Data reduction considerations for spherical R-32(CH2F2)-air flame experiments

• Published in: Combustion and flame 2022-03, Vol.237 (C), p.111806, Article 111806
• Main Authors: Hegetschweiler, Michael J., Pagliaro, John L., Berger, Lukas, Hesse, Raik, Beeckmann, Joachim, Bariki, Chaimae, Pitsch, Heinz, Linteris, Gregory T.
• Format: Article
• Language: English
• Subjects: Burning velocity; Data reduction; Equivalence ratio; Flame stretch; Laminar flame speed; Mathematical models; R-32; Radiation; Refrigerant Flammability; Simulation
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2021.111806

The burning velocities of mixtures of refrigerant R-32 (CH2F2) with air over a range of equivalence ratios are studied via shadowgraph images of spherically expanding flames (SEFs) in a large, optically accessible spherical chamber at constant pressure. Numerical simulations of the 1-D, unsteady, spherical flames incorporating an optically thin radiation model and detailed kinetics accurately predict experimental results for a range of equivalence ratios. For these low burning velocity flames, the effects of stretch and radiation occur simultaneously and make extraction of the unstretched burning velocity from the experimental data difficult. Different data reduction approaches are shown to have large effects on the burning velocities inferred from the experiments and simulations. A new flame radius tracking approach for the experimental images is shown to provide improved agreement of the burned gas velocity variation with stretch predicted by the simulations and helps to compensate for mild flame distortion due to buoyancy.