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Operating Parameters

The operating parameters pertaining to the Rolling Piston template involve the time definition for the simulation, compressor (pump) configuration and angular velocity definitions for rotation (see, Figure 6.682).

 

 

 

 

Figure 6.682 - Rolling piston model-Operating parameters

Time Definition

 This provides the following ways to specify the size and number of time steps for the Rolling Piston simulation (see Figure 6.682):

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

• Number of Revolutions: The number of revolutions to be simulated.
• Time Steps Per Revolution: The number of time steps taken to move rotor one complete revolution.

The magnitude of the time-step size (s) and the angle of rotation (deg) depend on the Time Steps Per Revolution.

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

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Pockets: A method of Time Definition, the parameters required under the Time Definition of Pockets are:

• Number of Pockets: It is similar to the number of revolutions. The number of revolutions decides the simulation time.
• Time Steps Per Revolution: The number of time steps taken to move rotor one complete revolution. The magnitude of the time step size (s) and the angle of rotation (deg) depend on the Time Steps Per Revolution.

Total Time Steps: Total number of time steps for a given simulation. The parameter required under Total Time Steps is:

• Time Steps Per Revolution

• Number of Time Steps (in the Simulation Panel)

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

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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 the Time Definition in the Model Tab of 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 Rolling Piston must be set as the Reference Pump for the Time Definition option to be displayed.

Compressor (Pump) Configuration

This contains the parameters pertaining to the geometry of the rolling piston (see, Figure 6.682). The inputs such as Chamber Center, Chamber Radius, Rotor Radius, Rotor Leakage Gap and Vane Tip Gap are same as those defined in the Mesher.

Angular Velocity Definition

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

The Rotational Direction is specified as Clockwise or Counterclockwise relative to the Axis Vector, using the convention that a positive clockwise rotation is based on the vantage point with the Axis Vector pointing at an observer. Rotational Speed (given in rpm) denotes the speed of Rolling Piston rotation.

 

 

 

 

Figure 6.683 - Angular velocity definition

Note: The magnitude of the Rotational Speed is specified relative to the stationary (lab) frame of reference in terms of rpm, even for example, when applied to the boundary of a non-inertial reference frame. The Rotational Speed only accepts a positive value, unless the Rotational Direction is set to Both Directions. Actually it follows the right-hand thumb rule with the thumb aligned with the axis vector.

Configuration

The type of configuration is selected during meshing, which is displayed in Blueand cannot be changed in the Properties Panel.

Cluster Method

This method controls the axial distribution in the rotor and chamber wall 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 rotor and chamber wall 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.