• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.269-273
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• 2011

본 논문에서는 대향류 매니폴드의 면적비에 따른 튜브형 열교환기에서의 압력강하와 유량 균일도를 분석하기위해 전산해석을 수행하였다. 유동 분배와 압력손실 특성은 입-출구 면적비에 따라 영향을 받는다. 본 연구에서, 최적의 입-출구 면적비를 선택함으로서 튜브형 열교환기의 유동 불균일도 최소와 향상된 압력손실 특성을 얻을 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.121-124
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• 2008

본 논문에서 연료 과농 가스발생기의 동적 연소 특성을 수록하였다. 연소실과 추진제 매니폴드 내에서 발생하는 압력 섭동을 계측하여 데이터 분석을 실시하였다. 단독 연소 시험에서는 연소압에 관계없이 연소가 안정적으로 이루어졌으나 터빈 매니폴드 장착의 경우, 산소 임계 압력에 해당하는 50 bar이하의 저압 조건에서 저주파 연소 불안정이 발생하는 것을 확인하였다. 이는 연소실 특성 길이 증가에 의한 축방향 연소 불안정으로 여겨지며, 연소압 증가에 따라 압력 섭동이 증가함을 확인하였다.

• 한국기계가공학회지
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• 제6권1호
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• pp.50-56
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• 2007

Exhaust manifold is generally subjected to thermal cycle loadings ; at hot condition, large compressive plastic deformations are generated, and at cold condition, tensile stresses are remained in highly deformed critical zones. These phenomena originate from the fact that thermal expansions of the runners are restricted by inlet flange clamped to the cylinder head, because the former is less stiff than the latter and, the temperature of the inlet flange is lower than that of the runners. Since the failure of an exhaust manifold is mainly caused by geometric constraints between the cylinder head and the manifold, the thermal stress can be controlled by geometric factors. The generic geometric factors include the inter distance (2R), the distance from the head to the outlet (L), the tube diameter(d) and the tube thickness (t). This criteria based on elastic analysis up to onset of yield apparently indicate that the pre-stress also reduces the factor; however, high temperature relaxation may reduce this effect at later operation stage.

• 한국수소및신에너지학회논문집
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• 제24권5호
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• pp.386-392
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• 2013

Polymer electrolyte membrane (PEM) fuel cell stacks are constructed by stacking several to hundreds of unit cells depending on their power outputs required. Fuel and oxidant are distributed to each cell of a stack through so-called manifolds during its operation. In designing a stack, if the manifold sizes are too small, the fuel and oxidant would be maldistributed among the cells. On the contrary, the volume of the stack would be too large if the manifolds are oversized. In this study, we present a three-dimensional computational fluid dynamics (CFD) model with a geometrically simplified flow-field to optimize the size of the manifolds of a stack. The flow-field of the stack was simplified as a straight channel filled with porous media to reduce the number of computational meshes required for CFD simulations. Using the CFD model, we determined the size of the oxidant manifold of a 30 kW-class PEM fuel cell stack that comprises 99 cells. The stack with the optimal manifold size showed a quite uniform distribution of the cell voltages across the entire cells.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.23-28
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• 2014

This study investigates fluid flow and thermal stress at automotive exhaust manifolds as model 1 and 2. The maximum displacements happen at joint part connected with 4 pipes and upper middle of both parts in cases of model 1 and 2 respectively. At inner surface of the part connected with engine, maximum equivalent stresses of 991.85 and 698.96 MPa are shown in cases of model 1 and 2 respectively. As maximum velocities at the outlet at model 1 are shown at 19.46 and 14.61 m/s in cases of model 1 and 2 respectively, model 1 has more pressure drop than model 2. As result, model 2 has less pressure drop than 1. Model 2 has less deformation and stress than model 1. Model 2 has also less pressure drop than model 1. Therefore model 2 has more strength durability than model 1. This study result is applied with the design of safe automotive manifold and it can be useful to improve the durability by predicting prevention against the deformation due to exhaust gas.

• 대한조선학회논문집
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• 제55권2호
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• pp.161-168
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• 2018

This paper presents the design procedure of the suction bucket used to support a subsea manifold. The soil-suction bucket interaction numerical analysis technique was verified by comparing the present results with a reference data. In order to simulate the soil-bucket interaction analyses of a subsea manifold structure, various material data such as undrained shear strength, elastic modulus, and poisson ratio of soft clay in Gulf of Mexico were collected from reference survey. We proposed vertical and horizontal design loads based on system weights and current-induced drag forces. Under the assumption that diameter of the suction bucket was 3.0 m considering real dimension of the subsea manifold frame structures, aspect ratio was decided to be 3.0 based on reference survey. The ultimate bearing load components were determined using tangent intersection method. It was proved that the two design load components were less than ultimate bearing loads.

• 한국유체기계학회 논문집
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• 제15권5호
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• pp.11-19
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• 2012

The main function of fuel cell manifold is to render reactants distribution as uniform as possible into a fuel cell stack. The purpose of this study is to numerically investigate the effects of stack manifold design on reactants distribution within a fuel cell stack. Four manifold designs with different manifold entrance shapes (expansion or diffuser) and different values of the extra width between the cell outer channel and manifold side wall are considered and applied to the fuel cell stack consisting of 50 cells. Since the fuel cell stack geometry involves several millions of grid points for numerical calculations, a parallel computing methodology is employed to substantially reduce the computational time and overcome the memory requirement. The numerical simulations are carried out and calculated results clearly demonstrate that both the manifold entrance shape and extra width have a substantial influence on manifold performance, controlling the degree of flow separation and entrance length for fully developed flow in the manifold channel. Finally, we suggest the optimum design of fuel cell manifold based on the simulation results.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2000년도 추계학술대회 학술발표 논문집
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• pp.195-198
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• 2000

Sliding mode control method is popularly used for robustness to distrurbance and variance of systems internal parameter. However, one of the serious problem of this method is Chattering which occurs in neighborhood of sliding manifold. Another problem is that we cannot expect robustness before system starts sliding mode. A new tuning method of sliding manifold which changes the parameter of sliding manifold dynamically using Wavelet Neural Network is proposed in this paper. We can expect the better performance in sliding mode control by the wavelet neural networks excellent property of approximating arbitrary function for multi-resolution analysis and decrease chattering drastically.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 하계종합학술발표회논문초록집
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• pp.304-304
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• 2004

• 대한기계학회논문집B
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• 제28권9호
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• pp.1133-1138
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• 2004

Shape optimization method was coupled with a conventional CFD analysis to find the optimal shape of ex-manifold diffuser which decreases the maldistribution of flow above the catalyst. Shape optimization results show that flow uniformity above the catalyst was increased about 28% fur the axi-symmetric case and about 18% for the asymmetric case. The axi-symmetric type can be applied to the diffuser of under floor catalyst and the asymmetric type can be applied to the diffuser of close coupled catalyst.