• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.78-84
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• 2013

The objective of this paper is to develop 360 W class wind turbine tree using a helical type wind turbine. The performance of 100 W class helical wind turbine which finished the conceptual design has been forecast through the CFD analysis. After performed the analysis of one wind turbine performance, four wind turbine have been installed at the structure of a tree type and then the change of a output data has been verified through the CFD analysis. In this study, the CFD results of a helical wind turbine tree have been shown by a velocity and pressure distribution. The result could obtain more than rated power 360 W through the CFD analysis.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.59-65
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• 2020

Vertical axis wind energy systems including 3 and 4 blades are numerically investigated in a two-dimensional (2D) computational domain. The power coefficient (C_p) is adopted to measure the efficiency of the system and the effect of the rotating velocity on the power coefficient is analyzed for the two different systems. The rotating velocity varies from 30 rad/s to 90 rad/s, which corresponds to the tip speed ratio (T.S.R) of 0.5 to 1.5. The torque exerted on the blades is mainly determined by the aerodynamic force in the x-direction and maximized when the blade is positioned at around θ = 186°. The efficiency of the 4-blade system is higher than that of the 3-blade system within the tip speed ratio range between 0.5 and 0.67, besides where the 3-blade system shows a better performance. For the 3-blade system, the maximum efficiency is reached to 0.082 at the tip speed ratio of 1.083. The maximum efficiency of the 4-blade system is 0.071 at T.S.R. = 0.92. The velocity fields in the x-direction, pressure fields, and the vorticity magnitude are analyzed in detail for the optimal cases of the 3- and 4-blades systems, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.399-406
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• 2016

The large scale wind turbine blades usually experience periodic change of inflow speed due to blade rotation inside the ground shear flow region. Because of the vertical wind shear, the inflow velocity in the boundary layer region is maximum at uppermost position and minimum at lowermost position. These spatial distribution of wind speeds can lead to the periodic oscillation of the 6-component loads at hub and low speed shaft of the wind turbine rotor. In this study we compare the aerodynamic loads between two inflow conditions, i.e, uniform flow (no vertical wind shear effect) and normal wind profile. From the computed results all of the relative errors for oscillating amplitudes increased due to the ground shear flow effect. Especially bending moment and thrust at hub, and bending moments at LSS increased enormously. It turns out that the aerodynamic analysis including the ground shear flow effect must be considered for fatigue analysis.

• The KSFM Journal of Fluid Machinery
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• v.19 no.4
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• pp.43-47
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• 2016

Vertical axis wind turbine, despite of its limit in power efficiency, the simplicity in structure and maintenance is a competitive factor that keeps this type of turbine in the game until nowadays. Continuous solutions have been given to handle its major weakness and the use of omni-directional guide vane is an considerable one. In this paper, a 5kkW scale Savonius-based wind turbine enhanced with such guide vane system was design and studied. Together with reasonable blade design, the wind turbine shows promising performance compared with basic design while maintaining its original advantages.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.166-171
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• 2013

In this study, low noise designs of a Savonius wind turbines are numerically investigated. From a previous study, it was found that the high harmonic components whose fundamental frequency is higher than the BPF were found to be dominant in noise spectrum of a Savonius wind turbine. On a basis of this observation, S-shaped blade tip is proposed as a low design factors that decrease wind turbine noise by inducing phase differences in vortex shedding. The conventional Savonius and S-shaped turbines are investigated using Hybrid CAA method where flow field around the turbine are computed using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Noise reductions by these design factors are confirmed by comparing the predicted noise levels from these turbines.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1203-1204
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• 2010

• Wind and Structures
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• v.22 no.5
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• pp.595-616
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• 2016

Providing high starting torque and efficiency simultaneously is a significant challenge for vertical axis wind turbines (VAWTs). In this paper, a new approach is studied in order to modify VAWTs performance and cogging torque. In this approach, J-shaped profiles are exploited in the structure of blades by means of eliminating the pressure side of airfoil from the maximum thickness toward the trailing edge. This new profile is a new type of VAWT airfoil using the lift and drag forces, thereby yielding a better performance at low TSRs. To simulate the fluid flow of the VAWT along with J-shaped profiles originated from NACA0018 and NACA0030, a two-dimensional computational analysis is conducted. The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the two-equation Shear Stress Transport (SST) turbulence model. The main objective of the study is to investigate the effects of J-shaped straight blade thickness on the performance characteristics of VAWT. The results obtained indicate that opting for the higher thickness in J-shaped profiles for the blade sections leads the performance and cogging torque of VAWT to enhance dramatically.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.269-274
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• 2014

In this study, low noise designs for a Savonius wind turbine were numerically investigated. As was reported in our previous study, the harmonic components with a fundamental frequency higher than the BPF were identified as being dominant in the noise spectrum of a Savonius wind turbine, and these components were a result of vortex shedding. On a basis of this observation, an S-shaped blade tip is proposed as a means of reducing the noise generated by small vertical(Savonius) wind turbines. This blade induces phase differences in the shedding vortices from the blades, and thus reduces the noise from the wind turbine. The aerodynamic noise characteristics of the conventional and "S-shaped" Savonius turbines were investigated by using the Hybrid CAA method where the flow field around the turbine is computed using the CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow field data. The degree of noise reduction resulting from the proposed design and its reduction mechanism were confirmed by comparing the predicted noise spectrum of these turbines and the flow characteristics around them.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.241-245
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• 2018

This paper designed the main blade in V-shape and tried to identify the best design conditions by changing the main blade angle and wind speed. When the main blade open angle was maintained at $120^{\circ}$ and the sample2 with an angle changed by $30^{\circ}$ was compared with the sample3 changed by $60^{\circ}$, the power output of sample2 was 3.8[kW], the power coefficient was 0.12, and the power output of sample3 was 6.0[kW], the power coefficient was measured as 0.18. So the power output of sample 3 was 58% higher than that of sample2, and the power coefficient was increased by 50%. The power coefficient was 0.18 and the wind speed was changed to 10[m/s] at 6.0[kW] at wind speed of 7[m/s] by fixing main blade open angle of $120^{\circ}$ and angle of $60^{\circ}$. The output was measured at 7.7[kW] and the power coefficient at 0.23. When the wind speed was high, the power output increased by 28% and the power coefficient increased by 83%. Also, sample4 was 103% higher in output and 92% more in efficiency than sample2.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.230-231
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• 2003

Two and three-dimensional flows around a cross-flow wind turbine are investigated by the numerical simulation. The turbine studied in this paper has cylindrical shape with many small blades along its periphery. Incompressible Navier-Stokes equation is used for this simulation. A rotating coordinate system, which rotates at the same speed of the turbine, is used in order to simplify the boundary conditions on the blades of the turbine. Additionally, a boundary fitted coordinate system is employed in order to express the shape of the blades precisely. A third order upwind scheme is chosen for the approximation of the non-linear terms. When the number of blades is about 10, the highest torque is obtained.