The input file to the Gas-phase Kinetics Pre-processor for a hydrogen-oxidation process is shown in Example 1.1: Sample Reaction Mechanism as Read by the Gas-phase Kinetics Pre-processor . First, the file specifies the elements and species that appear in the mechanism, and then includes the reaction mechanism description. The input is essentially format free. The elements and species names need only be separated by blank spaces, but may also be separated by tabs or blank lines. In the REACTIONS section, the character string that describes the reaction appears on the left and is followed by the three Arrhenius coefficients (pre-exponential factor, temperature exponent, and activation energy). Enhanced third body efficiencies for selected species are specified in the line following that for several reactions that contain an arbitrary third body, M. Exclamation marks signify the beginning of comments and the remainder of the line is ignored.

ELEMENTS  H O N END
SPECIES   H2 H O2 O OH HO2 H2O2 H2O N N2 NO END
REACTIONS
   H2+O2=2OH                  0.170E+14   0.00     47780
   OH+H2=H20+H                0.117E+10   1.30      3626   !D-L&W
   O+OH=O2+H                  0.400E+15  -0.50         0   !JAM 1986
   O+H2=OH+H                  0.506E+05   2.67      6290   !KLEMM ET AL., 1986
   H+O2+M=HO2+M               0.361E+18  -0.72         0   !DIXON-LEWIS
      H2O/18.6/ H2/2.86/ N2/1.26/
   OH+HO2=H2O+O2              0.750E+13   0.00         0   !D-L
   H+HO2=2OH                  0.140E+15   0.00      1073   !D-L
   O+HO2=O2+OH                0.140E+14   0.00      1073   !D-L
   2OH=O+H2O                  0.600E+09   1.30         0   !COHEN-WEST
   H+H+M=H2+M                 0.100E+19  -1.00         0   !D-L
      H2O/0.0/ H2/0.0/
   H+H+H2=H2+H2               0.920E+17  -0.60         0
   H+H+H2O=H2+H2O             0.600E+20  -1.25         0
   H+OH+M=H2O+M               0.160E+23  -2.00         0   !D-L
      H2O/5/
   H+O+M=OH+M                 0.620E+17  -0.60         0   !D-L
      H2O/5/
   O+O+M=O2+M                 0.189E+14   0.00     -1788   !NBS
   H+HO2=H2+O2                0.125E+14   0.00         0   !D-L
   HO2+HO2=H2O2+O2            0.200E+13   0.00         0
   H2O2+M=OH+OH+M             0.130E+18   0.00     45500
   H2O2+H=HO2+H2              0.160E+13   0.00      3800
   H2O2+OH=H2O+HO2            0.100E+14   0.00      1800
   O+N2=NO+N                  0.140E+15   0.00     75800
   N+O2=NO+O                  0.640E+10   1.00      6280
   OH+N=NO+H                  0.400E+14   0.00         0
END

Assume the governing equation we wish to study is the energy conservation equation for a constant-pressure environment:

(1–1)

where is the temperature, the mass density, the mean specific heat, the molar species enthalpies, and the species molar production rates. The representation of this equation begins with Gas-phase Kinetics subroutine calls (the output variables are underlined to help distinguish them):

CALL CKINIT(LENIWK, LENRWK, LENCWK, LINKCK, LOUT, ICKWRK, RCKWRK, CCKWRK, IFLAG)
CALL CKINDX(ICKWRK, RCKWRK, MM, KK, II, NFIT)
CALL CKRHOY(P, T, Y, ICKWRK, RCKWRK, RHO)
CALL CKCPBS(T, Y, ICKWRK, RCKWRK, CPB)
CALL CKHML (T, ICKWRK, RCKWRK, HML)
CALL CKWYP (P, T, Y, ICKWRK, RCKWRK, WDOT)

The complete details for these calls are explained in later sections of this manual; the objective here is to illustrate the relative simplicity of writing an Ansys Chemkin application. Briefly, the first call is to the initialization subroutine CKINIT, which reads the Linking File created by the Pre-processor and fills the three work arrays. LENIWK, LENRWK and LENCWK are dimensions provided by the user for the data arrays ICKWRK, RCKWRK, and CCKWRK. IFLAG is an error flag that is returned with a zero value if no errors occur. LINKCK is the logical file unit number of the Linking File, chem.asc, and LOUT is the logical file number for printed diagnostic and error messages. The call to CKINDX provides index information about the reaction mechanism: MM is the number of elements contained in the species, KK is the number of gas-phase species, II is the number of reactions, and NFIT is the number of coefficients in the thermodynamic fits. In the remaining calls, P, T, and Y are the pressure, temperature, and vector of species mass fractions, respectively. The output variables correspond to the various terms for describing the equation, that is, , , , and .

The FORTRAN representation of the governing equation, given by combining the results of the above subroutine calls, is simply

    SUM=0.0
    DO 100 K=1,KK
       SUM = SUM + HML(K)*WDOT(K)
100 CONTINUE
    DTDT = -SUM/(RHO*CPB)

One can see from this example that relatively little programming effort is required to form a conservation equation for an arbitrary reaction mechanism.