• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.371-379
• /
• 2000

A noise prediction method of axial flow fan is developed by incorporating through-flow method and vortex shedding noise model. Fan noise is assumed to be generated due to the pressure fluctuation induced by wake vortices of fan blades and radiate as diploe distribution. The wake vortices are analyzed by combining Karman vortex street model and through-flow analysis results, and the vortex-induced fluctuating pressure on blade surface is calculated by thin airfoil theory. The predicted sound pressure levels and directivity patterns of fan noise by the present method are favorably compared with fan noise test data. Furthermore, the present method is shown to be very useful for predicting the aero-acoustic performance map of the fan operated at off-design point.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.5
• /
• pp.42-47
• /
• 2012

Newly updated wing shape to apply small vertical wind turbine is tested with digital wind tunnel in this study. Digital wind tunnel is designed to reduce length of wind tunnel and also to maximize its area of test section. Same DC fans of ninety six are installed in the end side of its rectangular duct and air can be blown out to the other side to have uniform flow with same electricity power. New wing is concluded using experimental plan and analysis with 4-parameters and 3-levels, and tested with digital wind tunnel. It shows better performance in lift to drag ratio, and can applied to the wind turbine for the higher torque and lower thrust.

• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.520-525
• /
• 2003

A numerical investigation was performed to determine the effect of airfoil on the optimum flap height using NACA0015 Wells turbine. The five double flaps which have 0.5% chord height difference were selected. A Wavier-Stokes code, CFX-TASCflow, was used to calculate the flow field of the Wells turbine. The basic feature of the Wells turbine is that even though the cyclic airflow produces oscillating axial forces on the airfoil blades, the tangential force on the rotor is always in the same direction. Geometry used to define the 3-D numerical grid is based upon that of an experimental test rig. This paper tries to analyze the optimum double flap of Wells turbine with the numerical analysis.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.2
• /
• pp.311-324
• /
• 2015

This study presents computational analyses for low-drag aerodynamic design that are applied to modify a long-endurance UAV. EAV-2 is a test-bed for a hybrid electric power system (fuel cell and solar cell) that was developed by the Korean Aerospace Research Institute (KARI) for use in future long-endurance UAVs. The computational investigation focuses on designing a wing with a reduced drag since this is the main contributor of the aerodynamic drag. The airfoil and wing aspect ratio of the least drag are defined, the fuselage configuration is modified, and raked wingtips are implemented to further reduce the profile and induced drag of EAV-2. The results indicate that the total drag was reduced by 54% relative to EAV-1, which was a small-sized version that was previously developed. In addition, static stabilities can be achieved in the longitudinal and lateral-directional by this low-drag configuration. A long-endurance flight test of 22 hours proves that the low-drag design for EAV-2 is effective and that the average power consumption is lower than the objective cruise powerof 200 Watts.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.6
• /
• pp.13-20
• /
• 2014

It is necessary to design a compressor with high pressure ratio that satisfies the IMO(international maritime organization) NOx emission regulation for the marine diesel engine. Impeller was designed using the modified slip factor with the flow coefficient. The main purpose of this study is to investigate the sensitivity of the compressor performance by the vaned diffuser geometries. The first vaned diffuser type was based on a NACA airfoil, the second was channel diffuser, and the third was conformally transformated configuration of a NACA65(4A10)06 airfoil. The sensitivity of the performance was calculated using a commercial CFD program for three different diffuser geometries. The channel diffuser showed the wide range of operation and higher pressure characteristics, comparing with the others. This is attributed to the flow stability at diffuser. Combined with this results with impeller design, the optimized compressor was designed and verified by the test results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.12
• /
• pp.9-17
• /
• 2006

An experimental study was carried out to examine the behavior of the unsteady boundary layer. An NACA 0012 airfoil with aspect ratio of 2.7 was set vertically in a test section, which is sinusoidally pitched about the quarter chord. The oscillating amplitude is from -6$^{\circ}$ to +6$^{\circ}$ and the mean angle of attack is 0$^{\circ}$. Surface mounted probes (Glue-on probes) were employed to measure the surface flow of the boundary layer. Measurements were made at free-stream velocities of 1.98, 2.83, and 4.03m/s, and the corresponding Reynolds numbers based on the chord length were 2.3$\times$104, 3.3$\times$104 and 4.8$\times$104, respectively. The reduced frequency is fixed as 0.1 in all cases. The results show that the surface position of minimum shear stress and of boundary layer break-down can be discerned in the Reynolds number between 2.3$\times$104 and 3.3$\times$104.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.6
• /
• pp.693-701
• /
• 2012

In this study, a small wind turbine airfoil specialized for national wind condition was designed in order to develop the furling control type HAWT. And then a flow analysis was carried out based on the blade drawing which was designed to characterize of the developed airfoil. The result of the flow analysis showed that the torque on the 3 blades was 180.23N.m. This is equivalent to an output power of 5.66kw and an output efficiency of 0.44. Then we produced and constructed a 3kW - furling control type HAWT by getting the system unit design technology such as the specialized furling control device. By operating this turbine, we could get 3kW of the rated power at a wind speed of 10.5m/s through the ability test. Cut-in wind speed was 2m/s, generator efficiency was 92% at the rated power output. Sound power level was 87.2dB(A). Also we observed that the output power was limited to 10.5m/s with furling system operation.

• Aerospace Engineering and Technology
• /
• v.9 no.1
• /
• pp.78-83
• /
• 2010

In the present paper, a flap was optimized to maximize the lift. A 2-element fowler flap system was utilized for optimization with an initial shape of general aviation airfoil and a flap shape designed by Wentz. Response surface method and Hicks-Henne shape function were implemented for optimization. 2-D Navier-Stokes method was used to solve flow field around aGA(W)-1 airfoil with a fowler flap. Commercial programs including Visual-Doc, Gambit/Tgridand Fluent were used. Upper surface shape and the flap gap were optimized and lift for landing condition was improved considerably. The original and optimized flaps were tested in the KARI's 1-m low speed wind tunnel to examine changes in aerodynamic characteristics. For optimized flap tests, the similar trend to prediction could be seen but stall angle of attack was lower than what was expected. Also, less gap than optimized design delayed stall and produced better lift characteristics. This is believed to be the effect of turbulence model.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.328-331
• /
• 2008

For the purpose of verifying the calculation, the rotor blade shall be subjected to test for the natural frequencies and the static loading within the scope of the assessment. This paper presents a full scale static test procedure of the rotor blade for certification by GL. This blade model is manes as KM24 designed for IEC type IA. The test and calculation values are all most similar. Also there is not founded any marks of cracks or buckling at the shell, and bonding area is T/E, L/E and shear web. Therefore, the test is successful and the rotor blade is satisfied the safety requirement at the maximum design load.

• The KSFM Journal of Fluid Machinery
• /
• v.3 no.3 s.8
• /
• pp.31-40
• /
• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.