Learning Forum

[JASON.HOOKER]

Hello, 

I'm currently making a full engine cycle model on ansys forte, i have done all the geometry prep for it however when i'm specifying the boundires for the model i am having issues with the engine valves. 

The issue i am having is that when i specify the valves as a moving boundary they do not appear in the geometry display window and the valve motion does not show in the boundary motion tab when you preview the models motions. 

further to this when i select seat the valve it doesnt do anything other than make the geometry i had change drematically. 

Can somebody help me with this? I'm not sure what i am doing wrong so anything would be appreicated. 

Thanks, 

Jason 

[jcooper]

Hi Jason:

It is hard to say why the valves are not showing up.  Typically valve are "seated" describing the valve surface and the surface it contacts, however.  A description of this process is below.  I would suggest that you find a Forte tutorial that is similar to your application and follow it to see where your setup deviates from it.

*****************************'

In boundary conditions where wall motion is activated, the user has three options for the movement
sub-type:
• Moving Surface: Used for the piston
• Valve: As the name indicates, this is used for valves
• Sliding Interface: Used in ported engine cases where the piston covers/uncovers port openings to the cyl-
inder
For the Valve movement sub-type, the user needs to specify the valve seat and the surface it contacts.
The valve seat is the stationary portion that may be a part of the head or intake/exhaust port surface
and the surface it contacts is the valve itself.
In this case, some portions of the intake port (similarly for the exhaust port) have been split off and
labeled as the “seat”. This splitting is not a requirement, but has been done in this case to help with
the calculation speed of the valve opening/closing events (see Notes in the Valves section above). The
splitting is accomplished with a cut plane in the Geometry tree.
Select both the “seat” portion and the “valve” from the list by holding down the Ctrl key and clicking
with the left mouse to multi-select.
Now that the Valve movement subtype surfaces have been selected, you need to specify the Valve
Motion Activation Threshold, that is, the minimum gap before the valve is considered open or closed.
It is suggested to start with a 0.5 mm gap in the first simulation, and then you can use a smaller gap
if you are not satisfied with the results. The other required input is the Approximate Cells in the Gap
at Minimum Lift and this should be 2. Note that Forte automatically refine the valve gap down to 1/16
refinement, so no special refinements are required to for resolving the gap.

This Forte overview may also be helpful:

https://www.youtube.com/watch?v=cXUs8t-yh-Q

 

Best Regards,

 

Judy