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벽면조건에 의한 미소관내 화염 전파 특성 변화에 관한 수치해석
김남일(Nam Il Kim),카오루 마루타(Kaoru Maruta) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
A premixed flame propagating in a tube suffers strong variation in its shape and structure depending on boundary conditions. The effects of thermal boundary conditions and flow fields on flame propagation are numerically investigated. Navier-Stokes equations and species equations are solved with a one-step irreversible global reaction model of methane-air mixture. Finite volume method using an adaptive grid method is applied to investigate the flame structure. In the case of an adiabatic wall, friction force on the wall significantly affected the flame structure while in the case of an isothermal wall, local quenching near the wall dominated flame shapes and propagation. In both cases, variations of flow fields occurred not only in the near field of the flame but also within the flame itself, which affected propagation velocities. This study provides an overview of the characteristics of flames in small tubes at a steady state.
이대근(Dae Keun Lee),마루타 카오루(Kaoru Maruta) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
Flame propagation characteristics in a meso-scale cylindrical tube, of which diameter is comparable to the classical quenching diameter, was theoretically analyzed. One-dimensional planar flame approximation in a uniform gas flow was used to simplify the analysis, and gas and wall temperatures are also assumed to be a function of only the axial position. The large activation energy asymptotics was used to determine mass burning rate and propagation velocity of the flame. As a result, various flame propagation behaviors, different to those from the classical theory, were predicted. Intense flame-wall interaction exist only for slow moving condition, otherwise the flame behaves almost like a freely propagating nonadiabatic flame. Such interaction can make the flame superadiabatic and also provide an additional stable branch from the classical unstable lower branch. Heat recirculation from the exhaust gas through the wall is positive for such slow moving flame, but it is negative for other flames. It has its maximum value at the blowout point of normal flame on the slow moving branch and at the upper extinction point of sub-limit flame. It is also found that, for a given internal heat convection parameter, the transition velocities between neighboring normal flame branches and the maximum mass burning rate are determined by only one dimensionless parameter, respectively
Swiss-roll 마이크로 연소기 개발과 스케일 효과
김남일(NAM IL KIM),사토시 아이즈미(SATOSHI AIZUMI),카오루 마루타(KAORU MARUTA) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The configuration of Swiss-roll was adopted as a promising structure for the development of sub millimeters scale combustors. In this study, the scaling effects are investigated both experimentally and analytically. A simple one-dimensional analytical model was constructed to interpret the combustion characteristics of the Swiss-roll combustors. Two energy equations for combustor body and mixture, along with species equations employing two-step global reaction model were solved. In spite of the simplicity of the present model, important characteristics of the combustors such as upper and lower flammability limits, effect of cap thickness on flammability limits were predicted well. This study shows that the effects of design parameters are important in the practical development of smaller combustors.