• 한국연소학회지
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• 제4권2호
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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.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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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.

• 한국분무공학회지
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• 제5권4호
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• pp.66-71
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• 2000

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in the high-pressure engine conditions. The high-pressure vaporization model is developed to realistically simulate the spray dynamics and vaporization characteristics in high-pressure and high-temperature environment. The interaction between chemistry and turbulence is treated by employing the Representative Interactive Flamelet (RIF) Model. The detailed chemistry of 114 elementary steps and 44 chemical species is adopted for the n-heptane/air reaction. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the multiple RIFs are introduced. Numerical results indicate that the RIF approach together with the high-pressure vaporization model successfully predicts the ignition delay time and location as well as the essential features of a spray ignition and combustion processes.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.265-266
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• 2015

The multi-environment PDF model coupled with flamelet generated manifolds(FGM) has been developed for a large eddy simulation of turbulent partially premixed lifted flame. This approach has a capability to realistically account for the transport and evolution of probability density function for mixture fraction and progress variable with the manageable computational burden. Using the tabulated chemistry, it is possible to track radical distributions which is important to predict autoignition process with the vitiated coflow environment. Numerical results indicate that the present yields the good agreement with experimental data in terms of mixture fraction, temperature, and species mass fractions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.85-88
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• 2010

본 연구에서는 액체로켓 분사기에서 임계압력 이상의 추진제의 혼합과 연소과정을 수치적으로 모사하여 분석하고자 하였다. 이 과정에서 확장된 $k-{\varepsilon}$ 난류 모델을 이용하여 난류 속도장을 예측하였고 고압에서의 실제 유체 효과를 고려하기 위하여 혼합 추진제의 물성치는 SRK 상태 방정식을 이용하여 계산하였다. 또한 난류 확산 화염에서의 좀 더 정확한 난류와 화학반응의 상호작용을 고려하기 위하여 실제 유체 효과를 고려할 수 있는 층류 화염편 모델을 이용하였다. 수치적인 계산을 바탕으로 이상기체 가정을 사용한 결과와 비교하여 실제 유체의 효과와 기체메탄/액체산소 동축 전단 분사기의 제트화염 구조를 상세하게 살펴보았다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.92-97
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• 2007

Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base burning process. Overall fluid dynamic process is modeled by Navier-Stokes equations for reacting flows with two-equation $k-{\omega}$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

• 한국분무공학회지
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• 제13권1호
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• pp.28-33
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• 2008

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in high-pressure diesel engines. In order to realistically simulate the dimethyl ether (DME) fueled diesel engine, the high pressure vaporization model is utilized and the interaction between turbulence and chemistry is treated by employing the Representative Interactive Flamelet (RIF) model. The detailed chemisty consisted of 336 elementary reaction steps and 78 species is used for DME/air reaction. Numerical results indicate that the RIF model with high pressure vaporization model successfully predicts the essential feature of the combustion processes and pollutants formations in the DME fueled diesel engines.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.449-452
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• 2007

The present study numerically investigate the effects of the Syngas chemical kinetics on the basic flame properties and the structure of the Syngas diffusion flames. In order to realistically represent the turbulence-chemistry interact ion and the spatial inhomogeneity of scalar dissipation rate. the Eulerian Particle Flamelet Model(EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the EPFM model can effectively account for the detailed mechanisms of NOx format ion including thermal NO path, prompt and nitrous NOx format ion, and reburning process by hydrocarbon radical without any ad-hoc procedure. validation cases include the Syngas turbulent nonpremixed jet and swirling flames. Based on numerical results, the detailed discussion has been made for the sensitivity of the Syngas chemical kinetics as well as the precise structure and NOx formation characteristics of the turbulent Syngas nonpremixed flames.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.183-184
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• 2014

The multi-environment probability density function model has been applied to simulate the turbulent stratified premixed flames. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. Computations are made for the non-swirling turbulent stratified premixed flames including SWB1, SWB5 and SWB9. The numerical results obtained in this study are precisely compared with experimental data in terms of axial velocity, unconditional means and conditional means for scalar field including temperature and species mass fraction.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.201-206
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• 2005

In order to realistically represent the complex turbulence-chemistry interaction at the partially premixed turbulent lifted flames encountered in the gas turbine combustors, the combined conserved-scalar/level-set flamelet approach has been adopted. The parallel unstructured-grid finite-volume method has been developed to maintain the geometric flexibility and computational efficiency for the solution of the physically and geometrically complex flows. Special emphasis is given to the swirl effects on the combustion characteristics of the lean-premixed gas turbine combustor. Numerical results suggest that the present approach is capable of realistically simulating the combustion characteristics for the lean-premixed gas turbine engines and the lifted turbulent jet flame with a vitiated coflow.