H2/CO 합성가스 비예혼합 난류 제트화염에서 부착화염의 화염안정화
Stability of Attached Flame in H2/CO Syngas Non-premixed Turbulent Jet Flame
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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* chemiluminescence 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.
Abstract
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* chemiluminescence 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.
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