| Résumé | It has been confirmed that the addition of CO2 to a diffusion flame suppresses the formation of soot. However, a consensus has not been reached regarding the mechanism of the suppression, especially the chemical effect. Some researchers claimed that the effect of CO2 addition on soot formation is primarily due to the thermal and dilution effects, while others argued that there is also noticeable chemical effect. Among the later group, some of them thought that the chemical effect is primarily caused by the enhanced soot oxidation process, while others believed that the chemical suppression is also a result of the reduced concentration of soot precursors and atomic hydrogen. Most previous studies on the effect of CO2 addition on soot formation were conducted by experiments. Although experiments can capture the natural phenomena, it is hard to separate the coupled effects of different mechanisms. Numerical simulation has an advantage to separate the different mechanisms. However, in the past, usually simplified soot models were employed, or soot was totally neglected in the simulation, because of the limit of computation power and the lack of detailed soot formation model. Significant progress has been made in the development of relatively detailed soot formation models. These models can capture many phenomena of soot formation in various flames. This paper further investigates the effect of CO2 addition on soot formation in a laminar diffusion flame by numerical simulation using a relatively detailed soot model. The purpose is to use the details from numerical results to identify if there is chemical effect and how the chemical effect suppresses soot formation, when CO2 is added to a laminar diffusion flame. The paper focuses on the fuel side addition, i.e. CO2 is added to the fuel stream. |
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