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홍기배(K. B. Hong),김형섭(H. S. Kim),양회천(H. C. Yang),유홍선(H. S. Ryou) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
In this study, the numerical simulations of the spray characteristics within the combustion chamber of direct injection model engine are performed to examine the applicability of turbulence model. The turbulence models used are the RNG k-t model and the modified k-ε model which included the compressibility effect due to the compression/expansion of the charges. The predicted results in the quiescent condition of direct injection model engine show reasonable trends comparing with the experimental data of spray characteristics, i .e., spray tip penetration, spray tip velocity. The spray tip penetration predicted using the RNG k-t model is
[論文] 포트각도에 따른 2행정기관 실린더내의 유동장 해석
홍기배(K. B. Hong),최영진(Y. J. Choi),양희천(H. C. Yang),유홍선(H. S. Ryou),정인석(I. S. Jeung) 한국자동차공학회 1993 오토저널 Vol.15 No.1
The characteristics of the flow processes in the cylinder of the two-stroke cycle engines have become the subject of increasing interest and attention owing to the simplicity and the higher power per unit weight of the two-stroke cycle engine ‘<br/> Among the many factors which influence on the scavenging flow, the port angle is important factor. Hence, four different type models with one inlet-port and two side-ports are studied to show the effect of port angle on the laminar scavenging flow.<br/> When the inlet-port axial angle is relatively larger than the side-port axial angle, it is showed that the fresh charge penetrate into the burned gas and displace it first toward the cylinder head and then toward the exhaust port.<br/> When the inlet-port axial angle is much less than the side-port axial angle, the fresh charge through the inlet-port directly move toward the exhaust port.<br/> The result showed that the model A may suppress the generation of vortices in the vicinity of inlet and side prots which restrict the sufficient supply of fresh charge and obstruct the perfect displacement of all combustion products.
벽과 분무사이의 유동에 대한 저 Reynolds 난류모델의 비교평가
홍기배,유흥선,정남조 중앙대학교 생산공학연구소 1998 생산공학연구소 논문집 Vol.7 No.2
소형 디젤엔진의 발달에 벽과 분무액적과의 상호작용은 공기와 분사연료의 혼합뿐 아니라 연소에 큰 영향을 끼쳐왔다. 본 논문에서는 벽 부근에서 난류가 액적 거동에 미치는 영향을 분석하기 위해서 Yoshizawa의 비등방성 난류 모델과 Reynolds에 의해서 제안된 수정 k-ε 모델을 사용하였다. 또한 Fujimoto등에 의해서 측정된 실험값과 계산된 결과를 비교하였다. 비교 결과 다른 수정 k-ε모델보다 Yoshzawa의 모델이 실험값과 가장 잘 일치하였다. The spray/wall interaction is considered as one of the most important phenomena influencing air-fuel mixing and combustion in the development of compact diesel engine. In this paper we used the Yoshizawa's anisotropic turbulence model and the κ-εmodel modified by Reynolds in order to analyze the effect of turbulence on the drops behavior in the near-wall region and the calculated results are compared with the experimental data of Fujimoto et. al. It can be concluded that the calculated results by Yoshizawa's model rather than those of the modified κ-εmodel agree well the experimental data
운전상태에서의 유동장 및 분무특성에 미치는 분사압력의 영향에 대한 수치해석적 연구
최영기,유홍선,홍기배,양희천 중앙대학교 생산공학연구소 1992 생산공학연구소 논문집 Vol.1 No.1
Since the combustion in direct injection engines was strongly influenced by the characteristics of flow and spray, an understanding of the characteristics of those was essential to design of the direct injection engines. In this study the numerical analysis of the effects of injection pressure on the flow fields and the characteristics of spray in a motoring condition was performed using the spray model that could predict the interactions between spray droplets and gas fields. The governing equations were discretised by the finite volume method and the modified k- turbulence model which included the compressibility effects due to the compression/expansion of piston was used. The results showed that the radially strong inward squish flow or outward reverse-squish flow at the bowl lip was apparent due to the effect of the piston bowl. It was found that as the injection pressure increased, the evaporation rate of droplets was decreased due to the narrow width of spray and the increased number of droplets impinged on the bottom of piston bowl.
직접분사 엔진의 유동장 및 분무특성에 미치는 선회비의 영향에 대한 수치해석적 연구
김형섭,양희천,홍기배,유홍선 한국산업안전학회 1995 한국안전학회지 Vol.10 No.3
직접분사엔진에서 기상과 분무액적간의 유동특성 및 분무특성에 미치는 선회비의 영향에 대하여 수치해석하였다. 정적인 환경에서는 분무초기를 제외하고는 계산과 실험결과가 잘 일치하였다. 운전상태에서는 연료분사 기간동안 속도장의 영향이 증가하여 스쿼시유동의 중요성이 상대적으로 감소 하였다. 선회비가 증가할수록 높은 난류에너지가 연소실내에 분포되며 분무액적이 확산되고 기상과의 상호작용이 강해져서 증발률이 증가하였다. Since the rate and completeness of combustion in direct injection engines were controlled by the characteristics of gas flow fields and sprays, an understanding of those was essential to the design of the direct injection engines. In this study the numerical simulations of swirl effects on the characteristics of gas flow fields and sprays were performed using the spray model that could predict the interactions between gas fields and spray droplets. The governing equations were discretized by the finite volume method and the modified k-ε model which included the compressibility effects due to the compression/expansion of piston was used. The results of numerical calculation of the spray characteristics in the quiescent environment were compared with the experimental data. There were good agreements between the results of calculation and the experimental data, except in the early stages of spray. In the motoring condition, the results showed that a substantial air entrainment into the spray volume was emerged and hence the squish motion was relatively unimportant during fuel injection periods. As the swirl ratio increased, the evaporation rate was increased due to the wide dispersion of the spray droplets and the strong interaction between spray droplets and gas fields.