• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1765-1772
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• 2006

High-pressure die casting such as thixocasting and rheocasting is an effective process in the manufacturing automotive parts. Following the recent trend in the automotive manufacturing technologies, the product design subject to the die casting becomes more and more complex. Simultaneously the injection speed is also designed to be very high to establish a short cycletime. Thus, the requirement of the die design becomes more demanding than ever before. In some cases the product's shape can have multiple slender manifolds. In such cases, design of the inlet and outlet parts of the die is very important in the whole manufacturing process. The main issues required for the qualified products are to attain gentle and uniform flow of the molten liquid within the passages of the die. To satisfy such issues, the inlet cylinder ('bed cylinder' in this paper) must be as large as possible and simultaneously the outlet opening at the end of each passage must be as small as possible. However these in turn obviously bring additional manufacturing costs caused by re-melting of the bed cylinder and increased power due to the small outlet-openings. The purpose of this paper is to develop effective simulation methods of calculation for fluid flows in multiple columns, which mimic the actual complex design, and to get some useful information which can give some contributions to the die-casting industry. We have used a commercial code CFX in the numerical simulation. The primary parameter involved is the size of the bed cylinder. We will show how the very small opening of the outlet can be treated with the aid of the porous model provided in the code. To check the validity of the numerical results we have also conducted a simple experiment by using water.

• 한국유체기계학회 논문집
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• 제14권2호
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• pp.47-51
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• 2011

This paper describes the shape optimization of a blower impeller used for a refuse collection system. Two design variables, which are used to define the blade angles of an impeller, are introduced to increase the blower performance. A blower efficiency is selected as an object function, and the shape optimization of the blade angles is performed by a response surface method (RSM). Three-dimensional Navier-Stokes equations are introduced to analyze the internal flow of the blower and to find the value of object function for the training data. Relatively good agreement between experimental measurements and numerical simulation is obtained in the present study. Throughout the shape optimization, blower efficiency for the optimal blade angles is successfully increased up to 3.6% compared with that of reference at the design flow rate. Detailed flow field inside the turbo blower is also analyzed and discussed.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.59-66
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• 2013

Lack of the space in many diesel vehicles make it difficult to design and install the catalytic muffler to reduce emissions. For this reason, inlet part of the catalytic muffler is made of L-type which has lower flow uniformity than conventional I-type, and catalytic muffler has complex internal structure by various insertions, which affect the flow uniformity and pressure drop of the systems. In this work, the flow characteristics such as flow uniformity and pressure drop have been numerically investigated by changing such various geometries as inlet shape, porosity, and outlet shape inside the muffler with the three-dimensional turbulent incompressible flow solver. Total 4 different cases are considered in order to find optimal configurations of the catalytic muffler in view of high flow uniformity and low pressure drop. The results show that Case 2 which has no induction cone and outlet perforated pipe has higher uniformity index and lower pressure drop than others considered in this work.

• 한국분무공학회지
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• 제24권3호
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• pp.105-113
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• 2019

In this paper, a study of Urea-SCR System for Dosing Injector for responding to enhanced environmental regulations has been conducted. There is a limit to the experimental approach due to the structural characteristics of the injector. In order to overcome this problem, The analysis was performed assuming unsteady turbulent flow through computational fluid analysis and the internal flow characteristics of the injector were analyzed. By changing the nozzle shape of the injector, the performance factors of the swirl injector by shape were selected and compared. The design parameters were modified by changing the diameter of the nozzle at a constant ratio compared to the base model. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. The Conv. model to which the taper was applied showed the dominance in mass flow rate, discharge coefficient and swirl because of the smooth fluid flow by shape. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. As a result of the comparison coefficient derivation with those performance parameters for comparing the performance of the model-specific injector, the Conv-140 model with the nozzle diameter expanded by 140% showed the best value of the comparison coefficient.

• 대한기계학회논문집B
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• 제28권3호
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• pp.296-303
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• 2004

The heat and flow characteristics in a single-phase parallel-flow heat exchanger was examined numerically to obtain its optimal shape. A response surface method was introduced to approximately predict its performance with respect to the design parameters over the design domain. The inflow/outflow angle of the working fluid, the location of inlet/outlet, the protruding height of flat tube and the height of header were chosen as a design parameter The evaluation of the relative importance of the design parameters was performed based on a sensitivity analysis. An efficiency index was used as an evaluation characteristics value to simultaneously consider both the heat transfer and the pressure drop. The efficiency index of the optimum model, compared to that of the base model, was increased by 9.3%.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.187-194
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• 2010

Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• 한국전산유체공학회지
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• 제15권3호
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• pp.16-23
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• 2010

Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• 한국소음진동공학회논문집
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• 제23권4호
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• pp.372-378
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• 2013

An acoustical shape optimization problem is formulated for optimal design of a perforated reactive muffler with offset inlet/outlet. The mean transmission loss value in a target frequency range is maximized for an allowed pressure drop value between an inlet and an outlet. Partitions in the chamber are divided into several sub-partitions, whose lengths are selected as design variables. Each sub-partition has the same number of holes, whose sizes are equal. A finite element model is employed for acoustical and flow analyses. A gradient-based optimization algorithm is used to obtain an optimal muffler. The acoustical and fluidic characteristics of the optimal muffler are compared with those of a reference muffler. Validation experiment is carried out to support the effectiveness of our suggested method.

• 한국대기환경학회지
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• 제16권2호
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• pp.129-140
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• 2000

Simulation study has been carried out to analyze the air flow supplying from the heat pump system inside the tollgate booth by using the Phoenix computer simulation program. Through this simulation analysis we can find the problem of present tollgate booth in terms of air flow and recommend an improved model also simulate this model. Final results as follows; It was turned out that the fresh air conditioning is not provided to the worker effectively due to the improper location of inlet and outlet in the present tollgate booth in addition to that the air curtain system applied in the booth lowered air circulation from outside. The improved model was suggested first to increase the air curtain effect by downsizing the window and by installation of the air curtain suction line to reduce the induced outdoor air second to supply the fresh air to the worker directly by relocation of the inlet and outlet of supplying air. With these improved modifications better results have been reached in terms of air flow inside the booth. Next through the air flow simulation of outside booth the contaminated outdoor air has been easuily infiltrating into the booth through the window because of its rectangle shape. Stream like shape of booth has been proposed through the computer simulation as an alternative shape of tollgate booth for a new design.

• 한국기계기술학회지
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• 제13권3호
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• pp.49-55
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• 2011

For the purpose of the enhancement of the air conditioner performance and fuel effciency, several cases of centrifugal impeller for passenger car air conditioner have been numerically analyzed by changing central angle of blades and length of outlet for shape optimization of the impeller. Commercial CFD program Fluent 6.3.26 has been used to compute velocity, temperature, pressure and turbulence intensity that can lead numerous results. The central angles of two blades and three cases of outlet length led 4~12% and 3.5~6.4% differences of velocity and flow rate, respectively. The velocity distribution near the blade surface was axisymmetric and had a maximum value of 22.19 m/s and velocity of the vertical direction of the impeller showed linear increase with horizontal direction. At case 3 of oultet length, there existed a a minimum pressure value of -133320 Pa.