Implementing Heterogeneous reactions for DPM injected particles.

[shanmugapriyansv]

Greetings, 

I am trying to implement combustion model wherein I inject waste particles using DPM. Also, I included finite rate/eddy dissipation model for homogeneous (volumetric reactions) and heterogeneous (particle surface reactions) reactions. It created a mixture waste-species which contains fluid as well as solid carbon (which I mean to be char). All properties of waste are included in coal calculator (proximate and ultimate anaysis data). When I solve the model, I find DPM mass source, DPM C concentration and consequently the rate of all heterogeneous reactions are zero. How should I correct this? How to tell fluent that the waste particle injected using combustion model does contain some solid part which is the solid carbon included as solid species in species transport model and the fixed carbon in coal calculator? Also, fluent shows mass imbalance warning for volumetric reactions even when the stoichiometry and mass are balanced. 

Thank you ! 

[SamW]

I would double-check your DPM injection source and materials setup to confirm that the material properties are set up properly for the coal particles. Are you seeing particles enter that are just not reacting or otherwise interacting with the Fluid (Eulerian) domain?

For the reactions it's worth double-checking the molecular weights in your materials for the species in any offending reactions, maybe there is some issue there instead of in the stoichiometry.

[shanmugapriyansv]

Thank you, I'll look into the molecular weights of all species defined. Regarding the DPM injection, I can see the injected particles and DPM mass, momentum and energy source are updated. Even DPM vol source and CO2 source are being updated while O2 source acts as a sink due to its consumption during oxidation. My only trouble as of now is I find my DPM C concentration is zero. Here is how I implemented:

1). I defined my combustion particle to be waste in DPM and I have defined their elemental composition in coal calculator where I have named is as waste too. i

2). There is a waste-species mixture created under mixture which is the fluid flowing in the whole domain. Under this mixture, I have defined few fluids and I have defined C as solid species. 

3). I have implemented the heterogeneous i.e solid- gas reactions like C+ O2, C+CO, C+COetc under particle surface reactions in finite rate/ eddy dissipation head in speceis transport model.

I found my DPM C concentraion to be zero and consequently all my heterogenous reaction rate. Note: I just expected my waste to be a mixture of char + volatiles; char is the fixed carbon I defined which is also the solid carbon defined under waste-species mixture. Is my implementation correct?

[SamW]

So your "DPM Concentration" is non-zero, but your added solid species "C" concentration is zero? I would double-check your coal injection method and ensure that the C material is appropriately included. Here is an example of a quick coal particle surface-based injection I mocked up:

If you do not have this setup option enabled, make sure you are using "multiple-surface-reactions" for your coal particle:

Of coarse, you will also need to enable the reaction in your kinetics setup for the mixture:

Maybe your reactions are different, but hopefully this gives you some insight into what might be missing in your setup