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오창보,이창언,Oh, Chang-Bo,Lee, Chang-Eon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.10
A two-dimensional direct numerical simulation was performed to investigate the flame structure of CH$_4$$N_2$-air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed chemistry were adopted in this simulation. The characteristic vortex and chemical time scales were introduced to quantify and investigate the extinction phenomenon during a flame-vortex interaction. The results showed that fuel- and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex was extinguished at much larger scalar dissipation rate than steady flame. It was also found that the air-side vortex extinguished a flame more rapidly than the fuel-side vortex. Furthermore, it was noted that the degree of unsteady effect experienced by a flame can be investigated by comparing the above two characteristic time scales, and this analysis could give an appropriate reason for the results of the previously reported experiment.
CH<sub>4</sub>비예혼합화염의 수치계산에 적용하기 위한 확장된 축소반응기구의 비정상 응답특성 검토
오창보,박정,이창언,Oh, Chang-Bo,Park, Jeong,Lee, Chang-Eon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.2
The extinction behavior and the unsteady response of augmented reduced mechanism(ARM) have been investigated by adopting an OPPDIF code and a numerical solver for the flamelet equations. By comparing the performance of the ARM based on Miller and Bowman's mechanism(MB-ARM) with that of the ARM based on GRI-Mech 3.0(GRI-3.0-ARM), it is identified that the MB-ARM is more suitable for the unsteady calculation because it is relatively less stiff than GRI-3.0-ARM during an ignition process. The steady results using the MB-ARM, which is modified to predict reasonably the extinction point of experiment, are in excellent agreement with those from full mechanism. Under the sinusoidal transient disturbances of scalar dissipation rate, the unsteady responses of the flame temperature and species concentrations using a modified MB-ARM show in very close agreement with those from full mechanism. It is presumed that above modified MB-ARM is very suitable for the unsteady simulation of turbulent flames because it gives not only a low computational cost but also a good prediction performance for flame structure, extinction point and unsteady response.
오창보(Chang Bo Oh),최병일(Byung-il Choi),한용식(Yong-shik Han),김명배(Myung-bae Kim),황철홍(Cheol-hong Hwang) 한국연소학회 2007 KOSCOSYMPOSIUM논문집 Vol.- No.-
A micro cyclone combustor was developed to be used as a component of mobile power generator (MPG). The cyclone combustor was designed so that fuel and air were supplied to the combustion chamber separately to prevent a flash-back. The flame shape stabilized inside the micro cyclone combustor was visualized experimentally and the flow field and the combustion characteristics of the combustor were investigated numerically. The global equivalence ratio (Φ), defined using the fuel and air flow rates, was introduced to examine the overall flow and flame features of the combustor. The flame stabilization mechanism could be well understood using the velocity distribution inside the combustor. For only non-reacting case, it was found that a weak recirculating zone was formed upper the fuel-supplying tube in case of Φ <1.0. It was also found that small regions that have a negative axial velocity exist near the fuel injection ports for both of non-reacting and reacting case. It was identify that a flame front was stabilized at the negative axial velocity regions near the fuel injection ports.
단일 와동과 상호작용하는 대향류 비예혼합화염 구조에 대한 수치해석 연구
오창보(Chang-Bo Oh),박정(Jeong Park),이창언(Chang-Eon Lee) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
A two-dimensional direct numerical simulations was performed to investigate the flame structure of CH₄/N₂-Air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed reaction mechanism were adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. Results show that the fuel- and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished in much larger SDR than steady flame. It was also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex.
마이크로 사이클론 연소기의 혼합 및 유동특성에 관한 수치해석 연구
오창보(Chang Bo Oh),최병일(Byung-il Choi),한용식(Yong-shik Han),김명배(Myung-bae Kim),황철홍(Cheol-hong Hwang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
A micro cyclone combustor was developed to be used as a heat source of thermoelectric power generator (TPG). The cyclone combustor was designed so that fuel and air were supplied to the combustion chamber separately. The mixing and flow characteristics in the combustor were investigated numerically. The global equivalence ratio (Φ), defined using the fuel and air flow rates, was introduced to examine the flow features of the combustor. The mixing of fuel and air inside the combustor could be well understood using the fuel concentration distribution. It was found that the weak recirculating zone was formed upper the fuel-supplying tube in case of Φ < 1.0. In addition, it was found that small regions that have a negative axial velocity exist near the fuel injection ports. It is assumed that these negative axial velocity regions can stabilize a flame inside the micro cyclone combustor.