Oil Pump Transient Computation with Morphing Thomas Fischer, - - PowerPoint PPT Presentation

Simulation of a Vane-type Oil Pump

Transient Computation with Morphing Thomas Fischer, Daimler AG, Berlin Plant, ES

• Dr. Ulrich Stubbemann, Daimler AG, Berlin Plant, ES

Jan Fischer, Daimler AG, Berlin Plant, EV/T Kai Fellmann, Daimler AG, Berlin Plant, EH

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 2

Outline

• 1. Introduction
• Structure and Function of the Vane-type Pump
• Assignment for the CFD Simulation with STAR-CCM+
• 2. Construction of the Simulation Model in STAR-CCM+
• 3. Selected Results of the Simulation
• 4. Summary

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 3

Introduction

Structure and Function of the Vane-type Pump Assignment for the CFD Simulation with STAR-CCM+

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 4

Structure and Function of the Vane-type Pump

The fluid is sucked in and displaced by the change in volume of the chambers. Motions

• Rotation of the pump rotor and the vanes
• Translation of the vanes in the pump rotor
• 1. Introduction

Translation Rotation Pressure delivery side Intake side

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Pressure Pulsation of the Vane-type Pump

Assignment for the CFD Simulation with STAR-CCM+

• How high is the dynamic component stress because of the pressure

pulsation?

• Can the effect of modifying the geometry on the pulsation be assessed

without elaborate measurements?

• 1. Introduction / Assignment for the CFD Simulation

7.52 7.528 7.536 7.544 7.552 7.56

time [s]

• 2

2 4 6 8 10 12 14

p r e s s u r e [ b a r ] 1D Simulation

67.5 67.51 67.52 67.53 67.54 67.55

• 4
• 2

2 4 6 8 10 12

p r e s s u r e [ b a r ] Measure

Inlet Outlet

Graph of the pressure in a delivery chamber versus the time The pressure curve is governed by the connection of the chamber with the inlet or outlet. This pressure change is called pressure pulsation.

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 6

Cavitation Damage at the Set Collars

Assignment for the CFD Simulation with STAR-CCM+

• What mechanism causes the implosion of the gas bubbles at this

position?

• Can the effectiveness of geometrical modifications be assessed without

elaborate endurance testing?

• 1. Introduction / Assignment for the CFD Simulation

The endurance test yields cavitation damage at the set collars of the vane-type oil pump.

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Pressure Activation of the Vanes

Assignment for the CFD Simulation with STAR-CCM+

• How must the oil feed be arranged in order to obtain an optimal pressure

distribution in the interior of the rotor?

• What pressure (force) is actually applied to the undersides of the vanes?
• 1. Introduction / Assignment for the CFD Simulation

The vane must lie on the contact surface of the set collar in each

• perating state.

The vanes are therefore activated by pressure at the undersides. Pressure activation of the vanes

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 8

Construction of the Simulation Model in STAR-CCM+

Construction of the model Preparation of the simulation Sequential control

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 9

Basic Settings for the Mesh and Physical Continua

Physical continuum Segregated flow User-defined density (compressible fluid) Implicit unsteady Mesh continuum Polyhedral mesher Prism layer mesher Surface remesher

• 2. Model Construction

Geometry regions Mesh

Fixed region Morphed region Interfaces

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Definitions of the Regions and Motions in STAR-CCM+

• Splitting of the moving region into boundaries
• Assignment of the motions to the individual boundaries

Morpher: Motion Rigid motion: Rotation Incremental displacement: Table with local coordinate system

• 2. Model Construction

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Definitions of the Regions and Motions in STAR-CCM+

• The mesh quality deteriorates as the rotational angle increases.

Remeshing occurs if impermissible cells emerge.

• The boundaries are deformed.

The deformation of the boundaries is retained in the remeshing. To keep the deformation within acceptable limits, new meshes must be imported.

• 2. Model Construction

10° 18°

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Preparation of the Parametrized Surface Model in CAD

• The boundaries are generated in the CAD model
• Splitting and naming the boundaries is not required in STAR-CCM+.
• Meshes can be automatically generated with little effort for fixed positions.
• The CAD model is parameterized
• The positions of the geometry can be easily generated in the parameterized CAD model.
• 2. Model Construction

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Preparation of the Control Point Tables

• Analytical computation of the control point coordinates from the

geometry data of the pump

• Computed are tables for the translation of the vanes and the rotation of

the chamber

• The number of control points is critical; to be weighed is the geometrical

distortion compared with the CPU time for the morphing

• For the rotational range of the fluid, control points for 1° rotational angle

and 1 mm chamber depth are computed ~8300 points

• In addition for the vane displacement, one point for each vane and each

time increment

• 2. Model Construction

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Sequential Control via JavaScript

• 2. Model Construction

Start > 5 turns? < 1 turn? < 10°? Reset history End Remeshing Read prepared Mesh Morphing Simulation step Error? Yes No Yes Yes

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Motion of the Mesh

• 2. Model Construction

Assessment of the mesh quality by means of a test calculation.

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Selected Results of the Simulation

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Flow Rates in Selected Levels

• 3. Results

The area of the observed cavitation damage is characterized by a directed flow.

Section plane in the area of the observed cavitation damage

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 18

Flow Rate Distribution in the Selected Section Plane and Pressure Distribution at the Set Collar

• 3. Results

The area of the observed cavitation damage is characterized by a directed flow.

Section plane in the area of the observed cavitation damage

Simulation of a Vane-type Oil Pump | Daimler AG Berlin Plant | 20.03.2012 19

Average Pressures at Selected Surfaces Pressure Distribution

The pressures averaged at the surfaces yield the component stress due to the pressure pulsation. The pressure activation of the vanes is computationally optimized, significantly reducing the testing labor.

• 3. Results

1 2 3 4 5 6 7 8 9 10 0,00E+00 4,55E-03 9,09E-03 1,36E-02 1,82E-02 time [s] pressure [bar]

pressure pump

• utlet

pressure vane top side pressure vane bottom side pressure vane front side

T=120 °C n=3300 rpm

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Summary

• The presented procedure requires about 14 days for constructing the

CFD model and calculating an operating point.

• The coupled preparation of the meshes in the CAD system and in

STAR-CCM+, combined with the specified morpher settings, allows good mesh quality of the moving region.

• The results of the computation provide answers to the questions raised:
• The dynamic component stress due to pressure pulsation is computed as a surface integral.
• The pressure activation of the vanes is computed and optimized.
• Flow phenomena leading to cavitation damage become visible.
• Geometrical variations can be assessed computationally.
• The transient CFD computation of the pumps significantly reduces

testing labor.

• The computation was introduced as a standard in the pump

development.

• 4. Summary

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Thank you for your attention