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Diesel Engine Combustion

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Old   June 19, 2010, 03:14
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  #21
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Arun
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Hi Georg,

Can I know which chemistry input file you are using for the combustion chemical kinetics representation?

If you happen to use chem.inp_15 you can try change this:

C7H16+11O2=>7CO2 + 8H2O 1.00E+8 0.0 15780.0!

CHANGE TO

C7H16+11O2=>7CO2 + 8H2O 5.00E+10 0.0 10000.0!

There are few SAE papers that uses arrhenius rate parameter modification method to match their case setting, you can try refering that...

Regards
A
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Old   June 21, 2010, 13:35
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Hi arun,

thank you very much for your reply.
I don´t think I can fix heat release by changing Arrhenius coefficients. This may change ignition delay and fuel conversion rate, not energy content, right?

I am using the 1-step mechanism so far. The conversion rate seems not too bad for the investigated engine case.

Regards,
georg
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Old   August 17, 2010, 00:56
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Arun
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Hi Georg,
From my previous experience, the heat release is highly dependent on the Arrhenius coefficients. If these values is not proper, the combustion will start too late during the engine cycle which will lead to partial burn of injected fuel due to lower pressure in the expansion stroke (i.e. late combustion in expansion stroke). Hence, giving you lower values of pressure trace and amount of fuel consumed respectively.

By increasing the “A” value the rate of the reaction is increased and by decreasing the “E” value, this exothermic reaction will occur more easily.



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Old   December 18, 2011, 02:06
Default Running motored case with dieselEngineFoam
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Carl
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Dear Foamers,

I am currently running a motored case simulation with dieselEngineFoam. I delayed the SOI to very late so that no fuel is delivered with the 1st cycle (-180 to 180). However, the simulation seemed to stop at Top Dead Centre because the timestep did not progress anymore after I waited for quite some time. No error message appeared in the log file and hence I couldn’t really sort of the reason. I anyhow observed that the piston speed and deltaZ turned into negative numbers when the piston reaches TDC.

Courant Number mean: 0.00302152 max: 0.247541
deltaT = 5.14141e-07
Crank angle = 0.0238475 CA-deg
deltaZ = -2.36259e-09
clearance: 0.00210001
Piston speed = -0.00459523 m/s

Can anyone give me a little advice why did the simulation just ‘stop’ at TDC?

The following are my input for blockMeshDict, boundary.org, engineGeometry, pressure boundary condition as well as the controlDict file.

For all the boundary conditions, I basically added ‘cyclic’ for ‘cyclic patch’ and ‘empty’ for ‘empty patch’. Am I correct to set so?

Many thanks in advance. It would be a great help if anyone of you could point out my mistakes in the input.

Thanks again.

Best regards,
Carl.

blockMeshDict
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.01;

vertices

(
(0 0 0) //Vertex 0
(-0.187132 0.451777 0) //Vertex 1
(-1.871321 4.517771 0) //Vertex 2
(0 0 1.55) //Vertex 3
(-0.187132 0.451777 1.55) //Vertex 4
(-1.871321 4.517771 1.55) //Vertex 5
(0.187132 0.451777 0) //Vertex 6
(1.871321 4.517771 0) //Vertex 7
(0.187132 0.451777 1.55) //Vertex 8
(1.871321 4.517771 1.55) //Vertex 9
(0 0 17) //Vertex 10
(-0.187132 0.451777 17) //Vertex 11
(-1.871321 4.517771 17) //Vertex 12
(-2.673044 6.453299 17) //Vertex 13
(0.187132 0.451777 17) //Vertex 14
(1.871321 4.517771 17) //Vertex 15
(2.673044 6.453299 17) //Vertex 16
(-2.673044 6.453299 1.55) //Vertex 17
(2.673044 6.453299 1.55) //Vertex 18
);

blocks

(
hex (1 0 0 6 4 3 3 8) (3 19 5) simpleGrading (1 1 1) //prism for bowl
hex (2 1 6 7 5 4 8 9) (15 19 5) simpleGrading (1 1 1) //hex for bowl
hex (4 3 3 8 11 10 10 14) (3 19 52) simpleGrading (1 1 1) //prism for main stroke
hex (5 4 8 9 12 11 14 15) (15 19 52) simpleGrading (1 1 1) //hex for main stroke inner
hex (17 5 9 18 13 12 15 16) (7 19 52) simpleGrading (1 1 1) //hex for main stroke outer
);
//hex (1 0 0 6 4 3 3 8) (10 19 11) simpleGrading (1 1 1) Martini
//hex (2 1 6 7 5 4 8 9) (20 19 11) simpleGrading (1 1 1) Martini

edges
(
arc 1 6 (0 0.489 0)
arc 2 7 (0 4.89 0)
arc 4 8 (0 0.489 1.55)
arc 5 9 (0 4.89 1.55)
arc 11 14 (0 0.489 17)
arc 12 15 (0 4.89 17)
arc 13 16 (0 6.985 17)
arc 17 18 (0 6.985 1.55)
);

patches
(
wall liner
(
(17 18 16 13)
)
wall piston
(
(0 1 6 0)
(6 7 2 1)
(2 7 9 5)
(9 18 17 5)
)
wall cylinderHead
(
(10 14 11 10)
(14 15 12 11)
(15 16 13 12)
)
cyclic cyclic
(
(0 6 8 3) //positive, prism, bowl
(6 7 9 8) //positive, hex, bowl
(3 8 14 10) //positive, prism, main stroke
(8 9 15 14) //positive, hex, main stroke inner
(9 18 16 15) //positive, hex, main stroke outer
(0 1 4 3) //negative, prism, bowl
(1 2 5 4) //negative, hex, bowl
(3 4 11 10) //negative, prism, main stroke
(4 5 12 11) //negative, hex, main stroke inner
(5 17 13 12) //negative, hex, main stroke outer
)
empty center
(
(0 3 3 0)
(3 10 10 3)
)
);

mergePatchPairs
(
);

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

boundary.org
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

5
(
piston
{
type wall;
physicalType fixedTemperatureMovingWallFunctions;
nFaces 1083;
startFace 288493;
}

liner
{
type wall;
physicalType fixedTemperatureWallFunctions;
nFaces 1957;
startFace 286536;
}

cylinderHead
{
type wall;
physicalType fixedTemperatureWallFunctions;
nFaces 893;
startFace 289576;
}

cyclic
{
type cyclic;
physicalType cyclic;
nFaces 10342;
startFace 290469;
featureCos 0.9;
}

center
{
type empty;
physicalType empty;
nFaces 0;
startFace 300811;
}
)

engineGeometry
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

engineMesh layered;

conRodLength conRodLength [ 0 1 0 0 0 0 0 ] 0.3048;

bore bore [ 0 1 0 0 0 0 0 ] 0.1397;

stroke stroke [ 0 1 0 0 0 0 0 ] 0.1524;

clearance clearance [ 0 1 0 0 0 0 0 ] 0.002;

rpm rpm [ 0 0 -1 0 0 0 0 ] 1200;


// ************************************************** *********** //


-180/p
// ************************************************** *********** //
dimensions [1 -1 -2 0 0 0 0];

internalField uniform 233000;

boundaryField
{
piston
{
type zeroGradient;
}

liner
{
type zeroGradient;
}

cylinderHead
{
type zeroGradient;
}

cyclic
{
type cyclic;
}

center
{
type empty;
}
}


// ************************************************** *********** //


controlDict:

application dieselEngineFoam;

startFrom startTime;

startTime -180;

stopAt endTime;

endTime 180;

deltaT 0.025;

writeControl runTime;

writeInterval 5;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 0.2;

maxDeltaT 1;
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Old   December 29, 2011, 15:44
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saeed divrakhsh
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I want to simulate dual fuel diesel engine with OpenFOAM. Do I simulate this with dieselEngineFoam? If not, which solver I must use?
If I can use dieselEngineFoam, can I use (CH4) mass fraction in initial condition such as O2 and N2?
I want to calculate heat release rate (j/s), but in dieselEngineFoam output, dimension of dQ is (kg/(m^3*s)). How can I calculate heat release rate (j/s)? Do I have to change code?
Thanks.
Best Regards,
Divrakhsh
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Old   August 11, 2015, 09:26
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  #26
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hi arun,
Could you please guide me?
1)When I run your enginegeometry i found compression ratio =6 .How can I change the C.R in bore*stroke=86*86 case??
2)What is the role of clearance and conRodLength ?
thanks in advance.
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