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H₂/CO 합성가스의 난류 제트 확산화염에서 EINOx Scaling
황정재(Jeongjae Hwang),손기태(Kitae Sohn),김태성(Taesung Kim),윤영빈(Youngbin Yoon) 한국연소학회 2012 KOSCOSYMPOSIUM논문집 Vol.- No.45
EINOx scaling for H₂/CO non-premixed turbulent jet flame was conducted. NOx concentration and flame length were measured simultaneously with varying flow conditions. Flame length increases with Reynolds number which means the flames in buoyancy-momentum transition region. We assessed the previous Chen & Driscoll"s scaling with present results. However, the scaling cannot satisfy the present results. We proposed new scaling which is addressed the simplified flame residence time. The new scaling satisfies the results of H₂/CO syngas flame as well as pure hydrogen flames.
동축공기 유동장에서 수소 난류확산 부상화염의 안정화 연구
황정재(Jeongjae Hwang),오정석(Jeongseog Oh),백경엽(Kyong-Yup Paik),윤영빈(Youngbin Yoon) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40
To understand hydrogen jet liftoff height, the stabilization mechanism of turbulent lifted jet flames under non-premixed conditions was studied. The objectives were to determine flame stability mechanisms, to analyze flame structure, and to characterize the lifted jetat the flame stabilization point. Hydrogen flow velocity varied from 100 to 300 ㎧. Coaxial air velocity was regulated from 12 to 20 ㎧. Simultaneous velocity field and reaction zone measurements used, PIV/OH PLIF techniques with Nd:YAG lasers and CCD/ICCD cameras. Liftoff height decreased with increased fuel velocity. The flame stabilized in a lower velocity region next to the faster fuel jet due to the mixing effects of the coaxial air flow. Lifted flame stabilization was related to local principal strain rate and turbulent intensity, assuming that combustion occurs where local flow velocity and turbulent flame propagation velocity are balanced.
동축공기가 있는 H₂/CO 비예혼합 난류 제트화염의 화염 안정성에 대한 실험적 연구
황정재(Jeongjae Hwang),Nicolas Bouvet,손기태(Kitae Sohn),윤영빈(Youngbin Yoon) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
The research on the stability characteristics of the H₂/CO syngas jet flame in the turbulent region was conducted. Syngas fuel composition fraction, nozzle diameter, fuel velocity and coaxial air velocity were varied to investigate the effects of those on the characteristics of stability and mechanism of blowoff/liftoff. For higher CO content fuel, blowoff/liftoff is occurred at relatively low fuel velocity. But for all case of composition of fuel and all case of nozzle geometry, they have similar trend of blowoff/liftoff limit which is like a C-curve in fuel-air velocity diagram. The coaxial air diameter does not effect on the blowoff/liftoff coaxial air velocity in case of same fuel nozzle geometry.
동축공기 조건에서 H₂/CO 난류 제트 확산화염의 화염길이
황정재(Jeongjae Hwang),Nicolas Bouvet,손기태(Kitae Sohn),윤영빈(Youngbin Yoon) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
The effect of fuel composition and coaxial air on the flame length was studied in a non-premixed turbulent jet flame. Three cases(100% H₂, 75% H2 / 25% CO, and 50% H₂ / 50% CO) were determined to investigate effects of the fuel composition and fuel velocity and coaxial velocity were varied Uf = 40-140 m/s and Ua = 1.7-11.2 m/s each other to investigate effects of the coaxial velocity. And for excluding the partial premixing effect of the lifted flame, experiments on flame length were conducted in the attached flame region. The flame length is decreased with coaxial air increasing since the air entrainment for reacting is supplied with coaxial air instead of ambient air. In this study, we confirmed that the scaling correlation for predicting the flame length in a jet flame with coaxial air has good agrees with far field concept for relatively low Ua/Uf and near field concept for relatively high Ua/Uf.
H₂/CO 합성가스의 비예혼합 난류 제트화염에서 화염 길이와 EINOx 스케일링
황정재(Jeongjae Hwang),손기태(Kitae Sohn),Nicolas Bouvet,윤영빈(Youngbin Yoo) 한국연소학회 2012 한국연소학회지 Vol.17 No.4
The flame lengths and NOx emission characteristics of syngas H₂/CO turbulent non-premixed jet flames were investigated. The flame length which is the main parameter governs NOx emission was studied for various syngas compositions. The flame length was compared with previous correlation between Froude number and flame height and it shows that they have good agreements. It was confirmed that the turbulent jet flames herein investigated are in the region of buoyancy-momentum transition. NOx emission was reduced with increased Reynolds number and CO contents in syngas fuel and with decreased fuel nozzle diameter which is attributed by decreased flame residence time. Previous EINOx scaling based on flame residence time of Lf³/(df²Uf) satisfies only the jet flame in momentum-dominated region, not buoyancy-momentum transition region. The simplified flame residence time (Lf/Uf) was adopted in modified EINOx scaling. The modified scaling satisfies the jet flames not only in momentum-dominated region but in buoyancy-momentum transition region. The scaling is also satisfied with H₂/CO syngas jet flames.
V-gutter 보염기가 있는 모델 램제트 연소기에서의 연소불안정의 실험적 연구
황정재(Jeongjae Hwang),송진관(Jinkwan Song),송재천(JaeCheon Song),윤영빈(Youngbin Yoon) 한국연소학회 2008 KOSCOSYMPOSIUM논문집 Vol.- No.-
Characteristics and mechanisms of combustion instability in model ramjet combustor with V-gutter flameholder are experimentally investigated at airflow speed of 27.5m/s and 36.7m/s, especially 27.5m/s. For acquiring instability frequency and rms value, dynamic pressure sensor was used at combustor. With an aid of the high-speed photography, the phenomena of flame dynamics is well illustrated. Schlieren photography in cold flow shows relations between vortex or temporal characteristic of recirculation zone and combustion instability. Results shows that instability occurs strongly in lean condition, Φ = 0.65 - 0.75, and the frequency is near 30㎐. A flame in recirculation zone appears periodically and the period is well matched with instability frequency. Combustion instability is highly relative with the temporal characteristics of recirculation zone rather than vortex shedding frequency behind the flameholder.
H<SUB>2</SUB>/CO 합성가스 비예혼합 난류 제트화염에서 부착화염의 화염안정화
황정재(Jeongjae Hwang),Nicolas Bouvet,손기태(Kitae Sohn),윤영빈(Youngbin Yoon) 한국연소학회 2012 한국연소학회지 Vol.17 No.1
The detachment stability characteristics of syngas H2/CO jet attached flames were studied. The flame stability was observed while varying the syngas fuel composition, coaxial nozzle diameter and fuel nozzle rim thickness. The detachment stability limit of the syngas single jet flame was found to decrease with increasing mole fraction of carbon monoxide in the fuel. In hydrogen jet flames with coaxial air, the flame detachment stability was found to be independent of the coaxial nozzle diameter. However, velocities of appearance of liftoff and blowout velocities of lifted flames have dependence. At lower fuel velocity range, the critical coaxial air velocity leading to flame detachment increases with increasing fuel jet velocity, whereas at higher fuel velocity range, it decreases. This increasing-decreasing non-monotonic trend appears for all H2/CO syngas compositions (50/50~100/0% H2/CO). To qualitatively understand the flame behavior near the nozzle rim, OH<SUP>*</SUP> chemilumi-nescence imaging was performed near the detachment limit conditions. For all fuel compositions, local extinction on the rim is observed at lower fuel velocities(increasing stability region), while local flame extinction downstream of the rim is observed at higher fuel velocities(decreasing stability region). Maximum values of the non-monotonic trends appear to be identical when the fuel jet velocity is normalized by the critical fuel velocity obtained in the single jet cases.