converge compression ratio

liuadam67 · July 4, 2017, 18:25

why when I want to move the piston toward compression ratio the piston moves very ridiculous, by the way, I already make the cylinder close

MFGT · July 5, 2017, 02:36

Please define "ridiculous".

Do you have specified the correct piston moving direction?

liuadam67 · July 5, 2017, 06:52

I have set the piston move as z direction, ridiculous means that when it moves it will over the head or go down a lot. the compress ratio is always stuck in 3 my target compression ratio is set at 10, do I need to set the TDC first and if so how can I set the TDC position.
many thanks

MFGT · July 5, 2017, 07:55

The Piston has to be in BDC position, while the Valves are in closed position.
The minimum Lift (0.2 or 0.1 mm) causes a slightly higher compression ratio as originally defined in CAD.

Do you have selected the correct boundaries that form the combustion chamber?

liuadam67 · July 5, 2017, 08:57

I think I have set the correct boundary, but the compression ratio is still only 3 I don't know why, have you meet this kind problem before?

MFGT · July 5, 2017, 10:26

No, i never had this problem.
Do you have correct units for bore and stroke in the engine.in file?

Blanco · July 5, 2017, 10:46

I would also suggesto to check che model dimension: try to measure the cylinder diameter to double check you're working with your desired units

liuadam67 · July 5, 2017, 11:09

after I check the diameter it works, thank you guys, many thanks

July 4, 2017, 18:25	converge compression ratio	#1
liuadam67 New Member xinkai liu Join Date: Jun 2017 Posts: 5 Rep Power: 8	why when I want to move the piston toward compression ratio the piston moves very ridiculous, by the way, I already make the cylinder close

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July 5, 2017, 02:36		#2
MFGT Senior Member Tobias Join Date: May 2016 Location: Germany Posts: 264 Rep Power: 10	Please define "ridiculous". Do you have specified the correct piston moving direction?

July 5, 2017, 06:52		#3
liuadam67 New Member xinkai liu Join Date: Jun 2017 Posts: 5 Rep Power: 8	I have set the piston move as z direction, ridiculous means that when it moves it will over the head or go down a lot. the compress ratio is always stuck in 3 my target compression ratio is set at 10, do I need to set the TDC first and if so how can I set the TDC position. many thanks

July 5, 2017, 07:55		#4
MFGT Senior Member Tobias Join Date: May 2016 Location: Germany Posts: 264 Rep Power: 10	The Piston has to be in BDC position, while the Valves are in closed position. The minimum Lift (0.2 or 0.1 mm) causes a slightly higher compression ratio as originally defined in CAD. Do you have selected the correct boundaries that form the combustion chamber?

July 5, 2017, 08:57		#5
liuadam67 New Member xinkai liu Join Date: Jun 2017 Posts: 5 Rep Power: 8	I think I have set the correct boundary, but the compression ratio is still only 3 I don't know why, have you meet this kind problem before?

July 5, 2017, 10:26		#6
MFGT Senior Member Tobias Join Date: May 2016 Location: Germany Posts: 264 Rep Power: 10	No, i never had this problem. Do you have correct units for bore and stroke in the engine.in file?

July 5, 2017, 10:46		#7
Blanco Senior Member Blanco Join Date: Mar 2009 Location: Torino, Italy Posts: 193 Rep Power: 17	I would also suggesto to check che model dimension: try to measure the cylinder diameter to double check you're working with your desired units

July 5, 2017, 11:09		#8
liuadam67 New Member xinkai liu Join Date: Jun 2017 Posts: 5 Rep Power: 8	after I check the diameter it works, thank you guys, many thanks