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usker October 24, 2007 09:03

Multifuel Diesel Spray and Combustion
Hello everyone,

1) How my results will differ if I select droplet properties from database (for example, for Dodecane) or if I use subroutine DROPRO and FULPRO in "Droplet Properties". I think in Star-CD there is an extensive property database for each fluid included by adapco, so why to use subroutines?

2) How to use two or more different fuels (Dodecane, Heptane, etc) in one spray. If I want to make subroutine for each fuel, how to link the fuel and that particular subroutine.

In case of using two or three fuels, in "Evaporates to Scalar", shall I choose each relevant scalar?

Please provide some information on how to model multifuel diesel spray and combustion.


Andrea October 27, 2007 05:08

Re: Multifuel Diesel Spray and Combustion
1) You can use the Star-Cd database to compute droplet properties only if you use Epthane, Dodecane, Octane and something similar...for other fuel types you need to specify a "standard" fuel with his properties...and you use dropro.f instead the database. Also, if you want to modify some properties of docacane, for example, it's easy to do with dropro.f...and it's impossible to do with the database in some cases!
2) Sorry...I'm looking for something similar...
If someone has any info please post it because I'm interested too

hayate October 30, 2007 06:03

Re: Multifuel Diesel Spray and Combustion

andrea i ask everywhere.... still have not found any help....

usker October 30, 2007 08:05

Re: Multifuel Diesel Spray and Combustion
Andrea, thank you for your reply.

I think if I want to modify dodecane properties in dropro.f I only can modify surface tension coefficient and density. As I can see in that subroutine, these two properties are calculated using the data from the database, am I right? As I thought, in Star-CD database those data were included depending on each other. I think if I want to modify certain properties of dodecane and set a relationship with others then I have to include all thermodynamic data in that subroutine, so that in my Fortran code I write a program to calculate certain property extrapolating data from the list of data I included. I think Dodecane dropro.f subroutine was written only for dodecane, because properties in that subroutine are linked to dodecane data in Star-CD database. am I right?

Please correct me if I am wrong.


Andrea November 1, 2007 10:16

Re: Multifuel Diesel Spray and Combustion
Well in dropro.f you can modify surface tensione coeff. and density as you said but you can do that for any fuel you want...and you can modify also the other properties of that fuel (ps,drvis,...). Just use drty,1,stand and fuel,stand (a "standard" fuel) when you define droplets properties and use user coding. Star then refers to subroutine dropro.f for any properties you have specified and there you can do what you want without referring to the database. If you use the sample coding for dodecane, there you can see the function fuelfn(), and you're right: that's the internal calculation of fuel properties by means of database. You can also use that for other fuels...and you can calculate some properties by means of your formula and other properties by means of the database...the properties in the database depends only from TD as you can see in dropro.f, the droplet temperature.

Andrea November 1, 2007 10:17

Re: Multifuel Diesel Spray and Combustion
So I'm not THE ONLY ONE with this problem...sorry for that situation!
Thanks anyway!

Andrea November 1, 2007 10:20

Re: Multifuel Diesel Spray and Combustion
Hope that helps!
Regards, Andrea

hayate November 1, 2007 12:18

Re: Multifuel Diesel Spray and Combustion
hello all

i did that...... yesterday after 12 days i create my simulation......

thanks to andrea , usker, maurizio and all the other engineers

feel free to contact me for any details

i am very happy


usker November 1, 2007 20:24

Re: Multifuel Diesel Spray and Combustion
Congratulations hayate!

Was that simulation about multi-component diesel fuel spray and combustion? If yes, please share your knowledge:)


hayate November 2, 2007 03:21

Re: Multifuel Diesel Spray and Combustion
we create a diesel + bioathanol mixture simulation,

2 things that we understand are

1) the combustion chamber much change due to the mixture has different visconcity and can not spray very good to the chamber

2) the no2 and co2 are less due to the fact that the chamber can not burn the hole amount of mixture.

please feel free to ask me about simulation.

Andrea November 2, 2007 04:33

Re: Multifuel Diesel Spray and Combustion
Congratulations hayate!
So you're simulating a fuel mixture! I have some question about it:
1- How do you simulate the fuel mixture? In this sense: your injection is a set of 2 droplet types and every droplet evaporates to one different scalar? 2- What combustion model do you use? And if you have 2 scalars for the fuel you have 2 different chamical reaction scheme that operates simultaneously?
Thanks you for sharing your knowledge! :)

hayate November 7, 2007 03:54

Re: Multifuel Diesel Spray and Combustion
dear friends

i am apologies for the delate of my answer, i had a lot of thing to do this week and i had no time to responce,

well what i did... i download a free code named openfoam, it is a linux based cfd code that has a great manual, the person who wrote it .... knows a lot...

in the manua it is describe how to create a mixture fuel srpay in the diesel engines, so i take the manual and the software and sit down and i create it, it is very easy to do that and also you do not have to crash your head with star cd..... after i create the analysis i understant how to do the analysis in star but i did not do that in star because i already create it in an opensource software....

if you have a minute download the software fron the site nad read the manual.... you will understant a lot...

if you do not....

tell me to send you with an email the step by step analysis guide.

best regards hayate

Andrea December 1, 2007 20:08

Re: Multifuel Diesel Spray and Combustion
Thanks for your suggestions Hayate, I'll look at that code as soon as possible
Thank you very much
Best regards!

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