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Johannes P. February 5, 2009 06:25

fuel injection

I wanna simulate an injection of fuel(Dodecane(L)) into a high pressure cell. I wanna have a look to the length of the injected fuel jet and to the diameter and velocity of the fuel droplets.

It's an Lagrangian Multi-Phase spray injection with atomization.The Atomization model is the "Huh-Model", the "MPI-2" is the nozzle model. Heat, Mass and Momentum Transfer are Standard with 0 for mass coef. and 1 for the slip factor.

there is one inlet and one pressure boundary created. I wanna simulate pressures between 1e+05 and 100e+05Pa. That I can see how the pressure influences the length of my jet and the velocity and diameter of my parcels

So, the problem is that the length of the jet is still constant. Doesn't matter if the pressure in the cell is initialized to 1e+5Pa or to 500e+5Pa. So, what's wrong with my simulation?

I'm running the code of version 3.26.

Maybe you've an idea;-) Thanks a lot.


P.S. I'm a student from Germany, so sorry for my bad english ;-)

Kian Mehravaran February 5, 2009 07:42

Re: fuel injection
Hi Johannes,

Are you using RANS or LES? Also, when you say length of your jet, do you mean the liquid jet, or the gas jet?

Kian Mehravaran

Johannes P. February 5, 2009 08:08

Re: fuel injection
HEY Kian, i mean the length of the liquid jet (the length of the fuel jet). What's RANS or LES?

Thank you very much.


Andrea February 5, 2009 08:26

Re: fuel injection
RANS = Reynolds Averaged Navier Stokes equations, LES = Large Eddy Simulation, they are two ways of modeling turbulence...two radically different approach.
Try to look at the cfd wiki for more info
For the injection problem, do you get the correct pressure (the pressure you want) in the injection chamber? Have you verified that?

Johannes P. February 5, 2009 09:14

Re: fuel injection

ok, than i use RANS!

I get definitely the right pressure in the chamber.

try tp find sth. in the WIKI.

thanks, Johannes

Kian Mehravaran February 5, 2009 10:07

Re: fuel injection
Now the next question is how do you calculate the length of the liquid jet? By looking at the volume fraction? or do you look at the droplets directly? What is the temperature in the chamber? It could be that evaporation is very dominant in your case.

Kian Mehravaran

Daniel February 19, 2009 09:45

Re: fuel injection
Hello Johannes,

Although I am not familiar with star, my first guess is that you are doing an incompressible simualtion. In that case, the results do not depend on the actual level of the pressure, but just on the pressure gradient. If so, both initializations should lead to the same results.


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