TY - JOUR
T1 - Transition from opposed flame spread to fuel regression and blow off
T2 - Effect of flow, atmosphere, and microgravity
AU - Huang, Xinyan
AU - Link, Shmuel
AU - Rodriguez, Andy
AU - Thomsen, Maria
AU - Olson, Sandra
AU - Ferkul, Paul
AU - Fernandez-Pello, Carlos
N1 - Publisher Copyright:
© 2018 The Combustion Institute.
PY - 2019
Y1 - 2019
N2 - The spread of flames over the surface of solid combustible material in an opposed flow is different from the mass burning (or fuel regression) in a pool fire. However, the progress of a flame front over a solid fuel includes both flame spread and fuel regression, but the difference between these two processes has not been well clarified. In this work, experiments using cylindrical PMMA samples were conducted in normal gravity and in microgravity. We aim to identify the transition from opposed flame spread to fuel regression under varying conditions, including sample size, opposed flow velocity, pressure, oxygen concentration, external radiation, and gravity level. For a thick rod in normal gravity, as the opposed flow increases to 50-100 cm/s, the flame can no longer spread over the fuel surface but stay in the recirculation zone downstream of the cylinder end surface, like a pool fire flame. The flame spread first transitions to fuel regression at a critical leading-edge regression angle of α 45°, and then, flame blow-off occurs. Under large opposed flow velocity, a stable flat blue flame is formed floating above the rod end surface, because of vortex shedding. In microgravity at a low opposed flow (<10 cm/s), pure fuel regression was not observed. This work aims to clarify the differences between the flame spread and fuel regression in the progress of a flame and provide a better understanding of the blow-off phenomenon on solid fuels.
AB - The spread of flames over the surface of solid combustible material in an opposed flow is different from the mass burning (or fuel regression) in a pool fire. However, the progress of a flame front over a solid fuel includes both flame spread and fuel regression, but the difference between these two processes has not been well clarified. In this work, experiments using cylindrical PMMA samples were conducted in normal gravity and in microgravity. We aim to identify the transition from opposed flame spread to fuel regression under varying conditions, including sample size, opposed flow velocity, pressure, oxygen concentration, external radiation, and gravity level. For a thick rod in normal gravity, as the opposed flow increases to 50-100 cm/s, the flame can no longer spread over the fuel surface but stay in the recirculation zone downstream of the cylinder end surface, like a pool fire flame. The flame spread first transitions to fuel regression at a critical leading-edge regression angle of α 45°, and then, flame blow-off occurs. Under large opposed flow velocity, a stable flat blue flame is formed floating above the rod end surface, because of vortex shedding. In microgravity at a low opposed flow (<10 cm/s), pure fuel regression was not observed. This work aims to clarify the differences between the flame spread and fuel regression in the progress of a flame and provide a better understanding of the blow-off phenomenon on solid fuels.
KW - Blue flame sheet
KW - Burning
KW - PMMA rod
KW - Reduced pressure
KW - Regression angle
UR - http://www.scopus.com/inward/record.url?scp=85049186856&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2018.06.022
DO - 10.1016/j.proci.2018.06.022
M3 - Article
AN - SCOPUS:85049186856
SN - 1540-7489
VL - 37
SP - 4117
EP - 4126
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 3
ER -