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Lab 5 - Premixed Flames with Cantera

  • Video demonstrations of this lab can be found on YouTube at

In lab #1, we learned how to use some of the basic features of Cantera such as its chemical equilibrium solver. In this lab, we will explore some of the more advanced calculations that can be performed with Cantera. In particular, you will learn how to use Cantera to simulate premixed flames with detailed chemistry, including a freely propagating laminar premixed flame similar to the one we will study experimentally in lab #6.

Premixed flat flame

In this section we will simulate a premixed burner-stabilized flat flame with Cantera using Python. A simplified schematic is shown to the right. A premixed mixture of fuel and oxidizer are forced through a porous flat burner, usually circular. A bluish flat flame forms above the burner. In Cantera, the flame is simulated as a 1D problem, i.e. as if the burner had an infinite diameter.

The first flame that we will simulate with Cantera is a low-pressure hydrogen-oxygen premixed flat flame.

1. Open the file C:\Cantera\demos\Python\flames\flame1.py with Wordpad (or notepad). This can be done by right-clicking on the file and selecting ‘Open’ or ‘Open with...’. Browse this file, which contains the Cantera commands in the Python language. Note the similarity to MATLAB.

2. Execute the Python script file by double-clicking on it. The file extension “.py” should be associated with the Python interpreter so that double clicking the file automatically executes the Python script. Cantera will now try to find the steady state solution to the problem. While it is calculating, it will print information to the screen explaining what it is doing.

3. When the script finishes running, it will write a file called “flame1.csv” to the directory from which you ran the script. Double-click on this file to open it with Excel, and plot the species concentrations, temperatures, etc. This should give you an idea of the flame structure.

4. From Wordpad or notepad, try modifying various parameters to see how this affects the calculated flame structure. Try changing different quantities and seeing how they affect the results. For example, the initial pressure is 0.05 atm. What happens if you increase this value to 0.08? Or if you increase the mixture temperature? Make sure that after you modify the Python script that you save it before executing it.

Freely propagating laminar premixed flame

In addition to burner stabilized flames, Cantera can also simulate the steady propagation of a premixed flame through a quiescient fuel/air mixture. Cantera solves for the laminar flame speed as well as the flame structure (the temperature and species profiles). The laminar flame speed is an important concept that we will use frequently throughout the course, and studying the flame structure provides insight into how premixed flames “work.”

1. Open the file C:\Cantera\demos\Python\flames\adiabatic_flame.py with Wordpad or notepad. Browse this file, which contains the Cantera commands in the Python language.

2. As with the burner-stabilized flame, execute the Python script file by double-clicking on it. Cantera will now try to find the steady state solution to the problem. While it is calculating, it will print information to the screen explaining what it is doing.

3. After the script finishes running, a file containing the results (“adiabatic_flame.csv”) will be written to the directory from which you ran the Python script. This file can be opened with Excel by double clicking on it. It contains the calculated profiles of temperature, density, species mole fractions, etc. The velocity at a position of 0 m (cell B2) is the laminar flame speed, the eigenvalue to the problem. Try plotting the profiles in Excel. Which species have the highest concentrations? Why do some species continuously increase in concentration with increasing distance, while others decrease? Why are some species present only in the region where the temperature rapidly increases? Can you estimate how thick the flame is?

4. From Wordpad or notepad, try modifying various parameters to see how this affects the calculated flame structure and laminar flame speed. Some of the variables that you may wish to modify are p (pressure), tin (temperature of the unburnt mixture), and comp (composition of the premixed gas mixture). Make sure that after you modify the Python script that you save it before executing it.