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정수진(S.J.Jeong),김우승(W.S.Kim) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_1
A numerical and experimental study of three-dimensional steady incompressible non-reacting flow inside various dual-monolith catalytic converters was studied for achievement of performance improvement, reduction of light-off time and longer service life by improving the flow uniformity within the monolith. In this study, the effects of curvature of inlet exhaust pipe and monolith brick length on the flow uniformity and pressure drop within monolith were numerically investigated. The computations are confirmed by measurements of steady flow. The result of this study shows that curvature of inlet exhaust pipe and monolith brick length have a great effect on the flow uniformity and the shorter the brick length, the lower flow uniformity and the less pressure drop. The agreement between computation and experiment was relatively good, so it was confirmed that CFD can be used as an alternative way to analyze flow characteristics within catalytic converter for optimization design.<br/>
터널 내주행 중 발생하는 차량의 공력학적 간섭효과에 관한 수치해석적 연구
정수진(S.J.Jeong),이재진(J.J.Lee),장성국(S.K.Jang) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_2
A numerical study of the aerodynamic interference between road vehicles overtaking process was performed. A simplified vehicle-like body was employed. Steady state calculation was followed. The purpose of this paper is to clarify the effect of wake structure behind the road vehicle and its aerodynamic characteristics at overtaking in tunnels. Regarding the computational method, a Navier-Stokes solver employing k-ε RNG turbulent model with upwind difference scheme was applied. The Cd and Cp on both sides of each vehicle at overtaking was calculated, and it was found that drag coefficient increased abruptly and the wake pattern changed drastically in the process of overtaking.
촉매변환기를 포함한 배기계의 3차원 비정상 유독특성 해석
정수진(S.J.Jeong) 한국자동차공학회 1996 한국자동차공학회 학술강연초록집 Vol.1996 No.10
A theoretical study of three-dimensional unsteady compressible non-reacting flow inside a pair of dual-monolith catalytic converters which attatched to 6-cylinder engine and has two Y type junctions at inlet is studied for the achievement of performance improvements,reduction of light-off time,and longer service life by improving the flow distribution of perturbating exhaust gases. One dimensional non-steady gas dynamic calculation was also performed using method of characteristics in intake & exhaust system to obtain the boundary conditions to the 3-dimensional unsteady analysis. Studies indicate that unsteady representation is necessary because perturbation of gas velocity may affect gas flow uniformity on the surface of monolith. And simulation results show that the level of gas flow maldistribution in the monolith depends on interference at junctions due to the mass flow from the individual cylinders overlap in time, curvature and angle of separation streamline of exhaust pipes
6기통 가솔린 엔진에 장착된 촉매변환기 내의 3차원 비정상 유동특성 해석
정수진(S.J.Jeong),김우승(W.S.Kim) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_1
A theoretical study of three-dimensional unsteady compressible non-reacting flow inside double flow of monolith catalytic converter system attached to 6-cylinder engine was performed for the achievement of performance improvement, reduction of light-off time, and longer service life by improving the flow distribution of pulsating exhaust gases. CFD method was used to evaluate the differences between unsteady and steady-state flow.<br/> To obtain the boundary conditions to CFD analysis, one dimensional non-steady gas dynamic calculation was also performed by using the method of characteristics in intake and exhaust system. Studies indicate that unsteady representation is necessary because pulsation of gas velocity may affect gas flow uniformity within the monolith. The simulation results also show that the level of flow maldistribution in the monolith heavily depends on curvature and angles of separation streamline of mixing pipe that homogenizes the exhaust gas from individual cylinders. It also found that on dual flow converter systems, there is severe interactions of each pulsating exhaust gas flow and the length of mixing pipe and junction geometry influence greatly on the degree of flow distribution.<br/>
자동차의 촉매변환기 내의 열 및 변환특성에 관한 수치해석적 연구
정수진(S.J.Jeong),김우승(W.S.Kim) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_1
This work attempts a systematic investigation of the effects of flow maldistribution on the light-off behavior of monolithic catalytic converter. To achieve this goal, a three-dimensional computational fluid dynamic modeling with a chemical reaction model has been developed for analysis of transient temperature and concentration distribution by including the turbulent flow effect in inlet cone and exhaust pipes with varying cross-sectional area ratios of inlet exhaust pipe and monolithic brick. The computational results reveal that the influence of area ratio was significant during high flow transient condition, and the cross-sectional area ratio with a smaller value increases thermal gradient due to flow maldistribution in the monolith, finally degrades performance of catalytic converter. High velocities locally concentrated leaves large portion of monolith remain cold and CO,HC unconverted during warm-up period. Hence, flow maldistribution may cause a significant retardation of the light-off and eventually worsen the conversion efficiency.<br/>