multi-body engine simulation including …/file/151007_7_m meuter_avl...multi-body engine simulation...

TriboDays - 07.10.2015 Matthias Meuter

MULTI-BODY ENGINE SIMULATION INCLUDING NON-CONFORMAL LUBRICATED CONJUNCTIONS


AVL – GLOBAL PARTNER FOR THE AUTOMOTIVE INDUSTRY

Engineering

Simulation Tools

Test Systems

Passenger

Cars

Racing2-Wheelers

Construction Commercial

Vehicle

Agriculture

Locomotive Power PlantsMarine


AVL – GLOBAL PARTNER FOR THE AUTOMOTIVE INDUSTRY

Simulation Tools

Simulation software tools for powertrain

development

Structural Dynamics and Acoustics

CFD and Combustion&Emission

Powertrain System Simulation


Valvetrain – Functionality

• Controls Gas Exchange in Combustion Chamber• In: Air/Fuel Out: Exhaust Gas


Task

• Goal: Engine simulation including flexible body motion and oil lubricated contacts– Include conformal (e.g. journal bearings) and non-conformal contacts

(e.g. CAM contact)

• Combine Elastohydrodynamic Lubrication pressure calculation (EHL) with multibody simulation

• Integrate EHL module in multibody simulation software AVL EXCITE


Multibody Dynamics – Body State

Global Position Vector:



Number of Nodes:

Global Position Vector:



Body State Vector:

Node i

Node States:


Multibody Dynamics – Equation System

Node i

Advanced Equation of Motion:



Node i


e.g. Drive Torque



Node i


Unknown coupling forces


Multibody Dynamics – Joint Equation

• Describes physical coupling of Bodies




𝐹𝐸𝑥𝑡




• Calculates Joint forces acting on Bodies (Force Coupling)

𝐹𝐸𝑥𝑡





• Calculated with relative displacements and velocities

𝐹𝐸𝑥𝑡






𝐹𝐸𝑥𝑡

Unknown Joint Forces:- Have to be iterated until equation system is satisfied






𝐹𝐸𝑥𝑡


- EHL pressure has to be calculated for set positions






𝐹𝐸𝑥𝑡


- EHL pressure has to be calculated for set positions

- Differs from a common approach in EHL simulation where the force is used as an input


Valvetrain – Functionality

• Controls Gas Exchange in Combustion Chamber• In: Air/Fuel Out: Exhaust Gas


EHL – Contact Plane

Contact SurfaceContact Surface

Flat Follower Roller Follower



𝑅1

𝑅2

Contact

Body 1:

Body 2:

𝑅1, 𝐸1, 𝜗1

𝑅2, 𝐸2, 𝜗2

Contact Radii: 𝑅1,2, Elastic Moduli: 𝐸1,2, Poisson’s Ratios: 𝜗1,2


EHL - Reduced Model

Joint Force Calculation:

1

𝑅′ =1

𝑅1+

1

𝑅21

𝐸′ =1

2

1 − 𝜗12

𝐸1+1 − 𝜗2

2

𝐸2


EHL - Reduced Model

Joint Force Calculation:

2b

R

Line Contact in axial direction:

1

𝑅′ =1

𝑅1+

1

𝑅21

𝐸′ =1

2

1 − 𝜗12

𝐸1+1 − 𝜗2

2

𝐸2


EHL - Joint Equation

𝑝ℎ 𝑥 = 𝐹(ℎ, 𝑈)

Hydrodynamic Pressure Elastic Deformation

ℎ 𝑥 = 𝐹(𝑝)


EHL - Joint Equation

Hydrodynamic Pressure Elastic Deformation

Reynolds Equation Film Thickness Equation


Multibody Dynamics – EHL Inclusion

Solve Reynolds

ℎ0,R’,U

Equilibrium EHL

ℎ𝑗(𝑝𝑗)

𝑝𝑗+1( 𝑝𝑗)

𝑗 = 0

Initial (Hertz) Pressure ( )

Solve Film Thickness

Residual: 𝑝𝑗 − 𝑝𝑗

𝑝0

Iteration Control

𝑝𝑗 (ℎ𝑗)

𝑗 = 𝑗 + 1

N

Solve Bodies

𝐹𝐽𝑜𝑖𝑛𝑡

Y


Test Simulation

Elastic Properties:

𝐸1 𝐶𝑎𝑚 = 1.7𝐺𝑃𝑎

𝐸2(𝑇𝑎𝑝𝑝𝑒𝑡) = 2.1𝐺𝑃𝑎

Poiseuille Ratio: 𝜗 = 0.3

Oil Properties:

Dyn. Viscosity: 𝜂 = 6 𝑚𝑃𝑎 ∙ 𝑠

Roelands viscosity model: 𝛼 = 10𝑚𝑚²

𝑁

Simulation Properties:

Engine Speed: 3000 rpm

Simulation Interval: 0-720° Crank Angle -> 0-360° Cam Angle


Results – Force


Results – Gap Distribution


Outlook

• Integration of non-conformal hydrodynamic contacts in MBD is possible:

– Simulation results are comparable to the results obtained with the Hertzian theory

– Pressure distribution and clearance height can be analyzed in detail

• Simulation including EHL is challenging. ‒ Smaller time steps

• Further testing and comparison with measurements is needed


Outlook

• Integration of non-conformal hydrodynamic contacts in MBD is possible

– Simulation results are comparable to the results obtained with the Hertzian theory

– Pressure distribution and clearance height can be analyzed in detail

• Simulation including EHL is challenging ‒ Smaller time steps are needed‒ Code performance needs to be optimized

• Further testing and comparison with measurements are needed

Thank you for your attention.

multi-body engine simulation including …/file/151007_7_m meuter_avl...multi-body engine simulation...

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