Gear chamber Meshing

This section explains the settings for the gear chamber mesh generated using the Rotor Template Mesher. This involves selection of the surfaces, directional characteristics of the mesh and other advanced mesh settings.

The parameters related to External Gear meshing can be accessed by setting the Setup Options to Advanced Mode, as shown in Figure 6.138.

Figure 6.138 - Gear template mesher

Drive Gear

This is used to assign the drive gear as follows:

Select the drive gear surface under CAD Surfaces in the Geometric Entities Panel.
Click Add Surfaces icon to the right of Drive Gear, or click Select Drive Gear in the Properties Panel.

Drive Gear Outer Boundary

This is used to assign the portion of the boundary that surrounds the drive gear (shown in Figure 6.139) as follows:

Select the drive gear outer surface under CAD Surfaces in the Geometric Entities Panel.
Click Add Surfaces icon to the right of Drive Gear Outer Boundary, or click Select Drive Gear Outer Boundary in the Properties Panel.

Slave Gear

This is used to assign the slave gear as follows:

Select the slave gear surface under CAD Surfaces in the Geometric Entities Panel.
Click Add Surfaces icon to the right of Slave Gear, or click Select Slave Gear in the Properties Panel.

Slave Gear Outer Boundary

This is used to assign the portion of the boundary that surrounds the slave gear (shown in Figure 6.139) as follows:

Select the slave gear outer surface under CAD Surfaces in the Geometric Entities Panel.
Click Add Surfaces icon to the right of Slave Gear Outer Boundary, or click Select Slave Gear Outer Boundary in the Properties Panel.

Figure 6.139 - Drive and slave gear boundaries

Note:

Simerics-MP+ automatically cycles from one operation to the next in the sequence: Select Drive Gear, Select Drive Gear Outer Boundary, Select Slave Gear, Select Slave Gear Outer Boundary to Build Gear Mesh. For the Build Gear Mesh option to be available, the external gear surfaces must first be assigned.
The picking sequence can be repeated/reset in the event that a boundary is incorrectly identified or a new mesh is desired.
The boundary conditions are automatically set by the template for the assigned surfaces.

Rotor Mesh Size

This allows to control the resolution of the mesh created in the external gear pumping chamber as:

Coarse
Normal
Fine
User Input

Figure 6.140 - Rotor mesh size-Gear

Figure 6.141 - Gear mesh sizes

The control parameters associated with User Input (see, Figure 6.140) are:

Points in Rotational Direction: Corresponds to the number of cell nodes in the rotational direction along the circumference of the pumping chamber. The number of control cells in this direction is (Points in Rotational Direction – 1).
Points in Radial Direction: Corresponds to the number of cell nodes in the radial direction from the center to the edge of the pumping chamber. The number of control cells in this direction is (Points in Radial Direction – 1).
Points in Axial Direction: Corresponds to the number of cell nodes in the axial direction from the bottom to the top of the pumping chamber. The number of control cells in this direction is (Points in Axial Direction – 1).

Figure 6.142 - User input mesh size-Gear

Drive Gear Rotational Axis Vector: Specify the direction of the axis of rotation of the drive gear in the laboratory reference frame, in coordinates.

Figure 6.143 - Rotational axis vector- Gear

Drive Gear Center:

Specify the center of rotation of the drive gear in coordinates.

Slave Gear Center:

Specify the center of rotation of the slave gear in coordinates.

Figure 6.144 - Drive and Slave gear

Note:

The Drive Gear Center and Slave Gear Center must be set very precisely when accounting for tight clearances.
Although the Drive Gear Centerand Slave Gear Center do not affect the mesh generation, these are typically specified during the meshing operation and then automatically copied over to the Pump Configuration menu.

Feature Angle

This is an angle between CAD Surfaces segments. It is used to preserve the geometrical features by remembering certain CAD point segment ends, so that corners on the gear teeth are not truncated. This parameter is set to a default value of 20 degrees, and has an allowable input range between 3 and 45 degrees.

Low values of the Feature Angle cause the grid to conform to the CAD Surfaces more closely than higher values, but the grid is less smooth internally.
High values of the Feature Angle cause the grid to conform to the CAD Surfaces less closely than lower values, but the grid is more smooth internally.

Figure 6.145 - Gear-Feature angle