Warning

This documentation is for an old version of Cantera. You can find docs for newer versions here.

Tutorial: Working with input files

CTI files

This is the typical way to create a Cantera “phase” object in Matlab:

gas1 = importPhase('gri30.cti', 'gri30');

Function importPhase constructs an object representing a phase of matter by reading in attributes of the phase from a file, which in this case is gri30.cti. This file contains several phase specifications; the one we want here is gri30, which is specified by the second argument. This file contains a complete specification of the GRI-Mech 3.0 reaction mechanism, including element data (name, atomic weight), species data (name, elemental composition, coefficients to compute thermodynamic and transport properties), and reaction data (stoichiometry, rate coefficient parameters). The file is written in a format understood by Cantera, which is described in Defining Phases.

CTI files distributed with Cantera

Several reaction mechanism files in this format are included in the Cantera distribution, including ones that model high-temperature air, a hydrogen/oxygen reaction mechanism, and a few surface reaction mechanisms. These files are kept in the data subdirectory within the Cantera installation directory.

If for some reason Cantera has difficulty finding where these files are on your system, set environment variable CANTERA_DATA to the directory where they are located. Alternatively, you can call function addDirectory to add a directory to the Cantera search path:

addDirectory('/usr/local/cantera/my_data_files');

Cantera input files are plain text files, and can be created with any text editor. See Defining Phases for more information.

Importing multiple phases or interfaces

A Cantera input file may contain more than one phase specification, or may contain specifications of interfaces (surfaces). Here we import definitions of two bulk phases and the interface between them from file diamond.cti:

gas2 = importPhase('diamond.cti', 'gas');                   % a gas
diamond = importPhase('diamond.cti', 'diamond');             % bulk diamond
diamond_surf = importInterface('diamond.cti', 'diamond_100', ...
                               gas2, diamond);

Note that the bulk (i.e., 3D) phases that participate in the surface reactions must also be passed as arguments to importInterface.

CTML files

Note that when Cantera reads a .cti input file, wherever it is located, it always writes a file of the same name but with extension .xml in the local directory. If you happen to have some other file by that name, it will be overwritten. Once the XML file is created, you can use it instead of the .cti file, which will result in somewhat faster startup:

gas4 = importPhase('gri30.xml','gri30');

Interfaces can be imported from XML files too:

diamonnd_surf2 = importInterface('diamond.xml','diamond_100',...
                                 gas2, diamond);

Converting CK-format files

Many existing reaction mechanism files are in “CK format,” by which we mean the input file format developed for use with the Chemkin-II software package. [See R. J. Kee, F. M. Rupley, and J. A. Miller, Sandia National Laboratories Report SAND89-8009 (1989).]

Cantera comes with a converter utility program ck2cti (or ck2cti.exe) that converts CK format into Cantera format. This program should be run from the command line first to convert any CK files you plan to use into Cantera format.

Here’s an example of how to use it:

ck2cti -i mech.inp -t therm.dat -tr tran.dat -id mymech > mech.cti