• Title/Summary/Keyword: Flamelet modeling

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Flamelet Modeling of Turbulent Nonpremixed Flames (층류화염편 모델을 이용한 난류 비예혼합 화염장 해석)

  • Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 2000.12a
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    • pp.9-16
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    • 2000
  • The flamelet concept has been widely applied to numerically simulate complex phenomena occurred in nonpremixed turbulent flames last two decades, and recently broadened successfully the applicable capabilities to various combustion problems from simple laboratory flames to gas turbine engine, diesel spray combustion and partially premixed flames. The paper is focused on brief review of recently noticeable work related to flamelet modeling, which includes Lagrangian flamelet approach, RIF concept as well as steady flamelet approach. The limitation of steady flamelet assumption, the effect of transient behavior of flamelets, and the effect of spray vaporization on PDF model have been discussed.

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Flamelet Modeling of Thrbulent Nonpremixed Flames (층류화염편 모델을 이용한 난류 비예혼합 화염장 해석)

  • Kim, Yong-Mo
    • Journal of the Korean Society of Combustion
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    • v.5 no.2
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    • pp.1-8
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    • 2000
  • The flamelet concept has been widely applied to numerically simulate complex phenomena occurred in nonpremixed turbulent flames last two decades, and recently broadened successfully the applicable capabilities to various combustion problems from simple laboratory flames to gas turbine engine, diesel spray combustion and partially premixed flames. The paper is focused on brief review of recently noticeable work related to flamelet modeling, which includes Lagrangian flamelet approach, RIF concept as well as steady flamelet approach. The limitation of steady flamelet assumption, the effect of transient behavior of flamelets, and the effect of spray vaporization on PDF model have been discussed.

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Unsteady Flamelet Modeling of Turbulent Nonpremixed Flames (비정상 층류화염편 모델을 이용한 비예혼합 난류화염 해석)

  • Kim, Seong-Ku;Kang, Sung-Mo;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 2000.05a
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    • pp.133-141
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    • 2000
  • The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The recently developed unsteady flamelet model has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations the further downstream.

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Unsteady Flamelet Modeling of Turbulent Nonpremixed Flames (비정상 층류화염편 모델을 이용한 비예혼합 난류화염 해석)

  • Kim, Seong-Ku;Kang, Sung-Mo;Seo, Bo-Sun;Kim, Yong-Mo
    • Journal of ILASS-Korea
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    • v.6 no.3
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    • pp.8-16
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    • 2001
  • The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The unsteady flamelet model recently developed has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations further downstream.

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Large Eddy Simulation of Turbulent Combustion Flow Based on 2-scaler flamelet approach

  • Oshima, Nobuyuki;Tominaga, Takuji
    • 한국전산유체공학회:학술대회논문집
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    • 2006.10a
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    • pp.18-21
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    • 2006
  • This paper investigates LES of turbulent combustion flow based on 2-scalar flamelet approach, where a G-equation and a conserved scalar equation simulate a propagation of premixed flame and a diffusion combustion process, respectively. The turbulent SGS modeling on these flamelet combustion approach is also researched. These LES models are applied to an industrial flows in a full scale gasturbine combustor with premixed and non-premixed flames. The numerical results predict the characteristics of experiment temperature profiles. Unsteady features of complex flames in combustor are also visualized.

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TRANSIENT FLAMELET MODELING FOR COMBUSTION PROCESSES OF HSDI DIESEL ENGINES

  • Kim, H.J.;Kang, S.M.;Kim, Y.M.;Lee, J.H.;Lee, J.K.
    • International Journal of Automotive Technology
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    • v.7 no.2
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    • pp.129-137
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    • 2006
  • The representative interactive flamelet(RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the HSDI diesel engine. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the eulerian particle flamelet model using the multiple flamelets has been employed. The vaporization effects on turbulence-chemistry interaction are included in the present RIF procedure. the results of numerical modeling using the rif concept are compared with experimental data and with numerical results of the widely-used ad-hoc combustion model. Numerical results indicate that the rif approach including the vaporization effect on turbulent spray combustion process successfully predicts the ignition delay characteristics as well as the pollutant formation in the HSDI diesel engines.

Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • Journal of the Korean Society of Combustion
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    • v.4 no.2
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    • pp.51-62
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    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

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Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 1999.10a
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    • pp.93-104
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    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

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Eulerian Particle Flamelet Modeling for Combustion Processes of Bluff-Body Stabilized Methanol-Air Turbulent Nonpremixed Flames

  • Kim, Seong-Ku;Kang, Sung-Mo;Kim, Yong-Mo
    • Journal of Mechanical Science and Technology
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    • v.20 no.9
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    • pp.1459-1474
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    • 2006
  • The present study is focused on the development of the RIF (Representative Interactive Flamelet) model which can overcome the shortcomings of conventional approach based on the steady flamelet library. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF model can effectively account for the detailed mechanisms of $NO_x$ formation including thermal NO path, prompt and nitrous $NO_x$ formation, and reburning process by hydrocarbon radical without any ad-hoc procedure. The flamelet time of RIFs within a stationary turbulent flame may be thought to be Lagrangian flight time. In context with the RIF approach, this study adopts the Eulerian Particle Flamelet Model (EPFM) with mutiple flamelets which can realistically account for the spatial inhomogeneity of scalar dissipation rate. In order to systematically evaluate the capability of Eulerian particle flamelet model to predict the precise flame structure and NO formation in the multi-dimensional elliptic flames, two methanol bluffbody flames with two different injection velocities are chosen as the validation cases. Numerical results suggest that the present EPFM model has the predicative capability to realistically capture the essential features of flame structure and $NO_x$ formation in the bluff-body stabilized flames.

Flamelet Modeling for Combustion Processes of Hybrid Rocket Engine (화염편 모델을 이용한 하이브리드 로켓의 연소과정 해석)

  • Lim, Jae-Bum;Kim, Yong-Mo;Yoon, Myung-Won
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.245-248
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    • 2006
  • Hybrid propulsion systems provide many advantages in terms of stable operation and safety. However, classical hybrid rocket motors have lower fuel regression rate and combustion efficiency compared to solid propellant rocket motor. Accordingly, the recent research efforts are focused on the improvement of engine efficiency and regression rate in the hybrid rocket engine. The present study has numerically investigated the combustion processes in the hybrid rocket engine. The turbulent combustion is represented by the flamelet model and Low Reynolds number $k-{\varepsilon}$ turbulent model is employed to reduce the uncertainties for convective heat transfer near solid fuel surface having strong blowing effect. Based on numerical results, the detailed discussions have been made for the effects of oxygen injection methods and oxygen injection flow rate on flame structure and regression rate in the vortex hybrid rocket engines

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