1 Waste-Gated Turbochargers Behaviour Under Steady and Unsteady Turbine Operation Advanced Charging & Downsizing Concepts Advanced Charging & Downsizing Concepts Stuttgart, Germany, 31 st March- 2 nd April, 2008 Silvia Marelli Internal Combustion Engines Group (ICEG) Department of Thermal Machines, Energy Systems and Transportation (DIMSET) University of Genoa – Italy
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Internal Combustion Engines Group (ICEG)Department of Thermal Machines, Energy Systems and Transportation (DIMSET)
University of Genoa – Italy
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 2
ContentsContents
Introduction
Exhaust turbochargers testing
Steady flow results
Unsteady flow analysis
Conclusions
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 3
ContentsContents
Introduction
Exhaust turbochargers testing
Steady flow results
Unsteady flow analysis
Conclusions
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 4
BackgroundBackground
The reduction of fuel consumption and CO2 emissions has recently becomea fundamental target for automotive propulsion systems together with lowexhaust emissions
Automotive diesel engines have been substantially improved in recentyears, due to the introduction of breakthrough technologies (electroniccontrolled FIS, VGT, etc), even if a further reduction of exhaust emissions(especially NOX and particulate) is required to comply with forthcoming EUand US regulations
The spark ignition (SI) engine needs today to significantly reduce fuelconsumption and CO2 emissions (especially at part load) while maintaininghigh specific power, very low exhaust emissions (3-ways catalyst) andexcellent vehicle driveability
To achieve this goal, different solutions can be addressed in a short period: alternative fuels (CNG, LPG, ethanol, etc)
engine downsizing and turbocharging
variable valve actuation (VVA)
direct gasoline injection (with stoichiometric combustion)
Turbocharging is therefore becoming a key technology for both gasolineand diesel automotive engines
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 5
Turbocharging the automotive SI engineTurbocharging the automotive SI engine
The successful application of exhaust turbocharging to downsized SIengines has to face several problems: transient response
low end torque
engine exhaust gas temperature (catalyst light-off, VG turbines application)
Variable geometry turbines are today widely used in diesel turbochargingbut their application to SI engines is difficult due to the harsh thermalexhaust environment
A waste-gate valve (pneumatically or electrically driven) is usually fitted asa turbocharger control system in SI applications, due to its effectiveness,low cost and ability to work at high gas temperatures
In order to optimize engine-turbocharger matching, turbine performancewhen the waste-gate valve is partially or totally opened should be known
Unfortunately, this information (which is a fundamental input for theoreticalsimulation models) is usually not provided by turbocharger manufacturer
A dedicated investigation on the turbocharger behavior in the openedwaste-gate region is therefore desirable, extended both to steady state andto the typically unsteady flow conditions occurring in automotive engines
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 6
Definition of compressor and turbine maps in an extended range
Evaluation of unsteady flow turbine performance
Analysis of turbocharger regulating systems behaviour
Interactions between the turbocharger and the engine intake andexhaust system
Development of unsteady flow performance prediction procedures
Dedicated test facilities are particularly suitableto investigate turbocharger performance
independently of the engine
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 7
ContentsContents
Introduction
Exhaust turbochargers testing
Steady flow results
Unsteady flow analysis
Conclusions
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 8
Turbocharger test facility options (1/2)Turbocharger test facility options (1/2)
Air temperature level at the turbine inlet “hot air” test rigs
• combustion chamber• high temperature transducers
“cold air” test rigs• electrical air heater• lower absolute turbocharger rotational speed
Turbine power absorption device turbocharger compressor
• limited operating range• high rotational speed allowed• need of specific experimental techniques/devices to
extend turbine curves• information on the compressor side of TC available
high speed dynamometer• extended measurement of turbine characteristics• complexity of design• restricted rotational speed range• low flexibility• very sensitive measuring equipment required
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 9
Turbocharger test facility options (2/2)Turbocharger test facility options (2/2)
Flow characteristics at the turbine inlet Steady flow
• definition of turbocharger maps• baseline analysis on TC regulating device behaviour
Unsteady flow• further complexity of the test facility• need of a pulse generator system• use of high speed measuring systems• information on the effect of unsteady flow parameters
on turbine performance Partial and unequal admission (tests on two-entry turbines)
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 10
Schematic diagram of typical TC test rigSchematic diagram of typical TC test rig
Ref.: D.E. Winterbone and R.J. Pearson, Design Techniques for Engine Manifolds: Wave Action Methods for IC Engines, 1999
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 11
The UNIGE test facilityThe UNIGE test facility
Development of “cold” air tests (max 400K) on I/E components and subassemblies(particularly automotive turbochargers)
Two independent feeding lines areavailable for the TC turbine andcompressor (acting as a dynamometer)
Suitable experimental techniques are usedto extend the definition of turbinecharacteristics
Turbine performance can also beinvestigated under unsteady flow andtransient conditions by using two differentpulse generator systems
AF air filter LM laminar flow meterAH air heater LC lubricating circuitAR air receiver PC pressure controlC compressor SC screw compressorDC dynamic compressor T turbineFM flow meter
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 12
Rotating valves pulse generator systemRotating valves pulse generator system
Turbocharger T C
Rotating valves
Compressor air supply
Turbine air supplya)Plenum
Designed to perform parametric studieson the effect of the main unsteady flowparameters
Tests on single and two-entry turbinesallowed
Pulsating flow generated by diametral slotrotating valves
Easy control of pressure pulse parameters(amplitude, mean value) at each turbineentry
Pulse frequency can be adjusted in thetypical range of automotive I/E circuits(10-200 Hz)
Unequal admission and not-phasedpulsating flow conditions can bereproduced when testing two-entryturbines
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 13
Cylinder head pulse generator systemCylinder head pulse generator system
Turbocharger
Compressor air supply
Flow distributor
Turbine air supply
Manifold
Engine head
T C
Plenum Designed to investigate engine exhaustsubsystem behaviour in unsteady flowconditions, including the effect of: circuit geometry valve actuation strategies
Three main components downstream ofthe damping plenum: flow distributor (designed to reproduce
the engine cylinder block) motor-driven cylinder head (fitted with
a fully flexible VVA system) engine exhaust manifold (different
configurations) Dedicated throttle valves in the flow
distributor to reproduce engine loadtransients
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 14
Measuring system and data processing (1/2)Measuring system and data processing (1/2)
Measurement of: pressure (average and instantaneous
static levels) temperature turbine and compressor mass flow rate turbocharger rotational speed pulse frequency
Measurements performed thoroughan automatic data acquisition systemcontrolled by PC using dedicatedprocedures developed in LabVIEW®
environment Specific analysis tools for post-
processing of instantaneous signals(different filtering and averagingtechniques available)
Transduce rssignals
Gould OS-4020
In strumentB
us(IE EE
488)
IOTECH ADC 488AD converter
NI PCI-6110PersonalComputer
interfaceGP-IB
Dig. stor. oscill.
Digital counter
Data acquis. unit
HP-5316A
HP-3497A
volmeterDigital
NI PCI-6250M
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 15
Measuring system and data processing (2/2)Measuring system and data processing (2/2)
Station 1: compressor inlet section Station 2: compressor outlet section Station 3: turbine upstream section Station 4: turbine downstream section Station 5: turbine mass flow rate
estimated by a laminar flow meter Station 6: compressor mass flow rate
estimated by a sharp edged orifice Station 7: measuring stations on
manifold branchessect. 4
RVRV
AR
LC
sect. 3
T C
CBCH
AR
FM
AH
PULSE GENERATOR SYSTEMS
LM
PC AF
DC
AF
AF PC
SC SC SC
AR
sect. 6
sect. 5
sect. 2
sect. 1
sect. 7
AF air filter FM flow meterAH air heater LM laminar flow meterAR air receiver LC lubricating circuitC compressor PC pressure controlCB cylinder block RV rotating valveCH cylinder head (VVA) SC screw compressorDC dynamic compressor T turbine
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 16
ContentsContents
Introduction
Exhaust turbochargers testing
Steady flow results
Unsteady flow analysis
Conclusions
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 17
Mass flow sensitivity to wasteMass flow sensitivity to waste--gate openinggate opening
Higher sensitivity to the turbineregulating system for lower waste-gate settings: 95 per cent of the total mass
flow rate increase is achievedwhen the waste-gate opening(connecting roddisplacement) is about 50 percent
a very little driving roddisplacement (about 5 percent, i.e., 1.5 mm) results ina substantial swallowingincrease
Waste-gate mass flow rate increase
1000100
0
AndAnd
Andnd
MM
MMAdvanced turbochargercontrol needs a veryaccurate waste-gate
driving system
0
20
40
60
80
100
0 20 40 60 80 100Waste-gate opening degree [%]
Was
te-g
ate
mas
sfl
owra
tein
crea
se[%
]
3
4000T
n rpmT K
1.32tTS
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 18
The investigation was performed on a small automotive turbocharger (IHIRHF3), matched to a downsized SI engine (4-cylinder, 1.4 litres)
Turbine steady flow curves were measured in an extended range, taking intoaccount different waste-gate valve settings (WG = driving shaft rotationangle)
A substantial increase in turbine mass flow rate was observed also in thecase of partial WG openings
In the meanwhile, turbine overall efficiency (’t, referred to the totalavailable gas energy) decreased definitely when opening the by-pass valve
1.00 1.25 1.50 1.75 2.00 2.25 2.50Expansion ratio (total to static)
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
Turb
ine
mas
sflow
rate
fact
or
[kg√
K/s
bar]
1.00 1.25 1.50 1.75 2.00 2.25 2.50Expansion ratio (total to static)
0.10
0.20
0.30
0.40
0.50
0.60
0.70
Turb
ine
o ver
allef
fici
ency
3T
nT
T3
n rpm
T K
20003000400055007000
αWG [deg]
082060
sttot
cTCm
sttot
tTCmTStt
hMP
hMP
'
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 19
Mass flow results for different flowconfigurations were expressed in termsof equivalent isentropic flow area Aeq
AeqR turbine rotor (combined flow) AeqWG WG valve (combined flow) A*eqWG WG valve (single flow) Aeq tot rotor + WG (measured) A*eq tot rotor + WG (calculated)
Both turbine rotor and waste-gate swallowing capacity proved to be lower inthe case of combined flow (rotor + by-pass port), probably due to theinteractions between the two flow components which take place within theturbine volute casing
Total mass flow rate calculated starting from turbine rotor and waste-gatesingle flow curves (A*eq tot) resulted substantially higher than measured level(Aeq tot), with differences ranging between 10 and 25 %
0 10 20 30 40 50 60 70Waste-gate opening [deg]
0
1
2
3
4
5
6
7
8
9
10
11
Equiv
alen
t is
entr
opic
flo
w a
rea Aeq tot
*
Aeq tot
AeqWG*
AeqWG
AeqR
3
T3 4
n/ T =3000 rpm/ K
p /p =1.2
0 10 20 30 40 50 60 70Waste-gate opening [deg]
0
1
2
3
4
5
6
7
8
9
10
11
Equiv
alen
t is
entr
opic
flo
w a
rea Aeq tot
*
Aeq tot
AeqWG*
AeqWG
AeqR
0 10 20 30 40 50 60 70Waste-gate opening [deg]
0
1
2
3
4
5
6
7
8
9
10
11
Equiv
alen
t is
entr
opic
flo
w a
rea
0 10 20 30 40 50 60 70Waste-gate opening [deg]
0
1
2
3
4
5
6
7
8
9
10
11
Equiv
alen
t is
entr
opic
flo
w a
rea Aeq tot
*
Aeq tot
AeqWG*
AeqWG
AeqR
Aeq tot*
Aeq tot
AeqWG*
AeqWG
AeqR
3
T3 4
n/ T =3000 rpm/ K
p /p =1.2
Analysis of turbine and WG mass flow contributionsAnalysis of turbine and WG mass flow contributions
To allow the by-pass component to be measured (by a hotwire probe), a proper configuration of the turbine outletcircuit was set up, using an exit pipe fitted with a dividingseptum
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 20
Turbine overall efficiency can becalculated referring to
the total mass flowing throughthe system (rotor + waste-gate)(’t)
the rotor mass flow rate (’t R)
Effect of WG opening on turbine efficiencyEffect of WG opening on turbine efficiency
TCmsttot
tt
hMP
'
TCmstR
tRt
hMP
' 0 10 20 30 40 50 60 70Waste-gate opening [deg]
0
0.2
0.4
0.6
0.8
1
1.2
Turb
ine
effici
ency
(ref
err e
dto
clos
ed
WG
conditio
n)
'tη't Rη
n/√T3 = 3000 rpm/√K
pT3
/ p4
= 1.2 bar
Efficiency referred to the total mass flow rate (η’t) significantly decreasedwhen opening the waste-gate valve, due to the relative change of thisquantity
A different behaviour was found for the efficiency referred to the rotor massflow rate (η’tR), with a minimum at intermediate waste-gate settings (αWGbetween 20° and 30°), followed by a slight increase for larger openings
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 21
ContentsContents
Introduction
Exhaust turbochargers testing
Steady flow results
Unsteady flow analysis
Conclusions
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 22
Pulse frequency confirmed to significantly affect pressure diagrams, resultingin substantial modifications of both pulse shape and amplitude, due to thewave action in pipes
Pressure oscillation profiles, instead, were similar when working at constantpulsating flow frequency
A clear increase in turbine inlet pulse amplitude at wider by-pass openingswas observed as a consequence of the higher total mass flowing through thesystem
α3 W G
3m
n/ T = 4000 rpm/ K = 20°
Configuration A p = 1.4 bar
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9Pre
ssure
[bar]
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Pre
ssur e
[bar]
f = 66.67 Hz
f = 40 Hz
3 3mn/ T = 4000 rpm/ K f =40 Hz Configuration A p =1.4 bar
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Turb
ine
inle
tpre
ssur e
[bar]
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Turb
ine
inle
tpre
ssure
[bar]
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Turb
ine
inle
tpre
ssure
[bar ]
0 1 2 3 4time/pulse period
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Turb
i ne
inle
tpre
ssure
[bar]
αWG =0 αWG =8°
αWG =20° αWG =60°
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 24
Effect of WG opening on waves propagationEffect of WG opening on waves propagation
Flow at the turbine outletbecame significantlyunsteady for wide waste-gate openings
When using a divided exitpipe (configurations B andC), pulse amplitude at theby-pass exit proved to bemore remarkable formaximum WG settings,highlighting a significanttransmission of flowunsteadiness through thevalve port
The hypothesis ofconstant pressuredownstream of the turbine(often used withinsimulation models)confirmed to beunacceptable, especially inthe case of opened WG
3 3mn/ T =4000 rpm/ K f=40 Hz ConfigurationB p =1.4 bar
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outle t
pre
ssure
[bar]
p4WG
p4RαWG =0 αWG =15°
αWG =35°
αWG =60°
3 3mn/ T =4000 rpm/ K f=40 Hz ConfigurationB p =1.4 bar
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outlet
pre
ssure
[bar]
0 1 2 3 4
time/pulse period
0.98
1.02
1.06
1.10
1.14
1.18
1.22
Outle t
pre
ssure
[bar]
p4WG
p4R
p4WG
p4RαWG =0 αWG =15°
αWG =35°
αWG =60°
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 25
In the case of a simple downstream mixing pipe (configuration A)pressure signals at the waste-gate outlet were affected by higherfrequency disturbances when the by-pass port was opened,probably due to significant interference with the flow from theimpeller
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 26
This effect was substantially reduced by using a connecting pipe fittedwith a dividing wall between the two flow components (configuration Band C)
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 27
Instantaneous turbine mass flow rateInstantaneous turbine mass flow rate
3 mn/ T =4000rpm/ K f=40Hz =1.33 mn/ T =4000rpm/ K f=40Hz =1.3
An increasing amplitude of massflow rate oscillation was found whenopening the waste-gate valve
A noticeable phase shift wasdetected between measuredpressure and mass flow profiles,due to the filling and emptying ofthe turbine volute casing
This effect was highlighted by anhysteresis loop surrounding thesteady state curve, the magnitudeof which increased in the openedwaste-gate region
1.1 1.2 1.3 1.4 1.5 1.6pressure ratio
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
Mass
flow
para
mete
r[k
g√
K/s
bar]
40 Hz
Steady state
1.1 1.2 1.3 1.4 1.5 1.6pressure ratio
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
Mass
flow
para
met
er[k
g√
K/s
bar
]
40 Hz
Steady state
αWG =0
α °WG =20
1.1 1.2 1.3 1.4 1.5 1.6pressure ratio
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
Mass
flow
para
mete
r[k
g√
K/s
bar]
40 Hz
Steady state
1.1 1.2 1.3 1.4 1.5 1.6pressure ratio
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
Mass
flow
para
met
er[k
g√
K/s
bar
]
40 Hz
Steady state
αWG =0
α °WG =20
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 28
ConclusionsConclusions
Turbocharging is becoming a key technology for both gasoline and dieselautomotive engines
Dedicated and fully flexible test facilities are a fundamental tool toinvestigate turbocharger performance
Several aspects related to automotive turbochargers operation requirefurther investigation: definition of TC turbine and compressor steady state characteristics
over the full potential operating range measurement of instantaneous turbine operating parameters in
unsteady flow conditions and comparison with the results providedby simulation models
development of correlation criteria between steady and unsteadyturbine average performance
partial and unequal two-entry turbine operation, including theeffect of out-of-phase pulsating flows
optimization of engine valve control strategies and exhaust circuitgeometry to improve TC transient performance
effect of unsteady flow operation on compressor surge ……
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 29
ConclusionsConclusions
The results of an extensive experimental investigation on the behaviorof a turbocharger for downsized SI automotive engines werepresented, focusing on the effect of the waste-gate valve opening onturbine steady and unsteady performance
Different aspects were highlighted by the study:
when opening the waste-gate, the total system mass flow ratecan’t be calculated assuming the turbine and the by-pass valveas two nozzles working in parallel under the same overallexpansion ratio
the definition of turbine efficiency in the region of openedwaste-gate should take into account the fluid portion effectivelyworking through the turbine rotor
in typical automotive applications flow unsteadiness at theturbine outlet becomes significant for wide waste-gate openings
instantaneous mass flow rate is influenced by the filling andemptying phenomena in the turbine volute casing, resulting inhysteresis loops surrounding the steady state curve
Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008 30
UNIGEUNIGE –– ICEG ReferencesICEG References
M. Capobianco, A. Gambarotta, "Unsteady flow performance of turbochargerradial turbine", 4th International Conference on Turbocharging and Turbochargers,Instn Mech Engrs, London, 1990.
M. Capobianco, A. Gambarotta, "Variable geometry and waste-gated automotiveturbochargers: measurements and comparison of turbine performance", ASMETransactions, Journal of Engineering for Gas Turbine and Power, 1992.
M. Capobianco, A. Gambarotta, “Performance of a twin-entry automotiveturbocharger turbine”, ASME Energy-Sources Technology Conference andExhibition, Houston, 1993.
M. Capobianco, S. Marelli., “Transient Performance of Automotive Turbochargers:Test Facility and Preliminary Experimental Analysis”, 7th International Conferenceon Engines for Automobile (ICE 2005), Isola di Capri, Settembre 2005, SAE Paper2005-24-066.
M. Capobianco, S. Marelli, “Turbocharger turbine performance under steady andunsteady flow: test bed analysis and correlation criteria”, 8th InternationalConference on Turbochargers and Turbocharging – I.Mech.E., London, 5/2006.
M. Capobianco, S. Marelli, “Unsteady flow behaviour of the turbocharging circuitin downsized SI Automotive Engine”, paper F2006P119, FISITA 2006 WorldAutomotive Congress, Yokohama, Ottobre 2006.
M. Capobianco, S. Marelli, “Waste-gate turbocharging control in automotive SIengines: effect on steady and unsteady turbine performance”, SAE 14th AsiaPacific Automotive Engineering Conference (APAC-14), August 5-8, 2007,Hollywood, SAE Paper 2007-01-3543
31
Thank you for the attention!
For more information and contact:
www.iceg.unige.it
31Silvia Marelli – University of Genoa – Advanced Charging & Downsizing Concepts – 2nd April 2008