[balav94]

Hi,

I am currently working on SI Engine simulations using Converge CFD. For this purpose, I have a new geometry and I followed all the steps in the link below concerning compression ratio calculations. I also sealed the gaps between the valves and the openings on the head part of the geometry. However, after sealing the gaps using disconnect triangles, when I try to move the Piston based on the target compression ratio, the target compression ratio fails to change.

I am also getting a pop-up screen which asks me to make sure that I include the newly created disconnect triangles in the geometry for compression ratio calculations. But, I have already included the disconnect triangles in my geometry selection.

So, I feel that I am doing something wrong here. Can anyone help?

[MFGT]

Hi,

in Studio v2.3 or later you dont need to create disconnect triangles.
Just specify the boundaries belonging to the cylinder region and the moving piston boundary and you should be ready to go.

[balav94]

Hi MFGT,

Thank you for the reply.

Are you saying that creation of disconnect triangles is optional from Converge v2.3 onwards or the creation shouldn't be done at all?

Also, why am I receiving the warning message which asks me to make sure that I include the patches corresponding to disconnect triangles?

Is that warning or the creation of disconnect triangles the reason why I am unable to move the piston based on target compression ratio?

It would be great if you can clarify the above questions.

Thanks in advance!

[MFGT]

I think its optional, however i have never done that.

If you pick an SI example case and mark the region0 boundaries as well as the piston boundary, it should work. So you just have to set it up the same way.

I could imagine thats the reason for your problem.

[balav94]

Thanks again for the reply. I will try this in a day and get back to you. Hopefully it should work.

[balav94]

Hi MFGT,

Sorry for the late update. I tried this today and it worked out. I had one more question.

If I want to create valve events, how do I go about doing it?

I mean, the example SI Engine case has intake and outlet valve lift profiles. However, for my experimental data, I don't have the valve lift profiles to define the moving wall boundary conditions at valve location.

I just have the crank angles during which the valve opening and closing events occur. In such a situation, I am using the fixed wall BC at the valve locations (since CONVERGE CFD automatically activates/de-activates the disconnect triangles according to the valve events). Is this a good way to go about doing it?

Or, do I need to use the "piston motion" option in Moving Wall BC, which will move the valves based on piston motion? But, is it correct to connect the valve motion to the piston motion?

It would be great if you can help. Thanks in advance!

[tmburton]

Bala,

You will need a valve lift profile (as a start, you can always use one from one of our sample cases if and modify it to get the right duration and maximum valve lift, but that would just be to get a working case setup) to correctly specify the valve motion and get good results. Also, for valve events, CONVERGE will choose the time to connect and disconnect the regions based on the time where the valve lift value reaches half of the specified minimum lift.

Best regards,

Tristan