• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1322-1325
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• 2009

The impeller and vane diffuser for the mixed flow pump(NS550) was designed by using meridional selection program and inverse design method. We decided the meridional shape of the impeller from the meridional design parameter, such as the specific speed and maximum diameter at the impeller exit. The meridional shape of vane diffuser was set from the impeller shape, distribution of cross sectional area and maximum diffuser diameter. The angle of impeller blade and diffuser vane was designed by using inverse design method. The predicted overall performance by using commercial CFD code(ANSYS CFX-11) shown good agreement with design goals.

• 대한토목학회논문집
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• 제12권4호
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• pp.59-70
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• 1992

풍하중(風荷重)을 받는 쌍곡 냉각탑의 비탄성(非彈性), 비선형(非線型) 극한(極限) 거동(擧動)을 Cray Y-MP 슈퍼 컴퓨터에 개발(開發)한 유한요소(有限要素)컴퓨터 프로그램으로 연구(研究)하였다. 유한요소 망(mesh)을 각각 잘게 잘라서 3모델을 만들고, 이 모델들을 이용하여 탄성과 비탄성 해석으로 유한요소 망의 수렴관계(mesh convergence)를 연구하였다. 연구결과 유한요소의 크기가 냉각탑의 극한거동을 예측하는데 매우 중요한 역할을 하고있음을 볼 수 있었다. 비록 쌍곡 냉각탑이 풍하중(風荷重)에 대해서 막응력(膜應力)(membrane stress)으로 저항하나, 본 연구(研究) 결과(結果) 휨응력(應力)(bending stress)도 냉각탑의 파괴와 거동(擧動)에 매우 중요한 역할을 하고 있음을 알아 내었다. 해석(解析)한 냉각탑은 형성값(Shape factor)이 1.48에 이르렀고, 이는 냉각탑의 자오선 응력(meridional stress)이 원둘레방향으로 상당히 재분배 되고 있음을 보여주는 것이다. 이러한 재분배에 대한 사실은 배치된 철근의 항복이 바람방향 자오선으로부터 $30^{\circ}C$에 까지 나타난 것으로 더욱더 뚜렷하였다. 현재의 탄성해석을 이용하는 냉각탑 설계(設計) 방법은 안전(安全)측에 있음을 보여 주었으며, 1보다 큰 형상값을 설계시에 활용하기 위해서는 더욱더 많은 연구가 선행되어야 할 것이다.

• 한국유체기계학회 논문집
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• 제12권3호
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• pp.7-12
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• 2009

In this paper, shape optimization based on three-dimensional flow analysis has been performed for impeller design of centrifugal compressor. To evaluate the objective function of an isentropic efficiency, Reynolds-averaged Navier-Stokes equations are solved with SST (Shear Stress Transport) turbulence model. The governing equations are discretized by finite volume approximations. The optimization techniques based on the radial basis neural network method are used for the optimization. Latin hypercube sampling as design of experiments is used to generate thirty design points within design space. Sequential quadratic programming is used to search the optimal point based on the radial basis neural network model. Four geometrical variables concerning impeller shape are selected as design variables. The results show that the isentropic efficiency is enhanced effectively from the shape optimization by the radial basis neural network method.

• Animal Systematics, Evolution and Diversity
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• 제33권4호
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• pp.246-255
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• 2017

Three freshwater ciliates, Lembadion lucens (Maskell, 1887) Kahl, 1931, L. bullinum ($M{\ddot{u}}ller$, 1786) Perty, 1849, and L. magnum (Stokes, 1887) Kahl, 1931, belonging to the genus Lembadion Perty, 1849 are newly reported from Korea with detailed descriptions and illustrations based on live observation and protargol impregnation. Lembadion lucens is characterized by following characteristics: $52-91{\times}33-64{\mu}m$ body size in vivo; ovoid and slightly asymmetric body shape; 27-49 somatic kineties; and 55-80% of whole pellicle covered with meridional lines with rectangular meshes in posterior portion. Lembadion bullinum is distinguishable from its congeners by its body size of $110-130{\times}60-73{\mu}m$ in vivo; ovoid body shape; oral aperture occupying about four-fifths of ventral side; 48-55 somatic ciliary rows; meridional lines with rectangular meshes except anterior portion (about 16% of body) on pellicle. Lembadion magnum is also characterized by its body size of $70-90{\times}37-50{\mu}m$ in vivo; obliquely asymmetric anterior end of body; oral aperture occupying about more than four-fifths of ventral surface, and opened longitudinally entire ventral surface; 45-61 somatic ciliary rows; meridional lines without rectangular meshes on whole pellicle of body. The present study is the first description of the genus Lembadion from Korea.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.172-178
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• 2009

This paper reports on an investigation (using RSM with commercial CFD software) of the performance characteristics of the impeller in a centrifugal pump. Geometric parameters of vane plane development were defined with the meridional shape and frontal view of the impeller. The parameters are focused on the blade-angle distributions through the impeller in a fixed meridional geometry. For screening, a $2^k$ factorial design has been used to identify the important design parameters. The objective functions are defined as the total head rise and the total efficiency at the design flow-rate. From the $2^k$ factorial design results, it is found that the incidence angles and the exit blade angle are the most important parameters influencing the performance of the pump.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1303-1308
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• 2008

This paper presents effects of impeller geometrical parameters on the performance of a centrifugal pump impeller. The effects of meridional parameters and vane plane development parameters on the performance of the impeller were numerically studied using a commercial CFD code and DOE(design of experiments) software. Geometrical parameters in a method of meridional view and vane plane development were selected and defined to generate the 3D impeller shape. The response variables are defined in a total head and efficiency curve with flow rate. The influences of selected design variables on the various objective functions were examined as a result of the calculation using 2k factorial.

• 한국유체기계학회 논문집
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• 제10권4호
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• pp.29-38
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• 2007

In this study, flow structure in a two-stage centrifugal compressor for a turbo-chiller with the refrigerant, R134a, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller, diffuser and return channel were analyzed in detail including velocity vector, secondary flow, Mach number and pressure contours in blade spanwise and meridional plane for each stage. The estimation on the one-dimensional output from the preliminary design and three-dimensional shape of the impeller blade and the meridional shape of the return channel were performed through the flow analysis, while some numerical schemes and techniques including Multiple Frames of Reference technique, real gas property data and inlet boundary condition changes, which were used in CFD, were compared with their features. The results will be used as reference data for a new design of 3-D impeller shape to improve R134a compressor performance.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.14-24
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• 2011

In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied using a commercial computational fluid dynamics (CFD) code and DOE (design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser. Geometric design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffusers. The vane plane development was controlled using the blade-angle in a fixed meridional shape. First, the design optimization of the defined impeller geometric variables was achieved, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Next, design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed using $2^k$ factorial designs, and the design optimization of the geometric variables was determined using the response surface method (RSM). The objective functions were defined as the total head and the total efficiency at the design flow rate. Based on the comparison of CFD results between the optimized pump and base design models, the reason for the performance improvement was discussed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 하계학술발표대회 논문집
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• pp.6-6
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• 2007

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.530-536
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• 2016

The number of fabrication shop for spherical type LNG tank is proportional to that of the tank radius to be constructed. Due to limitation of facility investment including building sites, it is practically difficult to fabricate various size tanks with perfectly spherical shape in the yards. The efficient method to be capable of increasing cargo tank volume is to extend vertically the conventional spherical type LNG tank by inserting a cylindrical shell structure. The main purpose of this study is to derive related equations on forces generated on spherical type LNG tank with central cylindrical part under various static loadings in order to establish the simplified analysis method for the initial estimate. In this study, equations on circumferential and meridional force have been derived and verified by relations with the reaction forces per unit length of equator.