Cold-Start Performance and Emissions Behavior of Alcohol Fuels in

Cold-Start Performance and Emissions Behavior of Alcohol Fuels in an SIDI Engine Using

Transient Hardware-In-Loop Test Methods

Andrew Ickes & Thomas Wallner Argonne National Laboratory

17th Directions in Engine-Efficiency and Emissions Research (DEER) Conference Detroit, Michigan October 3-6, 2011

WORK SUPPORTED BY U.S. DEPARTMENT OF ENERGY OFFICE OF VEHICLE TECHNOLOGY AND OFFICE OF BIOMASS

Motivation & Objectives

2

Assess the potential of gasoline-alcohol fuel blends for use in a direct-injection (DI) spark-ignition (SI) engine.

Utilize Engine Hardware-In-Loop capability to characterize emissions trends over a simulated test cycle.

Cold-Start Performance and Emissions Behavior of Alcohol Fuels in an SIDI Engine Using Transient Hardware-In-Loop Test Methods

Adapted from: Renewable Fuels Standard (Federal Register, 75(58))

U.S. Renewable Fuel Standard requires an increase of ethanol and advanced biofuels to 36 billion gallons by 2022.

iso-Butanol as possible advanced biofuel?

Comparison of Fuel Properties


3

Gasoline Ethanol iso-Butanol Chemical formula C4 - C12 C2H5OH C4H9OH Composition (C, H, O) Mass-% 86, 14, 0 52, 13, 35 65, 13.5, 21.5 Lower heating value MJ/kg 42.7 26.8 33.1 Density kg/m3 741 790 802 Octane number ((R+M)/2)1 - 93 100 103

Stoichiometric air/fuel ratio - 14.7 9.0 11.2

Latent heat of vaporization2 kJ/kg 380 – 500 919 686

Boiling Point1 °C 29 (IBP) 78 108

0

5

10

15

20

25

30

35

0 20 40 60 80 100

Oxy

gen

Cont

ent (

%)

Alcohol Blend Content (vol.-%)

1Measured for gasoline, typical reference values for alcohols 2Typical reference values

Ethanol Blends

iso-Butanol Blends

Engine Hardware-In-Loop Concept

4

Autonomie Virtual Vehicle

(dSPACE)

Speed, Torque

Throttle

Speed

Low-Inertia Dynamometer

2005 Opel Vectra 2.2 L Ecotec DI

Automatic (5-sp.)

NEDC Cold/hot start

System Validation Cycle Fuel Consumption,

Emissions Mass

Emissions sampling (pre/post) 5-gas emissions bench, FTIR

Driving Cycle Engine Response Emissions &

Fuel Economy

Vehicle Model


‘In-Vehicle’ coolant loop.

3-way catalyst

GM 2.2 L Ecotec SIDI

Gasoline Validation

Experimental Methods: Cycle and Validation

5

Vehicle Engine HIL

ECE-15 11.3 12.4

EUDC 6.1 6.5

NEDC 8.0 8.7

l/100km l/100km

Fuel Consumption Euro 4 Engine HIL

NOx < 0.1 0.02 ± 0.01

CO < 1 0.7 ± 0.2

HC < 0.068 0.03 ± 0.01

g/km g/km

Emissions

050010001500200025003000350040004500500055006000

-120-100

-80-60-40-20

020406080

100120

0 200 400 600 800 1000 1200

Engi

ne S

peed

(RPM

)

Sim

ulat

ed V

ehic

le

Spee

d (k

m/h

r)

Cycle Time (s)


Experimental Methods for Fuels Testing


6

Test Fuels Gasoline

E50

E85

isoBut83

Constant oxygen content (18%-mass)

Comparable alcohol content

Engine Modifications

GM 2.2L Ecotec SIDI (European spec. engine, not ‘flex-fuel’)

ECU calibration change made for alcohol fuels +18% fueling for E50/isoBut83 +30% fueling for E85

Conditions and Sampling Locations


7

Hot-Start

Pre-TWC Emissions

Post-TWC Emissions

Cold-Start

Fuel variation: Gasoline v. Ethanol Blends v. iso-Butanol Blend

TWC at operational temperatures

• Full conversion in TWC yields near-zero emissions

• Emissions trends comparable to those of steady state data

Pre-TWC Emissions

Post-TWC Emissions

TWC initially non-operational Engine not at operating temperature

Problematic for alcohol blends?

• Levels are subject to regulation

• Useful for diagnosing engine behavior

0

100

200

300

400

500

600

700

800

0 15 30 45 60

Cata

lyst

Bed

Tem

pera

ture

(ºC)

Time (s)

Cold Start

Cold Start (M30)

0.0

0.2

0.4

0.6

0.8

1.0

NOx HC CO

NED

C Cy

cle

Emis

sion

s (g

/km

)

Cold Start

Cold Start (M30)

Modified ‘Cold Start’ for High Alcohol Fuels


8

Initial Problem: Engine would not start (reliably) with high alcohol blends

Solution: modified ‘cold-start’ procedure • Motor engine at 1000 rpm until coolant temperature reaches 30°C • Execute ‘cold-start’ (M30)

Cycle Emissions Results


9

0.0

0.2

0.4

0.6

0.8

1.0

NOx THC CO

Gasoline

E50

E85

isoBut83

Cold

-Sta

rt N

EDC

Cycl

e Em

issi

ons

(g/k

m)

Euro IV Maximum Euro IV Max.

Euro IV Maximum

NEDC, cold-start, post-TWC emissions

2X regulated limit

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 200 400 600 800 1000 1200

HC

Emis

sion

s M

ass

Flow

(g/s

)

Time (s)

Gasoline

E50

E85

iB-83

Hydrocarbon Mass Emissions with Time


10

NEDC, Cold-Start (M30), post-TWC hydrocarbon emissions

0.0

0.5

1.0

1.5

2.0

2.5

0 10 20 30 H

C Em

issi

on C

umul

ativ

e M

ass

(g)

Time (s)

Gasoline E50 E85 isoBut83

Euro IV mass limit 6.5 s

0

10000

20000

30000

40000

0 5 10 15 20 25 30

HC

Emis

sion

s (p

pm-C

1, c

orr.)

Time (s)


Hydrocarbon Levels Engine-Out


11

NEDC, cold-start (M30), pre-TWC hydrocarbon emissions

Analyzer Saturation

Suggests Misfire

-4

-2

0

2

4

6

8

10

12

0 5 10 15 20 25 30

IMEP

(bar

)

Time (s)

Cyl. 1 Cyl. 2 Cyl. 3 Cyl. 4

Misfiring (complete) cycles

Combustion Instability with iso-Butanol83 During Initial Idle Period


12

NEDC, cold-start (M30), iso-Butanol83 fuel

-2

0

2

4

6

8

10

12

0 10 20 30

IMEP

(bar

)

Time (s)

Cyl. 1 Cyl. 2 Cyl. 3 Cyl. 4

Gasoline

Instability

Cylinder Cycles

Misfiring

#1 9

#2 74

#3 72

#4 40

Engine Behaviors Effecting ECU Responses


13

0

500

1000

1500

2000

2500

0 10 20 30

Engi

ne S

peed

(rpm

)

Time (s)


0

5

10

15

20

25

0 10 20 30 Time (s)


Higher O2 levels in exhaust due to misfire

Engine Underspeed at Idle Increased Exhaust Oxygen Concentration

Engine not reaching targeted idle speed with isoBut83

[ O2

] EXH

AU

ST (%

)

Engine Underspeed & System Reaction


14

Vehicle Command ECU Command to Throttle

0

20

40

60

80

100

0 5 10 15 20 25 30

Engi

ne T

hrot

tle

Ang

le (%

) Time (s)


0

10

20

30

40

0 10 20 30

Vehi

cle

Thro

ttle

Com

man

d (%

)

Time (s)


Lean Lambda Signal with iso-Butanol83 Misfire


15

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30

Lam

bda

(-)

Time (s)


ECU Lambda Signal

0

5

10

15

20

25

0 10 20 30 Time (s)


[ O2

] EXH

AU

ST (%

) O2 in exhaust due to misfire

Exhaust Oxygen Content

Increased Fuel Flow with iso-Butanol83


16

0

20

40

60

80

100

0 10 20 30

Fuel

Ene

rgy

Flow

(kW

)

Time (s)


Excessive Fuel Flow

Measured Fuel Flow

0

2

4

6

8

10

12

14

16

-2 0 2 4 6 8 10

Inje

ctor

Cur

rent

(A)

Time, Aligned (ms)


Injection at Time = 6 s.

Conclusions & Future Opportunities

Highlights cold-start as a significant limitation to the “drop-in” potential of high level iso-butanol blends as a gasoline replacement fuel.

Persistent misfire during initial cold-start idle period responsible for high HC emissions, and failure to meet emissions targets, using blend of 83% iso-butanol with gasoline.

Comparable behavior was not attained with near matched blend of ethanol and gasoline (E85).

Opportunities lie in (1) development of cold-start control strategies for high alcohol fuels like iso-butanol and (2) developing a detailed understanding physical behavior of fuels under initial engine start conditions.

17


Cold-Start Performance and Emissions Behavior of Alcohol Fuels in an SIDI Engine Using

Transient Hardware-In-Loop Test Methods

Andrew Ickes & Thomas Wallner Argonne National Laboratory

17th Directions in Engine-Efficiency and Emissions Research (DEER) Conference Detroit, Michigan October 3-6, 2011

Cold-Start Performance and Emissions Behavior of Alcohol Fuels in

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