Appendix A: Creating MDL Files for Finite Rate (PEC-related)

The PEC module couples together flamelet methods and finite rate chemistry. There is a tool in the Stream source code that can be used to generate .mdl files with finite rate reactions encoded within them.

The user needs to obtain a Chemkin formatted mechanism with appropriate thermodynamic and transport database files like the process used for FlameMaster mechanism generation. A Python script is in bin/flamelet/utilities/chemkin-converter/chemkin-converter.py. It can create a simple .mdl file from the Chemkin mechanism alone that only contains species information. To include the reaction information an additional step must be taken. A Cantera formatted reaction mechanism must be provided (the Cantera Chemkin parser is detailed and thorough) to the script which will format that input into an .mdl file for input to Stream. The utility requires the three input files to have the following names: chem.inp, tran.dat, and therm.dat.

python chemkin-converter.py -casename RP2 -mechanism RP2.cti

As an example, if you have Cantera installed, you can run the ck2yaml.py script to generate a Cantera mechanism from the Chemkin mechanism using the following command.

python ck2yaml.py --input=chem.inp --therm=therm.dat --transport=tran.dat
--output=cantera_rp2.yaml --permissive

Notes:

Sometimes the Cantera translator does not like extraneous information at the bottom of the transport file (that is sometimes included in some files). Remove those lines if there is trouble.

Appendix B: FlameMaster Diffusion Flamelet Control File

A FlameMaster control file for generating diffusion flamelets is replicated here for the reader to use as a template for their set of conditions.

### Newton Solver ####
TStart = 0.1e-4
TEnd = 10.0

DampFlag = TRUE
LambdaMin = 1.0e-2

UseNumericalJac is TRUE
UseModifiedNewton = TRUE

MaxIter = 350
TolRes = 1.0e-3
TolDy = 1.0e-4

#### Grid ####
DeltaNewGrid = 20
OneSoluOneGrid is TRUE
initialgridpoints = 81
maxgridpoints =359
Q = -0.25
R = 60

#OutputPath is ./upperBranch_rightMoving
OutputPath is./upperBranch_leftMoving
#OutputPath is ./lowerBranch_rightPoint
#OutputPath is ./lowerBranch_leftMoving

WriteRes is TRUE
WriteEverySolution is TRUE

StartProfilesFile is ./N-C12H26_p468_8chi800000tf0288to0111
#StartProfilesFile is ./N-C12H26_p468_8chi497.037tf0288to0111Tst0941
#StartProfilesFile is ./N-C12H26_p468_8chi00500tf0288to0111
#StartProfilesFile is ./lowerBranch_rightPoint/N-C12H26_p468_8chi5e+09tf0288to0111

MechanismFile is ndodecane_31spec.pre
globalReaction is N-C12H26 + 18.5O2 == 12CO2 + 13H2O;

fuel is N-C12H26
oxidizer is O2

#### Flame ####
ConstLewisNumber is TRUE
LewisNumberFile is LewisNumberOne
ArclengthCont = TRUE

Flame is Counterflow Diffusion in Mixture Fraction Space
EquationOfState is PengRobinson

Scalar DissipationRate =1e6 #Starting rate
#Scalar DissipationRate =1.1e6 #Upper branch - right moving value
Scalar DissipationRate =1e1 #Upper branch - left moving value
#Scalar DissipationRate =50e8 #Lower Branchure right point
#Scalar DissipationRate =1e3 #Extinction branch, left

# Additional Values to constrain the curve to have resolution near the turning point of the S-curve
#Scalar DissipationRate = 1.000000e06

# Note: If the pressure continuation to shift the conditions is not quite
# exactly the pressure you want, then on the next property shift, just adjust
# this initial pressure to be the pressure that you want, and it should update
# the pressure and whatever the other property you selected.
pressure = 46.884e6

#### Boundary Conditions ####
Fuel Side {
    dirichlet {
    t=288.889
    Y->N-C12H26 = 1.0
    }
}

Oxidizer Side {
    dirichlet {
    t=111.111
    Y->O2 = 1.00
    }
}

Appendix C: FlameMaster Premixed Flamelet Control File

A FlameMaster control file for generating premixed flamelets is replicated here for the reader to use as a template for their set of conditions.

#### Newton solver ####
UseNumericalJac is TRUE
UseSecondOrdJac is TRUE
UseModifiedNewton = TRUE

DampFlag = TRUE
LambdaMin = 1.0e-3

MaxIter = 2000
TolRes = 1.0e-16
TolDy = 1e-12

#### grid ####
DeltaNewGrid = 50
OneSolutionOneGrid = TRUE
initialgridpoints = 80
maxgridpoints = 360
q = -0.25
R = 60

#### Sensitivity Analysis ####
#ReactionFluxAnal is TRUE

#### I/O ####
WriteEverySolution = TRUE

#PrintMolarFractions is TRUE
OutputPath is ./output

#StartProfilesFile is ./CH4_p01_0phi1_0006tu0300
StartProfilesFile is ./output/CH4_p01_0phi1_0000tu0300

#### Chemistry ####
MechanismFile is drm19.pre
globalReaction is CH4 + 2O2 == CO2 + 2H2O;

EquationOfState is IdealGasLaw

fuel is CH4
oxidizer is O2

#### Flame ####
ConstLewisNumber is TRUE
LewisNumberFile is LewisNumberOne

Flame is UnstretchedPremixed
ExactBackward is TRUE

phi = 0.95
phi = 0.9
phi = 0.85
phi = 0.8
phi = 0.75

pressure = 101325

#### Boundary conditions ####
#ConstMassFlux is TRUE
#MassFlux = 0.3

Unburnt Side {
    dirichlet {
        t = 300
        Y->CH4 = 0.0552
        Y->O2 = 0.2201
        Y->N2 = 0.7247
    }
}

Appendix D: Species Renaming

Occasionally there will be a case where the species names that FlameMaster uses (and the names that are written to the flamelet table) conflict with Stream’s table processor (bad characters, etc.). A Python utility has been written that will take an input file containing a mapping of old names to new names and rename the species in a provided ascii flamelet table.

Command:

bin/flamelet/utilities/flamemaster-tools/loci_table_species_rename.py Table.dat rename.dat

Appendix E: Pruning FlameMaster Counterflow-Diffusion Flamelets

In the course of generating a suite of counterflow-diffusion flamelets using FlameMaster, it is possible to generate a large number of flamelets due to FlameMaster’s use of an automatic arclength-continuation method. A resolution of 5 to 10 flamelets per decade of the scalar dissipation rate is usually sufficient. A collection of many flamelet solutions also runs a possible risk of having an overlapping flamelet solution. When this happens, the uniqueness of the Z-C manifold that is used to interpolate becomes polluted and the tabulated values can become erroneous. To remedy this issue, a Python utility script is provided in the utilities/flamemaster_tools directory of the Flamelet Table Tool. The script is named flamemaster_flamelet_pruning.py.

A summary of the options that the script takes is provided below:

FlameMaster Pruning Script Arguments

Argument	Type	Description
–flamelets_path	str (required)	Absolute or relative path to directory with flamelets
–minimum_arclength	float (required)	Threshold that removed flamelets that are closer than this distance together
–output_dir_name	str (required)	Name of directory to output pruned flamelets to