TY - JOUR
T1 - Microgravity burner-generated spherical diffusion flames
T2 - Experiment and computation
AU - Tse, Stephen D.
AU - Zhu, Delin
AU - Sung, Chih Jen
AU - Ju, Yiguang
AU - Law, Chung K.
N1 - Funding Information:
This work was supported by the NASA Microgravity Combustion Program. It is a pleasure to acknowledge useful technical discussions with and suggestions from Dr. K. Sacksteder of NASA-Glenn, Dr. L. He of Princeton University, and Prof. H. Wang of the University of Delaware.
PY - 2001
Y1 - 2001
N2 - Microgravity experiments were conducted in the 2.2-s drop-tower facility at the NASA Glenn Research Center to study the transient response of the burner-generated spherical diffusion flame caused by its initial displacement from the steady-state position. The experiment involved issuing H2/CH4/inert mixtures of constant fuel mass flow rates from a bronze, porous, 1.27-cm-diameter, spherical burner into atmospheric air. The experimental results on the flame trajectory were found to agree well with those obtained through fully transient computational simulation with detailed chemistry and transport, and appropriate initial conditions. Furthermore, although steady-state behavior should exist for such flames, the experimental and computational results indicated that it cannot be reached within the 2.2-s microgravity duration for the fuels and mass-flow rates tested.To assess the role of radiation on the flame dynamics and extinction, computations were performed without radiation, with radiation employing the optically thin approximation, and with radiation utilizing a detailed emission/absorption statistical narrow band (SNB) model. The computation showed that while the influence of radiative heat loss on the position of the flame is small, proper consideration of radiative effects is crucial in assessing the state of flame extinction. Specifically, while all simulations of the experimental cases studied incorporating radiative heat loss revealed that the flame extinguishes well before the attainment of steady state, simulations accounting for gaseous reabsorption of radiative emissions were required to adequately represent the experiments in terms of extinction time, with the optically thin simulations predicting premature extinction during the flame expansion process. Effects of heat loss to the porous burner were also examined, and the lack of correspondence between the visible flame luminosity and flame strength, as related to flame temperature and heat release rate, was noted.
AB - Microgravity experiments were conducted in the 2.2-s drop-tower facility at the NASA Glenn Research Center to study the transient response of the burner-generated spherical diffusion flame caused by its initial displacement from the steady-state position. The experiment involved issuing H2/CH4/inert mixtures of constant fuel mass flow rates from a bronze, porous, 1.27-cm-diameter, spherical burner into atmospheric air. The experimental results on the flame trajectory were found to agree well with those obtained through fully transient computational simulation with detailed chemistry and transport, and appropriate initial conditions. Furthermore, although steady-state behavior should exist for such flames, the experimental and computational results indicated that it cannot be reached within the 2.2-s microgravity duration for the fuels and mass-flow rates tested.To assess the role of radiation on the flame dynamics and extinction, computations were performed without radiation, with radiation employing the optically thin approximation, and with radiation utilizing a detailed emission/absorption statistical narrow band (SNB) model. The computation showed that while the influence of radiative heat loss on the position of the flame is small, proper consideration of radiative effects is crucial in assessing the state of flame extinction. Specifically, while all simulations of the experimental cases studied incorporating radiative heat loss revealed that the flame extinguishes well before the attainment of steady state, simulations accounting for gaseous reabsorption of radiative emissions were required to adequately represent the experiments in terms of extinction time, with the optically thin simulations predicting premature extinction during the flame expansion process. Effects of heat loss to the porous burner were also examined, and the lack of correspondence between the visible flame luminosity and flame strength, as related to flame temperature and heat release rate, was noted.
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U2 - 10.1016/S0010-2180(01)00247-4
DO - 10.1016/S0010-2180(01)00247-4
M3 - Article
AN - SCOPUS:0035359035
SN - 0010-2180
VL - 125
SP - 1265
EP - 1278
JO - Combustion and Flame
JF - Combustion and Flame
IS - 4
ER -