Two-Stroke Engine: CAD Bodies and Faces

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

CAD Bodies

For a two-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 the wetted surface of each piston-controlled intake, exhaust, or burner port.
  • For uniflow scavenging designs, one CAD body for each exhaust valve. Simcenter STAR-CCM+ In-cylinder allows a maximum of 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.
  • For uniflow scavenging designs, the exhaust valves must be at their closed position.

Example of a uniflow two-stroke engine:





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 for a two-stroke engine using the example of the uniflow two-stroke engine:

CAD Body



(only for uniflow designs)

Filter: CAD Body Name Contains engine

exhaust

AND

valve

AND

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

NOT

engine

AND NOT

valve
CAD Body Name Examples engine-fluid exhaust-valve 1 intake-plenum
Engine Part Cylinder Exhaust Valve 1 Plenum

CAD Faces

For the cylinder, the piston-controlled ports, and the exhaust valve, 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
  • liner
  • piston
CAD Face Name Example
  • cylinder liner
  • cylinder piston
Cylinder Part Surface
  • Liner
  • Piston
CAD Face

(only for uniflow designs)

(only for uniflow designs)

Filter: CAD Face Name Contains exhaust

AND

port

AND NOT

outlet

  • outlet
  • unnamed
CAD Face Name Example
  • exhaust-port
  • exhaust-port outlet
  • -
Cylinder Part Surface
  • Exhaust Port
  • Outlet
  • Default : Gases
Exhaust Valve [n] (only for uniflow designs)
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
Plenum
CAD Face



Filter: CAD Face Name Contains inlet

OR

outlet

 unnamed
CAD Face Name Example intake-plenum inlet

or

exhaust-plenum outlet

 -
Plenum Part Surface Inlet

OR

Outlet

 Default : Gases 2