Effects of low air pressure on radiation-controlled rectangular ethanol and n-heptane pool fires

Abstract Experiments on rectangular ethanol and n -heptane pool fires were conducted at different altitudes in Hefei (99.8 kPa) and Lhasa (66.5 kPa). The burners tested had the same fuel area of 900 cm 2 , but with aspect ratio of long side to short side ( n  =  l / w ) varied from 1 and 8. The individual and combined influences of low pressure and aspect ratio on burning rate, temperature, puffing frequency, flame height and radiation for the two fuels were interpreted and formulated. First, burning rate was found to be proportional to ambient air pressure under radiation control, the main reason is that radiative heat flux decreased with pressure due to the pressure affecting the soot absorption coefficient. Flame temperature slightly increased, leading to higher flame puffing frequency at low pressure. Flame height was almost insensitive to pressure as H ∝ p 0 . Second, for aspect ratio n , flame temperature was constant and independent of fuel type and burner shape. With increasing n , burner wall temperature increased at the long side, and decreased drastically at the short side, especially n  = 8. This was attributed to the change of flame tilt and heating of the burner side, caused by variation of entrainment motion. Flame puffing frequency was found to increase with n as a function of f ∼ ( Δ T / T ∞ ) ( n + 1 ) / 2 n . The flame was observed to split into small clusters by enhanced asymmetric entrainment, and H decreased with increasing n as H ∼ ( 1 / n ) 2 / 5 Q ˙ 4 / 15 . Considering fuel differences, with increasing n , the burning rate of the ethanol pool fire decreased, and n -heptane showed the opposite trend.

[1]  D. Drysdale.  An Introduction to Fire Dynamics , 2011 .

[2]  S. Koda,et al.  An Experimental Study of Radiative Properties of Pool Fires Of an Intermediate Scale , 1985 .

[3]  Baki M. Cetegen,et al.  Experiments on the periodic instability of buoyant plumes and pool fires , 1993 .

[4]  H. W. Emmons,et al.  A study of natural convection above a line fire , 1961, Journal of Fluid Mechanics.

[5]  G. Heskestad,et al.  Radiation fire modeling , 2000 .

[6]  I. Glassman.  Sooting laminar diffusion flames: Effect of dilution, additives, pressure, and microgravity , 1998 .

[7]  Y. Hasemi,et al.  Fuel Shape Effect On The Deterministic Properites Of Turbulent Diffusion Flames , 1989 .

[8]  Takashi Kashiwagi,et al.  Estimate of flame radiance via a single location measurement in liquid pool fires , 1991 .

[9]  Ran Tu,et al.  Influence of low air pressure on combustion characteristics and flame pulsation frequency of pool fires , 2011 .

[10]  G. Cox,et al.  An experimental study of some line fires , 1996 .

[11]  T. Kubota,et al.  Visible structure of buoyant diffusion flames , 1985 .

[12]  Andrew G. Glen,et al.  APPL , 2001 .

[13]  Yaping He,et al.  Combustion characteristics of n-heptane and wood crib fires at different altitudes , 2009 .

[14]  V. Blinov,et al.  DIFFUSION BURNING OF LIQUIDS , 1961 .

[15]  B. Cetegen,et al.  Experiments on stability and oscillatory behavior of planar buoyant plumes , 1998 .

[16]  Fang Jun,et al.  The influence of low atmospheric pressure on carbon monoxide of n-heptane pool fires. , 2008, Journal of hazardous materials.

[17]  Jie Chen,et al.  INFLUENCE OF GRAVITY AND PRESSURE ON POOL FIRE-TYPE DIFFUSION FLAMES , 1996 .

[18]  Gary F. Bennett,et al.  The SFPE handbook of fire protection engineering : By P.J. DiNenno, C.L. Beyler, R.L.P. Custer, W.D. Walton and J.M. Watts, Jr., National Fire Protection Association, Quincy, MA and Society of Fire Prot , 1990 .

[19]  L. Trefethen,et al.  Some Unanswered Questions in Fluid Mechanics , 1990 .

[20]  E. Villermaux,et al.  The Effect of Buoyancy on Flickering in Diffusion Flames , 1997 .

[21]  Longhua Hu,et al.  A wind tunnel experimental study on burning rate enhancement behavior of gasoline pool fires by cross air flow , 2011 .

[22]  M. C. Yuen,et al.  Pressure modeling of fires , 1973 .

[23]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[24]  D. Wieser,et al.  The influence of high altitude on fire detector test fires , 1997 .

[25]  Jian Wang,et al.  Combustion characteristics of n-heptane at high altitudes , 2011 .