The importance of thermodynamics to the modeling of nitrogen combustion chemistry
Modeling calculations have been performed to illustrate the effect of using five commonly accepted data bases of thermochemical properties on predictions of temporal species profiles. The thermochemical properties are those used for the determination of equilibrium constants employed in the calculation of reverse rate coefficients for a chemical mechanism where forward rate coefficients are specified. The modeling study was performed for hydrogen/oxygen/argon/nitrogen-compound mixtures where the nitrogen compound was either NO or NH/sub 3/. The mixtures reacted isothermally at 1600 K and isobarically at 1 atmosphere, and a single kinetic mechanism for which forward rate coefficients were specified was used throughout. Mixtures of equivalence ratios of 0. 625, 1.0 and 1.6 were considered. Modifications in sources of thermodynamic data have been substantial since 1971 for some species. Among the data bases, thermochemical properties varied greatly for the species NH, NH/sub 2/, NNH, and HO/sub 2/, and those for other species important in the mechanism had variations of less than 10 percent. The thermochemical property variations among the data bases in NH, NH/sub 2/ and NNH have substantial effects upon the temporal species profiles for nitrogenous species. While this result is not surprising, unfortunately, it is often overlooked when modeling results are compared. This effect is most pronounced for rich combustion, and varies directly with equivalence ratio. Use of different data bases had little effect on the H/O species profiles. Radical species profiles (with the exception of HO/sub 2/) tend to be influenced strongly by their own thermochemical properties. Computed profiles also were shown to be independent of algorithm (HCT or CHEMKIN) and thermodynamic property fitting procedure between 1000 and 2000/degree/K. 24 refs., 3 tabs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6908479
- Report Number(s):
- LBL-24687; CONF-880802-9; ON: DE88014656
- Resource Relation:
- Conference: 22. international symposium on combustion, Seattle, WA, USA, 14 Aug 1988; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMMONIA
COMBUSTION KINETICS
HYDROGEN
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXYGEN
CHEMICAL REACTIONS
ARGON
RADICALS
THERMOCHEMICAL PROCESSES
THERMODYNAMICS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
ELEMENTS
FLUIDS
GASES
HYDRIDES
HYDROGEN COMPOUNDS
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NITROGEN HYDRIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
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400800* - Combustion
Pyrolysis
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