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Improved Fidelity Turbocharger Heat Transfer Models for Use in GT-Power

Manish Khare, Les Smith, JLR Jose R. Serrano, Pablo Olmeda, Francisco J. Arnau, UPV-CMT

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Turbocharger efficiency on engine operation is affected by several physical phenomena of different nature:

Turbomachinery internal irreversibility (isentropic efficiency

in comp. & turbine) Mechanical efficiency due to friction in journal & thrust

bearings Internal heat transfer effects from turbine side to oil and to

compressor side External heat transfer effects

Introduction

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In the turbocharger there are complex interactions among different energy fluxes

Turb

ine

Housing

Com

pres

sor

Turbine power Compressor power Mechanical power

Heat powerOil power

C CompTmap

Ts

W QETE

Wη

+= =

Efficiency in turbine maps is a rough simplification of a complex phenomena and seems not enough for a fully predictive modeling of turbocharged engines

Introduction

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ETE ( Effective Turbine efficiency is a function of mechanical efficiency and turbocharger heat fluxes:

Ts

C CTmap

W Q ETEW

η += =

1T Cm

Ts C

W QETEW W

η

= ⋅ ⋅ +

30

30

1

1

T Tsa Cm

Tsa Ts C

qCm sT

C

W W QETEW W W

TQETEW T

η

η η

= ⋅ ⋅ ⋅ +

= ⋅ ⋅ + ⋅

30

1 1C Tm sT

C p

Q QETEW mc T

η η

= ⋅ ⋅ + ⋅ −

30

30q

4s 4qs

�̇�𝑇𝑇 �̇�𝑇𝑇𝑎

Introduction

Definition used in most of supplier maps

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Direct use of turbine maps efficiency over predicts turbine outlet temperature (due to neglecting heat transfer in the turbine side)

Ts

C CTmap

W Q ETEW

η += =

1T Cm

Ts C

W QETEW W

η

= ⋅ ⋅ +

Introduction

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Procedure for developing and validating turbocharger heat-transfer & mechanical loss model (in collaboration with CMT)

• To elaborate a model able to predict heat transfer in turbochargers, based on work published by CMT

• To elaborate a turbochargers mechanical losses model, based on work published by CMT

• To link the previous models and to implement them in GT-power

Experimental activities on

Project Definition & Approach

• Thermo-hydraulic bench ( Conductive Conductance & Capacitance Characterization )

• Gas stand ( Convective Conductance & External Conductance, mechanical loss model Characterization )

• Dynamic engine test bench ( GT Power Engine model validation )

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Mechanical Loss Model Definition Journal Bearing Thrust Bearing

Good correlation between experimental & model data achieved

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Heat Transfer Model Definition

A Lumped model based on electrical analogy used to account for different heat fluxes

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• Internal Conductances Conductive: KT/H1, KH1/H2, KH2/H3, KH3/C

Convective: GAS/T, H1/oil, H2/oil, C/Air, H2/W or H3/Air

• External Conductances KT/amb, KH1/amb, KH2/amb, KH3/amb, KC/amb

K’T/H1, K’T/H2, K’T/H3, K’T/C, K’H1/H2, K’H1/H3, K’H1/C, K’H2/H3, K’H2/C,

K’H3/C

• Capacitances CT, CH1, CH2, CH3, CC

Heat Transfer Model Definition

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Geometry, properties of the materials and other constant parameters will be provided by an external file & this file links to GT power by a user function

GT Power Model Definition

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The inputs

The model will need instantaneous information (temperatures, mass flows, turbocharger speed …)

Compressor & Turbine adiabatic maps

User function to link external file

The heat transfer & mechanical losses model

Compressor efficiency multiplier

Turbine efficiency multiplier

Mechanical losses + heat power

Additional heat

The main outputs

GT Power Model Definition

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GT Power Model Results: Full Load

Power

COP CIP

AirFlow

No effect was observed for above engine parameters using HTM at FL steady state condition

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GT Power Model Results: Full Load

Turbine Outlet Temperature

HTM is very important for accurately predicting turbine outlet temperature & to some extent compressor outlet temperature

Compressor Outlet Temperature

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GT Power Model Results: Full Load

Nodal Temperature

HTM is able to accurately predict variation in nodal temperature at different conditions

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GT Power Model Results: Part Load

Power

COP

AirFlow

CIP

Insignificant effect for above engine parameters using HTM at PL steady state condition

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GT Power Model Results: Part Load

Turbine Outlet Temperature Compressor Outlet Temperature

HTM is important for accurately predicting turbine outlet temperature & to some extent compressor outlet temperature

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GT Power Model Results: Part Load

Nodal Temperature

HTM is able to accurately predict variation in nodal temperature at different conditions

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Torque COP

Turbo-speed

GT Power Model Results: Transient

Air-flow

Transient results with HTM is better than base model

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COT TOT

GT Power Model Results: Transient

Transient results with HTM is better than base model

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Turbocharger friction losses model (FLM) developed & validated, also linked to GT Power

Turbocharger heat transfer model (HTM) developed & validated, also linked to GT Power

HTM is fundamental for turbine outlet temperature (TOT) prediction

Capability of using a variety of turbocharger map sources while keeping predictability; i.e: adiabatic, hot gas stand, cold gas stand

Clear improvement in load transient predictability Currently validation limited to diesel but work planned for

gasoline to develop database for all JLR turbo machines

Summary

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[1] Serrano, J., Olmeda, P., Arnau, Dombrovsky, A. and Smith, L., ‘’ Methodology to Characterize Heat Transfer Phenomena in Small Automotive Turbochargers: Experiments and Modelling Based Analysis’’, Proceedings of ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, GT2014-25179 , June 16 – 20, 2014, Düsseldorf, Germany [2] Serrano, J., Olmeda, P., Arnau, F. and Reyes-Belmonte, M., 2013, “Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications”, SAE Int. J. Engines 6(2), doi:10.4271/2013-01-0576. [3] Serrano, J.R., Olmeda, P., Páez, A., and Vidal, F., 2010, “An Experimental Procedure to Determine Heat Transfer Properties of Turbochargers”, Measurement Science and Technology, 21, 035109 . [4] Serrano, J. R., Olmeda, P., Tiseira, A., García-Cuevas, L. M., and Lefebvre, A., 2013, “Theoretical and Experimental Study of Mechanical Losses in Automotive Turbochargers”, Energy, 55, pp. 888–898. [5] Serrano, J.R., Olmeda, P., Arnau, F.J., Reyes-Belmonte, M.A., Lefebvre, A. and Tartoussi, H. “A Study on the Internal Convection on Small Turbochargers”, submitted to Energy. [6] F. Payri, P. Olmeda, F.A. Arnau, A. Dombrovsky, L. Smith. External heat losses in small turbochargers: Model and experiments. Energy 71 (2014) 534-546

References

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Compressor efficiency multiplier

•Mechanical power consumed by the compressor

•Using an adiabatic map

•The effect of the heat transfer is included by an efficiency multiplier

• The pseudo compressor power

20 1020 10

sa

map

T TT Tη−

= +

( )20 10= − C C p aW m C T T

ηη

−= = =

−

Cs

diab C C CC

Csmap C C

C

WW Q WK

W W QW

' = + C C CW W Q

positive CQ mean heat flow from the compressor to the housing

GT Power Model Definition

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Turbine efficiency multiplier.

•In order to obtain that temperature from 30 heat effect must be included by mean of the efficiency multiplier

•The pseudo turbine power calculated by GT-Power

( )4 30 30 4a map a sT T T Tη= − −

' = + T T TW W Q

,

,

ηη

+

+

= = =

T T

T T p

T diab TsT

TT adiab

Tsa

W Q

W Q mcWKWW

1

30 1γγ−

−Π

T

T

p

W

mc1

30 1γγ−

−Π

aT

30

30

+= ⋅

aT T

T

TW QW T

GT Power Model Definition

•Using an adiabatic map.

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GT Power Model Definition Mechanical efficiency.

•Pseudo power balance calculated by GT-Power

•Power balance in the turbocharger shaft

•Friction power and addition power due to heat must be extracted from the shaft

= + T C fW W W

' '− = + + T T C C fW Q W Q W

' '= + + +

shaft

T C f C T

W

W W W Q Q