• 한국화재소방학회논문지
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• 제21권4호
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• pp.18-24
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• 2007

본 연구는 아트리움 방호공간에서 화재발생시 복사열전달의 유무에 따른 유동장 및 온도분포의 예측을 목적으로 수치해석을 수행하였다. 화재모델로 Field 모델을 사용하였으며 난류 모델로 SIMPLE 알고리즘이 적용된 표준 $k-{\varepsilon}$ 모델을 사용하였다. 복사열전달 해석에 필요한 복사물성치의 계산은 속도를 단축하며 정확성을 유지하는 WSGGM-RG를 사용하였다. 난류유동장과 복사열전달의 계산은 자체 개발된 CCRHT-3D 프로그램을 사용하였다. 해석결과에 의하면 화재지점을 제외하고 아트리움의 천장부가 높은 온도분포로 나타났다. 유동과 온도의 분포가 출입문 방향으로 편향되고 화재의 위치에서 아트리움의 천장과 벽에 가까워질수록 온도가 낮아지는 경향을 보였다. 이러한 결과는 천장 스프링클러헤드의 작동 시점을 예측하는데 복사열의 영향이 크다는 것을 의미하게 된다.

• 한국연소학회지
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• 제10권3호
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• pp.10-16
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• 2005

Detailed flame structures of the counterflow flames of $CH_4/Air$ formed with $CO_2$ and $H_2O$ addition are studied numerically. The detailed chemical reactions are modeled by using the OPPDIF and CHEMKIN-II code. Only the $CO_2$ and $H_2O$ are assumed to participate in radiative heat transfer while all other gases are assumed to be transparent. The discrete ordinates method(DOM) and the narrow band based WSGGM with a gray gas regrouping technique(WSGGM-RG) are applied for modeling the radiative transfer through non-homogeneous and non-isothermal combustion gas mixtures generated by the counter flow flames. The results compared with the SNB model show that the WSGGM-RG is successful in modeling the counterflow flames with non-gray gas mixture. The numerical results show that the addition of $CO_2$ and $H_2O$ to the oxidant nozzle lowers the peak temperature and the NO concentration in flame.

• Journal of Mechanical Science and Technology
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• 제20권2호
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• pp.242-250
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• 2006

Detailed structures of the counterflow flames formed for different inlet fluid temperatures and different amount of additives are studied numerically. The detailed chemical reactions are modeled by using the CHEMKIN-II code. The discrete ordinates method and the narrow band based WSGGM with a gray gas regrouping technique (WSGGM-RG) are applied for modeling the radiative transfer through non-homogeneous and non-isothermal combustion gas mixtures generated by the counterflow flames. The results compared with those obtained by using the SNB model show that the WSGGM-RG is very successful in modeling the counterflow flames with non-gray gas mixture. The numerical results also show that the addition of $CO_2\;or\;H_2O$ to the oxidant lowers the peak temperature and the NO concentration in flame. But preheat of fuel or oxidant raises the flame temperature and the NO production rates. $O_2$ enrichment also causes to raise the temperature distribution and the NO production in flame. And it is found that the $O_2$ enrichment and the fuel preheat were the major parameters in affecting the flame width.

• 한국연소학회지
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• 제10권2호
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• pp.9-17
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• 2005

WSGGM with gray gas regrouping is successfully applied to study the flame structure of opposed flow flames including effect of radiative transfer. The statistical narrow band model is used to obtain the benchmark solutions. Results obtained by using the optically thin model are shown to overestimate the emission and to predict the flame structures inadequately especially for optically thick and low stretch rate flames. Computed results by using the WSGGM with 10 gray gases and SNB model show reasonable agreements with each other, and the required calculation time for the WSGGM is acceptable for engineering applications.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.79-85
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• 2006

Radiative heat transfer is very important in many combustion systems since they are operated in high temperature. Fluid flows in most of the combustion systems are turbulent to promote fast mixing of the hydrocarbon fuel and oxidant. Major combustion products are $CO_2$ and $H_2O$. The turbulent flow is modeled by using the standard ${\kappa}-{\epsilon}$ model and the radiation transfer is modeled by using the discrete ordinates method where the radiative gas properties are calculated by using the weighted sum of gray gases model with a gray gas regrouping(WSGGM-RG). Effect of the radiation on the combustion characteristics in a three-dimensional rectangular enclosure is studied by changing the equivalence ratio. Results show that the radiation plays a significant role on the heat transfer in the combustion systems by resulting in a temperature drop of 16% as compared to that obtained without radiation. The equivalence ratio also affects the combustion by different contribution of the radiative transfer with different gas compositions.