried out on a laboratory scale with a wind source using a fan directly opposite the turbine. The results showed that the highest turbine power occurred in a modified 2-blade turbine, namely 1.88 Watt with a torque value of 0.04 Nm and a shaft rotation of 450 rpm. 2 modified blades also obtain the highest rotation value at a wind speed of 6 m/s producing 896 rpm. However, the highest torque value is obtained by a conventional 2-blade turbine with a value of 0.136 Nm. A modified two-blade turbine receives the highest efficiency in each turbine, with an efficiency value of 36.92%. In comparison, the highest turbine efficiency for a modified 3-blade turbine reaches 11.69%, considered less efficient than other turbines. [ABSTRACT FROM AUTHOR]

Hydrokinetic turbines are an emerging type of hydroenergy converters used for small rivers and streams usually in run-of-the-river installations. Run-of-the-river installations are micro-hydropower plants built without significantly altering the natural flow of the river (no dams, no reservoir). They represents one of the most environment friendly hydropower plants available today. In order for these turbines to be deemed a cost effective solution, extensive research is required. To this end, a mathematical model of the hydrokinetic turbine is required. The aim of this paper is to determine a model of a hydrokinetic turbine using polynomial regression. A model is necessary for simulating the energy conversion system which is, in turn, necessary for designing the control of the system, the protection, etc. The power coefficient on which the model is based describes the efficiency of the turbine in extracting power from the water. It is highly dependent on the characteristics of the turbine: its type, shape, dimensions, material, etc. However, the power coefficient is seldom provided by literature. Therefore, being able to obtain an estimative relationship based on experimental data is a necessity. Since hydrokinetic turbines have a very different, less controllable installation compared cu conventional hydropower plants (zero head with no reservoir), they are modelled in a completelydifferent fashion. [ABSTRACT FROM AUTHOR]

Compared with a conventional turbine, counter rotating turbine has larger thrust weight ratio, shorter axial distance, and higher efficiency. It has been widely used in high-performance aviation. In conventional counter-rotating turbine, HPT is located in the front of LPT, and only a stator row can be eliminated. The layout limits the turbine weight and efficiency. Therefore, the staggered counter rotating turbine is proposed, and the staggered counter rotating turbine can eliminate the all-internal stators, which can greatly improve the turbine weight and efficiency. The staggered counter rotating turbine is the development and improvement of counter rotating turbine. Due to the elimination of the all-internal stators, the downstream rotor will suffer from the insufficient inlet swirl, which is the main question in staggered counter rotating turbine design. Furthermore, the turbine outlet angle is also an important parameter to evaluate the turbine design. The coordination of inlet swirl and outlet Mach number and the outlet angle is discussed by the theoretical method. In order to verify the design method, two-dimensional throughflow design, blade design, and three-dimensional numerical analysis are performed. Expansion ratios and efficiency at the speed combinations of the 80% to 105% are discussed to reveal the turbine characteristics at off-design conditions. An adiabatic total-to-total efficiency of 92.1% with expansion ratio of 4.47 at design point is obtained and achieves the initial design goal very well. The paper is aimed at providing a technical approach to improve the thrust weight ratio, efficiency of high bypass turbofan engines, and provide new ideas for the development of aeroengines. [ABSTRACT FROM AUTHOR]

Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the construction of a decentralized power system. Savonius wind turbines are operated by drag force, with the blades moving in the same direction as the flow current providing the thrust force and those moving in the opposite direction of the wind being rotated by the drag force. In this study, the Savonius wind turbine design was examined to develop a stable wind turbine for use in urban centers at low wind speeds. The Savonius rotor design variables (aspect and overlap ratios) and blade forms (semi-circular, Bach, and elliptical type) were examined using computational fluid dynamics analysis. Moreover, a rotor capable of providing the target output was designed and maximum rotor efficiency of 18% was realized. Further, changes to the flow corresponding with various turbine layouts were analyzed to determine the arrangement that would maximize turbine performance. The results showed that the maximum efficiency of the turbines was in the 17–19% range and without significant variation. [ABSTRACT FROM AUTHOR]

The primary objective of this investigation was to explore the aerodynamic impact of adding trailing edge serrations to a Wells turbine. The baseline turbine consists of eight NACA 0015 blades. The blade chord length was 0.125 m and the span was 0.100 m. Two modified serrated blade configurations were studied: (1) full-span, and (2) partial-span covering 0.288c of the trailing edge. The numerical simulations were carried out by solving the three-dimensional, incompressible steady-state Reynolds Averaged Navier-Stokes (RANS) equations using the k-ω SST turbulence model in ANSYS™ (CFX). The aerodynamic performance of the modified Wells turbine was compared to the baseline by calculating non-dimensional parameters (i.e., torque coefficient, pressure drop coefficient, and turbine efficiency). A comparison of the streamlines was performed to analyze the flow topology around the turbine blades for a flow coefficient range of 0.075 ≤ ϕ ≤ 0.275, representing an angle of attack range of 4.29° ≤ α ≤ 15.3°. The trailing edge serrations generated a substantial change in surface pressure and effectively reduced the separated flow region, thus improving efficiency in most cases. As a result, there was a modest peak efficiency increase of 1.51% and 1.22%, for the partial- and full-span trailing edge serrations, respectively. [ABSTRACT FROM AUTHOR]

In Ecuador, the implementation of hydroelectric power plants has had a remarkable growth in the energy sector due to its high efficiency, low environmental impact, and opportunities to generate employment. One of the sectors with the greatest benefits from this type of energy has been the rural sector, where several small-scale hydroelectric plants (0.5 MW–10 MW) have been installed, usually with Pelton turbines. Although these turbines are highly efficient, one of the challenges is to obtain the optimal geometry of the bucket to take advantage of the greatest amount of energy from the water, avoiding the separation of the fluid. In this context, this study focuses on the development of an analytical and iterative methodology that allows for the determining of the appropriate dimensions of the buckets to achieve maximum turbine efficiency. For that, a parametric model has been proposed considering the dimensions and main angles of the bucket, the net hydraulic head and the working flow, as well as the power losses. The results of the model have been validated by means of CFD and by contrasting the experimental data obtained from the "Illuchi N2" Hydroelectric Power Plant in Ecuador, and it is concluded that it is possible to improve the turbine efficiency by up to 4%. [ABSTRACT FROM AUTHOR]

In this study, using a Geographical Information System (GIS) based model method, locations having theoretical hydroelectric energy potential were identified in the Buyuk Menderes basin, one of Turkey's largest basins. According to the installed power potential on the examined basin, 33 sites below 10 MW, 57 sites between 10 and 50 MW, 4 sites between 50 and 100 MW, and 1 site over 100 MW were found as a consequence of the study. While the theoretical hydroelectric energy potential in the whole basin is 886.55 MW at 70% turbine efficiency, the installed power in the basin is currently 302.02 MW. According to these results, only 34.07% of the total hydro potential in the basin is used today. [ABSTRACT FROM AUTHOR]

To improve the efficiency of a Savonius vertical axis wind turbine, this investigation proposes the use of expandable blades instead of rigid blades. The expandable blades have the ability to change their form during the turbine rotation. The expansion of the advancing blade increases the positive torque, and the contraction of the returning blade decreases the negative torque, which boosts the turbine efficiency. Two-dimensional numerical simulations have been carried out using the commercial code ansys fluent 18.0 with a deformable mesh to fit the changing shape of the blades during the rotation cycle. The paper involves the effect of the expansion amplitude as well as the effect of the blades gap and overlap ratios on the turbine overall performance. The numerical model is validated by comparison of predictions with experimental results. Results show that the torque coefficient is improved by about 24% for the lowest expansion amplitude and by about 90.6% for the highest expansion amplitude. A further improvement of 7% is recorded for an expandable turbine with a gap ratio of 1/20 the turbine diameter. [ABSTRACT FROM AUTHOR]

Hydropower operation optimization in river systems involves market prices, technological constraints affecting the efficiency of turbines, and flow constraints set by an environmental regulator. Comprehensive environmental flow regulation includes the ecological state of a river system and the impact on hydropower value. This article studies the impacts of environmental constraints on hydropower value under varying electricity price volatility scenarios. The effects of maximum flow, minimum flow, and flow ramping constraints are studied analytically and quantitatively. We frame the lost hydropower value as the economic cost of these constraints. We show that the economic costs of the environmental constraints decrease with lower price volatility. We use a marginal cost and marginal benefit framework to illustrate that the optimal flow constraint should be tightened if the price volatility decreases in the electricity market. Our approach illustrates how electricity price volatility influences the analysis of optimal environmental constraints in regulated river systems. Finally, we analyse the effect of different environmental flow release options in fishways on the economic cost of a fishway. If the hydropower operator can optimize the fishway flow allocation, then the loss in hydropower value is lower than under a constant fishway flow. [ABSTRACT FROM AUTHOR]

A wind turbine's tip speed ratio (TSR) is the linear speed of the blade's tip, normalized by the incoming wind speed. For a given blade profile, there is a TSR that maximizes the turbine's efficiency. The industry's current practice is to impose the same TSR that maximizes the efficiency of a single, isolated wind turbine on every turbine of a wind farm. This article proves that this strategy is wrong. The article demonstrates that in every wind direction, there is always a subset of turbines that needs to operate at non-efficient conditions to provide more energy to some of their downstream counterparts to boost the farm's overall production. The aerodynamic interactions between the turbines cause this. The authors employed the well-known Jensen wake model in concert with Particle Swarm Optimization to demonstrate the effectiveness of this strategy at Lillgrund, a wind farm in Sweden. The model's formulation and implementation were validated using large-eddy simulation results. The AEP of Lillgrund increased by approximately 4% by optimizing and actively controlling the TSR. This strategy also decreased the farm's overall TSR, defined as the average TSR of the turbines, by 8%, leading to several structural and environmental benefits. Note that both these values are farm-dependent and change from one farm to another; hence, this research serves as a proof of concept. [ABSTRACT FROM AUTHOR]

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This paper is dedicated to the description of all our research done so far in the field of simulation of small hydropower plants as well as in creating a functional laboratory model based on the proposed simulation models. Comparing to the common structures, we propose some different approaches in modelling parts of the small hydropower plants, e.g. fuzzy model of the hydraulic turbine efficiency. Moreover, this simulation model is created directly for the small hydropower plants, thus it simplifies parts, that are commonly used in other scientific papers and simulate the phenomenon connected to the big scale hydropower plants structure and physical description. As a necessary step in the process of creation of universal laboratory model of a small hydropower plant that should be used for design and tuning purposes of new approaches of controlling such systems, we discuss the research and development phase that led to the final construction of the depicted laboratory model. [ABSTRACT FROM AUTHOR]

To reduce carbon dioxide emissions into the environment, the energy sector develops oxygen-fuel energy cycles. One of the most promising cycles is the Allam cycle that features the highest efficiency of electricity generation among all others. One of the main elements of an oxy-fuel energy cycle is a high-temperature carbon dioxide turbine. The turbine's working fluid and coolant consist predominantly of carbon dioxide at a supercritical pressure. Currently, there are no recommendations in the literature for the design of carbon dioxide turbines for an oxy-fuel energy system (OFES) operating according to the Allam cycle; therefore, there is a need to study the influence of parameters of the flow path of carbon dioxide turbines on its efficiency and overall performance. In this paper, we have presented the results of one-dimensional calculations of a flow path of the carbon dioxide turbine for the Allam cycle with a capacity of 300 MW, with an initial temperature and pressure of 1100 °C and 30 MPa, and an outlet pressure of 3 MPa. The study was carried out by varying the rotor speed, the reactivity level and the average diameter. Based on the results of one-dimensional calculations, we have found that the highest efficiency of the turbine flow path is achieved at a speed of 471 rad/s, a reactivity of 0.5, and an average diameter of 1.1 m for the first stage. [ABSTRACT FROM AUTHOR]

The radial-outflow turbine has advantages due to its liquid-rich gas adaptability when applied in the Kalina ammonia-water cycle system. However, the operational conditions of the turbine often deviate from its design values due to changes of the heat source or the cooling conditions, and such deviates may deteriorate the flow behavior and degrade the turbine performance. To enhance the turbine efficiency at complex conditions for flexible running of the Kalina cycle system, a multipoint design optimization method is developed: the flexible operating has been defined by three critical, dimensionless parameters, which cover a wide range in a 3D operating space; the representative off-design points are identified to define the objective function; and adaptive optimization methods are integrated to permit optimization searching using limited CFD callings. The developed multipoint design method is adopted to improve the turbine performance under complex operating conditions. The obtained results demonstrate that the application of the developed multipoint optimization method effectively eliminates the flow separation at various operating conditions; thus, the turbine off-design performance has been comprehensively improved. [ABSTRACT FROM AUTHOR]

Premature rain erosion damage development at the leading edges of wind turbine rotor blades impair the efficiency of the turbines and should be detected as early as possible. To investigate the causes of premature erosion damage and the erosion evolution, test specimens similar to the leading edge of a rotor blade were modified with different initial defects, such as voids in the coating system, and impacted with waterdrops in a rain erosion test facility. Using CT and XRM with AI-based evaluation as non-destructive measurement methods showed that premature erosion arises from the initial material defects because they represent a weak point in the material composite. In addition, thermographic investigations were carried out. As it shows results similar to the two lab-based methods, active thermography has a promising potential for future in-situ monitoring of rotor blade leading edges. [ABSTRACT FROM AUTHOR]

The battery of an electric vehicle (EV) must be appropriately cooled to prevent battery overheating while driving. Waste heat from EV batteries is typically recovered and used for indoor heating instead of generating electricity. In this study, an organic Rankine cycle (ORC) using electric vehicle (EV) battery heat as a heat source was designed with a particular focus on the turbine. The mean-line design of a single-stage axial-flow turbine was performed, and the turbine performance was analyzed. The isentropic efficiency of the designed turbine was 0.75, and the electrical power was approximately 100 W. The thermal efficiency of the ORC was 4.23 % at a working fluid temperature of 25 °C at the condenser outlet. This used 2.24 kW of battery heat, which is approximately 78 % of the EV battery waste heat considered in this study. Therefore, applying the ORC to an EV recovers a significant amount of waste heat from the battery to reduce the battery temperature and generate electricity. Furthermore, we present an operation method that can improve the thermal efficiency of the EV ORC and is applicable in situations where the evaporation and condensation are not constant. [ABSTRACT FROM AUTHOR]

The operating point of a propeller hydropower station will deviate from the effective workspace while the discharge reduces excessively during dry seasons. It usually leads to a decrease in efficiency and even to being unable to work. To solve the above problem, a scheme named decreasing capacity to increase efficiency was presented in this article. A low-specific-speed propeller runner with fixed blades that has the same installing dimensions as the original one was redesigned and equipped in dry seasons. A positive circulation at the outlet of the blades bigger than in conventional runners is allowed. Some key technologies about hydraulic design for runner blades were researched, which include distribution of velocity circulation at the inlet and outlet of the runner, thickening of the epiphyseal line of an aerofoil, unfolding aerofoil being converted to a cylindrical section, etc. In the section on digital modeling for runner blades, aerofoils on the cylindrical sections at the rim and at the hub were constructed employing the trend extrapolation method. Moreover, a blade digital model was built at one time according to the aerofoils on all cylindrical sections by means of a successful redevelopment to UniGraphics, and it has perfect symmetry. A case presented indicates that the method of decreasing capacity to increase efficiency is feasible. Using the method, the turbine efficiency increased from less than 28.6% to 83.4% while the discharge decreased from 3.20 m3s−1 to 1.00 m3s−1, and then the hydropower unit was able to work properly. [ABSTRACT FROM AUTHOR]

On the basis of the established irreversible simple closed gas turbine cycle model, this paper optimizes cycle performance further by applying the theory of finite-time thermodynamics. Dimensionless efficient power expression of the cycle is derived. Effects of internal irreversibility (turbine and compressor efficiencies) and heat reservoir temperature ratio on dimensionless efficient power are analyzed. When total heat conductance of two heat exchangers is constant, the double maximum dimensionless efficient power of a cycle can be obtained by optimizing heat-conductance distribution and cycle pressure-ratio. Through the NSGA-II algorithm, multi-objective optimizations are performed on the irreversible closed gas turbine cycle by taking five performance indicators, dimensionless power density, dimensionless ecological function, thermal efficiency, dimensionless efficient power and dimensionless power output, as objective functions, and taking pressure ratio and heat conductance distribution as optimization variables. The Pareto frontiers with the optimal solution set are obtained. The results reflect that heat reservoir temperature ratio and compressor efficiency have greatest influences on dimensionless efficient power, and the deviation indexes obtained by TOPSIS, LINMAP and Shannon Entropy decision-making methods are 0.2921, 0.2921, 0.2284, respectively, for five-objective optimization. The deviation index obtained by Shannon Entropy decision-making method is smaller than other decision-making methods and its result is more ideal. [ABSTRACT FROM AUTHOR]

The classic Savonius semi-circular blade turbine has a relatively low power coefficient. The performance of a Savonius wind turbine depends on its geometrical parameters. Various blade profiles have been developed in the past years to improve the performance of this class of turbine. In this paper, a new blade shapes of Savonius wind turbine is investigated numerically by using the CFD method, by using transient conditions and set k omega turbulence model. The new blade has different concave and convex shape, which is a combination of the conventional and the elliptical blade. A comparative study of three blade profiles, semi-circular, elliptical and the composed blades have been performed. Flow structures around the rotor have also been analyzed. The results show that changing the blade shape has an effect on the performance efficiency of the Savonius turbine. The new modified and the elliptical blade exhibit higher performance compared to the conventional Savonius wind turbine. The new modified Savonius blade and the elliptical blade exhibit an improved performance compared to the conventional model in the order of 20.5% and 18.2% respectively at the tip speed ratio of 0.8. [ABSTRACT FROM AUTHOR]

Based on the digital twin technology, this article investigates the physical rules fusion model of the turbine rotor operation in thermal power plants, establishes the geometric behavior mapping method of the turbine rotor in the virtual scenario of thermal power plants, and develops a real-time data-driven virtual monitoring system of the rotor operation, which realizes the virtual control of the rotor operation process from the physical and geometric levels, respectively. The 3D model created by Creo was imported into ADAMS in x_t format, constraints were added, and model data input and output interfaces were established in ADAMS software to build its dynamics model. The foundation of the joint simulation with the AMESim model is laid. The information fusion technology based on D-S evidence theory, fusing multisensor data and information from other channels, can more accurately and comprehensively understand and describe the diagnostic object, to make correct judgment and decisions on complex fault diagnosis. We propose an integrated modeling method for multiview control scenarios of manufacturing units based on digital twins and finalize the construction of digital twin models of manufacturing units based on the definition of the multiview model collaboration mechanism, which provides model support for the research of digital twin-driven manufacturing unit control technology. For the twin data perception and interaction problem, a unified architecture-standardized communication protocol is established based on OPC UA technology to solve the problem of difficult data perception and interaction caused by the nonuniform communication interface protocol of different devices on the automated production line. The model change is intended to help improve the visualization level of digital production line monitoring and improve the operating efficiency of the turbine rotor. The experimental results show that the application of digital twin to thermal turbine rotor operation monitoring provides a new method for turbine rotor vibration fault diagnosis; D-S evidence theory can fuse information from multiple aspects of the fault, thus improving the probability of fault diagnosis and reducing uncertainty. [ABSTRACT FROM AUTHOR]

An integrated method combining one-dimensional design and automatic three-dimensional optimization is proposed for SCO2 radial inflow turbines with low specific speed. The optimization of the nozzle and impeller are performed simultaneously. Four optimization algorithms, namely, grey wolf optimizer, elephant herding optimization, genetic algorithm, and simulated annealing algorithm, are integrated with computational fluid dynamics simulation and finite element analysis to improve the turbine efficiency. Two constraints (mass flow variation and maximum stress) are imposed in the optimization process. The results indicate that the grey wolf optimizer is the optimal algorithm. The total-to-static efficiency of the optimal turbine is 89.56 %, which is increased by 3.25 %. Moreover, splitter blades are also investigated and optimized. The maximum total-to-static efficiency of 90.16 % can be obtained by reasonably arranging splitter blades. The proposed method is versatile, nimble, and easy to implement. It can improve the design efficiency and provide a geometric reference for low specific speed SCO2 turbines. [ABSTRACT FROM AUTHOR]

The propulsion demands of high-speed naval vessels often rely on gas turbines, producing significant amount of power achieving thus high performance requirements. Gas turbines can be used either to provide purely mechanical propulsion, or alternatively to generate electricity, which is subsequently used by electric drives to propel the ship. However, the thermal efficiencies of gas turbines are lower than those of Diesel engines of similar power. In the context of improving the performance of existing marine gas turbines, it is proposed to enhance engine's performance by integrating a pressure wave supercharger (or wave rotor), while keeping the basic components of the baseline engine unchanged. This article is an application of a method developed by the author for marine gas turbines with and without recuperator, [Fatsis 2019]. It is found that important benefits are obtained for the topped engines in comparison to the self-standing baseline engines. The wave rotor integration is more appropriate for engines with low compression ratios and high turbine inlet temperatures. Application of wave rotor technology to recuperated marine gas turbines shows efficiency gain exceeding 19% for all the compression ratio and turbine inlet temperatures examined. Abbreviations: COGAS, Combined gas turbine and steam turbine; COGES, Combined gas turbine electric and steam; GTE, Gas turbine engines [ABSTRACT FROM AUTHOR]

Vertical-axis wind turbines (VAWT) are excellent candidates to complement traditional wind turbines and increase the total wind energy capacity. Development of VAWT has been hampered by their low efficiency and structural unreliability, which are related to the occurrence of dynamic stall. Dynamic stall consists of the formation, growth, and shedding of large-scale vortices, followed by massive flow separation. The vortex shedding is detrimental to the turbine's efficiency and causes significant load fluctuations that jeopardise the turbine's structural integrity. We present a comprehensive experimental characterisation of dynamic stall on a VAWT blade including time-resolved load and velocity field measurements. Particular attention is dedicated to the dilemma faced by VAWT to either operate at lower tip-speed ratios to maximise their peak aerodynamic performance but experience dynamic stall, or to avoid dynamic stall at the cost of reducing their peak performance. Based on the results, we map turbine operating conditions to one of three regimes: deep stall, light stall, and no stall. The light stall regime offers VAWT the best compromise in the dynamic stall dilemma as it yields positive tangential forces during the upwind and downwind rotation and reduces load transients by 75% compared to the deep stall regime. [ABSTRACT FROM AUTHOR]

Steam turbines play a critical role in power generation systems. Therefore, increasing the efficiency of steam turbines is highly desirable, especially in LP stages. One of the suggested techniques to reduce wetness losses in LP stages is the hot steam injection. In the first section of the present study, the effect of 3D turbine blade span length on wet steam flow parameters is investigated. Then, the performance of various arrangements of hot steam injection holes (single slot, in-line no. 1, in-line no. 2, staggered no. 1, and staggered no. 2) is evaluated and compared. The results demonstrated that the in-line no. 1 arrangement is the best design for hot steam injection. In this arrangement, the wetness and condensation loss are reduced by 79% and 44%, respectively, and the kinetic energy loss is less than the other arrangements. However, the kinetic energy is still about 28% lower than in the no-injection case. Ultimately, excessive kinetic energy reduction due to hot steam injection is prevented by decreasing the injection pressure. As the injection pressure is reduced from 160 to 100 kPa, the kinetic energy, wetness, and condensation loss are reduced by 9%, 40%, and 17%, respectively, compared to the no-injection case. [ABSTRACT FROM AUTHOR]

The Indian River, which is celebrated for its breathtaking beauty and diverse heritage of cultures, has an extensive amount of potential for producing green hydroelectric electricity. 7.5 % of the world's energy came from renewable sources in 2022, with India making up 36 % of the share and growing. India has nearly reached the 5 GW objective for small hydro projects and has reached 68 % of its 175 GW renewable energy ambition. At 90 % efficiency, bulb turbines are hydroelectric turbines that produce power from water, making them a perfect choice for high flow rates and low water head conditions. In order to optimize bulb turbines, this research investigates the use of computational fluid dynamics (CFD) to assess variables including the number of guiding vanes, the angle of the draft tube, and the design of the blades. According to studies, efficiency is increased when guiding vanes increase. The geometry of guiding vanes also has a significant impact on performance. Draft tubes, which restore kinetic energy from water entering the turbine, can enhance efficiency with proper design. Adding anti-cavitation capabilities to runner blades improves performance even further. CFD models verify these conclusions, with little variations from the field data. By fine-tuning important parameters such as 14 guiding vanes and adjusting the draft tube angle to 2.5°, the turbine's efficiency jumped from 87 % to 97 %. [ABSTRACT FROM AUTHOR]

• Thermodynamic cycle with isothermal expansion. • Isothermal nozzles: theory and design. • Simulation and experimental studies on nozzles with isothermal expansion. • Innovative gas isothermal turbine: design, simulation calculations and experimental studies. The efficiency of power plants with steam or gas turbines depends on the efficiencies of a thermodynamic cycle and devices implementing this cycle. In the case of high power outputs, we cannot expect a significant increase in the efficiency of individual devices. Therefore, what remains is to increase the efficiency of the implemented thermodynamic cycle − the complex Rankine cycle in the case of steam turbines or the extended Brayton cycle in gas turbine units. The efficiencies of these cycles depend on the hot reservoir temperatures, limited by the materials used. The solution seems to be the thermodynamic cycles with the highest efficiency within given temperature limits, the „generalized Carnot cycles". About gas turbines, such a cycle is the Ericsson cycle. The most difficult element of this cycle is carrying out high-temperature expansion. So far, there is no literature data on a technical device implementing this process. In this article, we present a method for designing turbine nozzles for isothermal expansion and the results of experimental tests of the first isothermal turbine. In the case of gas microturbines with a regenerator, isothermal expansion can increase efficiency from 24% to 28% up to 36%. An increase in efficiency of several to a dozen percentage points is expected for Organic Rankine Cycle (ORC) turbines. Due to such significant increases in energy generation efficiency, an isothermal turbine may become a future solution for energy systems. [ABSTRACT FROM AUTHOR]

• Fourteen parameters, which represented all the aerofoil's vane shape of a micro-scale turbine, i.e., 2–12 kW, were accurately studied. • Their influence on both the vane performance, stage operation, and the overall cycle's performance is determined. • The Linear Point Advanced Side 2 showed almost no influence on the turbine performance. • The Trailing Edge Wedge Angle and Trailing Edge Beta Angle were the most influential parameters. • This results in enhancing the stator and the turbine efficiency by around 11% and 5%, respectively, compared to the baseline design. The ever-elevating importance of turbines makes enhancing their performance a crucial point. In most cases, the required performance can be achieved by improving the turbine's components, i.e., its rotary part, stationary part, and volute. However, this requires a lot of effort, especially when dealing with rotary parts that are time-consuming and costly because of the rotor. Having said that, most of the previous studies have improved turbomachinery by using the latter method. The current study, on the other hand, highlights the importance of only one component, the cheaper one, as a key factor. So, once the numerical modelling was validated using a previous experimental published work, fourteen parameters, which represented all the aerofoil's vane shape (the stationary part of the turbine only) of a micro-scale turbine i.e. 2–12 kW, were accurately studied with the aim of highlighting their influence on both the vane performance, stage operation, and the overall cycle's performance as well. The results showed that while parameter 14 i.e. Linear Point Advanced Side 2 showed almost no influence and parameters 5 and 6 i.e. Trailing Edge Wedge Angle and Trailing Edge Beta Angle were the most influential ones, all the other parameters showed a significant effect on the overall turbines' performance, especially at higher PR values. Moreover, the results have also confirmed that the best values of the mentioned parameters are 0.33 mm, 17 Deg., −25 Deg., 41 Deg., 1 Deg., 55 Deg., 0.3 mm, 0 Deg., 19 mm, 31 mm, 77 mm and 0 mm for all thirteen parameters, respectively. This results in enhancing the stator and the turbine efficiency by around 11 % and 5 % respectively, compared to the baseline design. [ABSTRACT FROM AUTHOR]

In light of the extended exposure of tidal stream energy generation systems to seawater, which can lead to marine biofouling and subsequent reductions in turbine efficiency, this paper presents a deep learning-based method for the identification of pollutant adhesion. This method aims to rapidly assess the status of turbine pollutant adhesion in tidal energy generation systems. A dataset of adhesion images from tidal stream energy generation system under varying levels of pollution was obtained through underwater experiments with artificial fouling. Three different deep learning algorithms were employed to investigate the enhancement of underwater biofouling image quality. Image segmentation algorithms were used to extract and identify information related to the location and area of biofouling. The results demonstrate that the proposed deep learning-based pollutant adhesion identification method effectively recognizes the adhesion status on turbine blades, improving the accuracy of pollutant identification. This approach provides an efficient and accurate means of pollutant adhesion detection and management for the operation and maintenance of tidal stream energy generation systems, ultimately reducing operational costs. • A deep learning-based method for pollutant adhesion recognition is proposed. • The prototypes of the turbine component for the tidal energy generator device are designed, manufactured and tested under water. • Underwater images of the biofouling status of underwater tidal energy turbine devices are collected. • The recognition method can effectively improve the accuracy of identification of pollutant adhesion. [ABSTRACT FROM AUTHOR]

The thermodynamic analysis of a geothermal-based integrated energy system to produce liquid hydrogen, cooling, hot water, and power was presented in this study. The investigated system consists geothermal subsystems, a modified organic Rankine cycle (ORC), a PEM electrolyzer, and a liquid hydrogen storage source. Different organic fluids including refrigerants R113, R123, and R134a were investigated to increase the system performance. Analysis of organic fluids showed that the best organic fluid is R123 because it helps to increase the performance of the system. The authors employed the Design-Expert software and RSM for optimum results purposes, and the objective functions were chosen to be exergy efficiency (EE) and cost rate (CR). Following introduction of design variables, the mass flow rate of input to the evaporator, the temperature of input to heat recovery vapor generator, turbine efficiency, turbine input temperature, evaporator pinch point temperature, and pump efficiency, their impact on the system's performance were investigated. The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h, respectively. Also, in this research, seven regions within Canada were investigated for the launch of the proposed system. The studied cities were Victoria, Vancouver, Regina, St. John's, Dawson Creek, Whitehorse, and Port Alberni. Finally, Regina was chosen because of the system's superior performance in electricity production at a reasonable cost in that area. The environmental results showed that the presented energy system in Regina city could help to expand 5 ha of green space by producing electricity at the rate of 4993.03 MWh in one year. The findings indicated that implementing the suggested system in Regina would help prevent 1018.6 tons of CO 2 /MWh from being emitted into the environment yearly, only by chipping in 24445.9 $/ton of CO 2 per year. • Thermodynamic analysis of a multiple energy production system. • Geothermal energy for commissioning in Canada. • Optimization by response surface method (RSM). • The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h. [ABSTRACT FROM AUTHOR]

Hydraulic short circuit (HSC), corresponding to the simultaneous operation of the pumps and turbines, enhances the power flexibility of a pumped storage power plant (PSPP). However, comprehensive analyses are imperative to guarantee a secure and reliable operation within this novel operational mode. Unforeseen engaging dynamics may perturb the safe operation of the groups. The existing literature still lacks comprehensive analysis concerning the water flow structures and tubomachines performances during HSC operations across the entire hydraulic circuit. This paper evaluates the fluid-dynamic interactions between the units during HSC operations using 3D unsteady-state CFD simulations of an existing PSPP not designed for enduring such conditions. The total pressure evolution in the upstream trifurcation and consequent effects on the turbine performance are discussed by the selected HSC configurations. In the trifurcation, between the pumping unit and the turbine, the relative head loss reaches 1,78% and, eventually, anomalies of the velocity field are documented on a case-by-case basis. Moreover, the pump operations are investigated in HSC operations with the matter of efficiency detriments, cavitation and air entrainment risk. The results highlight that the pumping unit in HSC compared to the baseline operation undergoes a reduction in hydraulic efficiency up to 0.51% due to the operation of adjacent turbine. The documented observations led to the application of additional criteria for the safe and stable governing control of the PSPP in HSC. • CFD research assesses HSC impacts on penstock trifurcation and turbomachine performance. • In HSC, flow perturbations from trifurcations can reduce turbine efficiency by 0.55%. • Pumps in HSC may lose hydraulic efficiency due to nearby turbine operations. • Pump cavitation and air entrainment risk are investigated during HSC service. • Preferable configurations of pump and turbines for HSC operations are identified. [ABSTRACT FROM AUTHOR]

• High specific speed Francis turbine as an alternative to low specific speed Kaplan/semi-Kaplan/Propeller turbine. • Comprehensive experimental studies of the high specific speed Francis turbine. • Multi-aspect experimental approach to determining the Thoma cavitation number. • Comprehensive vortex visualization for various cavitation states in the draft tube. • Saddles were found on the performance characteristics for high guide vane opening angles. The paper presents comprehensive experimental research on a high specific speed model Francis turbine with a characteristic runner diameter of 250 mm under the head of 12 m. Essentially, the turbine was designed for use at heads between 10 and 50 m, which are typical for installations with low specific speed Kaplan turbines. The basic performance, cavitation and runaway characteristics of the machine, which were determined as a result of the work, are quite rarely available in the literature in the case of high specific speed Francis turbines. The turbine achieved the maximum efficiency of 91%, kinematic specific speed of 82, and relatively wide operation range, so that it can be attractive as an alternative to the low specific speed Kaplan, semi-Kaplan or propeller turbines. In result of the basic laboratory tests, the performance characteristics of the machine operation in a wide range of guide vane opening angles between 9° and 36° as well as the shell efficiency characteristics were determined. On the characteristics plotted vs. rotational speed, the saddle effect was identified for the guide vane opening angles with values greater than the optimal one (22°). During the operation of the machine in the area of saddles, the change in the flow rate took quite surprising patterns. The share of the turbine thrust torque in the total torque was also determined, the characteristics of which are also burdened with a similar saddle effect. In the case of cavitation tests, a multi-aspect approach to cavitation diagnostics was used to characterize the cavitation phenomenon from the viewpoint of various criteria. Following this approach, the signals of the draft tube wall acceleration, acoustic emission at the draft tube cone upper flange, and pressure fluctuations inside the draft tube were used. The determined cavitation characteristics indicate little cavitation susceptibility of the Francis turbine blade system, despite the presented turbine having been designed to operate at higher flow rates than the classic high head Francis turbines with long interblade channels. The cavitating flow in the draft tube, directly below the runner, was also visualized during the cavitation tests. The paper presents the results of visualization for all cavitation states at five selected settings of the guide vane opening angle (two states in Partial Load, two states in High Load area and one state in the Best Efficiency Point), thanks to which it was possible to track the development of vortices during pressure reduction in the flow system. The runaway coefficient was determined as a result of the runaway tests. The value of 1.497 was reached at the optimum guide vane opening angle. Additionally, the work also presents in detail the efficiency scale effects to be expected at prototype turbines, i.e. those intended for operation at a higher head and with larger runner diameters. The efficiency of the machine with a runner diameter of 1.5 m and working at a head of 50 m reaches ∼93%. The influence of water viscosity on the change in efficiency of the prototype turbine is also shown. The presented methodology can be used for the proper selection of turbines intended for hydropower plants and for the proper installation of the runner in respect to the tailwater level in order to avoid the phenomenon of cavitation erosion. [ABSTRACT FROM AUTHOR]

An enormous amount of the world's electricity is produced by steam power plants. The existence of a liquid phase in the steam turbine results in an efficiency drop and mechanical losses, which are very expensive due to its high price. Creating a suction slot in the stationary blade of the steam turbine for sucking the supercooled vapor and wetness fraction in the low-pressure stages of the turbine is one of the most effective methods of preserving the rotor blades against corrosion and erosion. The Eulerian-Eulerian method is employed for modeling the condensing flow. In the current research, the impact of the suction slot location and number on the surfaces of the turbine blades is investigated on condensation, total suction ratio, liquid suction ratio, average droplet radius, and condensation losses. Optimization is performed by the TOPSIS algorithm. Based on the results, the location and number of the suction slots affect the flow pattern in the turbine blade. Creating a suction slot in the optimal case has a total suction ratio of 4.1 %, which decreases the liquid suction ratio, condensation losses, and average droplet radius, respectively, by 5.28 %, 6 %, and 25 % compared to the original case. • Supercooled vapor suction in steam turbine is studied to control wetness parameters. • Effect of slot on steam turbine is investigated for supercooled vapor suction. • Optimization by TOPSIS is employed to find the optimal slot location and number. • Suction slot from the suction side has a greater influence than the pressure side. • Optimal mode is caused reduction in the droplet radius and condensation losses. [ABSTRACT FROM AUTHOR]

The pre-swirl system, a vital system responsible for supplying cooling gas to the turbine blades. However, the pre-swirl system involves rotor-stator matching and intricate power-heat conversion challenges, which has led to a bottleneck in the development of its temperature drop potential. This study investigates the traditional pre-swirl system structure to identify factors limiting its temperature drop performance. A novel design idea is proposed to enhance the temperature drop performance by reducing the power consumption in the pre-swirl system. Subsequently, the structure optimization and performance improvement for pre-swirl system are conducted through the design of four vane-shaped receiver hole models. To assess the effectiveness of these enhancements, the thermodynamic and aerodynamic characteristics of the pre-swirl system before and after optimizations are evaluated using numerical simulations. Finally, the system temperature drop characteristics equipped with optimal receiver holes are thoroughly evaluated by experimental test analysis. The findings reveal that the new type of pre-swirl system, featuring a leading-edge vane-shaped receiver hole design and the removal of the cover-plate cavity, surpasses traditional designs. It exhibits a remarkable 35.3 % improvement in the receiver hole discharge coefficient, a 39.7 % reduction in system entropy increase, and a 6.36 kW/(kg/s) decrease in specific power consumption. Significantly, experimental verification demonstrates a 10 % increase in the nozzle pressure ratio, the temperature drop of pre-swirl system increased by 53.6 % from 23.5K to 36.1K, and the temperature drop efficiency of pre-swirl system increased from 0.567 to 0.872. Therefore, this study offers valuable insights for the design of high-performance pre-swirl systems, contributing to the overall improvement of turbine efficiency. [Display omitted] • The leading-edge vane-shaped receiver holes can improve pre-swirl system performance. • New pre-swirl system has temperature drop significantly improved by 53.6 %. • New pre-swirl system has entropy increase reduced by 39.7 %. • New pre-swirl system has specific power consumption reduced by 6.36 kW/(kg/s). • New pre-swirl system has the temperature drop efficiency is 0.872. [ABSTRACT FROM AUTHOR]

This study aims to optimize a multi-energy production system that utilizes sustainable geothermal energy as its primary power source. The system comprises several subsystems, including a geothermal well, an organic rankine cycle (ORC) unit, an absorption chiller, and a proton exchange membrane (PEM) electrolyzer. The study examined the impact of variations in seven key parameters, including turbine inlet temperature, evaporator pinch point temperature, pump inlet temperature, evaporator inlet temperature, evaporator inlet mass flow rate, turbine efficiency, and pump efficiency, on the overall system performance. The Response Surface Methodology (RSM) was employed to find the optimum point of the system. To facilitate the practical implementation of the system, the research team assessed its viability in 10 different Iranian cities, all known for their substantial geothermal energy potential. Among the cities, Zahedan emerged as the most suitable location for deploying the system, given its robust energy production potential. The results showed that January, with a production of 626.4 MW h of electricity, and November, with a production of 622.8 MWh of electricity, are the best months for the system to operate in Zahedan city. The environmental aspect of the system also yielded noteworthy results. By setting up the proposed system in Zahedan city, it is possible to prevent the emission of 1472.411 tons of carbon dioxide by producing 7217.7 MWh of electricity throughout the year at a cost of 35337.86 $. Additionally, the proposed system can help expand 7 ha of green space, providing the electricity needed by 2349 people throughout the year. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of very low head (VLH) axial turbines in rivers and canals is one of the new methods of utilizing hydropower on a small scale. These types of turbines are environmentally friendly and, due to the lack of need for a dam, penstock, spiral casing, and draft tube, have low construction costs. Higher efficiency and improved turbine performance also lead to lower overall costs. In this study, the primary objective is to pinpoint the key factors that affect the VLH turbine performance and optimize it accordingly. The design variables encompass various elements, including leading and trailing edge angles, maximum thickness across three blade sections, tip clearance, outlet angles of guide vanes, and the count of guide vanes and runner blades. In this regard, during the optimization phase, only the most influential factors as ascertained through sensitivity analysis are considered. Subsequently, employing surrogate modeling, an evolutionary optimization algorithm is applied to identify the optimal configuration of design variables. Critical design variables were identified, including the blade angles in the middle section, the trailing edge angles, the outlet angle of the guide vanes, and the number of runner blades. Following the optimization process, the optimal turbine exhibited notable improvements, with a 2.26 % increase in efficiency and a remarkable 10.4 % boost in power output compared to the original configuration. Moreover, the optimized turbine showcased improved performance beyond the design point, with approximately a 2 % efficiency increase across all discharge rates. [ABSTRACT FROM AUTHOR]

Pumped storage represents an economically viable, highly efficient, and extensive energy storage solution, receiving substantial research attention worldwide. This study utilized the energy dissipation of fish swimming in the water, and the traveling wave plate was arranged in a vertical rectangular flow channel to obtain energy through reverse thinking. Numerical simulation was employed to investigate the performance characteristics of the traveling wave turbine under varying wave number across high and low water head. The results reveal that the efficiency at low water head starts to increase and then decreases with the increase of wave number. There is an optimal wave number N = 4 to maximize turbine efficiency, and the maximum efficiency under low water head condition is 89.35 %. The efficiency of the high head condition shows a continuous upward trend, with a maximum value of 92.27 % in the range of wave number studied. With the increase of wave number, the instantaneous mass flow coefficient and power coefficient become more stable. The advantage of increasing the wave number is that more traveling wave plates can participate in energy capture, which is conducive to reducing the force required by each traveling wave plate and making the pressure distribution in each working cavity more regular. [ABSTRACT FROM AUTHOR]

• Numerical analysis optimizes hydrokinetic turbine design and performance parameters. • The study explores five novel turbine geometries with varying blade configurations. • The flow field around the blade profiles was studied at different angular positions. • Two-blade turbine configuration achieves maximum torque and power coefficient. Hydrokinetic turbines harness the kinetic energy of flowing water to generate sustainable power, offering a promising avenue for clean and renewable energy. An effective turbine design is necessary for optimizing power extraction even in scenarios with minimal head. Among the various hydrokinetic turbine designs, the Savonius hydrokinetic turbine holds prominence. Over the past century, numerous studies have aimed to refine the design of the Savonius rotor, yet there remains no consensus on the ideal configuration for these turbines. Addressing this, the current study introduces a novel approach with detailed 3D transient simulations to enhance the water turbine performance via blade modifications, transitioning from traditional analyses that primarily focus on wind turbines. This research develops and analyzes five unique turbine geometries, each varying in blade number, diameter, and angular positions. A detailed numerical analysis was conducted using the sliding mesh technique to assess their impact on turbine efficiency and output, using an inlet water velocity of 0.5 m/s and a tip speed ratio ranging from 0.7 to 1.3. Findings indicate that a two-blade turbine configuration achieves the highest torque coefficient of 0.295, which is 2.41 times higher than that of a four-bladed design with equal blade diameter at a tip speed ratio of 0.7. It also reaches a maximum power coefficient of 0.217, marking a 155 % increase over four-bladed designs with equal blade diameter at a tip speed ratio of 0.9. [ABSTRACT FROM AUTHOR]

The lead-cooled fast reactor (LFR) engenders novel requisites for the energy conversion system when applied to maritime ships and distributed energy supply systems. The supercritical carbon dioxide (sCO 2) Brayton cycle, with the advantages of high efficiency, space-saving, simplicity, and flexibility, is a promising candidate for LFR. Here, we present the first study on the off-design operation of the sCO 2 cycle for LFR, with the turbine and compressor arranged on a single shaft (coaxial-shaft) or two shafts (split-shaft). The off-design performances of the system are investigated using four rotational speed (RS) control-based hybrid control strategies. We showed that the split-shaft system controlled by separate turbine speed and compressor speed has a wider operating space of power load than the coaxial-shaft system. Among the four investigated control strategies, the RS-inventory hybrid control can achieve the best thermal efficiency during load variation by operating at the turbine speed and mass flow rate corresponding to the optimal turbine isentropic efficiency. The maximum operating space of power load (0%–100 %) can be achieved by the RS-turbine inlet pressure hybrid control and the RS-bypass hybrid control. Our study can provide guidance for the flexible and safe part-load operation for small-scale modular Gen-IV nuclear reactors. • Off-design performance of sCO 2 cycle for LFR is evaluated. • Arrangements of turbomachines in coaxial- and split-shaft are compared. • Four hybrid control strategies based on the rotational speed control are studied. • Operating space of thermal efficiency and power load are analyzed. [ABSTRACT FROM AUTHOR]

• A novel inverted cross-flow turbine and its design method for the low and ultra-low head hydraulic condition were proposed. • The four-step parametric studies were conducted to achieve the optimized turbine design. • The turbine achieved higher than 60 % efficiency range in the ultra-low head condition (under 3 m water head) by using a simple spiral nozzle and without a guide vane. • The optimized turbine maximum efficiency was achieved 72.92 % efficiency at the turbine speed 170 RPM with 8.01 m of water head. This study aimed to address the challenges of micro-hydropower generation in low-head environments to expand the proportion of hydropower in renewable energy and achieve a carbon neutrality policy. To achieve these goals, various factors affecting the micro-hydro systems, including geographical constraints, construction costs, and grid connectivity, were reviewed and assessed. The results concluded that a novel type of cross-flow turbine with inverted structures, improved the economic feasibility, productivity, and installability of micro-hydropower plants by reducing head losses in open channels or small streams. The parametric studies consisted of four steps: first, designing the initial inverted cross-flow turbine based on the traditional design rules; for the second and third steps, a parametric study for comparing the runner diameter ratio and the number of blades is conducted; and in the last step optimized turbine was designed. The best efficiency point of the optimized inverted cross-flow turbine was 72.92 % at a runner rotational speed of 170 RPM with a 0.75 runner diameter ratio and 35 blades. The optimized turbine was improved by 7.8 % in power and 7.35 % in efficiency, higher than the initial turbine. From the hill chart comparison between the initial and optimized turbine, operation range expansion was confirmed. Overall, this research demonstrates the potential of the inverted cross-flow turbine under low-head conditions. [ABSTRACT FROM AUTHOR]

Compressible flow turbines usually work under choked conditions, requiring an analysis for the performance estimation. The Mean-line modeling is a fast and accurate method extensively used for the analysis and design purposes. However, it has not already been well-investigated for axial flow turbines specially in choked conditions. The present study investigates the issue from three novel aspects. First, a detailed study is accomplished on the inconsistencies of Mean-line method respect to the physics of real flows. It is discussed that the conditions related to maximum mass flow rate through a nozzle and the Mach number one at the throat are different. In fact, the latter condition is not quite physical. Second, a complete algorithm is utilized to implement the aforementioned considerations for the analysis of turbines. This algorithm includes an innovative Blade Solution Algorithm (BSA) and Turbine Solution Algorithm (TSA). The BSA solves the blade rows of turbine using the basic laws of Physics and real-gas properties. In the TSA, a robust and efficient procedure is presented so the solution of turbine converges in wide ranges of boundary conditions with minimum iterations. The results demonstrate that the algorithm generate close maps to the previous studies. Eventually in the third part, since a fast and robust Mean-line algorithm is crucial in optimization, the code is utilized for a design based on optimization using the Genetic Algorithm. In this procedure, all geometrical parameters are optimized as decision parameters rather than the use of old and approximate correlations. This is done along with novel constraints, which not only maximizes efficiency, but also puts the output power, mass flow rate and turbine size in appropriate ranges. The optimization results in a 3.5% rise in efficiency. • Two efficient and real-time approaches are proposed for Mean-line analysis of axial-flow turbines. • All the procedures are based on the real-gas models. • The performance of turbines can be estimated under a wide range of working conditions, including choked conditions. • Optimization is accomplished on an experimental turbine using the Genetic Algorithm, resulting in an almost 3.5% rise in efficiency. • The impact of various parameters on the turbine efficiency are discussed. [ABSTRACT FROM AUTHOR]

• An improved GANormaly model for fast and accurate diagnosis of blade attachment in marine current turbines is proposed. • The method is based on unsupervised learning, eliminating the need for human tagging and improving the efficiency of human capital use. • Deblurring recovery of underwater images to improve the efficiency of turbine blade attachment cleaning. • Enables fast and accurate diagnosis of blade adhesion on marine current turbines, promoting clean energy production and the development of marine current power generation technology. Marine current energy is a clean and renewable resource that is an available energy source with future power generation potential. However, complex subsea conditions can cause blade failures in marine current turbines (MCTs); therefore, the fault diagnosis of MCTs is essential to ensure their good operation. Image-based diagnosis is a nondestructive approach. To improve the efficiency of using human capital, this study uses the unsupervised learning network GANomaly trained only with normal samples to diagnose the leaf attachment of MCTs. Marine biofouling is a lengthy process, and according to the literature, the blades were contaminated by a 1.1-mm-thick layer of lithium lubricating grease, therefore, this study uses ropes to simulate this attachment. First, we address the problem of blurred underwater images collected using a multiscale retinex enhancement algorithm with color recovery to form a new dataset. GANomaly is modified to diagnose MCT blades with different attachment degrees. The experimental results show that the accuracy of the enhanced dataset is improved by 1.75 %, and the accuracy of the improved GANomaly model reaches 91.23 %, thereby enhancing the efficiency of the fault diagnosis of MCTs. [ABSTRACT FROM AUTHOR]

For decades, hydropower has been the most important renewable energy source in the world. The use of Banki-Michell turbine (B-M) in small hydropower constitutes an attractive solution for rural electrification in developing countries and off-grid applications. This robust turbine is easy to design and to construct and not expensive. A test bench (JLA 29) for remote applications was installed at the Aero-Thermo-Mechanics Department of the Brussels Polytechnic School of ULB to test this type of turbine. This paper aimed to present the efficiency results of the installed Banki-Michell turbine test bench for remote applications and these results helped to design a typical turbine adapted for remote sites such as the Ryamukona site located in Burundi. Two series of B-M turbine tests were carried out, by varying the flow rate using the turbine control valve opening placed inside the distributor and also by controlling the turbine speed using a Sinamics S 120 drive. The efficiency of the turbine varies between 40 and 60% for a flow range varying between 15 and 20% of the nominal flow. According to the tests made with a discharge above 20%, the efficiency of the turbine can reach easily 75 %. Based on this turbine efficiency, a typical B-M turbine of an electric power of 79.5 kWe turbine was designed for Ryamukona site which is a remote site located in Burundi.

One of the most promising technologies for sea-wave energy conversion is the one based on the OWC principle. In a system of this type, the oscillatory motion of the sea waves is converted into a bi-directional air flow which is commonly exploited by means of a self-rectifying turbine such as the Wells turbine, the simplest and most reliable device for this purpose. The vast majority of experiments on Wells turbines and OWC devices has analyzed their performance from a global point of view, often in experimental facilities where the turbine was operated under stationary flow conditions. This paper presents the results of the experimental investigation carried out on a Wells turbine, by measuring the flow field both upstream and downstream of the rotor, in a laboratory set-up capable to reproduce the bi-directional airflow typical of an OWC system. The investigation aims to evaluate the local performance of the Wells turbine under unsteady flow conditions. The experimental measurements allow the identification of the loss components that affect the performance of the turbine. Viscous losses, due to the aerodynamic of the rotor cascade, represent the main contribution to the total losses, and appear larger than kinetic energy losses at the machine exhaust. • Measurements of the local performance of a Wells turbine under bi-directional flow. • Loss components and turbine efficiency are calculated. • Most of losses are due to the aerodynamic behavior of the rotor. • Non-stationary operating conditions strongly affect the performance of the turbine. • Rotor solidity at the hub and tip leakage are main responsible of turbine losses. [ABSTRACT FROM AUTHOR]

Summary: For grid‐scale intermittent electricity storage, liquid air energy storage (LAES) is considered to be one of the most promising technologies for storing renewable energy. In this study, a steady‐state process model was developed for an LAES, by combining a Linde liquefaction process and an open Rankine power cycle. To investigate the system performance and achieve global optimization, a single‐factor analysis approach and multifactor genetic algorithm (GA) optimization model were built using MATLAB software. The effects of the charging pressure, storage pressure, discharging pressure, and isentropic efficiency of the compressor/turbine on the LAES performance parameters, such as the inlet temperature of the Joule–Thomson valve, round‐trip efficiency (RTE), liquefaction ratio (LR), and power consumptions in the compressor, cryo‐pump, and turbine, were investigated. Subsequently, the optimal conditions were obtained using the GA optimization method to achieve the optimal performance of the LAES. The results showed that the charging pressure, discharging pressure, and isentropic efficiencies of the compressor and turbine had significant effects on the RTE; an increase in the discharging pressure resulted in an improved expansion power output; the GA optimization could achieve RTE, LR, the system energy storage and recovery exergy efficiencies of 53.33%, 86.96%, 81.00%, and 78.16%; the power consumption in the compressor of GA optimization was 10.02% maximum saving. The proposed optimization method can be used to further explore the global optimization of cryogenic energy storage systems, such as different‐layout LAES systems and different cryogenic liquefaction media energy storage systems. [ABSTRACT FROM AUTHOR]

Purpose: Steam turbine final assembly is a dynamic process, in which various interference events occur frequently. Currently, data transmission relies on oral presentation, while scheduling depends on the manual experience of managers. This mode has low information transmission efficiency and is difficult to timely respond to emergencies. Besides, it is difficult to consider various factors when manually adjusting the plan, which reduces assembly efficiency. The purpose of this paper is to propose a knowledge-based real-time scheduling system under cyber-physical system (CPS) environment which can improve the assembly efficiency of steam turbines. Design/methodology/approach: First, an Internet of Things based CPS framework is proposed to achieve real-time monitoring of turbine assembly and improve the efficiency of information transmission. Second, a knowledge-based real-time scheduling system consisting of three modules is designed to replace manual experience for steam turbine assembly scheduling. Findings: Experiments show that the scheduling results of the knowledge-based scheduling system outperform heuristic algorithms based on priority rules. Compared with manual scheduling, the delay time is reduced by 43.9%. Originality/value: A knowledge-based real-time scheduling system under CPS environment is proposed to improve the assembly efficiency of steam turbines. This paper provides a reference paradigm for the application of the knowledge-based system and CPS in the assembly control of labor-intensive engineering-to-order products. [ABSTRACT FROM AUTHOR]

Endwall contour optimization design utilized to improve the aerodynamic performance has impact on the flow field near rim seal, and it consequently affects the sealing performance. Combined with Kriging agent model, NSGA-II genetic algorithm and CFD which solves the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations coupled with a fully developed shear stress transport turbulent model, this paper constructs an optimization design system for turbine non-axisymmetric endwall contour design in order to improve aerodynamic efficiency and sealing effectiveness simultaneously. The numerical method for predicting the flow in wheel-space and sealing performance of turbine rim seal is validated on the basis of published experimental data. The base flat endwall design, and two optimal endwall contour designs are selected to investigate the aerodynamic and sealing performance. The results show that the aerodynamic and sealing performance can be improved at the same time. Compared with the base flat endwall design, the total-to-total efficiency is increased by 0.23% and the sealing effectiveness is increased by 11.49% for optimal design 1 at optimal design point. Optimal design 1 can significantly reduce the aerodynamic loss and for different sealing flow rates, the total-to-total efficiency is greater than that of base flat endwall design. Compared with the base flat endwall design, the total-to-total efficiency is increased by 0.15% and the sealing effectiveness is increased by 15.43% for optimal design 2 at optimal design point. The influence of endwall contour on sealing effectiveness is obvious when the cooling flow rate is small. The work of this paper provides a reference for the design of non-axisymmetric endwall with comprehensive optimization of turbine aerodynamic and rim sealing performance. [ABSTRACT FROM AUTHOR]

The horizontal-axis ocean current turbine under investigation is a three-blade rotor that uses the flow of water to rotate its blade. The mechanical energy of a turbine is converted into electrical energy using a generator. The horizontal-axis ocean current turbine provides a nongrid robust and sustainable power source. In this study, the blade design is optimized to achieve higher efficiency, as the blade design of the hydrokinetic turbine has a considerable effect on its output efficiency. All the simulations of this turbine are performed on ANSYS software, based on the Reynolds Averaged Navier–Stokes (RANS) equations. Three-dimensional (CFD) simulations are then performed to evaluate the performance of the rotor at a steady state. To examine the turbine's efficiency, the inner diameter of the rotor is varied in all three cases. The attained result concludes that the highest Cm value is about 0.24 J at a tip-speed ratio (TSR) of 0.8 at a constant speed of 0.7 m/s. From 1 TSR onward, a further decrease occurs in the power coefficient. That point indicates the optimum velocity at which maximum power exists. The pressure contour shows that maximum dynamic pressure exists at the convex side of the advancing blade. The value obtained at that place is −348 Pa for case 1. When the dynamic pressure increases, the power also increases. The same trend is observed for case 2 and case 3, with the same value of optimum TSR = 0.8. [ABSTRACT FROM AUTHOR]

Wind energy is gaining special interest worldwide due to the necessity of reducing pollutant emissions and employ renewable resources. Traditionally, horizontal axis wind turbines have been employed but certain situations require vertical axis wind turbines. With a view to improve the efficiency of a vertical axis wind turbine Savonius type, the present work proposes a bioinspired design blade profile relying on the Fibonacci spiral. This shape is repeatedly presented in nature and thus it leads to a bio-inspired blade profile. A numerical model was carried out and it was found that the Fibonacci shape improves the performance of the original Savonius shape, based on semicircular blade profiles. Particularly, the Fibonacci blade profile increases around 14% the power in comparison with the Savonius blade profile. Besides this comparison between Savonius and Fibonacci, a research study was carried out to improve the efficiency of the Fibonacci turbine. To this end, the effect of several parameters was analyzed: number of blades, aspect ratio, overlap, separation gap, and twist angle. Improvements on the average power greater than 30% were obtained. [ABSTRACT FROM AUTHOR]