how to module the internal combustion engine and analysis by using the ansys workbench?
Ohhh boy,straight to the deep end. First of all how much experience do you have with CFD software? Second, are we talking 2D analysis or 3D (i really hope its 2D..) , third-what sort of analysis are you required to do thermal/mechanical etc.
Your starting point is always the model, or domain if you are analysing gas within the engine,then the meshing,then the setup and analysis. I suggest having a browse through http://www.cfd-online.com/ you will find most of the specific answers to your questions once you start setting up the models and meshing.