• 한국연소학회지
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• 제8권1호
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• pp.36-45
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• 2003

The subject of turbulent premixed flames has been focused by many researchers for a number of decades. Especially, Borghi suggested a magnificent diagram classifying turbulent combustion areas and Lipatnikov and Chomiak modified this diagram. Recently, experimental techniques have been developed so that we can use PIV for measuring 2D velocity field and apply OH PLIF techniques for obtaining flame locations. In present study, a new diagram is proposed using strain rates and OH signal intensity. Thus, simultaneous PIV and OH PLIF measurements are used for shear strain rates and flame locations, respectively. It is believed that the shear strain rates represent flow characteristics such as turbulence intensity and the OH intensity indicates the flame characteristics such as burning velocities.

• 한국자동차공학회논문집
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• 제2권2호
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• pp.124-131
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• 1994

자동차엔진의 연소과정에 상사하는 밀폐정적연소실을 주연소실과 대향 2개 부연소실로 분할하고 오리피스로 연결하였다. 이때 부연소실로부터 주연소실로 분출하는 대향분출염 연소에 의한 질소산화물 배출저감특성을 연소방식, 연소실형상 그리고 연료종류를 변경한 수종의 실험으로 조사하였다. 질소산화물농도, 연소실 최고압력, 화염전파과정의 고속도슐리렌사진 가시화를 수행한 결과, 대향분출염 연소방식을 도입하연 연소실의 중앙부공간이 상대적으로 넓은 경우에 고부하운전과 동시에 질소산화물의 배출량도 저감할 수 있었다. 그러나 연료의 종류는 질소산화물생성에 매우 영향이 적었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.245-246
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• 2012

The possibility that self-ignition can be generated near an obstacle is high in practical applications such as a hydrogen car. In this paper, experimental investigations were suggested to understand the effects of a wall on self-ignition phenomena through high-speed images. The results showed that the existence of a wall could not change the ignition phenomena itself irrespective of wall height and burst pressure. However, when a strong flame was induced in the tube, a wall could promote the flame stabilization.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.1-9
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• 2002

Simultaneous PIV and OH PLIF measurements are used for shear strain rates and flame locations, respectively. It is believed that the shear strain rates represent flow characteristics such as turbulence intensity and the OH intensity indicates the flame characteristics such as burning velocities. However, these are still lack of geometric information, which may be very important to flame quenching Hence, fractal dimensions 'Df) of the OH images are adopted as an additional information. Finally, the flame structure diagram proposed in this research has three parameters, which consist of strain rates, OH intensities and fractal dimensions. The results show that this diagram classifies turbulent premixed flames more effectively based on flame structures. The regime of weak turbulence is limited to narrow strain ranges and has the fractal dimension of about 2 In the regime of moderate turbulence, OH intensities increase as strain rates increase and the values of fractal dimensions are 1.8 Df 1.95. The regimes of thickened reaction and flame extinction (quenching) show bell-shaped and their values of fractal dimensions are 1.5 Df 1.7 and 0.9 Df 0.6, respectively.

• 한국연소학회지
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• 제2권1호
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• pp.17-27
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• 1997

It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

• 한국추진공학회지
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• 제3권3호
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• pp.53-61
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• 1999

충돌제트는 미사일 또는 수직/단거리 이착륙기의 배기가스가 지면이나 화염 편향기 등에 부딪힐 때 발생하며 노즐의 형상, 노즐과 평판과의 거리등에 따라 유동양상이 달라진다. 본 연구에서는 초음속 노즐을 통해 과소 팽창된 제트가 평판에 부딪힐 때 형성되는 평판 압력분포 및 버블 발생 등에 대한 시험결과를 선행된 충격파 풍동을 이용한 시험 결과와 비교하고 초음속 유동시험장치 이용시의 유동 특성을 규명하였다. 초음속 유동시험장치와 충격파 풍동의 평판에서 압력분포는 저압 챔버 내의 수분과 온도 때문에 차이가 나타났고 과소 팽창비에 따른 압력분포는 서로 유사한 경향을 보여주었다.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.11-22
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• 1996

It has been generally accepted that NOx formation increases as the maximum temperature or correspondingly the maximum pressure of a combustion system increases. Recently some exceptional experimental results have been reportes that under certain circumstance NOx formation could be reduced while the maximum pressure was increasing by varying the methods of combustion for the same kind of premixed gases. Until now that kind of results have been acquired only for the case of a dual opposed prechamber. But the mechanism has not been clearly understood yet. 3D computer simulation has been tried to clarify the mechanism. Flor this purpose KIVA-Ⅱ has been modified and applied to the model combustion chamber with which the same kind of experimental works have been done by the authors. A good agreement with the experimental results was achieved with the spatial and temporal resolution which is hard th be obtained by the experimental methods. And it was observed that for the dual opposed prechamber case the time for the NOx formation, which is non-equilibrium reaction, is shorter than any other case by an appropriate mixing process in the main combustion chamber. The shorter time reduceed heat loss through the combustion chamber walls and thereby obtaines the higher maximum pressure.

• 한국연소학회지
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• 제5권1호
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• pp.43-53
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• 2000

Experimental studies on determination of the supply leading time of propellants to combustion chamber have been made to stably and efficiently guarantee the ignition process with liquid rocket engine. The propellant used is a Jet A-1 as fuel and a liquid oxygen as oxidizer. Unlike impinging FOOF type of injectors are arranged radially and the designed O/F ratio is 2.34. The present experiment program also includes the stability on the quadlet type of ignitor using the triethylalumimum as an ignition source and injector life tests. Experimental results clarifies that the propellant supply through LOx leading to combustion chamber is proper for stable ignition and combustion processes based on the fuel and oxidizer manifold pressures, combustion chamber pressure, and the variation of flame length from the nozzle exit with lapse time, and shows that the leading supply time of propellants affects the engine performance little. The effect of positioning cooling holes is remarkable to protect the injector face.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.453-456
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• 2011

합성가스를 이용한 충돌제트 버너에서 신장된 예혼합 화염의 열전달 특성에 관한 실험적 연구를 수행하였다. 본 연구에서는 석탄을 가스화하는 과정에서 추출되는 수소와 일산화탄소를 혼합한 합성가스를 연료로 사용하였다. 정체점에서의 열유속은 전체 신장율이 증가함에 따라 증가하다 다시 감소하는 것이 관찰되었다. 또한 정체점에서의 열유속이 노즐로부터 충돌판까지 거리가 증가함에 따라 증가하는 것을 확인하였다. 본 연구는 석탄에서 발생하는 부생가스의 주성분인 수소와 일산화탄소를 실용화하는 연구 중 기초 연구이다.