Numerical computations of premixed propane flame in a swirl-stabilized burner: Effects of hydrogen enrichment, swirl number and equivalence ratio on flame characteristics

This paper investigates the effect of hydrogen addition and swirl intensity and equivalence ratio on characteristics of premixed C3H8-air flame, in a model burner. The numerical simulation is carried out using Reynolds Average Navier-Stokes (RANS) technique with Realizable k-ε as a turbulence closure model. The turbulence-chemistry interaction scheme is modeled using FR/EDM with three-step global reaction mechanism. The study is performed with two lean regimes of Φ = 0.3 and 0.5 and four volumetric fractions of hydrogen XH2 = 10%, 20%, 40% and 80% for two swirl numbers Sn = 0.6 and 1.05. First, validations of the computational models with the experimental data are performed, and a good agreement is found. Second, the effect of H2 addition to extended lean flammability limits is addressed. Third, the differential diffusion effects on the accuracy of the predictions are studied and therefore should always be accounted for. Fourth, the effect of H2 addition on the flow development and the flame characteristics is investigated. Results indicate that the H2 addition affects strongly the flame structure. Two types of enriched flame are found, Balloon-type and M-type flames. The effects of H2 addition on the reaction rates of C3H8 and H2, the flow species and CO emissions are also analyzed.