Laboratory Studies of Gas-Particle Reaction Kinetics of Particulates Emitted from Aircraft
(Summer Research Institute, PNNL Scope #16248)
EMSL Project ID
18418
Abstract
The proposed research involves design parameters of an experiment used to study the heterogeneous reaction kinetics of particulates emitted from aircraft. Preliminary investigations of heterogeneous reactions using other particulates with the experimental setup have revealed a highly spatial dependence on the reaction rates. A theoretical treatment of the reaction kinetics tells one that said rate depends on the diffusion length of the reacting gas (ppm) in the gas mixture. The observed spatial dependence of reaction rates results from diffusion boundary layer thickness growth. This boundary layer depends on several experimental parameters (mass flow rate, tube length, and tube offset length), and its shape is given by the solution of the Navier-Stokes equations. Because the equations governing this experiment’s fluid flow are highly non-linear, a computational fluid dynamics (CFD) package is currently being used to determine how this boundary layer changes with variations in experimental parameters. It is proposed to implement CFD results into the experimental design used to measure heterogeneous reaction rates. By doing so, the investigators will be able to tailor the experimental design to their liking by having a knowledge of the diffusion length as parameters are changed.Before soot reaction rates can be measured with the current setup, an important design parameter, particle separation distance on the TEM (transmission electron microscopy) grid, needs to be evaluated for its influence on the reaction rate. Diffusion of reacting gases is effected, and even becomes limited, by the close proximity of particles; hence, the reaction rates are altered. A kinetic-diffusive reaction code will be implemented to aid in the design of the particle spacing on the substrate. Tests will be conducted on particles for which reaction rate data exists, so as to confirm computational results and finalize the particle spacing. Measurements of reaction rates for soot and reacting gas will commence once this effect can be quantitatively described.
Once the experimental setup parameters are finalized, the investigators will perform experiments with aerosol particles and reacting gases. A chemical analysis will be performed on the products of the heterogeneous reactions using electron probe and micro-FTIR spectroscopy with the equipment available at PNNL. The proposed technique will be the first time this method is used to measure heterogeneous reactions.
Project Details
Project type
Exploratory Research
Start Date
2006-07-20
End Date
2007-01-05
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Cain JP, J Camacho, DJ Phares, H Wang, and A Laskin. 2011. "Evidence of Aliphatics in Nascent Soot Particles in Premixed Ethylene Flames." Proceedings of the Combustion Institute 33(1):533-540. doi:doi:10.1016/j.proci.2010.06.164
Cain JP, PL Gassman, H Wang, and A Laskin. 2010. "Micro-FTIR Study of Soot Chemical Composition – Evidence of Aliphatic Hydrocarbons on Nascent Soot Surfaces." Physical Chemistry Chemical Physics. PCCP 12(20):5206-5218. doi:10.1039/b924344e