• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.5
• /
• pp.121-131
• /
• 2013

The characteristics of flame dynamics occurring near the bluff body was experimentally investigated in a model combustor with V-gutter bluff body. Measurements of chemiluminescence with high speed camera and PIV were performed for visualization of flame structure. Flashback occurs due to the change of pressure gradient in the combustor, and the flashback distance depends on equivalent ratio. Unstable flames can be classified into three types depending on the flashback distance and structure. When the flame goes over the bluff body, an unusual flame structure occurs at the front of the bluff body. Re-stabilization takes place as the flame moves downstream of the combustor. This process is supported by a strong vortex structure behind the bluff body.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2003.05a
• /
• pp.408-411
• /
• 2003

PPV(Positive Pressure Ventilation)란 화재진압시 송풍기를 이용하여 화염이 발생한 구조물 내부로 신선한 공기를 유입시켜 내부압력을 상승시키는 방식으로서, 구조물 내부의 전체 영역에 균일하게 열ㆍ연기 및 연소 생성물 등의 급속 배기 및 구조물 내부온도를 급속히 감소시킬 수 있는 것이 특징이다.(중략)

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.4
• /
• pp.912-919
• /
• 1990

본 연구에서는 다중선회연소기의 원리에 기초하여 속도차가 있는 두 공기류의 전단층에 기체연료를 분출하여 연소시키면 연료가 두 공기류 사이에 유입되므로 연료 가 산화제의 접촉면적이 증대되고 또한 난류혼합속도가 큰 영역으로 연료가 유입되므 로 혼합효과가 증대되어 고부하연소에 적절한 방식이 될 것으로 생각하여 동축이중공 기분류중의 난류 확산화염에 대해 그 화염구조를 밝히고 이 화염을 실용연소기에 응용 하기 위한 기초자료를 얻는데 목적이 있다.

• 한국연소학회:학술대회논문집
• /
• 2000.05a
• /
• pp.57-66
• /
• 2000

OH radical and NO distributions have been measured in methane/air partially premixed counterflow flames(${\alpha}$=1.0, 0.8, 0.6) using PLIF technique. The results are discussed and compared with the numerical analysis results obtained under the same flame conditions. Measured OH and NO LIF signals agree with the computed concentration distributions. Both numerical and experimental results indicate that the structural change in a flame alters the NO formation characteristics of a partially premixed counterflow flame. The nitrogen dilution also changes flame structure, temperature and OH radical distributions and results in the decreased NO concentrations in a flame. The levels of decrease in NO concentrations, however, depends on the premixedness(${\alpha}$) of a flame. The larger change in the flame structure and NO concentrations have been observed in a premixed flame($\alpha$=1.0), which implies that the premixedness is likely to be a factor in the dilution effect on NO formation of a flame.

• Journal of Power System Engineering
• /
• v.2 no.1
• /
• pp.17-24
• /
• 1998

The combustion regime was discussed using a laser tomography and flame structure diagram. It was shown first how to represent the turbulent burning velocity and flame structural parameters in the dimensionless plane referred to as the flame structure diagram. And then, turbulent flame structure from the obtained images by laser tomography was compared with combustion regime in the Re-Da plane, one of the diagrams, specified by different researchers. As the result, the $u'/S_{L0}$ ratio at the boundary between the wrinkled laminar flame regime and reactant islands flame regime was found to be about 1.5.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.72-80
• /
• 1988

Partially premixed diffusion system is analyzed using the matched asymptotic expansion technique adopting counterflow with supplying fuel and oxidizer from one side and fuel only from the other as a model problem. Results show that single-stage extinction always occurs as stretch increases, and the partially premixed diffusion flame can hardly exist. Depending on the initial mixture concentrations, either premixed or diffusion flame extinction leads to complete extinction of the system, and the diffusion flame can change its character to premixed flame such that two premixed flames can exist in the partially premixed-diffusion system.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1493-1498
• /
• 2004

WSGGM with gray gas regrouping is successfully applied to study the flame structure of counter 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.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.6
• /
• pp.647-653
• /
• 2012

A short reaction mechanism for premixed $CH_4$-air flames at high pressure was developed using a reduction method based on the combined application of the simulation error minimization connectivity method and the iterative species-removal sensitivity method. It consisted of 43 species and 554 elementary reactions under the condition that it produces less than 5% of the maximum error. The flame structures obtained using a detailed reaction mechanism and the short reaction mechanism were compared for $CH_4$-air flames with various initial temperatures and equivalence ratios at high pressure, and the results were in good agreement. Therefore, the short reaction mechanism developed could reproduce the flame speeds, temperatures, and concentrations of major and minor species at high pressure.

• Journal of the Korean Society of Safety
• /
• v.17 no.3
• /
• pp.107-111
• /
• 2002

A near extinction nonpremixed counterflow flame of 19% methane diluted by 81% nitrogen by volume and undiluted air at a low global strain rate, 20 s-1, was computed. Investigations were focused on effects of the duct thickness and velocity boundary conditions on the flame structure in normal and zero gravity conditions. The results showed that, under normal gravity conditions, the effects of the duct thickness and velocity boundary conditions were significant by shifting the flame position, but negligible in zero gravity. The differences in flame structure were caused by buoyancy, and hence should be considered in the measurements in normal gravity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.1
• /
• pp.133-140
• /
• 2002

This article presents an application of a large-scale structural mixing model(Broadwell et at. 1984) to the blowout of turbulent reacting cross flow jets. Experimental observations, therefore, aim to identify the existence of large-scale vortical structure exerting an important effect upon the flame stabilization. In the analysis of common stability curve, it is seen that the phenomenon of blowout are only related to the mixing time scale of the two flows. The most notable observation is that the blowout distance is traced at a fixed positions according to the velocity ratio at all times. Measurements of the lower blowout limits in the liftable flame are qualitatively in agreement with the blowout parameter $\xi$, proposed by Broadwell et al. Good agrement between the results calculated by a modified blowout parameter $\xi$'and the present experimental results confirms the important effect of large-scale structure in the stabilization feature of blowout.