friction and heat transfer effects on turbocharger modeling · pdf filefriction and heat...

Friction and Heat Transfer Effects

on Turbocharger Modeling

Frankfurt, 22.10.2012

Dominik Lückmann1, Christof Schernus2, Tolga Uhlmann2, Björn Höpke1, Carolina Nebbia3

1 Institute for Combustion Engines (VKA), RWTH Aachen University 2 FEV GmbH, Aachen 3 FEV Italia S.r.l.

1

© by VKA, FEV – all rights reserved. Confidential – no passing on to third parties

Content

Introduction

Impact of Compressor Heat Flux on TC Maps

Impact of Bearing Friction Losses on TC Modeling

GT-Power TC Modeling

Results of a Simple Friction and Turbine Heat Transfer Model

Summary

2


1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 1000 2000 3000 4000 5000 6000 7000 8000

Reduced Turbine Speed nTC*T0.5 / min-1/K0.5

Turb

ine P

ressu

re R

atio / -

Turbine Operation Area at WOT and Load Step

3

Load Step neng = 1300 min-1

WOT neng = 1000-5500 min-1

Engin

e T

orq

ue

M

Engine Speed n


WOT neng = 1000-5500 min-1


1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 1000 2000 3000 4000 5000 6000 7000 8000

Reduced Turbine Speed nTC*T0.5 / min-1/K0.5

Turb

ine P

ressu

re R

atio / -

Standard Hot Gas Measurement Range

4

Standard Measurement (Open Loop)

T3 = 600 °C

Measurement

Range Below

0.5 * nTC,max


WOT neng = 1000-5500 min-1

Engin

e T

orq

ue

M

Engine Speed n


WOT neng = 1000-5500 min-1

Below 0.5 * nTC,max


Turbine Net Efficiency is a function of

Aerodynamic turbine performance

Compressor heat flux

Bearing friction losses

Calculation of the Turbine Efficiency

Friction and Heat Transfer Effects on Turbocharger Modeling

5

Turbine efficiency as a function of turbine outlet temperature

)hh(m

)hh(m

P

P

is4,3T

43T

isT,

TisT,

)()(

)(4

is4,3T

12V

isT,

FTVTCm,isT,netT, Tf

hhm

hhm

P

PPP

Turbine efficiency definition using compressor power

0T Q

0VQ

Mach similarity does not apply to turbine net efficiency maps

Heat flux, friction losses and aerodynamic has to be separated

Turbine

TQ

VQ

11 pT

22 pT

TCn

Cm Tm

44pT

33 pT

Compressor

Burner


Content

6

Introduction





Summary


Heat Flux into the Compressor

Coolant Temperatur Variations

7

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5

Tu

rbin

e N

et

Effic

iency η

T,is*η

m,A

TL / -

Turbine Pressure Ratio p3t/p4 / -

Standard measurement range down

to approx. 0.4 - 0.5 * nATL,max due to a

dominant heat flux into the

compressor at lower speeds

)hh(m

)hh(m*

stis,4,tot3,T

tot1,tot2,VTCm,isT,

w/o CW

nTC,max

TCWT:

T3 = 600 °C

TOil = 90 °C

nTC,min



Coolant Temperatur Variations

8

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5

Tu

rbin

e N

et

Effic

iency η

T,is*η

m,A

TL / -


w/o CW

115 °C

90 °C

40°C

nTC,min

nTC,max

TCWT:

T3 = 600 °C

TOil = 90 °C With lower coolant temperature the heat

flux into the compressor is reduced

ηT



Coolant Temperatur Variations – Total Turbocharger Efficiency

9

Negligible Impact of the compressor heat

flux on the aerodynamic performance

Conditions to separate

Aerodynamic performance

Heat flux to compressor

fulfilled

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

1.0 1.5 2.0 2.5 3.0 3.5

To

tal T

urb

och

arg

er

Effic

iency η

C,is*η

T,is*η

m,A

TL


nTC,min

nTC,max

w/o CW

115 °C

90 °C

40°C

TCWT:

T3 = 600 °C

TOil = 90 °C


0

4

8

12

16

20

24

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

Spe

cific

he

at

flux t

o c

om

pre

sso

r q

C /

kJ/k

g .

Compressor mass flow rate / kg/s


Calculation of the Heat Flux

10

nred = 2150 min-1K0.5

T3 = 600 °C

Toil = 90 °C

w/o CW

Experimental Approach (Scharf)1

„FVV TC-Wärmeströme“ CFD (Heuer)2

Model Based Approach (Sirakov, Casey)3

1 Extended Turbine Mapping and Engine Simulation, Dissertation, Scharf 2 TC-Wärmeströme, FVV Abschlussbericht, Bohn, Heuer, Moritz, Wolff 3 Evaluation of Heat Transfer Effects on Turbocharger Performance, ASME GT2011-45887, Sirakov, Casey


Content

11

Introduction





Summary



Friction Measurement


12

TC

Fri

ctio

n P

ow

er L

oss

/ W

FA = 0 N

TOil = 90 °C

pOil = 4 bar (abs.)

TOil = 90 °C

pOil= 4 bar (abs.) FA = 0 N

pOil = 4 bar (abs.)

120 000 1/min 120 000 1/min

80 000 1/min 80 000 1/min

40 000 1/min 40 000 1/min

450

300

200

550

50

100

150

250

350

400

500

0

TC

Frictio

n P

ow

er

Loss /

W

40000 80000 120000 0

TC Speed / 1/min

40 60 80 100 120

Oil Temperatur / °C

-60 -40 -20 0 20 40 60

Thrust Load / N



neng = 1500 RPM, WOT


13

4000

4500

5000

5500

6000

red

. T

C S

pe

ed

/ R

PM

*K^-

0.5

850

1050

1250

1450

1650

120000

140000

160000

180000

200000

Turb

ine I

nle

t G

as T

em

p.

/ K

TC

Spe

ed /

RP

M

InletTurbine

TCred

T

nn



neng = 1500 RPM, WOT


14

350

450

550

650

750

850

-80 20 120 220 320 420 520 620

TC

Fri

ctio

n /

W

Engine CA / °AFTDC

120000

140000

160000

180000

200000

TC

Spe

ed

/

RP

M

4000

4500

5000

5500

6000

red

. T

C S

pe

ed

/ R

PM

*K^-

0.5

850

1050

1250

1450

1650

120000

140000

160000

180000

200000

Turb

ine I

nle

t G

as T

em

p.

/ K

TC

Spe

ed /

RP

M

InletTurbine

TCred

T

nn

K15873redMapping TC, .nn

%355

d

))d(-)((Error

Turbine

Mapping TC,FrictionPower-GTTC,Friction

.

P

nPnP


Content

15

Introduction





Summary


Isentropic Adiabatic Turbine Efficiency


16

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Tu

rbin

e E

ffic

iency η

T /

-.

Turbine Pressure Ratio p3t/p4 / - .

)hh(m

)hh(m*

stis,4,tot3,T

tot1,tot2,VTCm,isT,

Net turbine efficiency




17

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Tu

rbin

e E

ffic

iency η

T /

-.


)hh(m

P)hh(m

stis,4,tot3,T

Ftot1,tot2,VisT,

Isentropic efficiency

)hh(m

)hh(m*

stis,4,tot3,T

tot1,tot2,VTCm,isT,





18

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Tu

rbin

e E

ffic

iency η

T /

-.


)hh(m

P)hqh(m

stis,4,tot3,T

Ftot1,Ctot2,Vadis,T,

Isentropic adiabatic efficiency

)hh(m

P)hh(m

stis,4,tot3,T

Ftot1,tot2,VisT,

Isentropic efficiency

)hh(m

)hh(m*

stis,4,tot3,T

tot1,tot2,VTCm,isT,



GT-Power Turbocharger Modeling

19

Separate modeling of

Aerodynamic turbine performance


improves the simulation quality

0

200

400

600

800

1000

1200

1400

1600

0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

TC Speed / min-1

Fri

ctio

n P

ow

er

/ W


PF

nTC

Extended turbine maps Extended compressor map

mcorC

. 0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6

Tu

rbin

e E

ffic

ien

cy e

ta_

T /

-.

Turbine Pressure Ratio p3t/p4 / - .isentr

oper

adia

bate

rT

urb

inenw

irkun

gsgra

d η

is,a

d,T

Turbinendruckverhältnis p3t/p4

ηT

πT

1.00

1.40

1.80

2.20

2.60

3.00

3.40

3.80

4.20

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

Com

pre

sso

r P

ress

ure

Ratio

p 2

t/p1t

/ -

.

Corr. Compressor Mass Flow Rate m_dot_cor_C / kg/s .

πC


GT-Power Turbocharger Advanced Modeling

20

Extended turbine maps


Extended compressor map

mcorC

. 0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6

Tu

rbin

e E

ffic

ien

cy e

ta_

T /

-.

Turbine Pressure Ratio p3t/p4 / - .isentr

oper

adia

bate

rT

urb

inenw

irkun

gsgra

d η

is,a

d,T

Turbinendruckverhältnis p3t/p4

ηT

πT

1.00

1.40

1.80

2.20

2.60

3.00

3.40

3.80

4.20

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

Com

pre

sso

r P

ress

ure

Ratio

p 2

t/p1t

/ -

.

Corr. Compressor Mass Flow Rate m_dot_cor_C / kg/s .

πC

TC

Fri

ctio

nP

ow

er L

oss

/ W

FA = 0 N

TOil = 90 °C

pOil = 4 bar (abs.)

TOil = 90 °C

pOil= 4 bar (abs.)FA = 0 N

pOil = 4 bar (abs.)

120 000 1/min 120 000 1/min

80 000 1/min 80 000 1/min

40 000 1/min 40 000 1/min

450

300

200

550

50

100

150

250

350

400

500

0

TC

Friction

Pow

er

Loss / W

40000 80000 1200000

TC Speed / 1/min

40 60 80 100 120

Oil temperatur / °C

-60 -40 -20 0 20 40 60

Thrust Load / N

Turbocharger Heat Flux Model Environment

Turbine hous.Comp. hous.

Comp. Turb.Shaft

Shaft hous.

Mech. Power

OilCoolant

Thrust

Load


Content

21

Introduction





Summary


Friction model enables turbo engine modeling in cold-start and warm-up scenarios

Lower turbo speed and slower acceleration

Increased backpressure by higher power consumption

PMEP

BSFC

Impact of Turbocharger Inlet Oil Temperature on Load Steps


22


Friction model enables turbo engine modeling in cold-start and warm-up scenarios

Lower turbo speed and slower acceleration

Increased backpressure by higher power consumption

PMEP

BSFC

Delayed engine response in

Drive-away

Tip-in from low part load

Impact of Turbocharger Inlet Oil Temperature on Load Steps


23

12

12.5

13

13.5

14

14.5

15

20 30 40 50 60 70 80 90 100 110 120

IME

P @

2 s

ec

/ b

ar

TC oil inlet temperature / °C

Small Turbocharged Gasoline Engine

Load Steps at 1400 RPM

time

IME

P

TC

fri

ction p

ow

er

TC speed

Oil Temp.


Simple Heat Transfer Model


24

specific

turb

ine h

eat flux

tot4,TFtot1,Ctot2,Vtot3,T hm)P)hqh(m(hmQT

T,m

TQ

heat input rate

Hot gas measurements

T3 Variations

Turbine Volute


Simple Heat Transfer Model


25

specific

turb

ine h

eat flux

tot4,TFtot1,Ctot2,Vtot3,T hm)P)hqh(m(hmQT

T,m

TQ

heat input rate

Hot gas measurements

T3 Variations

Turbine Volute

Tu

rbin

e o

utlet te

mp. /

°C

%T

TT100error

testbench engine

testbench enginesim

w/o heat flux model

with heat flux model

neng = 2000 RPM 6500 RPM

700

750

800

850

engine measurement

error = 7.5 % 1.3 % 3.6 % 0.6 %


Summary

Due to the measurement methodology the calculation of the turbine (net) efficiency and

compressor efficiency is impacted by the heat transfer to the compressor and the bearing

friction losses

The heat transfer into the compressor has no impact on the aerodynamic performance of the

compressor

This enables a separation of

Compressor heat flux

Aerodynamic Performance

and combined with a bearing friction measurement allows to create TC Maps that apply the

Mach similarity

On this basis advanced heat transfer models or bearing friction loss models can been

introduced (decrease of IMEP @ 2 sec by 1 bar Oil temp. 90 50 °C)

The shown simple turbine heat transfer model shows already good results.

(error reduction in turbine outlet temperature by 80 %)

26

© by VKA – all rights reserved. Confidential – no passing on to third parties


Frankfurt, 22.10.2012

Dominik Lückmann1, Christof Schernus2, Tolga Uhlmann2, Björn Höpke1, Carolina Nebbia3

1 Institute for Combustion Engines (VKA), RWTH Aachen University 2 FEV GmbH, Aachen 3 FEV Italia S.r.l.

27

Thank you for your attention!

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