TY - GEN

T1 - Similarity solutions and applications to turbulent upward flame spread on non-charring materials

AU - Delichatsios, Michael A.

AU - Delichatsios, Mary

AU - Chen, Y.

AU - Hasemi, Y.

PY - 1992/12/1

Y1 - 1992/12/1

N2 - Turbulent upward flame spread on non-charring materials (for pyrolysis lengths less than 1.8 m) is shown to be directly predicted by using measurable flammability parameters. The controlling parameters are: a combustion related length scale which is proportional to (dq″net ΔHc/ΔHv)2, a pyrolysis or ignition time τp, and a transient pyrolysis parameter: λ = L/c ΔTp = ratio of the latent heat to the sensible heat of the pyrolysis temperature of the material. In the length scale parameter, dq″net is the total net heat flux from the flames to the wall (i.e. total heat flux minus reradiation losses), ΔHc is the heat of combustion and ΔHv is an effective heat of gasification for the material. The pyrolysis or ignition time depends (for thermally thick conditions) on the material thermal inertia, the pyrolysis temperature and the total heat flux from the flames to the wall, dq″fw. The controlling parameters were developed by using a numerical simulation, developed earlier, and new exact similarity solutions which complement existing similarity solutions. The predictions of the analysis are validated by comparison with upward flame spread experiments on PMMA. The present results are directly applicable for pyrolysis lengths less than 1.8 m over which experiments in practical materials show that the total (radiative and convective) heat flux to the wall from the flames is constant and nearly uniform over the flame length. As the pyrolysis length increases (>approx. 1.8 m), radiation dominates and a different total wall heat flux distribution applies.

AB - Turbulent upward flame spread on non-charring materials (for pyrolysis lengths less than 1.8 m) is shown to be directly predicted by using measurable flammability parameters. The controlling parameters are: a combustion related length scale which is proportional to (dq″net ΔHc/ΔHv)2, a pyrolysis or ignition time τp, and a transient pyrolysis parameter: λ = L/c ΔTp = ratio of the latent heat to the sensible heat of the pyrolysis temperature of the material. In the length scale parameter, dq″net is the total net heat flux from the flames to the wall (i.e. total heat flux minus reradiation losses), ΔHc is the heat of combustion and ΔHv is an effective heat of gasification for the material. The pyrolysis or ignition time depends (for thermally thick conditions) on the material thermal inertia, the pyrolysis temperature and the total heat flux from the flames to the wall, dq″fw. The controlling parameters were developed by using a numerical simulation, developed earlier, and new exact similarity solutions which complement existing similarity solutions. The predictions of the analysis are validated by comparison with upward flame spread experiments on PMMA. The present results are directly applicable for pyrolysis lengths less than 1.8 m over which experiments in practical materials show that the total (radiative and convective) heat flux to the wall from the flames is constant and nearly uniform over the flame length. As the pyrolysis length increases (>approx. 1.8 m), radiation dominates and a different total wall heat flux distribution applies.

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M3 - Conference contribution

AN - SCOPUS:0026995306

SN - 0791810682

T3 - American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD

SP - 21

EP - 28

BT - Heat and Mass Transfer in Fire and Combustion Systems - 1992

PB - Publ by ASME

T2 - Winter Annual Meeting of the American Society of Mechanical Engineers

Y2 - 8 November 1992 through 13 November 1992

ER -