Advertisement

Soot Production and Radiative Heat Transfer in Opposed Flame Spread over a Polyethylene Insulated Wire in Microgravity

  • 144 Accesses

  • 2 Citations

Abstract

Flame spread over an insulated electrical wire is identified as a fire scenario in space vehicles. In such microgravity configurations, the contribution of thermal radiation from gaseous participating species and soot to the wire burning rate and flame spread is not fully understood and the present paper addresses this question both experimentally and numerically. A non-buoyant opposed-flow flame spread configuration over a nickel–chrome wire coated by Low Density PolyEthylene (LDPE) is considered with an O2/N2 oxidizer composed of 19% of oxygen in volume and a flow velocity of 200 mm/s. Flame spread rate, pyrolysis rate, stand-off distance, soot volume fraction, and soot temperature are experimentally determined based on optical diagnostics that capture the flame spread in parabolic flights. The numerical model uses the measured spread and pyrolysis rates as input data and solves transport equations for mass, momentum, species, energy, and soot number density and mass fraction in an axisymmetric flame-fixed coordinate system in conjunction with a simple degradation model for the LDPE and a state-of-the-art radiation model. The model considers two assumptions. First, pure ethylene results from the decomposition of LDPE and, second, an acetylene/benzene based-soot model, initially validated for C1–C3 hydrocarbons, can be extended with minor modifications to model soot production of LDPE. Comparisons between model predictions and experimental data in terms of flame structure and soot volume fraction support these assumptions. The major finding of this study is that radiation contributes negatively to the surface heat balance along the LDPE molten surface and the coating ahead of the molten front. This shows that the convective heat transfer from the flame is the main contribution to sustain the pyrolysis process and the flame spread is mainly ensured owing to the combined contribution of convection from flame and conduction inside the condensed phase. The maximum incident radiative flux along the molten ball is 17.5 kW/m2 and is reached at the molten ball trailing edge whereas the radiant fraction is about 0.25. Neglecting flame self-absorption affects these values by less than 5%, showing that the optically-thin approximation is valid for this flame. In addition, soot radiation dominates the radiative heat transfer in this flame, contributing for about two-third of the total radiation. Finally, model results show that the usually-used thermally-thin assumption throughout the LDPE coating is not strictly valid.

This is a preview of subscription content, log in to check access.

We’re sorry, something doesn't seem to be working properly.

Please try refreshing the page. If that doesn't work, please contact support so we can address the problem.

Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12

Abbreviations

a :

Stretch function (–)

A S :

Soot surface area (m−1)

C a :

Agglomeration rate constant (–)

c :

Heat capacity (J kg−1 K−1)

f :

k-distribution function (m−1)

f S :

Soot volume fraction (–)

g :

Cumulative k-distribution function (–)

\({I}_{{g}} ,{I}\) :

Radiative intensity (W m−2 sr−1)

I b :

Blackbody intensity (Planck function) (W m−2 sr−1)

k :

Absorption coefficient variable (m−1)

k B :

Boltzmann constant (J kg−1)

L :

Heat of reaction (J kg−1)

\(\dot{m}_{pyr}\) :

Pyrolysis mass flow rate (kg s−1)

\(\dot{m}_{pyr}^{{{\prime \prime }}}\) :

Pyrolysis mass flow rate per unit area (kg m−2 s−1)

N A :

Avogadro number (part mol−1)

NC min :

Number of carbon atoms in the incipient soot particle (–)

N S :

Soot number density per unit mass of mixture (part kg−1)

\(\varvec{n}_{\varvec{q}}\) :

Unit surface normal (pointing away from surface into the medium)

\(\dot{q}_{net}^{{{\prime \prime }}}\) :

Net heat flux (W m−2)

\(\dot{q}_{R}^{{{\prime \prime }}}\) :

Radiative flux (W m−2)

\(\dot{q}_{R,inc}^{''}\) :

Incident radiative flux (W m−2)

\(\dot{q}_{R,net}^{{{\prime \prime }}}\) :

Net radiative flux (W m−2)

\(\dot{q}_{R,R}^{{{\prime \prime }}}\) :

Surface re-radiation (W m−2)

r :

Radial coordinate or radius (m)

\(\varvec{r}\) :

Position vector (m)

\(\hat{\varvec{s}}\) :

Unit vector into a given direction (–)

T :

Temperature (K)

u :

Velocity (m s−1)

\(u_{p}\) :

Spread rate (m s−1)

W i :

Molecular weight of the ith species (kg mol−1)

Y i :

Mass fraction of the ith species (–)

z :

Axial coordinate (m)

δ :

Stand-off distance (m)

\(\Delta \eta_{j}\) :

Narrow band spectral resolution (cm−1)

η :

Wavenumber (cm−1)

κ :

Absorption coefficient (m−1)

\(\lambda\) :

Thermal conductivity (W m−1 K−1)

ρ :

Density (kg m−3)

\(\dot{\omega }_{n}\) :

Reaction rate for soot nucleation (mol m−3 s−1)

\(\dot{\omega }_{sg}\) :

Reaction rate for soot surface growth (mol m−3 s−1)

\(\dot{\omega }_{{N_{S} }}\) :

Reaction rate for soot number density (part m−3 s−1)

\(\dot{\omega }_{{O_{2} }}\) :

Reaction rate for soot oxidation by O2 (kg m−3 s−1)

\(\dot{\omega }_{OH}\) :

Reaction rate for soot oxidation by OH (kg m−3 s−1)

\(\dot{\omega }_{{Y_{S} }}\) :

Source term for soot mass fraction (kg m−3 s−1)

\(\varOmega_{i}\) :

Solid angle around the direction \(s_{i}\)

b :

Molten ball

core:

Metallic core

f :

Flame

F :

Fuel

g :

Gas

inc :

Incident

m :

Molten phase

melt :

Melting

mix:

Mixing

pyr :

Pyrolysis

PE :

Polyethylene

R :

Radiation or radiative

r:

r-direction

ref :

Reference state

S :

Soot

wire:

Coated wire

z:

z-direction

η :

At a given wavenumber or per unit wavenumber

∞:

Ambient

FS:

Full spectrum

NB:

Narrow band

g :

Gas

g-s :

Gas-soot

References

  1. 1.

    Greenberg PS, Sacksteder KR, Kashiwagi T (1994) The USML-1 wire insulation flammability glovebox experiment. In: Third international microgravity combustion workshop 2, NASA Lewis Research Center, Cleveland, Ohio, pp 25–30

  2. 2.

    Kikuchi M, Fujita O, Ito K, Sato A, Sakuraya T (1998) Experimental study on flame spread over wire insulation in microgravity. Proc Combust Inst 27:2507–2514. https://doi.org/10.1016/S0082-0784(98)80102-1

  3. 3.

    Fujita O, Nishizawa K, Ito K (2002) Effect of low external flow on flame spread over polyethylene-insulated wire in microgravity. Proc Combust Inst 29:2545–2552. https://doi.org/10.1016/S1540-7489(02)80310-8

  4. 4.

    Citerne JM, Dutilleul H, Kizawa K, Nagachi M, Fujita O, Kikuchi M, Jomaas G, Rouvreau S, Torero JL, Legros G (2016) Fire safety in space—investigating flame spread interaction over wires. Acta Astronaut 126:500–509. https://doi.org/10.1016/j.actaastro.2015.12.021

  5. 5.

    Osorio AF, Mizutani K, Fernandez-Pello C, Fujita O (2015) Microgravity flammability limits of ETFE insulated wires exposed to external radiation. Proc Combust Inst 35:2683–2689. https://doi.org/10.1016/j.proci.2014.09.003

  6. 6.

    Longhua H, Yong L, Yoshioka K, Yangshu Z, Fernandez-Pello C, Ho CS, Fujita O (2017) Limiting oxygen concentration for extinction of upward spreading flames over inclined thin polyethylene-insulated NiCr electrical wires with opposed-flow under normal- and micro-gravity. Proc Combust Inst 36:3045–3053. https://doi.org/10.1016/j.proci.2016.09.021

  7. 7.

    Kong W, Liu F (2009) Numerical study of the effects of gravity on soot formation in laminar coflow methane/air diffusion flames under different air stream velocities. Combust Theory Model 13:993–1023. https://doi.org/10.1080/13647830903342527

  8. 8.

    Contreras J, Consalvi JL, Fuentes A (2018) Numerical simulations of microgravity ethylene/air laminar boundary layer diffusion flames. Combust Flame 191:99–108. https://doi.org/10.1016/j.combustflame.2017.12.013

  9. 9.

    Takahashi S, Kondou M, Wakai K, Bhattacharjee S (2002) Effect of radiation loss on flame spread over a thin PMMA sheet in microgravity. Proc Combust Inst 29:2579–2586. https://doi.org/10.1016/S1540-7489(02)80314-5

  10. 10.

    Legros G, Joulain P, Vantelon JP, Fuentes A, Bertheau D, Torero JL (2006) Soot volume fraction measurements in a three-dimensional laminar diffusion flame established in microgravity. Combust Sci Technol 178:813–835 https://doi.org/10.1080/00102200500271344

  11. 11.

    Fuentes A, Rouvreau S, Joulain P, Vantelon JP, Legros G, Torero JL, Fernandez-Pello C (2007) Sooting behavior dynamics of a non-buoyant laminar diffusion flame. Combust Sci Technol 179:3–19. https://doi.org/10.1080/00102200600805850

  12. 12.

    Fuentes A, Legros G, Claverie A, Joulain P, Vantelon JP, Torero JL (2007) Interactions between soot and CH radicals in a laminar boundary layer type diffusion flame in microgravity, Proc Combust Inst 31:2685–2692. https://doi.org/10.1016/j.proci.2006.08.031

  13. 13.

    Legros G, Fuentes A, Rouvreau S, Joulain P, Porterie B, Torero (2009) Transport mechanisms controlling soot production inside a non-buoyant laminar diffusion flame. Proc Combust Inst 32:2461–2470. https://doi.org/10.1016/j.proci.2008.06.179

  14. 14.

    Legros G, Torero JL (2015) Phenomenological model of soot production inside a non-buoyant laminar diffusion flame. Proc Combust Inst 35:2545–2553. https://doi.org/10.1016/j.proci.2014.05.038

  15. 15.

    Contreras J, Consalvi JL, Fuentes A (2017) Oxygen index effect on the structure of a laminar boundary layer diffusion flame in a reduced gravity environment. Proc Combust Inst 36:3237–3245. https://doi.org/10.1016/j.proci.2016.06.065

  16. 16.

    Takahashi S, Takeuchi H, Ito H, Nakamura Y, Fujita O (2013) Study on unsteady molten insulation volume change during flame spreading over wire insulation in microgravity. Proc Combust Inst 34:2657–2664. https://doi.org/10.1016/j.proci.2012.06.158

  17. 17.

    Guibaud A, Citerne JM, Orlac’h JM, Fujita O, Consalvi JL, Torero JL, Legros G (2018) Broadband modulated absorption/emission technique to probe sooting flames: implementation, validation, and limitations. Proc Combust Inst. https://doi.org/10.1016/j.proci.2018.06.199

  18. 18.

    Ferkul P, Sacksteder K, Greenberg P, Dietrich D, Ross H, Tien JS, Altenkirch R, Tang L, Bundy M, Delichatsios M Combustion experiments on the Mir Space Station. AIAA-99-0439. https://doi.org/10.2514/6.1999-439

  19. 19.

    Emmons HW (1956) The film combustion of liquid fuel. Z für Angew Math Mech 36:60–71

  20. 20.

    Consalvi JL, Porterie B, Loraud JC (2005) A blocked-off region strategy to compute fire scenarios involving internal flammable targets. Numer Heat Trans 47:419–441. https://doi.org/10.1080/10407790590919234

  21. 21.

    Zhang J, Wang Y, Lu X (2005) Study on melting behavior of polymers during burning. Fire Saf Sci 8:637–646. https://doi.org/10.3801/IAFSS.FSS.8-637

  22. 22.

    Gauthier E, Laycock B, Cuoq FJJM, Halley PJ, George KA (2012) Correlation between chain microstructural changes and embrittlement of LLDPE-based films during photo- and thermo-oxidative degradation. Polym Degrad Stab. https://doi.org/10.1016/j.polymdegradstab.2012.08.021

  23. 23.

    Guo H, Liu F, Smallwood GJ, Gülder ÖL (2006) Numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene-air diffusion flame. Combust Flame 145:324–338. https://doi.org/10.1016/j.combustflame.2005.10.016

  24. 24.

    Khan MM, Tewarson A, Chaos M (2016) Combustion characteristics of materials and generation of fire products. In: Hurley MJ (ed) SFPE handbook of fire protection engineering, 5th edn, Springer, New York, pp 1143–1232

  25. 25.

    Annamalai K, Sibulkin M (1979) flame spread over combustible surfaces for laminar flow systems part I: excess fuel and heat flux. Combust Sci Technol 19:167–183

  26. 26.

    Rangwala AS (2016) Diffusion flames. In Hurley MJ (ed) SFPE handbook of fire protection engineering, 5th edn. Springer, New York, pp 350–372

  27. 27.

    Qin Z, Lissianski VV, Yang H, Gardiner WC, Scott SG, Wang H (2000) Combustion chemistry of propane: a case study of detailed reaction mechanism optimization. Proc Combust Inst 28:1663–1669. https://doi.org/10.1016/S0082-0784(00)80565-2

  28. 28.

    Lindstedt RP (1994) Simplified soot nucleation and surface growth steps for non-premixed flames. In: Bockhorn H (ed) Soot formation in combustion. Springer, Berlin, pp 417–441

  29. 29.

    Nmira F, Consalvi JL, Demarco R, Gay L (2015) Assessment of semi-empirical soot production models in C1–C3 axisymmetric laminar diffusion flames. Fire Saf J 73:79–92. https://doi.org/10.1016/j.firesaf.2015.03.005

  30. 30.

    Moss JB, Aksit IM (2007) Modelling soot formation in a laminar diffusion flame burning a surrogate kerosene fuel. Proc Combust Inst 31:3139–3146. https://doi.org/10.1016/j.proci.2006.07.016

  31. 31.

    Naggle J, Strickland-Constable RF (1962) Oxidation of carbon between 1000°C and 2000°C. In: Proceedings of the 5th conference on carbon. Pergamon Press, London, pp 154–164

  32. 32.

    Fenimore CP, Jones GW (1967) Oxidation of soot by hydroxyl radicals. J Phys Chem 71:593–597. https://doi.org/10.1021/j100862a021

  33. 33.

    Rothman LS, Gordon IE, Barber RJ, Dothe H, Gamache RR, Goldman A, Perevalov VI, Tashkun, Tennyson J (2010) HITEMP: the high-temperature molecular spectroscopic database. J Quant Spectrosc Radiat Transf 111:2139–2150. https://doi.org/10.1016/j.jqsrt.2010.05.001

  34. 34.

    Chang H, Charalampopoulos T (1990) Determination of the wavelength dependence of refractive indices of flame soot. Proc R Soc 430:577–591. https://doi.org/10.1098/rspa.1990.0107

  35. 35.

    Modest MF, Zhang H (2002) The full-spectrum correlated-k distribution for thermal radiation from molecular gas-particulate mixtures. ASME J Heat Transf 124:30-38. https://doi.org/10.1115/1.1418697

  36. 36.

    Modest MF (2003) Radiative heat transfer. Academic Press, London

  37. 37.

    Modest MF, Riazzi RJ (2005) Assembly full spectrum k-distribution from a narrow band database: effects of mixing gases, gases and non-gray absorbing particles and non-gray scatters in non-gray enclosures. J Quant Spectrosc Radiat Transf 90:169–189. https://doi.org/10.1016/j.jqsrt.2004.03.007

  38. 38.

    Chui EH, Raithby GD, Hughes PMJ (1992) Prediction of radiative transfer in cylindrical enclosures with the finite volume method. AIAA J Thermophys Heat Transf 6:605–611. https://doi.org/10.2514/3.11540

  39. 39.

    Chen CH, T’ien JS (2007) Diffusion flame stabilization at the leading edge of a fuel plate. Combust Sci Technol 179:3–19. https://doi.org/10.1080/00102208608923938

  40. 40.

    Markstein GH, De Ris J (1985) Radiant emission and absorption by laminar ethylene and propylene diffusion flames. Proc Combust Inst 20:1637–1646. https://doi.org/10.1016/S0082-0784(85)80659-7

  41. 41.

    Kent JH (1986) A quantitative relationship between soot yield and smoke point measurements. Combust Flame 63:349–358. https://doi.org/10.1016/0010-2180(86)90004-0

Download references

Acknowledgements

The authors feel grateful to the Centre National d’Etudes Spatiales for its financial support under Contract No. 130615.

Author information

Correspondence to J. L. Consalvi.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Guibaud, A., Consalvi, J.L., Orlac’h, J.M. et al. Soot Production and Radiative Heat Transfer in Opposed Flame Spread over a Polyethylene Insulated Wire in Microgravity. Fire Technol 56, 287–314 (2020). https://doi.org/10.1007/s10694-019-00850-8

Download citation

Keywords

  • Insulated wire
  • Opposed-flow flame spread
  • Microgravity
  • Soot production
  • Heat transfer