[jacksonkelly]

Hello everyone. I intend to make cfd analysis of internal combustion engine and I'm at the begining. I'm sketching geometry with solidworks then i'm going to import it to ansys.
My question is; when sketching geometry , is it necessary to make empty inside cylinder,port,etc...

[Mack]

Hi Kamil,

If you are planning to use the Ansys ICE tool, then you need to keep all solid volumes (I mean, do not subtract the empty spaces inside the engine, or the valves using the function "cavity" on solidworks).
However, if you are going to use fluent straight (I am saying this because Ansys ICE only sets the case, but uses Fluent to solve it), then you do need to subtract the valves just. But do not worry about this now, as you can correct it latter on ICEM.
Just one tip: if you want to simulate an engine with moving mesh, I would recommend you not using Fluent/Ansys, once their mesh movement is based on "sliding", what creates hanging nodes and spoils the convergence.
Nevertheless, if your simulation will be done with a "frozen" geometry (like a "flow bench type simulation"), then this solver performs nicely.

Regards
Mack

[jacksonkelly]

Hi Mack. Thanks for your reply.

I want to modelling the air flow and fuel injection in si engine without reaction and simulate it with moving mesh. This is my finishing thesis. Actually i have a ready mesh file but my advisor doesn't let me to use this file.
I looked for tutorial about modelling and meshing engine geometry but i couldn't find it anywhere.

So i'm trying to modelling geometry but i don't know how to do that
Should i draw complete cylinder or only cylinder head , valves and ports ?
In my firstime i sketched complete geometry without cavities but when i tried to mesh it i couldn't select the valves surface.

By the way sorry about if there is a misspelling. My english is not good enough

[Mack]

Hi Kamil,

I am not an expert on Ansys ICE, but I am sure you need to upload a solid geometry, I mean: intake and exhaust ports, chamber and valves. The chamber will be limited by the cylinder head and the piston shape. You do need to model all of them if you want to get accurate results.
In my case, as soon as I realized that Ansys ICE just sets up the case on fluent, then I went straight to fluent and meshed my engine on ICEM.
I would suggest you to switch to another code (as you are in the beginning), such as AVL Fire, Star CD, Ricardo Vectis... once they are designed almost exclusively for ICE. Fluent/Ansys, as I said, perform very well for non-moving meshes, but when you have a moving frame than you will need to produce hanging nodes (to allow the movement of the valves).
You can check on youtube this video:
http://www.youtube.com/watch?v=MDaN4I1DPKI
Around 30s you will see a jet getting into the combustion chamber, and if you pause the footage you will realize that this jet is not continuous (red above the valve and yellow inside the chamber). It happens because the approach used by Ansys/fluent is based on a interface between tetra and hexa mesh, affecting the conservation of momentum and mass.
As you are a student (like me), try to get any other of the software I mentioned above, it will probably save you time.
It took me 5 months of my research to realize it, and now I am using AVL Fire

Regards,
Mack

[biond8]

Hi ! I’m simulating a full engine cycle with ansys ICE but I have problems with the decomposition because of valve body/ valve seat. It says “check valve seat again “ but it doesn’t say why..the error is “there should be non-manifold body”. Do you have an example of working geometry? Just to see what is wrong in mine ! Thanks
berardina2006@msn.com