Defining chemical reactions
The following inputs are defined using the prefix chemistry:
Description |
Type |
Default |
|
|---|---|---|---|
solve |
Specify the name(s) of the chemical reactions or set to None to disable the chemistry solver. The name(s) assigned to the chemistry solver are used to specify the chemical reactions equations. |
String |
|
[reaction0].reaction |
Chemical formula for the given reaction. The string given as input must not contain white space and the reaction direction has to be specified as ‘-->’ or ‘<--’. Chemical species phases must be defined as ‘(g)’ for the fluid phase or ‘(s)’ for the solid phase. |
String |
|
mass_balance_tolerance |
Tolerance used to test chemical formula conserves mass. \(\left|\sum\text{products - \sum\text{reactants}\right| < \text{tolerance}\) |
Real |
1e-12 |
solids.update_type |
How to update solids quantities due to chemical reactions. Options:
|
ConstantVolume |
|
solids.mass_threshold |
Sets a threshold value for the particles’ mass. When updating the solids quantities in chemistry, check whether the solids mass is below the threshold, and in that case set the particle as invalid and remove it. |
Real |
0 |
solids.radius_threshold |
Sets a threshold value for the particles’ radius. When updating the solids quantities in chemistry, check whether the solids radius is below the threshold, and in that case set the particle as invalid and remove it. |
Real |
0 |
solids.density_threshold |
Sets a threshold value for the particles’ density. When updating the solids quantities in chemistry, check whether the solids density is below the threshold, and in that case set the particle as invalid and remove it. |
Real |
0 |
Choosing the integrator type for the chemistry ODE integration operation that is
performed to determine the fluid and solids phases transfer quantities due to
chemical reactions. The StiffSolver class of integrators is inspired by the
class of integrators in AMReX-Astro/Microphysics
(https://github.com/AMReX-Astro/Microphysics)
Description |
Type |
Default |
|
|---|---|---|---|
chemistry.integrator |
Specified name of the chemistry ODE integrator type. Options (case-insensitive):
|
String |
ForwardEuler |
One can define the environment variable VODE_JACOBIAN_CACHING at compile
time to enable caching of the numerical approximation of the Jacobian matrix
(the derivative of the ODE right-hand side), applicable when the VODE integrator
is selected. The following inputs can be specified using the
prefix chemistry.integrator:
Description |
Type |
Default |
|
|---|---|---|---|
burner_verbose |
Enable printing of some integration statistics. |
Int |
0 |
ode_max_steps |
The maximum number of substeps for the ODE integration. |
Int |
150000 |
jacobian_type |
Select how to compute the Jacobian for the ODE iterative solver.
This option is available for Options (case-insensitive):
|
String |
Numerical |
atol |
Absolute tolerance for the ODE integration error test between the solution and the fine-step solution. |
Real |
1.e-6 |
rtol |
Relative tolerance for the ODE integration error test between the solution and the fine-step solution. |
Real |
1.e-6 |
retry_atol |
Overwrites the absolute tolerance value atol in case the ODE integration fails. |
Real |
-1 |
retry_rtol |
Overwrites the relative tolerance value rtol in case the ODE integration fails. |
Real |
-1 |
retry_swap_jacobian |
Swaps the type of Jacobian (from 1 to 0 or vice versa) in case the ODE integration fails. |
Int |
1 |
ode_max_dt |
Maximum timestep size for the ODE integration substeps. |
Real |
1.e30 |
max_dt_change_factor |
Only for StiffSolver::ForwardEuler, sets a maximum factor for the change of the timestep for the internal substeps. |
Real |
1.001 |
max_iter |
Maximum number of iterations for the internal Newton solver. |
Int |
100 |
linalg_do_pivoting |
Only for |
Int |
1 |
rp_rtol |
Relative tolerance for the convergence test of the internal
Newton solver. Valid only for |
Real |
1.e-6 |
use_jacobian_caching |
Only for |
Int |
1 |
X_reject_buffer |
Only for |
Real |
1.0 |
Below is an example for specifying chemical reactions for MFIX-Exa.
Example inputs
The following setup shows how to define chemical reactions in the inputs file.
Only Ideal Gas constraint types can be used when solving chemistry, as the
IncompressibleFluid constraint would be inconsistent with the nature of
a problem where the fluid density is not constant because of mass transfer due
to chemical reactions.
mfix.constraint_type = IdealGasOpenSystem
mfix.advect_density = 1
mfix.advect_enthalpy = 1
mfix.solve_species = 1
# Species model settings
#----------------------------------------------------------------------
species.solve = CH4 H2 CO H2O CO2 O2 N2 Fe2O3 FeO inert
species.diffusivity = constant
species.diffusivity.constant = 2.31000e-5 # m^2 / sec
species.specific_heat = NASA7-poly
# Methane
species.CH4.molecular_weight = 16.04276e-3
species.CH4.specific_heat.NASA7.a0 = 5.14911468E+00 1.65326226E+00
species.CH4.specific_heat.NASA7.a1 = -1.36622009E-02 1.00263099E-02
species.CH4.specific_heat.NASA7.a2 = 4.91453921E-05 -3.31661238E-06
species.CH4.specific_heat.NASA7.a3 = -4.84246767E-08 5.36483138E-10
species.CH4.specific_heat.NASA7.a4 = 1.66603441E-11 -3.14696758E-14
species.CH4.specific_heat.NASA7.a5 = -1.02465983E+04 -1.00095936E+04
# Hydrogen
species.H2.molecular_weight = 2.01588e-3
species.H2.specific_heat.NASA7.a0 = 2.34433112E+00 2.93286575E+00
species.H2.specific_heat.NASA7.a1 = 7.98052075E-03 8.26608026E-04
species.H2.specific_heat.NASA7.a2 = -1.94781510E-05 -1.46402364E-07
species.H2.specific_heat.NASA7.a3 = 2.01572094E-08 1.54100414E-11
species.H2.specific_heat.NASA7.a4 = -7.37611761E-12 -6.88804800E-16
species.H2.specific_heat.NASA7.a5 = -9.17935173E+02 -8.13065581E+02
# Carbon monoxide
species.CO.molecular_weight = 28.01040e-3
species.CO.specific_heat.NASA7.a0 = 3.57953350E+00 3.04848590E+00
species.CO.specific_heat.NASA7.a1 = -6.10353690E-04 1.35172810E-03
species.CO.specific_heat.NASA7.a2 = 1.01681430E-06 -4.85794050E-07
species.CO.specific_heat.NASA7.a3 = 9.07005860E-10 7.88536440E-11
species.CO.specific_heat.NASA7.a4 = -9.04424490E-13 -4.69807460E-15
species.CO.specific_heat.NASA7.a5 = -1.43440860E+04 -1.42661170E+04
# Water vapor
species.H2O.molecular_weight = 18.01528e-3
species.H2O.specific_heat.NASA7.a0 = 0.41986352E+01 0.26770389E+01
species.H2O.specific_heat.NASA7.a1 = -0.20364017E-02 0.29731816E-02
species.H2O.specific_heat.NASA7.a2 = 0.65203416E-05 -0.77376889E-06
species.H2O.specific_heat.NASA7.a3 = -0.54879269E-08 0.94433514E-10
species.H2O.specific_heat.NASA7.a4 = 0.17719680E-11 -0.42689991E-14
species.H2O.specific_heat.NASA7.a5 = -0.30293726E+05 -0.29885894E+05
# Carbon dioxide
species.CO2.molecular_weight = 44.00980e-3
species.CO2.specific_heat.NASA7.a0 = 2.35681300E+00 4.63651110E+00
species.CO2.specific_heat.NASA7.a1 = 8.98412990E-03 2.74145690E-03
species.CO2.specific_heat.NASA7.a2 = -7.12206320E-06 -9.95897590E-07
species.CO2.specific_heat.NASA7.a3 = 2.45730080E-09 1.60386660E-10
species.CO2.specific_heat.NASA7.a4 = -1.42885480E-13 -9.16198570E-15
species.CO2.specific_heat.NASA7.a5 = -4.83719710E+04 -4.90249040E+04
# Oxygen
species.O2.molecular_weight = 31.99880e-3
species.O2.specific_heat.NASA7.a0 = 3.78245636E+00 3.66096065E+00
species.O2.specific_heat.NASA7.a1 = -2.99673416E-03 6.56365811E-04
species.O2.specific_heat.NASA7.a2 = 9.84730201E-06 -1.41149627E-07
species.O2.specific_heat.NASA7.a3 = -9.68129509E-09 2.05797935E-11
species.O2.specific_heat.NASA7.a4 = 3.24372837E-12 -1.29913436E-15
species.O2.specific_heat.NASA7.a5 = -1.06394356E+03 -1.21597718E+03
# Nitrogen
species.N2.molecular_weight = 28.01340e-3
species.N2.specific_heat.NASA7.a0 = 3.53100528E+00 2.95257637E+00
species.N2.specific_heat.NASA7.a1 = -1.23660988E-04 1.39690040E-03
species.N2.specific_heat.NASA7.a2 = -5.02999433E-07 -4.92631603E-07
species.N2.specific_heat.NASA7.a3 = 2.43530612E-09 7.86010195E-11
species.N2.specific_heat.NASA7.a4 = -1.40881235E-12 -4.60755204E-15
species.N2.specific_heat.NASA7.a5 = -1.04697628E+03 -9.23948688E+02
# Hematite
species.Fe2O3.molecular_weight = 159.68820e-3
species.Fe2O3.specific_heat.NASA7.a0 = 1.52218166E-01 2.09445369E+01
species.Fe2O3.specific_heat.NASA7.a1 = 6.70757040E-02 0.00000000E+00
species.Fe2O3.specific_heat.NASA7.a2 = -1.12860954E-04 0.00000000E+00
species.Fe2O3.specific_heat.NASA7.a3 = 9.93356662E-08 0.00000000E+00
species.Fe2O3.specific_heat.NASA7.a4 = -3.27580975E-11 0.00000000E+00
species.Fe2O3.specific_heat.NASA7.a5 = -1.01344092E+05 -1.07936580E+05
# Wustite
species.FeO.molecular_weight = 71.84440e-3
species.FeO.specific_heat.NASA7.a0 = 3.68765953E+00 1.81588527E+00
species.FeO.specific_heat.NASA7.a1 = 1.09133433E-02 1.70742829E-02
species.FeO.specific_heat.NASA7.a2 = -1.61179493E-05 -2.39919190E-05
species.FeO.specific_heat.NASA7.a3 = 1.06449256E-08 1.53690046E-08
species.FeO.specific_heat.NASA7.a4 = -2.39514915E-12 -3.53442390E-12
species.FeO.specific_heat.NASA7.a5 = -3.34867527E+04 -3.30239565E+04
# inert
species.inert.molecular_weight = 92.82399e-3
species.inert.specific_heat.NASA7.a0 = 1.52218166E-01 2.09445369E+01
species.inert.specific_heat.NASA7.a1 = 6.70757040E-02 0.00000000E+00
species.inert.specific_heat.NASA7.a2 = -1.12860954E-04 0.00000000E+00
species.inert.specific_heat.NASA7.a3 = 9.93356662E-08 0.00000000E+00
species.inert.specific_heat.NASA7.a4 = -3.27580975E-11 0.00000000E+00
species.inert.specific_heat.NASA7.a5 = -1.01344092E+05 -1.07936580E+05
# Fluid model settings
#----------------------------------------------------------------------
fluid.solve = fluid
fluid.thermodynamic_pressure = 101325.
fluid.reference_temperature = 298.15
fluid.species = CH4 H2 CO H2O CO2 O2 N2
fluid.viscosity = constant
fluid.viscosity.constant = 4.73e-5 #air @ 1200K
fluid.specific_heat = mixture
fluid.thermal_conductivity = constant
fluid.thermal_conductivity.constant = 0.024
# Solids model settings
#----------------------------------------------------------------------
solids.types = solid0
solids.reference_temperature = 298.15
solids.species = Fe2O3 FeO inert
solids.specific_heat = mixture
# Chemistry model settings
#----------------------------------------------------------------------
chemistry.solve = Hem_CH4 Hem_H2 Hem_CO Wus_O2
chemistry.Hem_CH4.reaction = Fe2O3(s)+0.25CH4(g)-->2.FeO(s)+0.25CO2(g)+0.5H2O(g)
chemistry.Hem_H2.reaction = Fe2O3(s)+H2(g)-->2.FeO(s)+H2O(g)
chemistry.Hem_CO.reaction = Fe2O3(s)+CO(g)-->2.FeO(s)+CO2(g)
chemistry.Wus_O2.reaction = FeO(s)+0.25O2(g)-->0.5Fe2O3(s)
# Initial Conditions
#----------------------------------------------------------------------
ic.regions = full-domain
ic.full-domain.fluid.volfrac = 0.725
ic.full-domain.fluid.velocity = 0.015 0.00 0.00
ic.full-domain.fluid.temperature = 1273.
ic.full-domain.fluid.species.CH4 = 0.1
ic.full-domain.fluid.species.H2 = 0.2
ic.full-domain.fluid.species.CO = 0.1
ic.full-domain.fluid.species.H2O = 0.2
ic.full-domain.fluid.species.CO2 = 0.1
ic.full-domain.fluid.species.O2 = 0.1
ic.full-domain.fluid.species.N2 = 0.2
ic.full-domain.solids = solid0
ic.full-domain.packing = pseudo_random
ic.full-domain.solid0.volfrac = 0.275
ic.full-domain.solid0.velocity = 0.00 0.00 0.00
ic.full-domain.solid0.diameter = constant
ic.full-domain.solid0.density = constant
ic.full-domain.solid0.diameter.constant = 100.0e-6
ic.full-domain.solid0.density.constant = 2000.0
ic.full-domain.solid0.temperature = 1273.
ic.full-domain.solid0.species.Fe2O3 = 0.3
ic.full-domain.solid0.species.FeO = 0.3
ic.full-domain.solid0.species.inert = 0.4
# Boundary Conditions
#----------------------------------------------------------------------
bc.regions = inflow outflow
bc.inflow = mi
bc.inflow.fluid.volfrac = 1.0
bc.inflow.fluid.velocity = 0.015 0.0 0.0
bc.inflow.fluid.temperature = 1273.
bc.inflow.fluid.species.CH4 = 0.1
bc.inflow.fluid.species.H2 = 0.2
bc.inflow.fluid.species.CO = 0.1
bc.inflow.fluid.species.H2O = 0.2
bc.inflow.fluid.species.CO2 = 0.1
bc.inflow.fluid.species.O2 = 0.1
bc.inflow.fluid.species.N2 = 0.2
bc.outflow = po
bc.outflow.fluid.pressure = 101325.