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Outlet mass flow rate

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Old   January 25, 2017, 07:00
Default Outlet mass flow rate
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xab
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xabi
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Hi friends,

I am trying to simulate the suction port of an oil pump in order to set the minimum oil level needed in the sump so that the pump doesn't suck air.

The problem I'm facing is that I know the volumetric flow of the pump but I can't set a mass or volume flow in the outlet (wich would be the inlet of the pump).

What I have been trying so far is to set the suction port as an outflow and the inlet as the mass flow inlet with oil at a certain location of the sump but here is my problem. When the simulation starts, the suction port sucks some air but from the inlet only get out oil therfore the sump starts filling.

Any suggestion?
Cheers!
Xabi
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Old   February 2, 2017, 18:34
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can you post again with a clearer description of the question. specially the last part of your question
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Old   February 6, 2017, 11:56
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xab
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Yes of course,

I have make some progres on this topic but it would be great if you could give me some more advices.

I have attached a picture of the problem. In this picture the surface A is the suction port of the pump here there is a volumetric flow of 2,15 l/min going out of the volume control.
On the other hand, this fluid is has to return after lubricating some parts to the sump. To simplify this, I have defined surfaces B and C where B is the inlet of the oil and C is de inlet of the air.

The problem is about setting the boundary conditions. I don't know the suction pressure and I am not able to set a volumetric flow at the outlet. So I need to set an inlet massflow at the Surface B (for 2.15 l/min of oil 1,72Kg/s).

When I start running the simulation, air start going through the surface A. I have attached an other image about the contour of a section perpendicular to surface A that could help to understand the situation where Oil phase is in red and air is blue.

Here, I need to modify the mass flow at the inlet to match what is going out other way, I have more oil going into the sump than out and after a while it will finish with more oil.

I have written an UDF in order to read the flow at the outlet and modify it at the inlet but I am having convergence problems. I attach here the code of the UDF.

Code:
real flux=0;
real massair=0;
real massoil=0;
DEFINE_ADJUST(profile,d)
{


Thread *tout;
face_t f;
d=Get_Domain(3);
tout =Lookup_Thread (d, 6);

begin_f_loop(f,tout)
{
flux+=F_FLUX(f,tout);
}
end_f_loop(f,tout)
Message ("mass flow %g \n", flux);
}


DEFINE_PROFILE(massair,tin,i)
{
Domain *d;
face_t f;
massair=flux-massoil;
d=Get_Domain(3);
tin=Lookup_Thread(d,8);
begin_f_loop(f,tin)
{

F_PROFILE(f,tin,i)=massair;
}
end_f_loop(f,tin)
}

DEFINE_PROFILE(massoil,tin,i)
{
Domain *d;
face_t f;
d=Get_Domain(3);
tin =Lookup_Thread (d, 7);
massoil=((flux/1.225)-0.00215)/((800/1.225)-1)*800;
begin_f_loop(f,tin)
{
F_PROFILE(f,tin,i)=massoil;
}
end_f_loop(f,tin)
}

Do you think that I am in the correct way? Is there an easyer way of doing this?

Thank you very much
Xabi
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