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Vane chamber meshing

This section explains the settings for the vane 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 Vane meshing can be accessed by setting the Setup Options to Advanced Mode, as shown in Figure 6.195.

 

 

 

 

Figure 6.195 - Vane template mesher

Rotor

This is used to assign the rotor of the vane pump as follows:

• Select the rotor surface under CAD Surfaces in the Geometric Entities Panel.
• Click Add Surfaces icon to the right of Rotor, or click Select Rotor in the Properties Panel.

The selected CAD Surfaces corresponding to the rotor do not have to be cylindrical. If the selected CAD Surfaces are within 1% of the ideal cylinder defined by the parameters Rotor Center, Rotational Axis Vector, and Rotor Radius, the selected rotor will be adjusted to be perfectly cylindrical.

Note: Identification of the vanes is not needed for grid generation because the vanes are generated by extrusion of the points where they attach to the rotors.

Chamber Wall

This is used to assign the chamber wall of the vane pump as follows:

• Select the chamber wall surface under CAD Surfaces in the Geometric Entities Panel.
• Click Add Surfaces icon to the right of Chamber Wall, or click Select Chamber Wall in the Properties Panel.

The selected CAD Surface corresponding to the Chamber Wall does not have to be cylindrical. If the selected CAD Surface is within 1% of the ideal cylinder defined by the parameters Chamber Center, Rotational Axis Vector, and Chamber Radius, the selected Chamber Wall will be adjusted to be perfectly cylindrical.

Rotor Mesh Size This allows to control the resolution of the mesh created in the vane pumping chamber as: Coarse Normal Fine User Input

Figure 6.196 - Rotor mesh size-Vane

The control parameters associated with User Input (see Figure 6.196) 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). The default value of Points in Rotation Direction is automatically rounded up to give a whole number of cells between blades. 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). The default value of Points in Radial Direction is 16. 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). Points on Each Vane Tip: Corresponds to the number of cell nodes in the circumferential direction between the vane tips and the pumping Chamber Wall. The number of control cells in this direction is (Points on Each Vane Tip – 1). The minimum number of points on vane tip is 2 and the default is 3. The Points on Each Vane Tip are a subset of the total number of points in Rotation Direction.   Warning: Attempting to generate a mesh with Points on Each Vane Tip larger than the Points in Rotation Direction, will cause the mesher to crash. Points in Tip Gap: Corresponds to the number of cell nodes in the radial direction between the vane tips and the pumping Chamber Wall. The number of control cells in this direction is Points in Tip Gap – 1. The minimum number is 2 and the maximum number is (Points in Radial Direction – 1). The default value is 2. The Points in Tip Gap are a subset of the total number of Points in Radial Direction.   Warning: Attempting to generate a mesh with Points in Tip Gap = or > Points in Radial Direction will cause the mesher to crash.

Figure 6.198 - User input - Vane     Figure 6.199 - Points on tip vane and Gaps

Design Type The configuration of the pump is specified by the Design Type option as (see, Figure 6.200): Balanced: A balanced vane pump has a Chamber Wall that has a fixed lobed geometry, thereby balancing the load on the rotor (see Figure 6.192). Fixed Displacement: The displacement of the pump is fixed, such that no lateral movement occurs between the Chamber Wall and the Rotor. Variable Displacement: A variable displacement vane pump (VDVP) has a Chamber Wall that either translates or rotates, thereby changing the pump’s eccentricity and the resulting displacement. Slider Type: Allows the selection of the type of Variable Displacement pump to be simulated. There are two types of displacements in the vane pump, they are (see Figure 6.201): Translation: This parameter is selected to enable the simulation of a Variable Displacement pump for which the chamber wall translates, thereby changing the pump’s eccentricity and the resulting displacement (see Figure 6.202). Rotation: This parameter is selected to enable the simulation of a Variable Displacement pump for which the chamber wall rotates, thereby changing the pump’s eccentricity and the resulting displacement (see, Figure 6.203).   Note:   For VDVP translation, the chamber wall is linked to a Translation Dynamics (Translation (1 DOF)) module to simulate a dynamics-controlled variable displacement vane pump. For VDVP rotation, the chamber wall is linked to a Rotation Dynamics (Rotation (1 DOF)) module to simulate a dynamics-controlled variable displacement vane pump.

Figure 6.200 - Design type-Vane       Figure 6.201 - Slider type - Vane

Figure 6.202 - Translating VDVP

Figure 6.203 - Rotating VDVP

 

Physical Parameters of the Vane Pump

The physical parameters of the vane pump that govern the working of the vane pump are described below as follows:

 

 

 

 

Figure 6.204 - Vane pump physical parameters

Number of Vanes

This parameter corresponds to the number of vanes in the pump and it is typically specified during the meshing operation, but it is not required for meshing. Its primary function is to control the time-steps in the template module

The Number of Vanes has no effect on the geometry but this parameter is used in conjunction with the Time Steps Per Vane Rotation to determine the number of degrees the vanes are rotated every time-step.

	6.20
	6.21

Rotational Axis Vector The direction of the axis of rotation of the rotor in the laboratory reference frame, specified in coordinates.

Figure 6.205 - Rotational axis vector- Vane

Rotor Center

This parameter is used in conjunction with the Rotational Axis Vector and Rotor Radius in the Vane Pump Template to generate the mesh and during simulation. This must be set very precisely if tight tolerances (e.g. Tip Clearances) are to be modelled (see, Figure 6.204).

The Rotor Center input can be used in combination with the Rotational Axis Vector and Rotor Radius to perfect a circular Rotor boundary. If the CAD Surface is within 1% of the cylinder defined by the above parameters, the points on the rotor boundary created during the meshing operation are adjusted to precisely conform to the cylinder.

• If the cylindrical boundary generated using the Rotor Radius, Rotational Axis Vector and Rotor Center above does not match the corresponding CAD Surface to within 1% of the radius (as in the case of an elliptical housing), the shape of the CAD Surface is used instead.
• If the above parameters qualify for perfection of the rotor during meshing, this modification applied directly to the rotor boundary and stored in the .sgrd.

Chamber Center

This parameter is used in conjunction with Rotational Axis Vector and Chamber Radius to perfect a circular Chamber Wall. If the CAD Surface is within 1% of the cylinder defined by the above parameters, the points on the Chamber Wall boundary created during the meshing operation are adjusted to precisely conform to the cylinder (see Figure 6.204). Specify the Chamber Center in coordinates option under Rotor Type.

• If the cylindrical boundary generated using the Chamber Radius, Rotational Axis Vector and Chamber Center above do not match the corresponding CAD Surface to within 1% of the radius (as in the case of an elliptical housing), the shape of the CAD Surface is used instead.
• If the above parameters qualify for perfection of the Chamber Wall during meshing, this modification is applied directly to the chamber wall boundary and is stored in the .sgrd file.

Note: Chamber Center is offered as a Vane Mesher Parameter when the Design Type is Variable Displacement or Fixed Displacement. For Balanced, the Chamber Center is computed based on the Chamber Wall’s CAD Surface.

Pin Center

This parameter is a meshing parameter only available when the Design Type is Variable Displacement with Rotation. It is the rotational center of the Chamber Wall

Specify the Pin Center in coordinates option under Rotor Type. If specified during the meshing operation, it is passed over to the Pin Center parameter under the Pump Configuration in the Vane Module (see, Figure 6.203).

Slider Rotation: This represents the angle (in degrees) by which the Chamber Wall rotates about the Pin Center for a rotating Variable Displacement pump (see, Figure 6.203).

Slider Displacement: This represents the displacement (in meters) by which the Chamber Wall translates for a translating Variable Displacement pump (see, Figure 6.202).

Sliding Direction: This represents the direction in which the Chamber Wall translates for a translating Variable Displacement pump (see, Figure 6.202).

Vane Angle (-90 ~+90) The angle between the vanes and the radial direction. The direction of a positive Vane Angle is determined by the right-hand rule with the Rotational Axis Vector. This is an optional parameter specified under the Rotor Template Mesher the Mesh Panel and implemented in the Geometry Tab. It is an Advanced Mode option. If not set by the user, it is assumed to be 0 deg. Specify the angle of the vane in terms of degrees in the Vane Angle option.

Figure 6.206 - Vane angle

Note: After creation of the numerical mesh, the Vane Angle can still be modified before or during a simulation using the Vane Angle option in the Model Tab, after selecting the Vane module in the Model Panel. The slant of the blades (positive vs. negative) is based on the right-hand rule relative to the Rotational Axis Vector.

Vane Tip Gap This parameter is used to set the physical tip clearance during the creation of the numerical mesh. When generating the mesh, this clearance can range from zero to the minimum clearance between the Chamber Wall and the rotor. Specify the Vane Tip Gap in terms of a positive real number under the Rotor Type. A non-zero value of the Vane Tip Gap must be specified during the Rotor Template Mesher in the Geometry Tab of the Properties Panel, if a tip clearance is to be included in the model. It may subsequently be modified as a Pump Configuration parameter under the Vane Pump module in the Model Tab. Once created, this gap can be adjusted later using the Vane Tip Gap parameter. The clearance can range from greater than zero (zero is not allowed) up to the minimum clearance between the Chamber Wall and the Rotor. The grid distribution in the Vane Tip Gap can be controlled as an advanced User Input, using the parameters Points on each Tip Vane and Points in Tip Gap.

Figure 6.207 - Zero clearance at the vane tip gap

Note: The Vane Tip Gap shown under the Pump Configuration in the Model Tab of the Properties Panel and under Rotor Type in the Geometry Tab of the Properties Panel are not linked and can have different values.

 

Note: If a zero value of the Vane Tip Gap is specified during the Rotor Template Mesher operation, no mesh is included in tip clearance and cannot be adjusted during operation.

Rotor Radius

This is an optional parameter that can be used in conjunction with the Rotational Axis Vector and the Rotor Center to generate the circular inner boundary of the mesh created inside the vane pump chamber. Specify the radius of the rotor in terms of a positive real number during the Rotor Template Mesher operation in the Geometry Tab of Properties Panel

If the CAD Surface is within 1% of the cylinder defined by the above parameters, the points on the rotor boundary created during the meshing operation are adjusted to precisely conform to the cylinder.

• If the cylindrical boundary generated using the Rotor Radius, Rotational Axis Vector and Rotor Center above does not match the corresponding CAD Surface to within 1% of the radius (as in the case of an elliptical housing), the shape of the CAD Surface is used instead.
• If the above parameters qualify for perfection of the Rotor during meshing, this modification is applied directly to the Rotor boundary and is stored in the .sgrd file.

Chamber Radius

This specifies the radius of the chamber in terms of a positive real number in the Chamber Radius option under the Rotor Type. This input under the Rotor Template Mesher can be used in combination with Rotational Axis Vector and Chamber Center to perfect a circular Chamber Wall. If the CAD Surface is within 1% of the cylinder defined by the above parameters, the points on the Chamber Wall boundary created during the meshing operation are adjusted to precisely conform to the cylinder.

• If the cylindrical boundary generated using the Chamber Radius, Rotational Axis Vector and Chamber Center above does not match the corresponding CAD Surface to within 1% of the radius (as in the case of an elliptical housing), the shape of the CAD Surface is used instead.
• If the above parameters qualify for perfection of the Chamber Wall during meshing, this modification is applied directly to the Chamber Wall boundary and is stored in the .sgrd file.

Curved Rotor in Axial Direction

Specify this option as Yes or No. The two possibilities of this option are:

• Setting this option to Yes will create the rotor volume inner surface mesh for the rotor hub that coheres to the CAD Surface curvature. This enables modelling hubs that have curvature or angles in the axial direction.
• Setting this option to No will create a straight hub whether the corresponding hub mesh is curved or straight.

Note: Curved Rotor in Axial Direction should only be used if the hub is curved or angled along the axial direction.

Keep Tip Profile

Specify this option as Yes or No. This option is typically specified during the meshing operation and automatically copied over to the Vane Template model menu parameters.

If Yes is selected for Keep Tip Profile, select an appropriate CAD Surface or Boundary which is used for the Vane Tip surface shape and remains unchanged during the motion of the Vanes.

Note: Keep Tip Profile is only available in Extended Mode and is activated or deactivated in the Geometry Tab of the Properties Panel.