Chemiions and nanoparticle formation in diesel engine exhaust

The nanoparticles (diameter < 50 nm) emitted by diesel engines have receive d increasing attention due to their potential health effects. We propose th at chemiions generated during combustion play an important role in the form ation of these nanoparticles. The predicted nanoparticle properties based o n our chemiion theory closely match measurements in terms of total nanopart icle concentrations, and their sensitivity to fuel sulfur contents and seco nd stage dilution conditions, while the classical homogeneous nucleation fa ils to explain these observed properties. Our study indicates that total nu mber of nanoparticles formed is very sensitive to chemiion concentrations, and we propose a technique to effectively reduce vehicle nanoparticle emiss ions by removing ions in the exhaust.