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Kinetics and Reaction Engineering
We study intrinsic surface and gas phase reaction and transport mechanisms and
their interactions in high temperature chemically-reacting flow systems in order
to optimize or stabilize the performance of reactors and combustors. Challenges
related to species and particulate measurements in these complex systems have
led us to develop novel measurement techniques to produce new insights. Our
experimental tools are laboratory-scale reactors and flames equipped with
laser-based spectroscopic techniques, infrared spectroscopy, gas chromatography,
and mass spectrometry. Our theoretical tools range from asymptotic to large
scale reacting flow models and kinetic parameter estimation techniques.
Catalytically Stabilized Combustion of Hydrocarbon Fuels
Catalytic combustion allows engine designs with both efficiency improvements and
significant reduction of both NOx, CO, and hydrocarbon emissions. In some
designs the majority of the reaction occurs on the catalyst surface but in many
interesting applications gas phase reactions are ignited and stabilized by heat
and intermediates from a surface which is kept hot by catalytic oxidation of the
fuel. These designs are also interesting for synthesis reactors as well as for
power production. We are combining modeling work on catalytically stabilized
combustion with experimental gas phase species and temperature measurements
using laser-induced fluorescence (LIF), photoionization mass spectrometry to
provide information on the interaction between homogeneous and heterogeneous
processes in these systems. We are also developing techniques based on UV-vis
reflectance spectroscopy to monitor in-situ changes in catalyst morphology and
state under combustion conditions. Qualitative analysis of how to add catalytic
boundary conditions to turbulent reacting flow models has also been addressed
for cases of both high and low Damkohler number.
Hydrocarbon Chemistry in Flames
The difficulties involved with accurate, non-perturbing measurement of dilute
concentrations of large hydrocarbons in complex reacting flow mixtures have
obscured mechanistic studies of many combustion processes, especially those
related to higher hydrocarbon growth. A major challenge in addressing these
problems is dealing with the large number of cross-correlated unknowns. This
dictates the development of experimental tools to address a meaningful portion
of the problem, development of techniques for simultaneous measurement of as
many parameters as possible and use of theoretical tools for providing system
constraints and error analysis. Using a novel measurement technique--single
photon ionization time of flight mass spectrometry (VUV-MS)-- we have been able
to do molecular beam sampling in complex mixtures, for example, we can
simultaneously gather accurate, real-time measurements of a wide range of
hydrocarbons and hydrocarbon radicals from diffusion flames and combustion and
pyrolysis reactors.
- Selected Publications:
"Uniform-Diameter
Single-Walled Carbon Nanotubes Catalytically Grown in Cobalt-Incorporated
MCM-41," D. Ciuparu, Y. Chen, S. Lim, G.L. Haller, and L.D. Pfefferle, J
Phys Chem B, 108(2) 503 (2004).
"In Situ DR-FTIR Investigation of Surface Hydroxyls on Gamma-Al2O3
Supported PdO Catalysts During Methane Combustion," D. Ciuparu, E.
Perkins and L.D. Pfefferle, Appl Catal a-Gen, 2003.
"Synthesis and Characterization of Highly Ordered Co-MCM-41 for
Production of Aligned Single Walled Carbon Nanotubes (SWNT)," S. Lim,
D. Ciuparu, C. Pak, F. Dobek, Y. Chen, D. Harding, L.D. Pfefferle, and G.
Haller, J Phys Chem B, 107(40), 11048 (2003).
"Experimental Study of Fuel Decomposition and Hydrocarbon Growth
Processes for Practical Fuel Components: Heptanes," C.S. McEnally, D.M.
Ciuparu, and L.D. Pfefferle, Combust Flame, 134(4), 339 (2003).
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