zero dimensional reactor

[Dong Wang]

Hi Everyone, 

I'm using cantera to evolve a system at constant temperature and pressure. There is a strange behavior that is freaking me out. So here is my code. 

import sys

import numpy as np

import cantera as ct

# initilize the phase

ct.add_directory('/Users/wangdong/Documents/2014_summer/cantera_input_files')

gas1=ct.Solution('test_1.cti')

gas1.TPX = 2200.0,100.0e5,"H2:1.0, He:0.17, CH4:5.38e-4, O2:4.90e-4, N2:6.76e-5"

# chemcial evolution initilzation

r1 = ct.IdealGasConstPressureReactor(contents = gas1, energy = 'off')

network1=ct.ReactorNet([r1])

data = np.zeros((50,5))

t=1.0e-10

for i in range(50):

    t=t*2.0

    network1.advance(t)

    data[i,0]=t

    print t 

    data[i,1:] = r1.thermo['H','C2H6','OH','NH3'].X

There is an error: 

2e-10

4e-10

8e-10

1.6e-09

3.2e-09

6.4e-09

1.28e-08

2.56e-08

5.12e-08

1.024e-07

2.048e-07

4.096e-07

8.192e-07

1.6384e-06

3.2768e-06

6.5536e-06

Traceback (most recent call last):

  File "evolution_0D_not_working.py", line 22, in <module>

    network1.advance(t)

  File "cantera/reactor.pyx", line 760, in cantera._cantera.ReactorNet.advance (interfaces/cython/cantera/_cantera.cpp:40599)

RuntimeError: 

***********************************************************************

CanteraError thrown by CVodesIntegrator:

CVodes error encountered. Error code: -1

At t = 1.05537e-05, mxstep steps taken before reaching tout.

Components with largest weighted error estimates:

26: 1.12675e-08

28: 2.41636e-09

35: 1.3409e-10

34: 9.25656e-11

71: 3.57017e-11

25: -3.29988e-11

13: -2.79367e-11

23: 2.31985e-11

7: -2.10332e-11

12: -2.02191e-11

***********************************************************************

However, if I reinitialize the reactor and reactorNet every time, like this: 

for i in range(50):

    t=t*2.0

    gas1.TPX = 2200.0,100.0e5,"H2:1.0, He:0.17, CH4:5.38e-4, O2:4.90e-4, N2:6.76e-5"

    r1.syncState()

    network1.reinitialize()

    network1.set_initial_time(0.0)

    network1.advance(t)

    data[i,0]=t

    print t

    data[i,1:] = r1.thermo['H','C2H6','OH','NH3'].X

There is no error and the code runs pretty well. So can anyone tell me what is wrong with the first implementation? Thank you very much! 

best,

-Dong

[Ray Speth]

Hi Dong,

This is caused by the automatic selection of the maximum internal time step which is done the first time you call 'advance' based on the time that you pass to advance. If you know that you are going to be asking for output after longer intervals, you may want to explicitly set a larger maximum step size by calling ReactorNet.set_max_time_step.

Regards,

Ray 

[Dong Wang]

Thanks, Ray, it works! 

-Dong