• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.450-454
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• 2005

축대칭 동축형 램제트 연소기에 대한 반응 유동장 해석을 수행하였다. 2차원 축대칭 Wavier-Stokes 방정식과 낮은 레이놀즈 수 $k-\varepsilon$ 난류 모델을 이용하였고, 유한반응률 화학반응 모델을 적용하였다. 난류 연소 모델인 EDM (Eddy-Dissipation Model)과 층류 반응 모델을 적용한 경우를 서로 비교하였다. 급확대 연소기와 wedge형 보염기를 장착한 동축형 램제트 연소기에 대한 반응 유동장 수치해석을 통해 두 가지 결과를 화염안정 측면에서 서로 비교하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.162-168
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• 2000

This paper conducted experimental study of turbulent diffusion flame, equipped with a unique double swirler combustor for gas fuel. The burner has two vane swirlers which are fitted to primary, secondary air channel. Temperature, and NOx emission concentrations are measured in combustion flame region and velocity in cold flow for various primary/secondary air ratio conditions. The results showed the characteristics of swirl flame and decreasing NOx concentrations with increasing primary/secondary air ratio.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.47-54
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• 1999

A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength assigned by the density difference between the burned and the unburned region. The present model provides good agreement with the experimental results by using realistic volume expansion ratio which was not reached in the previous researches. Including volume expansion, the flow predicts the same behavior of measured velocity field qualitatively. The flame propagation in varying flow field due to volume expansion provides a promising way to represent the wrinkled turbulent premixed flames in a numerically efficient manner.

• 대한기계학회논문집
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• 제18권2호
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• pp.512-518
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• 1994

An experimental study is made on turbulent diffusion flames stabilized by a circular cylinder in a divergence flow. In this paper, stabilization characteristics and flame structure are examined by varying the divergence angle of duct and position of a circular cylinder. The fuel used is a commercial grade gaseous propane injected by two slit of rod. It is found that the positive pressure gradient greatly influences the eddy structure behind the rod. and that two different kinds of combustion patterns exist at the blowoff limit depending on the divergent angle of duct. They are distinguished by their wake structures: one associated with Karman vortex shedding, the other without it. Also, the blowoff velocity in the former is found to be higher than in the later.

• 대한기계학회논문집B
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• 제29권11호
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• pp.1277-1284
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• 2005

The combustion characteristics of methane oxygen diffusion flames have been investigated to give basic information for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since the small amount of nitrogen is included from the current low cost oxygen production process. Flame lengths decreased with increasing fuel or oxygen velocity because of the enhancement of mixing effect. Correlation equation between flame length and turbulent kinetic energy was proposed. NOx concentration was reduced with increasing fuel or oxygen velocity because of the enhanced entrainment of the product gas into flame zone as well as the reduction of residence time in combustion zone.

• 대한기계학회논문집B
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• 제30권9호
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• pp.891-897
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• 2006

The SRS method is applied to a turbulent flame with radiation/turbulence interaction to invert the temperature and concentration profile. The flame is conditioned as optically thin per each fluctuation length and the flame spectral intensity is measured for inversion. From inversion result, we find that SRS can successfully invert the coupled temperature/concentration fluctuation amplitudes. For two cases of experiments, inverted values are within approximately 1% over the full range of fluctuation amplitude. However, SRS cannot find the detailed local fluctuation parameters such as pattern and phase, etc. as far as they do not affect the resulting radiation intensity. Important available parameters are the mean temperature and the temperature fluctuation amplitude. The radiation/turbulence interaction effect is verified to play an important role in the radiation.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.80-89
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• 2002

The flame structure and soot formation in Acetylene-Air nonpremixed jet flame are numerically analyzed. We employed two variable approach to investigate the soot formation and oxidation processes. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of pyrene and acetylene. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical model used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reaction flow field.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2977-2983
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• 2008

The combustion characteristics of a partially premixed flame in a dump combustor were studied to determine the effects of hydrogen enrichment in propane. Bluff-body was used for flame stabilization. Fuel mixtures containing a hydrogen mole fraction ranging from 0.1 to 0.5 were burnt at ambient pressure within a quartz chamber. Tests were carried out keeping the total reactant flow rate by adjusting the fuel and air flow rates. The fluctuations of pressure were measured by piezoelectric pressure sensor. The instantaneous flame structure and OH chemiluminescence images were described by High-speed Intensified Charged Coupled Device (HICCD) camera and Intensified Charged Coupled Device (ICCD) camera. The present results show that hydrogen enrichment in fuel changed the location of primary reaction zone from inner recirculation zone to turbulent shear layer and pressure signal. The reason is that chemical aspects take precedence over flow aspects in the hydrogen-enriched flame.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.139-154
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• 1998

Under certain circumstance, premixed turbulent flame can be treated as wrinkled thin laminar flame and its motion in a hydrodynamic flow field has been investigated by employing G-equation. Past studies on G-equation successfully described certain aspects of laminar flame propagation such as effects of stretch on flame speed. In those studies, flames were regarded as a passive interface that does not influence the flow field. The experimental evidences, however, indicate that flow field can be significantly modified by the propagation of flames through the volume expansion of burned gas. In the present study, a new method to be used with G -equation is described to include the effect of volume expansion in the flame dynamics. The effect of volume expansion on the flow field is approximated by Biot-Savart law. The newly developed model is validated by comparison with existing analytical solutions of G -equation to predict flames propagating in hydrodynamic flow field without volume expansion. To further investigate the influence of volume expansion, present method was applied to initially wrinkled or planar flame propagating in an imposed velocity field and the average flame speed was evaluated from the ratio of flame surface area and projected area of unburned stream channel. It was observed that the initial wrinkling of flame cannot sustain itself without velocity disturbance and wrinkled structure decays into planar flame as the flame propagates. The rate of decay of the structure increased with volume expansion. The asymptotic change in the average burning speed occurs only with disturbed velocity field. Because volume expansion acts directly on the velocity field, the average burning speed is affected at all time when its effect is included. With relatively small temperature ratio of 3, the average flame speed increased 10%. The combined effect of volume expansion and flame stretch is also considered and the result implied that the effect of stretch is independent of volume release.

• 대한환경공학회지
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• 제29권6호
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• pp.647-653
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• 2007

본 연구의 목적은 기존의 산업용 보일러에서 이산화탄소 배출저감을 위하여 연소가스 재순환에 의한 고온 순산소 연소기술을 개발하는데 있다. 이를 위해 실험실 규모의 LNG 연소기에서 연소 화염특성을 평가하기 위한 조직적인 수치해석 연구가 일차적으로 수행되었다. 특히 본 연구에서 고려한 중요한 변수는 산소부화환경에서 계산된 연소가스의 재순환 정도이다. 배기가스 재순환이 없는 100% 순산소 연소환경에서 화염은 고온의 길고 가는 층류형상의 화염을 보였다. 이는 산화제 중에서 질소성분이 감소함으로써 약화된 난류혼합효과와 $N_2$ 가스에 의한 현열손실의 감소에 기인하는 것으로 판단하였으며 문헌에 발표된 실험과 일치된 결과를 보였다. $O_2/CO_2$ 혼합가스에서 $CO_2$ 가스의 재순환율이 증가될수록 산화제의 유량 증가에 따른 강화된 난류혼합으로 인해 최고 화염온도가 버너 근처로 이동한 반면 전반적인 연소가스 온도는 $N_2$에 비해 $CO_2$의 높은 비열로 인해 낮아지는 현상을 보였다. 결국 80% 이상 $CO_2$ 가스를 재순환한 경우 연소가스의 온도가 급격하게 떨어지는 화염소멸 현상을 보여주었다. 그러나 30% $O_2/70%$ $CO_2$의 혼합 연소조건에서는 기존의 공기연소와 유사한 가스온도를 나타내었다. 이외에도 공기연소와 동일한 유량조건에서 난류강도와 열수지 측면에서 화염특성 변화를 평가하기 위한 면밀한 연구가 수행되었다.