| Résumé | This paper presents a numerical and experimental study on the structure and soot formation of atmospheric pressure coflow laminar DME/air and CH4/air diffusion flames. Detailed thermal and transport properties were used in the simulation. The combustion chemistry was modeled using a reduced mechanism for the DME flame and GRI Mech3.0 for the methane frame. A semi-empirical soot formation model was used. In the experiments, the flames were generated using the standard NRC coflow laminar flame burner. Un the condition of constant carbon flow rate, the visible flame height of the DME flame is only about two thirds of that of the CH4 flame. For the methane flame, the soot field (distribution, visible flame height, and peak volume fraction) predicted numerically is in reasonably good agreement with the present experimental observation and experimental data in the literature. However, the same simplified soot model fails miserably when applied to the DME flame. In this flame, the predicted soot volume fractions in the centerline region are about two orders of magnitude larger than the values measured using a laser-induced incandescence technique, suggesting that the soot volume fractions in flames fueled with DME cannot be reliably modeled using the simplified soot model developed for conventional hydrocarbon flames without modification. |
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