Computational domain

This section explains the preparation of surfaces to create the domain.

The pre-requirement in a bent axis piston pump simulation is the preparation of CAD Surfaces, for a virtual neutral position of the pump in which the cylinder remains in the “neutral” position. If a neutral geometry is not available, this must be done in CAD by rotating the ports, valve plate, and a single cylinder around the joint of the bent axis (Bent Center) until the Cylinder Block Axis Vector aligns with the Flange Axis Vector, and then adjusting the piston position (and volume of the cylinder) by rotating around the center of the ball joint (as determined in PumpLinx by the Flange Center and Flange Center to Ball Joint Radius) until it fits within the cylinder.

This tutorial is performed with a neutral geometry, in which the cylinders are rotated to incorporate the bend of the axis. The surfaces are then split, combined and renamed to prepare the computational domain.

Pump Surfaces

Select Split/Combine Geometry or Grid in the Mesh Panel.
Select CAD Surfaces pump in the Geometric Entities Panel.
Select Split Disconnected from the Operation drop-down list in the Properties Panel, click Split Disconnected. Eight new CAD Surfaces are created in the Geometric Entities Panel.
Rename CAD Surfaces pump_01, pump_02 and pump_03 as inlet, outlet and piston respectively.
Select the remaining CAD Surfaces and select Combine from the Operation drop-down list in the Properties Panel, click Combine
Rename the combined CAD Surfaces as vp.

Figure 6.480 - Split of CAD surfaces

Inlet Surfaces

Select CAD Surfaces inlet in the Geometric Entities Panel.
Select Split by Angle from the Operation drop-down list in the Properties Panel.
Enter 75 deg for Angle, click Split by Angle. Three new CAD Surfaces are created in the Geometric Entities Panel.
Rename CAD Surfaces inlet_01, inlet_02 and inlet_03 as inlet_walls, inlet_inlet and inlet_mgi respectively .

Figure 6.481 - Inlet surfaces

Outlet Surfaces

Select CAD Surfaces outlet in the Geometric Entities Panel.
Select Split by Angle from the Operation drop-down list in the Properties Panel.
Enter 75 deg for Angle, click Split by Angle. Three new CAD Surfaces are created in the Geometric Entities Panel.
Rename CAD Surfaces outlet_01, outlet_02, and outlet_03 as outlet_walls, outlet_outlet and outlet_mgi respectively .

Figure 6.482 - Outlet surfaces

Piston Surfaces

Select CAD Surfaces piston in the Geometric Entities Panel.
Select Split by Angle from the Operation drop-down list in the Properties Panel.
Enter 75 deg for Angle, click Split by Angle. Six new CAD Surfaces are created in the Geometric Entities Panel.
Rename CAD Surfaces piston_01 and piston_05 as piston_cylinder and piston_mgi respectively.
Select CAD Surfaces piston_02, piston_06. Select Combine from the Operation drop-down list in the Properties Panel, click Combine and rename as piston_wall. Similarly select the CAD Surfaces piston_03, piston_04. Click Combine and rename as piston_cap.

Figure 6.483 - Piston surfaces

Valve Plate Surfaces

Select CAD Surfaces vp in the Geometric Entities Panel.
Select Split by Angle from the Operation drop-down list in the Properties Panel.
Enter 50 deg for Angle, 16 for Maximum No. of Splits and click Split by Angle. Sixteen new CAD Surfaces are created along with vp in the Geometric Entities Panel.
Select CAD Surfaces as shown in Table 6.22. Select Combine from the Operation drop-down list in the Properties Panel.
Click Combine and rename with corresponding names as shown in Table 6.22.

Figure 6.484 - Valve plate surfaces

CAD Surfaces	Rename as
vp, vp_01, vp_02, vp_03, vp_04, vp_05, vp_16	vp_walls
vp_06,vp_07, vp_10, vp_11, vp_12	vp_mgi_pistons
vp_08, vp_09, vp_13, vp_14, vp_15	vp_mgi_ports

Table 6.22 - Combine CAD surfaces

´	Note: Splitting of the surfaces can also be done by mouse selection using the Split by Mouse option from the Method drop-down list in the Geometry Tab of Properties Panel.