OCR Text |
Show 2 Farmer's one [4] are classified into phenomenological model. In Tesner's model, the numerical equation, which expresses the total amount of soot, is based on the results obtained by the experiment of diffusion flame. It is simple enough to apply this model to any simulations related with soot formation. However, it is necessary to determine appropriate empirical constants used in the model, while the constants are changed by concentration of soot particles, flame structure and fuel. In Farmer's model, the rate of soot formation is expressed as Arrhenius type formula. While both models are used to estimate the total amount of soot, the models are therefore insufficient to estimate the shape of soot aggregate. Nakatake et al. [4] applied both models to the soot formation in diesel combustion and concluded that the rate of soot formation is predicted well with combining both models. On the other hand, Ivie et al. [1] simulated the synthesis of the C B by benzene pyrolysis in a C B furnace using a numerical model which includes four kinds of reactions, i.e. pyrolysis, oxidation, surface growth and coagulation reactions of the soot particles. The feature in their model is to calculate simultaneously the rates of both chemical and physical aggregation reactions. However, the comparison of simulated and experimental data was carried out under only one isothermal condition. Moreover Yoshikawa et al. [5, 6] simulated the process which includes heavy oils pyrolysis, combustion and reaction to produce a precursor of CB. They used a numerical model based on PAH(Polycyclic Aromatic Hydrocarbon) model [7] suggested by Frenklach et al. [8-11]. This P A H model can calculate a combustion process at the elementary process level. They clarified the soot yield-bell. However, they insufficiently compared calculated data with experimental ones, and did not estimate the shape of soot, because of no considerations of coagulation reactions of soot particles. In this study, we carry out to the experiment to form the soot by the pyrolysis of 1mol% benzene(in 99mol% nitrogen) in an alumina tube, which was kept at 1573K, with variations of residence time(0.05 to LOOsec), and measure the diameter of soot particles. In addition, the aggregates are classified into four kinds of shape from the image analysis of soot. Furthermore we develop the simulation model, which is based on the work of the Ivie et al. [1]. Our model is able to predict the diameter change and the existence ratio of four kinds shape of soot by benzene pyrolysis. We consider the influence of an aggregate shape upon the diffusion coefficient of a particle and also the temperature profile in the reactor. Experimental |