• 한국연소학회지
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• 제15권4호
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• pp.15-21
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• 2010

The transported probability density function(PDF) model has been applied to simulate the turbulent nonpremixed piloted jet flame. To realistically account for the mixture fraction PDF informations on the turbulent non-premixed jet flame, the present Lagrangian PDF transport approach is based on the joint velocity-composition-turbulence frequency PDF formulation. The fluctuating velocity of stochastic fields is modeled by simplified Langevin model(SLM), turbulence frequency of stochastic fields is modeled by Jayesh-Pope model and effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate the present approach, the numerical results obtained by the joint velocity-composition-turbulence frequency PDF model are compared with experimental data in terms of the unconditional and conditional means of mixture fraction, temperature and species and PDFs.

• 대한기계학회논문집B
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• 제25권7호
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• pp.885-894
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• 2001

A large eddy simulation(LES) is performed for turbulent flow in a combustion device. The combustion device is simplified as a cylinder with sudden expansion. To promote turbulent mixing and to accommodate flame stability, a flame holder is attached inside the combustion chamber. Emphasis is placed on the flow details with different geometries of the flame holder. The subgrid scale models are applied and validated. The simulation code is constructed by using a general coordinate system based on the physical contravariant velocity components. The calculated Reynolds numbers are 5000 and 50000 based on the bulk velocity and the diameter of inlet pipe. The predicted turbulent statistics are evaluated by comparing with the LDV measurement data. The agreement of LES with the experimental data is shown to be satisfactory.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.185-193
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• 2003

Basic flow fields of two dimensional V flames were examined as a preliminary work to study the instability of premixed flame with vorticity generation. Laminar premixed propane and methane flame were anchored by electrically heated wire to make two dimensional V flames. Flow fields were measured mainly by PIV(Particle Image Velocimetray) and the results were compared with those obtained by LDV(Laser Doppler Velocimetry) to confirm their reliability. Because the curvatures of V flames are so small, V flames were locally assumed to be inclined planar flames in gravitational field. The measured flow fields were locally compared with those of analytical solutions, which showed the qualitatively similar results. In downstream region, the vorticity fields were nearly constant except region near the center line, which support the assumption of locally one dimensional flame. Besides it was tried to find experimentally the similarity of flow fields in downstream region. Finally, stability diagram of propane and methane flames were drawn for the equivalence ratio less than one and the wide range of mean velocity.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.253-255
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• 2012

This study has numerically investigated the combustion processes in the bilayer porous media. To account for the velocity transition and diffusion influenced by solid matrix, porosity effects are included in the governing equations. Heat transfer coefficient is calculated by Nusselt number to reflect the effect of gas velocity, pore diameter, and material properties. Numerical results indicate that the present approach is capable of the essential features of the premixed combustion in the porous burner, in terms of the precised flame structure, pollutant formation, and flame stabilization. It is also found that heat transferred from the downstream flame zone is conducted to the upstream flame region through the solid matrix and the preheated mixture. By increasing the inlet velocity, the solid temperature of upstream is cooling down.

• 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.

• 한국화재소방학회논문지
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• 제19권3호
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• pp.44-51
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• 2005

도료공업, 유기합성의 원료, 혼합용제 및 분석용 시약으로 광범위하게 이용되고 있는 메틸알콜에 대하여 작업장에서 발생할 우려가 있는 화재 폭발 예방 대책을 수립하기 위한 기초자료를 획득하기 위하여 화염전파속도와 화염도달시간을 측정하였다 용기의 크기를 변화시키고 온도 및 농도를 변화시켜 실험을 행한 결과 시료의 용기가 적을수록 연소가 용이하고 연소속도는 빠르게 나타났으며, 최대연소속도는 소용기 $30^{\circ}C$에서 200 cm/sec를 구하였다. 화염도달시간은 시료 용기의 크기가 클수록 길어지는 경향을 나타내었으며, 시료의 온도 및 농도가 높아질수록 짧아졌다.

• 한국연소학회지
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• 제5권2호
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• pp.69-78
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• 2000

Reattachment characteristics of laminar flames in partially premixed jets are studied for propane fuel mixed with air. As the flow rate decreases, liftoff height is decreased nonlinearly and the flame reattaches to a nozzle at a certain liftoff height. Using a jet theory by taking into account a virtual origin, it is predicted that flow velocity along a stoichiometric contour has a maximum value near nozzle. With this velocity characteristics, it is shown that reattachment mechanism can be explained by a balance between flame speed and flow velocity. Predicted displacement speeds at reattachment and liftoff agree qualitatively well with experimental findings.

• Korean Chemical Engineering Research
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• 제60권2호
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• pp.229-236
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• 2022

동일 분체특성의 분진이 평균입경, 농도, 분진조건(부유 또는 퇴적) 변화에 따른 화재폭발 위험성을 조사하였다. 이를 위해 20L분진폭발시험장치, 열중량분석장치, 연소속도시험장치(UN시험법)를 사용하였다. 4종 분진(Sugar, Mg, Al, Zr)의 입경이 서로 다른 8개 분진 시료에 대하여 부유 분진의 폭발특성과 화염전파속도(FPV), 그리고 퇴적분진의 화염확산속도(FSV)를 조사하였다. 부유 분진 조건에서 Mg 및 Al 분진은 입경이 감소하면 폭발 위험성이 증가하였지만, Sugar는 입경 변화에 따른 폭발 위험성의 영향이 거의 나타나지 않았다. 부유 분진의 화염전파속도(FPV)는 마이크로 범위에서의 입경 변화보다 마이크로에서 나노로 입경이 감소하면 크게 증가하였다. 퇴적층의 화염확산속도(FSV)는 수평면(기울기 0°)보다 경사면(기울기 30°)에서 증가하는 경향을 나타냈으며, 경사면(기울기 30°) 퇴적층 조건에서는 상방 전파가 하방 전파보다 높게 나타났다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.65-72
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• 2003

In order to clarify turbulent combustion characteristics of hydrocarbon mixtures by hydrogen addition, turbulent burning velocities in a constant volume vessel were measured for both lean and rich hydrocarbon mixtures. Moreover, the configuration characteristics of turbulent flame was investigated in the wrinkled laminar flame region. A laser tomography technique was used to obtain the images of turbulent flame, and quantitative analyses were performed. As a result, the characteristics of turbulent burning velocity was shown a distinct difference with the addition rate of hydrogen between lean and rich mixtures. On the other hand, the obtained tomograms showed that the surface area of turbulent flame depends almost only on the turbulence intensity.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1701-1709
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• 1997

The diagnostic used to observe the early flame development was a fiber optic spark plug, which enabled measurement of the flame front arrival times on a cycle-to-cycle basis. The data obtained with this fiber optic spark plug were analyzed to obtain two parameters to describe the behavior of the flame kernel : an expansion speed and a convection velocity. In addition, synchronized cylinder pressure data were taken to compare with the fiber optic spark plug data on a cyclic basis. Heat release analysis was performed on the cylinder pressure data to obtain the mass burning profile of the charge for each cycle. There was a significant correlation observed in the initial flame duration and the kernel expansion speed with dwell angle.