transient cooling system simulation by …...transient cooling system simulation by means of...

TRANSIENT COOLING SYSTEM SIMULATION BY MEANS

OF AUTOMATIC ENGINE PARAMETER CALIBRATION

Gerald Pichler, Simone Fratti, Gerald Steinwender, Günther Pessl

BMW Dieselmotorenentwicklung, Steyr

Kuli User Meeting 2013

Linz, Austria, 26th-28th June

G. Pichler , BMW Steyr Kuli User Meeting , 26th-28th June 2013 Seite 2

OVERVIEW

Introduction 1

Heat balance measurements 2

Kuli model set up 3

Engine model parameter calibration 4

Conclusion 5


OVERVIEW

Introduction 1


Kuli model set up 3


Conclusion 5

G. Pichler , BMW Steyr

Updated BMW internal testing guidline for the cooling system

Build up of a Kuli model for transient cooling cycle analysis for a 225kW BMW Diesel engine

Air side and coolant circuit modeling supported by 3D-CFD simulations

Validation of the baseline model with vehicle measurements (hill climb and high transient cycle)

Coupling of ModeFrontier® with Kuli with the aim to optimize the engine parameters

The model should be accurate enough for comparing and optimizing different cooling packages.

0,0

50,0

100,0

150,0

200,0

250,0

0 50 100 150 200 250 300

En

gin

e lo

ad

Vehicle speed

100kph+

Trailer

Kuli User Meeting , 26th-28th June 2013 Seite 4

INTRODUCTION AND MOTIVATION (1)

Hot Idle

Hill Solo

Sporty

US

Clubsport Racetrack

Hill 60kph

Solo Hill 35kph+

Trailer

210kph

Vmax

Hill Solo

Moderate


The BMW six cylinder Diesel engine Vehicle: BMW 535d

The 4 mass engine model of Kuli



6-Cylinder 740d, 535d, X5, X6 xDrive40d

225 kW 600 Nm

Piezo 2000 bar Crankcase aluminum

Two main groups of engine parameters

6 Heat transfer coefficients 4 Heat capacities

In sum 10 parameters of Kuli’s 4 mass engine model have to be optimized



Thermal engine model

Vehicle: Engine load point, Engine rpm

Component characteristics

Radiator, TOC, OC, CAC, EGR, ...

Track data

Altitude, ambient pressure,

ambient temperature,…

Underhood flow CFD simulation

Air mass flow rates, velocity distribution Heat balance measurements

Automatic transmission: Efficiency map,

TOC flow rates, heat capacities

Controllers

EGR controller

Fan

Thermostat…

Thermal engine capacities

Component weights, fluid volume

CFD coolant circuit

Coolant flow rates


OVERVIEW

Introduction 1


Kuli model set up 3


Conclusion 5


HEAT BALANCE MEASUREMENTS (1) WORKFLOW

Steady state measurements (heat balance for oil and water

circuits)

Load step measurements

(test bench)

Set up of a Kuli® model

Thermal engine model

calibration (4 mass model)

Transient cooling

simulations

modeFRONTIER®

Optimization algorithms •Heat capacities

•HTC

•Heat resistances

Manual

calibration

Load steps for different engine speeds:

• 1750 rpm

• 2250 rpm

• 3000 rpm


AirFuelradiation,convectionCACcoolantExhaustemErrorHQQQQHPdB


HEAT BALANCE MEASUREMENTS (2) ENERGY BALANCING

Balancing error Engine power

Exhaust enthalpy

Heat loss to coolant

Heat rejection CAC

Heat loss to ambient Injected fuel power

Air intake enthalpy

emP

ExhaustH

coolantQ

CACQ

radiation,convectionQ

FuelQ

AirH


HEAT BALANCE MEASUREMENTS (3) ENERGY BALANCING

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Am

ou

nt

of

fue

l an

d a

ir in

take

en

erg

y [

%]

Engine speed [rpm]

BalancingError

Convection & radiation

Heat rejection CAC

Exhaust enthalpy

Engine power

Coolant heat

Full load engine operating point Partial load engine operating point

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Am

ou

nt

of

fue

l an

d a

ir in

take

en

erg

y [

%]

Engine speed [rpm]

BalancingError

Convection & radiation

Heat rejection CAC

Exhaust enthalpy

Engine power

Coolant heat

Mean balancing error at full load: 3% Mean balancing error at partial load: 2%

Max. error from 850rpm to 1250 rpm up to 14%.

Coolant exit temp.=110°C Coolant exit temp.=110°C


HEAT BALANCE MEASUREMENTS (4) COMPARISION TESTBENCH VS. VEHICLE

165

103

164

102

0

20

40

60

80

100

120

140

160

180

4400 3750

Pe

[kW

]

U/min

Effective engine power

Testbench

Vehicle

0

10

20

30

40

50

60

4400 3750

Inje

cted

mas

s [m

g/st

roke

]

U/min

Injection quantityTestbench

Vehicle

high

11,458

10,217

11,972

9,929

0

2

4

6

8

10

12

14

4400 3750

Coo

lant

flow

[m

³/h]

U/min

Coolant flow through engine

Testbench

Vehicle

0

10

20

30

40

50

60

70

80

90

100

4400 3750Q

_W

Mot

or [k

W]

U/min

Total coolant heat flow

Testbench

Vehicle

0

5

10

15

20

25

30

35

4400 3750

Q_

WM

otor

[kW

]

U/min

Heat flow charge air

Testbench

Vehicle

15

16

15

15

15

15

16

16

16

16

16

17

4400 3750

dQ_

WM

otor

[kW

]

U/min

Deviation coolant heat flow

High deviation in coolant heat flow between

vehicle and testbench for both operating

points although injected fuel mass almost

same. To be checked:

• Air wind speed on test bench on crankcase

and on oil pan.

• Thermal conditions in the vehicle underhood

(convection and radiation). As a result a heat correction map had to be

implemented to the Kuli vehicle model.


OVERVIEW

Introduction 1


Kuli model set up 3


Conclusion 5


KULI MODEL SET UP (1) COOLANT CIRCUIT

To cabin heater

From cabin heater

High temperature radiator

Low temperature radiator

Thermostat

Water pump

Turbo charger cooling jacket

SCR dosing module

Low temperature path

for transmission cooling

Engine oil cooler

High pressure EGR cooler

Transmission oil cooler

EGR cooler valve


Test bench model was built up to simulate load steps.

Open circuit with boundary conditions from load step

measurements (flow rates, temperatures…).

Flow rates through EGR and oil cooler branch were not

measured on testbench. Flow split ratio was taken into

account based on 3D-CFD results.

Oil cooler entry on

coolant side is between cylinder 1-2 warm up

has to be considered

to calculate accurate

entry temperature

differences at the oil

cooler (heat transfer

between oil and water).

Oil circuit N57D30T0 Kuli User Meeting , 26th-28th June 2013 Seite 14


Testbench model EGR cooler branch

Oil-water cooler branch

Oil plate HX

1 2

3

A characteristic map

depending on an average oil

temperature and engine

speed was added.

The map was taken from a

fully detailed oil circuit

model.

Oil flow rate map



Vehicle model

1

2

3

1 High temperature radiator 9 HP-EGR cooler

2 Low temperature radiator 10 Engine model

3 Thermostat 11 Engine oil cooler

4 Expansion tank 12 Hydraulic oil cooler

5 Cabin heater 13 Charge air cooler

6 Thermal transmission model

7 Transmission oil cooler

8 Water pump

4

5

7 6

Charge air circuit

Hydraulic oil circuit

8

9 10

10

11

12

Engine oil circuit

Transmission oil circuit

13


KULI MODEL SET UP (4) AIR PATH MODEL

Air mass flow rates taken from 3D-CFD simulation

for stationary operating points (hill climb to Vmax)

Comparison of 3D-CFD air flow rates with flow rates

calculated out of vehicle measurements shows that

simulation is predicting ~10% less flow rate for hill climb

Accurate fan curve(s) w/o air flaps essential for Kuli

Extracting a flow distribution out of CFD for Kuli matrix is a

common workflow. For simulating accurate total air flow

rates, results from measurements were taken into account.

Condenser

Charge air cooler

Hydraulic Oil Cooler

Radiator

Fan System

Heater

Normal velocity profile of condenser and

CAC during 35 kph hill climb

Method for building up the fan

in 3D-CFD is still under evaluation fully rotating fan is today too time consuming in a

development process


OVERVIEW

Introduction 1


Kuli model set up 3


Conclusion 5


ENGINE PARAMETER CALIBRATION (1) COUPLING KULI AND MODEFRONTIER

Parameter optimization Kuli engine parameters

DOE done with 1500 designs

used for a sensitivity study for

a load step on testbench for

3000 rpm.

ModeFRONTIER Workflow

Parameters to be optimized:

6 x Heat capacity

4 x Heat transfer coefficients

55

60

65

70

75

80

85

90

95

100

105

0,0 15,0 30,0 45,0 60,0 75,0 90,0 105,0 120,0 135,0 150,0 165,0 180,0 195,0 210,0 225,0

T [

°C]

Time [sec]

Coolant temperature

Results of the DOE

Load step at 3000 rpm


-200

-150

-100

-50

0

50

100

150

200

Eff

ec

tiv

e S

ize

- E

rro

r o

il

-1

-0,8

-0,6

-0,4

-0,2

0

0,2

0,4

0,6

0,8

1

Eff

ec

tiv

e S

ize

- E

rro

r c

oo

lan

t


ENGINE PARAMETER CALIBRATION (2) RESULTS OF SENSITIVITY ANALYSIS

Effective size on error coolant Effective size on error oil

• The height of the bars represents the magnitude of the effect of the variable on the objective. E.g. the HTC of the oil pan has a low

effect on the error on the coolant side.

• A red colored bar means that the variable has a direct effect on the objective, meaning that an increase of the value of the variable

leads to a higher deviation.

• Blue colored bars are an indication that the defined variable space is in an acceptable range.

• Aim of the evaluation was to define an accurate variable range to speed up the following optimization.

Low importance, low effect Low importance, low effect


ENGINE PARAMETER CALIBRATION (3) LOAD STEP CALIBRATION ON TESTBENCH

Based on the results from sensitivity study the parameter

optimization was only done for the engine oil side for a load step at

1750rpm. The picture on the left side below shows the results of the

coolant side for the simulated load step at 1750rpm.

Load step at 1750rpm

Oil temperature (Optimization target)

Coolant temperature

Optimization results of ModeFrontier

About 60 designs of ModeFrontier were

Enough to find the correct engine parameters.


ENGINE PARAMETER CALIBRATION (4) LOAD STEP CALIBRATION ON TESTBENCH


Oil temperature (Optimization target)

Coolant


Parameters from 1750rpm load step optimization






ENGINE PARAMETER CALIBRATION (5) 2 DIFFERENT VALIDATION CYCLES

Miramas BMW test track Mt. Ventoux hill climb solo (moderate)

High dynamic test track cycle done in Miramas (FR). With temperature gaps up to 20K the cycle is ideal for the validation of the thermal engine masses.

The second test was done on Mt.Ventoux without trailer. Max speed for this test is about 80kph (~50mph). Following boundary conditions from tests

were used for transient simulation:

• Engine speed and BMEP

• Vehicle speed and gear

• Ambient conditions

Veh

icle

spe

ed [

kph]

Gea

r

Veh

icle

spe

ed [

kph]

Gea

r Alt

itud

e [m

]


ENGINE PARAMETER CALIBRATION (6) VALIDATION ON MT. VENTOUX HILL CLIMB

Engine oil temperature Coolant temperature

Results of engine parameter validation is not satisfying. Specially the comparison of the engine oil temperature between test and

simulation during hill climb shows a big deviation. The temperature trend on the coolant side is OK, also the deviation between test and

simulation is in an acceptable range. Based on latest results the approach for parameter optimization was updated.

Parameter optimization for oil and cooant for hill

climb cycle

Validation on Miramas test track

cycle

Validation on test bench load steps

Updated approach


ENGINE PARAMETER CALIBRATION (7) VALIDATION ON MT. VENTOUX HILL CLIMB

Engine oil temperature Coolant temperature


climb cycle


cycle


Te

mp

era

ture

[°C

]

Time [sec]

Load step optimized

Te

mp

era

ture

[°C

]

Time [sec]

Cycle optimized

Te

mp

era

ture

[°C

]

Time [sec]

Cycle optimized

ModeFrontier optimization (Pareto frontier)

Err

or

co

ola

nt

[-]

Te

mp

era

ture

[°C

]

Time [sec]

Load step optimized

Error oil [-]

Final design Pareto frontier

The picture above shows the best results of the

optimization regarding the error on oil and

coolant side. Pictures on the left side are

showing an overall improvement on the

temperature trends of oil and coolant.


ENGINE PARAMETER CALIBRATION (8) VALIDATION ON MIRAMAS TEST TRACK CYCLE


climb cycle


cycle


Coolant temperature

Engine oil temperature

Some time sections of the cycle are showing

almost perfect correlation between simulation and

measurement specially on the coolant side.

Specially in propulsion engine operation points the

oil temperatures are lower than the simulation is

showing.

The wind conditions during test track

measurement have a high influence on the results

but were not documented directly in the test

report.

Round 1 Round 2


ENGINE PARAMETER CALIBRATION (9) VALIDATION ON TEST BENCH LOAD STEPS


climb cycle


cycle


55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

110,0

115,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330

Tem

pe

ratu

re [°

C]

Time [s]

Simulation

Experimental

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

110,0

115,0

120,0

125,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330

Tem

pe

ratu

re [°

C]

Time[s]

Simulation

Experimental

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255

Tem

pe

ratu

re [°

C]

Time [s]

Simulation

Experimental

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

110,0

115,0

120,0

125,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255

Tem

pe

ratu

re [°

C]

Time[s]

Simulation

Experimental

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

110,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360

Tem

pe

ratu

re [°

C]

Time [s]

Simulation

Experimental

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

110,0

115,0

120,0

125,0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360

Tem

pe

ratu

re [°

C]

Time[s]

Simulation

Experimental

1750 rpm 2250 rpm 3000 rpm


OVERVIEW

Introduction 1


Kuli model set up 3


Conclusion 5


CONCLUSION A transient engine model for cooling system analysis was built up in Kuli and a validation with

two different driving cycles and load step measurements on test bench were done.

Comparison of measured coolant heat balances in the vehicle and on test bench show

significant differences at almost the same engine operating points. Specially convective heat

transfer of crankcase, oil pan and cylinder head is difficult to determine exactly on the test

bench.

Heat transfer coefficients and the thermal inertia (direct/indirect) of the engine model were

optimized automatically by coupling Kuli with modeFRONTIER®

Generation of a vehicle model based on a test bench model to a was partially successful. The

oil temperatures during hill climb showed biggest deviation. Therefore a cycle optimization of

the engine parameters for the hill climb cycle was done showing accurate results on Miramas

test cycle finally.

Absolute media temperatures during driving cycles with deviations below 5K is difficult to

reach but possible if a database of previous cycle measurements is available.

In conclusion the created transient model is accurate enough for comparing and optimizing

different cooling packages, but the proposal of absolute media temperatures during driving

cycles with deviations below 5K is difficult to reach but possible if a database of previous

cycle measurements is available.

G. Pichler , BMW Steyr Kuli User Meeting , 26th-28th June 2013

transient cooling system simulation by …...transient cooling system simulation by means of...

Documents