Learning Forum

[Sem B]

Hi everyone!

I'm currently trying to simulate a premixed NH3-flame (steady-state).

I've imported the GRI 3.0 mechanism. I've selected Species Transport, volumetric reactions, Eddy-Dissipation concept and applied a velocity inlet (1 inlet) where I've specified mole fractions of NH3 and O2 which is at 300 K. Additionally, I've initialized the domain with a temperature of 2500 K in order to ignite the mixture. The temperature contours however show 300 K in the entire domain after simulating, and the NH3 doesn't react.

Before running this simulation, I've used the same settings for methane-air mixture (even without initializing T=2500 K) and this does react.

Do you have any tips on how to solve this problem?

Thank you in advance!

[Vijay Narayan]

Hi Sem,

The GRI mechanism is suitable for Natural Gas (Methane) fuel and wouldn't contain the reaction kinetics for Ammonia fuel.

You would have to import a relavant Ammonia chemistry file for the simulation to run successfully.

[Sem B]

Hi Vijay,

Thank you for your response. I've indeed noticed that the GRI mechanism is mainly suitable for natural gas combustion, but I assumed it might also contain the kinetics for ammonia combustion. Now, I understand that I'll need a different mechanism. 

I've been trying already to import the mechanism by Nozari (https://doi.org/10.1016/j.fuel.2015.06.075). However, as soon as I import the mechanism, Fluent doesn't give any error, but Fluent just shuts down. I'm running Fluent from Workbench. Would this imply that the file can not be read correctly perhaps? Or can this be caused by something else?

[Vijay Narayan]

Hi Sem,

Could you try opening the mechanism in CHEMKIN platform. It could give some idea on potential issues (maybe some errors in the CHEMKIN format used). Otherwise, i shouldnt see any other reason for not opening in Fluent. As the max number of species is only 21 (it should be good to be read to Fluent)

[felix512]

Hello all,

I have a similar problem with the ignition in my simulation.

I'm using the GRI 3.0 mechanism, for non premixed air-methane combustion, but the ignition doesn't start... And as Sem, when I do the same simulation with methane-air mixture, it works.

Do you know how I can solve this issue please ? 

Here are my parameters :

• Steady combustion, with energy model, k-e viscous model and Species Transport model (using GRI 3.0 + Eddy Dissipation Concept)
• Air inlet velocity (I tried 2,4 and 6,1, but it doesn't works...), 300K
• Fuel inlet velocity 5 m/s, 300K, 100% methane
• Outlet pressure of 101kPa
• Coupled Pressure scheme, and 2nd order for spacial discretisazions

I'm trying to reproduce a simulation I found on a paper, to learn and improve in combustion simulations. Hence, normally these parameters are correct (according to the paper, which succeed to do simulations with these parameters...).

So I don't get why my mixture doesn't ignite, can you help me please ?

 

Thanks.

[Vijay Narayan]

Hi Felix,

I have responded to your post in Ansys Forum. Just to rule out my confusion - why do say methane-air system doesnt ignite and air-methane system ignite. Isnt both the same ?