• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.497-508
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• 1985

본 논문에서는 일양한 예혼합 기류중에 놓여진 원주 후류의 고온 순환류에 의 해 보지되는 난류 예혼합 화염을 대상으로 해서 유동의 가시화 및 온도와 이온전류의 변동의 측정에 의해서 화염의 구조를 조사한 결과, 원주 보염기 후류의 재순환 영역부 근에 형성된 전단층에 있어서는 코히렌트(Coherent)구조의 화염이 되고 하류부에서는 불규칙한 3차원 와(渦)에 지배되는 전파성 화염이 형성 되었다. 온도변동에 대한 쌍 봉성의 확율밀도분포와 이온전류변동에 대한 3개의 피이크의 확율밀도분포는 엷은 반 응면을 사이에 두고 미연혼합기괴와 기연가스괴가 서로 접하는 주름 상층류화염 또는 층류화염편의 구조에 대응하며, 코히렌트 와(渦)에 지배되는 화염에 있어서는 거시적 혼합은 코히렌트 와의 거동에 지배되나 그 구조는 주름상층류 화염과 일부 강한 전단 력을 받는 부분에는 분산 반응영역의 구조임이 밝혀졌다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.315-320
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• 2008

This experimental study has been conducted to investigate the effect of the flame holder on the multi-slot film cooling in the ramjet combustor. The turbulent wake which is generated by the flame holder on the entrance of the coolant flow path affects on the slot. Adiabatic film cooling effectiveness on the downstream wall of the slot exit are measured. The results show that the film cooling performance is rapidly decreased after the slot exit by shear layer and high turbulence intensity between separated flows and coolant flows.

• Fire Science and Engineering
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• v.17 no.2
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• pp.25-34
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• 2003

In this paper, characteristics of the DC flashover voltage in the horizontal air gap of sphere-sphere/needle-needle electrode system were investigated when the combustion flame of paraffin oil was present between the two electrodes. The reduction characteristic of DC flashover voltage was discussed with the thermal ionization process, the relative air density and the deflection phenomena in the shape of flames that caused by the corona wind and Coulomb's force. As the results of an experimental investigation, It was found that the reduction characteristics of DC flashover voltages with flames were affected strongly by the flame deflection and the change of relative air density. It was also found that the thermal ionization phenomena were not important in the range of combustion flame temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.305-309
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• 2008

This experimental study has been conducted to investigate the installation of the vertical flame holder shape in ramjet combustor, which affects on the film cooling effectiveness. All slot position, the film cooling effectiveness decreases because of the shear layer and high turbulence intensity between separated flows and coolant flows. When the flame holder is installed, film cooling effectiveness decreases abruptly on the beginning of the slot exit region due to the mixing effect. As the blowing rate increases, the film cooling effectiveness is increased for all cases due to the augmented momentum of injected coolant from the slot.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.44-51
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• 2005

In this paper, reduction characteristics of the AC and DC flashover voltage in the horizontal air gap of sphere-sphere electrode system were investigated when the combustion flame was present near the high voltage electrode. The voltage and current waveforms were measured, when the flashover is occurred, in order to examine the flashover polarity by flame. The reduction characteristics of AC flashover voltage were discussed with the thermal ionization process, the relative air density and the deflection phenomena in the shape of flames that caused by the coulomb's force. As the results of an experimental investigation, It was found that the reduction of flashover voltages in sphere-sphere system, in comparison with the no flame case, are $79.9[\%]$ for k=0, $82.9[\%]$ for k=0.5, $87.5[\%]$ for k=1.0, $85.0[\%]$ for h=0[cm], $40.8[\%]$ for h=5[cm] and $28.2[\%]$ for h=9[cm] when ac voltage is applied. The influence for thermal ionization process of the combustion flame in small scale no particular change is recognized.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.27-34
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• 2002

In this paper, characteristics of the ac and dc flashover voltage in the horizontal air gap of a needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrode. In order to examine the flashover phenomena and the corona inception voltages caused by flame we measured the voltage and current waveforms when the corona and the flashover was occurred. We also observed, as increasing the applied voltages, the deflection or fluctuation phenomena in the shape of flames caused by the corona wind and the coulomb's force. As the results of an experimental investigation, we found that the reduction of flashover voltages, in comparison with the no-flame case, are 62.7[%] for k=1.0, 34.2[%] for h=5[cm], 27.3[%] for h=7[cm] and 21.4[%] for h=9[cm] when ac voltage is applied.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.603-609
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• 2014

차세대 제트 추진기관으로 주목받고 있는 스크램제트 엔진의 핵심은 연소기 내부에서의 성공적인 초음속 연소를 필요로 한다. 초음속 연소는 공기-연료 혼합(fuel-air mixing)의 정도에 따라 연소효율이 영향을 받게 된다. 공동형 화염 보염기(cavity flameholder)는 재순환 영역(recirculation zone)을 생성하여 연료 혼합의 효율을 높여 지속적인 초음속 연소가 진행될 수 있는 시간을 제공한다. 본 연구에서는 EDISON 전산유체역학 소프트웨어를 이용하여 공동형 화염 보염기를 지나는 초음속 유동의 재순환 영역과 전압력 변화에 대한 전산 해석을 수행하였다. 초기 형상을 생성하여 유동 해석을 수행한 후, 3개의 형상 변수에 대한 매개 변수 연구를 통하여 공동의 형상과 위치에 따른 재순환영역의 제어가 가능함을 확인하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.121-131
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• 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 Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.369-374
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• 2010

This paper presents a numerical investigation of the Deflagration to Detonation Transition (DDT) of flame acceleration by a shock wave in combustible gas mixture. A model consisting of the reactive compressible Navier-Stokes equations is used. The effects of viscosity, thermal conduction, species diffusion, and chemical reactions are included. Using this model, the generation of hot spots by repeated shock and flame interaction in front and back of flame and the change of detonation occurrence by various shock intensities (Ms=1.1, 1.2, 1.3) are studied. The simulations show that as the incident shock intensity increases, the Richtmyer-Meshkov (RM) instability becomes stronger and DDT occurrence time is reduced.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.457-462
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• 2011

This paper presents a numerical investigation of deflagration to detonation transition (DDT) induced by shock wave and flame interaction in ethylene-air mixtures. Also shows the change of DDT triggering time by wall cooling effect. A model is consisted of the compressible reactive Navier-Stokes equations. And the effect of viscosity, thermal conduction, molecular diffusion, chemical reaction and wall effect are included. Using this model, the generation of hot spot by repeated shock and flame interaction, occurrence of detonation, and wall cooling effect of detonation confining boundaries are studied.