• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.343-352
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• 2016

In this study, a pre-swirl duct for the 180,000 DWT bulk carrier has been designed from a propulsion standpoint using CFD. The stern duct - designed by NMRI - was selected as the initial duct. The objective function is to minimize the value of delivered power in model scale. Design variables of the duct include duct angle, diameter, chord length, and vertical and horizontal displacements from the center. Design variables of the stators are blade number, arrangement angle, chord length, and pitch angle. A parametric design was carried out with the objective function obtained using CFD. Reynolds averaged Navier-Stokes equations have been solved; and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. MRF and sliding mesh models have been applied to simulate the actuating propeller. A self-propulsion point has been obtained from the results of towing and self-propelled computations, i.e., form factor obtained from towing computation and towing forces obtained from self-propelled computations of two propeller rotating speeds. The reduction rate of the delivered power of the improved stern duct is 2.9%, whereas that of the initial stern duct is 1.3%. The pre-swirl duct with one inner stator in upper starboard and three outer stators in portside has been designed. The delivered power due to the designed pre-swirl duct is reduced by 5.8%.

• New & Renewable Energy
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• v.5 no.3
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• pp.4-12
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• 2009

The effect of change in DFIG (doubly-fed wind power generator) rotating speed and active power on the grid was analyzed to understand the characteristics of wind power using the wind power simulator connected to the grid at Gochang Power Quality Test Center. Electric power quality improvement devices (DVR, STATCOM, SSTS) and electric power quality disturbance application devices for 22.9 kV grid are equipped at Gochang Power Quality Test Center. Induction motor and VVVF inverter were used to emulate the blade of a wind power generator, and a simulator for Cage wound induction generator and DFIG was developed. The trial line were assumed to be 20 km and 40 km in length, and variable wind speed pattern was set using wind speed data from Ducjeokdo to verify the power characteristics of the wind power generator according to rotating speed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.137-143
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• 2017

An axial fan has competitive advantages that can make air flow more straight and longer and produce larger air volume than the other kinds of fans. In those reasons, axial fans are widely used for ventilator, 4D cinema, duct, and so on. But, as it was designed and manufactured without any mathematical analysis or computer simulations, it is difficult to develop the performance of axial fans. Actually the axial fan is designed and manufactured in industry by imitation or traditional method. Flow velocity and volume of axial fan are changed by pitch angle, frame, the number of blade, camber angle, and chord length. In this paper, the performance of axial fan was analyzed and by computer program known as CFD. Finally, we have designed a new axial fan whose velocity and volume is improved. The performance of new axial fan is also compared with the of conventional fans experimentally.

• Journal of Engineering Education Research
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• v.13 no.5
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• pp.8-14
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• 2010

This study intends to study about the blade performance loss occurred due to the variation in the shape of an airfoil from attachment/non-attachment of an erosion shield for the hovercraft. The model in this study has used NACA44XXseries, has designed NACA44XX-series by using the Auto CAD, and it designed the shape that has attached an erosion shield to this model according to the thickness and length. By using these models, a grid was generated by GAMBIT and the lift coefficient ($C_l$) and the drag coefficient ($C_d$) were calculated FLUENT code for flow analysis. Through this, the $C_l$ and $C_d$ have calculated and compared the lift-to-drag ratio that an indicator of airfoil performance according to the shape and attachment/non-attachment of erosion shield.

• The KSFM Journal of Fluid Machinery
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• v.14 no.1
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• pp.48-54
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• 2011

The effect of channel cutback on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-to-chord ratio of $h_{st}/c$ = 5.51% and h/c = 2.0% respectively. The cutback length-to-camber ratio is changed to be $CB/c_c$ = 0.0, 0.1, 0.2 and 0.3. The results show that longer cutback delivers not only stronger secondary flow but also higher aerodynamic loss in the tip leakage vortex region, meanwhile it leads to lower aerodynamic loss in the passage vortex region. The discharge of cavity fluid through the cutback opening provides a beneficial effect in the reduction of aerodynamic loss, whereas there also exists a side effect of aerodynamic loss increase due to local wider tip gap near the trailing edge. With increasing $CB/c_c$ from 0.0 to 0.3, the aerodynamic loss coefficient mass-averaged all over the measurement plane tends to increase slightly.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.64.2-64.2
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• 2011

해상용(offshore) 부이(bouy)는 선박의 항로를 지시하거나 암초, 침몰선 등 항해상의 위험물을 알리기 위해 사용 되며, 야간을 위해 등화장치를 설치한 것을 등부표라 한다. 등부표는 야간 점등을 위해 자체 전력 생산시스템을 갖추고 있으나, 기존의 태양광을 이용한 전력 시스템은 해상 환경에 따른 제약이 많아 안정적인 운영이 어려우므로 풍력 발전기(wind turbine)를 이용한 하이브리드 전력 생산시스템으로의 전환이 필요한 실정이다. 선행 연구는 수직축(vertical axis) 양력(lift) 및 항력(drag) 조합형 해상용 풍력발전기 개발에 대하여 수행하였으나, 본 논문에서는 풍력발전기의 효율 증대를 위해 날개 길이 및 후면부 절개 비율에 따른 수직축 풍력발전기 특성에 대하여 연구하였다. 풍력발전기의 설치조건은 선행연구와 동일하게 등명구 교체 작업을 원활하게 하기 위하여 설치 공간을 $1m{\times}1m$로 제한하였으며, 등부표의 구조를 고려하여 최상단에 지지 프레임을 별도로 구성 하였다. 풍력발전기의 블레이드는 0.6mm의 알루미늄 박판을 절곡하여 NACA 4418의 외형을 가지도록 제작하였고, 블레이드 설계 시 에어포일의 후면부를 절개하여 양력과 항력을 효과적으로 이용하며 저속과 고속에서 높은 효율을 가지도록 설계하였다. 또한 블레이드 날개 길이와 후면부 절개 비율에 따른 풍력발전기 특성을 실험을 통해 비교하여 기준 해상 풍속에서 블레이드 설계 최적화를 수행하였으며 비교 모델 대비 약32% 발전량이 증가한 설계변수 조합을 구하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.687-696
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• 2005

Acoustic power spectrum of the upstream and downstream sound field due to an isotropic frozen turbulent gust impinging on a cascade of flat plate airfoils are computed by using a analytic formulation derived from Smith's method, and Whitehead's LINSUB codes. A parametric study of the effects on sound power of the number of blades and turbulence length scale is performed with an emphasis on analyzing the characteristics of sound power spectrum. Through the comparison of the computed results of sound power, it is found that acoustic power spectrum from the 2-D cascade subject to a ingested turbulence can be categorized into two distinct regions. one is lower frequency region where some spectral components of turbulence do not contribute to the cut-on acoustic modes and therefore the effect of the cascade geometry is more dominant ; the other is higher frequency region where all of spectral components of turbulence make contributions to cut-on acoustic modes and thus acoustic power is approximately proportional to the blade number.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.686-695
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• 1993

A flywheel-type, inclined axis chopper for small-area rice and livestock farmers, has been developed at IRRI Agricultural Engineering, The prototype is belt-driven by a 2.6kW engine and uses four angled blades rotating below a fixed counteredge. Manual feeding is facilitated by a convenient spout presenting the crop to the inclined blade housing and also suction created by the rotating blades . The distance between the rotating blades and the bottom of the housing determines the length of chops, set here for 25 cm. The unit would cost $200 without the engine. Tests with napier grass, corn stalks , and rice straw showed satisfactory performance within the acceptable clearance, speed and moisture content ranges of the material presented. Highest capacities were 1186, 1148 and 744kg/hr for napier grass, corn stalks and rice straw, respectively. Corn stalks required the highest power demand at 2.3kW engine would be adequate as power source. The chopper performance was comparable to higher cost commercial chippers in terms of capacity and specific energy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.141-144
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• 2006

In this study, we developed a decladding device which separates 250 mm length of simulated nuclear spent fuel rod into the pallets and the pieces of the hulls after inserting the rod cut into the module with several pairs of blades. To improve the performance of the equipment, we considered some mechanisms to prevent the rod cut from being exposed or bounced into the hot-cell, to reduce the operation time, and to insert the rods automatically. It is expected that the newly developed system will contribute to prevent radioactive pollution in the hot-cell, reduce the operation time, and to increase the safety of the operators. As a result of the performance test for some mockup fuel rod cuts in the ACP(Advanced Spent Fuel Control Process) facility, it was verified that the decladding device could be applied to the actual fuel rod cut. And it will be able to use for a scale-up facility in the future.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.194-199
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• 2003

Developed m this research is a production information system for marie propellers. The paper deals with surface modeling and tool path generation modules of the system. Since the input point data may have some errors, the data is examined using the 2nd divided difference. The point data is interpolated to a $G^2$ chord-length spline surface with some end-conditions. The effects of the various end-conditions on the interpolated surface are discussed in the paper. The tool paths for blade, fillet, and boss of the propeller are generated. Some illustrative examples from an industry are presented.