[goldencatto]

Hi,

I am modelling a non-premixed combustion of a 60 degree light-duty diesel sector mesh and I am trying to model the effects of EGR (just the effects) into my system. I found a formula saying that the EGR% = (CO2%)intake/(CO2%)exhaust * 100%, and I am trying to incorporate 5% EGR into my system but I am confuse about how to do it in Fluent. Do I do this under the Boundary tab in the Species settings? If so, does the Fuel column represent the intake and oxid represent exhaust?



Thank you in advance

[Cramsay]

You would just replace 5% of the original air mixture (O2 and N2) with CO2, H2O and more N2. And yes you'd just hit add where you have it if you're planning on using the chemical equilibrium model. Boundary is the oxid is the initial oxidiser stream, fuel the fuel stream e.g. discrete phase evaporated species.

Easy way to estimate exhaust gases is a relation which comes from Heywood I think, linked formula.

Then just substitute 5% of what you calculate into the oxidiser boundary stream.

Just as a quick heads up, if you're just planning on doing diesel combustion try find an n-heptane chemkin mechanism and thermal database with less than 50 species (hard limit in Fluent for some reason for this model) and use the diesel unsteady flamelet model as it's the least buggy of the lot of them.