•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.
Studies on lift-type VAWTs are far fewer than those on horizontal VAWTS, especially in the field of airfoil, which is regarded as the fundamental of VAWT design. Existing researches seldom ...systematically and efficiently touch upon a specific airfoil family. Thus, a coupled approach comprising two steps was used in this paper to assess an airfoil family, wherein the first step was the orthogonal algorithm combined with an automatic computational fluid dynamic analysis (ACFDA) module, and the second step was the combination of the one-factor at a time (OFAAT) algorithm and the ACFDA module.
Results demonstrate that among three design parameters, the thickness-chord ratio (TCR) had the biggest effect on CP while the maximum thickness in tenths of chord (MTITOC) had the smallest influence on CP. By this approach, we found a desired airfoil having maximum power coefficient(CPMAX) was 0.4585, app. 15.5% higher than that of the previously widely used rotor NACA 0015. In addition, detailed flow data (field) dispersing in the vicinity of the airfoil were visualized to reveal the effect of each design parameter on airfoil's aerodynamic behavior. Lastly, this coupled approach can be used to assess any airfoil family that can be parameterized and has several design parameters.
•Orthogonal algorithm was coupled with ACFDA module.•25 different airfoils were evaluated in this paper.•The impact weight of each design parameter was found.•15.5% more power coefficient was gained from a desirable airfoil.•A systematic and efficient evaluation approach for any Darrieus rotor's airfoil family.
Vertical axis wind turbines (VAWTs) are superior because they have compact structure, good wind adaptability and strong scalability. The coupling dynamic response mechanisms between different ...configurations of wind turbines and floating platforms are different. Based on the CFD method, dynamic fluid body interaction (DFBI), overlapping grid and dynamic grid techniques are used for numerical simulations. The force characteristics and self-starting features of H-type and Φ-type VAWTs are compared. The aerodynamic performance and motion response of the floating VAWT (FVAWT) are studied under different tip-speed ratios (TSR) and aspect ratios (η). The results show that the power coefficient (Cp) of H-type and Φ-type FVAWTs reaches the peak when TSR = 6 and TSR = 7, respectively. The optimal η for both is 1.2. The H-type FVAWT improves the Cp by 34.3% compared to Φ-type FVAWT. H-type FVAWT has a large thrust and excellent stability. The Φ-type FVAWT requires less initial thrust, and the self-starting performance is 12% superior to H-type FVAWT. With the increase of TSR and η, the heave motion of both FVAWTs is almost unaffected, but the pitch motion sensitivity is stronger. The heave amplitude of H-type FVAWT is 282% larger than Φ-type FVAWT, which has a gain effect on energy conversion. The Φ-type FVAWT has better safety. The strengthened structure of Φ-type VAWT has a noticeable impact on velocity and vortex distribution. In addition, the aerodynamic and hydrodynamic performance of the FVAWT is improved.
•A nonlinear fully coupled time domain model including vertical axis wind turbine, floating platform and mooring system is established.•The difference of energy efficiency and thrust characteristics between floating vertical axis wind turbine with different configurations are studied.•The optimal parameters and strengthening structure design of megawatt vertical axis wind turbine with different configurations are explored.•The coupling mechanism and energy conversion characteristics between vertical axis wind turbine and floating platform are studied.
Hydropower generation is an important part of global renewable energy development. The vertical axis hydrokinetic turbine (VAHT) is a typical device to capture the kinetic energy of water. The ...optimization of its hydrodynamic performance can improve power coefficient. In this study, the Taguchi method was used to optimize the typical parameters of the vertical axis turbine, i.e., airfoil (NACA), pitch angle (β), enwinding ratio (ϖ), solidity ratio (σ), and small shaft position (O). An orthogonal array with five parameters and four levels was established; then, sixteen runs were simulated using computational fluid dynamics (CFD) software. A signal-to-noise (S/N) ratio analysis of the CFD simulation results was carried out, and the hydrodynamic performance of the optimized VAHT was studied. The results show that the influence strength order of each parameter on the power coefficient of the VAHT is featured by the relation NACA >σ > O > ϖ > β. According to the S/N ratio, the optimal combination of the five factors is as follows: NACA = 0020, β = 0°, ϖ = 1.25, σ = 0.382, and O = 0.5. In comparison with the initial design, the optimized minimum self-starting torque coefficient of the turbine is increased by 15.9%, which means that the self-starting performance is optimized. The power coefficient (CP) of optimized turbine is 0.1951, which is 17.59% higher than in the initial design, and the power coefficient fluctuation is 87.56% lower. Finally, the research findings could provide a reference for the optimal design of vertical axis turbines.
There are several main troubles in urban wind energy utilization such as noise and installation space. Vertical Axis Wind Turbine (VAWT) runs low noise and low center of gravity, which is more ...suitable placed on the building roof installation. This paper propose that VAWT is innovatively installed outside of existing buildings that as its support frame, to expand the VAWT sweep area and ensure the building safety by decreased turbine gravity center. The build-in entity model of VAWT is present to study the dynamic characteristics of the structure. We prepared the VAWT model with 520 mm rotor diameter, and eight cylinders of build-in entity diameters for numerical simulation and experiment. The results show that the VAWT peak value of Power Coefficient (CP) decreases with the increase of the built-in entity diameter at same Tip Speed Ratio (TSR). When the built-in entity diameter decreased to 50% rotor diameter, the CP loss is less than 20% not linear in 50%. In the case of low TSR, the wind turbine with larger diameter build-in entity obtains higher torque coefficient and CP. It can be deduced that VAWT with built-in entity widens the working range and improves turbine self-starting capability. This study provide a reference for combination of building and VAWT.
•The build-in entity model of VAWT that installed outside of buildings is proposed.•Investigation on the effect of different entity diameter on VAWT performance.•Numerical simulation and experiment analysis of VAWT power coefficient (CP).•Improvement the working range and the self-starting capability of wind turbine.
•The maximum value of torque and power coefficients appear for thinner airfoils in comparison to thicker airfoils.•A novel parameter for checking the actual obtainable performance of HATCT is ...proposed.•The superiority of the maximum power coefficient for thicker airfoils stands on maximum value in comparison to thinner airfoils.•Airfoils with rapid changes in curvature are predisposed to reduce the value of torque and power coefficients.•Airfoils which include a higher average of thickness on the pressure side, the probability of fatigue hazard reduces.
One of the most essential parameters contributing to the performance of hydrokinetic tidal current turbine is its geometry. In this study, the effect of curvature, thickness, and blade pitch angle (BPA0) with a glimpse at the turbine performance considering the probability of fatigue loading presence are investigated. Six different airfoils based on possessing the acceptable lift to drag ratio were selected and used to design turbine blades using the blade element momentum theory. Computational fluid dynamic was employed for simulation the performance of turbines at diverse tip speed ratios (TSR)s and BPA0s so that the condition for obtaining the maximum performance was determined. An experimental setup was fabricated to validate the computational results. The question is: To what extent this maximum performance condition is possible to be implemented in practice? To answer this question, a parameter called superiority of maximum power coefficient (SCPmax) was introduced to assess the usefulness of employment of each airfoil based on maximum power coefficient (CPmax), thrust coefficient (CTh), and the percentage of airfoil thickness (%t) and exhibit the utility of maximum performance against the probability of fatigue hazard. Results indicated that at higher values of BPA0s, by increasing the thickness, the maximum amount of torque enhances. Furthermore, the augmentation in the TSR leads to increase in CPmax at the lower value of BPA0 so that the difference between the lowest (for NACA 65(3)-618) and highest (for NACA 4412) CPmax is around 66%. In contrast, the maximum value of SCPmax belonged to the NACA65(3)-618 due to lower CTh and more %t, while the minimum amount of SCPmax appertained to the NACA2410 which has the minimum %t.
The installation of wind turbines in urban sites requires consideration of the wind characteristics affecting the energy production (turbulence, environment roughness due to the surrounding buildings ...…), the self-starting capability and the type, hence the performance, of the wind turbine. In this paper, a three-dimensional CFD analysis of an aerodynamic Savonius wind turbine is performed under steady wind conditions. The inclusion of a deflector was also investigated, and the performance compared to the initial design.
Results of the 3D analysis showed that an optimized axisymmetric deflector improves the power coefficient in all wind directions and over the entire operating range of the turbine. The deflector also increased the average starting torque by 30%, thus extending the operating range of the turbine with respect to the wind speed.
•Design of a new deflector type with a simple axisymmetric shape to improve the intrinsic capacities of a Savonius wind turbine.•Numerical optimization of the concentrator.•3D dynamic modeling of the concentrator and the wind turbine.•Profits and highlighting of the obtained results compared to existing deflectors/concentrators.
The power coefficient parameter represents the aerodynamic wind turbine efficiency. Since the 1980s, several equations have been used in the literature to study the power coefficient as a function of ...the tip speed ratio and the pitch angle. In this study, these equations are reviewed and compared. A corrected blade element momentum algorithm is used to generate three sets of data representing different ranges of wind turbines, going from 2 to 10 MW. With this information, two power coefficient models are proposed and shared. One model is based on a polynomial fitting, whereas the other is based on neural network techniques. Both were trained with the blade element momentum model output data and showed good behaviour for all operating ranges. In the results, compared to all the algorithms found in the literature, the proposed models reduced the power coefficient error by at least 55% compared to the best numerical approximation from the literature. An error reduction in the power coefficient parameter may have a large impact on many wind energy conversion system studies, such as those treating dynamic and transient behaviours.
Straight-bladed Vertical Axis Wind Turbines (SB-VAWTs) have recently attracted much attention as they are considered to be an option for wind energy utilization, whether in offshore or urban ...environments. In this study, the effects of airfoil chord length and rotor diameter (circumference) on the aerodynamic characteristics of SB-VAWTs were explored by numerical simulation. The research object is a three-bladed SB-VAWT fitted with a NACA0018 symmetric airfoil. A dimensionless parameter RCC is proposed, that is, the ratio of the airfoil chord length to the circumference of the rotor. There are 43 different combinations of chord length and rotor diameter designed for the present study, making the RCC ranges between 1.4% and 57.3%. When the length of airfoil chord is constant and the diameter of rotor changes, the recommended RCC is supposed to be approximately 8% for the SB-VAWT. Differently, when the diameter of the rotor is constant and the length of airfoil chord changes, the recommended RCC is supposed to range between 9.5% and 13.4%. Based on the results, it is confirmed that the RCC is a significant parameter for the design of the SB-VAWT. This study is expected to provide a practical reference for the parametric structural design of SB-VAWTs.
•Three-bladed SB-VAWT with NACA0018 symmetric airfoil was selected as the research object.•A dimensionless parameter RCC was proposed as the ratio of blade airfoil chord length to rotor circumference.•Effect of RCCs between 1.4% and 57.3% on rotor aerodynamics was researched by numerical simulation.•The optimal RCCs for airfoil chord length and rotor diameter were analyzed and recommended, respectively.
NASA's SR3 8-bladed rotor with a rotational speed of 6350 rpm, an advance ratio of 3.6, and a transonic Mach Number of 0.8 is utilized to evaluate the aerodynamic and rotor effectiveness predictive ...ability of a CFD simulation using the Ansys commercial software. The experimentally tested model 1 included eight 45° swept blades that were tested at a design operating altitude of 10.68 km (35,000 ft.) and it is the one with the most data in the public domain. In the model, blade sweep and the distinct contour of the spinner and nacelle design were implemented to reduce compressibility losses. The primary goal of this research is to compare performance predictions with the experimental results for power coefficient and efficiency evaluation. Analyses are carried out on a single rotating zone separated by a sliding mesh boundary. We also look at the accuracy of recording downward velocities and swirling angles in the propeller's wake, with the goal to use the RANS technique to investigate how these wake parameters react with aerodynamic surface and the results are compared with the experimental results. Initial computational findings demonstrate increased correlation with wind tunnel measurements at 63.3° degrees pitch.
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