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168 lines
5.7 KiB
Python
Executable File
168 lines
5.7 KiB
Python
Executable File
#################################################################
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#
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# Getting started
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#
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###################################################################
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# Start Python, and at the prompt type:
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from Cantera import *
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# This statement imports the most commonly-used components of Cantera.
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# Now type
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gas1 = GRI30()
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print gas1
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# If you have successfully installed the Cantera package,
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# you should see something like this:
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#
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#
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# temperature 300 K
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# pressure 101325 Pa
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# density 0.081896 kg/m^3
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# mean mol. weight 2.01594 amu
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#
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# X Y
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# ------------- ------------
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# H2 1.000000e+000 1.000000e+000
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#
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# (except that it will list many more species).
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#
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# What you have just done is to create an object ("gas1") that
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# implements GRI-Mech 3.0, the 53-species, 325-reaction natural gas
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# combustion mechanism developed by Gregory P. Smith, David M. Golden,
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# Michael Frenklach, Nigel W. Moriarty, Boris Eiteneer, Mikhail
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# Goldenberg, C. Thomas Bowman, Ronald K. Hanson, Soonho Song, William
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# C. Gardiner, Jr., Vitali V. Lissianski, and Zhiwei Qin. See
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# http://www.me.berkeley.edu/gri_mech/ for more information.
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#
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# The object created by GI30() has properties you would expect for a gas
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# mixture - it has a temperature, a pressure, species mole and mass
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# fractions, etc. As we'll soon see, it has many more properties.
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#
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# The summary of the state of 'gas1' printed above shows that new
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# objects created by function GRI30() start out with a temperature of
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# 300 K, a pressure of 1 atm, and have a composition that consists of
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# only one species, in this case hydrogen. There is nothing special
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# about H2 - it just happens to be the first species listed in the
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# input file defining GRI-Mech 3.0 that the 'GRI30' function reads. In
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# general, whichever species is listed first will initially have a
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# mole fraction of 1.0, and all of the others will be zero.
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# Setting the state
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# -----------------
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# The state of the object can easily be changed. For example,
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gas1.setTemperature(1200)
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# sets the temperature to 1200 K. (Cantera always uses SI units.)
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# After this statement,
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print gas1
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# results in:
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#
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# temperature 1200 K
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# pressure 405300 Pa
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# density 0.081896 kg/m^3
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# mean mol. weight 2.01594 amu
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#
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# X Y
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# ------------- ------------
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# H2 1.000000e+000 1.000000e+000
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#
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# Notice that the temperature has been changed as requested, but the
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# pressure has changed too. The density and composition have
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# not.
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#
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# When setting properties individually, some convention needs to be
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# adopted to specify which other properties are held constant. This is
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# because thermodynamics requires that *two* properties (not one) in
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# addition to composition information be specified to fix the
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# intensive state of a substance (or mixture).
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#
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# Cantera adopts the following convention: only one of the set
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# (temperature, density, mass fractions) is altered by setting any
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# single property. This means that:
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#
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# a) Setting the temperature is done holding density and
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# composition fixed. (The pressure changes.)
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# b) Setting the pressure is done holding temperature and
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# composition fixed. (The density changes.)
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#
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# c) Setting the composition is done holding temperature
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# and density fixed. (The pressure changes).
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#
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# Setting multiple properties
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# ---------------------------------------------------
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# If you want to set multiple properties at once, use the 'set' function:
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set(gas1, Temperature = 900.0, Pressure = 1.e5)
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# This statement sets both temperature and pressure at the same
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# time. Any number of property/value pairs can be specified in a
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# call to 'set'. For example, the following sets the mole fractions
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# too:
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set(gas1, Temperature = 900.0, Pressure = 1.e5,
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MoleFractions = 'CH4:1,O2:2,N2:7.52')
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# The 'set' function also accepts abbreviated property names:
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set(gas1,T = 900.0, P = 1.e5, X = 'CH4:1,O2:2,N2:7.52')
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# Either version results in
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#
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# temperature 900 K
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# pressure 100000 Pa
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# density 0.3693 kg/m^3
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# mean mol. weight 27.6332 amu
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#
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# X Y
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# ------------- ------------
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# O2 1.901141e-001 2.201489e-001
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# CH4 9.505703e-002 5.518732e-002
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# N2 7.148289e-001 7.246638e-001
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#
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# Other properties may also be set using 'set', including some that
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# can't be set individually. The following property pairs may be
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# set: (Enthalpy, Pressure), (IntEnergy, Volume), (Entropy,
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# Volume), (Entropy, Pressure). In each case, the values of the
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# extensive properties must be entered *per unit mass*.
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# Setting the enthalpy and pressure:
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set(gas1, Enthalpy = 2*gas1.enthalpy_mass(), Pressure = 2*OneAtm)
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# The composition above was specified using a string. The format is a
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# comma-separated list of <species name>:<relative mole numbers>
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# pairs. The mole numbers will be normalized to produce the mole
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# fractions, and therefore they are 'relative' mole numbers. Mass
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# fractions can be set in this way too by changing 'X' to 'Y' in the
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# above statement.
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# The composition can also be set using an array, which must have the
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# same size as the number of species. For example, to set all 53 mole
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# fractions to the same value, do this:
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x = ones(53,'d'); # NumPy array of 53 ones
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set(gas1, X = x)
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print gas1
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# To set the mass fractions to equal values:
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set(gas1, Y = x)
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print gas1
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