scholarly journals Performance Analysis of a Helical Savonius Rotor with Shaft at 45° Twist Angle Using CFD

2013 ◽  
Vol 3 (1) ◽  
pp. 118 ◽  
Author(s):  
Rajat Gupta ◽  
Bachu Deb ◽  
R. D. Misra
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Twist Angle ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Complete Cycle ◽  
Tip Speed Ratio ◽  
Savonius Rotor ◽  
Rotor Angle

Helical Savonius rotor is considered to be superior to conventional Savonius rotor in terms of higher power coefficient (Cp) and better starting characteristic. However studies related to helical Savonius rotors is few. In view of this, in this paper, the performance of a helical Savonius rotor with shaft at 45° bucket twist angle for one complete cycle of rotation was analyzed using Computational Fluid Dynamics. A two-bucket helical Savonius rotor with shaft was designed using GAMBIT, having a height of 60 cm and diameter of 17 cm with 45° bucket twist angle. A three dimensional Computational Fluid Dynamics analysis using Fluent package was done to predict the performance of the rotor. Standard k-? turbulence model with second order upwind discretization scheme and standard wall condition was used. Grid independence test was also conducted to have the best meshing accuracy. Power coefficients (Cp) of the rotor at different tip speed ratios were evaluated for rotor angle variation from 0° to 180°. Cp at each rotor angle increased with increase of tip speed ratio up to an optimum tip speed ratio, but then decreased even if tip speed ratio was further increased. Moreover, the effect of rotor angle on Cp in a complete cycle of rotation was analyzed. Cp was found to be positive at all rotor angles, and higher values of Cp were obtained at rotor angles namely 45°, 90°, 225° and 270°, which would contribute maximum power production by the rotor. In addition to these, flow physics of the rotor was studied using tangential velocity plots w.r.t. rotor angle and path lines across the rotor. It was found that at 45°, 90° and 135° rotor angles, maximum concentration of the path lines near the tip of the blades in the upstream and downstream side of the rotor had occurred, which would be responsible for generation of maximum power coefficient in its clockwise rotation.

scholarly journals PERFORMANCE ANALYSIS OF A HELICAL SAVONIUS ROTOR WITHOUT SHAFT AT 45° TWIST ANGLE USING CFD

2013 ◽  
pp. 126-133 ◽  
Author(s):  
Bachu Deb ◽  
Rajat Gupta ◽  
R.D. Misra
Keyword(s):  
Twist Angle ◽  
Three Dimensional ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Complete Cycle ◽  
Tip Speed Ratio ◽  
Savonius Rotor ◽  
Velocity Magnitude ◽  
Computational Fluid Dynamics Analysis ◽  
Upwind Discretization

Helical Savonius rotor exhibits better performance characteristics at all the rotor angles compared to conventional Savonius rotor. However studies related to the performance measurement and flow physics of such rotor are very scarce. Keeping this in view, in this paper, a three dimensional Computational Fluid Dynamics analysis using commercial Fluent 6.2 software was done to predict the performance of a two-bucket helical Savonius rotor without shaft and with end plates in a complete cycle of rotation. A two-bucket helical Savonius rotor having height of 60 cm and diameter of 17 cm with 45° bucket twist angle was designed using Gambit. The buckets were connected at the top and bottom circular end plates, which are 1.1 times the rotor diameter. The k-ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp) and torque coefficients (Ct) at different tip speed ratios were evaluated at different rotor angles. From the investigation, it was observed that power coefficient increased with increase of tip speed ratio up to an optimum limit, but then decreased even further tip speed ratio was increased. Further investigation was done on the variations of Cp & Ct in a complete cycle of rotation from 0° to 360° in a step of 45° rotor corresponding to the optimum tip speed ratio. The value of Cp at all the rotor angles is positive. Moreover, velocity magnitude contours were analyzed for each rotor angle and it could be concluded that high aerodynamic torque and power can be expected when the rotor is positioned at 45º & 90º with respect to incoming flow.

scholarly journals Performance Prediction and Validation of a Small-Capacity Twisted Savonius Wind Turbine

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1721 ◽  
Author(s):  
Hyeonmu Jang ◽  
Insu Paek ◽  
Seungjoo Kim ◽  
Deockjin Jeong
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Performance Test ◽  
Cfd Simulation ◽  
Power Production ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Simulation Results

In this study, an off-grid–type small wind turbine for street lighting was designed and analyzed. Its performance was predicted using a computational fluid dynamics model. The proposed wind turbine has two blades with a radius of 0.29 m and a height of 1.30 m. Ansys Fluent, a commercial computational fluid dynamics solver, was used to predict the performance, and the k-omega SST model was used as the turbulence model. The simulation result revealed a tip-speed ratio of 0.54 with a maximum power coefficient, or an aerodynamic rotor efficiency of 0.17. A wind turbine was installed at a measurement site to validate the simulation, and a performance test was used to measure the power production. To compare the simulation results obtained from the CFD simulation with the measured electrical power performance, the efficiencies of the generator and the controller were measured using a motor-generator testbed. Also, the control strategy of the controller was found from the field test and applied to the simulation results. Comparing the results of the numerical simulation with the experiment, the maximum power-production error at the same wind speed was found to be 4.32%.

Improving the Energy Conversion Efficiency of a Savonius Rotor Using Automatic Valves

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
M. Amiri ◽  
M. Anbarsooz
Keyword(s):  
Low Power ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Energy Conversion Efficiency ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Savonius Rotor ◽  
Rotor Axis

Savonius wind turbines are popular for their easy fabrication and high starting capabilities. Nevertheless, they suffer from low power coefficients, which are mainly due to a negative torque resulting from the blade moving against the upcoming wind. Numerous methods have been proposed to alleviate the negative torque, among them are modified blade profiles (twisted blades), adding flow deflectors, and valve-aided blades. In this study, the effects of adding automatic valves to a two-bladed Savonius rotor on its energy conversion efficiency are investigated numerically and experimentally. The valves are placed at three different positions: close to the rotor axis, at the blade center, and at the tip of the rotor. Results show that although adding valves can decrease the negative torque of the returning blade, they can also lead to a considerable reduction in the positive torque of the advancing blade. For the rotors in the current study, the maximum power coefficient is increased 20.8% when the valves are at the tip of the blades, while the two other cases have decreased the power coefficient of the rotor. Adding the valves to the blades does not change the tip speed ratio corresponding to the maximum power coefficient of the rotor.

Performance of Double Blade Savonius Rotor at Low Rotational Speed

2020 ◽  
Vol 17 (2) ◽  
pp. 729-735 ◽  
Author(s):  
Mohanad Al-Ghriybah ◽  
Mohd Fadhli Zulkafli ◽  
Djamal Hissein Didane ◽  
Sofian Mohd
Keyword(s):  
Turbulence Model ◽  
Rotational Speed ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Savonius Rotor ◽  
Maximum Improvement ◽  
Torque Coefficient ◽  
Better Than

The performance of the single and double blade Savonius rotors are numerically analyzed using the K-ε/realizable turbulence model. The computations are implemented at different values of tipspeed ratio from 0.2 to 0.4 with a step of 0.05. Both rotors have the same dimensions with an external overlap between their blades equals 0.02 m. The results indicate that the double blade rotor performs better than the single blade rotor in terms of power coefficient. In addition, the torque coefficient is improved at all tested values of tip-speed ratio. Furthermore, the results of the simulation show that the maximum power coefficient was 0.163 at tip-speed ratio = 0.4 for the double blade rotor, whereas the maximum improvement of the double blade rotor occurs at tipspeed ratio = 0.2 with a percentage of 11.86% compared to the single blade rotor. Moreover, the highest value of the torque coefficient was 0.524 at tip-speed ratio = 0.2 for the double blade rotor.

Study on Performance and Flow Condition of a Cross-Flow Wind Turbine With a Symmetrical Casing

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Junichiro Fukutomi ◽  
Toru Shigemitsu ◽  
Hiroki Daito
Keyword(s):  
Wind Turbine ◽  
Rotational Speed ◽  
Flow Condition ◽  
Cross Flow ◽  
Low Noise ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
The Cross

A cross-flow wind turbine has a high torque coefficient at a low tip speed ratio. Therefore, it is a good candidate for use as a self-starting turbine. Furthermore, it has low noise and excellent stability; therefore, it has attracted attention from the viewpoint of applications as a small wind turbine for an urban district. However, its maximum power coefficient is extremely low (10%) as compared to that of other small wind turbines. Prevailing winds in two directions often blow in urban and coastal regions. Therefore, in order to improve the performance and the flow condition of the cross-flow rotor, a casing suitable for this sort of prevailing wind conditions is designed in this research and the effect of the casing is investigated by experimental and numerical analysis. In the experiment, a wind tunnel with a square discharge is used and main flow velocity is set as 20 m/s. A torque meter, a rotational speed pickup, and a motor are assembled with the same axis as the test wind turbine and the tip speed ratio is changeable by a rotational speed controller. The casing is set around the cross-flow rotor and flow distribution at the rotor inlet and the outlet is measured by a one-hole pitot tube. The maximum power coefficient is obtained as Cpmax = 0.19 with the casing, however Cpmax = 0.098 without the casing. It is clear that the inlet and the outlet flow condition is improved by the casing. In the present paper, in order to improve the performance of a cross-flow wind turbine, a symmetrical casing suitable for prevailing winds in two directions is proposed. Then, the performance and the internal flow condition of the cross-flow wind turbine with the casing are clarified. Furthermore, the influence of the symmetrical casing on performance is discussed and the relation between the flow condition and performance is considered.

A Study on Performance of New Tidal Energy Converter for Tidal Current Extraction Using Computational Fluid Dynamics

2016 ◽  
Author(s):  
Manh Hung Nguyen ◽  
Haechang Jeong ◽  
Changjo Yang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Tidal Current ◽  
Tidal Energy ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Energy Converter ◽  
Double Row ◽  
Tidal Turbines ◽  
Stage Of Development

Renewal energy technologies are increasingly popular to ensure future energy sustainability and to balance environmental issues. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The energy available in tidal currents or other artificial water channels is being considered as viable source of renewable power. Hydrokinetic conversion systems, albeit mostly at its early stage of development, may appear suitable in harnessing energy from such renewable resources. A concept of tidal energy converter (TEC) which is based on shape of the conventional water wheels, is introduced in this study. Basically, this turbine has several special features that are potentially more advantageous than the conventional tidal turbines, such as propeller type tidal turbines. The research aims to study the possibility of twelve-blade turbine in extracting the hydrokinetic energy of tidal current and converting it into electricity, and evaluate the performance of the turbine at different given arrangements of blades (single and double rows) using Computational Fluid Dynamics (CFD). In all cases of tip-speed ratio (TSR), the twelve-blade double-row type obtains higher power efficiency, especially about 20% power coefficient at TSR = 0.75, in comparison with 13% power coefficient of the single-row one. Furthermore, by changing the arrangement of rotating blades, the torque’s absorption from the rotor shaft of twelve-blade double-row turbine is more uniform due to the less interrupted and fluctuated generation of force for a period of time (one revolution of the rotor).

scholarly journals STATORS USE INFLUENCE ON THE PERFORMANCE OF A SAVONIUS WIND ROTOR USING COMPUTATIONAL FLUID DYNAMICS

2011 ◽  
Vol 10 (1-2) ◽  
pp. 63
Author(s):  
J. V. Akwa ◽  
A. P. Petry
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Cylindrical Shape ◽  
Tip Speed Ratio ◽  
Eddy Viscosity Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Moment ◽  
Volume Method

This paper aims at verifying the influence of using five kinds of stators in the averaged moment and power coefficients of a Savonius wind rotor using computational fluid dynamics (CFD). The analyzed stators have cylindrical shape with two and three openings, one and four deflector blades and walls shaped like a wings. The equations of continuity, Reynolds Averaged Navier-Stokes – RANS and the Eddy Viscosity Model k-ω SST, in its Low-Reynolds approaches, with hybrid near wall treatment; are numerically solved using the commercial software Star-CCM+, based on Finite Volume Method, resulting in the fields of pressure and velocity of the flow and the forces acting on the rotor buckets. The moment and power coefficients are achieved through integration of forces coming from the effects of pressure and viscosity of the wind on the buckets device. The influence of the stators use in the moment and power coefficients is checked by changing the geometry of the device for each simulations series, keeping the Reynolds number based on rotor diameter equal to 433,500. The obtained values for averaged moment and power coefficients indicate that for each type of stator used, there was maximum performance for a given tip speed ratio of rotor. Improvement in performance over the operation without stator was obtained only to the operations using stator with four deflector blades and to the stator with cylindrical shape with three openings. The improvement percentage in performance obtained for the best condition (use of four deflector blades at tip speed ratio equal to 1) is 12% compared to the performance of the rotor operating without stator.

Numerical Simulation on 2D Savonius Rotor in Ground Effect

2014 ◽  
Vol 953-954 ◽  
pp. 424-427
Author(s):  
Jian Yong Zhu ◽  
Kai Wang ◽  
Hai Bin Ruan
Keyword(s):  
Numerical Simulation ◽  
Power Output ◽  
Ground Effect ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Savonius Rotor ◽  
Calculation Results ◽  
Torque Values

The Aerodynamic Performance of 2D Savonius Rotor in Ground Effect is Numerically Simulated through Solving Unsteady Compressible RANS Equations and the Standard k-ε Turbulence Model. the Calculation Results Indicate that the Ground Effect Influences the Starting Performance and the Power Output. the Optimal Height between the Ground to the Lowest Part of the Rotor is 0.4 Times Rotation Diameter, at which the Starting Performance is Optimal. the Ground Effect also Increases the Power Coefficient and the Tip Speed Ratio Corresponding to the Maximum Power Coefficient. when Determining the Rated Tip Speed Ratio, the Fluctuation of the Torque Values and the Power Coefficient with Different Tip Speed Ratio should be Synthesized.

scholarly journals The effect of using winglets to enhance the performance of swept blades of a horizontal axis wind turbine

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987831 ◽  
Author(s):  
Mohamed G Khalafallah ◽  
Abdelnaby M Ahmed ◽  
Mohamed K Emam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Twist Angle ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Cfd Modeling ◽  
Speed Ratio ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine

One of the recent methods to improve the performance of horizontal axis wind turbine is to attach a winglet at the tip of the blade of these turbines. Winglets reduce the effect of vortex flow at the blade tip and thus improve the performance of the blade. This article presents a parametric study using the computational fluid dynamics (CFD) modeling to investigate the capability of a winglet to increase the turbine power of swept blades as well as straight blades of a horizontal axis wind turbine. The effects of winglet direction, cant angle, and twist angle are studied for two winglet orientations: upstream and downstream directions. The numerical simulation was performed using ANSYS Fluent computational fluid dynamics code. A three-dimensional computational domain, cylindrical rotationally periodic, was used in the computations. The k-ω shear-stress transport turbulence model was adopted to demonstrate turbulence in the flow. Results show that horizontal axis wind turbine with winglet and sweep could enhance more power compared to their equivalent straight or swept blade. The best improvement in the coefficient of power is 4.39% at design tip speed ratio. This is achieved for downstream swept blades with winglets pointing in the upstream direction and having cant and twist angles of 40° and 10°, respectively.

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