• 제목/요약/키워드: Lewis number induced self-excitation

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층류 동축류 제트 부상화염에서 부력에 의한 자기진동과 루이스 수에 의한 자기진동 비교에 관한 실험적 연구 (Experimental Study on Comparison between Buoyancy Driven and Lewis Number Induced Self-excitations in Laminar Lifted Coflow-jet Flames)

  • 이원준;박정;권오붕;윤진한;길상인
    • 한국연소학회지
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    • 제19권2호
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    • pp.21-27
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    • 2014
  • Experimental study in laminar propane coflow jet flames has been conducted to investigate self-excitations. For various propane mole fractions and jet velocities, two types of self-excitation were observed: (1) buoyancydriven self-excitation (hereafter called BDSE) and (2) Lewis-number-induced self-excitation coupled with (1) (hereafter called LCB). The mechanism of Lewis-number-induced self-excitation (hereafter called LISE) is proposed. When the system $Damk\ddot{o}hler$ number was lowered, LISE was shown to be launched. The LISE is closely related to heat loss, such that it can be launched in even helium-diluted methane coflow-jet flame (Lewis number less than unity). Particularly, The LISE becomes significant as the $Damk\ddot{o}hler$ number decreases and heat-loss is excessively large.

층류 동축류 제트 부상화염에서 부력에 의한 자기진동과 루이스 수에 의한 자기진동 비교에 관한 실험적 연구 (Experimental Study on Comparison of Buoyancy Driven and Lewis Number Induced Self-excitations in Laminar Lifted Coflow-jet Flames.)

  • 반규호;이원준;박정;길상인;윤진한;임인권
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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    • pp.367-369
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    • 2014
  • A study on laminar coflow jet flames diluted with helium and nitrogen has been conducted to investigate self-excitations. The stability map was provided with a function of nozzle exit velocity and fuel mole fractions of propane or methane. The results show that there exist three types of self-excitations; (1) buoyancy-driven self-excitation (BDSE), (2) Lewis number induced self-excitation coupled with buoyancy (LCB) and (3) Lewis number induced self-excitation (LISE).

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층류 동축류 제트 부상화염에서의 자기진동에 관한 실험적 연구 (A study on Self-excitations in Laminar Lifted Coflow-jet Flames)

  • 반규호;이원준;박정;길상인;윤진한;임인권
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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    • pp.129-132
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    • 2014
  • A study on laminar coflow jet flames diluted with helium and nitrogen has been conducted to investigate self-excitations. The stability map was provided with a function of nozzle exit velocity and fuel mole fractions of propane or methane. The results show that there exist three types of self-excitations; (1) buoyancy-driven self-excitation (BDSE), (2) Lewis number induced self-excitation coupled with buoyancy (LCB) and (3) Lewis number induced self-excitation (LISE).

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층류 동축류 제트 부상화염에서의 자기진동에 관한 연구 (A Study on Self-excitation in Laminar Lifted Coflow-jet Flames)

  • 반규호;이원준;박정;김태형;박종호
    • 한국연소학회지
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    • 제20권1호
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    • pp.43-51
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    • 2015
  • A study on laminar jet flames in coflow air diluted with helium has been conducted to investigate self-excitations for various propane mole fractions and nozzle exit velocities. The stability map was represented as a function of nozzle exit velocity and fuel mole fraction for propane. The results show that two types of self-excitation were observed : (1) buoyancy-driven self-excitation (hereafter called BDSE) and (2) Lewis-number induced-self-excitation coupled with (1) (hereafter called LCB) near extinction limit for 9.4 mm nozzle diameter. It was shown that with 0.95 mm nozzle diameter, Lewis-number-induced self-excitation (hereafter LISE) and BDSE could be separated. The differences between the two self-excitations were shown and discussed.

층류 동축류 제트에서 공기측 헬륨 희석이 화염진동에 미치는 영향 (Helieum-dilution Effect of Coflow Air on Self-excitation in Laminar Coflow Jet Flames)

  • 이원준;박정;권오붕;백세현;고성호
    • 한국연소학회지
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    • 제17권4호
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    • pp.51-59
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    • 2012
  • Experimental study in coflow jet flames has been conducted to investigate the helium-dilution effect of coflow air on self-excitation. For various helium mole fractions and jet velocities, two types of self-excitation were observed: buoyancy-driven self-excitation and Lewis-number-induced self-excitation(here after called Le-ISE) coupled with buoyancy-driven one. The difference between buoyancy-driven and Le-ISE is clarified by using the Mie-scattering visualization as well as exploring the different features. The mechanism of Le-ISE is proposed. When the system Damk$\ddot{o}$hler number was lowered, Le-ISE is shown to be launched. Le-ISE is closely related to heat loss, in that it can be launched in even methane jet flame (Lewis number less than unity) with helium-diluted coflow air. Particularly, Le-ISE becomes significant as the Damk$\ddot{o}$hler number decreases and heat-loss becomes significant.

에지화염의 자기 진동 (Self-excitation of Edge Flame)

  • 박정;윤성환;정용호;이원준;권오붕
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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    • pp.167-170
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    • 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.

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질소 희석된 프로판 자유제트 층류부상화염에 있어서 화염 자기진동 특성에 관한 연구 (Study of Characteristics of Self-Excitation in Lifted Laminar Free-Jet Propane Flames Diluted with Nitrogen)

  • 윤성환;박정;권오붕;배대석
    • 대한기계학회논문집B
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    • 제34권4호
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    • pp.399-408
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    • 2010
  • 질소 희석된 프로판 층류 부상 화염에서 화염진동 불안정성과 화염 곡률 효과를 살펴보기 위하여 실험적 연구를 수행하였다. 화염 진동은 총 3가지 영역으로 열손실에 의한 진동, 열손실 및 부력이 혼재된 진동, 그리고 열손실 및 루이스 수에 의한 영향이 혼재된 진동으로 구분되었다. 순수 열손실에 의한 진동은 루이스 수에 의한 진동과 부력에 의한 수력학적 불안정성과 관련이 없으며 연료 루이스 수에 관계없이 모든 부상화염 조건에서 관찰되었다. 화염의 시간에 따른 부상높이 변화에 대한 FFT분석을 통해 화염진동 불안정성의 실험적 증거와 특성을 명확히 제시하였고, 부상 화염의 열손실에 의한 자기진동의 메커니즘에 대한 시나리오를 논의한다.

직류 전기장을 인가한 층류부착화염에서 물질-열 확산 및 부력에 의한 화염진동 비교에 관한 연구 (Diffusive-Thermal Instability and Buoyancy-Driven Instability in Laminar Attached Free-jet Flames with DC Electric Fields)

  • 한종규;윤성환;박정;윤진한;길상인;서상일;김영주
    • 한국연소학회지
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    • 제16권3호
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    • pp.41-51
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    • 2011
  • In this paper, we describe the behavior of two self-excitations in laminar attached free-jet flames under the influence of DC electric fields, one of buoyancy-driven and the other of diffusion-thermal instability, established from the horizontal and vertical injection. In the horizontal injection with removed buoyancy effect, oscillating flames with the frequency of 1.3 - 7.4 Hz were observed in a certain condition with Lewis number more than unity. On the other hand, it was appeared Lewis number induced self-excitation as well as buoyancy-driven self-excitation in the vertical upward injection with DC electric fields. This behavior had frequency range of 1.6 - 9.4 Hz and was exhibited to attribute the buoyancy effect. Finally, a well-defined division about two self-excitations having similar frequency range is briefly discussed.