Research For Diesel Engine Soot Particle Evolution Based On Monte Carlo Method

Hazy weather strikes us frequently in recent years, which leads to growing concern about the air pollution. Particulate matters from diesel engine are the major pollution sources. Soot particles not only reduce the air visibility, contaminate water, but also pose threats to human health. The more complicated of soot chemical composition, the more harmful to human health. Meanwhile, particle size plays an important role on human health. Soot formation is very complex, which includes the gas-phase reaction kinetics and the particle dynamics evolution. Moreover, soot particle size distribution function(PSDF) varies significantly in the growth evolution process. Currently, researches on the formation mechanism of soot particles only focuse on the gas-phase chemical reaction mechanism, theoretical methods and experimental methods are frequently employed. The particles dynamics process largely depends on experiments.This paper gives a brief introduction of soot model development and analyzes the advantages and disadvantages of various soot models, and then introduces the particle population balance model and several numerical methods for solving particle population balance equation(PBE), which provide a theoretical basis for the computing platform. This work base on the theoretical approach of PBE to build a detailed soot model, and the Monte Carlo method is used to solve this model. Soot particle dynamics evolution computing platform also be built with Fortran language. The detailed chemical kinetic mechanism was used, which includes the pyrene molecules formation. The soot formation process is detailed simulated in a perfectly stirred reactor(PSR) model and the laminar one-dimensional premixed flames. Some results of soot formation, such as soot density number and volume fraction are obtained base on the above computation platform. Meanwhile, the dynamics evolution processes, such as nucleation, coagulation, and surface reactions are analyzed in detail, the detailed information of soot PSDF is obtained. The effects of equivalent ratio and carbon dioxide addition on soot formation in the laminar premixed flames are investigated by numerical simulation. Results showed that soot particle density number and volume fraction increased along with the equivalent ratio rises. The addition of carbon dioxide reduces the particles nucleation rate and the particles growth rate, and promotes the soot oxidation rate by oxygen and hydroxide radical. Soot particle density number and volume fraction is decreased, which inhibit the soot formation finally.The theory of the soot particle growth evolution has been systematically studied, the findings may provide a reference for a better understanding of soot formation mechanism. This research has great significance and value on soot particulate emissions control.