19730012205.Pdf

NASA CONTRACTOR NASA CR-2178 REPORT CM »*|/>* £gT I1 IIf * »•F• COPY APPROXIMATE THERMOCHEMICAL TABLES FOR SOME C-H AND C-H-O SPECIES by Gilbert S. Bahn Prepared by LTV AEROSPACE CORPORATION Hampton, Va. 23365 for Langley Research Center NATIONAL AERONAUTICS AND SPACE ADMINISTRATION • WASHINGTON, D. C. • MARCH 1973 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. NASA CR-2178 4. Title and Subtitle 5. Report Date APPROXIMATE THERMOCHEMICAL TABLES FOR SOME C-H AND C-H-0 March 1973 6. Performing Organization Code SPECIES 34.800 \ 7. Author(s) 8. Performing Organization Report No. GILBERT S. BAHN 10. Work Unit No. 9. Performing Organization Name and Address 501. -24-1 6-01 -00 LTV Aerospace Corp. 11. Contract or Grant No. HAMPTON TECHNICAL CENTER NAS1- 10900 3121 ARMISTEAD AVENUE, HAMPTON, VA 23365 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Contractor Report National Aeronautics and Space Administration 14. Sponsoring Agency Code Washington, D.C. 20546 15. Supplementary Notes 16. Abstract Approximate thermochemical tables are presented for some C-H and C-H-0 species and for some ionized species, supplementing the JANAF Thermochemical Tables for application to finite-chemical-kinetics calculations. The approximate tables have been prepared by interpolation and extrapolation of limited available data, especially by interpolations over chemical families of species. Original estimations have been smoothed by use of a modification for the CDC-6600 computer of the Lewis Research Center PACT Program which was originally prepared for the IBM-7094 computer Summary graphs for various families show reasonably consistent curvefit values, anchored by properties of existing species in the JANAF tables. .17. Key Words (Suggested by.Auth6r(s))i# t . 18. Distribution Statement *•}•"•' "/-"•" enthalpy and entropy tables . curve fittings techniques • heats of formation Unclassified - Unlimited • hydrocarbons and free radicals • ionized species 19. Security dassif. (of this report) 20. Security Oassif. (of this page) 21. No. of Pages 22. Price* Unclassified Unclassified 247 $3.00 For sale by the National Technical I nformation Service, Springfield, Virginia 22151 p*9e Intentionally Left £,,,„„ APPROXIMATE THERMOCHEMICAL TABLES FOR SOME C-H and C-H-0 SPECIES By Gilbert S. Bahn LTV Aerospace Corporation Hampton, VA SUMMARY The Fortran IV Program for Calculation of Thermodynamic Data (named PAC1) prepared by B. J. McBride and S. Gordon for the IBM 7094 computer has been adapted in its curvefitting option to run on the CDC-6600 computer. The "grey" and "very grey" thermochemical tables for some C-H and C-H-0 species previously issued by the author as a technical paper, along with additional tables for some related chemical species, have been subjected to the refine- ment afforded by the curvefitting treatment. Comparisons within chemical families have been made, and substitute values have been assigned and then curvefitted as evidently required. Tables for available JANAF species have anchored such comparisons. This report includes tables and comparison graphs for 180 species, primarily selected for finite-chemical-kinetics calculations involving pyrolysis and/or combustion of aliphatic hydrocarbons, but also incorporating ionic species of possible interest in the hydrogen/air system at very high temperatures. INTRODUCTION Finite-chemical-kinetics calculations of pyrolysis and/or combustion of fuels or for ionization of air or combustion products require chemical thermodynamic data for the participating chemical species. In the past two decades, improvements made in both validity and scope of the chemical thermodynamic data in the scientific literature have been chiefly associated with chemical equilibrium considerations; the transient species of pyrolysis and combustion have generally been ignored during this time. The foremost English-language effort in the field is reported in the JANAF Thermochemical Tables (ref. 1), and even today the new tables issued for the JANAF compila- tion are justified by the needs of equilibrium calculations, not by finite- kinetics requirements. This report presents a set of tables designed to satisfy the latter need. In finite-kinetics calculations, the most critical application of the pertinent thermochemical data is in the determination of the equilibrium constant for each reaction of interest. The net rate of progress of any reaction depends upon its degree of displacement from its own equilibrium, even if all of the participants are nonequilibrium species. Secondly, adjustment of temperature in the reacting system is dependent upon the heat capacities of the participating species and upon the exothermicity or endo- thermicity of the various reactions consuming and producing quantities of these species. Finally, the balance of chemical thermodynamic data for a reaction may enter into the definition of the reaction rate constant when this is unknown experimentally and must be estimated analytically. These considerations explain the need for detailed chemical thermodynamic data such as are presented here. In order to pursue kinetic calculations of pyrolysis and/or -combustion in the recent past, the author has previously prepared provisional tables of chemical thermodynamic data for participating species. These tables were not well refined. Their preparation began with the tables from API Petroleum Project 44 (ref. 2), which were extrapolated as regards temperature for the particular species of interest that were present in the tables, and were interpolated as regards molecular composition for other species, especially free radicals. Another significant source of backgound numbers for the provisional tables was a report of Bauer and Duff (ref. 3), which made available results of their calculations for various species in the form of curvefit coefficients for the thermodynamic parameters as functions of temperature. Specific numbers were obtained by evaluating the coefficient expressions. Between averaging, extrapolating, interpolating, and estimating of similarities between different molecules, the present provisional tables owe debts to API Petroleum Project 44 and to Bauer and Duff. However, until now it has not been considered worthwhile to document these tables so that the basis of each table could be firmly established. Previously the preliminary or provisional versions of these tables were informally offered to the scientific community as "grey" (originally printed on grey paper) and "very grey" tables (in the terminology of Y. S. Touloukian) via reference 4. Availability of a computer program of McBride and Gordon, reported in reference 5, afforded an opportunity to refine the provisional tables. This computer program provides a least-squares curvefitting to temperature (T) of a set of chemical thermodynamic data, taking heat capacity (c ), enthalpy (H), and entropy"(S) jointly into account. The output data thus are internally consistent. In addition to ensuring this internal consistency, it was desired to improve the relationships between members of families of species, as is discussed in the body of the report. A few revisions of heats of formation that were effected were based simply on graphical comparisons. The McBride-Gordon computer program was prepared for the IBM 7094 computer, and changes were required to adapt it to the CDC-6600 computers installed at Langley Research Center. The adaptation is discussed, and then a delineation is made of the operations performed on the initial provisional data so as to obtain the output values which comprise the principle substance of this report. The work presented herein was done in support of the NASA Hypersonic Research Engine Project. The information presented was required, in part, for the HRE chemical kinetics studies where the engine internal flow temperatures were high enough to generate many free radicals and ionized species. Also, hydrocarbon information was required for combustion studies conducted with carboniferous vitiation in the tunnel air flow. It is unlikely that this work will be repeated in any general sense. For example, the API tables are sufficient for their intended ends, and the work of Bauer and Duff served its own purpose. Primarily, this report documents working tools utilized by the author in finite-chemical-kinetics calculations. Continued improvements will be desirable. SYMBOLS c heat capacity, cal/g-mole-°K P DCUBE a parameter used in estimation of reaction rate constants, not specifically dimensioned as assembled but roughly Angstroms cubed H enthalpy, kcal/g-mole S entropy, cal/g-mole-°K T temperature, °K COMPUTER PROGRAM CHANGES The "Fortran IV Program for Calculation of Thermodynamic Data "(ref. 5) bears the short title "PAC1" and will hereafter be referred to by this \ designation. The program has a multiplicity of options, and thus is of wide utility when an IBM 7094 computer is available for its application. How- ever, it is specific to the computer type for which it was prepared because five subroutines written in MAP language are included, and these are peculiar to the IBM 7094 compiler. Three of the MAP subroutines are required only for options which were not involved in the effort being discussed here. No work was devoted to adapting these options to the CDC-6600 computer; instead, the portions of the program involving these options were identified and eliminated. The other two subroutines required replacement with standard CDC-6600 subroutines, and this involved

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