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Showing papers on "Tip-speed ratio published in 2023"


Journal ArticleDOI
TL;DR: In this article , the influence of using dielectric barrier discharge (DBD) plasma actuators on a cycloidal VAWT in combination with blade rotations and oscillations performance is analyzed through computational fluid dynamics (CFD) and a user defined function (UDF) is loaded into ANSYS FLUENT to describe and control the complex dynamic pitching movements of the blades and the plasma effect.
Abstract: Harvesting a maximum power from wind turbines especially at low tip speed ratio still remains a challenge. Vertical axis wind turbines (VAWTs) suffer periodically from stall which leads to aerodynamic losses and structural load fluctuation. In which improving their efficiency by increasing the generated power is an essential goal. The focus of the current study is to improve VAWT efficiency by analyzing the influence of using dielectric barrier discharge (DBD) plasma actuators on a cycloidal VAWT in combination with blade rotations and oscillations performance. The analysis is performed through computational fluid dynamics (CFD) and a user defined function (UDF) is loaded into ANSYS FLUENT to describe and control the complex dynamic pitching movements of the blades and the plasma effect. A sliding mesh technique coupled with the turbulence model k-ω SST is used in the simulations. The influence of the plasma actuation on the velocity contour, vorticity field and the evolution of power coefficient is analyzed. For better performance, a control law is proposed to regulate the plasma actuators operation as the blades rotate in azimuth direction. The results showed that by applying the DBD plasma actuation, with the control law, we can improve the power coefficient by 8% as compared to the base case and 38% as compared to a conventional fixed pitch vertical axis wind turbine.

6 citations


Journal ArticleDOI
TL;DR: In this paper , the physical mechanisms of counter-rotating and corotating VGs on a flat plane at different incoming wind directions were analyzed to improve the aerodynamic performance of a wind turbine.

4 citations


Journal ArticleDOI
TL;DR: In this article , an experimental study carried out in a wind tunnel serves two purposes: to examine blade solidity effect on the power Cp and torque coefficients Cτ vs. tip-speed ratio curves at a fixed number of blades and to investigate its effects on the velocity distributions using stereoscopic particle image velocimetry (SPIV).

3 citations


Journal ArticleDOI
TL;DR: In this paper , the authors used the Boltzmann method and very large eddy simulation (LBM-VLES) to predict the aerodynamic performance of a complete scale model H-Darrieus vertical axis wind turbine (VAWT) with end plates at different operating conditions.
Abstract: Purpose The purpose of the paper is to predict the aerodynamic performance of a complete scale model H-Darrieus vertical axis wind turbine (VAWT) with end plates at different operating conditions. This paper aims at understanding the flow physics around a model VAWT for three different tip speed ratios corresponding to three different flow regimes. Design/methodology/approach This study achieves a first three-dimensional hybrid lattice Boltzmann method/very large eddy simulation (LBM-VLES) model for a complete scaled model VAWT with end plates and mast using the solver PowerFLOW. The power curve predicted from the numerical simulations is compared with the experimental data collected at Erlangen University. This study highlights the complexity of the turbulent flow features that are seen at three different operational regimes of the turbine using instantaneous flow structures, mean velocity, pressure iso-contours, blade loading and skin friction plots. Findings The power curve predicted using the LBM-VLES approach and setup provides a good overall match with the experimental power curve, with the peak and drop after the operational point being captured. Variable turbulent flow structures are seen over the azimuthal revolution that depends on the tip speed ratio (TSR). Significant dynamic stall structures are seen in the upwind phase and at the end of the downwind phase of rotation in the deep stall regime. Strong blade wake interactions and turbulent flow structures are seen inside the rotor at higher TSRs. Research limitations/implications The computational cost and time for such high-fidelity simulations using the LBM-VLES remains expensive. Each simulation requires around a week using supercomputing facilities. Further studies need to be performed to improve analytical VAWT models using inputs/calibration from high fidelity simulation databases. As a future work, the impact of turbulent and nonuniform inflow conditions that are more representative of a typical urban environment also needs to be investigated. Practical implications The LBM methodology is shown to be a reliable approach for VAWT power prediction. Dynamic stall and blade wake interactions reduce the aerodynamic performance of a VAWT. An ideal operation close to the peak of the power curve should be favored based on the local wind resource, as this point exhibits a smoother variation of forces improving operational performance. The 3D flow features also exhibit a significant wake asymmetry that could impact the optimal layout of VAWT clusters to increase their power density. The present work also highlights the importance of 3D simulations of the complete model including the support structures such as end plates and mast. Social implications Accurate predictions of power performance for Darrieus VAWTs could help in better siting of wind turbines thus improving return of investment and reducing levelized cost of energy. It could promote the development of onsite electricity generation, especially for industrial sites/urban areas and renew interest for VAWT wind farms. Originality/value A first high-fidelity simulation of a complete VAWT with end plates and supporting structures has been performed using the LBM approach and compared with experimental data. The 3D flow physics has been analyzed at different operating regimes of the turbine. These physical insights and prediction capabilities of this approach could be useful for commercial VAWT manufacturers.

3 citations


Journal ArticleDOI
TL;DR: In this article , the influence of VGs on the hydrodynamic characteristics of the turbine blades of the NACA 4418 hydrofoil has been investigated using a numerical simulation.
Abstract: Tidal turbine blades are prone to flow separation in the boundary layer under high speed or high angle of attack(AOA), which will reduce energy efficiency and even the stall damage of the blades. This paper proposes introducing the flow control theory of Vortex Generators(VGs) to tidal turbines and studying the influence of VGs on the hydrodynamic characteristics of the tidal turbine blades. Firstly, a numerical study is performed to investigate the effects of VGS on the hydrodynamic performance of the NACA 4418 hydrofoil. The impact of different parameters, such as VG arrangement, spacing, height and length, on the hydrodynamic performance of hydrofoil is studied by the CFD method. The results show that VGs can effectively suppress the flow separation and improve the maximum lift coefficient of the hydrofoil. The influence of VGs on flow separation characteristics of horizontal axis tidal turbines (HATT) is studied by the CFD method. The results show that the flow separation of turbine blades mainly occurs at the root part of the suction surface, and the flow separation region expands radially as the flow velocity increases. VGs can effectively reduce the flow separation area on the suction side of turbine blades by suppressing the flow separation effect. Compared with the turbine blades without VGs, the power coefficient of turbine blades with VGs is increased by up to 5%. The flume experiment verifies the accuracy of the simulation results.

1 citations


Journal ArticleDOI
17 Feb 2023-Energies
TL;DR: In this article , a power control algorithm of a variable-speed fixed-pitch horizontal-axis lift-type 20 kW small wind turbine (SWT) was proposed and verified through dynamic simulations.
Abstract: In this study, a power control algorithm of a variable-speed fixed-pitch horizontal-axis lift-type 20 kW small wind turbine (SWT) was proposed and verified through dynamic simulations. The power control algorithm proposed in this study consists of algorithms for Region II to track the maximum power coefficient, for Region II-1/2 to maintain the rated rotor speed, and for Region III to maintain the rated power. To verify the proposed power control algorithm, simulations were performed at the rated wind speed and above the rated wind speed, to which turbulence intensity based on the IEC regulation’s normal turbulence model was applied. As a result, it was confirmed that the proposed controller operates properly in the whole three regions including Regions II, II-1/2, and III. The controller performance was then compared with the variable-speed variable-pitch power controller. Although the performance of the proposed controller was considered good for the target VSVP wind turbine, it was lower than that of the conventional controller applied to the same wind turbine. Compared to the VSVP wind turbine, the VSFP wind turbine with the proposed controller was found to have higher mean loads on the blade and the tower but the fatigue loads in terms of Damage Equivalent Load (DEL) were found to be reduced.

1 citations


Journal ArticleDOI
19 May 2023-Energies
TL;DR: In this article , a new blade geometry with guide gap flow was proposed for the Savonius wind turbine blade design, which was analyzed using 3D ANSYS CFX software.
Abstract: Small-scale vertical-axis wind power generation technologies such as Savonius wind turbines are gaining popularity in suburban and urban settings. Although vertical-axis wind turbines (VAWTs) may not be as efficient as their horizontal-axis counterparts, they often present better opportunities for integration within building structures. The main issue stems from the suboptimal aerodynamic design of Savonius turbine blades, resulting in lower efficiency and power output. To address this, modern turbine designs focus on optimizing various geometric aspects of the turbine to improve aerodynamic performance, efficiency, and overall effectiveness. This study developed a unique optimization method, incorporating a new blade geometry with guide gap flow for Savonius wind turbine blade design. The aerodynamic characteristics of the Savonius wind turbine blade were extensively analyzed using 3D ANSYS CFX software. The optimization process emphasized the power coefficient as the objective function while considering blade profiles, overlap ratio, and blade number as crucial design parameters. This objective was accomplished using the design of experiments (DOE) method with the Minitab statistical software. The research findings revealed that the novel turbine design “OR0.109BS2BN2” outperformed the reference turbine with a 22.8% higher power coefficient. Furthermore, the results indicated a trade-off between the flow (swirling flow) through the gap guide flow and the impact blockage ratio, which resulted from the reduced channel width caused by the extended blade tip length.

1 citations


Journal ArticleDOI
TL;DR: In this paper , the NACA-4412 type aerofoil was chosen as a departure point for the blade design, and a variation of the maximum pitch angle of 6°, 10° and 12° at an optimum angle of attack of 5°, 7°, and 9° were implemented respectively for Designs 1, 2 and 3.
Abstract: A low-cost small 500W wind generator was used as a basis for the prototype development. The research was primarily focused on the determination of the type of aerofoil for improved rotor blades and pitch angle, and for adapting the number of blades in order to optimize the power output from the prototype, for low wind-speed inland conditions in Soweto. NACA-4412 type aerofoil was chosen as a departure point for the blade design, and a variation of the maximum pitch angle of 6°, 10°, and 12° at an optimum angle of attack of 5°, 7°, and 9° were implemented respectively for Designs 1, 2 and 3. With the Soweto area having an average wind speed of 2.3m/s (8.28km/h), 3-, 5-, and 7-blade sets were subsequently developed, implemented, and tested. Prototype 1 produced a maximum output power of 8.2W at 4.2km/h wind speed. Prototype 2 yielded a maximum output power of 12.5W at 4.2km/h, and Prototype 3, generated a very useful power output of 39.5W during testing. The maximum power output was achieved at an average wind speed of 1.17m/s (4.2km/h). Moreover, the developed prototype designs were also tested for self-regulation in case of high-speed gust conditions. Prototype 3, with a 12° maximum pitch angle during operation in high gust conditions, had its blades control high speed. A drawback pressure occurred on the back side of the blades and tangent drag was developed normally to the blade rotation direction, consequently limiting the maximum speed of the rotor and acting as a self-regulation mechanism with regard to maximum achievable speed. The other two designs suffered from over-speeding tendencies in high gust speed conditions, also causing noise and turbulence.

1 citations


Journal ArticleDOI
TL;DR: In this paper , a proof-of-concept study for the application of Vortex Generators (VGs) on tidal turbines in view of increasing their performance is presented, which demonstrates for the first time the potential of passive VGs to be included either in the design process of a tidal turbine blade or as a retrofit solution.

1 citations


Journal ArticleDOI
TL;DR: In this paper , a bionic blade shape of the Savonius-type wind turbine rotor inspired by sandlances is proposed, combined with an optimization step in order to maximize performance.

1 citations


Journal ArticleDOI
TL;DR: In this article , the effects of pitch angle, electrical load, wave characteristics, and current velocity on turbine performance are examined, and the results demonstrate the direct relationship between power, momentum, thrust, rotor speed and current velocities.

Journal ArticleDOI
TL;DR: In this paper , the best pitch angle for hybrid Savonius Darrieus dual shaft vertical wind turbines is recommended according to the wind speed, pitch angle of 5 degrees for 1 m/s wind speed.
Abstract: All Vertical turbines use a fixed pitch angle; the determination of the pitch angle is very influential on the characteristics of a vertical wind turbine. In the initial stages of planning a Savonius Darrieus vertical turbine, an experiment was carried out to determine the best pitch angle, and the best pitch angle was 7 degrees. In its development, many designs have changed from the initial design, so it is necessary to carry out field experiments to get the best pitch angle. The purpose of this study is to recommend the best pitch angle for hybrid Savonius Darrieus dual shaft vertical wind turbines. That suit each wind characteristic with the variable performance tip speed ratio (TSR) also (λ), coefficient of performance (Cp), mechanical power and mechanical energy. Data is collected for 8 hours in real-time, using proximity sensors, anemometers, and an Arduino Mega to record and store data on a computer. The data collection interval at every 10 seconds. The data obtained is the RPM of the rotor and the RPM of the anemometer. The results of this study are the recommended pitch angle according to the wind speed, pitch angle of 5 degrees for 1 m/s wind speed, pitch angle of 8 degrees for 2 m/s a, and pitch angle of 8 degrees for 3 m/s wind speed.

Journal ArticleDOI
01 Feb 2023-Energy
TL;DR: In this paper , the authors used surrogate-based optimization (SBO) to obtain the optimum configuration of Savonius wind turbine which results in maximum power coefficient (Cp) in order to achieve that Surrogatebased optimization was used for obtaining the optimum values of investigated parameters.

Journal ArticleDOI
01 May 2023-Energy
TL;DR: In this article , a three-dimensional numerical study has been conducted by solving the unsteady Reynolds Averaged Navier Stokes equations with shear stress transport (SST) k-omega turbulence model to investigate the power production efficiency of a 3-bladed H-Darrieus vertical axis wind turbines (HDWT) using S-1046 airfoil under accelerated wind conditions of the cooling tower exhaust system.

Journal ArticleDOI
TL;DR: In this article , the aerodynamic performance of the contra-rotating Darrieus turbine configuration was investigated by comparing it to the single-rotor VAWT under the same conditions, and the results showed that in terms of output power or Power coefficient (Cp), the contrarotating has a greater value than the single rotating configuration.
Abstract: The new Contra-rotating Darrieus turbine configuration has been invented to enhance the V ertical Axis Wind Turbine (VAWT) performance. This configuration increases the relative rotational speed of the generator, resulting in higher output power. It is well known that the increase can reach four times the output power. However, how the Darrieus turbine VAWT contra- rotating configuration influences its aerodynamic performance still needs to be discovered. This study investigates the aerodynamic performance of the contra-rotating configuration by comparing it to the single-rotating Darrieus turbine VAWT under the same conditions. The freestream speed is 5 m/s, with TSR varying from one to two intervals of 0.2. This research is being completed using Computational Fluid Dynamics (CFD) 3D cases with an Unsteady Reynold Average Navier-Stokes (URANS) equation as the turbulent model equation. The results of this study show that in terms of output power or Power coefficient (Cp), the contra-rotating has a greater value than the single- rotating configuration. However, in all TSR variations, contra-rotating outperforms single-rotating in terms of aerodynamic performance or moment coefficient (Cm). This is due to the fact that the aspect ratio of stage 1 contra-rotating rotor is lower than the single-rotating rotor, resulting in more significant blade tip losses in contra-rotating. Theflow was discovered through the gap between stages 1 and 2 contra-rotating, providing additional momentum. This phenomenon increases Cm at an azimuth angle of 200°-255°.

Journal ArticleDOI
01 Feb 2023-Energy
TL;DR: In this paper , a variable solidity Darrieus-type vertical axis wind turbine (D-VAWT) was designed to solve the self-starting problem and optimize the aerodynamic performance.

Journal ArticleDOI
TL;DR: In this article , different soft computing methods, namely CatBoost, Artificial Neural Network (ANN), Random Forests (RF), Multivariate Adaptive Regression Splines (MARS), Adaptive Neuro-Fuzzy Inference System (ANFIS), ANFIS-Genetic algorithm (ANN-GA), SLIME MULTI-MMA, and Linear Regression (LR) were used to predict the power coefficient of Savonius hydrokinetic turbines for the first time.

Journal ArticleDOI
25 Mar 2023-Energies
TL;DR: In this article , the Aeroleaf Savonius Wind Turbine was developed numerically and a computational fluid dynamics simulation was performed on this new type of wind tree to predict its performance, which indicated that the system could accept wind from any direction and could start rotating as soon as the site had a cut in wind speed of 3.3 m/s.
Abstract: Large wind turbines of the horizontal axis are commonly used to gather wind energy; however, their performance is found to be constrained in conditions of erratic and low-speed wind flow. In contrast, low wind conditions—which are typically present in dense urban areas—are found to favour vertical axis wind turbines (VAWT). These turbines have a simple design, are inexpensive and quiet, and are discovered to be better in low wind situations. In this research, we have chosen wind tree applications to absorb the most available wind energy. The new Aeroleaf Savonius Wind Turbine was developed numerically and a computational fluid dynamics simulation was performed on this new type of Savonius tree to predict its performance. The results indicated that the system could accept wind from any direction and could start rotating as soon as the site had a cut in wind speed of 3.3 m/s. The rotor speed increased by 10.4% from 5.5 to 6.3 m/s wind speed at 0.45 tip speed ratio. The tip speed ratio is 0.52 at the site’s high wind speed, and under these circumstances, the maximum Cp is 12.9%. The turbine was able to produce superior performance coefficients, according to the results.

Journal ArticleDOI
TL;DR: In this paper , a literature study method was used to compare and summarize data optimizing variations in the number of blades and wind speed on horizontal axis wind turbines from various sources, and the results showed that the wind speed and blade rotation yield are directly proportional to the energy produced, since the effect of the ratio of tip speed is inversely proportional to wind speed.
Abstract: The utilization of wind turbines is able to convert wind energy into electrical energy. It is recorded from the DG of NREEC source that Indonesia has a wind energy potential of 60.6 Giga Watt (GW) with a total renewable energy potential of 442GW. One of the most common types of wind turbines is the horizontal axis wind turbine. This study uses a literature study method that aims to compare and summarize data optimizing variations in the number of blades and wind speed on horizontal axis wind turbines from various sources. The results of the study are known that the pinwheel power generated by the rotation of the pinwheel blade produces energy that is converted into electrical energy. The wind speed and blade rotation yield are directly proportional to the energy produced. The greater the wind speed given to the turbine, the higher the rotation. Variations in the number of blades result in variations in rotational properties, since the effect of the ratio of tip speed is inversely proportional to wind speed. The performance of horizontal axis wind turbines can be optimized by applying blade design using chord and twist linearization methods. The greatest efficiency of the counter-rotational horizontal shaft wind turbine is achieved at a blade angle of 10° and a wind speed of 4.03m/s, resulting in a maximum efficiency of up to 71.8%, which is higher than the optimal single-rotor power coefficient of 59%. This means dual-rotor wind turbines are more efficient at converting energy than single-rotor wind turbines.

Journal ArticleDOI
TL;DR: In this article , the performance of the H-Darrieus VAWT having NACA 0018 airfoil by use of semi-cylindrical attachments at the trailing edge and hybridization using two bladed S-Savonius rotor with zero overlap conditions was examined at a low wind speed of 4 m/s.

Journal ArticleDOI
TL;DR: In this article , a new wind generating device coupled with a flow convergent was proposed to increase the performance at low wind speed, and the effect of the pulley transmission ratio on the mechanical values of the generator, the impact of the operating gas in terms of angular velocity, power and torque on the generator shaft was clearly determined.
Abstract: Aims: Researchers are more and more focused on finding ways to optimize renewable energy sources. One of the more promising of these renewable energies is wind energy. However, these wind resources are very localized and selective. There is also significant potential for wind resources available at low densities or low wind speeds. The objective of this research is to exploit these resources. Methodology: To do so, this study proposes a new wind generating device coupled with a flow convergent in order to increase its performance at low wind speed. This new wind device is designed under Solidworks and analyzed with Matlab software. Several parameters are simulated. The effect of the pulley transmission ratio on the mechanical values of the generator, the impact of the operating gas in terms of angular velocity, power and torque on the generator shaft was clearly determined. Results: It appears that the power at the input of the wind device is multiplied by the square of the ratio of the output and input velocities, the flow passing through the convergent being constant. The torque on the generator decreases with the increase of the transmission ratio while its speed increases. However, for a fixed transmission ratio, the speed remains constant while the torque and power increase with the speed at the inlet of the convergent. On the other hand, it is noted that, the lower the adiabatic coefficient of the gas used, the higher the power generated. Conclusion: When used with a wind device, the output parameters of the convergent will result in better mechanical efficiency, which greatly improves electrical power generation.

Journal ArticleDOI
TL;DR: In this paper , a 3D-CFD simulation on the effect of various design and operating parameters, namely the number of blades, overlap ratio, spacing size, arc angle, shape factor, presence of curtain, and multi-bucket rotor, on the aerodynamic performance of a Savonius vertical axis wind turbine (VAWT) is conducted.
Abstract: In this study, a 3D-CFD simulation on the effect of various design and operating parameters, namely the number of blades, overlap ratio, spacing size, arc angle, shape factor, presence of curtain, wind velocity, and multi-bucket rotor, on the aerodynamic performance of a Savonius vertical axis wind turbine (VAWT) is conducted. In order to evaluate the effect of each parameter, the rotor’s power coefficient (Cp) for different tip speed ratio (TSR) values and overall torque as a function of the azimuth angle are investigated. The results show that the generated power of a solid rotor with more buckets is less than that of the two-bladed rotor, and by decreasing the overlap ratio and spacing size, Cp values are enhanced. Moreover, a rotor with a larger bucket arc angle has less Cp value and total torque, in addition to shape factor, which changes the configuration of the rotor by adding arms, thus enhancing the aerodynamic performance of the prototype. Furthermore, it is shown that installing a curtain in the upstream section of the rotor improves Cp value by directing airflow. Moreover, it is observed that by increasing inlet wind velocity and, subsequently, the Reynolds number, generated power is boosted. In addition, it is noted that a suitable multi-bucket rotor configuration can boost generated power. Finally, the optimum design is achieved by using the Kriging method. Based on the optimization results, a 2-bladed Savonius VAWT with an overlap ratio of 0, spacing size of 0 (m), arc angle of 170°, shape factor of 0.5, and inlet wind velocity of 12 (m/s) at TSR = 0.37 introduces the highest efficiency.

Journal ArticleDOI
16 Mar 2023-Energies
TL;DR: In this article , the authors present a review of the power and torque coefficients of various wind generation systems, which involve the real characteristics of the wind turbine as a function of the generated power.
Abstract: This paper presents a review of the power and torque coefficients of various wind generation systems, which involve the real characteristics of the wind turbine as a function of the generated power. The coefficients are described by mathematical functions that depend on the trip speed ratio and blade pitch angle of the wind turbines. These mathematical functions are based on polynomial, sinusoidal, and exponential equations. Once the mathematical functions have been described, an analysis of the grouped coefficients according to their function is performed with the purpose of considering the variations in the trip speed ratio for all the coefficients based on sinusoidal and exponential functions, and with the variations in the blade pitch angle. This analysis allows us to determine the different coefficients of power and torque used in wind generation systems, with the objective of developing algorithms for searching for the point of maximum power generated and for the active control of wind turbines with variations in the blade pitch angle.

Journal ArticleDOI
TL;DR: In this paper , the authors investigated a new combination between the Savonius and Darrieus rotors at which a two-bladed Bach-type rotor is attached inside a twobladed Darrieous rotor made by NACA 0018.
Abstract: The application of the Darrieus rotors in regions with lower wind potentials is one of the challenging issues in the operation of this type of vertical axis wind turbine (VAWT). To overcome this problem, various combinations of Darrieus and Savonius rotors, called the hybrid rotor, are proposed, which is one of the attractive subjects among wind turbine researchers. Using the computational fluid dynamics technique (CFD), this study investigates a new combination between the Savonius and Darrieus rotors at which a two-bladed Bach-type rotor is attached inside a two-bladed Darrieus rotor made by NACA 0018. In this way, various attachment angles (α) between the internal and external rotors such as 0°, 45°, and 90° are studied to find the optimal case. Computations are performed for various tip speed ratios (TSR) such as 1.5, 2.5, and 3.5, and free-wind speeds (U∞) of 5 and 10 m/s. The obtained results revealed that the application of a hybrid wind turbine is more beneficial under lower TSR and U∞ values. Additionally, it is demonstrated that the case with α = 90° is the optimal case in TSR = 1.5 and 2.5 providing a maximum 21.43% improvement in comparison to the Darrieus rotor for TSR = 1.5 and U∞ = 5 m/s.

Journal ArticleDOI
26 Feb 2023-Energies
TL;DR: In this paper , a 2D URANS (Unsteady Reynolds-Averaged Navier Stokes) numerical analysis is employed for an H-Darrieus VAWT.
Abstract: Vertical Axis Wind Turbines (VAWTs) have proven to be suitable for changing wind conditions, particularly in urban settings. In this paper, a 2D URANS (Unsteady Reynolds-Averaged Navier Stokes) numerical analysis is employed for an H-Darrieus VAWT. A turbulent domain is created through systemically randomising the inlet velocity to create macro-turbulence in front of the VAWT. The parameters for spatial and temporal randomisation of velocity and its effects on the turbine performance are studied for a mean free stream velocity, U∞ = 10 m/s, and a tip speed ratio (TSR) of 4.1. The mean Coefficient of power (Cp) for randomised fluctuation of 2 m/s and half-cycle randomisation update frequency is 0.411 and for uniform inlet velocity is 0.400. The Cp vs. Tip Speed ratio plot suggests that the optimal tip speed ratio for operation is around 4.1 for this particular wind turbine of diameter 1 m, chord 0.06 m, and NACA 0018 airfoils. The effect of randomisation for tip speed ratio λ = 2.5, 3.3, 4.1, and 5.3 on the performance of the turbine is studied. Turbine wake recovers at a faster rate for macro-turbulent conditions and is symmetric when compared to wake generated by uniform velocity inlet. The maximum velocity deficit for a distance behind the turbine, x/d = 8 at TSR (λ) = 4.1 is 46% for randomised inlet and 64% for uniform inlet. The effect of randomisation for λ = 2.5 to 5.3 on the performance of the turbine is analysed. A time-varying gust based on International Electrotechnical Commission (IEC) Extreme Operating Gust is used to study the effect of fluctuating wind conditions in a turbulent environment. Since real-time conditions often exceed gust factors mentioned by IEC, winds with large gust factors such as 1.50, 1.64, and 1.80 are analysed. With an increase in gust amplitude, Ugust = 6 m/s to Ugust = 12 m/s on a free stream velocity of U∞ = 10 m/s, the mean Cp decreases from 0.41 to 0.35 since the wind turbine operates under tip speed ratios outside optimal range due to large fluctuations in incoming velocity.

Journal ArticleDOI
26 Jun 2023-Fluids
TL;DR: In this paper , the aerodynamic characteristics of a newly designed three-bladed horizontal-axis wind turbine (HAWT) using the Computational Fluid Dynamic (CFD) method were investigated.
Abstract: The present work aims to study the aerodynamic characteristics of a newly designed three-bladed horizontal-axis wind turbine (HAWT) using the Computational Fluid Dynamic (CFD) method. The blade geometry is designed using an improved Blade Element Momentum (BEM) method to be similar in size to the Ampair300 wind turbine. The shear stress transport (SST) transition turbulence model closure is utilized to solve the steady state three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations. The Ansys Fluent CFD solver is used to solve the problem. Then, a comparison between the two turbines’ operating conditions is conducted by monitoring the pressure coefficient, pressure contours and velocity vectors at five different radial positions. The analysis of the Tip Speed Ratio (TSR) effects on the turbine efficiency and on the flow behavior on the blade and in the near wake is carried out. For 8 m/s wind speed, the optimum pitch angle is also investigated, and the results are prepared against each TSR.

Journal ArticleDOI
TL;DR: In this article , the authors compared the power performance of a horizontal axis current turbine and a turbine with two passive flow control attachments, the vortex generator, and the inserted tube, and found that including vortex generators and tubes on the turbine can help increase power production by 9.8% and 14.7%, respectively.
Abstract: Energy from river currents is one of the available renewable energy sources to produce electricity. An improvement in the efficiency of the horizontal axis current turbine is required for the successful utilization of this energy. This paper compares the power production of a horizontal axis current turbine and a turbine with two passive flow control attachments, the vortex generator, and the inserted tube. Firstly, the NACA S1210 hydrofoil shape has been selected. Then the variation of chord length and twist angle along the blade span has been determined. Finally, a 5-meter-diameter, three-bladed, horizontal-axis current turbine has been designed using the blade element momentum theory.The rotor has a maximum power coefficient and a maximum power of 0.47 and 42.71 kW, respectively, at the current speed of 2.1 m/s and a tip speed ratio of 6 when the hydrofoil with tubes has been chosen to design the horizontal axis current turbine. It has been proven that including vortex generators and tubes on the turbine can help increase power production by 9.8% and 14.7%, respectively.

Journal ArticleDOI
11 May 2023-Energies
TL;DR: In this paper , the authors developed a novel preset performance controller for a wind power system maximum power tracking control, which is based on the concept of time-varying feedback.
Abstract: The primary control goals of a wind turbine (WT) are structural load shedding, maximum wind energy capture in the underpowered situation, and consistent power production in the full power condition. A crucial component of the control problem for wind turbines with varying speeds is maximum power tracking control. Conventional maximum power tracking control tracks the ideal blade tip speed ratio to provide the most wind power at the specified wind speeds. However, because of the wind turbine’s great nonlinearity and the significant external disturbances it encounters, it is difficult to react quickly to variations in wind speed, and the tracking speed is sluggish, which lowers the amount of electricity produced annually. In light of this, this work develops a novel preset performance controller for a wind power system maximum power tracking control. With this technique, the convergence rate and tracking precision may be set. In particular, based on the concept of time-varying feedback, a time-varying function, known as the preset performance function, is first created to allow the convergence speed and accuracy to be predetermined; then this time-varying function is used to transform the actual specified time problem of the original system into a bounded time problem of the new system; finally, a direct robust controller design strategy with pre-defined performance is suggested based on the design concept of the backstepping technique. The plan may maximize the rotor power coefficient by altering the wind turbine speed, track the ideal blade tip speed ratio for a given tracking accuracy and speed, and get the most wind power to produce the most power with the strongest robustness. The simulation results show that the recommended control technique works.

Journal ArticleDOI
TL;DR: In this article , an experimental and computational analysis of a novel hybrid vertical axis wind turbine (VAWT) arrangement has been performed, and performance characteristics such as the output power, power coefficient, dynamic torque coefficient, and static torque coefficient were determined.
Abstract: In this research, an experimental and computational analysis of a novel hybrid vertical axis wind turbine (VAWT) arrangement has been performed. We suggest an innovative VAWT design that has a high power coefficient and self-starting capability. The inner side of the proposed hybrid system has been integrated with the H-rotor turbine with cambered blades, which demonstrates strong self-starting capabilities at various azimuths. Three NACA0018 airfoil blades are mounted on the outside of the proposed hybrid wind turbine, while three DU 06-W-200 airfoil blades are installed on the inside. Based on a similarity analysis, a scaled-down model was developed, and performance characteristics such as the output power, power coefficient ([Formula: see text]), dynamic torque coefficient ([Formula: see text]), and static torque coefficient ([Formula: see text]) were determined. An existing hybrid VAWT and a typical H-rotor Darrieus design were also examined for comparison. The highest [Formula: see text] for the proposed hybrid design was found to be 0.486 at a tip speed ratio (TSR) of 3, while the H-rotor Darrieus’ maximum value was 0.42 at a TSR of 2.62 and the existing hybrid VAWT’s value was 0.41 at a TSR of 2.5. Positive [Formula: see text] values at all azimuths demonstrate that the proposed hybrid wind turbine can start entirely on its own. In comparison to the existing H-rotor and hybrid VAWT, this novel hybrid system has shown enhanced performance parameters ([Formula: see text], [Formula: see text], [Formula: see text], output power) by around 11%–13% over a wide range of wind speeds.