VTT TECHNICAL RESEARCH CENTRE OF FINLAND TRANSIT BUS EMISSION STUDY COMPARISON OF EMISSIONS FROM DIESEL AND NATURAL GAS BUSES Nils-Olof Nylund & Kimmo Erkkilä VTT PROCESSES 1 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND THE FINNISH NATIONAL BUS PROJECT 2002-2004 � VTT performed more than 200 emission measurements with 34 different buses � Some vehicles were subjected to a follow-up program to study emission stability and deterioration � Variables in the study were, among others: – vehicle certification class (Euro 1 to Euro 5/EEV) – vehicle mileage – fuel (diesel, natural gas) – duty cycle (Braunschweig bus cycle, ECE, Orange Country) – vehicle load VTT PROCESSES 2 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND OBJECTIVES OF THE EXPANDED WORK ON CNG BUSES � To provide unbiased emission data on current diesel and CNG vehicles – extensive emission analysis � Diesel buses – Euro 3 without after-treatment – Euro 3 with oxidation catalyst – Euro 3 with OEM installed CRT � Natural gas buses (catalyst equipped) – Euro 3 lean-burn – EEV lean-burn – EEV lean-mix (combination of λ = 1 and lean-burn) – EEV stoichiometric ( λ = 1) VTT PROCESSES 3 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND CHASSIS DYNAMOMETER TESTING Braunschweig Bus Cycle 70 60 50 Speed (km/h) 40 30 20 10 0 0 200 400 600 800 1000 1200 1400 1600 1800 Time (s) Orange County Bus cycle 70 60 50 Speed (km/h) 40 30 20 10 0 0 500 1000 1500 2000 Time (s) VTT PROCESSES 4 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND NO x vs. PM FOR TOTAL BUS MATRIX NOx and PM emissions over the Braunschweig city bus -cycle Diesel Euro 1 20 Diesel Euro 2 Brand A Diesel Euro 3 Diesel + CRT Euro 2 & 3 Brands A&B CNG Euro2 Brand B CNG Euro3 15 CNG EEV Brand A Euro limits (by factor 1.8) Brand C NOx g/km Brand C 10 Brand A Brand A Brand C Brand B 5 Euro 4 Brands D&E Euro 5 / EEV Euro 3 Euro 1 Euro 2 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 PM g/km VTT PROCESSES 5 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND NO x TREND NOx emissions vs. Euro-levels in Braunschweig city bus -cycle Diesel 25 Diesel + CRT CNG CNG EEV LB CNG EEV LM CNG EEV SM 20 Euro limits (by factor 1.8) 15 g/km 10 5 0 Euro emission level VTT PROCESSES 6 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND PM TREND PM emissions vs. Euro-levels in Braunschweig city bus -cycle Diesel Diesel + CRT CNG 0.6 CNG EEV LB CNG EEV LM CNG EEV SM Euro limits (by factor 1.8) 0.5 0.4 g/km 0.3 0.2 0.1 0.0 Euro emission level VTT PROCESSES 7 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND PARTICLE NUMBERS Particle size distribution over Br and Or test (ELPI) 1.E+16 DI Euro III - Br DI Euro III - Or DI Euro III OC - Br DI Euro III OC - Or DI Euro III CRT - Br 1.E+15 DI Euro III CRT - Or CNG Euro III OC - Br CNG Euro III OC - Or CNG1 EEV OC - Br CNG1 EEV OC rep. - Br CNG1 EEV OC - Or 1.E+14 CNG2 EEV TW/OC - Br CNG2 EEV TW/OC - Or CNG EEV SM TW - Br dN/dlogDp [#/test] DIESEL, 1.E+13 DIESEL + OC 1.E+12 SM CNG 1.E+11 1.E+10 DIESEL + CRT CNG 1.E+09 0.01 0.10 1.00 10.00 Aerodynamic Dp [µm] VTT PROCESSES 8 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND DIESEL CRT vs LEAN-MIX CNG Relative emissions, worst result = 100% Brauschweig cycle Items evaluated: PAH car. Euro 3 Diesel � Carcinogenic PAHs 100 % NMHC FA � NMHC � NO x 50 % � NO 2 (tailpipe) � CO 2 PM# Ames � Ames mutagenicity 0 % � Formaldehyde (FA) � Particle mass (PM) � Particle numbers (PM#) PM NO2 CO2 NOx VTT PROCESSES 9 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND DIESEL CRT vs LEAN-MIX CNG Relative emissions, worst result = 100% Brauschweig cycle Items evaluated: Euro 3 Diesel PAH car. Euro 3 Diesel +CRT � Carcinogenic PAHs 100 % NMHC FA � NMHC � NO x 50 % � NO 2 (tailpipe) � CO 2 PM# Ames � Ames mutagenicity 0 % � Formaldehyde (FA) � Particle mass (PM) � Particle numbers (PM#) PM NO2 CO2 NOx VTT PROCESSES 10 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND DIESEL CRT vs LEAN-MIX CNG Relative emissions, worst result = 100% Brauschweig cycle Items evaluated: PAH car. Euro 3 Diesel Euro 3 Diesel +CRT 100 % � Carcinogenic PAHs CNG EEV LM NMHC FA � NMHC � NO x 50 % � NO 2 (tailpipe) � CO 2 PM# Ames � Ames mutagenicity 0 % � Formaldehyde (FA) � Particle mass (PM) � Particle numbers (PM#) PM NO2 CO2 NOx VTT PROCESSES 11 Captive Fleets 14.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND CONCLUSIONS � On average, CNG delivers better emission performance than CRT equipped diesel � Exhaust from advanced CNG vehicles was found less toxic than exhaust from CRT diesel � Total numbers of particles and nanoparticles with CNG are similar to CRT diesel � How will new diesel technology perform? VTT PROCESSES 12 Captive Fleets 14.1.2005
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