performance simulation of small turbo gdi engines · larger turbine than for 3-cylinder engine...

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


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


CO

2em

issi

on in

NED

C /

(g/k

m)

50

100

150

200

250

300

350

400



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


Passengers cars AT/MT/CVTSource: KBA / status 2009


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


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

ion

ofS

mal

l Tur

bo G

DI E

ngin

es


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

ulat

ion

ofS

mal

l Tur

bo G

DI E

ngin

es


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

ulat

ion

ofS

mal

l Tur

bo G

DI E

ngin

es


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

ngin

es


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

ion

ofS

mal

l Tur

bo G

DI E

ngin

es


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

ngin

es


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

es


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

bo G

DI E

ngin

es


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

bo G

DI E

ngin

es


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


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

ngin

es


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


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


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


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

performance simulation of small turbo gdi engines · larger turbine than for 3-cylinder engine...

Documents