• Title/Summary/Keyword: 화염가시화

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A Study of Flow Characteristics by Acoustic Excitation on the Laminar Non-premixed Jet Flame (층류 비예혼합 분류화염에서 음향가진에 의한 유동특성 연구)

  • Oh, Kwang-Chul;Lee, Kee-Man
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.2
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    • pp.160-168
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    • 2010
  • An experimental study has been conducted to investigate the effects of forcing amplitude on the tone-excited non-premixed jet flame of the resonance frequency. Visualization techniques are employed using the laser optic systems, which are RMS tomography, PLIF and PIV system. There are three lift-off histories according to the fuel flow rates and forcing amplitudes; the regime I always has the flame base feature like turbulent flame when the flame lift-off, while the flame easily lift-off in the regime II even if a slight forcing amplitude applied. The other is a transient regime and occurs between the regime I and regime II, which has the flame base like the bunsen flame of partial premixed flame. In the regime I and II, the characteristics of the mixing and velocity profile according to the forcing phase were investigated by the acetone PLIF, PIV system. Particular understanding is focused on the distinction of lift-off history in the regime I and II.

An Experimental Study on the Flashback and Re-ignition Structure with a V-gutter type Flameholder (V-gutter형 보염기에서 발생하는 화염의 역화 및 재점화 구조에 관한 실험적 연구)

  • Jeong, Chan-Yeong;Kim, Tae-Sung;Song, Jin-Kwan;Yoon, Young-Bin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.603-607
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    • 2011
  • Structure of flashback and reignition occurring near flameholder was experimentally investigated in a model combustor with V-gutter flameholder. The combustor has a long duct shape with cross section of $40{\times}40mm$ and City Nature Gas(CNG) were used as fuel. Measurements of chemiluminescence with high speed camera was used for visualization of flame structure. In the lean case, flashback distance depend on equivalent ratio. New flame occurred at the front tip of flameholder when flashback. Flashback flame moved toward downstream direction of combustor because mixture flow velocity had increased, and then re-ignition was caused by entering flow into recirculation zone that is formed behind the flameholder.

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Flame Propagations of Gasoline-Air Mixtures by Electrostatic Discharge Energies (정전기 방전에너지에 따른 가솔린-공기 혼합물의 화염전파)

  • Park, Dal-Jae;Kim, Nam-Il
    • Journal of the Korean Institute of Gas
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    • v.15 no.3
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    • pp.6-10
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    • 2011
  • Experimental studies were carried out to investigate the effects on flame propagation of gasoline-air mixtures by different electrostatic discharge energies in a cylindrical chamber. Three different ignition energies were used: 1 mJ, 50 mJ and 98 mJ. In this work, a high-speed particle image velocimetry technique was applied to visualize the flow-field around ignition electrodes. It was found that as the ignition energy increased, the ignition kernel was different. The different ignition kernel caused different flame initiation. During the flame initiation, the higher ignition energy was applied, the higher flame speed was observed. However, with increasing time, the flame speeds were independent of the ignition energies used. Theses observed flame behaviors were similar to computational simulations shown in the literature. It was also found that as the ignition energies increased, the velocities of unburnt mixtures ahead of propagating flame fronts increased.

In-cylinder Flame Visualization and Flame Propagation Characteristics of SI Engine by using Optimal Threshold Method (Optimal Threshold 법을 이용한 가솔린 기관의 실린더 내화염 가시화 및 화염 전파 특성에 관한 연구)

  • 김진수;전문수;윤정의
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.5
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    • pp.96-104
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    • 2000
  • It is well known that combustion stability under idle and part-load conditions directly affect fuel economy and exhaust emission. In practice, there have been a lot of studies so that a significant improvement in combustion stability has been achieved in this research field. However, applying published results to the development process of mass production engine, there are still many problems which are solved previously. In this study, initial flame behavior and flame propagation characteristic were investigated statistically in order to optimize combustion chamber shapes in the development stage of mass production S.I. engine. To the purpose, the authors applied the flame image capturing system to single cylinder optical engine. The captured flame images were effectively analyzed by using the image processing program which was developed by the authors and adopted new threshold algorithm instead of conventional histogram analysis. In addition, the cylinder pressure was also measured simultaneously to compare evaluated flame results with cylinder pressure data in terms of the combustion characteristics, combustion stability, and cycle-to-cycle combustion variability.

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Research on Turbulent Premixed Flame with Simultaneous PIV/OH PLIF measurements (PIV/OH PLIF 동시측정을 이용한 난류 예혼합 화염 연구)

  • Cho Yong-jin;Kim Ji-ho;Cho Tae-young;Yoon Young-bin
    • 한국가시화정보학회:학술대회논문집
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    • 2002.11a
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    • pp.97-99
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    • 2002
  • Turbulent premixed flames were a subject of many researches for a number of decades. Especially, Borghi suggested a manificent diagram classifying turbulent combustion reasions and Lipatnikov and Chomiak modified this diagram. But this diagram has difficulties tn defining a flame thickness and velocity and measuring integral length scales In addition, recently experimental techniques are being developed, so we can accurately use PIV diagnostics measuring 2D velocity field instead of LDV and make good use of PLIF techniques for obtaining the flame information. In this study, according to developing techniques, suggest a new diagram replacing the existing Borghi diagram. Simultaneous PIV/OH PLIF measurements are used, which measure a shear strain rate and a location of flames, respectively. The shear strain rate represents turbulence and the OH signal indicates the flame information, but there is no geometric Information which is very important to flame quenching. Hence, to consider the geometric information, calculate fractal dimensions of the OH images. So the diagram suggested in this research has three axes which consist of strain rate, OH signal, and fractal dimension and can classify turbulent premixed flames.

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Experimental Study of Thermo-Flow Field in a Model Gas Turbine Combustor with Various Swirl Conditions (스월변화에 따른 모형 가스터빈 연소기의 열유동장의 실험적 연구)

  • Ryu, Song-Youl;Koo, Ja-Ye
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.4
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    • pp.70-76
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    • 2002
  • Characteristics of kerosine spray combustion were investigated at various swirl condition. PDPA(Phase Doppler Particle Analysis) was used to measure the droplet sizes and velocities. R-type(Platinum vs. Platinum-13%rhodium) thermocouple was used to measure the temperature of combustion flow field inside model combustor. A visualization of spray and flame was performed with still camera. As swirl number increases due to increase of swirl vane angle, the spray and the flame were developed to radial direction rapidly. When swirl number is small, the configuration of flame is cone type, but swirl number is large, the configuration of flame is cylindrical type due to enhanced mixing by the transport of swirl momentum.

An Experimental Study of Shock Wave Effects on the Model Scramjet Combustor (모델 스크램제트 연소기에서 충격파 영향에 대한 실험적 연구)

  • 허환일
    • Journal of the Korean Society of Propulsion Engineers
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    • v.3 no.1
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    • pp.65-71
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    • 1999
  • An experimental study was carried out in order to investigate the effect of shock waves on the supersonic hydrogen-air jet flames stabilized in the Mach 2.5 model scramjet combustor. This experiment was the first reacting flow experiment interacting with shock waves. Two identical $10^{\cire}$ wedges were mounted on the diverging sidewalls of the combustor in order to produce oblique shock waves that interacted with the flame. Schlieren visualization pictures, wall static pressures, and combustion efficiency at two different air stagnation temperatures were measured and compared to corresponding flames without shock wave-flame interaction. It was observed that shock waves significantly altered the shape of supersonic jet flames, but had different effects on combustion efficiency depending on air temperatures. At the higher air stagnation temperature and higher fuel flow rates, combustion of efficiency showed a better result.

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A Study on the Diesel Flame by Means of Image Analysis ofn Shadow Photographs (음영사진의 화상해석에 의한 디젤화염에 관한 연구)

  • 장영준;박호준;신본무정
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1222-1233
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    • 1990
  • The formation and oxidation processes of soot particles in a diesel flame were investigated with a rapid compression machine. A cloud of soot particles was successfully visualized by means of the instantaneous laser shadow photographs technique and the equivalence ratio of the soot formation zone was estimated from a measured fuel concentration distribution in a nonevaporating spray. The temporal and spatial variation of soot concentration in the flame was also correlated with the rate of heat release. Soot particles appears first in a region near the flame tip when diffusion combustion period starts, and its concentration is a maximum at about the end of injection, then decreases due to oxidation. The reason for soot being formed in a fuel lean region near the flame tip is the evaporated fuel requires time to be pyrolized as it travels through the burning fuel rich zone towards the flame tip.

Behavioral Change of the Ultrasonic Standing Wave-affected Flame in the Reaction Zone of the Ultrasonically-atomized Kerosene Injected through a Slit-jet Nozzle (Slit-jet 노즐을 통해 분사되는 초음파 무화 케로신 화염의 정상초음파 가진에 의한 거동 변이)

  • Bae, Chang Han;Kang, Yun Hyeong;Ahn, Hyun Jong;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.26 no.1
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    • pp.60-67
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    • 2022
  • A study was conducted to analyze the behavioral change of the kerosene flame ultrasonically-atomized under an ultrasonic standing-wave. Combustion region was visualized through DSLR, ICCD camera and the Schlieren photography with high-speed camera. The fuel consumption was measured by a precise scale. As a result, in the case of ultrasonic standing-wave excitation, it was observed that the intensity of OH radical(OH*) was enhanced and optimal combustion condition was formed around the upper edge of the standing-wave field.

Flame Propagation Characteristics Through Suspended Combustible Particles in a Full-Scaled Duct (이송 배관 내 분진폭발의 화염전파특성)

  • Han, OuSup
    • Korean Chemical Engineering Research
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    • v.47 no.5
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    • pp.572-579
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    • 2009
  • This study is to investigate experimentally the flame structure and propagation mechanism in dust explosions and to provide the fundamental knowledge. Upward propagating laminar dust flames in a vertical duct of 1.8 m height and 0.15 m square cross-section are observed and flame front is visualized using by a high-speed video camera. Also, the thicknesses of preheated and reaction zone have been determined by a schlieren, electrostatic probe and thermocouple. The thickness of preheated zone in lycopodium dust flame is observed to be 4~13 mm, about several orders of magnitude higher than that of premixed gaseous flames. From the experimental results by a PIV(Particle Image Velocimetry) system, a certain residence time of the unburned particle in preheated zone is needed to generate combustible gas from the particle. The residence time will depend on preheated zone thickness, particle velocity and flame propagation velocity.