• Proceedings of the KSME Conference
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• 2001.06d
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• pp.37-42
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• 2001

This paper computes the bluff-body stabilized jet and flame. This study numerically investigates the nonpremixed $C_{2}H_{4}-air$ jet for the nonreacting case and the nonpremixed $CH_{3}OH-air$ turbulent flames for the reacting case using the laminar flamelet model on modified KIVA2 code. And this study predicts $NO_{x}$ formation characteristics using Eulerian Particle Flamelet Model. In the present study, the turbulent combustion model is applied to analyze both nonreacting and reacting case. And both standard $k-{\varepsilon}$ model and modified $k-{\varepsilon}$ model are used in nonreacting case. Calculations are compared with experimental data in terms of velocity, mixture fraction, mixture fraction Root Mean Square and Temperature. The present model correctly predicts the essential features of flame structures and $NO_{x}$ formation characteristics in the bluff-body stabilized flames.

• Journal of the Korean Society of Combustion
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• v.13 no.3
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• pp.24-32
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• 2008

Steady Laminar Flamelet Model (SLFM) calculation is performed to compare the turbulent combustion characteristics of air combustion and oxy-combustion with $CO_2$ recirculation. Radiative heat loss is considered by the optically thin limit assumption. For more realistic simulation the first-order conditional moment closure(CMC) model is applied to SANDIA PILOTED FLAME D again for the oxidants of air and mixture of $O_2$ and $CO_2$. The chemical kinetic machanism for methane is GRI Mech 3.0. Results show that oxy flames are much more stable than air flames, while comparable stability is maintained with 65% $CO_2$ recirculation. The comparable peak temperature is maintained with 80% $CO_2$ recirculation. Higher the temperature, higher the fractions of intermediate species, CO and OH, due to dissociation.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.67-70
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• 2014

We performed computational simulation for a heat recovery steam generator to predict emissions (especially carbon monoxide) and compare the results with experimental data. We used the steady laminar flamelet model(SLFM) which can consider detailed chemical mechanisms. To reduce the number of grid, we simplified the geometry of the whole heat recovery steam generator. In conclusion, the trend of simulation results is good agreement with experimental data.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.195-199
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• 2003

The stoichiometric methan/air premixed turbulent flames at the axisymmetric Bunsen burner situation are numerically investigated. To account for the chemistry-turbulence interaction in the turbulent premixed flames, the steady laminar flamelet library method has been adopted. The flame front is tracked by using the Level-Set Approach. Turbulence is represented by the ${\kappa}-{\varepsilon}$ modeling with a Pope's correction. The detailed comparison between prediction and measurement has made for the flame field in terms of velocity, turbulent kinetic energy, and normarlized temperature.

• Fire Science and Engineering
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• v.28 no.4
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• pp.35-43
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• 2014

The prediction performance of 9 model sets, which combine 3 turbulent models and 3 combustion models, was investigated numerically for turbulent partially-premixed jet flame. The standard ${\kappa}-{\varepsilon}$ (SKE), Realizable ${\kappa}-{\varepsilon}$ (RKE) and Reynolds stress model (RSM) were used as a turbulence model, and the eddy dissipation concept (EDC), steady laminar flamelet (SLF) and unsteady laminar flamelet model (ULF) were also adopted as a combustion model. The prediction performance of those 9 model sets was evaluated quantitatively and qualitatively for Sandia D flame of which flame structure was measured precisely. The flame length was predicted as, from longest to shortest, RSM > SKE > RKE, and the RKE predicted the flame length of the jet flame much shorter than experiment. The flame temperature was over predicted by the combination of RSM + SLF or RSM + ULF while the flame length obtained by RSM + SLF and RSM + ULF was well agreed with the experiment. The combination of SKE + SLF and SKE + ULF predicts well the flame length as well as the temperature distribution. The SKE turbulence model was most superior to the other turbulent models, and SKE + ULF showed the best prediction performance for the structure of turbulent partially-premixed jet flame.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.2
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• pp.103-111
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• 2019

The combined cycle plant is an integration of gas turbine and steam turbine, combining the advantages of both cycles. It recovers the heat energy from gas turbine exhaust to use it to generate steam. The heat recovery steam generator plays a crucial role in combined cycle plants, providing the link between the gas turbine and the steam turbine. Simulation of the performance of the HRSG is required to study its effect on the entire cycle and system. Computational fluid dynamics has potential to become a useful to validate the performance of the HRSG. In this study a solver has been implemented in the open source code, OpenFOAM, for combustion simulation in the heat recovery steam generator. The solver is based on the steady laminar flamelet model to simulate detailed chemical reaction mechanism. Thereafter, the solver is used for simulation of HRSG system. Three cases with varying fuel injections and gas turbine exhaust gas flow rates were simulated and the results were compared with measurements at the system outlet. Predicted temperature and emissions and those from measurements showed the same trend and in quantitative agreement.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.118-125
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• 2007

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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1185-1191
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• 1999

Radiation-induced oscillatory instability in diffusion flames is numerically investigated with nonlinear dynamics considered. As the simplest flame model, a diffusion flame established in the stagnant mixing layer is employed with optically thin gas-phase radiation and unity Lewis numbers for all species. Attention is focused on the radiation-induced extinction regime, which occurs at large $Damk\ddot{o}hler$ number. Once the steady flame structure is obtained for a prescribed value of the initial $Damk\ddot{o}hler$ number, transient solution of the flame is calculated after a finite amount of the $Damk\ddot{o}hler$-number perturbation is imposed on the steady flame. Transient evolution of the flame exhibits three types of flame-evolution behaviors, namely decaying oscillatory solution, diverging solution to extinction and stable limit-cycle solution. A dynamic extinction boundary is identified for laminar flamelet library.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.17-24
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• 2016

The reacting flows of gaseous hydrogen/liquid oxygen 2D coaxial shear injector with varying recess length are numerically analyzed. The standard ${\kappa}-e$ model and laminar flamelet model are adopted for the steady turbulent combustion with the ideal and real gas equations. As the recess length increases, the recirculating region in the combustion chamber expands and the vorticity is intensified. Also, the variations of temperature, products, and pressure are strongly related to the recess length. The results show that an efficient combustor can be obtained by the introduction of the recessed injector.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.79-87
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• 2002

Acoustic responses to pressure oscillations in axisymmetric combustion chamber are numerically investigated to examine the qualitative trend of acoustic instability in liquid rocket engine. Chamber operating condition and excitation frequency of oscillating pressure are selected as exciting parameters of acoustic instability. Artificial perturbation is simulated by total-pressure oscillation with sine wave at chamber inlet. Many approximations and simplifications are introduced without losing the essence of acoustic pressure response. First, steady-state solution for each operating condition is obtained and next, transient analysis is conducted. Depending on operating condition and excitation frequency, the distinct response characteristics are brought. Weak-strength flames and high-frequency excitation tend to cause sensitive acoustic pressure response leading to unstable pressure field. These results are analyzed based on the correlation with acoustic pressure responses from the previous works adopting laminar flamelet model.