Learning Forum

[rajesh1234]

Hello

I see in asnsys Fluent there is a lot of different combustion models, i am study chemical engineering and i want to do a CH4 combustion process i know there is in fluent a slow chemistry and fast chemistry, can someone describe me diferences between it? I want to calculate CO and unburned full emission, can you suggest me some simply models with nice convergance in fluent to calculate Ch4 combustion and CO and unburned full emission? Model spiecies with eddy dissipation , and one step reaction will be good? How to setup spiecies with eddy dissipation to obtain co emmision?

Regards Rajesh

[Rob]

Read the documentation to see what the assumptions are and how the models are applied. If you have the reaction scheme you can also set it up via the "normal" Arrhenius chemistry solver.

[rajesh1234]

So i see Primary spiecies model with global chemical fluent mechanics with basic kinetics dont have ability to calculate CO?

[Rob]

The various models will calculate differently based on their assumptions and your input. We can, and do, calculate CO, unburnt hydrocarbons etc on a routine basis.

[rajesh1234]

Sir but what i can see in global one step Edi dissipation combustion mechanism is only CO2 and H2O spiecies but unfortunately i cant see in this way any CO results, is it possible to calculate it in one step global eddy disipation kinetics?

[Rob]

If you have a one step scheme then yes, you only get CO2 and H2O. If you want CO etc you'll need a more complete reaction scheme.

[rajesh1234]

thank you Sir for the time and effort spent to solve my problem. now I am trying two step EDM ch4 combustion. But in fluent exist only one step EDM CH4 combustion. I want to two or three step CH4-air combustion mechanism modelling. i see the FLuent documentations gives no description, for this type o reaction i have to use some other combustiopn models than EDM?
Regards

[Rob]

Then you'll need to add the extra reactions in, have you checked the tutorials and/or examples available in Help?

[rajesh1234]

So it looks like this?
CH4+1,5O2=>CO+2H2O, CO+0,5O2<=>CO2 ???

[Rob]

Pretty much. I always prefer whole molecules when balancing equations, but otherwise looks good. You may need to find the rate constants etc.