[the_sixth_hokage]

Hi..

My boundary conditions are
Methane mass flow inlet
Oxygen mass flow inlet
Pressure Outlet at 5.6MPa

Operating pressure 0.

I'm simulating a combustion at high pressure and there shouldn't be any reversed flow..and the no of faces only seems increasing in number near to convergence (1e-05 , 06 residuals)

When I checked the pressure contours maximum pressure is only 5.14Mpa and minimum 4.98MPa..

My mesh orthogonal quality is 0.99753..

[RaiderDoctor]

Hi, this isn't really descriptive of your problem. Could you provide pics of your fluid domain?

[the_sixth_hokage]

Originally Posted by RaiderDoctor

Hi, this isn't really descriptive of your problem. Could you provide pics of your fluid domain?

Hi I solved the reversed flow problem...


I am using a steady state, pressure based, species transport, EDC , k Omega SST model...
My domain is a 2D combustion chamber..

The residuals vibrate near to convergence...I am using animation to get contours for every 10 iteartion...and my required temperature contour was seen...but after next 10 iteartion it changes shape...and after maybe 30 iteartion the desired contour repeats...

The continuity and Omega residual vibrate in the range of ( e+01, e00, e-01)...I have run it upto 13,000 itreations..still no convegence...other residuals are in the range of 1e-05...

[RaiderDoctor]

It sounds like you're tackling an interesting problem. From what you've said, I think you might have a bad mesh. But without pictures of it, or the fluid domain, I'm not sure.

[the_sixth_hokage]

My geometry is relatively simple..mesh orthogonal quality is 0.998... my mesh is concentrated at the region of interest..

[vinerm]

Is it an axisymmetric case or planar? Since combustion usually takes place away from the walls, is not well suited for application until and unless you are also interested in heat transfer at the walls and the walls are curved, which doesn't appear to be the case. Secondly, EDC is not an easy-going combustion model; its tricky and usually requires a solution from non- or partially-premixed model. Reverse flow, as you observed, is because of lower pressure in the combustor as compared to that at the outlet. There could be two reasons for that, either the mass flow rate of fuel and oxidizer are not enough or the energy release is not sufficient to increase the pressure. I suppose you are using ideal gas for the density. It is also recommended to use specific heat and thermal conductivity as a function of temperature, if that is not already being done.

How many reactions do you have in your model? If it is not more than two, then prefer using FR/EDM. Even with more than that, you can still use FR. EDC also requires that the reaction time be much smaller than turbulence time scale. However, these only affect the numerics and not the physics.