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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
1
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
2
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
3
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
4
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
5
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
6
OPERATIONAL REGIMES CERTIFICATION VS. BUS CYCLE
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
7
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
8
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
9
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
10
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
CITY BUS EMISSION EVALUATION
IANGV
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
11
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
CITY BUS EMISSION EVALUATION
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
12
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
13
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
14
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
)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
15
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
)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
16
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
17
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
CNG EEV
Diesel Euro 3
CRT Euro 2 & 3
CNG Euro 3
Diesel Euro 2
CNG Euro 2defective CRT's
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
18
CITY BUS EMISSION EVALUATIONRESULTS
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)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
19
CITY BUS EMISSION EVALUATIONRESULTS
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)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
20
CITY BUS EMISSION EVALUATIONRESULTS
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
21
CITY BUS EMISSION EVALUATIONRESULTS
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
22
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
23
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
24
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
25
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 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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
26
PM EMISSIONS/IANGV MATRIX
PM emissions (g/km)
0.00
0.05
0.10
0.15
0.20
0.25
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
27
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
28
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
29
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
30
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Items evaluated:
Carcinogenic PAHsNMHCNOx
NO2 (tailpipe)CO2
Ames mutagenicityFormaldehyde (FA)Particle mass (PM)Particle numbers (PM#)
COMPARISON DIESEL, DIESEL + CRT, CNGIANGV STUDY
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
31
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
32
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
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
2004 DEER ConferenceAug 28 – Sept 2, Coronado, California, USA
VTT PROCESSESKimmo Erkkilä
33
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