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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.
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.
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.
난류 제트 확산화염에서 PIV/OH-PLIF 동시측정을 이용한 날림 한계 근처에서의 변형률 및 OH 구조에 관한 연구
황정재(Jeongjae Hwang),김태성(Taesung Kim),윤지수(Jisu Yoon),윤영빈(Youngbin Yoon) 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12
Simultaneous measurements of planar laser-induced fluorescence (PLIF) of OH radicals and particle image velocimetry (PIV) were used to investigate the effect of strain rates and OH thicknesses on the detachment of turbulent syngas non-premixed jet flames. Mean values of the extensive principal strain rate on the OH layer decrease with the axial distance, and the maximum value appears near the nozzle. Flames with various fuel jet Re near detachment have almost identical minimum OH thicknesses.
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.