• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.9-12
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• 2012

In this study, opposed flow combustion was re-visited in a narrow channel. Various flame behaviors were observed. Due to the confined structure of the combustor in this study, flame structures at very narrow strain rate could be stabilized and their characteristics were investigated. This study will be helpful to understand overall flame behavior of non-premixed flame in a narrow combustion space, and will also be useful to develop small combustors.

• 대한기계학회논문집B
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• 제27권4호
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• pp.447-457
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• 2003

An experiment in a turbulent non-premixed flat flame was carried out in order to investigate the effect of swirl number on the flow and combustion characteristics. First. stream lines and velocity distribution in the flow field were obtained using PIV method. In contrast with the axial flow without swirl, highly swirled air induced stream lines along the burner tile. and backward flow was caused by recirculation in the center zone of the flow field. In the combustion. the flame with swirled air also became flat and stable along the burner tile with increment of the swirl number. Flame structure by measuring OH and CH radicals intensity and by calculating Damkohler number(Da) and turbulence Reynolds number(Re$_{T}$) was examined. It appeared to be comprised in the wrinkled laminar-flame regime. Backward flow by recirculation of the burned gas decreased the flame temperature and emissions concentrations as NO and CO. Consequently, the stable flat flame with low NO concentration was achieved.d.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.185-186
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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. The IEM mixing model is employed to represent the mixing process and the chemical mechanism is based on Gri 3.0 mechanism. Numerical results obtained in this study are precisely compared with experimental data in terms of unconditional and conditional means for scalar fields and velocity fields.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.787-790
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• 2017

본 연구는 이원추진제 추력기(thruster)에 사용되는 메탄-산소 연소특성규명의 선행연구로서 모델연소실 내 전단동축형인젝터를 통해 분사된 기체메탄-기체산소 비예혼합화염의 연소안정한계 및 화염형상을 도출하기 위한 실험적 연구가 수행되었다. DSLR 카메라를 이용하여 화염 직접이미지(direct image)를 촬영하였고, 이미지 후처리(post-processing)를 통해 연소특성파악 및 화염길이 정량화를 수행하였다. 그 결과, 산화제 레이놀즈 수($Re_o$)가 증가함에 따라 이론반응비(stoichiometric ratio)에서 안정된 화염이 발생하였고, 동일 인젝터직경 조건에서 난류화염의 길이가 늘어남을 확인하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.7-12
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• 2006

The propagation rates ($U_{edge}$) of various premixed edge-flames were measured as a function of global strain rate (${ \sigma}$), mixture strength, and Lewis number (Le). Using a counterflow slot-jet burner with electrical heaters at each end, both advancing (positive $U_{edge}$) and retreating (negative $U_{edge}$) edges can be studied as they propagate along the long dimension of the burner. Preliminary results are presented for single and twin premixed hydrocarbon edge-flames in terms of the effects on $U_{edge}$. A low-${\sigma}$ extinction limit has been discovered for all mixtures tested but further analysis is necessary for full characterization since sufficiently $high-{\sigma}$ leads to an apparent stability limit. Propagation rates clearly show a strong dependence on Le. Future work will focus on completing the premixed hydrocarbon edge-flame analysis and include investigations into non-premixed edge-flames and edge-flames composed of fuels such as hydrogen ($H_2$) with significantly lower Le.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.181-188
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• 2005

Large eddy simulation(LES) methodology used to model the isothermal swirling flows in a dump combustor and the turbulent premixed flame in a model gas turbine combustor. The LES solver was implemented on parallel computer consisting 16 processors. In isothermal flow simulation, the results was compared with that of ${\kappa}-{\varepsilon}$ model as well as experimental data, in order to verify the capability of LES code. To model the turbulent premixed flame in a gas turbine, the G-equation flamelet model was used. The results showd that LES and RANS well predicted the mean velocity field of a non-swirling flow. However, in swirling flow, LES showed a better performance in predicting the mean axial and azimuthal velocities, and the central recirculation zone than those of RANS. In a model gas turbine combustor, the operation condition of high pressure and temperature induced the different phenomena, such as flame length and flow-field information, comparing with the condition of ambient pressure and temperature. Finally, it was identified that the flame and heat release oscillations are related to the vortex shedding generated by swirl flow and pressure wave propagation.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.79-84
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• 2004

For the non-premixed interacting jet flames, it has been reported that if eight small nozzles are arranged along the circle of 40 $^{\sim}$ 72 times the diameter of single jet, the flames are not extinguished over 2oom/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, ${\Phi}$, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying Sand ${\Phi}$ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with ${\Phi}$ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of fuel through the centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was different from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.

• 대한기계학회논문집B
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• 제34권5호
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• pp.547-552
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• 2010

본 연구에서는 VIStA(Vortex Inertial Staged Air) 버너를 개조하여 관류보일러에 적용하였다. 개조는 크게 2가지 부분에서 이루어 졌는데, 먼저 원형에서 채택한 예혼합 연소 방식을 사용상 편의와 안전을 위해 비예혼합방식으로 변경하였다. 연소 방식의 변경에 따라 공기 1차, 2차에 별도의 송풍기를 사용하던 공급 방식도 변경하여 본 연구에서는 하나의 송풍기로부터 공기를 공급받아 댐퍼를 통하여 1, 2차 연소실에 분할하여 공기를 공급하도록 하였다. 본 연구에서는 질소 산화물(NOx)의 생성을 억제하는 최적의 운전 조건을 찾기 위하여 전체 공기비 및 1, 2차 연소실로의 공기 분배 비율에 따른 NOx 생성 특성을 관찰하였다. 본 연구에서 산업용 보일러에 적용하기 위해 개조한 비예혼합 방식의 VIStA 버너를 설치한 결과, 기존의 일반 버너에 비해 균일한 화염을 얻었고 질소 산화물을 최대 20%까지 줄일 수 있는 것을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2964-2964
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• 2008

• 대한기계학회논문집B
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• 제26권6호
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• pp.833-841
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• 2002

The present study examined the possibility of NOx reduction in the high temperature industrial furnaces, duct burner of gas turbine cogeneration and two-stage gas turbine combustor. The experimental study was carried out for the non-premixed flame of second stage combustor with the variations of oxygen concentration in the hot exhaust gas of first stage combustor. It also examined the flammability range, temperature and NOx, $CO_2$, $O_2$formation in the combustor with respect to oxygen concentration in which the fuel(natural gas) is supplying into the hot exhaust gas. The results show that the inner temperature of flame reaches 1,20$0^{\circ}C$ at EGR $O_2$23% and that 15ppm of NOx at EGR $O_2$15.5% increases up to 60ppm at EGR $O_2$23%. It is believed that Fenimore＇s prompt NOx mechanism is more influential on the NOx formation than Zeldovich＇s thermal NOx mechanism does.