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한인석(Insuk Han),허강열(Kang-Yul Huh) 한국연소학회 2007 한국연소학회지 Vol.12 No.2
Flame surface area is a critical parameter determining turbulent flame speed. Three-dimensional direct numerical simulations(DNS) were conducted to figure out the evolution process of flame surface area. Fully compressible Navier-Stokes equations are solved to reproduce premixed flame embedded in isotropic decaying turbulent flow. The tangential straining and curvature of propagating surface affect development of flame area. In this study, four different turbulent intensity flows and three different Le number flames are investigated to force changes in straining and curvature effects. Consistent results are obtained for the probability density functions (PDF) of strain and curvature with previous researches. It is revealed that displacement speed, which is a speed of flame surface relative to unburnt flow, controls the balance between sink and source of flame surface area.
공기 연소와 CO₂ 재순환에 의한 순산소 연소의 난류 화염 특성 비교
이승환(Seung-Hwan Lee),허강열(Kang-Yul Huh) 한국연소학회 2008 KOSCOSYMPOSIUM논문집 Vol.- No.-
To compare air combustion and oxy combustion, SLFM calcuation was done. Then, the firtst-order conditional moment closure (CMC) model is applied to SANDIA PILOTED FLAMES D. The flow and mixing fields are calculated by fast chemistry assumption with SLFM library and a beta function pdf for mixture fraction. Chemical kinetic mechanism was GRI Mech 3.0. Oxy-combustion is stabler than air combustion. More oxygen in oxidant results in stabler flame, higher temperature, higher mass fraction of CO and OH. More CO₂ recirculation rate causes more heat loss due to radiation. CMC model gives more accurate results than SLFM model.
한인석(Insuk Han),허강열(Kang-Yul Huh) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
Flame surface area is a critical parameter determining turbulent flame speed. Three-dimensionaldirect numerical simulations(DNS) were conducted to figure out the evolution process of flame surface area. Fully compressible Navier-Stokes equations are solved to reproduce premixed flame embedded in isotropic decaying turbulent flow. The tangential straining and curvature of propagating surface affect development of flame area. In this study, four different turbulent intensity flows and three different Le number flames are investigated to force changes in straining and curvature effects. Consistent results are obtained for the probability density functions (PDF) of strain and curvature with previous researches. It is revealed that displacement speed, which is a speed of flame surface relative to unbumt flow, controls the balance between sink and source of flame surface area.
FIRE Code를 사용한 정적연소기의 메탄-공기 균질 혼합기 연소특성 연구
이석영(Suk-Young Lee),허강열(Kang-Yul Huh) 한국연소학회 2006 한국연소학회지 Vol.11 No.2
A constant volume combustion chamber was used to investigate the combustion characteristics of homogeneous charge of methane-air mixture under various initial pressure, equivalence ratio and ignition times. The constant volume combustion chamber(CVCC) mostly has been studied by the experiments of visualization until now. So it is needed the numerical analysis of fluid and combustion characteristics in chamber by the more detail simulation. In this paper, the numerical analysis is tried to approach basically the homogeneous charge combustion phenomena under the various conditions, and the combustion phenomena in chamber is numerically analyzed by the commercial FIRE code. As a results, the combustion phenomena which were mean temperature, OH radical and reaction rate in chamber were investigated and it showed that the smallest flame growth occurs for the lean state and the increase of initial charged pressure condition due to the reduced OH radical.
가스터빈 모사 연소기에서 선회 확산 화염의 연소특성 해석
정대로(Dae-Ro Joung),허강열(Kang-Yul Huh) 한국연소학회 2007 KOSCOSYMPOSIUM논문집 Vol.- No.-
The firtst-order conditional moment closure (CMC) model is applied to CH4/air swirl diffusion flame in a gas turbine model combustor. The flow and mixing fields are calculated by fast chemistry assumption with SLFM library and a beta function pdf for mixture fraction. RNG k-e model is used to consider the swirl flame in a confined wall. Reacting scalar fields are calculated by elliptic CMC formulation with chemical kinetic mechanism, GRI Mech 3.0. Validation is done against measurement data for mean flow and scalar fields in the model combustor [1]. Results show reasonable agreement with the mean mixture fraction and its variance, while temperature is overpredicted as the level of local extinction increases. The second-order CMC model is needed to consider local extinction with considerable conditional fluctuations near the nozzle.
직접 수치 해법을 이용한 난류 예혼합 연소의 화염 면적 밀도 연구
한인석(Insuk Han),허강열(Kang Yul Huh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
One of the difficulties in modeling turbulent premixed flame is that the reaction progress variable is not a conserved scalar as the mixture fraction in non-premixed flame. DNS has been a useful tool to extract critical information not easily available from measurements for modeling. In previous work it was shown that the maximum flame surface density is one of the critical parameters to determine turbulent burning velocity. In this study parametric investigation is performed to find the effects of turbulent intensity, integral length scale and laminar flame speed on the maximum flame surface density. Turbulent premixed flames have been reproduced in this study by three-dimensional direct numerical simulation (DNS) with inflow/outflow boundary condition to get a flame brush in a statistically steady state. Fully compressible Navier-Stokes equations are solved with single step chemistry. Initial and inflow turbulence are assumed to be homogeneous and isotropic.