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sealing and two-stroke gas flow question

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Old   November 6, 2017, 10:26
Default sealing and two-stroke gas flow question
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YHY
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hyhui
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Hello everyone,
I am simulating gas flow of a two-stroke engine,and i use the "seal" option to make the scavenge port and exhaust port be sealed.

The question is below: When i start my simulation from TDC to BDC , a little gas in cylinder leak to intport and outport at the moment i start it. I guess the gap between piston and linear is too big, so i set the gap from 0.05mm to 0.01mm. But the mass of the leakage is similar. Then , i don't know how to solve this problem.
Is someone met the same question?
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Old   November 8, 2017, 11:48
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Hello,

Have you looked at a clip plane to verify that the sealing is working properly to cut off the ports from the combustion region? The attached image shows the difference between a sealed and unsealed cylinder.

Best regards,

Tristan
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File Type: jpg sealing.jpg (104.3 KB, 14 views)
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Old   November 9, 2017, 01:05
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Quote:
Originally Posted by tmburton View Post
Hello,

Have you looked at a clip plane to verify that the sealing is working properly to cut off the ports from the combustion region? The attached image shows the difference between a sealed and unsealed cylinder.

Best regards,

Tristan
hello tmburton,
i have cut the clip plane in the attached file, the seal is normal, but there are some high temperature gas in the ports. the red color represent the temp. I don't know how the high temperature come to the ports after sealing.
Attached Images
File Type: png WWBJ]T1{YPQ{1_{X]$$[6HH.png (17.0 KB, 10 views)
File Type: png C`@60M}L7{RG1A8E@@B6J]3.png (2.1 KB, 11 views)
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Old   November 9, 2017, 13:33
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Hello,

Ok, it's a region assignment problem. The cells near the port seals are getting assigned to the cylinder region instead of the appropriate port region, and they're getting initialized with the conditions of the cylinder. Can you try switching the region assignment for the piston skirt and the liner to 'Dependent'?

Best regards,

Tristan
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Old   November 10, 2017, 09:09
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Quote:
Originally Posted by tmburton View Post
Hello,

Ok, it's a region assignment problem. The cells near the port seals are getting assigned to the cylinder region instead of the appropriate port region, and they're getting initialized with the conditions of the cylinder. Can you try switching the region assignment for the piston skirt and the liner to 'Dependent'?

Best regards,

Tristan
Hello tmburton,
Thanks for your help, i switch the piston skirt ,liner, and ring into 'dependent', it works at the begining. But there comes to an WARNING: "flow is occuring between regions which are not geometrically connected. This indicates that the cell resolution in this area is not sufficient to resolve all regions. Flows output in regions_flow.out may not balance" , when the port open. Finally, it aborted with the message:
stuck in an infinite loop trying to initialize region_id for cells, cell count is 4
stuck in an infinite loop trying to initialize region_id for cells, cell count is 4
stuck in an infinite loop trying to initialize region_id for cells, cell count is 2
stuck in an infinite loop trying to initialize region_id for cells, cell count is 2
internal error: stream numbers do not match;
Can you tell me what should i do for it ?
Thank you very much!
Sincerely.
YHY
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Old   November 13, 2017, 01:43
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Quote:
Originally Posted by tmburton View Post
Hello,

Ok, it's a region assignment problem. The cells near the port seals are getting assigned to the cylinder region instead of the appropriate port region, and they're getting initialized with the conditions of the cylinder. Can you try switching the region assignment for the piston skirt and the liner to 'Dependent'?

Best regards,

Tristan
Hello tmburton,

I haven't find the way to solve it yet.
Can you help me again? Thank you very much!

Sincerely!
hyhui
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Old   November 13, 2017, 11:45
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Hello,

Have you checked your surface file in Studio to make sure that the triangles are assigned to the correct boundary group and that the boundary groups are assigned to the appropriate region? One thing that can help is to check the Group color by regions box in the View Options dock and make sure that everything looks ok as you turn the boundary groups in the different regions on and off.

Best regards,

Tristan
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Old   November 14, 2017, 09:44
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Quote:
Originally Posted by tmburton View Post
Hello,

Have you checked your surface file in Studio to make sure that the triangles are assigned to the correct boundary group and that the boundary groups are assigned to the appropriate region? One thing that can help is to check the Group color by regions box in the View Options dock and make sure that everything looks ok as you turn the boundary groups in the different regions on and off.

Best regards,

Tristan
Hello tmburton,
Thanks for your patient help!
I may have solved the problem, when i encryption the grid around the port, it also have the warning above, but it can finish normally.

Sincerely!
hyhui
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