Measurements and Modeling of Spherical CH2F2-Air Flames
Michael J. Hegetschweiler, John L. Pagliaro, Lukas Berger, Raik Hesse, Joachim Beeckmann, Heinz Pitsch, Gregory T. Linteris
The burning velocity of mixtures of the refrigerant R-32 (CH2F2) with air over a range of equivalence ratios are studied via spherically expanding flames SEFs in a large, optically accessible spherical chamber at constant pressure. Shadowgraph images from a high-speed video camera are analysed to yield flame radius as a function of time. Data reduction techniques are explored and direct numerical simulations of the flame are performed with the FlameMaster code, using detailed kinetics. The flame radius as a function of time is accurately predicted by the simulations. Flame stretch and thermal radiation (using an optically thin model) occur simultaneously and make extraction of the unstretched burning velocity from the experimental data difficult. For these low burning velocity flames, the numerical simulations show that stretch and radiation effects are particularly important, and different data reduction schemes can have large effects on the inferred burning velocity.