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Performance Simulation of Small Turbo GDI Engines
Christof Schernus1, Carolina Nebbia2, Carsten Dieterich1, Stefan Wedowski11FEV GmbH, Aachen2FEV Italia s.r.l., Torino
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Overview
IntroductionTarget, Dimensions and Package ConsiderationsMass Balance and FrictionComparison of T/C Engines w/ 2 & 3 cylindersConclusion
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
CO2 scatter (NEDC) & 2012/2019 targets
750 1000 1250 1500 1750 2000 2250Inertia Weight Class / kg
CO
2em
issi
on in
NED
C /
(g/k
m)
50
100
150
200
250
300
350
400Passengers cars AT/MT/CVTSource: KBA / status 2009
Gasoline vehicles, incl. start/stopGasoline hybrid vehicles
750 1000 1250 1500 1750 2000 2250Inertia Weight Class / kg
CO
2em
issi
on in
NED
C /
(g/k
m)
50
100
150
200
250
300
350
400
750 1000 1250 1500 1750 2000 2250Inertia Weight Class / kg
750 1000 1250 1500 1750 2000 2250Inertia Weight Class / kg
CO
2em
issi
on in
NED
C /
(g/k
m)
50
100
150
200
250
300
350
400C
O2
emis
sion
in N
EDC
/ (g
/km
)
50
100
150
200
250
300
350
400Passengers cars AT/MT/CVTSource: KBA / status 2009
Gasoline vehicles, incl. start/stopGasoline hybrid vehicles
Passengers cars AT/MT/CVTSource: KBA / status 2009
Gasoline vehicles, incl. start/stopGasoline hybrid vehicles
Fleet standards 2012Fleet standards 2012
Proposed fleet standards 2019Proposed fleet standards 2019
130 g/km CO2
95 g/km CO2
-27 %
Downsizing = possible path to meet CO2 targets for 2012/2019
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Coping with CO2 targets:Load point shift by Downsizing
15%
10%
5%
1%
0
5
10
15
20
25
1000 2000 3000 4000 5000 6000
.
15%
10%
5%
1%
Engine speed / rpm
BM
EP /
bar
5
10
15
2
25
1000 2000 3000 4000 5000 6000
T/τ3-Cyl., VD=1.0ltr, 80kW
0
5
10
15
2
25
001000 2000 3000 4000 5000 6000
Downsized engine drivability requires boosting
Per
form
ance
Sim
ulat
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ofS
mal
l Tur
bo G
DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Downsizing: Improved Engine Length
Package improvement Base: 1.4 dm³ 4-cyl. NA, 74 kW
Stroke/bore = 80/74.5 Bore pitch = 85.5 mm
Mk #1: 0.9 dm³ 4-cyl. Turbo, 74 kW Stroke/bore = 69.1/64.3 Bore pitch = 73 mm
Mk #2: 0.9 dm³ 3-cyl. Turbo, 74 kW Stroke/bore = 76/70.8 Bore pitch 80.4 mm
Mk #3: 0.9 dm³ 2-cyl. Turbo, 74 kW Stroke/bore=87/81 Bore pitch 92 mm
- 7%
- 17%
- 28%
2- and 3-cylinder engine bore sizes suitable for GDI
oil dilution!
Per
form
ance
Sim
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mal
l Tur
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DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Mass Balance and FrictionExample of 2-cylinder Parallel Twin Cranktrain
Parallel Twin needs 1st order balancer shaft, FMEP ↑
0
1
2
3
1000 2000 3000 4000 5000 6000
Engine Speed [rpm]
FMEP
[bar
]2-cylinder 3-cylinder
Per
form
ance
Sim
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ofS
mal
l Tur
bo G
DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Equal TC: Full load performance and fuel consumption
target of 74 kW achievable with both, but 3-cyl has reserves
8%
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Compressor operation at full load
Similar risk of surge2-cylinder @ higher rpm: Higher boost pressure Larger loops Excursion into ηsC ↓
larger fluctuations in 2-cyl at med. & high engine speeds
Per
form
ance
Sim
ulat
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ofS
mal
l Tur
bo G
DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Turbine characteristics at full load
TC match to 3-cyl. Appears too small for 2-cylinder engine
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Turb. Efficiency, 2500 rpm, equal T/C
Larger excursions to low BSR in 2-cyl. Engine⇒ Turbine appears too small
Turbine PR ↑
0cDBSR ω
=Blade Speed Ratio:
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
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© by FEV – all rights reserved. Confidential – no passing on to third parties
Pulsation effects on turbine side, 2500 min-1, equal T/C
Slight backflow
2-cyl flow rate discontinued between exhaust strokes
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
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DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
0.0
0.2
0.4
0.6
0.8
0.0 1.0 2.0 3.0 4.0 5.0
Turbine Pressure Ratio / -
Red
. tur
bine
Mas
s Fl
ow /
kgK
^0.5
/(sba
r)
CFD Assisted Turbine Map Extension to Cover Pulsation Effects
Model must cover Stagnation and Reversal of turbine flow
0≈m
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
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DI E
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© by FEV – all rights reserved. Confidential – no passing on to third parties
0.0
0.2
0.4
0.6
0.8
0.0 1.0 2.0 3.0 4.0 5.0
Turbine Pressure Ratio / -
Red
. tur
bine
Mas
s Fl
ow /
kgK
^0.5
/(sba
r)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
0.0 1.0 2.0 3.0 4.0 5.0Turbine Pressure Ratio / -
Red
. tur
bine
Mas
s Fl
ow /
kgK
^0.5
/(sba
r)
140 m/s, CFD
140 m/s, Measured
340 m/s, CFD
340 m/s, Measured
430 m/s, CFD
430 m/s, Measured
Steady State OperationBoundary (Run Away Curve)
CFD Assisted Turbine Map Extension to Cover Pulsation Effects
Model must cover Stagnation and Reversal of turbine flow
0≈m
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
2- and 3-cylinder turbochargingInterim conclusion
Surge limited low end torque Applies to both 2- and 3-cylinder engine Already with small base turbocharger
2-cylinder needs larger turbineLarger turbine only available with larger compressorLarger compressor in conflict with low end torque Map of larger compressor ranges in larger flow rates Required boost pressure at low speeds exceeds surge line
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
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es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Larger turbo for 2-cylinder engine
Pre-swirl device Converts standard compressor into VGC extends operation range to small flow
rate Wide open blades
New generation: negligible pressure loss Closing blades:
swirl ↑, pCin ↓, turbo rpm ↑ makes compressor virtually smaller
High boost at low speeds from large compressor with preswirl
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Larger turbo for 2-cylinder engine
3-cyl with KP352-cyl with KP39 w/o & w/ pre-swirl device
2-cyl. low end torque can be recovered by larger VGC
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Different T/C’s on 2-cylinder engine
Variable pre-swirl helps compressor operation: smaller loops, better surge margin, better efficiency
Per
form
ance
Sim
ulat
ion
ofS
mal
l Tur
bo G
DI E
ngin
es
© by FEV – all rights reserved. Confidential – no passing on to third parties
Conclusions
GT-POWER study on small turbo enginesDifferent T/C matching for 2-cylinder engines Larger turbine than for 3-cylinder engine Larger compressor than for 3-cylinder engine Larger fluctuations due to less continuous flow3-cyl with better NVH and fuel consumptionPackage and cost advantageous for 2-cyl, e.g. for HEV2-cyl’s larger bore likely to cause less oil dilution
Performance Simulation of Small Turbo GDI Engines
Christof Schernus1, Carolina Nebbia2, Carsten Dieterich1, Stefan Wedowski11FEV GmbH, Aachen2FEV Italia s.r.l., Torino
AcknowledgementsBWTS: Frank Schmitt Polito: Federico MilloFEV: Richard Aymanns, Raimund Vedder,Johannes Scharf, Franz-Gerd Hermsen
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