A transient two-dimensional chemically reactive flow model: Fuel particle combustion in a nonquiescent environment

A numerical model based on the spectral element method has been developed to simulate transient two-dimensional chemically reactive flows. Our numerical formulation is not only capable of including realistic transport and chemical kinetics but is also sufficiently flexible to model combustion systems in various complex geometries. In the present study, this numerical method has enable, for the first time, the two-dimensional transient solutions of two different fuel particle combustion problems in a nonquiescent environment that includes coupled convection, detailed molecular transport, and elemental chemical kinetics. The simulations performed reveal the effects of low Reynolds number flow on the ignition and flame structure development of a spherical nonpremixed CO/air flame and on the gasification behavior of a small (200 μm in diameter) carbon particle. At a Reynolds number of unity, the steady-state non-premixed CO/air flame is spherically symmetric; however, during the ignition process, deviations from spherical symmetry are significant. As for the carbon particle simulation, the burning mode of the particle is sensitive to the Reynolds number (in the range of 0<Re<10). It changes from a fast burning mode at Re=1 (or less) with the presence of a reacive boundary layer surrounding the particle to a heterogeneous kinetics-controlled, slow burning mode at Re=10 with nontrivial gas-phase chemistry in the wake.