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/ m 2 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 usuallyused thermally-thin assumption throughout the LDPE coating is not strictly valid.

The objective of this work is to quantify for the first time soot-related radiative heat transfer in opposed flow flame spread in microgravity. This article presents experimental results obtained in parabolic flight facilities. A flame is established over a solid cylindrical polyethylene coated metallic wire and spreads at a steady rate, in low velocity flow conditions allowed by the absence of buoyancy. Implementing the Broadband Modulated Absorption/Emission (B-MAE) technique, the two-dimensional fields of soot volume fraction and temperature are obtained for the first time in flame spread configuration over an insulated wire in microgravity. The consistency of the results is assessed by comparing results from independent experimental runs. From these fields, radiative losses attributed to soot in the flame are computed at each location. This map of radiative losses together with the profile of the wire surface are then used as inputs to a novel experimental approach that enables the assessment of soot radiative heat feedback to the wire. Results are extracted from a specific case of a flame propagating over a polyethylene coated Nickel-Chrome (NiCr) wire at nominal pressure. The oxidizer, composed of 19% oxygen and 81% nitrogen in volume is blown at opposed flow parallel to the wire at a velocity of 200 mm.s −1. This new approach provides the first detailed quantitative measurements which are required to check the relevance

A new optical setup and its associated post-processing have been designed in an effort to map soot related quantities in an axisymmetric flame spreading over solid samples in microgravity environment where setup compactness constraints are stringent. Extending the well-established spectral modulated absorption/emission (S-MAE) technique that uses lasers as light sources together with a sophisticated optical arrangement, LEDs have been associated with broadband optics to enable the broadband modulated absorption/emission (B-MAE) technique. The design and the cautious assessment of the original B-MAE setup are reported in the present paper. Algorithms that need to be reformulated for broadband integration are first validated retrieving both two-dimensional soot temperature and volume fraction fields produced by numerical simulations. Then, these fields are measured with both B-MAE and S-MAE techniques in a largely documented steady laminar non-premixed coflow ethylene/air flame established at normal gravity. Thus, outputs delivered by the B-MAE technique can be compared with those obtained with the S-MAE setup. Both soot temperature and volume fraction are shown to be decently measured by the B-MAE technique. As the spread of the non-buoyant flames to be investigated in the near future is especially driven by radiative heat transfer, the discrepancies between both techniques outputs are commented in the light of the fields of local radiative loss computed from the fields measured by both techniques. As a result, the fields delivered by the B-MAE technique are expected to provide ground-breaking insights into the control of flame spread in the absence of buoyancy, therefore manned spacecraft fire safety.