Learning Forum

[ozankekul]

Hello My Friends, nI' m trying to model NH3-oxy combustion and i have to predict temperature and emission distribution in my combustion field. Since i' m familiar with non-premixed combustion model (pdf mixture fraction) and it does not require chemical kinetics parameters, this model is very convenient for my knowledge. nMy problem is that since there is nitrogen in the fuel, i have to take into account fuel nox calculations. But there is not any option in fluent post processing to estimate fuel nox in non-premixed combustion model. Only thermal and prompt nox are included. nI have also tried the get fuel nox prediction by using species transport / eddy dissipation model but this model predicted higher temperature profile and therefore inaccurate nox emissions than experimental results. ( i remain mixing rates A: 4 and B: 0.5 default values). I think, maybe i could get more accurate solutions via eddy dissipation consept or finite rate/eddy dissipation model but arrhenius parameters are required for these models and i don't have any data related to pre-exponantial factor , activation energy etc. for my NH3+O2=N2+H2O reaction. nMy question is that , can i predict nox emissions including fuel nox via non-premixed combustion model. If there is a solution about this issue , it will be very helpful for me. nYour suggestions are very important to me and if we can find a solution , i will be able to finish my dissertation. nThanks in advance.Ozan

[wcao]

Hi Ozan,nFor non-premixed combustion model, are you using chemical equilibrium assumption? Or you are using the steady diffusion flamelet? Since you explicitly have nh3 in the fuel, the fuel NOx should be directly calculated instead of modeled by a postprocess approach. You can consider using a steady diffusion flamelet model in the Non-premixed Combustion model in Fluent with a detailed reaction mechanism in chemkin format. The link below introduced an example of such detailed mechanism. However, this is a very complex mechanism including other fuels so that you will need to clean it for nh3 combustion only.nYou can also check the article https://www.researchgate.net/publication/343918121_Comparison_of_detailed_reaction_mechanisms_for_homogeneous_ammonia_combustion in which different detailed mechanism of nh3-o2 combustion are listed.nOnce you have a detailed nh3-o2 combustion mechanism, you can input it into flamelet model and study the NO/NO2 formations.

[ozankekul]

Hello Wcao;nFirst of all, i'd like to thank for your help and detailed explanation. Since i have been working on ammonia combustion for a long time, i was gathering the reduced reaction mechanisms from the literature and i have all the nh3 reaction mechanisms which are done in the last decade. So, i have chemkin reaction mechanism, thermo file and transport file. I was trying to solve my problems with eddy dissipation consept but i was getting a lot of error and long computational time. nAs far i as i understand from your message, i can predict fuel, thermal and promt nox distribution via steady diffusion flamelet model in the Non-premixed Combustion model. nSo i will try it. I hope this way will work , otherwise eddy dissipation concept model will be a big problem for me related to computational time and errors. nThanks for your information about the solution . I will do that and advise the result .nn