Προυπολογισμός λειτουργίας κεραμικών φίλτρων αιθάλης

Abstract

The new emission control regulations for the diesel engines impose less soot particulate emissions. The particulates are dangerous and very harmful for the enviroment. Today, the CO and HC emissions of the diesel engines are already very low but the NOx and particulates emissions are still high. These are the goal of the modern emission control technologies. The reduction of the NOx and particulates emitted can be reduced with improvements in the engine design, fuel, oil and additive technologies and with exhaust after treatment. The soot filters collect the particulates from the diesel engine exhaust gas. The filter efficiency can be over 90% and the durability is satisfactory. When the trap's soot load is high the regeneration is necessary to retain the efficiency and to avoid the filter failure. The regeneration methods must be further developed in order to avoid problems cause from the heat released during the combustion of the soot. These problems must be completely solved, for the soot traps to become a common used emission control device in passenger cars. Today, soot filters in passenger cars are used only from PSA, but the emission control regulations in the future will impose every vehicle with a diesel engine to have reduced particulates emissions. That will lead in the wide use of soot filters. The design and improvement of soot traps can be much more easier, more efficiently and with less cost with the use of soot filter simulation software. Many tests and modifications can be made, avoiding the experimental cost. Besides, many parameters of the filter function can be computed and analysed faster and reliably. The diploma thesis with title 'Modeling of ceramic soot filters' was conducted within the purposes of the research project 'Development of computational tools for exhaust after-treatment systems design optimization' for PSA Peugeot Citroen, at the Laboratory of Thermodynamics and Thermal Engines, of the Department of Mechanical and Industrial Engineering. The goal of the diploma thesis is the presentation of the basics of soot traps and the calculations conducted with the soot filter simulation software Catwall. The validation of the model as well as to find the points that need to be improved are a part of the thesis. The properties of the materials, soot and insulation were defined and there was an effort to choose the most suitable kinetics scheme for the soot combustion and the additive reaction. The first chapter describes the emissions of the diesel engines, the emissions regulations, the soot particulates, the soot filters basics, regeneration, materials and the fuel additive. The second chapter deals with the modeling of the experiments of the small filters, conducted by PSA. The experiments are described and the results from the calculations are compared with the measurements with SiC and Cordierite filters. In the next chapter the experiments conducted with insulated filters by the IFP are described and then the temperature and ΔΡ calculations are presented. The effort to choose the most suitable kinetics parameters follows as well as the comparison of 4 kinetics schemes for the soot combustion without additive. The forth chapter describes the experiments conducted at the Laboratory of Thermodynamics and Thermal Engines. The results from the calculations are compared with the measurements with SiC and Cordierite filters and there is also an effort to choose the most suitable kinetics scheme, with a comparison of 4 kinetics schemes for the soot combustion with additive. The model is described in appendix I and the preprocessing and postprocessing of the experimental data are presented in appendix II. The conclusions from the calculations are presented in order to improve the source code and to suggest the conduction of new experiments, which will help in achieving this goal. Finally many remarks are made on the results, which confirm the literature data or describe the effect of the regeneration parameters on the calculations, which need to be further searched through.