Hi @Kai_himself,
Just to add on to what was mentioned by Vinícius. If you refer to the figure below you will notice that you basically have a broken mesh based on the very high illegal cell count. This is what is causing your simulation error.
From the same mesh’s meshing log, you will also notice that your layers are not showing up as Vinícius has mentioned.
This post here should help you with regards to layer generation.
The issue with illegal cells seems to be with the geometry. Your pipe has a gap between the inner and outer surface along with the hollow cap that is interfering with the inner and outer pipe surface. The presence of this coupled with the sharp edges along with the high refinement levels all equate to the very high illegal cell count you encountered. Do refer below.
A good way to mitigate this issue would be to either create a simple pipe assembly with just one inner surface and a cap with no thickness or to close the gaps within the geometry (for the cap and the pipe itself) by filling in the gaps.
Cheers.
Regards,
Barry