Development and Applications of Detailed Kinetic Models for the Soot Particle Size Distribution Function
Sammanfattning: Two different mathematical methods of implementing a detailed kinetic soot model have been employed in this work. The theoretical description of the soot modeling employed in this work is divided into three parts. Initially a detailed kinetic soot model is described from a chemistry and physics perspective. The soot model is then elaborated into mathematical form, starting with the formulation of the method of moments. Later on a thorough description of the sectional mathematical formulation of the detailed kinetic soot model is given. The sectional method is a new addition to the toolbox developed and used by the kinetic workgroup at Lund University. The sectional method and the moment method are compared, with the focus of doing a theoretical validation of the sectional method. Where discrepancies between the models exist, due to choices of approximations and discretizations, these are investigated and explained. The validation is carried out in the framework of a 0-dimensional code usually used for describing the process of ignition in perfectly stirred combustion reactors. A 0-dimensional reactor tool is also used, in which precalculated or premeasured chemistry profiles are read in. Based on the read-in profiles soot formation is calculated. Features as well as limitations of the sectional method are investigated. The sectional method is also validated using experimental data. A laminar premixed flame is modeled and the calculated profiles of the soot particle size distribution function are compared to experimentally measured distributions. Comparisons are made for different flames with different temperatures. An investigation on how the sectional method performs with another well known soot model is also performed. The moment method and the sectional method are both applied in different turbulent non-premixed combustion cases. In most of the work the soot models are used within the general turbulent combustion modeling approach called the flamelet model. Turbulent non-premixed combustion is also modeled using a stochastic reactor model. Turbulent diffusion flames are simulated using the flamelet model. The flamelet model describes the turbulent flame as an ensemble of 1-dimensional laminar diffusion flames, so-called flamelets. The interaction between flowfield and chemical reactions is described, while decoupling the actual calculations of chemistry and flowfield. Both the moment method and the sectional method have been applied within the flamelet model to study turbulent freely propagating diffusion flames. By applying the sectional method in a turbulent flame, spatially detailed information on the evolution of the soot particle size distribution was obtained. This is novel and has taken the study of soot formation and specifically the study of the evolution of the soot particle size distribution into a new area. The moment method in combination with the flamelet model was also used to investigate diesel engine combustion. A stochastic reactor tool is used to model carbon black (i.e. soot) formation in a carbon black reactor. This tool is a 0-dimensional model, assuming spatial homogeneity can be replaced by statistical homogeneity.
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