Modeling Soot Formation in a Stirred Reactor

The formation of carbonaceous particulate matter and polycyclic aromatic hydrocarbons has recently been studied (Stouffer, et al, 2002 and Reich, et al, 2003) in a toroidal well-stirred reactor using ethylene as the fuel, with and without the additive ethanol. In the later work, modeling of the gas-phase species was performed and compared to the experimental trends. In the present study, a modified version of the CHEMKIN-based code for ‘perfectly stirred reactors’ has been used to model soot particle formation, including computations of particle mass and smoke number. Detailed soot formation routines have been extracted from Hall and coworkers (1997), who modeled soot formation in flames. Experimental trends are accurately modeled by the code with quantitative accuracies generally within 50%. The importance of accurate knowledge and control of reactor temperature is discussed. In fact, scatter in the original experimental study can be largely attributed to inadequate temperature control. Speculation for differences between the model and experiment are offered while additive effects and the well known ‘soot bell’ are discussed. For the initial experiments examined by Stouffer et al, the effect of the additive is largely due to temperature differences.