• 제목/요약/키워드: Counterflow Diffusion Flame

검색결과 82건 처리시간 0.024초

Crossed Twin Jet Counterflow에서의 소염과 재점화 특성 (On the Characteristics of Extinction and Re-ignition in a Crossed Twin Jet Counterflow)

  • 이범기;양승연;정석호
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
    • /
    • pp.25-31
    • /
    • 2002
  • For the better understanding of the stability of turbulent combustion, more researches on extinction and re-ignition are needed. Flame interactions in non-premixed flame have also not been greatly researched. We made a hybrid twin jet flame, the combinations of diffusion flame and partially-premixed diffusion flame, in a twin jet counterflow configuration. The extinction limits of a crossed twin jet counterflow have been extended in comparison with those of a one-dimensional counterflow because of flame interactions through heat transfer and joint ownership of various radicals. Besides, we have obtain ignition $Damk\"{o}hler$ number by experimental method without external ignition source using the extinction characteristic in a crossed twin jet counterflow flame. From results, we can identify the hysteresis between extinction and ignition $Damk\"{o}hler$ number in S-curve.

  • PDF

대향류 화염의 비정상 거동에 대한 연구 (Unsteady behavior of counterflow flame)

  • 이기호;이은도;오광철;이춘범;신현동
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
    • /
    • pp.33-39
    • /
    • 2002
  • Unsteady behaviors of counterflow flame were studied experimentally in opposing jet counterflow burner using diluted methane. To generate the unsteadiness on the flame, the counterflow diffusion flame was perturbed by velocity changes made by the pistons installed on both sides of the air and fuel stream. The velocity changes were measured by Hot wire and Laser Doppler Velocimetry, and the flame behaviors were observed by High speed ICCD and ICCD. In this investigation, the spatial irregularity of the strain rate caused the flame to extinguish from the outside to the axis during the extinction, and we found the following unsteady phenomena. First, the extinction strain rates of unsteady cases are much larger than those of the steady ones. Second, the extinction strain rates become larger as the slope of the change of the strain rate increases. Third, the unsteady extinction strain rates become smaller with the increase of the initial strain rate.

  • PDF

A Numerical Study on Methane-Air Counterflow Diffusion Flames Part 1. Concentration of Fuel

  • Park, Woe-Chul
    • International Journal of Safety
    • /
    • 제2권1호
    • /
    • pp.7-11
    • /
    • 2003
  • Structure of the counterflow nonpremixed flames were investigated by using Fire Dynamics Simulator(FDS) and OPPDIF to evaluate FDS for simulations of the diffusion flame. FDS, employed a mixture fraction formulation, were applied to the diluted axisymmetric methane-air nonpremixed counterflow flames. Fuel concentration in the mixture of methane and nitrogen was considered as a numerical parameter in the range from 20% to 100% increasing by 10% by volume at the global strain rates of $a_g = 20S^{-l} and 80S^{-1}$ respectively. In all the computations, the gravity was set to zero since OPPDIF is not able to compute the buoyancy effects. It was shown by the axisymmetric simulation of the flames with FDS that increasing fuel concentration increases the flame thickness and decreases the flame radius. The centerline temperature and axial velocity, and the peek flame temperature showed good agreement between the both methods.

예혼합 및 대향류확산 화염에서 NO의 생성에 미치는 소반응의 역할 (Roles of Key Elementary Reaction for NO Formation in Premixed Flame and Counterflow Diffusion Flame)

  • 최낙정;윤석범
    • Journal of Advanced Marine Engineering and Technology
    • /
    • 제22권1호
    • /
    • pp.108-116
    • /
    • 1998
  • In this paper it is investigated the roles of key elementary reactions for NO formation in methane-air one-dimensional premixed flame and counterflow diffusion flame, which were studied numerically by using NO kinetics and $C_{2}$ -chemistry complied by Miller and Bowman. The spatial distributions of the reaction rates of 9 main elementary reactions directly related to NO formation and destruction were calculated. Integration of the rates of all reactions in the NO formation across the flame yields the quantitative reaction path diagram, which shows clearly relative importance of each reaction path in NO formation and how it changes with the type and parameters of the flame. The results show that the thermal and Fenimore mechanisms are dominant respectively for learn and rich premixed flames, and the latter is dominant for diffusion flames. In addition, it was found that the HCN recycle route is important for diffusion flame, and that the routes of mutual transformation between NO and NO$^{2}$, and between NO and HNO do not contribute to the net NO formation.

  • PDF

A Numerical Study on Methane-Air Counterflow Diffusion Flames Part 2. Global Strain Rate

  • Park, Woe Chul
    • International Journal of Safety
    • /
    • 제2권1호
    • /
    • pp.12-16
    • /
    • 2003
  • In Part 1, the flame structure of the counterflow nonpremixed flames computed by using Fire Dynamics Simulator was compared with that of OPPDIF for different concentrations of methane in the fuel stream. In this study, comparisons were made for the global strain rate that is an important parameter for diffusion flames for further evaluation of FDS. At each of the three fuel concentrations, $20% CH_4+ 80% N_2, 50% CH_4 + 50% N_2, 90% CH_4 + 10% N_2$ in the fuel stream, the temperature and axial velocity profiles were investigated for the global strain rate in the range from 20 to $100s^{-1}$. Changes in flame thickness and radius were also compared with OPPDIF. There was good agreement in the temperature and axial velocity profiles between the axisymmetric simulations and the one-dimensional computations except for the regions where the flame temperature reach its peak and the axial velocity rapidly changes. The simulations of the axisymmetric flames with FDS showed that the flame thickness decreases and the flame radius increases with increasing global strain rate.

분류 및 대향류 확산 소화염의 구조 및 NOx 생성특성 비교 검토 (A Study on Structures and NOx Formation Characteristics in Coflow and Counterflow Diffusion Flamelet)

  • 오창보;김종수;이창언;이기만
    • 한국연소학회지
    • /
    • 제3권2호
    • /
    • pp.29-40
    • /
    • 1998
  • Flame structures and NOx formation characteristics in the flame lets of coflow and counterflow diffusion flame are numerically studied. Calculations were carried out twice with the $C_2-Full$ and $C_2-Thermal$ Mechanism for each flame. Mixture fractions and scalar dissipation rates are used as the parameters to compare the flame let structures and NOx formation characteristics quantitatively. It was found that there is a similarity in flame temperature and stable species profiles except radical profiles between two flamelets. And there are some differences in NOx concentration and production rates. These results imply that the flow effects must be considered in calculations for NOx formation of turbulent flames using Laminar Flamelet Model.

  • PDF

$CO_2$ 첨가가 $CH_4$-공기 대향류 확산화염의 구조 및 NOx 생성에 미치는 영향 (Effect of $CO_2$ Addition on Flame Structure and NOx Formation of $CH_4-Air$ Counterflow Diffusion Flames)

  • 이승로;한지웅;이창언
    • 한국연소학회지
    • /
    • 제4권2호
    • /
    • pp.97-108
    • /
    • 1999
  • This numerical study was to investigate the effect of $CO_2$ addition on the structures and NOx formation characteristics in $CH_4$ counterflow diffusion flame. The importance of radiation effect was identified and $CO_2$ addition effect was investigated in terms of thermal and chemical reaction effect. Also the causes of NOx reduction were clarified by separation method of each formation mechanisms. The results were as follows : The radiation effect was intensified by $CO_2$ addition. Thermal effect mainly contributed to the changes in flame structure and the amount of NO formation but the chemical reaction effect also cannot be neglected. The reduction of thermal NO was dominant with respect to reduction rate, but that of prompt NO was dominant with respect to total amount.

  • PDF

메탄 대향류 확산화염내 수소를 첨가한 탄소나노물질 합성에 관한 연구 (Study on synthesis of carbon nanomaterials by hydrogen mixing in counterflow methane diffusion flames)

  • 신우중;최정식;윤석훈;이현식;최재혁
    • 한국마린엔지니어링학회:학술대회논문집
    • /
    • 한국마린엔지니어링학회 2011년도 후기공동학술대회 논문집
    • /
    • pp.88-89
    • /
    • 2011
  • The study on synthesis of carbon nanomaterials by H2 mixing in counterflow methane diffusion flames has been experimentally conducted. We have also investigated on effect of catalyst and temperature in flame. The counterflow flame was formed by many kind of gas (fuel side using $CH_4-H_2-N_2$ and oxidizer side $N_2-O_2$) and nitrogen shields discharge on each other side to cut off oxidizer of the atmosphere. Ferrocene was used as a metal catalyst for CNTs synthesis. substrate was used to deposit carbon nanomaterials and these were analyzed by FE-SEM. We could find that carbon nanotubes and many kind of carbon nano materials were formed in Cu wire substrate, through this experiment.

  • PDF

대향류 확산 화염 중에서 비구형 입자 성장에 관한 해석 (Simulation of the Growth of Non-Spherical Particles in a Counterflow Diffusion Flame)

  • 정재인;황준영;이방원;최만수;정석호
    • 대한기계학회논문집B
    • /
    • 제23권8호
    • /
    • pp.997-1009
    • /
    • 1999
  • Silica particle formation and growth process including chemical reaction, coagulation and sintering was studied in a counterflow diffusion flame burner. The counterflow geometry provides a one dimensional flow field, along the stagnation point streamline, which greatly simplifies interpretation of the particle growth characteristics. $SiCl_4$ has been used as the source of silicon in hydrogen/oxygen/argon flames. The temperature profiles obtained by calculation showed a good agreement with experiment data. Using one and two dimensional sectional method, aerosol dynamics equation in a flame was solved, and these two results were compared. The two dimensional section method can consider sintering effect and growth of primary particle during synthesis, thus it showed evolution of morphology of non-spherical particles (aggregates) using surface fractal dimension. The effects of flame temperature and chemical loading on particle dynamics were studied. Geometric mean diameter based on surface area and total number concentration followed the trend of experiment results, especially, the change of diameters showed the sintering effect in high temperature environment.

대향류 확산화염의 소염특성에 미치는 직류전기장의 영향에 관한 실험적 연구 (Experimental Study on the Effect of DC Electric Field on Extinction Characteristics of Counterflow Diffusion Flame)

  • 박익형;김민국;원상희;차민석;정석호
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
    • /
    • pp.253-259
    • /
    • 2006
  • The effect of DC electric fields on the flame extinction was investigated experimentally in counterflow configurations for the methane/oxygen/nitrogen diffusion flame. The electric fields was applied by connecting the high voltage and ground terminals to the upper and lower burners, respectively. In case of having electric fields, several modes of flame extinction was observed according to the electric field intensity and strain rate defined by the exit velocity. To visualize and characterize the flame structure and intensity, planar LIF technique was adopted for OH radicals. Consequently, several length scales, including the flame width, thickness, and height from the burner tip, were introduced to explain the various flame behaviors and to characterize the flame extinctions. It was found that the variation of flame width and the chemical reaction are strongly related to a critical electric field intensity, thus the various modes of diffusion flame extinction could be observed due to the electric fields.

  • PDF