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-   -   Air/Fuel Ratio (http://www.cfd-online.com/Forums/cd-adapco/55122-air-fuel-ratio.html)

wendy February 4, 2006 08:38

Air/Fuel Ratio
 
Hi All,

I would like to know some knowledge about air/fuel ratio inside STAR-CD. So does anyone know how to control the air-fuel ratio within engine cylinder for the case of direct injection? Do I need to use user subroutine for that? Or maybe I just define the mass fraction burn for stoichiometric condition in the "Ignition" panel?

I really need a help for someone and any response are greatly appreciated. Thank you!

wendy

Mehdi February 7, 2006 09:45

Re: Air/Fuel Ratio
 
Hello,

I'm also beginner in the combustion field but I think you can build a diffusion model for it and after that in the post process of your results calculate A/F in each point of cylinder. it can be calculated by mass of air to mass of fule in each point, but I don't think this will be important parameter in the diffusion flame.

Mehdi


Wendy February 7, 2006 20:34

Re: Air/Fuel Ratio
 
Hello Mehdi,

Thank you so much for your reply. I still do not know and confused about the chemical reaction inside STAR-CD. Let us assume if we define the chemical reaction as the stoichiometric condition, will the reaction within engine cylinder become lean or maybe rich condition?

I have defined my reaction as the diffusion model. As you mentioned earlier, the A/F ratio can be calculated by doing the post-processing at each cell of the calculation result. I admit that this is not so important in the diffusion flame, but I need to make sure that my reaction is on the stoichiometric reaction.

Keep in touch and waiting your reply earlier.

Wendy

Mehdi February 10, 2006 06:14

Re: Air/Fuel Ratio
 
Hi,

As i told you I'm bigginer in the Star CD, but what do you mean by defining chemicals reactions in the stoichiometric conditions?, I can't understand. In my views after geomery and flow field you have to make a model for fuel spary first or just one passage for pure gasous fuel in high velocity, then around of this fuel spary in the stoichiometric surface there is combustion, so you need a diffusion model for that which you can select from star CD moduls. I think at first try use a simple one (like EBU which assumes stronge turbulent regime if I'm right) and see results, and continue to upgrade your model. Good luck, Mehdi



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