I am working on diesel engine combustion simulation with STAR-CD3.24. The fuel, C12H26(liquid) was injected into cylinder and then evaporation took place. Lagrangian Multi-Phase Model was used. Now I want to obtain the mass of liquid C12H26 and the mass of C12H26 vapor in every cell. How can I do that? By the way, what's the meaning of Scalar, Mix_Frac-Fuel_1? Thank for your any help.

Jim

May, 9, 2008

Hi,
what model do you use for your simulation? I suppose you have a scalar for the C12H26 vapor and that the liquid fuel evaporates into it (by the command drmc,1)...
Well if this is your situation then just look at the mass of that scalar inside tha cylinder and you get the mass of fuel vapor at the specified angle observed...write down a .pstt file to look at transient solutions.
The mass of liquid can be plotted by the dplot command after you load the droplet data (getd...)
The scalar mix_frac_fuel probably indicates the fuel fraction in the mixture of fuel+air in the cylinder...again what model of combustion do you use?
Bye!
Andrea

Thank you very much! Yes~ I use C12H26 as a fuel for diesel engine combustion simulation. C12H26 vapor is scalar 1. The EBU LATCT model and Shell auto-ignition model are used. I know how to get the mass of scalar with registors and also that how to plot the characters of droplets with command getd. But I want to know the mass sum of liquid C12H26 and vapor in every cell for equivalence ratio calcution. Can you tell me anything about that? Thanks a lot.

Jim

Well, remember that the equivalence ratio is referred ONLY to air and fuel vapor...so if you want to calculate the equiv ratio for your sim you only need the C12H26 concentration, the mass of air in the cell (m_O2/0.233) and the stoichometric ratio of the combustion...not the liquid mass of fuel inside the cell.
Then if you want the sum of fuel and vapor in every cell for other computations, you can operate on registers (menu post->operate) and get the sum of liquid mass and fuel vapor as you wish.
Hope that help! Bye!
Andrea

Thanks a lot! I try to do so as you say. But ONLY C12H26 vapor(scalar 1)can be loaded into register easily by command getc, oper getc NSC, or through the GUI menu, post->operate. I can't find COMMAND for loading the properties of DROPLET or LIQUID C12H26 (I didn't define the scalar C12H26(L). Can that be done in PROSTAR?). Can you tell me what command should be used to get liquid C12H26 or droplet properties into register in detail, Andrea? Thanks!

oh~I found that command getd can load droplet information from .pstt file ,then the information can be plotted on screen. but the information isn't saved into register 1~6. The same is command dlist which can lists droplets properties. Is there any command to load DROPLET to register. Well, FIRE can output the information of liquid fuel, vapor and equivalence ratio (seems to be the ratio of the sum of liquid an gas of fuel to the air) easily. So I think PROSTAR can also do that. But the command ... Can you tell me more about that aspect? Again~ thanks a lot!

Jim

Hi,
the only way I know to look at droplet data (apart from plotting it...) is to look at the .trk file...you can load if also from the Star-Gui Panel but I think that's not useful for you: there you can find only the mass of a droplet and where it is during the simulation...not other things.
But again, remember that equivalence ratio is defined apart from the liquid mass of fuel...the local equivalence ratio is defined ONLY with the VAPOR FUEL
Regards,
Andrea

[sthamit]

Originally Posted by Andrea
;175811

Hi,
what model do you use for your simulation? I suppose you have a scalar for the C12H26 vapor and that the liquid fuel evaporates into it (by the command drmc,1)...
Well if this is your situation then just look at the mass of that scalar inside tha cylinder and you get the mass of fuel vapor at the specified angle observed...write down a .pstt file to look at transient solutions.
The mass of liquid can be plotted by the dplot command after you load the droplet data (getd...)
The scalar mix_frac_fuel probably indicates the fuel fraction in the mixture of fuel+air in the cylinder...again what model of combustion do you use?
Bye!
Andrea

Hi Andrea, I am kind of new to this but I have trying Unpremixed/EBU LATCT with 4-step Auto-Ignition. Looks like I am not getting fuel vapor as combustion is not taking place. I, however, don't know how to check the mass of fuel vapor or check transient solutions. Since I am kind of new to this, I would really appreciate if you could give some step wise guidelines with useful commands to check mass of fuel vapor, write and plot.

Thanks in Advance