What steps will reproduce the problem? 1.initiate temperature to 500K 2.program is not solving the velocity 3.

What is the expected output? What do you see instead? output obtained: Traceback (most recent call last): File "F:\Book\VIII Project\Diffusion\free_h2_air.py", line 58, in <module> f.solve(loglevel, refine_grid) File "C:\Python27\lib\site-packages\Cantera\OneD\FreeFlame.py", line 73, in solve Stack.solve(self, loglevel = loglevel, refine_grid = refine_grid) File "C:\Python27\lib\site-packages\Cantera\OneD\onedim.py", line 581, in solve return _cantera.sim1D_solve(self._hndl, loglevel, refine_grid) error:

            Cantera Error!                  

Procedure: MultiNewton::step Error: Jacobian is singular for domain flame, component CH3CHO at point 6 (Matrix row 400) see file bandmatrix.csv

What version of the product are you using? On what operating system? python 2.7

Please provide any additional information below.

Hello,

You appear to be using the old version of Cantera (as shown by the capital C import Cantera at the top of your script). A number of improvements have been made to the 1-D solvers in more recent versions, so I would encourage you to update.

Best, Bryan

I believe this is caused by the fact that in the legacy Python module, the default value for the temperature fixed point is 500K. This can be changed by providing a value to the FreeFlame constructor:

f = FreeFlame(gas = gas, grid = initial_grid, tfix=600)

In the new Python module, the fixed point temperature is set to be halfway between the unburned and burned gas temperatures, so this problem does not occur.