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usker March 13, 2006 01:18

diesel engine spray and combustion
I am trying to run spray and combustion model to simulate diesel combustion. Initial conditions for air I use, 4Mpa for pressure, 920K for temperature. I am running Transient, Lagrangian Multi-Phase, Chemical Reaction, I am running for 3milliseconds, with the time step 20microseconds, so with the total number of 150 time steps. However, it seems Star CD does not calculate combustion, because at every time step maximum abs. temperature value is 920K as I have specified for initial conditions. But maximum combustion temperature is supposed to be much higher. When I try to get post data for temperature I only can see temperature distribution of spray. And also it does not give me any NOx value. Does any one has ever faced this kind of problem? Please advise. Thanks

Mork March 13, 2006 04:55

Re: diesel engine spray and combustion
You have to set the variables you want in your pstt-file. Star will not automatically write them.

Which combustion model do you use? Did you set the ignition properly?

QQ April 23, 2006 22:36

Re: diesel engine spray and combustion
Hello usker,I am doing the same thing about diesel, so I am intested in your work. And you know that in 'star' the subroutine is needed if you want to define spray, but when i want to use subroutine, I meet a problem. There isn't any warning and error in my .f file, but when i run 'star', it always tell me that there's error in my .f file. Do you hoe to solve this problem. Thanks in advance.

usker April 24, 2006 01:41

Re: diesel engine spray and combustion
Tell me in more detail how you set up the model. I have never had the same problem you have described. But if you elaborate I will try to help you. Did you install STAR-CD recently? Did you install Fortran compiler? Did you link the fortran compiler with your computer operating system?

QQ April 24, 2006 04:03

Re: diesel engine spray and combustion
Thanks so much for your warm-hearted reply,usker! I am a rookie about 'star'. I installed STAR-CD one month ago. And I have installed Absoft.Fortran.Pro.v9.0 . But I am not very clear about linking fortran compiler with my OS. Doesn't it link with OS automatically after the installation? The problem which I have faced took place when I exercised the Tutorial 9.5 C7H8 DROPLET COMBUSTION (NON-ADIABATIC PPDF) in 'star_tut'. And this morning I found that the problem I faced was about droplet other than spray. What I wanted to solve is about spray and combustion, so I looked for the 'spray injection with atomization'. Then I met another question. You know that the spray runs at the beginning of the expansion stroke. It means that the spray relates with time, so I want to know that how define the spray related with time! Thank you once again!

usker April 24, 2006 05:13

Re: diesel engine spray and combustion
Hi QQ, If your system is Windows then just go to My Computer-> Properties-> Advanced->Environment Variables, and type the link to the Fortran Compiler in System Variables Window. For example, for Absoft80 it is like:

ABSOFT C:\Absoft80 (in your case the name of folder of your fortran compiler which you installed on C drive).


LIB C:\Absoft80\LIB;

Path C:\Absoft80\BIN;

To define spray with time you need to go to Spray Injection with Atomization panel you will see there Mass Flow Rate option by default it is Fixed, but you need to create a table, where you can specify mass flow rate of your injection with time. In the main ProSTAR window you can see Table Editor. Go there and you will see Select Table Type there. You select Lagrangian Multi-Phase -> Mass Flow Rate, and you will see the table with time and flow rate data to be included to solve your problem. Give a name to your table file -> Write Table. Return to Spray Injection with Atomization and select the table you just created.

Good Luck

QQ April 24, 2006 22:36

Re: diesel engine spray and combustion
Thanks very much for your help, usker! I will keep on learning STAR-CD in the following days. If I face any problems, I will consult you again and look forward to your messeges! :)

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