evaluating exhaust emission performance of urban … · evaluating exhaust emission performance of...

VTT TECHNICAL RESEARCH CENTRE OF FINLAND

2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA

VTT PROCESSESKimmo Erkkilä

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EVALUATING EXHAUST EMISSION PERFORMANCE OF URBAN BUSES USING TRANSIENT

HEAVY-DUTY CHASSIS DYNAMOMETERKimmo Erkkilä, Nils-Olof Nylund, Markku Ikonen and Juhani Laurikko,

VTT Technical Research Centre of FinlandVTT Processes, Engines and Vehicles




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OUTLINE

Background– HD engine emission legislation

Advantages of complete vehicle testing (on chassis dynamometer)

Features of VTT’s heavy-duty emission laboratory

Ongoing transit bus emission evaluation– Methodology– Results of 2002 and 2003 measurements– Conclusions




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BACKGROUND

HD engine emission certification is based on engine testing– Engines are run in engine dynamometers using specified load

patterns

In the US: HD Transient cycle used for several years

In Europe: steady-state testing (ESC) is supplemented by transient testing (ETC, directive 1999/96/EC)

Transient testing represents real-world conditions better than steady-state

However, engine testing does not take the whole vehicle into account




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Certification testing according to Directive 1999/96/EC calls for:

From 2000 onwards: Diesel engines

– ETC is required in addition to ESC (and ELR), if advanced emission aftertreatment is used for NOX and/or PM control

Natural gas engines– ETC only

From 2005 onwards:Diesel engines:

– ETC required for all enginesNatural gas engines:

– ETC only

BACKGROUND - EUROPEAN HD LEGISLATION




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WHY COMPLETE VEHICLE TESTING ?

Engine testing does not account the properties of the vehicle– Vehicle weight and loading– Vehicle specific driving resistance at different speeds– Transmission properties etc.

Evaluation of in-use vehicle emissions presents a problem– Dismounting engines from in-use vehicles for testing is costly

Do the standardized engine test cycles represent real-life driving?– Complete vehicle testing easily enables comparison of different

driving patternsThe rationale for testing complete vehicles and VTT’s new heavy-duty emissions laboratory were discussed in detail in Ikonen’spresentation at DEER 2003




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OPERATIONAL REGIMES CERTIFICATION VS. BUS CYCLE




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Road-simulation chassis dynamometer for complete vehicle testing

– In-use vehicle emission performance– Evaluation of different real-life driving cycles– Emission deterioration evaluation along with vehicle aging

Transient type engine dynamometer with fast response– ETC testing– High performance engine testing

Full-flow CVS system– Secondary tunnel– Particle collector

Exhaust emission analyzer set for regulated emissionsWide variety of instrumentation for unregulated emission measurements

HEAVY-DUTY EMISSION LABORATORY AT VTT MAIN COMPONENTS




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HEAVY-DUTY EMISSION LABORATORY AT VTT CHASSIS DYNAMOMETER

Road-simulation chassis dynamometer – Manufacturer Froude Consine Ltd, UK– Roller diameter 2.5 m– Inertia simulation 2 500 - 60 000 kg– Max axle weight 20 000 kg– Max tractive force ±20 000 N (speed

range 0 - 54 km/h)– Max power absorption 300 kW (speed

range 54 - 110 km/h)– Fast and precise IGBT control for good

transient load response– Driver’s Aid with programmable driving

cycles




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National urban bus emission evaluation– Scheduled for 2002 - 2004– Emission factors will be generated for about 35 in-use vehicles– Vehicles represent different age groups, fuels and technologies

– Euro 1 >> Euro 5 / EEV (Environmentally Enhanced Vehicle)– Both diesel and natural gas fuels are included– Diesel buses with and without exhaust aftertreatment– Natural gas buses with aftertreatment, both lean-burn and

stoichiometric– Regulated emissions (CO, THC, NOX, PM) for all vehicles

CITY BUS EMISSION EVALUATION




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Additional IANGV’s assignment with newest-technology CNG and diesel busesMore comprehensive emission analyses:

– Particulate size distribution– Chemical and biological characterization of particulates– Hydrocarbon speciation– Aldehydes– Semivolatiles– Anions (sulfates and nitrates)

IANGV will publish a full reportin October 2004


IANGV




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Bus selection criteria, for the general part:– Most common bus types – Several units of same bus type to evaluate consistency– A few buses repeatedly every year to evaluate ageing/deterioration

Bus selection criteria, for the IANGV part:– Several newest technology NG buses, both lean-burn and stoichiometric– Relevant new diesel counterparts with and without aftertreatment for

reference– Low mileage and flawless condition required





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Fuel Brand Model year Euro class Exhaustaftertreatment

Combustion

diesel C 2003 3 - diesel

diesel C 2003 3 oxicat diesel

diesel C 2003 3 CRT filter diesel

CNG A 2002 3 oxicat lean-burn

CNG B 2002 EEV oxicat lean-burn

CNG D 2003 EEV TWC lean-mix*)

CNG E 2004 EEV TWC stoichiom.

*) combination of stoichiometric and lean-burn combustion

VEHICLES/IANGV BUS STUDY




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Driving cycles– Braunschweig bus cycle (European)– Orange County bus cycle (US, SAE J2711)

Vehicle loading– Tests with half-loaded vehicles, some checkpoints unloaded

Test fuels– Ultra low sulphur commercial diesel– Natural gas of high methane content (98 %), sulphur free (no odorant)

CITY BUS EMISSION EVALUATION , METHODOLOGY




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CITY BUS EMISSION EVALUATION, METHODOLOGY

Braunschweig urban bus cycle– duration 1740 s– length 10.873 km– average speed 22.5 km/h– max speed 58.2 km/h

share of idle 25% Braunschweig Bus Cycle

0

10

20

30

40

50

60

70

0 200 400 600 800 1000 1200 1400 1600 1800

Time (s)

Spee

d (k

m/h

)




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CITY BUS EMISSION EVALUATION, METHODOLOGY

Orange County bus cycle– duration 1909 s– length 10.526 km– average speed 19.9 km/h– max speed 65.4 km/h– share of idle 21% Orange County Bus cycle

0

10

20

30

40

50

60

70

0 500 1000 1500 2000

Time (s)

Spee

d (k

m/h

)




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CITY BUS EMISSION EVALUATIONRESULTS

NOx and PM emissions over the Braunschweig city bus -cycle

0

5

10

15

20

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

PM g/km

NO

x g/

km

Diesel Euro 1Diesel Euro 2Diesel Euro 3Diesel + CRT Euro 2 & 3CNG Euro2CNG Euro3CNG EEVEuro limits (by factor 1.8)

Euro 1Euro 2Euro 3

Euro 4

Euro 5 / EEV




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NOx and PM emissions over the Braunschweig city bus -cycle

0

5

10

15

20

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

PM g/km

NO

x g/

km

Diesel Euro 1Diesel Euro 2Diesel Euro 3Diesel + CRT Euro 2 & 3CNG Euro2CNG Euro3CNG EEVEuro limits (by factor 1.8)

Euro 1Euro 2Euro 3

Euro 4

Euro 5 / EEV

CNG EEV

Diesel Euro 3

CRT Euro 2 & 3

CNG Euro 3

Diesel Euro 2

CNG Euro 2defective CRT's




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NOx emissions vs. Euro-levels in Braunschweig city bus -cycle

0

5

10

15

20

25

Euro emission level

g/km

DieselDiesel + CRTCNGCNG EEV LBCNG EEV LMCNG EEV SMEuro limits (by factor 1.8)




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PM emissions vs. Euro-levels in Braunschweig city bus -cycle

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Euro emission level

g/km

DieselDiesel + CRTCNGCNG EEV LBCNG EEV LMCNG EEV SMEuro limits (by factor 1.8)




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NOx and CO2 emissions over the Braunschweig city bus -cycle

0

5

10

15

20

900 1000 1100 1200 1300 1400 1500 1600 1700

CO2 g/km

NO

x g/

km

Diesel Euro 1

Diesel Euro 2

Diesel Euro 3

Diesel + CRT Euro 2 & 3

CNG Euro2

CNG Euro3

CNG EEV




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NOx and CO2eqv emissions over the Braunschweig city bus -cycle

0

5

10

15

20

900 1000 1100 1200 1300 1400 1500 1600 1700

CO2 g/km

NO

x g/

km

Diesel Euro 1

Diesel Euro 2

Diesel Euro 3

Diesel + CRT Euro 2 & 3

CNG Euro2

CNG Euro3

CNG EEV

CO2eqv = CO2 + 21 * CH4




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CO EMISSIONS/IANGV MATRIX

CO emissions (g/km)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Euro 3 Diesel Euro 3 Diesel +OC Euro 3 Diesel+CRT

Euro 3 LB CNG+OC

EEV LB CNG +OC EEV LM CNG+TW/OC

EEV SM CNG+TW

g/km

BrauschweigOrange County




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THC EMISSIONS/IANGV MATRIX

THC emissions (g/km)

0.0

0.5

1.0

1.5

2.0

2.5

Euro 3 Diesel Euro 3 Diesel +OC Euro 3 Diesel+CRT

Euro 3 LB CNG+OC

EEV LB CNG +OC EEV LM CNG+TW/OC

EEV SM CNG+TW

g/km

BraunschweigOrange County




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HC EMISSIONS/IANGV MATRIX

HC emissions over the Braunschweig cycle (g/km)

0.0

0.5

1.0

1.5

2.0

2.5

Euro 3 Diesel Euro 3 Diesel+OC

Euro 3 Diesel+CRT

Euro 3 LB CNG+OC

EEV LB CNG+OC

EEV LM CNG+TW/OC

g/km

Methane

NMHC




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NOx EMISSIONS/IANGV MATRIX

NOx emissions (g/km)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0


Euro 3 Diesel+CRT

Euro 3 LB CNG+OC

EEV LB CNG+OC

EEV LM CNG+TW/OC

EEV SM CNG+TW

g/km





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PM EMISSIONS/IANGV MATRIX

PM emissions (g/km)

0.00

0.05

0.10

0.15

0.20

0.25


Euro 3 Diesel+CRT

Euro 3 LB CNG+OC

EEV LB CNG+OC

EEV LM CNG+TW/OC

EEV SM CNG+TW

g/km





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ALDEHYDE EMISSIONS/IANGV MATRIXAldehydes (g/km, Braunschweig)

0

5

10

15

20

25

30

35

40

Euro 3 Diesel Euro 3 Diesel +OC Euro 3 Diesel +CRT Euro 3 LB CNG +OC EEV LB CNG +OC EEV LM CNG+TW/OC

mg/

km

FAAA




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Particle size distribution over Br and Or test (ELPI)

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

0.01 0.10 1.00 10.00Aerodynamic Dp [µm]

dN/d

logD

p [#

/test

]

Euro 3 Diesel / BrEuro 3 Diesel / OrEuro 3 Diesel + OC / BrEuro 3 Diesel + OC / OrEuro 3 Diesel + CRT / BrEuro 3 Diesel + CRT / OrEuro 3 LB CNG + OC / BrEuro 3 LB CNG + OC / OrEEV LB CNG + OC /BrEEV LB CNG 0 OC / OrEEV LM CNG + TW/OC / BrEEV LM CNG + TW/OC / Or

DIESEL,DIESEL + OC

DIESEL + CRTCNG

PARTICLE NUMBER SIZE DISTRIBUTION/IANGV MATRIX




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AMES MUTAGENICITY/IANGV STUDY

0

20

40

60

80

100

120

140

160

180

Euro 3 Euro 3 DOC Euro 3 CRT CNG LB

PM mg/kmAMES rev/mg/10AMES krev/km




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Relative emissions, worst result = 100%Brauschweig cycle

0 %

50 %

100 %

PAH car.

NMHC

NOx

NO2

CO2Ames

FA

PM

PM#

Euro 3 Diesel

Euro 3 Diesel +CRT

CNG EEV


Items evaluated:

Carcinogenic PAHsNMHCNOx

NO2 (tailpipe)CO2

Ames mutagenicityFormaldehyde (FA)Particle mass (PM)Particle numbers (PM#)

COMPARISON DIESEL, DIESEL + CRT, CNGIANGV STUDY




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CITY BUS EMISSION EVALUATION,CONCLUSIONS

Both NOX and PM emissions decrease along with newer Euro standards– “real life” emission trends point steadily downwards – exceptions can be found as certain bus models don’t follow the general trend

Results of older Euro 1 and Euro 2 buses spread significantly more than newer Euro 3 results

– higher mileage and inaccurate fuel metering in transient situations

Good and bad results for CRT buses– in some cases poor maintenance or failures caused CRT inactiveness– fully working devices give good results, even in the case of high mileage Euro

2 buses

No significant difference in aggregate CO2 emissions between diesel and natural gas buses

– diesels consume less energy– CNG vehicles benefit from fuel chemistry




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CITY BUS EMISSION EVALUATION,CONCLUSIONS

PM emissions of natural gas buses are extremely low– independent of technology and mileage

Stoichiometric NG combustion gives both lowest NOx and CO2 values– generally lean-burn combustion is claimed to be more fuel efficient– great differences in fuel consumption between different CNG buses

Significant spread in THC emissions of CNG vehicles – moderate THC emissions for new CNG vehicles– high THC emissions for old CNG buses with ineffective catalysts– NMHC part low for all CNG vehicles

Practically all CNG buses in Europe are catalyst equipped– excellent performance regarding unregulated emissions and exhaust toxicity– in this respect, the results of the IANGV study differ from many North

American studies




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ACKNOWLEDGEMENTS - SPONSORSSponsors

– Helsinki Metropolitan Area Council (YTV)– Helsinki City Transport Planning Department (HKL)– Ministry of Transport and Communications, Finland– Gasum Oy (the Finnish natural gas company)– the Swedish National Road Administration (Vägverket)– International Association of Natural Gas Vehicles (IANGV)– Vehicles supplied by transport companies and

manufacturers

IANGV

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