Simulation For The Fractal Growth Of Particle Matter From Diesel Engine

As we know, the air pollution is more and more serious. PM is the mainpollutants of diesel engine, and it is one of the atmospheric pollutants which isharmful to human health as well. So it is significant to research the means to controlthe PM for the development of diesel. It would be very useful to research theformation and physical characteristic. Though people have worked on this field fordecades, the mechanism of soot formation is not clearly by far. Therefore，thethoroughly research on mechanism of particle formation is very necessary for ourhealth, environment protecting and application of diesel.The soot generated abroad conducted researches in the working mechanism wereintroduced to the model established the experience model; the semi-experiencedmodel and detailed model are briefly described. Describes the numerical methodsused to solve the model and explains the basis of the experimental results, we canconclude that soot structures with fractal characteristics that conclusion.The basic theory of fractal is introduced. The fractal dynamics of a typical model–DLA and BA, as well as the important parameters of fractal–the fractaldimension-are discussed. Based on the dynamic Monte Carlo method and the DLAmodel, one kind of soot growth model is built. The methods for calculating thestructure of cohesion calculation parameters such as volume, surface area, and fractaldimension and collision frequency is described. The random incremental algorithm tocalculate the radius of the structural parameters such as spatial cohesion is presented.The dynamic Monte Carlo method is solved numerically by computer. Bysolving the model, the body of fractal growth process was simulated and experimentalaggregates observed in the resulting PM were compared on the morphology. Thegrowth and cohesion in the structural parameters such as body fractal changes indimension, volume, surface area and other parameters were analyzed. Compared theeffects of single-particle aggregates formed by grafting collision condensation formedon the difference between the morphology and structure of the body. The influencesof different pressure on the fractal dimension of cohesion and collision frequency ofthe body were examined. The probability of adhesion set based on a simplified analysis of the effects of different probability of condensate morphology andparameters. The dimension of the model is modified further. At last, several methodsare introduced to calculate the fractal dimension. In this dissertation, the fractaldimension of coalescence and aggregation are calculated by box-counting algorithm,respectively.