• 제목/요약/키워드: Turbulent Flame Speed

검색결과 50건 처리시간 0.02초

동축류 제트에서 초기 온도 변화에 따른 난류 부상화염 특성 (Characteristics of Turbulent Lifted Flames in Coflow Jet with Initial Temperature Variations)

  • 김길남;원상희;정석호
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
    • /
    • pp.15-20
    • /
    • 2004
  • Characteristics of turbulent lifted flames in coflow jet have been investigated by varying initial temperature through the heating of coflow air. In the turbulent regime, liftoff height increases linearly with fuel jet velocity and decreases nonlinearly as the coflow temperature increases. This can be attributed to the increase of turbulent propagation speed, which is strongly related to laminar burning velocity. Dimensionless liftoff heights are correlated well with dimensionless jet velocity, which are scaled with parameters determining local flow velocity and turbulent propagation speed. This implies that the turbulent lifted flames are stabilized by balance mechanism between local turbulent burning velocity and flow velocity. Blowout velocity can be obtained from the ratio of mixing time to chemical time. Comparing to previous researches, thermal diffusivity should be evaluated from the initial temperature instead of adiabatic flame temperature.

  • PDF

동축류 제트에서 초기 온도 변화에 따른 난류 부상화염 특성 (Characteristics of Turbulent Lifted Flames in Coflow Jet with Initial Temperature Variations)

  • 김길남;원상희;정석호
    • 한국연소학회지
    • /
    • 제9권1호
    • /
    • pp.32-38
    • /
    • 2004
  • Characteristics of turbulent lifted flames in coflow jet have been investigated by varying initial temperature through the heating coflow air. In the turbulent regime, liftoff height increases linearly with fuel jet velocity and decreases nonlinearly as the coflow temperature increases. This can be attributed to the increase of turbulent propagation speed, which is strongly related to laminar burning velocity. Dimensionless liftoff heights are correlated well with dimensionless jet velocity, which are scaled with parameters determining local flow velocity and turbulent propagation speed. This implies that the turbulent lifted flames are stabilized by balance mechanism between local turbulent burning velocity and flow velocity. Blowout velocity can be obtained from the ratio of mixing time to chemical time. Comparing to previous researches, thermal diffusivity should be evaluated from the initial temperature instead of adiabatic flame temperature.

  • PDF

정적연소기내 유동형태가 화염전파에 미치는 영향 연구 (An Experimental Study of the Effect of Flow on Flame Propagation in a Constant-Volume Combustion Chamber)

  • 정동수;오승묵;서승우;장영준
    • 한국자동차공학회논문집
    • /
    • 제3권2호
    • /
    • pp.136-145
    • /
    • 1995
  • The aim of this study is to gain a better understanding of the effect of a flow motion on the flame development by means of an optically-accessible constant-volume combustion chamber and the visualization technique of a combustion flame. At first, the characteristics of a flame propagation are investigated in the combustion field of the two kinds of flow conditions such as a quiescent and a flowing condition, and methane-air mixture is used as fuel. Then the same investigation is performed in two flow configurations : bulk flow motion type and turbulence generating type. In this study, the combustion phenomena are analyzed by measuring the combustion pressure, flame propagation speed, mean velocity, turbulent intensity, and mass fraction burned.

  • PDF

DOHC 가솔린기관의 연소실 난류특성이 기관성능에 미치는 영향에 관한 연구 (A Study on the Influence of Turbulent Intensity on DOHC Engine Performance)

  • 김철수;최영돈
    • 한국자동차공학회논문집
    • /
    • 제2권2호
    • /
    • pp.12-23
    • /
    • 1994
  • In order to investigate the effect of turbulent intensity on combustion characteristics, new flame factor model was developed. The principal study is the evaluation of interaction of swirl, tumble and unstrutural component of flow characteristics and correlation between turbulent intensity and flame factor. Computational and experimental study has been, performed such as quasi-dimensional cycle simulation, three dimensional flow analysis, engine performance test and diagnostic simulation. From these studies, it was found that flame factor was a function of engine speed and turbulent intensity.

  • PDF

예혼합 난류화염구조에 미치는 레이놀즈 수와 담퀠러 수의 영향에 관한 연구 (A Study on the Effects of Reynolds Number and Damkohler Number in the Structure of Premixed Turbulent Flames)

  • 김준효;안수길
    • Journal of Advanced Marine Engineering and Technology
    • /
    • 제19권4호
    • /
    • pp.34-41
    • /
    • 1995
  • The structure of premixed tubulent flames in a constant-volume vessel was investigated using a schlieren method and microprobe method. The schlieren method was used to observe the flame structure qualitatively. The microprobe method, which detects a flamelet by detecting its flame potential signal, was used to investigate the deeper flame structure behind the flame front. The flame potential signal having one to six peaks was obtained in the case of turbulent flames, each of them being regarede as a flamelet existing in the flame zone. Based on this consideration, the flame propagation speed, the thickness of the flame zone, the number of flamelets and the separation distance between adjacent flamelets in the flame zone were measured. Moreover, the thickness of flamelet which could not be attempted in the conventional electrostatic probe method was also investigated. The experimental results of this work suggest the existence of "reactant islands" in the reaction zone, and show that the averaged number of flamelets increases with an increase in the turbulence intensity and/or a decrease in the Damkohler number. The mean thickness of flamelet in the case of turbulent flames was found to be about two times compared to laminar values.ar values.

  • PDF

고속카메라를 이용한 디젤엔진내의 화염 가시화, 화염의 온도 및 매연 측정에 관한 연구 (A Study on the Measurement of Flame Visualization, Temperature and Soot for Diffusion Flame in a Diesel Engine Using High-Speed Camera)

  • 한용택;이기형
    • 대한기계학회논문집B
    • /
    • 제31권2호
    • /
    • pp.132-140
    • /
    • 2007
  • The temperature and soot of the visualized diesel engine's turbulent flow of the flame was measured qualitatively. In the combustion chamber, in order to judge the affect that the swirl current has on the current ratio two heads with different ratios were used. Using a high speed camera, the results were analyzed using flame visualization. In order to measure the temperature and soot of the turbulent flames like diesel flames, two color methods were used to acquire temperature and the soot of the flames according to the conditions through analyzing the two wavelengths of the flames. It was possible to measure the highest temperature of the non-swirl head visualized engine, which is approximately 2400K, and that swirl head engine managed up to 2100K. With respect to the visualized diesel engine soot, we got the grasp of the KL factor which bears the qualitative information of the soot. This study is dedicated to suggesting the possibility of measuring not only the temperature but also soot of the diffusion flame of the diesel engine turbulent flames.

스월 난류연소기의 흡입공기온도, 스월세기에 따른 연소불안정 발생 메커니즘에 대한 연구 (A study on flame bifurcation due to inlet mixture temperature and swirl strength in a swirl turbulent combustor)

  • 김종찬;성홍계;유혁
    • 한국추진공학회:학술대회논문집
    • /
    • 한국추진공학회 2007년도 제29회 추계학술대회논문집
    • /
    • pp.377-380
    • /
    • 2007
  • 스월 난류연소기에서의 혼합기 유입온도와 스월세기에 따른 연소불안정 발생 메커니즘 알아보기 위하여 Large Eddy Simulation을 수행하였다. 스월각 45도 경우 연료공기 혼합기의 온도를 600K에서 660K으로 증가시켰을 경우 화염분기(Bifurcation)현상이 관찰되었고, 스월 강도가 변할 경우 온도와 관계없이 화염분기가 일어나거나 그렇지 않음을 확인하였다. 벽면근처의 혼합가스 유동속도와 화염속도간의 상관관계는 화염분기현상의 발생에 주요한 인자임을 확인하였다.

  • PDF

프로판-공기 예혼합기의 화염전파 과정에 관한 연구 (Flame Propagation Characteristics of Propane-Air Premixed Mixtures)

  • 배충식
    • 한국연소학회지
    • /
    • 제1권2호
    • /
    • pp.21-29
    • /
    • 1996
  • Flame propagation characteristics of propane-air mixtures were experimentally investigated in constant-volume combustion chambers. Flame propagation process was observed as a function of mixture strength, initial mixture temperature and initial mixture pressure in quiescent mixtures. A cylindrical combustion chamber and a spherical combustion chamber contain a pair of parallel windows through which optical access into the chamber can be provided. Laser two beam deflection method was adopted to measure the local flame propagation, which gave information on the flame size and flame propagation speed. Pressure development was also measured by a piezoelectric pressure transducer to characterize combustion in quiescent mixtures. Burning velocity was calculated from flame propagation and pressure measurements. The effect of flow on flame propagation was also investigated under flowing mixture conditions. Laser two beam method was found to be feasible in measuring flame propagation of quiescent mixtures. Flame was observed to propagate faster with higher initial mixture temperature and lower initial pressure. Combustion duration was shortened in the highly turbulent flowing mixtures.

  • PDF

난류 부분예혼합화염과 로테이팅 아크 플라즈마를 이용한 난연성 유증기의 연소처리 (Reduction of Lean VOC Emission by Reforming with a Rotating Arc Plasma and Combustion with a Turbulent Partially-Premixed Flame)

  • 안태국;이대훈;박선호
    • 한국연소학회지
    • /
    • 제22권1호
    • /
    • pp.23-31
    • /
    • 2017
  • Large-scale fuel tanks emit massive amount of hardly-combustible VOC mixtures which are light hydrocarbon species in dilution with nitrogen and carbon dioxide. We have developed a lab-scale burner to combust those VOC mixtures by use of a turbulent partially-premixed flame as a pilot flame. For a higher HC treatment ratio, the mixture gases were reformed by a rotating arc plasma device. The results showed that the nitrogen mole fraction and the injecting speed of the VOC mixture influence on the performance of the burner. It was also found that the size of the pilot flame and the power supplied to the plasma device determine the overall HC treatment ratio and the concentrations of CO and NOx in the exhaust gas.

혼합기의 유동 및 점화조건에 따른 초기화염의 전파특성 (The influence of Mixture Flow and the Ignition Conditions on the Initial Flame Propagation Characteristics)

  • 김진영;이중순;하종률
    • 한국자동차공학회논문집
    • /
    • 제7권6호
    • /
    • pp.57-64
    • /
    • 1999
  • Initial flame development and propagation were visualized under the new ignition system developed to estimate the effects of ignition characteristics on the engine performance in a port injection SI engine. Effects of intake air flow characteristics were also investigated by three different kinds of the swirl control valve. Experiments were performed in an optical single cylinder engine modified form a commercial engine. Flame images were captured through the quartz window mounted in the piston by the high speed video camera and analyzed to compare initial flame development. Results show that IMEP tends to rise slightly as the ignition duration gets longer. The direction of flame propagation is decisively governed by the in-cylinder flow motion. Every flame grows toward the exhaust valve forming a kind of turbulent flame. Initial flame propaagation characteristics are very similar to ones analyzed form pressure data.

  • PDF