Learning Forum

[cehangir]

Hi, 

I am trying to simulate NOx emissions using the decoupled detailed chemistry using GRIMech2.0 Chemkin model for detailed chemistry. 

I have used COAL as fuel and using Eddy Dissipation (EDM) as Turbulence-Chemistry Interaction. Therefore, I have volatiles (C2.05H4.5O0.21) as lumped in the system. I want to use detailed chemistry for NOX production which is a slow kinetic reaction. 

When I use the decoupled detailed chemistry option with GRIMech, it gives me an error "Thermo data of species vol was not found, or species cp type not handled". 

Is there a way to resolve that issue, because it seems that EDM for coal wont allow decoupled detailed chemistry since I have volatiles in a lump in the system, which do not have kinetic/thermo data. 

[pjstopfo]

Hi cehangir,

The message indicates that the lumped 'volatiles' species is not present in the GRIMech data properties 'thermo.dat' file, so it can't find its physical properties, like specific heat (Cp). The volatiles species will also not be present in the GRIMech mechanism itself since this mechanism is intended to model natural gas and other mixtures of light hydrocarbon gases. So there is nothing to burn unless you add a reaction to decompose the lumped volatiles species into lighter fuel species present in the mechanism, e.g. methane, hydrogen and CO.

Detailed mechanisms for coal are challenging because coal has a very variable composition and may give rise to over 100 volatile species. My advice would be to use the built-in  reduced mechanisms for coal combustion and NOx formation, unless you can find or develop a detailed mechanism suitable for your type of coal. Profs. Alan Williams  and Jenny Jones at Leeds University, amongst others, have developed such schemes.

[cehangir]

Thanks for the references. I am looking into them 

 

Is it advisable to use Non-premixed model instead of Eddy-dissipation to model coal combustion for pollutant analysis? 

 

[pjstopfo]

For the standard reduced schemes in Fluent, I would recommend the Eddy Dissipation model (i.e. Species Transport). If you can obtain a detailed mechanism then you could use the non-premixed model with the laminar flamelet option.