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디젤 분무와 천연 가스 분류의 거동 특성에 관한 기초 연구
염정국(J. K. Yeom),김민철(M. C. Kim) 한국동력기계공학회 2009 동력시스템공학회지 Vol.13 No.6
This basic study is required to examine spray or jet behavior depending on fuel phase. In this study, analyses of diesel fuel(n-Tridecane, C13H28) spray and natural gas fuel(Methane, CH4) jet under high temperature and pressure are performed by a general-purpose program, ANSYS CFX release 11.0, and the results of these are compared with experimental results of diesel fuel spray using the exciplex fluorescence method. The simulation results of diesel spray is analyzed by using the combination of Large-Eddy Simulation(LES) and Lagrangian Particle Tracking(LPT) and of a natural gas jet is analyzed by using Multi-Component Model(MCM). There are two study variables considered, that is, ambient pressure and injection pressure. In a macroscopic analysis, the higher ambient pressure is, the shorter spray or jet tip penetration is at each time after start of injection. And the higher injection pressure is, the longer spray or jet tip penetration is at each time after start of injection. When liquid fuel is injected, droplets of the fuel need some time to evaporate. However, when natural gas fuel is injected, the fuel does not need time to evaporate. Gas fuel consists of minute particles. Therefore, the gas fuel is mixed with the ambient gas more quickly at the initial time of injection than the liquid fuel is done. The experimental results also validate the usefulness of this analysis.
김민철(M. C. Kim),이성원(S. W. Lee),전만수(M. S. Joun) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this paper, a ductile fracture approach to predicting the piercing stage of the automatic multi-stage cold forging processes are studied with emphasis on fracture prediction and automatic simulation of consecutive stages of multi-stage forging processes. The normalized Cockcroft-Latham damage model is employed to predict the fracture and a smoothing scheme to clear the fracture surface is proposed for easy simulation of the consecutive stages. The approach is applied to five-stage cold forging processes and the predictions are compared with the predictions of a simple approach as well as the experiments.
김민철(M. C. Kim),엄재근(J. GL Eom),임성주(S. J. Lim),최호준(H. J. Choi),전만수(M. S. Joun) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
In this paper, a new approach to finite element analysis of a swaging process is presented. An analysis model is presented with emphasis on the pusher that imposes the back pressure to keep the workpiece from slipping along the die-workpiece interface especially when the inclined dies are utilized. The rigid-plastic finite element method is employed. The approach is applied to simulate a tube swaging process and its results are compared with the predictions, revealing that they are in close agreement with each other.
김민철(M. C. Kim),김봉수(B. S. Kim),장성민(S. M. Jang),문호근(H. K. Moon),조광제(K. J. Cho),전만수(M. S. Joun) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
Experimental and numerical study is conducted to establish application-oriented approach to predicting the engineering dimensions of drawn pipe with large diameters. Rigid-plastic finite element analysis is applied to predict the plastic deformation using rigid-dies and die stress vectors on the die-material interface. Die structural analysis is then conducted using the die stress vectors to predict the final dimensions of the drawn pipe. The approach is applied to a drawing process of the pipe with large inner and outer diameter. The predictions are compared with experiments and a meaningful agreement has been achieved.