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Operating Parameters

The operating parameters pertaining to the Crescent template involve the time definition for the simulation, pump configuration, angular velocity definitions for pump rotation and other advanced/extended settings (see, Figure 6.314).

 

 

 

 

Figure 6.314 - Crescent model-Operating parameters

Time Definition

This provides the following ways to specify the size and number of time steps for the crescent pump simulation (see Figure 6.314).

1. Revolutions: A single revolution corresponds to a pump rotation of 360 degrees. The parameters required under this Time Definition are:

• Number of Revolutions: The number of pump revolutions to be simulated.
• Time Steps Per Inner Tooth Rotation: The number of time steps taken to move the inner tooth through one pocket (angle between the tips of two inner rotor teeth).

The magnitude of the time-step size (s) and the angle of rotation (deg) depend on the Time Steps Per Inner Tooth Rotation and the Number of Inner Teeth as follows:

	6.27
	6.28

For a Time Definition of Revolutions, the Number of Time Steps is computed as follows:

6.29

Pockets:A method of Time Definition that uses the angle from one inner tooth to the next to determine the size and number of time steps. A single pocket corresponds to a rotation equal to the average angle between blades, based on 360 degrees divided by the user specified Number of Inner Teeth. The parameters specified under this Time Definition are:

• Number of Pockets: The amount of rotation based on the angle between two inner teeth.
• Time Steps Per Inner Tooth Rotation


 

 

 

 

Figure 6.315 - Pocket-Crescent

For a Time Definition of Pockets, the Number of Time Steps is computed as follows:

6.30

 

Note: The number of pockets corresponds to the number of inner teeth.

Total Time Steps:Total number of time steps for a given simulation. The following parameters are specified for this Time Definition:

• Time Steps Per Inner Tooth Rotation
• Number of Time Steps (in the Simulation Panel)

For a Time Definition of Total Time Steps, the Simulation Time (Duration) is computed as follows:

6.31

 

Note: If the Number of Time Steps is displayed in Blue, it means that it is set and controlled elsewhere and cannot be changed in the Simulation Panel. The setting of Time Definition in the Properties Panel and in the Simulation Panel are slaved to each other, such that changing the value in one panel, changes the value in the other. If multiple templates are active, the Crescentmodule must be set as the Reference Pumpfor the Time Definition option to be displayed.

Pump Configuration

This contains parameters pertaining to the geometry of the crescent pump (Figure 6.314). The inputs such as Number of Inner Teeth, Number of Outer Teeth, Inner Rotor Center and Outer Rotor Center are same as those defined in the mesher.

• Inner Rotor Shrinkage (%): Enables to shrink the inner rotor size in terms of percentage. This is used to see the effects of increased tip clearance. Figure 6.316 shows an example of shrinking the inner rotor size by 10%. Negative values of Inner Rotor Shrinkage (%) are specified to increase the size of the inner rotor.

Note: The Inner Rotor Shrinkage (%) can be specified only once after opening Simerics-MP+. Once a non-zero value has been set, the program must be closed and reopened before any new value will take effect. For example, setting Inner Rotor Shrinkage (%) to 10%, starting a simulation, stopping the simulation, resetting Inner Rotor Shrinkage (%) to 0, and then restarting from Initial Conditions will not restore the inner rotor to its original size.

Figure 6.316 - Inner rotor shrinkage (%)

Figure 6.317 - Outer rotor enlargement (%)

• Outer Rotor Enlargement (%): Enables to enlarge the outer rotor in terms of percentage. This is used to see the effects of increased tip clearance. Figure 6.317 shows an example of enlarging the outer rotor by to 10%. Negative values of Outer Rotor Enlargement(%) can be specified to decrease the size of the outer rotor.

Note: The Outer Rotor Enlargement(%) can be specified only once after opening Simerics-MP+.Once a non-zero value has been set, the program must be closed and reopened before any new value will take effect. For example, setting Outer Rotor Enlargement(%) to 10%, starting a simulation, stopping the simulation, resetting Outer Rotor Enlargement(%) to 0, and then restarting from initial conditions will not restore the outer rotor to its original size.

Angular Velocity Definition

This contains parameters pertaining to the rotation of the pump. The parameters defined under the Angular Velocity Definition are: Rotational Direction, Rotational Speed and Rotational Axis Vector (see Figure 6.314).

Cluster Method

This method controls the axial distribution in the inner and outer rotor using the following methods:

• Original Distribution gives a uniform cell spacing.
• Symmetric Clustering(1-2) stretches the mesh towards or away from the top and bottom of the inner rotor and outer rotor in the axial direction depending on the value entered for Cluster Mesh in Axial Direction(1-2). The values entered must be between 1.0 and 2.0.

 

Keep Corner Points If this parameter is set to Yes, it snaps the mesh nodes to the original coordinates of the teeth corner points so that no clipping occurs, and the teeth keep their shape. It is set to No by default. The Corner Point Angle is used to control the angle between the tangent vector at the corner point and the vector to an adjacent corner point. If Keep Corner Points is set to Yes, the option Corner Point Angle appears with a default value of 30.

Figure 6.320 -  Keep corner points

 

The other parameters Mesh Center (0 Inner, 1 Outer) and Gear Deformation are the same as defined in the crescent mesher.