[adorean]

Hi all,

I want to simulate a DI Diesel engine combustion using a 3D, 45 deg. sector mesh.
I have found on the forum how to add engine swirl, as explained by Niklas Nordin somewhere in 2004.

1) How and where can the injector (nozzle) orientation be defined?

2) Can somebody please give me a (detailed, if possible) list of the directories, files and parameters that needs to be defined for a dieselEngineFoam case?

I suppose it should be a combination of dieselFoam and engineFoam, but I don't want to start this by guessing.

Thank you!

Ervin

[niklas]

1, in the constant/injectorProperties
2, in the constant directory.

what each dictionary controls should be clear by it's name

N

[adorean]

Thanks!

[adorean]

Hi,

direction (1 0 0) means that the injector is oriented along the positive x axis.

To rotate it 30 deg. along the y and z axes, is it correct:
direction (0 30 30) or the angle should be expressed in radians?
direction (0 pi/6 pi/6)?
Or it's none of these?

Thanks

Ervin

[lucchini]

Hi,

the direction you need is

(cos(pi/6) sin(pi/6) 1.0/cos(pi/6))

[niklas]

> direction (1 0 0) means that the injector is oriented along the positive x axis.
yes.

none of these.

I dont understand, what is unclear with the meaning 'direction'?

N

[adorean]

Well, now it's clear.

[adorean]

Hi,

A few more questions about dieselEngineFoam.
The mesh I'm using: 1/8 sector, 3D.

1) the injected mass 'mass' in 'injectorProperties' is the total injected mass by the injector/cycle or is the mass injected by 1 nozzle of the injector/cycle?

2) the mass flow rate profile, 'massFlowRateProfile' can also be expressed as a function of CAD vs. mass flow rate (if yes, how) or only as a function of time vs. mass flow rate?

Thanks.

Ervin

[niklas]

1. its the total mass injected by that injector. there's no periodicity in the time, since time is always increased, so a SOI of for instance -12 CAD will never happen more than once.

2. yes, for dieselEngineFoam it MUST be expressed in CAD's, since this is the 'time'.

[adorean]

Hi,

Trying to run dieselEngineFoam, but got this error.
Can somebody tell me what kind of error is this, and how can it be avoided/corrected?

Create engine time

Create mesh for time = -0.02


Reading thermophysicalProperties
Selecting thermodynamics package hMixtureThermo<reactingmixture>
Selecting chemistryReader chemkinReader
Reading field U

Reading/calculating face flux field phi

Creating turbulence model.

Selecting turbulence model RNGkEpsilon
Creating field DpDt

polyMesh::parallelData() const : Constructing parallelData from processor topology
This needs the patch faces to be correctly matched
Constructing chemical mechanism
Selecting ODE solver SIBS
chemistryModel::chemistryModel: Number of species = 5 and reactions = 1

Reading environmentalProperties
Reading combustion properties

Constructing Spray
Selecting injectorType commonRailInjector
Selecting atomizationModel off
Selecting dragModel standardDragModel
Selecting evaporationModel standardEvaporationModel
Selecting heatTransferModel RanzMarshall
Selecting wallModel reflect
Selecting breakupModel ReitzKHRT
Selecting collisionModel off
Selecting dispersionModel gradientDispersionRAS
Selecting injectorModel constInjector
Average Velocity for injector 0: 5.62148e+06 m/s, injection pressure = 1200 bar
Constructing three dimensional spray injection.
deckHeight: -0.0434871
piston position: 0
Total cylinder mass: 0.000673331

Starting time loop

--> FOAM Warning : Requested reference cell 0 is on a constraint boundary, selecting reference cell 1

Max Courant Number = 0

Crank angle = -179.75 CA-deg
deltaZ = 4.8849e-07
tmp<scalarfield> polyMesh::movePoints(const pointField&) : Moving points for time -0.0199722 index 1
bool primitiveMesh::checkMeshMotion(const pointField& newPoints, const bool report) const: checking mesh motion
Min volume = 3.99657e-11. Total volume = 0.000243964. Cell volumes OK.
Min area = 3.3873e-08. Face areas OK.
Pyramid volumes OK.
Non-orthogonality check OK.
Mesh motion check OK.
clearance: -0.0434876
Piston speed = 0.0175857 m/s


--> FOAM FATAL ERROR : face 0 and 1778 areas do not match by 0.0249476% -- possible face ordering problem

Function: cyclicFvPatch::makeWeights(scalarField& w) const
in file: meshes/fvMesh/fvPatches/derivedFvPatches/cyclicFvPatch/cyclicFvPatch.C at line: 62.

FOAM aborting

Thanks.

Ervin

[mattijs]

This means that your cyclics don't match. Probably they don't match on the starting mesh.

Did you follow all the steps:
- have binary mesh writing enabled
- set startTime to latestTime
- convert mesh from Gambit or whatever mesh generator you use.
- create a cyclic patch from the two halves ('createPatch')
- copy back the resulting mesh to the constant directory
- reorder the cyclic patch faces
('couplePatches')
- copy back the resulting mesh to the constant directory
- try rerunning the couplePatches util. It should now not complain.

If you want to do engines: layer addition/removal with cyclics has problems and will probably not work.

[adorean]

Hi Mattijs,

What's this error? Appears at createPatch.

--> FOAM FATAL IO ERROR : cannot open file

file: /home/ervin/OpenFOAM/ervin-1.1/run/tutorials/dieselEngineFoam/motor5/system/crea tePatchDict at line 0.

Function: regIOobject::readStream(const word&)
in file: db/regIOobject/regIOobjectRead.C at line: 68.

FOAM exiting

Ervin

[niklas]

Hmmm...

-> FOAM FATAL IO ERROR : cannot open file
self-explanatory...

file: /home/ervin/OpenFOAM/ervin-1.1/run/tutorials/dieselEngineFoam/motor5/system/crea tePatchDict at line 0.
self-explanatory...

an example of the dictionary can be found here
utilities/mesh/manipulation/createPatch/


N

[mattijs]

See also

http://www.cfd-online.com/cgi-bin/Op...st=997#POST997

[adorean]

Hi,

The last run of 'couplePatches' produces this:

"Create morphMesh for time = -180

Mesh has coupled patches ...

Testing for correct face ordering ...
cyclicPolyPatch::order : Found 53 on patch slice where the cos of the angle between two connected faces was less than 0.9
cyclicPolyPatch::order : Writing zone 0 face centres to OBJ file "slice_zone_0.obj"
cyclicPolyPatch::order : Writing zone 1 face centres to OBJ file "slice_zone_1.obj"
cyclicPolyPatch::order : Number of faces per zone:2{1778}
cyclicPolyPatch::geometricOrder : Rotation : n00 0 1) n1-0.707107 0 -0.707107)
cyclicPolyPatch::order : Dumping newly found cyclic match as lines between corresponding face centres to file "slice_faceCentres.obj"
Patch face ordering OK.
Coupled patch face ordering ok. Nothing changed ...

End"


Except the complaint about those 53 faces "where the cos of the angle between two connected faces was less than 0.9" I don't see nothing wrong.

The 53 faces are the ones situated on the cylinder axis. The angle is 45 deg., so of course that cos is less then 0.9. Is this a problem?

Running the case produces the above mentioned "FOAM FATAL ERROR : face 0 and 1778 areas do not match by 0.0249476% -- possible face ordering problem " error.


Any hints? What am I doing wrong?

The controlDict is:

applicationClass dieselEngineFoam;

startFrom startTime;

startTime -180;

stopAt endTime;

endTime 30;

deltaT 0.25;

writeControl runTime;

writeInterval 5;

cycleWrite 0;

writeFormat ascii;

writePrecision 12;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

runTimeModifiable yes;

adjustTimeStep no;

maxCo 0.2;

maxDeltaT 1.0;


Thanks!

Ervin

[mattijs]

couplePatches seems to find no problems. Have a look at the file

slice_faceCentres.obj

it creates. (with e.g. javaview or run objToVTK and use vtk). It will show the connected (centres of) faces.

The tolerance issue has been discussed before on this site. Use the 'search' functionality to find these.

[adorean]

Hello,

Can somebody please tell me some guidelines for a control dictionary for 'dieselEngineFoam'?

- Courant number should be kept around 1?
- deltaT=? for compression & injection?
- adjustTimeStep no/yes?
- maxDeltaT?

Thanks!

Ervin

In spray calculations, I found that a courant number around 0.1 works better. 1 sounds way off to me.

deltaT is just the initial parameter, as long as you have adjustTimeStep yes (which I think you should have). So set it around 1e-8 to be safe.

maxDeltaT, I'm not sure this one matters, I heard it's a part of an old code, but I usually set it to around 1e-6.

/Fabian

[adorean]

OK, Fabian.

Thanks.

Ervin

[lucchini]

maxDeltaT in an engine simulation is the MAXIMUM CRANK ANGLE (and not the TIME STEP) and it should be kept around 0.1
usually you have to set something like
adjustTimeStep yes;
maxDeltaT 0.1;
maxCo 0.1;
but you have also to investigate how the solution changes with the maxCo value.
bye