科研之友
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摘要
In this work, the behavior of a 200-mu m spherical carbon particle moving in a hot environment mainly consisting of O-2 and CO2 was investigated numerically. The main goal of this work was to study the influence of the particle velocity, temperature, and composition of the surrounding gas on the carbon consumption rates. The particle investigated was placed in a uniform oxygen/carbon dioxide mixture at different Reynolds numbers corresponding to different laminar flow regimes. The ambient temperature was systematically varied in the range of 1000-3000 K, and the mass fraction of O-2 was varied between 0.12 and 0.36. To solve the Navier-Stokes equations for the flow field coupled with the energy and species conservation equations, a finite volume solver was applied. In addition to the solid carbon, the model incorporates six gaseous chemical species (O-2, CO, CO2, H-2, H2O, and N-2). The semiglobal reaction mechanism includes the forward and backward water-gas-shift reaction, one reaction for CO combustion, and four heterogeneous reactions. The ambient medium was assumed to be nearly dry (Y-H2O = 0.001). The numerical results were carefully validated against experimental data published in the literature (Bejarano and Levendis, Combust. Flame 2008, 153, 270-287). In particular, it was shown that taking into account losses from radiation (gas-gas, gas-solid) brings the results closer to the experimental data. Additionally, the influence of the gas-gas radiation effect on the integral characteristics of the oxidizing particle was studied. In particular, the results are discussed with a focus on the systematic variation of the ambient-gas temperature and Reynolds number. We found out that increasing the Reynolds number enhances species transport to the particle surface and shifts particle oxidation from a diffusion-controlled to a kinetically controlled regime.
- 出版日期2013-4-24
