Process Modeling and Kinetics

Research Focus: We develop, analyze, and improve detailed gas phase and gas-surface chemical kinetics mechanisms for complex physical processes. Modeling with reliable mechanisms is the key to understanding, controlling, and enhancing such reaction systems. Our approach begins by assembling and evaluating a detailed elementary reaction step mechanism, using our expertise in rate theory and experiments where necessary. A second step is to compare model results for selected process experiments, including some in our laboratories, to validate the mechanism's performance. Often an optimization procedure is needed to enhance performance, because kinetics uncertainties propagate into process model prediction error.

This process and its application to natural gas combustion are described on the GRI-Mech Web page. We select relevant, modelable process 'target' data from the literature, use sensitivity analysis to identify the controlling reaction rate parameters, map the response of the target predictions to these rates, and construct and minimize an error function for these combined predictions vs. rate parameter variations.

Accomplishments: In collaboration with colleagues at Stanford, UC Berkeley, and Texas, we produced the widely used GRI-Mech optimized combustion chemistry mechanism for natural gas oxidation and NO production and reburn. We recently used sensitivity analysis and kinetics evaluation on atmospheric chemistry models to determine uncertainties and their sources in model ozone predictions.

Previous efforts have investigated a wide range of other subjects such as smog photochemistry, coal combustion, treatment methods for NO, thermal chlorination, hydrocracking, catalytic combustion, spacecraft reentry kinetics and ablation, diamond CVD and plasma arc-jet synthesis, discharge laser kinetics, and fuel additive effects. We recently began a collaborative effort with CFDRC to develop kinetics mechanisms for semiconductor processes for use in Virtual Reactor simulators.

Application Opportunities: Our varied and general experience in kinetics and modeling for many gas phase systems, coupled with our strong background in rate constant evaluation estimation and measurement, ensures our ability to develop mechanisms and models for virtually any process with a significant gas phase kinetics component. Our technologies also feature the ability to reduce mechanism size for rapid model execution, and to systematically optimize mechanisms (within the kinetics error bars) to provide reliable predictability.

Learn more about our Modeling Complex Chemical Systems.

Papers:

• P. A. Berg, G. P. Smith, J. B. Jeffries, and D. R. Crosley, "Nitric Oxide Formation and Reburn in Low-Pressure Methane Flames," 27th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, p. 1377, 1998.

• M. K. Dubey, G. P. Smith, W. S. Hartley, D. E. Kinnison, and P. S. Connell, "Rate Parameter Uncertainty Effects in Assessing Stratospheric Ozone Depletion by Supersonic Aircraft," Geophys. Res. Lett. 24, 2737 (1997).

• J. B. Jeffries, G. P. Smith, D. E. Heard, and D. R. Crosley, "Comparing Laser-Induced Fluorescence Measurements and Computer Models of Low Pressure Flame Chemistry," Ber. Bunsenges. Phys. Chem. 96, 1410 (1992).

• G. P. Smith and J. B. Jeffries, "Gas Phase Chemistry in a Diamond-Depositing dc-Arc-Jet," in Diamond Materials, Electrochem. Soc. Proc. Vol. 91-8, p. 194, 1991.

• G. P. Smith and D. R. Crosley, "A Photochemical Model of Ozone Interference Effects in Laser Detection of Tropospheric OH," J. Geophy. Res. 95, 16427 (1990).

• D. M. Golden, G. P. Smith, A. B. McEwen, C.-L. Yu, B. Eiteneer, M. Frenklach, G. L. Vaghjiani, A. R. Ravishankara, and F. P. Tully, "OH(OD) + CO: Measurements and an Optimized RRKM Fit,' J. Phys. Chem. 102, 8598(1998).

• M. K. Dubey, M. P. McGrath, G. P. Smith, and F. S. Rowland, "HCl Yield from OH+ClO: Stratospheric Model Sensitivities and Elementary Rate Theory Calculations," J. Phys. Chem. 102, 3127 (1998).

Visit the Laboratory - Molecular Physics Laboratory

Technical Contact:
Gregory P. Smith
(650) 859-3496
gregory.smith@sri.com