Four-Stroke Engine: CAD Bodies and Faces

For the setup of a four-stroke engine, the CAD bodies and faces of the engine geometry must meet certain criteria.

CAD Bodies

For a four-stroke engine, Simcenter STAR-CCM+ In-cylinder requires the following CAD bodies:

  • One CAD body for the wetted surface of a single cylinder.
  • One CAD body for each solid valve. Simcenter STAR-CCM+ In-cylinder allows a maximum of three intake valves and four exhaust valves.
  • One CAD body for the wetted surface of each additional plenum that is attached to the engine (optional).

The following alignment and orientation of the cylinder and valve geometries are required:

  • The cylinder must be positioned so that the piston motion is along the z-axis, with the compression stroke moving the piston in the positive z-direction.
  • The x and y coordinates of the cylinder centre must be at x=0, y=0.
  • The firedeck z coordinate must be at z=0.
  • The piston must be at the TDC position.
  • All valves must be at their closed position.




To enable Simcenter STAR-CCM+ In-cylinder to recognize the engine bodies, you must name the bodies prior to CAD import in a certain manner. Simcenter STAR-CCM+ In-cylinder uses name-based Object Filters that assign the bodies to the respective Engine Parts, automatically. The following table displays the filters and the associated Engine Parts for the CAD bodies that you import:

CAD Body





Filter: CAD Body Name Contains
  • engine

intake

AND

valve

AND

a number (1, 2, or 3)

exhaust

AND

valve

AND

a number (1, 2, 3, or 4)

CAD Body Name Examples
  • engine-fluid
  • intake-valve 1
  • intake-valve 2
  • exhaust-valve 1
  • exhaust-valve 2
Engine Part
  • Cylinder
  • Intake Valve 1
  • Intake Valve 2
  • Exhaust Valve 1
  • Exhaust Valve 2

CAD Faces

For the cylinder wetted surface and the valves, you must name certain faces prior to CAD import. Simcenter STAR-CCM+ In-cylinder uses the face names to assign the faces to the respective Engine Part Surfaces. The default Simcenter STAR-CCM+ In-cylinder filters work as follows:

Cylinder
CAD Face







Filter: CAD Face Name Contains intake

AND

port

AND NOT

inlet

exhaust

AND

port

AND NOT

outlet

  • inlet
  • outlet
CAD Face Name Example
  • intake-port
  • exhaust-port
  • intake-port inlet
  • exhaust-port outlet
Cylinder Part Surface
  • Intake Port
  • Exhaust Port
  • Inlet
  • Outlet
CAD Face





Filter: CAD Face Name Contains
  • liner
  • piston
  • unnamed
CAD Face Name Example
  • cylinder liner
  • cylinder piston
  • -
Cylinder Part Surface
  • Liner
  • Piston
  • Default : Gases
Intake Valve [n]
CAD Face



(for valves with a margin)





Filter: CAD Face Name Contains

intake

AND

valve

AND

head

AND

a number (1, 2, or 3)

intake

AND

valve

AND NOT

head

AND NOT

face

AND

a number (1, 2, or 3)

intake

AND

valve

AND

face

AND

a number (1, 2, or 3)

intake

AND

valve

AND

stem

AND

a number (1, 2, or 3)

  • unnamed
CAD Face Name Example
  • intake-valve 1 head
  • intake-valve 1 margin
  • intake-valve 1 face
  • intake-valve 1 stem
  • -
Intake Valve Part Surface
  • Head
  • [CAD face name]
  • Face
  • Stem
  • Default : Solids
Exhaust Valve [n]
CAD Face



(for valves with a margin)





Filter: CAD Face Name Contains

exhaust

AND

valve

AND

head

AND

a number (1, 2, 3, or 4)

exhaust

AND

valve

AND NOT

head

AND NOT

face

AND

a number (1, 2, 3, or 4)

exhaust

AND

valve

AND

face

AND

a number (1, 2, 3, or 4)

exhaust

AND

valve

AND

stem

AND

a number (1, 2, 3, or 4)

  • unnamed
CAD Face Name Example
  • exhaust-valve 1 head
  • exhaust-valve 1 margin
  • exhaust-valve 1 face
  • exhaust-valve 1 stem
  • -
Exhaust Valve Part Surface
  • Head
  • [CAD face name]
  • Face
  • Stem
  • Default : Solids