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You are here: Automotive Templates and Tutorials > Automotive Tutorials > Planetary Gearbox Tutorial > Defining Physics and Conditions

Defining Physics and Conditions

The physics and conditions are specified as follows:

Adding Modules
  1. Click Select Modules in the Model Panel. The Physical Model Selection dialog box opens.
  2. General Gear is automatically added to the Model Panel by the Rotor Template Mesher.
  3. Select Multiphase under Available Modules and click Add. Similarly, select Turbulence under Available Modules and click Add.

  4. Click Close to close the Physical Model Selection dialog box.

  

Figure 7.202 - Adding modules

 
Multiphase
  1. Select Multiphase in the Model Panel.
  2. Click two times Add Element icon for Components in the Model Tab of Properties Panel, to add components.
  3. Rename comp_1 and comp_2 as oil and air respectively.

 

 

 

 

 

 

  

Figure 7.203 - Multiphase operating parameters

 
Flow
  1. Select Flow in the Model Panel.
  2. Select Yes for Gravity Force drop-down list.
  3. Enter g = 0, -9.81, 0 m/s2 in the Gravity Force list.

 

 

 

 

 

 

  

Figure 7.204 - Flow operating parameters
General Operating Parameters
  1. Select General Gear in the Model Panel.
  2. Select Extended Mode for Setup Options.
  3. Enter Number of Revolutions and Time Steps Per Revolution to 3 and 310 respectively for the Time Definition in the
    Model Tab of Properties Panel.

  4. Enter the parameters for the Angular Velocity Definition as follows:

    • Rotational Direction: Counterclockwise

    • Rotational Speed: rpmSrpm

    • Rotational Axis Vector: 0,0,1

 

 

 

 

 

 

  

Figure 7.205 - Operating parameters
´ Note:  Provide speed and angular velocity definition parameters with respect to sun gear, as it is set as main gear.
Boundary Conditions
Gear Conditions

In this simulation, Ring gear is held stationary, speed is set as 0 rpm (rpmR) and sun gear rotates at 600 rpm (rpmS). Both of these conditions are provided using expressions.

The Speed ratio is set as zero for Gear 2, Gear 3, Gear 4, and Gear 5 in the general gear module.

The translation/rotation for planet gears (Gear 2, Gear 3, Gear 4) is provided using additional movement option in the gear module by calling user expressions written under global expression editor. Refer Global expressions for expression and speed relations.

Enter the parameters as follows:

  1. Select General Gear in the Model Panel.
  2. Select Yes for Main Gear under Gear 1 list.
  3. Enter 0 as Speed Ratio for Gear 2, Gear 3, Gear 4 and Gear 5.

  4. Enter the following parameters under Additional Movement in Gear2 list.

    1. Enter dgp1x, dgp1y, 0 m for Translation.

    2. Enter selfP rad for Additional Rotation Angle.

  5. Similarly, enter the following parameters under Additional Movement in Gear3 list.

    1. Enter dgp2x, dgp2y, 0 m for Translation.

    2. Enter selfP rad for Additional Rotation Angle.

  6. Similarly, enter the following parameters under Additional Movement in Gear4 list.

    1. Enter dgp3x, dgp3y, 0 m for Translation.

    2. Enter selfP rad for Additional Rotation Angle.

 

 

 

 

  

Figure 7.206 - General gear module parameters
  Note: The gear boundary conditions are assigned automatically by the Rotor Template Mesher.

 

Global Expression
  1. Click Edit Expression icon on the View Toolbar to open the Expression Editor dialog box.
  2. Copy and paste the expressions written under Description drop-down list for Global Expressions, see Figure 7.207.
    3. ClosedDescription

    # initial oil level

    VOFoil = (y<-0.03)? 1:0

    VOFair = 1 - VOFoil

    # sun gear total angle

    # -17.33483871

    # planet gear total angle

    # 26.869

    # ring gear total angle

    # 7.568732394

    # rotating axis

    axis = [0,0,1]

    # sun gear center

    Scenter = [0, 0, 0]

    # planet1 center

    gp1c = [-0.0441673, 0.0255, 0]

    # planet2 center

    gp2c = [0.0441673, 0.0255, 0]

    # planet3 center

    gp3c = [0, -0.051, 0]

    # S sun gear, P planetary gear, R ring gear, C carrier

    # number of teeth

    # sun gear

    zS = 31

    # planetary gear

    zP = 20

    # ring gear

    zR = 71

    # gear teeth relationship for any planetary gear system

    # zR = 2*zP + zS

    # rotation speed relationship (Willis Equation)

    # this relationship connects the rotatiton speeds of sun, planetary, ring gears and carrier

    # these two equations will be satisfied simutanously

    # reference link https://www.tec-science.com/mechanical-power-transmission/planetary-gear/willis-equation-for-planetary-gears/

    # rpmP*zP = rpmC*(zP+zS) - rpmS*zS (1)

    # rpmR*zR = rpmC*(zR+zS) - rpmS*zS (2)

    #### scenario 1####

    # rpmS is an input

    # rpmR is zero (stationary)

    ################

    # rotation speed for sun gear, conterclockwise

    rpmS = 600

    # rotation speed for carrier

    # assuming ring gear is stationary, rpmC can be derived based on relationship (2)

    rpmC = zS/(zS + zR)*rpmS

    # rotation speed for planetary gear, based on relationship (1)

    rpmP = (rpmC*(zP+zS) - rpmS*zS)/zP

    # rotation speed for ring gear, stationary ring gear

    rpmR = 0

    # for translation

    # Carrier rotation speed

    angle = rpmC*2*pi/60*time

    dgp1x = (gp1c.x*cos(angle) - gp1c.y*sin(angle)) - gp1c.x

    dgp1y= (gp1c.x*sin(angle) + gp1c.y*cos(angle)) - gp1c.y

    dgp2x = (gp2c.x*cos(angle) - gp2c.y*sin(angle)) - gp2c.x

    dgp2y= (gp2c.x*sin(angle) + gp2c.y*cos(angle)) - gp2c.y

    dgp3x = (gp3c.x*cos(angle) - gp3c.y*sin(angle)) - gp3c.x

    dgp3y= (gp3c.x*sin(angle) + gp3c.y*cos(angle)) - gp3c.y

    # for cavity volume remesh

    newx =x*cos(angle) - y*sin(angle)

    newy =x*sin(angle) + y*cos(angle)

    # self rotation angle for planetary gears

    selfP = rpmP*2*pi/60*time

    # self rotating angle for ring gear

    selfR = rpmR*2*pi/60*time

     

  3. Click OK to close the Expression Editor dialog box.

 

 

 

 

  

Figure 7.207 - Expressions
Carrier conditions
  1. Select carrier boundary surface under carrier Volume Boundaries list in the Geometric Entities Panel.
  2. Select Rotating wall under General Gear list in the Model Tab of Properties Panel.
  3. Select Yes for Power under Flow Output list.

 

 

  

Figure 7.208 - Carrier conditions
  Note: Select Yes for Power under Flow output list for the carrier, and all gear boundaries.

 

Carrier Volume condition
  1. Select carrier under Volumes in the Geometric Entities Panel.
  2. Select Volume Remesh under Volume Remesh in the Model Tab of Properties Panel.
  3. Ensure Rotation under Method dropdown list is selected.
  4. Select Both Directions for Rotational Direction.

  5. Enter rpmC rpm for Rotational Speed.

 

 

 

 

  

Figure 7.209 - Carrier volume condition

 

Cavity Volume condition
  1. Select cavity under Volumes in the Geometric Entities Panel.
  2. Select Volume Remesh under Volume Remesh in the Model Tab of Properties Panel.
  3. Select Expression under Method dropdown list.

  4. Enter newx, newy, 0 for X,Y,Z coordinates.

 

 

 

 

 

  

Figure 7.210 - Cavity volume condition

 
Fluid properties
  1. Select all Volumes in the Geometric Entities Panel.
  2. Enter the parameters for Flow Properties and Initial Condition as follows:
Component oil:
  • Density: 800 kg/m3.
  • Dynamic Viscosity: 0.0029 Pa-s

  • Surfaces Tension: 0.072 N/m

Component air:
  • Ideal Gas Law
  • Dynamic Viscosity: 1.853e-05 Pa-s
Initial Condition:
  • Initial Condition: Value as VOFoil for Component oil
  • Initial Condition: Value as VOFair for Component air

 

 

  

Figure 7.211 - Fluid properties
  Note: Select Yes for Mass Fraction, Volume Fraction, Phase Mass and Phase Volume under Component Output list for the Component oil and Component air list.

 

 

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