Contents lists available at ScienceDirect Fire Safety Journal journal homepage: www.elsevier.com/locate/ firesaf Effect of oxygen concentration on the combustion of horizontally-oriented slabs of PMMA David Alibert a, ⁎ , Mickaël Coutin b , Maxime Mense b , Yannick Pizzo a , Bernard Porterie a a Aix-Marseille Université(AMU), CNRS, IUSTI UMR 7343, Laboratoire commun ETiC, 13453 Marseille, France b Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES, SA2I, Laboratoire commun ETiC, Cadarache, 13115 Saint-Paul-Lez-Durance, France ARTICLE INFO Keywords: Reduced oxygen atmosphere Heat transfer Pyrolysis PMMA CADUCEE ABSTRACT The aim of this study is to collect data on the combustion of horizontally-oriented poly(methyl methacrylate) (PMMA) samples in reduced oxygen atmospheres for CFD model validation. Experimental results relating the oxygen concentration to the burning behavior of 3-cm-thick clear PMMA slabs are discussed. Experiments are conducted in the controlled atmosphere calorimeter of IRSN called CADUCEE. Pyrolysis and combustion of 0.2×0.2 m 2 horizontally-oriented PMMA samples are studied varying the oxygen molar fraction from 0.210 to 0.180, extinction occurring at about 0.175. The measured quantities are the regression rate of the slab, mass loss rate, temperatures and total and radiative heat fluxes at the center of the slab. All experiments are carried out twice, showing a good repeatability. It is found that the slab regression rate, mass loss rate and heat fluxes at the slab center decrease significantly with the oxygen concentration, while the gas temperature is much less sensitive. Most notable is that the radiative and convective contributions to the total heat flux remain almost constant, respectively 0.65 and 0.35. It is also found that both heat fluxes and mass loss rate exhibit linear oxygen-concentration-dependent behavior. From an energy balance and current average values of the total heat flux and regression rate at the center of the slab, the present study obtains a heat of gasification value of 2.25 MJ kg -1 , in agreement with literature data. 1. Introduction The effect of oxygen on fuel combustion is of primary importance for fire safety in nuclear plant compartments as well as buildings. The oxygen quantity available for combustion depends on the oxygen consumption by the fire and on the air renewal rate of the mechanical ventilation system or openings. Under-oxygenation of the ambient air will lead to a decrease of the heat flux feedback from the flame to the fuel surface, which in turn will lead to a decrease in mass loss rate (MLR). This is accompanied by changes in other properties, such as the regression rate of the slab, gas temperature and composition, and total and radiative heat fluxes. A model developed by Utiskul et al. [1] may be used to express the MLR as a function of the oxygen molar fraction. This model was based on the Quintiere approach [2] and some simplifying assumptions. By assuming a small B number and neglecting the flame radiative effects, Utiskul et al. obtained the following relationship m m X q L ̇ ″ = ̇″ 0.21 + ̇ ″ X O ext r G 21 , O 2 2 (1) More recently, Nasr et al. [3] developed a model to determine the fuel mass loss rate in a confined and mechanically ventilated compart- ment fire using a global approach. This model was based on the energy balance at the fuel surface without neglecting the radiative heat flux from the flame and considering that the term ln(1+B)/B is different from 1. They obtained the fuel mass loss rate as ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ m h Lc l Y Δh r χ c T T σε L α η σ L ε T T σ L T T ̇ ″ = n(1 + B) B (1 − )− ( − ) + (Y + ) + (1 − )( − )− ( − ) X conv Gp O c r p s G O G g s G s ∞ f 4 f 4 4 4 ∞ 4 O 2 2 2 (2) Few correlations have been established to express the MLR as a function of the oxygen concentration from experimental results. Tewarson and Pion [4] determined the MLR of various commercial samples of plastics, at a small scale, in normal and reduced-oxygen atmospheres. For a limited range of molar fraction of oxygen, they found a linear correlation between the MLR and the oxygen concen- tration for all the combustibles studied http://dx.doi.org/10.1016/j.firesaf.2017.03.051 Received 15 February 2017; Received in revised form 24 March 2017; Accepted 27 March 2017 ⁎ Corresponding author. E-mail address: david.alibert@univ-amu.fr (D. Alibert). Fire Safety Journal xxx (xxxx) xxx–xxx 0379-7112/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Alibert, D., Fire Safety Journal (2017), http://dx.doi.org/10.1016/j.firesaf.2017.03.051