Toluene Combustion in the Presence of Ceria Nanoparticles: A Shock-Tube Study
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abstract
A novel approach toward the study of nanoparticle-aided combustion of hydrocarbons has been developed using a shock tube, and the first measurements of the effect of ceria nanoparticles on toluene soot yield are reported. By utilizing a shock tube, the effect of additives such as ceria can be studied at the time scales of the soot inception period. The technique involves the introduction of fuel and oxidizer separately through a two-stage injection procedure in which the particle-laden condensed-phase fuel is injected using a syringe and the oxidizer, premixed with inert gas, is introduced at two separate locations to promote turbulent mixing within the shock tube. In the present work, two concentrations of ceria, of chemical composition CeO1.63, were employed to examine the effect on soot production of toluene over the range of temperature 1588 K - 2370 K under dilution conditions in which reflected-shock pressure was maintained near 1.5 atm. The ceria nanoparticles were synthesized using a microemulsion technique which utilizes sodium dioctyl sulfosuccinate (AOT), a surfactant, to retard the natural tendency of nanoparticles to form aggregates. Use of surfactants is necessary to ensure a homogeneous distribution within the condensed-phase (carrier) fuel and, to make certain that the observance of any effects is due to the nanoparticles, mixtures of toluene and AOT were also examined. The results indicate that the reduced soot formation observed in the experiments is possibly due more to the surfactant than the ceria nanoparticles. Furthermore, to identify the impact of ceria on the kinetics of toluene combustion, ignition delay times of toluene were investigated and recent results from gas-phase experiments are reported. 2008 by the American Institute of Aeronautics and Astronautics, Inc.
