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-   -   Multiple Injectors (http://www.cfd-online.com/Forums/openfoam-solving/64909-multiple-injectors.html)

make May 28, 2009 08:36

Multiple Injectors
 
Dear All,

in the spray class of dieselSpray the injectors are implemented as IOPtrList. How can I define multiple injectors of different or same type in the injectorProperties dictionary?

Thanks in advance,
Matthias

sebastian_vogl May 29, 2009 03:23

2 Attachment(s)
Hi Matthias,

if you want to use several injectors, you only have to define them in the injectorProperties dictionary one after another. You write all the specifications for the first injector and then simply add the next injector with its entries. All injectors can be of the same or different type. You also have to add some entries in the sprayProperties file. Each injector has got some more specifications there. When you open this file and just scroll down, you will see some entries like: "constInjectorCoeffs", "hollowConeInjectorCoeffs", etc. According to the type of injector you choose, you will need to add the corresponding entries for each injector there.
Attached to this message are the injectorPropertis file and the sprayProperties file for a case setup in which 5 injectors of type "definedInjector" were created. Each injector creates single droplets. The injectorProperties file is quite long because the third injector makes 5000 droplets. But you can see there how you need to arrange the injectors one after another. In my case all injectors are of the same type. Of course you can choose different types.
I further used "constInjectorCoeffs" in the sprayProperties file (is also attached) to specify the droplet-nozzle diameter and the angle of injection. You just need to scroll down. As you will see, there are five entries, one for each injector.

I hope this will help you!

Best regards,
Sebastian

make May 29, 2009 10:46

Hello Sebastian,

thanks a lot. This is exactly what I was looking for.

Enjoy your weekend,
Matthias

Rachel June 2, 2009 13:33

Hello All,

I would like to ask if its possible to inject multilpe liquids with multiple injectors in dieselFoam solver ?

Thanks
Rachel

niklas June 3, 2009 02:37

Quote:

Originally Posted by Rachel (Post 217971)
Hello All,

I would like to ask if its possible to inject multilpe liquids with multiple injectors in dieselFoam solver ?

Thanks
Rachel

yup.
just specify the liquid as a mulitcomponent, lets say you want to have water and heptane as fuels

in thermophysicalProperties set
liquidComponents
(
H20 C7H16
);
and then for one injector you specify the volumefraction X as
X( 0 1 )
and for the other
X( 1 0 )

ALC May 30, 2011 12:19

I am wondering how multiple injectors can be modeled when the droplet sizes are based on a pdf (e.g. Rosin Rammler). In the example above, the parameters that changed for each injector were lists. However, in OF1.7, the Rosin Rammler distribution only allows a scalar for the diameter and does not accept a list of diameters for each injector. In light of this restriction, is there still a way to specify multiple injectors, each with a different set of pdf parameters?

Thanks in advance for any input on this issue.

niklas May 31, 2011 04:11

not at the moment, but it is very easy to fix.

I will show you how to do it for the hollowCone

go to src/lagrangian/dieselSpray/spraySubModels/injectorModel/hollowCone/
and modify the below files to this:
hollowCone.H
Code:

        scalarList innerAngle_;
        scalarList outerAngle_;
        List<autoPtr<pdfs::pdf> > dropletPDF_;

hollowCone.C (in the constructor)
Code:

    injectorModel(dict, sm),
    hollowConeDict_(dict.subDict(typeName + "Coeffs")),
    innerAngle_(hollowConeDict_.lookup("innerConeAngle")),
    outerAngle_(hollowConeDict_.lookup("outerConeAngle")),
    dropletPDF_
    (
        outerAngle_.size()
    )

and a bit further down add this before the ambientPressure-line
Code:


    forAll(dropletPDF_, i)
    {

        OStringStream num;
        num << i;
        word pdfName = "dropletPDF" + num.str();
        Info << "reading pdf " << pdfName << endl;
        dropletPDF_[i] = pdfs::pdf::New
        (
            hollowConeDict_.subDict(pdfName),
            sm.rndGen()
        );
    }

    scalar referencePressure = sm.ambientPressure();

the find the d0 function that returns the initial size and change it to this
Code:

scalar hollowConeInjector::d0
(
    const label i,
    const scalar
) const
{
    return dropletPDF_[i]->sample();
}

then go to src/lagrangian/dieselSpray and type 'wmake libso' to recompile the dieselSpray lib.

done.

the name of the pdf dictionary will now have an appended injectorindex and
the sprayProperties will look something like this (for 2 injectors)

Code:

hollowConeInjectorCoeffs
{
    dropletPDF0
    {
        pdfType        RosinRammler;
        RosinRammlerPDF
        {
            minValue        1e-06;
            maxValue        0.00015;
            d              0.00015;
            n              3;
        }
    }

    dropletPDF1
    {
        pdfType        RosinRammler;
        RosinRammlerPDF
        {
            minValue        0.0002;
            maxValue        0.0005;
            d              0.0005;
            n              3;
        }
    }

    innerConeAngle  ( 0 0);
    outerConeAngle  ( 20 20 );
}


ALC June 1, 2011 05:41

Many thanks for the instructions! They were exactly what I was looking for.

mfmohdyasin June 3, 2011 13:26

Dear Niklas,

How about the 1.6 version which has d , n, innerConeAngle and outerConeAngle as a list, but not the minValue and maxValue? As an example:

hollowConeInjectorCoeffs
{
dropletPDF
{
pdfType RosinRammler;
RosinRammlerPDF
{
minValue 1e-06;
maxValue 90e-06;
d ( 32e-06 );
n ( 2.4 );
}


}

innerConeAngle ( 15.2 );
outerConeAngle ( 86.6 );
}

How can I add similar functionality as been described by ALC?

Quote:

is there still a way to specify multiple injectors, each with a different set of pdf parameters?
Thanks,
Fairus

niklas June 7, 2011 02:39

its exactly the same


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