University of Utah Undergraduate Research Abstracts, Volume 3, Spring 2003

Sensitivity Tests on the Uncertainties of Thermodynamic Properties on Nitrogen Oxides Emissions from Combustion Sources

SENSITIVITY TESTS ON THE UNCERTAINTIES OF THERMODYNAMIC PROPERTIES ON NITROGEN OXIDES EMISSIONS FROM COMBUSTION SOURCES Satisfying ever tightening restrictions on emissions of nitrogen oxides, combustion-generated air pollutants, requires a better understanding of the fundamentals of nitrogen chemistry in flames. In order to gain insight into elementary reaction steps, flame simulations with detailed chemical kinetic mechanisms are often employed. None of the available mechanisms are currently able to simulate nitrogen oxide emissions in modern intermediate-temperature combustors accurately. Although the most common target for mechanism improvement has been reaction rate coefficients, we found that some of the underlying thermo-dynamic data was questionable. The uncertainties in thermody-namic data affect the simulation results through equilibrium con- stants and reactive mixture heat transfer properties. Thermodynamic properties can be obtained theoretically through accurate but expensive ab initio molecular orbital calculations; however, it would be a significant undertaking to compute properties for all species involved. The objective of this study, therefore, was to identify the species whose ther-modynamic properties have the greatest impact on calculated emissions of nitrogen oxides and thus might need to be reevaluated. For that purpose, the simulation program Chemkin™ II was modified to calculate the thermodynamic sensitivity coefficients, whose magnitude indicates the influence of a given species. To the best of our knowledge this is the first study of this kind. David Q. Vu Junior Chemical Engineering dvul [e-mail] Faculty Sponsor: Zoran M. Djursic Dept. of Chemical Engineering [e-mail] Faculty Sponsor: Eric G. Eddings Dept. of Chemical Engineering [e-mail] 75