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Marine current power has been utilized in recent years as one of the most foreseeable renewable energy sources. In this study, the optimal design of hydrofoil is carried out for hydrokinetic turbines to improve their hydrodynamic performance in Golden Gate Strait with the low-speed current. In order to design optimal hydrofoils for different sections of a blade, Particle Swarm Optimization (PSO) and XFoil are coupled. For hydrofoil's shape parameterization, the B-spline curve is used. The coordinate's values of the control points are designated to act as optimization parameters. Five hydrofoils from root to tip are designed for a turbine at low current speed with three blades. Hydrofoils are optimized from hub to tip in distances 0.4, 1.2, 2.4, 3.4, and 4.4 m. Optimum chord length and twist angle distribution along the blade are obtained using Harp_Opt, which is based on Blade Element Momentum theory. Finally, the power coefficient, rotational speed, cavitation criteria, and power are calculated for an optimized turbine and compared to the first turbine and Betz criterion. It is assured that cavitation will not occur at the tip of the blade which the linear velocity is maximum. The summation of cavitation number and minimum pressure coefficient (σ + Cp Min) is estimated to be 1.8. The power coefficient is computed using Harp_opt for both initial turbines with hydrofoil NACA 4415 and turbine with optimized cross sections from hub to tip. The power coefficient is improved 26% for speeds of 0.5–2 m/s and 50% for speeds of 2–3 m/s. An optimal marine current turbine which is useable for relatively lower currents is designed in this study by applying and combining different tools for different stages of research. • Optimal design of hydrofoil for hydrokinetic turbines in Golden Gate Strait. • Applying the Particle Swarm Optimization method coupled with XFoil. • B-spline curve foe parameterization of the hydrofoil shape. • Using Harp_Opt to obtain the optimum chord length and twist angle distribution along the blade. • Power improvement of 26% for speeds 0.5–2 m/s and 50% for speeds 2–3 m/s. [ABSTRACT FROM AUTHOR]

Abstract A cycle simulation code with integrated turbine design/optimization algorithm has been developed and utilized for the analysis/optimization of ≈ 10 M W e recompression supercritical carbon dioxide Brayton cycle. Integrated turbine design and optimization code computes the turbine design engaging the meanline design calculations as a function of received inlet conditions from the main cycle simulation code. Moreover embedded turbine code optimizes the turbine geometric by minimized the losses with in the turbine using response surface optimization methodology and returns turbine geometry and performance parameters to main code. In order to capture the swift variation in thermophysical properties of SCO 2 in the supercritical region, cycle design point code and embedded turbine codes are linked with NIST REFPROP program. Integrated turbine design/optimization code was validated using 3D Reynolds-Averaged-Navier-Stokes calculations. Response surface methodology was tested by comparing the 3D computation results for the turbine baseline and optimized designs. Finally recompression supercritical carbon dioxide Brayton cycle was analyzed under various conditions of cycle's minimum temperature, minimum pressure, and pressure ratio and split mass fraction. On the basis of the results it is recommended to use proposed model for more realistic and accurate modeling cycle design point analysis. Highlights • Development of cycle simulation tool with embedded turbine design/optimization code. • A meanline turbine design methodology is developed using real gas model. • The turbine rotor is optimized using Response Surface Method (RSM). • Conduct cycle analysis and optimization of recompression S C O 2 − B C. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle power systems represent a viable and efficient solution for the exploitation of medium-to-low temperature heat sources. Despite the large number of commissioned units, there is limited literature on the design and optimization of organic Rankine cycle power systems considering multistage turbine design. This work presents a preliminary design methodology and working fluid selection for organic Rankine cycle units featuring multistage axial turbines. The method is then applied to the case of waste heat recovery from a large marine diesel engine. A multistage axial turbine model is presented and validated with the best available data from literature. The methodology allows the identification of the most suitable working fluid considering the trade-off between cycle and multistage turbine designs. The results of the optimization of cycle and turbine suggest that the fluid n-butane yields the best compromise in terms of cycle net power output, turbine cost and efficiency for the considered case study. When a conservative design approach is adopted, the turbine features a two-stage configuration with supersonic converging nozzles and post-expansion. Conversely, a single-stage turbine featuring a supersonic converging-diverging nozzle and Mach number up to 2 is the resulting ideal choice when a more advanced design approach is implemented. [ABSTRACT FROM AUTHOR]

This work presents a systematic method for analysis and optimization of specific energy production (SEP) of pressure retarded osmosis (PRO) systems employing single-stage configuration as well as multistage design with interstage hydro-turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameter [ABSTRACT FROM AUTHOR]

This paper presents a novel optimization methodology based on both adjoint sensitivity analysis and trust-based dynamic response surface modeling to improve the performance of a modern turbine of a large civil aero-engine in the presence of high-fidelity geometry configurations. The system has been applied to the nonaxisymmetric hub and tip endwall optimization of a high-pressure turbine stage making use of multirow 3D simulations, parametric modeling, and rapid meshing of real geometry features such as rim seals and modeling of film cooling flows. It has been shown in previous papers that improvements gained using simplified models of the stage are lost when applying the high-fidelity geometry configuration. New results presented in this paper indicate that controlling the purge flow that exits the disk space through the rim seal at the hub of the main annulus is more significant than the reduction of secondary flows in the main passage. For a given rim sealing mass flow rate and whirl velocity, the nonaxisymmetric endwalls are optimized such that the detrimental impact of the sealing flow on the turbine performance is reduced, and hence, the stage efficiency is significantly increased. The traditional optimization approaches based on evolutionary methods or even sequential modifications for defining the endwalls shape are computationally demanding. Since turbomachinery industry continuously strive to reduce the design cycle time, in particular when high-fidelity 3D computational fluid dynamics (CFD) is used, the main body of this paper outlines the novel methods developed to produce a practical design in a very aggressively short design cycle time. [ABSTRACT FROM AUTHOR]

The oscillating water column (OWC), which is a wave energy extracting device, uses a bidirectional flow turbine to generate power. The device performance largely depends on the efficiency, torque and operating range of the turbine. The turbine with a larger operating range produces power during a wider wave height and period, both properties changing throughout the year or during each wave cycle. In this article, a numerical work relying on design optimization is reported to show the dependency of power extraction capability to the operating range of the turbine. Reynolds-averaged Navier-Stokes (RANS) equations were solved and a surrogate approximation model was constructed to find an optimal design. Design variables were blade sweep angles at the tip and mid sections. The objective function, to be maximized, is the torque coefficient. The optimal design delayed the flow separation and the peak efficiency dropped by 3.1%. At the same time, the relative power output and the relative stall point were increased by 29% and 18% compared to the reference case, respectively. [ABSTRACT FROM AUTHOR]

A novel combined cycle system comprising of a supercritical CO2 (sCO2) cycle and a Kalina cycle is proposed in this paper. Exergoeconomic comparison between the combined sCO2/Kalina cycle and the sCO2 cycle is investigated. The exergoeconomic models are established, and detailed parametric analyses are conducted for both cycles to reveal the influence of selected decision variables on cycle performance based on the self-build thermodynamic simulation platform. Besides, the parameters of both systems are optimized utilizing the exergetic efficiency and total product unit cost as the objective functions through genetic algorithm (GA). The results reveal that there is an optimal main compressor pressure ratio, an evaporating pressure, and a Kalina turbine inlet temperature that contribute to better system performance. A lower pinch point temperature difference in evaporator and a higher ammonia water mass fraction are beneficial to operation. The nuclear reactor and the sCO2 turbine are the most and second important components from the view of exergoeconomics. The total product unit cost and exergetic efficiency of the combined sCO2/Kalina cycle are 5.50% lower and 8.02% higher than the values for the stand-alone sCO2 cycle. [ABSTRACT FROM AUTHOR]

Recovering energy using microhydropower turbines on the flow of wastewater into or out of treatment plants has been shown to be a viable method of increasing the sustainability of the process. This paper examines the selection and design optimization of turbines at four wastewater-treatment plants in Ireland. Investigations were conducted to examine the impact of variation in flow rate due to storm events and changes in water demands on the optimal design of turbines. Turbine selection was also investigated in this setting, highlighting the optimum design in terms of power output and cost. Low-cost options for this low-head setting were examined through the use of multiple pump-as-turbines in parallel. The result highlights significant differences between power output estimates, using average flow rates and turbine efficiency, and those conducted using detailed design optimization. Underestimates of up to 12% were shown. The optimized systems efficiencies obtained across the sites ranged from 73 to 76%. Turbine costs ranged from 315 to 1; 708 €/kW depending on the type. Using pump-as-turbines produced system efficiencies of 58-62%. Using two pump-as-turbines, arranged in parallel, was shown to increase efficiency of these low-cost systems by a further 5%. [ABSTRACT FROM AUTHOR]

A novel modular pumped-storage scheme is investigated that uses elevated water storage towers and cement pools as the upper and lower reservoirs. The scheme serves a second purpose as part of the wastewater treatment process, providing multiple benefits besides energy storage. A small pumped-storage scheme has been shown to be a competitive energy storage solution for micro renewable energy grids; however, pumped-storage schemes have not been implemented on scales smaller than megawatts. Off-the-shelf runner designs are not available for modular pumped-storage schemes, so a custom runner design is sought. A preliminary hydraulic design for a pump-turbine runner is examined and optimized for increased pumping hydraulic efficiency using a response surface optimization methodology. The hydraulic pumping efficiency was found to have improved by 1.06% at the best efficiency point, while turbine hydraulic efficiency decreased by 0.70% at the turbine best efficiency point. The round-trip efficiency for the system was estimated to be about 78%, which is comparable to larger pumped-storage schemes currently in operation. [ABSTRACT FROM AUTHOR]

The response surface methodology was employed to make mathematical modeling and optimization of the temperature and pressure for centrifugal compressor. ProSimulator software was used for simulation of process parameter mainly temperature (x) and pressure (y). We considered a polynomial regression model equation between independent variable (x) and dependent variable (y). The simulation parameter revealed that the modeled values were in good agreement with simulated ones. [ABSTRACT FROM AUTHOR]

Nepal has an enormous amount of water resources and the topography gives rise to a huge hydropower potential. Out of 83,000 MW, only about 43,000 MW is economically and technically feasible. However, rivers of Nepal contain heavy quantities of sand particles. This is why the hydropower plants of this region face severe sand erosion problem. Erosion mechanism in hydropower is a complex phenomenon. It is a major technological challenge for R-O-R (Run off river) hydropower plants. There are several technologies to reduce erosion but none of them has proven to be economically viable. The hydraulic design of the turbine with a new design philosophy expected to reduce sand erosion considerably and this process is economic too. This paper describes the alternative optimized design of Francis turbine runner for large sediment load. The process involves optimization to obtain specific Francis runner blade using not defined ANSYS CFX parametric study. The process also includes analysis of the runner blade using CFX parametric study and Fluid structure interaction simulation for specific blade design. Design and drafting of the runner and part model design for FSI (Fluid Structure Interaction) analysis have also been described. [ABSTRACT FROM AUTHOR]

Within the framework of blade aerodynamic design, the maximum aerodynamic efficiency, power production, and minimum thrust force are the targets to obtain. This paper describes an improved optimization framework for blade aerodynamic design under realistic conditions, while considering multiple design parameters. The relationship between the objective function and the design parameters, such as the chord length, maximum chord, and twist angle, were obtained by using the second-order response surface methodology (RSM). Moreover, the identified parameters were organized to optimize the aerodynamic design of the blades. Furthermore, the initial and optimized blade geometries were compared and showed that the performance of the optimized blade improved significantly. In fact, the efficiency was increased by approximately 10%, although its thrust was not varied. In addition, to demonstrate the improvement in the resulting optimized blades, the annual energy production (AEP) was estimated when installed in a specific regional location. The result showed a significant improvement when compared to the baseline blades. This result will be extended to a new perspective approach for a more robust optimal design of a wind turbine blade. [ABSTRACT FROM AUTHOR]

This work aims at designing and optimizing the performance of a small Horizontal-Axis-Wind-Turbine to obtain a power coefficient (CP) higher than 40% at a low wind speed of 5 m/s. Two symmetric in shape airfoils were used to get the final optimized airfoil. The main objective is to optimize the blade parameters that influence the design of the blade since the small turbines are prone to show low performance due to the low Reynolds number as a result of the small size of the rotor and the low wind speed. Therefore, the optimization process will select different airfoils and extract their performance at the design conditions to find the best sections which form the optimal design of the blade. The sections of the blade in the final version mainly consist of two different sections belong to S1210 and S1223 airfoils. The optimization process goes further by investigating the performance of the final design, and it employs the blade element momentum theory to enhance the design. Finally, the rotor-design was obtained, which consists of three blades with a diameter of 4 m, a hub of 20 cm radius, a tip-speed ratio of 6.5 and can obtain about 650 W with a Power coefficient of 0.445 at a wind-speed of 5.5 m/s, reaching a power of 1.18 kW and a power coefficient of 0.40 at a wind-speed of 7 m/s. [ABSTRACT FROM AUTHOR]

Savonius wind turbines are the most suitable devices used in urban areas to produce electrical power. This is due to their simplicity, ease of maintenance, and acceptable power output with a low speed and highly variable wind profile. However, their efficiency is low, and the development of optimization tools is necessary to increase the total power output. This work presents a metamodel-based method to optimize the size and shape of a set of deflector plates to reduce the reverse moment of the turbine, using a genetic algorithm combined with an artificial neural network, reducing the computational cost. A parametrization of the deflectors geometry is proposed, and a Computational Fluid Dynamics model was implemented to train and validate the artificial neural network. The method was applied to design the deflectors of an actual 8-blade, 1[kW], 2.5[m] height turbine. Results showed an efficiency increment of 30%, from 0.215, to 0.279 in the turbine with the optimized deflectors. Furthermore, it is capable of producing power at 4[m/s], while the reference design had null power at that point. This methodology demanded 159 h, a substantial reduction of the computational cost of up to 97% in contrast to the classical simulation-based optimization approach. [ABSTRACT FROM AUTHOR]

The loading-to-flow diagram is a widely used classical method for the preliminary design of radial turbines. This study improves this method to optimize the design of radial turbines in the early design phase under variable operating conditions. The guide vane outlet flow angle is a key factor affecting the off-design performance of the radial turbine. To optimize the off-design performance of radial turbines in the early design phase, we propose a hypothesis that uses the ratio of the mean velocity of the fluid relative to the rotor passage with respect to the circumferential velocity of the rotor as an indicator to indirectly and qualitatively estimate the rotor loss, as it plays a key role in the off-design efficiency. Theoretical analysis of rotor loss characteristics under different types of variable operating conditions shows that a smaller design value of guide vane outlet flow angle results in a better off-design performance in the case of a reduced mass flow. In contrast, radial turbines with a larger design value of guide vane outlet flow angle can obtain a better off-design performance with increased mass flow. The above findings were validated with a mean-line model method. Furthermore, this study discusses the optimization of the design value of guide vane outlet flow angle based on the matching of rotor loss characteristics with specified variable operating conditions. It provides important guidance for the design optimization of multistage radial turbines with variable operating conditions in compressed air energy storage (CAES) systems. [ABSTRACT FROM AUTHOR]

Rapid aerodynamic design and optimization is essential for the development of future turbomachinery. The objective of this work is to demonstrate a methodology from 1D mean-line-design to a full 3D aerodynamic optimization of the turbine stage using a parameterization strategy that requires few parameters. The methodology is tested by designing a highly loaded and efficient turbine for the Purdue Experimental Turbine Aerothermal Laboratory. This manuscript describes the entire design process including the 2D/3D parameterization strategy in detail. The objective of the design is to maximize the entropy definition of efficiency while simultaneously maximizing the stage loading. Optimal design trends are highlighted for both the stator and rotor for several turbine characteristics in terms of pitch-to-chord ratio as well as the blades metal and stagger angles. Additionally, a correction term is proposed for the Horlock efficiency equation to maximize the accuracy based on the measured blade kinetic losses. Finally, the design and performance of optimal profiles along the Pareto front are summarized, featuring the highest aerodynamic performance and stage loading. [ABSTRACT FROM AUTHOR]