Heat release rate of each reaction

[Inna G]

Hi guys,

I am new to Cantera and I am using Python environment to predict ignition delay times and excitation times. I am currently trying to determine which reactions have the maximum contribution to total heat release for 0-D Ideal Gas Reactor at the time of maximum heat release. I calculated the maximum heat release using following formula heat_release_rate2[i]=(np.dot(gas.net_rates_of_progress, gas.delta_enthalpy) ) which gave me 3.114e+14 for the total volumetric heat release. However, when I am trying to calculate the heat release of each reaction it is giving a total volumetric heat release of 3.22. I am not sure where I am going wrong.. This is part of my code for calculating it:

q=np.zeros((710))

z=np.zeros((710))

w=np.zeros((710))

outfile = open('reaction.csv', 'wb')

csvfile = csv.writer( outfile )

csvfile.writerow(['Reaction', ' delta enthalpy [J/kmol]', 'net rates of progress [kmol/m^3/s]'])

for i in xrange(int(x1)):

        if heat_release_rate2[i]==h_max2:

                t_x=times2[i]

                II = [k for k, r2 in enumerate(gas.reactions())]

                for k in II:

                        q=gas.reaction(k).equation     

                        z=gas.delta_enthalpy[k]

                        w=gas.net_rates_of_progress[k]

                        csvfile.writerow([q, z, w])

                print (np.dot(gas.net_rates_of_progress[II], gas.delta_enthalpy[II]))       

                print (heat_release_rate2[i])

                print (t_x)

                print (h_max2)               

     

outfile.close()

Thanks,

Inna

[Ray Speth]

Inna,

You showed one method of calculating the heat release rate:

    np.dot(gas.net_rates_of_progress, gas.delta_enthalpy)

which is correct, but you did not explain the other method you are using. The only other straightforward method would be to sum over the species instead, by calculating:

    np.dot(gas.net_production_rates, gas.partial_molar_enthalpies)

These methods should give you the same answer to within a relative tolerance on the order of the working precision, around 1e-16. If you're still having trouble, it would help to show an example which is simplified but still complete.

Regards,

Ray

[Inna]

Hi Ray,

Thank you for your reply. I tried the second method you suggested and the problem still persists. I attached the simplified version of the code.

Thank you.

Regards,

Inna 

[Ray Speth]

Inna,

Thank you, that helps clarify the problem. The issue is that you never update the state of the Solution object (gas) in the second loop, so it just has whatever state that it did at the end of the reactor network integration (which presumably had reached a near-equilibrium state where the heat release rate is essentially zero). If you want to do calculations after the fact, you will need to also store the temperature, pressure, and mass fractions after each time step so that you can set the Solution object to that state later.

Regards,

Ray

[Inna]

Hi Ray,

Thank you very much for your help. I really appreciate it. I will try it next week and will let you know if I have any further issues.

Kind Regards,

Inna

[JM7]

Hi Inna, did you get or figure out how to get the heat release rate?, you mind to share the solution code.

Thank you