EXHAUST PARTICLE SIZE DISTRIBUTIONS PRODUCED BY DIESEL AND SPARK IGNITION ENGINES: COMPARISON OF THEORY AND EXPERIMENT.

Although particles produced by diesel and spark ignition engines have been studied for many years, only recently have techniques become available for detailed examinations of the physical and chemical properties of such particles. This paper will focus on physical measurements, placing emphasis on particle size distribution measurements. The work described in this paper represents the beginning of an attempt to understand some of the processes which govern the formation, growth, and decay of carbonaceous particles in both spark ignition (premixed charge) and diesel (stratified charge) engines. The exhaust particle size distribution produced by both spark ignition and diesel engines are examined in terms of a coagulation model. The model predicts that the most important parameters influencing the exhaust particle size distribution are the size and concentration of primary particles formed by combustion and the degree of stratification within the combustion chamber. Size distributions predicted by the model are compared with actual size distributions produced by diesel engines and non-catalyst, unleaded fuel spark ignition engines.