optimization studies of engine friction...total engine friction, strip-down test. optimization...

M.Sc. Oleg Krecker, PhD candidate, BMWB.Eng. Christoph Hiltner, Master’s student, Affiliation BMW

OPTIMIZATION STUDIES OF ENGINE FRICTIONEUROPEAN GT CONFERENCE FRANKFURT/MAIN, OCTOBER 8TH, 2018

Optimization Studies of Engine Friction | Oleg Krecker | October 8th 2018 Slide 2

AGENDA

Motivation and objective1

Improvements on preliminary results2

Friction reduction studies with GT-SUITE’s Integrated Design Optimizer 3

Conclusion and further developments4

MOTIVATION


Thermal engine model

1D Simulation warm up & fuel consumption within driving cycles

Test

Warm up

0 200 400 600 800 1000 12000

50

100

150

Zeit [s]

TH

_Z

ST

_1

_2

_0

5 [°C

]

m.TH_ZST_1_2_05

Tem

pera

ture

[°C]

Time [s]

Cylinder Liner Temperature, NEDC

Simulationdata

Final result:

Impact on CO2 - emissions

Corre

latio

n &

valid

atio

n

Predictive evaluation of concepts and trends in engine friction reduction„As simple as possible and as complex as necessary“

other losses

mech. power

Piston assembly

Crank-shaft

Oil + vacuum

Belt driveCylinder head+ chain drive

Measurement data (motored and fired)

Fric

tion

Speed

pump

Friction

Low

Total engine

fired

1-cylinder fired(floating liner)

Total engine / strip-down

Single components motored

Transient cycles

Low High

Real boundary conditions

Data resolution &reproducibility

High

Measured

Pred

icte

d

0D/1D Friction Simulation Total engine

GT-SUITE

Crucial formodel calibration

0D/1D Friction SimulationOBJECTIVE


Low

Total enginefired

1-cylinder fired(floating liner)

Total engine / strip-down

Single components motored

Transient cycles

Low High

Closeness of basic conditions to reality

Possible measuring resolution & reproducibility

High

Fast prediction

Agile transferability

Relative comparison

Physical evaluation

Requ

irem

ents

Validation Calibration OptimizationFriction

Advanced parameter analysis using GT-SUITE Integrated Design Optimizer (IDO)

Systems


AGENDA





PRELIMINARY RESULTSTOTAL ENGINE FRICTION, STRIP-DOWN TEST


Total Engine Test Rig Transmission Oil- & Vacuum – Pump Water pumpAcc. Belt Drive Inlet Camshaft + ValvetrainExhaust Camshaft + ValvetrainBalancer Shaft Piston SkirtPiston RingsSmall End BearingBig End Bearing Main Bearings Seals

Sim

ulat

ion

Expe

ri-m

ent

Strip-Down Test, 90°C

1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

Necessary model improvements:

Fric

tion

dist

ribut

ion:

pr

evio

us m

odel

ass

umpt

ion

� Buildup� Parameter

identification� Validation

� Further investigation on model parameters

� Validation of single camshaft friction

� Parameter identification

� Extend measurements for validation

Gap due to:− Missing simulation of chain friction.− Non-validated belt drive friction model.− Inaccuracies between single state strip-down

measurements, total engine friction behavior and its equivalent simulation.

PRELIMINARY RESULTSTOTAL ENGINE FRICTION, STRIP-DOWN TEST


Total Engine Test Rig Transmission Oil- & Vacuum – Pump Water pumpAcc. Belt Drive Inlet Camshaft + ValvetrainExhaust Camshaft + ValvetrainBalancer Shaft Piston SkirtPiston RingsSmall End BearingBig End Bearing Main Bearings Seals

Sim

ulat

ion

Expe

ri-m

ent


1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

Gap due to:− Missing simulation of chain friction.− Non-validated belt drive friction model.− Inaccuracies between single state strip-down

measurements, total engine friction behavior and its equivalent simulation.


Fric

tion

dist

ribut

ion:

pr

evio

us m

odel

ass

umpt

ion

� Buildup� Parameter

identification� Validation

� Further investigation on model parameters

� Validation of single camshaft friction

� Parameter identification

� Extend measurements for validation

0 1000 2000 3000 4000 5000

Camshaft + valvetrain frictionTorque

transducer

CHAIN DRIVE FRICTION MODEL


Validation Method

In chain-guide/sprocket contacts:- Friction coefficient guides- Friction coefficient sprocketsIn chain links: - Longitudinal damping- Torsional damping

Main friction/power loss parameters

Modelling

Strip-Down states Single component motored

Torquetransducer

Feasible magnitude and slope of chain drive power loss.

Inaccuracies due to missing system interdependency (e.g. chain tensioner dynamics).

Speed [rpm]

Pow

er lo

ssch

ain

drive

[W

]IDO Calibration

subtract subtract

Torquetransducer

0 1000 2000 3000 4000 5000 6000

FEAD FRICTION MODEL


Validation MethodModelling

Single component motored

In belt-pulley contacts:- Friction coefficient- Contact damping In belt properties: - Bending stiffness- Shearing stiffness- Longitudinal damping

Main friction/power loss parameters

Friction torque of each accessory

Speed [rpm]

Pow

er lo

ssFE

AD [W

]

IDO Calibration Feasible magnitude FEAD power loss.

Inaccuracies due to missing system interdependency (e.g. accessory roller bearing).

CURRENT RESULTSTOTAL ENGINE FRICTION, STRIP-DOWN TEST



Buildup Parameter

identification Validation

Parameter identification

Extend measurements for validation

CURRENT RESULTSTOTAL ENGINE FRICTION, STRIP-DOWN TEST



1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

Total engine, measuredRemaining components, measuredMain components, simulated

Acc. Belt Drive Chain DriveCylinder Head UnitPiston AssemblyBalancer Shaft Crankshaft


Buildup Parameter

identification Validation

Parameter identification

Extend measurements for validation

1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

1000 2000 3000 4000Speed [rpm]

Fric

tion

Torq

ue [N

m]

Cylin

der H

ead

+Ch

ain

Bala

ncer

Sha

ftCr

anks

haft

Test Rig Transmission Oil- & Vacuum – Pump Water pump

- Correlation of measurement and simulation has been improved. - Single component friction simulation shows feasible agreement

to measured data. - Note: magnitude and trend of single component friction has to be

questioned critically if compared to total engine friction losses.


AGENDA





0 2000 4000 6000

GT-SUITE INTEGRATED DESIGN OPTIMIZERSETTINGS FOR FEAD MODEL


Variables forcalibration

i = 15

Variables forpower loss reduction

i = 7

Search algorithm Genetic, NSGA-III

Population size 50

Number of generations 10


i = 7

1st loop 2nd loop Example parameters:LuGre friction coefficient, belt damping coefficient, belt-pulley connection damping ratio, …

Example parameters:LuGre friction coefficient, belt damping coefficient, belt shear stiffness, belt axial stiffness, …

0

1

2

3

4

0 300 600

Design [-]

Obj

ectiv

e fu

nctio

n [W

]*10

5

0

200

400

600

800

1000

0 300 600

Design [-]

Obj

ectiv

e fu

nctio

n [W

]

Speed [rpm]

Pow

er lo

ss [W

]

(*)

(*hypothetical, no-constraint study)

0 2000 4000 6000

Speed [rpm]

Pow

er lo

ss [W

]

Best design Base design TargetCalibrated design

Calibrated design

No-constraint design

Constraintdesign

VARIATION STUDIESFEAD FRICTION MODEL


0 1000 2000 3000 4000 5000 6000

meas., 222N meas., 316N

sim., 222N sim., 316N

Speed [rpm]

Pow

er lo

ssFE

AD [

W]

0 1000 2000 3000 4000 5000 6000

meas., 222N meas., 217N, 2nd Layout

sim., 222N sim., 217N, 2nd Layout

Speed [rpm]

Pow

er lo

ssFE

AD [

W]

Belt pre-tension Belt layout

Higher pre-tension leads to more power losses. Good correlation in mid to high speed ranges. Further investigation on low speed power losses necessary.

Less power losses by removing a pulley and changing the belt layout (e.g. remove water pump in case it is electrically driven).

Good correlation in mid to high speed ranges. Further investigation on low speed power losses necessary.

0 1000 2000 3000 4000 5000 6000

OPTIMIZATION STUDIESFEAD FRICTION MODEL


Speed [rpm]

Pow

er lo

ssFE

AD [

W] - 80%

power loss

FEAD power loss minimization

Idea

Resu

ltsCr

itica

lco

nclu

sion

Inner belt power dissipation is determined by the belt material properties. Soft belt (less axial stiffness, less shear stiffness) might decrease power losses.

Parameter comparison base design vs. best design:1. Axial stiffness & LuGre friction coeff. comparable magnitude. 2. Shear stiffness & belt damping significantly lower in best design. More than 80% power loss reduction.

Torque transmission of soft belt still sufficient? Belt slip rate? Functionality of accessories assured?Fatigue strength in long terms?Wear?

Calibrated design

No-constraint design

Constraintdesign

METHODOLOGYWORKFLOW IMPROVEMENTS


Simulation model

f(x1, x2…)

Known parameters

Assumptions

“Tuning factors”

Sensitivity

Inte

rdep

ende

ncy

Parameter categorizing

Sensitivity analysis

Validation Parameter identification

Calibration OptimizationFriction

Enhanced simulation engineering



AGENDA





CONCLUSION AND FURTHER DEVELOPMENTS


Conclusion

− All major friction components of a modern petrol engine have been modelled within GT-SUITE.

− GT-SUITE’s Integrated Design Optimizer is a powerful tool for extensive parameter studies of each friction sub-model. But comprehensive definition of parameter range and magnitude is challenging (usually due to lack of data).

− Current workflow of model parameter studies will be enhanced by extended sensitivity analyses.

Final parameter freeze of friction

sub-models

Model calibration and proof of friction

prediction

Validation of secondary model outputs (besides

friction)

Development of a friction optimized

engine design concept

Further investigation on

design regarding feasibility

Furth

er d

evel

opm

ents


THANK YOU!

optimization studies of engine friction...total engine friction, strip-down test. optimization...

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