Building the Mesh

This section describes the step-by-step procedure for preparing the mesh for the rolling piston compressor with valve. The Rolling Piston Template is used to create the rotor chamber mesh and the Valve Template Mesher is used to create the valve mesh.

Rolling Piston Mesh Select Rotor Template Mesher in the Mesh Panel. Select Rolling Piston from Rotor Type drop-down list. Select CAD Surfaces rotor_chamber_wall in the Geometric Entities Panel and click Add Surfaces icon for Chamber Wall in the Properties Panel. Select CAD Surfaces rotor_vane_tip in the Geometric Entities Panel and click Add Surfaces icon for Vane Tip. Enter the parameters as follows: Rotor Mesh Size: Coarse Rotational Axis Vector: 0,0,1 Chamber Center: 0,0,0 Chamber Radius: 0.024 m Rotor Radius: 0.02 m Rotor Leakage Gap: 1e-05 m Vane Tip Gap: 1e-05 m Click Build Rolling Piston Mesh. A new mesh rollingpiston is created under Built Meshes in the Geometric Entities Panel. The meshed volume rollingpiston is generated under Volumes.

Figure 17.112 - Rolling piston mesh settings

 

Valve Select Valve Template Mesher in the Mesh Panel. Select Circumferential Valve from Valve Type drop-down list in the Geometric Entities Panel . Select CAD Surfaces valve_valve in the Geometric Entities Panel and click Add Surfaces icon for Valve Surfaces in the Properties Panel. Similarly, select CAD Surfaces valve_bottom, valve_cylinder_in, valve_cylinder_out, valve_top and click Add Surfaces icon for Cylinder Surfaces Select CAD Surfaces valve_end and valve_mgi_port. Click Add Surfaces icon for Valve End Surfaces in the Properties Panel. Enter the parameters as follows. Center of Rotation: -0.0181899, 0.022586, 0 Rotational Axis Vector: 0,0,1 Reference Point: -0.012,0.0275,0.01 Minimum Gap Size: 0.0005 m Maximum Displacement: 0.005 m Deform Zone Layers: 5 Enter Maximum Cell Size as 0.02, Minimum Cell Size as 0.001 and Cell Size on Surfaces as 0.02 in the Properties Panel. Click Build Circumferential Valve Mesh. The new mesh circumferential valve is created under Built Meshes in the Geometric Entities Panel. The meshed volume circumferential valve is generated under Volumes.

Figure 17.113 - Circumferential valve mesh settings

 

Inlet, Outlet and Port Select General Mesher in the Mesh Panel. Select CAD Surfaces inlet_inlet, inlet_mgi_rotor, inlet_wall, outlet_mgi_valve, outlet_outlet, outlet_wall, port_wall, port _mgi_rotor and port _mgi_valve in the Geometric Entities Panel. Click Add Surfaces icon for CAD Surfaces in the Properties Panel. Enter Maximum Cell Size as 0.005, Minimum Cell Size as 0.001 and Cell Size on Surfaces as 0.005 in the Properties Panel. Click Create Mesh. A new mesh mesh is created under Built Meshes in the Geometric Entities Panel. The meshed volumes inlet, outlet and port are generated under Volumes.

Figure 17.114 - Inlet, outlet and port mesh settings

 

The meshes created for the fluid domain are shown below.

Figure 17.115 - Rolling Piston mesh

Figure 17.116 - Valve mesh

Figure 17.117 - Inlet, outlet and port mesh

 

Create interfaces

In this section, the Mismatched Grid Interfaces (MGIs) are generated between boundaries.

The steps to create the MGIs are shown below:

1. In Geometric Entities Panel > Volumes > Boundaries, select Boundaries as shown in Table 17.11.
2. Click Connect Selected Boundaries via MGI icon to create the MGI entities. Refer, Figure 17.118.

A group display of entities can be viewed using the Group Entities by Volumes/Types icon at Geometric Entities Panel toolbar.

Connecting interfaces	Boundaries	Entity
Inlet, rolling piston chamber and port	inlet_mgi_rotor, chamber_wall and port_mgi_rotor	MGI03
Port and circumferential valve	port_mgi_valve and valve_mgi_port	MGI04
Circumferential valve and outlet	valve_cylinder_out and outlet_mgi_valve	MGI05

Table 17.11 - Creating interfaces

The new entities are created under MGI in Volumes, refer Figure 17.119. MGI01 and MGI02 are created automatically by the Rolling Piston Template.

Figure 17.118 - Connecting interfaces

Figure 17.119 - Created interfaces

 

Note: If MGIs are created by connecting the wrong boundaries, delete the created MGIs by clicking on Delete Selected Geometric Entity icon and then recreate the MGIs.