• Title/Summary/Keyword: Lifted flame

Search Result 120, Processing Time 0.018 seconds

Effect of Electric Fields on Reattachment of Lifted Flame at Low AC Frequency (저주파 교류 전기장 내에서의 부상화염의 재부착 특성에 관한 연구)

  • Kim, Y. K.;Ryu, S. K.;Won, S. H.;Chung, S. H.
    • 한국연소학회:학술대회논문집
    • /
    • 2007.05a
    • /
    • pp.197-201
    • /
    • 2007
  • The reattachment characteristics of propane lifted flames in laminar coflow jets influenced by AC electric fields have been investigated experimentally in low AC frequency range. The reattachment velocity and height have been measured by varying the applied AC voltage and frequency. The results showed that the reattachment of lifted flame occurred at relatively higher jet velocity with AC electric fields, comparing to that without having AC electric fields. The effect of AC electric fields became more effective at higher voltage and lower frequency in the AC frequency range larger than 30 Hz. However, in the low frequency range below 30 Hz, the reattachment velocity decreased with decreasing frequency. Consequently, there existed a transition regime, for the frequency smaller than about 30 Hz. Also, when the AC voltage was applied to the fuel nozzle at very low frequency, the reattachment process exhibited an oscillatory behavior, synchronized with the applied AC frequency.

  • PDF

A Study on Effects of Flame Curvature in Oscillatory Laminar Lifted-flames (진동하는 층류부상화염에서 화염곡률 효과에 관한 연구)

  • Yoon, Sung-Hwan;Park, Jeong;Kwon, Oh-Boong;Yun, Jin-Han;Keel, Sang-In
    • Journal of the Korean Society of Combustion
    • /
    • v.14 no.1
    • /
    • pp.1-8
    • /
    • 2009
  • Experiment is conducted to grasp effects of flame curvature on flame behavior in laminar lifted-jet flames. Nozzle diameters of 0.1 and 1.0mm are used to vary flame curvature of edge flame. There exist three types of edge flame oscillation. These edge flame oscillations may be caused by radial heat loss at all flame conditions, by fuel Lewis numbers near or larger than unity with the help of appreciable radial conduction heat loss, and by buoyancy effects. These are confirmed by the analysis of oscillation frequencies. It is however seen that the change of lift-off height through edge-flame oscillation is mainly due to radial heat loss irrespective of Lewis number and buoyancy.

  • PDF

A Study on the Flame Curvature Characteristics in a Lifted Flame (부상화염에서 화염 곡률반경 특성에 관한 연구)

  • Ha, Ji-Soo;Kim, Tae-Kwon;Park, Jeong;Kim, Kyung-Ho
    • Journal of the Korean Institute of Gas
    • /
    • v.14 no.2
    • /
    • pp.34-39
    • /
    • 2010
  • Flame propagation velocity is the one of the main mechanism of the stabilization of triple flame. To quantify the triple flame propagation velocity, Bilger presents the triple flame propagation velocity through the experiment, depending on the mixture fraction gradient, based on the laminar jet flow theory. However, in spite of these many analyses, there has not been any attempt to quantify the triple flame propagation velocity with the radius of flame curvature. In the present research, a relation of the flame propagation velocity is proposed with the radius of flame curvature for the flame stabilization mechanism. As a result, we have shown that the height of lifted flame is determined with the nozzle diameter and exit velocity of fuel and presented that the radius of flame curvature is proportion to the nozzle exit velocity of fuel and height of lifted flame. Therefore, the importance of the radius of flame curvature has to be recognized. To discribe the flame stabilization mechanism, Bilger's formula has to be modified with flame curvature effect.

Effects of AC Electric Field on the Stability of Laminar Lifted Flame in Coflow Jet (동축류 버너에서 층류 부상화염 안정화의 교류 전기장 효과에 관한 실험적 연구)

  • Park, C.S.;Won, S.H.;Chung, S.H.;Lee, S.M.;Cha, M.S.;Song, Y.H.
    • 한국연소학회:학술대회논문집
    • /
    • 2004.11a
    • /
    • pp.70-75
    • /
    • 2004
  • The effect of electric fields on the stability of non-premixed laminar lifted flame in coflow jets has been investigated by applying high voltage alternative current (AC) to the nozzle of propane fuel. The stable lifted flame which exist in far field of jets, the liftoff height was not effected by applied voltage. This implies that the cold jet between the nozzle and flame base can be analyzed with the previous cold jet theory. Flame liftoff and reattachment velocities were also measured as function of applied voltage and frequency. The fuel jet velocity at flame liftoff and reattachment increased with increasing voltage, implying that the range of flame srability can be extended with the AC charging. However the liftoff velocity increased with frequency of AC charging on nozzle, whereas the reattachment velocity decreases with frequency. The liftoff and reattachment velocities were correlated linearly with voltage considering the effects of frequency.

  • PDF

Effect of Ignition Delay Time on Autoignited Laminar Lifted Flames (자발화된 층류 부상화염에 대한 점화지연시간의 영향)

  • Choi, Byung-Chul
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.35 no.10
    • /
    • pp.1025-1031
    • /
    • 2011
  • Autoignition characteristic is an important parameter for designing diesel or PCCI engines. In particular, diesel spray flames are lifted from the nozzle and the initial flame is formed by an autoignition phenomenon. The lifted nature of diesel spray flames influences soot formation, since air will be entrained into the spray core by the entrainment of air between the nozzle region and the lifted flame base. The objective of the present study was to identify the effect of heat loss on the ignition delay time by adopting a coflow jet as a model problem. Methane ($CH_4$), ethylene ($C_2H_4$), ethane ($C_2H_6$), propene ($C_3H_6$), propane ($C_3H_8$), and normal butane (n-$C_4H_{10}$) fuels were injected into high temperature air, and the liftoff height was measured experimentally. As the result, a correlation was determined between the liftoff height of the autoignited lifted flame and the ignition delay time considering the heat loss to the atmosphere.

Self-excitation of Edge Flame (에지화염의 자기 진동)

  • Park, Jeong;Youn, Sung Hwan;Chung, Yong Ho;Lee, Won June;Kwon, Oh Boong
    • 한국연소학회:학술대회논문집
    • /
    • 2012.11a
    • /
    • pp.167-170
    • /
    • 2012
  • Self-excitations of edge flame were studied in laminar lifted free- and coflow-jet as well as counterflow flames diluted with nitrogen and helium. The self-excitations, originated from variation of edge flame speed and found in the above-mentioned configurations, are discussed. A newly found self-excitation and flame blowout, caused by the conductive heat loss from premixed wings to trailing diffusion flame are described and characterized in laminar lifted jet flames. Some trials to distinguish Lewis-number-induced self-excitation from buoyancy-driven one with O(1.0 Hz) are introduced, and then the differences are discussed. In counterflow configuration, important role of the outermost edge flame in flame extinction is also suggested and discussed.

  • PDF

An Experimental Study on the Lift-off Behavior of Tone-Excited Propane Non-premixed Jet Flames (음향 가진된 프로판 비예혼합 제트 화염의 부상 거동에 대한 실험적 연구)

  • Kim, Seung-Gon;Kim, Kang-Tae;Park, Jeong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.28 no.5
    • /
    • pp.569-579
    • /
    • 2004
  • The lift-off characteristics of lifted laminar propane jet flames highly diluted with nitrogen are investigated introducing acoustic forcing with a fuel tube resonance frequency. A flame stability curve is obtained according to forcing strength and the nozzle exit velocity for N2 diluted flames. Flame lift-off behavior is globally classified into three regimes; 1) a weakly varying partially premixed behavior caused by a collapsible mixing for large forcing strength, 2) a coexistent behavior of the edge flame and a weakly varying partially premixed behavior for moderate forcing strength, and 3) edge flame or triple flame behavior for small forcing. It is shown that the laminar lifted flame with forcing affects flame lift-off behavior considerably, and is also clarified that the flame characteristic of flame base is well described with the penetration depth of the degree of mixing, ${\gamma}$$\_$$\delta$/. It is also confirmed that the weakly varying partially premixed flame caused by a collapsible mixing fur large forcing strength behaves as that just near flame blow-out in turbulent lift-off flame.

Characteristics of Interacting Lifted Flames (상호작용하는 부상화염의 특성에 관한 연구)

  • Lee, Seung;Lee, Byeong-Jun
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.25 no.4
    • /
    • pp.461-466
    • /
    • 2001
  • The characteristics of nonpremixed interacting flames are investigated in the parameter of nozzle configuration and nozzle separation distane, s. Three nozzle arrangements - diamond 4 nozzle, linear 5 nozzle and cross 5 nozzle- are used. When s is about 10 nozzle diameter, flames lift from the nozzle at the highest fuel flowrate compared with the other s cases. Normally flames are extinguished at the lifted states. Flowrates when blowout occurs are affected by the nozzle configuration, nozzle seperation distance. Blowout flowrates for the diamond- or cross-shaped nozzle cases are parabolic function of s. For 5 cross nozzle case, flames extinguished at 3.3 times higher flowrate than that of single equivalent area nozzle. Turbulent liftoff heights are not function of flowrates for these cases.

A Behavior of the Ultrasonically-atomized Kerosene Lifted-flame According to the Position of Ultrasonic Standing-wave Field (정상초음파장의 위치에 따른 초음파 무화 케로신 부상화염의 거동)

  • Chang Han Bae;Jeong Soo Kim
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.27 no.1
    • /
    • pp.1-8
    • /
    • 2023
  • A study was conducted to scrutinize the behavior of the ultrasonically-atomized kerosene lifted-flame according to the carrier gas flow-rate and position of ultrasonic standing wave (USW). The combustion region of the kerosene-aerosol generated through a slit-jet nozzle was visualized using a DSLR, ICCD, high-speed camera, and Schlieren technique, and the fuel consumption was measured by using a precision balance. As a result, the flame was confined within the region bounded by the USW-field, and the fuel consumption decreased as the position of the USW field increased.

Effects of Flow Excitation on the Nitrogen Oxide Emission of a Non-Premixed Flame (유동장 자극이 화염의 질소산화물 배출에 미치는 영향)

  • 이기만
    • Fire Science and Engineering
    • /
    • v.18 no.2
    • /
    • pp.34-40
    • /
    • 2004
  • The effects of external flow excitation with various frequencies and amplitudes on the flame behavior and pollution emission characteristics from a laminar jet flame are experimentally investigated. Measurements of $NO_x$ emission indices ($EINO_x$), performed in vertical lifted flame like turbulent with various exciting amplitude at a constant resonance frequency, have been conducted. It was also conducted to investigate the effects of excited frequency at a constant exciting amplitude on $NO_x$ emissions with a various frequency ranged 0 Hz to 2 KHz. From the vertical lifted turbulent flame of the excited jet with resonance frequency by strong excitation was shown that the dependence of $NO_x$ emission could be categorized into three groups Group I of long flame length with high disturbances yielding high $NO_x$ emission, Group II of intermediate flame length and relative narrow flame volume with low disturbance yielding low $NO_x$ emission and Group III of long flame length and large flame volume with high time & space disturbances behaviour yielding high $NO_x$ emission.