[hashim84]

How are you doing all? Hopefully, everyone is doing well!
I want to ask you question, could I?
I am running EDC( Eddy Dissipation Concepts Model)
But the problem is the time for hot flow, it takes long time like around 7 days or more.
What is the problem in your opinion? What can I do to solve this problem? Please, I need your experience to help me solve this issue.

Thank you so much
Hashim

[hashim84]

How are you all?
I have some problems that I am facing with my project.
1- Right now, I am running EDC ( Eddy dissipation concept model) in Ansys Fluent.
But the problem is the time for hot and soot flow, it takes long time like around 10 days or more.
What is the problem in your opinion?How can I reduce the time for EDC running to be converged?
2- I run many cases with EDC, and if I run the same cases with PDF(Non-premixed Combustion) model in Ansys Fluent, the adiabatic flame temperature would be different for PDF models (1800K), but in EDC ( T= 2200K and above). So the difference is around 400K or more sometimes. Just for your information ( everything is the like the geometry, meshing, and the boundary conditions.
3- For some cases, I got CE ( combustion efficiency) less than the ones in the experiment. I am getting 97.5 to 98.11, but I want 99 or above. How can I improve that?

Thank you so much
Hashim

[macfly]

Hi,

Lots of details are missing... Nobody can help you without information.

What is the geometry?
What is the mesh?
What combustion reaction are you modeling?
Steady or transient?
etc.

[hashim84]

Thank you so much macfly!
The geometry is like a cylinder with 1 meter diameter (for air), and it has in the center jet for the fuel, which is 3 types of fuel I have for different cases.( the main fuel for some cases is methane) for other cases, the fuel is just 100% c2h4. As attached. The process is flare system, we are burning fuel and we want to get a flame with little soot and high combustion efficiency.
2- The mesh which i am using is hexa, and it is very fine in the center with minimum orthogonal quality = 8.939 e-1 and Maximum Aspect Ratio= 6.923 e+1. Also, as attached.
3- I am using the steady, and the species transport, volumetric, Eddy Dissipation Concept Model. And Soot Model is used as well (Moss Brooks)
4- We are using Mechanism File with 50 species, which was built by Chemkin Software.
5- For Boundary Conditions, I give for inlet jet (different velocities, diameter, and the mole fractions for fuel inlets). As well as, I give for the inlet air (velocity, and diameter (1 meter).
We have different jet velocities (from 0.28 to 2.44 m/s) depending on the case we are running and 3 different types of jet diameter (1”, 1.5”, and 2")
6- The other steps i do the same in Ansys Fluent User Guide.


I am not good in Ansys, I am still working on it.
Please, I need your help.
Any help or suggestions, thoughts, answers, I will be very thankful for them
Thank you so much
geo.jpg

22222.jpg

meshing.jpg

[macfly]

Unless you are using a super computer, it is not surprising that your case takes a long time to converge if there are 50 species. There are 49 species conservation equations?

Regarding the flame temperature, did you check the adiabatic flame temperature of the reaction with a chemical equilibrium software (e.g. https://cearun.grc.nasa.gov/)? This is the maximum temperature that Fluent should not exceed. I'm surprised that EDC gives 400 K higher than Mixture Fraction even if you use a complex mechanism, but I'm not familiar with complex mechanism... Maybe someone else can help you about this.

[hashim84]

Thank You for answer!
I am using 2 computers with 12 processors for each.
The previous mechanism was 92 species! They used it for 2 last years.