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Temperature extrapolation error CI engine

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Old   May 23, 2022, 08:27
Default Temperature extrapolation error CI engine
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Hello,
I have modified a bit the inputs of the example: Heavy_Duty/Engine_sector_SAGE_DMS_transient_RANS

the modifications I did is changed
Bore to 0.46m
Stroke to 0.58m and
Connecting rod length to 1.2m
Crank speed to 500 rpm
As I simulate a marine engine.

I receive the following error:
(Rank 11) WARNING: [ 365] it = 490, it_out = 422, extrapolating on the temperature calculation.
(Rank 11) WARNING: [3467] Temperature extrapolation error found at cell 11 located at cell 185, located at <0.0380171, -0.00674593, -0.0206378>, in region 0, whose level=7, ii=194, jj=187, kk=240



I have increased the grid size and also increased iterations but they seem not to solve the issue.
Could you suggest something ?

Thank you
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Old   May 26, 2022, 17:44
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Praveen Srikanth
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Hi,

Did you change the geometry as well when you changed those parameters? Depending on how you changed the geometry in the example case, there could be a lot of reasons for this temperature extrapolation error.

Praveen
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Old   May 27, 2022, 02:44
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Hello again,
I scaled by a factor of 3.4 the geometry and increased the mass of fuel injected by the same factor.

The only modifications after that were the engine.in file for Bore, Stroke and rod length.
(Also relaxed the tolerance and max iterations for energy and pressure eq.)

When I do these, I receive this kind of error.
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Old   May 27, 2022, 17:41
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Praveen Srikanth
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Hi,

Do these errors show up right from the start or do they show up close to TDC or close to an event? You could try to run a case with check_grid_motion_flag = 1 to make sure the changes you made to engine.in and the geometry are valid before running a case.

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Old   May 28, 2022, 06:42
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Hello again,
The initial case I import is the heavy duty diesel engine sector SAGE.
I scaled the entire surface by a factor of 3.4 as I want to simulate larger bore and stroke.

1) When I run the case with check_grid_motion_flag = 1 I get several temperature extrapolation errors after 24%.

2) When I run the case regularly, (I scale mass of fuel injected, the injector diameter, relax timesteps, increase pressure eq. iterations) I receive the errors attached.

Do you think it is a mesh issue or where should I focus ?
Thanks
Attached Images
File Type: jpg issue (2).jpg (41.5 KB, 9 views)
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Old   June 1, 2022, 18:20
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I think by scaling and using the engine.in parameters you mentioned, you might run into intersection issues when the piston reaches close to TDC. You can verify this by running with check_grid_motion_flag set to 2. Alternatively, you could look at the cylinder volume in thermo.out to see if the volume at TDC looks acceptable.

If you are still having issues with this case, feel free to contact the support team at support@convergecfd.com (or your existing support contact) with your case setup and someone can look into this. Please use your official email for all correspondence with Convergent Science.
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