6cb4bd93ce
4 spaces per indentation level, no tabs, no trailing whitespace, and a single newline at end of each file.
97 lines
3.5 KiB
Python
97 lines
3.5 KiB
Python
########################################################################
|
|
#### NOTE: with the changes made to the ChemEquil solver in version 1.7,
|
|
#### it now converges, and the Multiphase solver is no longer invoked
|
|
#### in this demo
|
|
########################################################################
|
|
|
|
# Equilibrium of a (nearly) stoichiometric hydrogen/oxygen mixture at
|
|
# fixed temperature.
|
|
|
|
# Cantera has 3 different equilibrium solvers. The 'ChemEquil' solver
|
|
# uses the element potential method for homogeneous equilibrium in gas
|
|
# mixtures. It is fast, but sometimes doesn't converge. The
|
|
# 'MultiPhaseEquil' solver uses the VCS algorithm (Gibbs
|
|
# minimization), which is slower but more robust. As the name
|
|
# suggests, it can also handle multiple phases. Here we'll solve a
|
|
# problem for which the ChemEquil solver fails, but the
|
|
# MultiPhaseEquil solver has no problem.
|
|
|
|
from Cantera import *
|
|
|
|
# create an object representing the gas phase
|
|
gas = importPhase("h2o2.cti")
|
|
|
|
temp = 400.0
|
|
|
|
# make the composition very close to stoichiometric
|
|
comp = "H2:1.00000001, O2:0.5"
|
|
|
|
# set the initial state
|
|
gas.set(T = temp, P = OneAtm, X = comp)
|
|
|
|
# equilibrate the gas holding T and P fixed. First try the default
|
|
# (ChemEquil) solver... (This will fail, throwing an exception that
|
|
# will be caught in the 'except' block, where we will try the other
|
|
# solver.)
|
|
|
|
####################################################################
|
|
# Note: We are setting solver = 0 here to demonstrate the difference
|
|
# between the two solvers. If you do not set 'solver', or set it to a
|
|
# negative value, then ChemEquil will be tried first, and if it fails
|
|
# the MultiPhaseEquil solver will be tried. In most cases this will
|
|
# give the best results.
|
|
####################################################################
|
|
|
|
try:
|
|
gas.equilibrate("TP", solver = 0) # use the ChemEquil (0) solver
|
|
except:
|
|
print "ChemEquil solver failed! Try the MultiPhaseEquil solver..."
|
|
|
|
# Try again. Reset the gas to the initial state
|
|
gas.set(T = temp, P = OneAtm, X = comp)
|
|
|
|
# The MultiPhaseEquil solver is used to equilibrate 'Mixture'
|
|
# objects, since these may have more than one phase. Here we'll
|
|
# create a Mixture object containing only the gas. Some other
|
|
# useful parameters are rtol (relative error tolerance, default =
|
|
# 1.0e-9), max_steps (default = 1000), loglevel (default = 0).
|
|
mix = Mixture([(gas,1.0)])
|
|
mix.equilibrate("TP", loglevel=4)
|
|
|
|
# Note: another way to do this is:
|
|
# gas.equilibrate("TP", solver = 1, loglevel = 4)
|
|
|
|
# print a summary of the results
|
|
print gas
|
|
|
|
|
|
|
|
# To check that this is an equilibrium state, verify that the chemical
|
|
# potentials may be computed by summing the element potentials for each atom.
|
|
# (The element potentials are the chemical potentials of the atomic vapors.)
|
|
|
|
mu_H2, mu_OH, mu_H2O, mu_O2, lambda_H, lambda_O = gas.chemPotentials(
|
|
["H2", "OH", "H2O", "O2", "H", "O"])
|
|
|
|
|
|
print
|
|
print " Comparison between Chem potentials and element potentials:"
|
|
print
|
|
s_mu_H2 = "%11.4e" % mu_H2
|
|
s_lam_mu_H2 = "%11.4e" % (2.0*lambda_H)
|
|
print "mu_H2 : ", s_mu_H2, ", ", s_lam_mu_H2
|
|
|
|
|
|
s_mu_O2 = "%11.4e" % mu_O2
|
|
s_lam_mu_O2 = "%11.4e" % (2.0*lambda_O)
|
|
print "mu_O2 : ", s_mu_O2, ", ", s_lam_mu_O2
|
|
|
|
|
|
s_mu_OH = "%11.4e" % mu_OH
|
|
s_lam_mu_OH = "%11.4e" % (lambda_H + lambda_O)
|
|
print "mu_OH : ", s_mu_OH, ", ", s_lam_mu_OH
|
|
|
|
|
|
s_mu_H2O = "%11.4e" % mu_H2O
|
|
s_lam_mu_H2O = "%11.4e" % (2.0 * lambda_H + lambda_O)
|
|
print "mu_H2O : ", s_mu_H2O, ", ", s_lam_mu_H2O
|