Numerical study of carbonaceous nanoparticle formation behind shock waves

By incorporating complex chemical kinetics for both gaseous and particulate phases with a fixed sectional aerosol dynamics model, a detailed description of the properties of carbonaceous nanoparticles formed in the pyrolysis of carbon suboxide behind a reflected shock wave can be obtained. The model successfully predicted the induction time, growth rate and particle yield for the shock tube experiment. The calculated time-dependent particle volume fractions were in good agreement with the measured optical densities, and the averaged particle diameters were in reasonable agreement with the measured particle size using LII (laser-induced incandescence) and TEM (transmission electron microscope). The predicted particle size distribution as a function of residence time showed an evolution from the power law shape to a bi-modal shape. The temperature dependence of particle properties has been also investigated. The second bell at the high temperature range, which has been argued as resulting from particle nucleation behind the incident wave during the experiment, was found in the numerical simulation of particle formation behind the reflected shock wave where no incident wave is included. Analysis of the simulation results showed that the double bell-shaped particle yield arises from the different particle nucleation timescales and the changing surface growth rates at different temperatures.

Keywords:

• Carbonaceous nanoparticle
• sectional model
• carbon suboxide
• shock wave
• particle size distribution

Acknowledgements

This work has been supported by Auto21 Canada program and the Natural Sciences and Engineering Research Council of Canada (NSERC). The authors also wish to thank Dr A. Eremin, Dr S. N. Rogak and Dr S. H. Park for the discussions on experiments and aerosol codes.