Improved Fidelity Turbocharger Heat Transfer Models for Use in GT

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
1/24
Introduction
 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
2/24
Introduction
 In the turbocharger there are complex interactions among
Compressor
Turbine
different energy fluxes
WC + Q Comp
ETE
=
ηTmap =

W
Housing
Turbine power
Compressor power
Oil power
Heat power
Ts
Mechanical power
 Efficiency in turbine maps is a rough simplification of a complex
phenomena and seems not enough for a fully predictive modeling of
turbocharged engines
3/24
Introduction
 ETE ( Effective Turbine efficiency is a function of mechanical
efficiency and turbocharger heat fluxes:
ηTmap
WC + Q C
= ETE
W Ts
30
30q
Definition used in most
of supplier maps
𝑊̇𝑇𝑇𝑎
4qs
𝑊̇𝑇𝑇
4s
 Q C 
⋅ 1 +
 
W
C 

 Q C  T30 q
ETE = ηm ⋅ηsT ⋅  1 +
⋅

 WC  T30
WT WTsa
ηm ⋅  ⋅ 
ETE =
WTsa WTs
WT
ETE = ηm ⋅
WTs
 Q C 
⋅ 1 +
 
W
C 

 Q C
ETE = ηm ⋅ηsT ⋅  1 +

 WC
 
Q T 

 ⋅  1 − 
  mc pT30 
4/24
Introduction
 Direct use of turbine maps efficiency over predicts turbine outlet
temperature (due to neglecting heat transfer in the turbine side)
ηTmap
WC + Q C
= ETE
W Ts
WT
ETE = ηm ⋅
WTs
 Q C 
⋅ 1 +
 
W
C 

5/24
Project Definition & Approach
Procedure for developing and validating turbocharger heattransfer & 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
• 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 )
6/24
Mechanical Loss Model Definition
Journal Bearing
Thrust Bearing
 Good correlation between experimental & model data achieved
7/24
Heat Transfer Model Definition
 A Lumped model based on electrical analogy used to
account for different heat fluxes
8/24
Heat Transfer Model Definition
• 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
9/24
GT Power Model Definition
 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
10/24
GT Power Model Definition
The heat transfer
& mechanical
losses model
The inputs
 The model will need
instantaneous information
(temperatures, mass flows,
turbocharger speed …)
 Compressor & Turbine
adiabatic maps
 User function to link
external file
The main outputs
 Compressor efficiency
multiplier
 Turbine efficiency
multiplier
 Mechanical losses +
heat power
 Additional heat
11/24
GT Power Model Results: Full Load
Power
CIP
AirFlow
COP
 No effect was observed for above engine parameters using HTM
at FL steady state condition
12/24
GT Power Model Results: Full Load
Turbine Outlet Temperature
Compressor Outlet Temperature
 HTM is very important for accurately predicting turbine outlet
temperature & to some extent compressor outlet temperature
13/24
GT Power Model Results: Full Load
Nodal
Temperature
 HTM is able to accurately predict variation in nodal temperature at
different conditions
14/24
GT Power Model Results: Part Load
Power
CIP
AirFlow
COP
 Insignificant effect for above engine parameters using HTM at PL
steady state condition
15/24
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
16/24
GT Power Model Results: Part Load
Nodal
Temperature
 HTM is able to accurately predict variation in nodal temperature at
different conditions
17/24
GT Power Model Results: Transient
Torque
Turbo-speed
COP
Air-flow
 Transient results with HTM is better than base model
18/24
GT Power Model Results: Transient
COT
TOT
 Transient results with HTM is better than base model
19/24
Summary
 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
20/24
References
[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
21/24
22/24
GT Power Model Definition
 Compressor efficiency multiplier
•Using an adiabatic map
T20=
T10 +
a
T20 s − T10
ηmap
•Mechanical power consumed by the compressor
=
WC m C C p (T20 a − T10 )
•The effect of the heat transfer is included by
an efficiency multiplier
WCs
ηdiab WC − Q C
WC
=
=
KC =
WCs
ηmap
WC − Q C
WC
• The pseudo compressor power
W=
WC + Q C
C '
positive Q C mean heat flow from the compressor to the housing
23/24
GT Power Model Definition
 Turbine efficiency multiplier.
•Using an adiabatic map.
T4 =
T30 a − ηmap (T30 a − T4 s )
•In order to obtain that temperature from 30
heat effect must be included by mean of the
efficiency multiplier
WT + QT
WT + QT
ηT ,diab
WTs
=
=
=
KT
WT
ηT ,adiab
WTsa
1−γ


γ
 p T30 1 − Π 
mc


WT + QT T30 a


=
⋅
WT
WT
T30
1−γ

 p T30 a 1 − Π γ
mc





•The pseudo turbine power calculated by GTPower
W=
WT + QT
T '
24/24
GT Power Model Definition
 Mechanical efficiency.
•Power balance in the turbocharger shaft
 W + W
W=
T
C
f
•Pseudo power balance calculated by GT-Power
WT '− QT = WC '+ Q C + W f
•Friction power and addition power due to heat must be
extracted from the shaft
WT ' = WC '+ W f + Q C + QT



Wshaft
25/24

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