TY - JOUR
T1 - A Numerical Study of Lean Propane-Air Flame Acceleration at the Early Stages of Burning in Cold and Hot Isothermal Walled Small-Size Tubes
AU - Baigmohammadi, Mohammadreza
AU - Roussel, Olivier
AU - Dion, Claude M.
N1 - Funding Information:
Open access funding provided by Umea University. The present work was supported financially by the Swedish Research Council (VR), the Kempe Foundation and the Faculty of Natural Sciences, Umeå University. The computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at HPC2N, Umeå University. Acknowledgements
PY - 2020/1/1
Y1 - 2020/1/1
N2 - In this study, the problem of lean propane-air premixed flame acceleration from closed to open end during the early stages of burning in small-size tubes with isothermal walls was considered. In particular, the effects of tube radius, slip/non-slip wall conditions, and the wall temperature on the flame propagation and shape were investigated numerically. Five stages of flame propagation are identified: 1) spherical expansion of the flame front; 2) finger shape expansion of the flame front before touching the wall; 3) flame propagation in the tube subjected to flame-wall interactions; 4) transformation of the flame shape into tulip form; 5) conversion of the tulip shape flame to finger. Our results show that the tube radius, wall condition and its temperature significantly affect flame propagation regimes even in the first instance of the flame propagation in the tubes. We find that increasing tube radius has, overall, the effect of increasing the flame propagation speed in isothermal tubes. Also, depending on tube radius and wall condition, the wall temperature can increase or decrease the flame propagation speed in the isothermal tubes. Furthermore, the results demonstrate that imposing either slip or non-slip condition on the tube’s walls impressively affects flame acceleration and its configuration in the early stages. We observe that, unlike flame propagation forms in the tubes with slip walls, the early exponential flame propagation phase in the tubes was generally followed by a linear flame propagation phase in the tubes with a non-slip wall condition. We obtain that flame propagation in tubes with slip wall conditions are more sensitive to variations in tube radius and wall temperature compared to non-slip conditions. We also see that, contrary to the exponential flame propagation phase, increasing the non-slip wall temperature reduces the flame propagation speed in the linear part of the flame propagation, while such an increase in temperature leads to oscillations in the flame propagation speed in the tubes with slip walls.
AB - In this study, the problem of lean propane-air premixed flame acceleration from closed to open end during the early stages of burning in small-size tubes with isothermal walls was considered. In particular, the effects of tube radius, slip/non-slip wall conditions, and the wall temperature on the flame propagation and shape were investigated numerically. Five stages of flame propagation are identified: 1) spherical expansion of the flame front; 2) finger shape expansion of the flame front before touching the wall; 3) flame propagation in the tube subjected to flame-wall interactions; 4) transformation of the flame shape into tulip form; 5) conversion of the tulip shape flame to finger. Our results show that the tube radius, wall condition and its temperature significantly affect flame propagation regimes even in the first instance of the flame propagation in the tubes. We find that increasing tube radius has, overall, the effect of increasing the flame propagation speed in isothermal tubes. Also, depending on tube radius and wall condition, the wall temperature can increase or decrease the flame propagation speed in the isothermal tubes. Furthermore, the results demonstrate that imposing either slip or non-slip condition on the tube’s walls impressively affects flame acceleration and its configuration in the early stages. We observe that, unlike flame propagation forms in the tubes with slip walls, the early exponential flame propagation phase in the tubes was generally followed by a linear flame propagation phase in the tubes with a non-slip wall condition. We obtain that flame propagation in tubes with slip wall conditions are more sensitive to variations in tube radius and wall temperature compared to non-slip conditions. We also see that, contrary to the exponential flame propagation phase, increasing the non-slip wall temperature reduces the flame propagation speed in the linear part of the flame propagation, while such an increase in temperature leads to oscillations in the flame propagation speed in the tubes with slip walls.
KW - Cold walls
KW - Flame acceleration
KW - Hot walls
KW - Isothermal walls
KW - Narrow tubes
KW - Propane-air
UR - http://www.scopus.com/inward/record.url?scp=85072181158&partnerID=8YFLogxK
U2 - 10.1007/s10494-019-00057-5
DO - 10.1007/s10494-019-00057-5
M3 - Article
AN - SCOPUS:85072181158
SN - 1386-6184
VL - 104
SP - 179
EP - 207
JO - Flow, Turbulence and Combustion
JF - Flow, Turbulence and Combustion
IS - 1
ER -