• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.187-194
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• 2004

The surface flames in porous ceramic burner are experimentally characterized to investigate the effects of equivalence ratio and firing rates. The results show that the surface flames are classified into green, red radiant and blue surface flame as the decrease of equivalence ratio. And each flame is maintained very stable and represents the same flame characteristics at any orientation of ceramic burner. Particularly the blue surface flame is found to be very stable at very lean equivalence ratio at 7000kcal/hr to 20000kcal/hr firing rates. And the exhausted NOx was analysed to find out which flame has lower NOx emission. The blue surface flame shows the lowest NOx emission regardless of the location of burner since it sustains very stable at lean mixture ratio.

• Journal of the KSME
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• v.25 no.3
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• pp.236-241
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• 1985

본 고에서는 일반적으로 노즐 부위 열해석에서 무시되는 복사열전달율과 점성소산효과를 수치적 모델을 통하여 그 필요성 여부를 조사한 것이며 다음과 같은 결론을 얻었다. (1)연소실 및 수 렴부위에서는 복사열전달율이 대류열전달율과 같은 차수의 크기로 나타나고 있어서 고 복사율을 갖는 연소가스에서는 특히 중요하다. 특히 최근에 많이 사용되는 연료에는 연소가스에 산화알 루미늄 성분이 증가하는 추세이므로 노즐부위 열해석에는 복사열전달이 차지하는 비중이 커질 것이다. (2)노즐의 확산부위에서는 고속으로 인하여 가스자체의 점성소산이 일어나 특성치 보 정계수 값이 감소한다. 따라서 Bartz의 예측치 보다는 열전달계수의 값이 적어지고 있다. (3) 따라서 노즐수렴부위에서는 일반적으로 Bartz의 예상치보다 높고 확산부에서는 낮은 결과를 얻 었던 실험결과와를 비교할 때 고온고속 노즐에서의 열전달해석은 복사 열전달과 점성열 소산을 고려함으로써 정확하게 될 수 있다. (4)이상 고려된 실험 데이터와 수치모델의 고찰은 노즐내의 침식이 없는 경우이나 실제의 경우 노즐벽 표면에서 화학적 반응이 일어난다. 그러나 이때 발 생될 수 있는 순수한 발한효과는 미미하며 단지 전체적인 단면의 열 해석시 상기에서 예측된 열전달율을 근간으로 화학반응열 및 온도분포를 계산하여야 할 것이다.

• Journal of the KSME
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• v.56 no.9
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• pp.38-43
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• 2016

초임계 난류유동이 활용되고 있는 가장 대표적인 시스템은 액체로켓연소기이다. 액체로켓엔진은 목적하는 임무에 따라 추력이 결정되고 엔진의 추력이 결정된다. 이러한 추력을 결정하는 핵심부품이 분사기(injector)이다. 실용 인공위성을 발사하기 위한 액체로켓엔진의 연소기는 수백 개의 분사기를 통해 연료와 산화제가 혼합되는 구조를 가지고 있다. 따라서 로켓연소기의 연소특성 및 성능은 분사기의 혼합특성에 좌우된다. 그러므로 단일 분사기의 연료/산화제 혼합특성에 대한 많은 실험과 해석연구가 진행되고 있다. 그런데 초임계압력에서는 액체의 표면장력이 사라지게 되어 독특한 혼합특성을 가지고 있기 때문에 성능을 높여주기 위하여 초임계 압력을 선택할 경우 분사기에 대한 연구가 선행되어야 한다. 이 글에서는 이러한 초임계 작동압력에서 분사기에 대한 연구들을 소개하고자 한다.

• Journal of the Korean Society of Combustion
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• v.6 no.1
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• pp.29-35
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• 2001

The surface flames in porous ceramic burner are experimentally characterized to investigate the effects of equivalence ratio and firing rates. The results show that the surface flames are classified into green, red radiant and blue surface flame as decrease of equivalence ratio. And each flame is maintained very stably and shows the same flame characteristics at any orientation of ceramic burner. Particularly the blue surface flame was found to be very stable at very lean equivalence ratio at 200 to $800\;kw/m^2$ firing rates. And the exhausted NOx was analysed to find out which flame has lower NOx emission. The blue surface flame showed the lowest NOx emission regardless of the location of burner since it sustained very stable at lean mixture ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.774-779
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• 2009

A numerical modelling was performed to predict unsteady combustion processes for the AP/HTPB/Al propellant in a solid rocket motor. Its results were compared with the experimental data. Temporal pressure development was found to match quite well with measured data. A change in propellant surface was traced using the moving grid. The propellant thickness change was also observed to confirm the erosive burning effect.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.11a
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• pp.35-36
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• 2013

2차 화염확산체로서의 역할을 할 수 있는 일반 유기폼 침대 매트리스에 착화된 연소성상을 고찰하며 특히 표면 화염확산(flame spread)에 대해서 장방향 및 단방향에 대한 확산속도를 분석함.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.56-56
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• 2008

연소화학증착법(CCVD)를 이용해 IN738LC 합금에 $SiO_2$ 보호피막 코팅을 행하였다. 소스물질인 TEOS 첨가량과 증착 시간을 변화시키면서 $SiO_2$ 보호피막을 제조하였다. 증착된 코팅층은 SEM, EDX, XPS 분석을 통해 $SiO_2$층임 을 확인하였고 TGA(Thermogravimetric analysis)를 이용하여 합금의 내산화 특성을 평가하였다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.166-170
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• 2010

Six different size of torch-ignition device were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The torch-ignition device was designed six different volumes and same orifice size. The combustion pressures were measured to calculate the mass burn fraction and combustion enhancement rate. In addition, the flame propagations were visualized by shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burn fraction were increased when using the torch ignition device. And the combustion duration were decreased. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition device the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage. And the initial flame propagation was effected torch-ignition volume.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.40-47
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• 2013

The similarity in internal flow of solid and hybrid rocket suggests that hybrid rocket combustion can be susceptible to instability due to vortex sheddings and their interaction. This study focuses on the evolution of interaction of vortex generated in pre-chamber with other types of vortex in the combustor and the change of combustion characteristics. Baseline and other results tested with disks show that there are five different frequency bands appeared in spectral domain. These include a frequency with thermal lag of solid fuel, vortex shedding due to obstacles such as forward, backward facing step and wall vortices near surface. The comparison of frequency behavior in the cases with disk 1 and 3 reveals that vortex shedding generated in pre-chamber can interact with other types of vortex shedding at a certain condition. The frequency of Helmholtz mode is one of candidates resulting to a resonance when it was excited by other types of oscillation even if this mode was not discernable in baseline test. This selective mechanism of resonance may explain the reason why non-linear combustion instability occurs in hybrid rocket combustion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.363-368
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• 2010

In the solid rocket propellant combustion, the dynamic phase change from solid to liquid to vapor occurs across the melt layer. During the surface burning, liquid and gas phases are mixed in the intermediate zone between the propellant and the flame to form micro scale bubbles. The known thickness of the melt layer is approximately 1 micron at $10^5$ Pa. In this paper, we present a model of the melt layer structure and the dynamic motion of the melt front derived from the classical phase field theory. The model results show that the melt layer grows and propagates uniformly according to exp(-1/$T_s$) with $T_s$ being the propellant surface temperature.