cae-based strategies to improve reliability of variable oil pumps

1 © 2014 ANSYS, Inc. May 20, 2014 ANSYS Confidential

CAE Based Strategies to Improve Reliability of Variable Oil Pumps

Riccardo Maccherini

Pierburg Pump Technology, KSPG Automotive

Riccardo.Maccherini@it.kspg.com

Padmesh Mandloi

ANSYS

Padmesh.Mandloi@ansys.com

2 © 2014 ANSYS, Inc. May 20, 2014 ANSYS Confidential

Key Vehicle Systems Are Undergoing Drastic Changes To Reduce Carbon Footprints

Reduce Carbon Footprint

Aerodynamics

Road Resistance

Powertrain

HEV/EV Thermal

Management Energy

Leightweight

Design Energy Recovery

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Warranty Expenses Due to Increasingly Complex And Interdependent Automotive Systems

Warranty Reduction

KBI

Early introduction of quality and

reliability prediction system

Innovative manufacturing

processes

Insights into system

level interdependencies

Courtesy of Pierburg Pump Technology Italy SpA

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Pump Design Process

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Performance

Pump Characterization

Pump Optimization

Reliability

Structural Integrity

Fatigue Life Vibrational Behavior

Dynamic Behavior

Sealing Verification

Noise

Aeroacoustics Vibroacoustics

1D & 3DCFD

FEA

Multiphysics

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Variable Oil Pump - Advantage

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Reduction of the energy consumption: this is also valid for engines’

accessories!

VOP: an innovative concept of oil pump

Up to 3% CO2 saving in the

NEDC cycle

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Variable Oil Pump – Conventional Type

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• Features:

– Vane pump.

– Displacement controlled by the linear (or pivoting) movement of the control ring driven by the pressure signal.

– Continuous control of the volume of the working chamber.

– Simple design, few components.

– Pressure working directly on the volume control system.

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Variable Oil Pump – Genesis of the Product

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Customer SOR

• Oil Flow Rate Requirement • Oil Pressure Requirement • The Minimum Absorbed Energy

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Variable Oil Pump – Design Loop

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VOP design

1 2 3 4 5 6 7 8 Suggested

Shaft diameter d [mm] 10.00 10.00 10.00 10.00 10.00 12.00 12.00 10.00 >10

Max eccentricity e [mm] 3.00 3.00 3.00 3.00 3.00 2.70 2.37 3.00

Vane inside rotor i [mm] 3.60 6.00 6.00 6.00 6.00 5.00 5.34 6.00

Rotor - hub thickness s [mm] 3.00 4.00 4.00 4.00 4.00 3.70 3.70 4.00

Rotor collar max thickness p [mm] 3.10 3.00 3.00 3.00 3.00 0.30 0.64 3.00 >3,0

"Small" ring thickness b [mm] 2.50 2.50 2.50 2.50 2.50 0.30 0.64 2.50 >2,5

Vane - rotor slot f [mm] 0.50 0.30 0.30 0.30 0.30 0.30 0.64 0.30 >0,3

Rotor - control ring g [mm] 0.50 0.30 0.30 0.30 0.30 0.30 0.64 0.30 >0,3

"Small" ring - shaft n [mm] 1.00 1.80 1.80 1.80 1.80 3.70 3.70 1.80 >0,3

"Small" ring - rotor m [mm] 0.50 3.00 3.00 3.00 3.00 4.70 4.70 3.00 >0,3

Rotor external diameter dr [mm] 36.200 42.600 42.600 42.600 42.600 40.800 40.800 42.600

Control ring internal diameter da [mm] 43.200 49.200 49.200 49.200 49.200 46.800 46.800 49.200

Vane length h [mm] 10.100 12.300 12.300 12.300 12.300 10.700 10.700 12.300

Vane length outside rotor slot a [mm] 6.500 6.300 6.300 6.300 6.300 5.700 5.365 6.300

Percentage of length outside rotor slot % 64.4 51.2 51.2 51.2 51.2 53.3 50.1 51.2 <55%

"Small" ring diameter c [mm] 23.000 24.600 24.600 24.600 24.600 25.400 25.400 24.600

Ratio e/D e/D [adim] 0.0694 0.0610 0.0610 0.0610 0.0610 0.0577 0.0505 0.0610 <0,055

Required displacement C [cc/rev] 20.17 20.00 20.00 20.00 20.00 20.00 20.00 20.00

Vane number N [adim] 7 7 7 7 7 7 7 7

Vane thickness w [mm] 2 2 2 2 2 2 2 2

Max head radius for vane rmax [mm] 5.40 6.15 6.15 6.15 6.15 6.32 6.95 6.15

Max area Amax [mm2] 109.749 123.572 123.572 123.572 123.572 105.818 98.950 123.572

Min area Amin [mm2] 8.166 6.361 6.361 6.361 6.361 5.943 11.458 6.361

N*(Amax-Amin) [mm2] 711.081 820.477 820.477 820.477 820.477 699.124 612.446 820.477

Pump height 28.365 24.376 24.376 24.376 24.376 28.607 32.656 24.376

Pump height (rounded) 28.4 24.4 24.4 24.4 24.4 28.6 32.7 24.4 < 35

Delivery pressure Pd [bar] 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00

Area of vane outside rotor slot A [mm2] 184.600 153.720 153.720 153.720 153.720 163.020 175.436 153.720

Total force on vane outside rotor slot F [N] 92.30 76.86 76.86 76.86 76.86 81.51 87.72 76.86

Unit pressure on vane punit [N/mm] 3.250 3.150 3.150 3.150 3.150 2.850 2.683 3.150

---Input data

---Output data

Data - Main geometric parameters

Data - Displacement

Results - Height

H [mm]

Data & Results - Clearances

Results - Main geometric dimensions

Preliminary verifications

Optimization of the geometry best design

Best Pump!

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Variable Oil Pump - Performance

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Lumped Parameters Simulation

Equivalent hydraulic circuit build with custom & standard sub-models.

Output results: instantaneous pressure - flow - torque values in different pump areas

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Variable Oil Pump - Performance

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Output result: prediction of the cavitation

CFD Analyses

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Variable Oil Pump - Reliability

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Multi-Body Dynamic Analyses

Variable Oil Pump - Reliability

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Output results:

Exchanged Forces Components Velocity Components Accelerations

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Structural Analyses

Variable Oil Pump - Reliability

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Deformations

Stresses

Linear analyses

Non-linear analyses (contacts, material plasticity, large strain)

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Structural Analyses

Variable Oil Pump - Reliability

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Coarse Model

Sub-Model

Sub modelling (detail analyses)

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Lifetime Prediction

Variable Oil Pump - Reliability

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Real Crack

Classical theoretical approach (Goodman, Haigh, Soderberg, …)

Advanced theoretical approach (Sines, Critical plane, Dang Van, …)

Miner’s cumulative damage ratio

Virtual Crack

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Multi-axial Fatigue Analyses

Variable Oil Pump - Reliability

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The PPT F – Code Tool

Dynamic Loads

Sampling Results Data

Multi Body Simulation

Structural Analyses

Equivalency Criterion Choice

Rainflow Algorithm

Palmgren – Miner Hypothesis

Are Stress Principal Directions Varyimg?

ANSYS Plot of μ Parameter

No Yes

Life in Every Node

Proportional Fatigue?

Material Data

Import Data MatLab/SCILAB

Proportional and not proportional fatigue evaluation

Total load cycles by means of Rainflow algorithm

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Sealing Analyses

Variable Oil Pump - Reliability

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Full 3D approach

Pre-stress effects

Mesh rezoning

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Sealing Analyses

Variable Oil Pump - Reliability

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Mono-dimensional approach

“Bed” of springs

Linear or not linear springs

gasket 3D model

load – crush curve

spring elements modelling the

gasket

resulting sealing force

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Output results:

Contact pressure

Bending stress on teeth

Gear Design Optimization

Variable Oil Pump - Reliability

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Variable Oil Pump - Reliability

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Structural Resonance

Experimental/Numerical Correlation

Modal Analyses

1st Frequency

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Variable Oil Pump - Reliability

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Structural Resonance

Optimization of the pump structure

Modal Analyses

1st Frequency (New)

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Variable Oil Pump - Reliability

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FEA Dynamic Analyses

Spectrum & PSD Analyses

Transient Analyses

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Acoustic Simulations

Variable Oil Pump - Reliability

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FEM Modal Analysis Vibrational Modes

CFD Results INPUT SIGNAL

Output results

dB Sound Power Emission Type Noise Radiation

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The increased “know how” gained in different simulation areas like the FEM, CFD and MBA has allowed to run complex combined simulations. These skills gives the possibility to manage difficult situation during the product development.

fluid dynamics analysis (CFD) internal pressure peaks

dynamical analysis (MBA) contact forces crankshaft-rotor structural analysis (FEM) lifetime prediction

or

PROBLEM: crack on a VOP rotor.

Cause of the failure ?

Variable Oil Pump – Example of a Successfully Solved Problem

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weak design engine conditions

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Dynamic analysis was run in order to evaluate contact forces between crankshaft and rotor under crankshaft torsional vibration (measured directly on the engine). Clear effect of high unexpected vibration of the new engine against an existing application were highlighted.

Crankshaft mounted camera

New engine Old engine

Variable Oil Pump – Example of a Successfully Solved Problem

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26 © 2014 ANSYS, Inc. May 20, 2014 ANSYS Confidential

Calculated loads on shaft has been used to evaluate the lifetime of the component.

mesh internal stresses submodeling fatigue life

At the end of this activity it was shown that the problem was engine related (excessive crankshaft torsional vibrations).

Variable Oil Pump – Example of a Successfully Solved Problem

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Customer worked to reduce the amplitude of torsional vibrations by tuning the engine (crankshaft modifications, new damper, etc).

No re-design of the pump was necessary. No additional costs for PPT.

27 © 2014 ANSYS, Inc. May 20, 2014 ANSYS Confidential

• The present work has shown some possible numerical analyses which can be performed to design, optimize and verify a generic variable oil pump, in order to have a successful product with a reasonable cost.

• Thanks to CAE software, all of the numerical evaluations are executed without the building of any prototype, with a great economy in terms of materials and money.

• Thanks to the virtual prototyping it’s possible to explore “unusual” working loads, not reachable with experimental tests, in order to verify the pump also outside from the nominal conditions.

• Finally, it is worth noting the great flexibility of the current CAE software, like ANSYS, which permit a complete multidisciplinary approach in designing and verifying whatever mechanical component, providing reliable results in short time

Conclusions

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28 © 2014 ANSYS, Inc. May 20, 2014 ANSYS Confidential

• Simulation Driven Design and Development of a Variable Vane Pump has been presented

• ANSYS provides simulation based solutions for every aspect of pump analysis

• Concepts discussed here can be applied to all types of positive displacement and centrifugal pumps

Summary

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Thank You!