Species Transport – Relax to Chemical Equilibrium Model Source Term

- March 10, 2020 at 7:12 pm
  
  Benoit85
  Subscriber
  
  Hello,
  
  I'm using Fluent 2019R3. I'm running a combustion simulation with species transport + volumetric reactions + ED (eddy dissipation) turbulence interaction (thus assuming fast chemistry).
  
  I tried to apply the "Relax to Chemical Equilibrium"-option and this is what happens: the oxidizer (N2O @ 290K) gets converted to O2 and N2 almost immediately after entering the domain. This is not physically realistic.
  
  I'm trying to understand what Fluent is doing and thus why this happens.
  
  Question 1 (general):
  Why does it happen?
  
  Question 2:
  The theory guide states that the "Relax to Chemical Equilibrium"-option can be 'considered as an extension of the ED type models where species react towards chemical equilibrium instead of complete reaction'. When Relax to Chemical Equilibrium is selected, the source term in the species transport equation becomes:
  
  In the final species transport equation, does this source term replace the one of the ED model, or is it added alongside the ED source term expression?
  
  Question 3:
  I'm having troubles finding any explanation on the "Temperature Threshold"-option that appears in the Species dialog box when Relax to Chemical Equilibrium is selected... What does it do?
  
  Thank you for any clarification!