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Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
1
On-road measurement of emissions of reactive nitrogen compounds and
greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR
Michal Vojtíšek, Vít Beránek, Vojtěch Klír Center for Vehicles for Sustainable Mobility, Czech Technical University in Prague
Petr Jindra, Martin Pechout Czech University of Life Sciences in Prague
Tomáš Voříšek, SEVEn s.r.o.
[email protected] - tel. (+420) 774 262 854 – www.medetox.cz
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
2
Particulate matter and tropospheric
ozone are causing over 400 thousands
of premature deaths annually in the
EU (vehicle accidents less than 40 thousands/year)
Internal combustion engines are among cleanest
combustion devices. But they do not have chimneys,
and they are not far outside of the cities.
They are among us in the streets where we inhale.
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
3 U Tesca, rozjezd busu nestandardní palivo
35
56
21
31
33
9
77
114
25
3 3
2
15 11
29
27
43
29
30
67
7
30
16 55
13
171
89
492 127
161
50.191
50.192
50.193
50.194
50.195
14.491 14.493 14.495 14.497 14.499 14.501 14.503 14.505 longitude (E)
lati
tud
e
(N)
Morning rush hour May 15
Smoking vehicles
Lawn mowing
Total particle counts, 10-500 nm thousands of particles per cm3
Líbeznice, 15. 5. 2014, morning rush hour
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
4
Euro 6 HDV limit:
5 mg/kWh ~ 0,6 mg/m3
Particles are measured by mass or by count, just like we sell fruits and vegetables – it is
difficult to measure by other parameters, even though they may be more relevant.
Czech limit for local heating up
to 300 kW (Reg. 201/2012, appendix 10)
125-150 mg/m3 from 1.1.2014
60-75 mg/m3 from 1.1.2018
Euro 6 bus - 1 km of travel
~ 1 mg PM ~ 1 cigarette
Emission limits in broader perspective
Locomotive exhaust (this one
CNG, diesel with DPF
looks similar)
Home heating stove
chimney
Burning of trash ~ 500 mg/m3 Christian et al., Atmos. Chem. Phys., 10, 565–584, 2010
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
5
Problematic pollutants in engine exhaust
• Particles + secondary aerosol
• NOx + tropospheric ozone
• CO, benzene, lead – no longer a problem
New and emerging problems:
• NO2 - formation in oxidation catalysts
• NH3 - formation in reduction catalysts
• - formation in three-way catalysts when run rich
• Aldehydes – oxygenated fuels (ethanol)
Greenhouse gases
• N2O - NOx reduction catalysts (SCR, LNT)
• CH4 - natural gas engines, LNT catalyst
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
6
Natural gas as the “clean fuel”
• Mostly methane (ethane, hydrogen, nitrogen, CO2)
• Can be produced from biomass (biomethane)
• Relatively safe fuel (stable, low health risks, high ignition energy)
• Stored compressed (CNG) or liquified (LNG)
• Combustion produres some nanoparticles, nitrogen oxides, aldehydes,…
• High-temperature processes in engines lead to formation of NOx
• Any engine produces nanoparticles from lubricating oil
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
7
Natural gas as the “clean fuel”
• Early CNG engines much cleaner (Holmén and Ayala, 2002) and lower toxicity (Turrio-Baldassarri et al., 2006) than diesel
• But diesel with DOC/DPF better than natural gas with no aftertreatment (Kado et al., 2005)
• „State of the art“ CNG: optimized compression ratio, stoichiometric air-fuel ratio, three-way catalyst no problem
• “State of the art” diesel: DOC/DPF/SCR/ammonia slip catalyst no problem (Hesterberg 2011)
• When state of the art compared, not much difference CNG-diesel (Nylund et al., 2004), (Hesterberg et al., 2008)
With advanced engine and aftertreatment technologies, are the differences attributable to fuel merely academic?
Is state of the art the reality?
– In the EU, maybe not !!! (i.e., DieselGate)
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
9
Euro 5 with no DPF (Prague, CZ)
EURO 5 – DOC, DPF (particle filter), no SCR2012 Iveco Daily, 3.0-liter Iveco engine
Emissions of particulate matter very low even during 1-hour idle and generally well below 1 mg/m3
EURO 5 – DOC, DPF (particle filter), no SCR2012 Iveco Daily, 3.0-liter Iveco engine
Emissions of particulate matter very low even during 1-hour idle and generally well below 1 mg/m3
With DPF
Is diesel PM becoming more of a question of public policy
rather than technology?
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
10
Real-world emissions could be higher than during „standardized tests“
(i.e., type approval)
• Optimization for type-approval conditions
– No EGR at full load
– Catalyst sized for low flow and too small for high loads
• Technology limits
- low SCR temperature – cold start, creep
• Malfunction & deterioration
• „No one is watching“
– Switching off EGR, LNT fuel / SCR urea injection
– „Cycle beating“ strategy
– DPF removal, SCR deactivation, etc.
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
11
„DieselGate“: NEDC cold („test mode”, EGR, low Nox) vs. hot (non-test mode, less EGR, more NOx
(VW Passat, Euro 5, measured by the authors for a BBC documentary)
0
0.5
1
1.5
2
2.5
3
3.5
0 200 400 600 800 1000 1200
g N
Ox
(N
O+
NO
2)
-20
0
20
40
60
80
100
1201600 1800 2000 2200 2400 2600 2800
km
/h
NEDC-cold-NOx
NEDC-hot-NOx
road speed
0
100
200
300
400
500
600
700
800
100 300 500 700 900 1100 1300
pp
m N
Ox
(N
O+
NO
2)
-40000
-20000
0
20000
40000
60000
80000
100000
120000
pp
m
CO
2
NEDC-4WD-hot-NOx NEDC-4WD-cold-NOx NEDC-4WD-cold-CO2 NEDC-4WD-hot-CO2
Euro 5 limit
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
12
10
100
1000
18:0
3 - N
EDC
18:2
7 - N
EDC
19:3
6 - 3
xEUDC
08:0
4 - N
EDC
08:5
2 - N
EDC
10:0
5 - N
EDC
10:3
0 - A
rtem
is (e
ntire
cycl
e)
11:3
2 - 3
xEUDC
08:0
2 - N
EDC
08:5
1 - N
EDC
10:1
1 - N
EDC
12:0
8 - 2
xEUDC
12:2
6 - N
EDC
12:5
8 - W
LTP
08:2
6 - N
EDC cold
NO
x [
mg
/km
]
Euro 6 limit
NEDC cycle
80 mg/km
Vehicle
driven
outside
Different
preconditioning
cycle
Legislative
test sequenceHot start
NEDC
8352 64 67
4360 66 69
267 297
37
214146
89170
72
1838
3042
756
364
707
10
100
1000
10000
18:0
3 - N
EDC
18:2
7 - N
EDC
19:3
6 - 3
xEUDC
08:0
4 - N
EDC
08:5
2 - N
EDC
10:0
5 - N
EDC
10:3
0 - A
rtem
is (e
ntire
cycl
e)
11:3
2 - 3
xEUDC
08:0
2 - N
EDC
08:5
1 - N
EDC
10:1
1 - N
EDC
12:0
8 - 2
xEUDC
12:2
6 - N
EDC
12:5
8 - W
LTP
08:2
6 - N
EDC cold
08:5
8 - E
CE 1
08:5
8 - E
CE 2
10:2
3 - E
UDC 1
10:2
9 - E
UDC 2
10:3
5 - E
UDC 3
10:4
5 - N
EDC
11:0
6 - N
EDC-160
NO
x [
mg
/km
]
Cold start
NEDCHot
start
NEDC
3x
EUDC
soak
Cold
start
NEDC
Vehicle
driven
outside
Legislative
test sequence
Hot
start
NEDC
Hot
start
NEDC
3x
EUDC
soak
Cold
start
NEDCHot
start
NEDC
Hot
start
NEDC
WLTPArtemis
CADC
„DieselGate“: Cooling of the ambient air sensor during preconditioning triggers “high NOx” operation during subsequent test cycle …
(Opel Zafira 1.6 CDTi, MY 2015, Euro 6, measurement for WHR documentary)
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
13
<- WLTC cycle
NOx concentrations in
the exhaust increase at higher speeds and loads
than those experienced in
NEDC
Opel Zafira diesel, MY 2015, Euro 6
<- CADC cycle (Artemis)
0
100
200
300
400
500
600
700
800
0 300 600 900 1200 1500 1800 2100 2400 2700 3000 3300
NO
+N
O2
(N
Ox
) [p
pm
]
0
20
40
60
80
100
120
140
1601 8 7 0 2 3 7 0 2 8 7 0 3 3 7 0 3 8 7 0 4 3 7 0 4 8 7 0 5 3 7 0
ro
ll s
peed
[k
m/h
]
NOx [ppm] in raw exhaust
v Front left [km/h]
WLTP - Nov 12, 12:58
0
100
200
300
400
500
600
700
0 200 400 600 800 1000 1200 1400 1600 1800
NO
x r
aw
[p
pm
]
0
20
40
60
80
100
120
140
roll s
peed
[k
m/h
]
NOx [ppm] in raw exhaust - FTIR
v Front left [km/h]
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
14
Automobil, r.v. 2015, Euro 5, naftový motor s LNT
Vysoké zatížení – vyšší emise NOx i částic
0
100
200
300
400
500
600
700
800
13:40 13:45 13:50 13:55 14:00 14:05 14:10 14:15 14:20 14:25 14:30 14:35 14:40
NO
[ppm
], C
H4 [ppm
]
0
15
30
45
60
75
90
105
120
CO
2 [%
], N
2O
[ppm
]
CH4 [ppm]
NOx [ppm]
N2O [ppm]
CO2 [%]
regenerace LNT
-75-60
-45-30
-150
15
3045
6075
rych
lost [k
m/h
]
-2-1
01
234
56
78
zry
ch
len
í [m
/s2]
absence regenerace LNT
= vyšší NOx
Při dynamičtější jízdě nedocházelo k regeneraci zásobníkového katalyzátoru („úspora paliva“?) a emise NOx byly výrazně vyšší.
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
15
ADAC tests:
EU diesel cars produce more NOx during WLTC
than during NEDC
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
16
Diesel car NOx limit: 180 mg/km Euro 5, 80 mg/km Euro 6
Average emissions - Braunschweig cycle: 195 mg/km NOx. At 37 liters / 100 km, 220 g/kWh: 162 mg/kWh (Euro 6: 460 mg/kWh)
Diesel car real driving NOx: Euro 3-5: 1000 mg/km
One Euro 5 car = 1000 mg/km = 5 buses !!!
But 5 buses can transport 100x more people.
SOR CN12 Euro 6 diesel bus – Hradčany military airport
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
17
NO, NO2, N2O, NH3, ...., CO, CO2, PM
1
10
100
1000
10000
14.30 14.50 15.10 15.30 15.50 16.10 16.30 16.50 17.10 17.30 17.50
CH4 (ppm)
NO (ppm)
NH3 (ppm)
0
20
40
60
80
100
120
140
14:14:00 14:19:00 14:24:00 14:29:00 14:34:00 14:39:00 14:44:00 14:49:00
sp
eed
[km
/h
], f
uel
[dm
3/h
]
-30
-20
-10
0
10
20
30
40
N2
O,
NO
, N
O2
[mg
/s]
fuel-from-ECU [dm3/h] fuel-from-CO2 [dm3/h]actual speed [km/h] prescribed speedNO [mg/s] NO2 [mg/s]N2O [mg/s]
diesel: N2O vs. NOx
Higher mileage CNG with miscalibration or malfunction: CH4, NO, NH3 !
SOR CN12 Euro 6 diesel bus – Hradčany military airport
21.6.2017 M. Vojtisek et al.: Measurement of particle emissions from small engines during real-world
operation using simple on-board (or off-board) monitoring systems 18th ETH Conference on Combustion Generated Nanoparticles, Zurich, CH, June 22-25, 2014
18
0 10 20 30 40 50 60
NEDC
Artemis urban
& rural
WLTP
US06
Artemis
motorway 130
Artemis
motorway 150
PM mass [mg/km]
direct injection 20 K km
port injection 30 K km
WLTP is “not as lame as NEDC”, but does it cover the problem – enrichment at high load (prohibited by EPA)?
US06 and Artemis motorway cycles as a supplement?
EURO 5 PM mass limit
Gasoline engine PM: Choice of cycles
EURO 5 PN limit
Answer to Imad Khalek’s question on PN from PFI
From Vojtisek-Lom, ETH 2014
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
19
Study goals
What is the real emissions benefit of switch to natural gas on exhaust emissions?
• This study: light utility vehicles, Euro 6 – Harder to replace by public and non-motorized transport – 4 x diesel, 4 x CNG (1 station wagon + 3 vans each fuel) – 1 van with non-functional DPF replaced – Comprehensive laboratory and on-road evaluation
• On the road: – Urban route in Prague (21 km) – Composite route outside of Prague (65 km) – Nanoparticles, reactive nitrogen NO, NO2, NH3,
greenhouse gases N2O, CH4, CO2, aldehydy
• Laboratory: – NEDC, WLTP, Artemis (CADC), NYCC, US06 cycles – Particle size distributions, offline analysis of PAH
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
20
Vehicles
Case for EU light-duty utility vehicles: Similar type approval as cars
Cars can be replaced by electric, non-motorized, public transit Heavy trucks can be routed to rail
Light utility vehicles are difficult to replace …
Mileage Fuel Test
weight Model Engine
Model
year [km]
All CNG factory
& dual-fuel [kg]
Škoda Octavia 1,6 TDI CR DPF/81 kW 2014 42 567 Diesel 1 594
Škoda Octavia 1,4 TSI G-TEC/81 kW 2015 21 293 CNG (Gasoline) 1 683
OPEL Zafira 2.0 CDTI ecoFLEX /96 kW 2014 27 201 Diesel 2 070
VW Touran 1,4 TSI EcoFuel/110 kW 2014 68 343 CNG (Gasoline) 2 039
VW Caddy 1,6 TDI/75 kW *Euro 5* 2014 39 434 Diesel 1 886
VW Caddy 2,0 MPI EcoFuel/80 kW 2014 60 102 CNG (Gasoline) 1 910
Fiat Doblo 1,6 MultiJet/77 kW 2016 489 Diesel 1 772
Fiat Doblo 1,4 T-Jet/88 kW 2016 10 417 CNG (Gasoline) 1 682
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
21
On-board instrumentation
• Gaseous compounds: FTIR & MiniPEMS • Particles: NanoMet3 • Operating data: EOBD • Poloha: GPS
FTIR spectrometer
• Nicolet Antaris IGS
• 5 m path length, 130°C
• 0.5 cm-1, 1 Hz resolution
• ZnSe optics, 4000-650 cm-1
NanoMet3
• Diffusion classifier, detection by electrometer
• Output correlated with particle number (PN) per Euro 6 (PMP, non-volatile particles detected at 50% efficiency at 23 nm)
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
22
Low-cost on-board system overview (Vojtisek-Lom and Cobb, CRC On-road vehicle emissions workshop, 1998)
Engine
Measured concentrations HC, CO, CO2, NO,
particulates
Time shift (delay) Determined experimentally
Mass air flow, intake air pressure and temperature, engine rpm, vehicle speed,
engine temperatures
ECU
Direct measurement
Diagnostic interface
ηvol * Mair * pintake * ω * displacement Qvzd = ------------------------------------ R * Tintake
GPS – position. Speed, altitude
Time signal
1. Exhaust gas flow calculations 2. Mass emissions = const. x concentration x exhaust flow
3. Fuel consumption = C emissions (PM, HC, CO, CO2) / C in fuel Integrating: Emissions per test, distance, kg of fuel
Data recording
Synchronization of data Harmonization of sample
interval to 1 s
Aft
er-
tr
eatm
em
t
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
23
DetectorDetector
IR SourceIR Source
Fixed mirrorFixed mirror
x 0 -xx 0 -x
BeamsplitterBeamsplitter
Laser diodeLaser diode
HeHe--NeNe laserlaser
SampleSample
Moving mirrorMoving mirror
FTIR (Fourier Transform Infra Red) Spectrometer - measures large portion of infrared spectra
- quantification of compounds absorbing in IR through deconvolution of spectra
NO
NO2 CH4
H2O
CO2 CO
NH3
Different HC
H2O CO2
Diagram: Nicolet
- greenhouse gases CO2, CH4, N2O - reactive nitrogen compounds NO, NO2, NH3, HCN, HCNO - various heterogeneous molecules present in concentrations that can be detected and discerned from other compounds - this study: MCT detector, ZnSe optics, 0.5 cm-1 resolution, 6 m path length, 130°C
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
24
On-board FTIR packages Both liquid nitrogen cooled MCT detector, ZnSe optics,
130 C sampling train, 0.5 cm-1 optical resolution, 4000-650 cm-1
Nicolet Antaris IGS, 70 kg 5 m cell length, 1 s resolution
Midac I-series, 30 kg 6 m cell length, 2.5 s resolution poster #29 –
locomotive emissions
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
25
The “MiniPEMS” (Poor man’s PEMS) concept: Focus on making the test possible & practical. Variances within and among vehicles are often greater
than the uncertainty of simpler instruments
Home-made instrument
CO, CO2, indicative HC: NDIR NO, NO2, O2: electrochemical
Indicative PN: Ionization chamber
Intake air flow: calculated from engine rpm, intake
air pressure and temperature Position and speed: GPS
Exhaust gas temp: thermocouple
LiFeYPO battery, 3 hours runtime 9 kg, 40x22x22 cm
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
26
Nanomet
(particles)
FTIR
(gases)
Particle classifiers
ELPI (aerodynamic)
EEPS (electric mobility)
Dilution tunnel 10 m3/min
High volume sampler
Digitel, 500 lpm
Laboratory tests
High volume sampler
Digitel, 500 lpm
PN-PMP
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
27
On-board system validation
0
100
200
300
400
500
600
700
800
900
0 100 200 300 400 500 600 700 800 900
CVS Horiba CO [mg/km]
FT
IR C
O [
mg/k
m]
Octavia TSI
Octavia TDI
Octavia CNG
VW Caddy TDI
Fiat Doblo Euro 5
Fiat CNG
VW Touran CNG
1
10
100
1000
1 10 100 1000
CVS Horiba HC [mg/km]
FT
IR H
C [
mg/k
m]
(sum
of analy
zed c
om
pounds)
Octavia TSI
Octavia TDI
Octavia CNG
VW Caddy TDI
Fiat Doblo Euro 5
VW Touran CNG
Fiat CNG
On-board system:
concentrations in raw exhaust measured by FTIR
exhaust flow calculated (speed-density method)
Laboratory: Diluted exhaust (CVS), traditional on-line measurements
Each point plotted = emissions per cycle Agreement requires correct a) concentration, b) flow, c) synchronization
CO
FID vs. FTIR sum of analyzed HC
Vojtisek-Lom et al., Sci. Tot. Env (in review)
r2=0.722
r2=0.747
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
28
1
10
100
1000
10000
1 10 100 1000 10000
CVS Horiba NOx [mg/km]
FT
IR N
Ox [
mg/k
m]
Octavia TSI
Octavia TDI
Octavia CNG
VW Caddy TDI
Fiat Doblo Euro 5
VW Touran CNG
Fiat CNG
1
10
100
1000
10000
1 10 100 1000 10000
CVS Horiba NOx [mg/km]
FT
IR N
O [
mg/k
m]
Octavia TSI
Octavia TDI
Octavia CNG
Fabia CNG
VW Caddy TDI
Fiat CNG
Fiat Doblo Euro 5
VW Touran CNG
NOx FTIR NO vs. NOx
On-board system validation On-board system:
concentrations in raw exhaust measured by FTIR
exhaust flow calculated (speed-density method)
Laboratory: Diluted exhaust (CVS), traditional on-line measurements
Each point plotted = emissions per cycle Agreement requires correct a) concentration, b) flow, c) synchronization
Vojtisek-Lom et al., Sci. Tot. Env (in review)
r2=0.956 r2=0.961
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
29
High NO2 & high NO2/NOx
The reference method – chemiluminescence – may have limitations
– NO2 loss to condensate ? inefficient conversion NO2 NO ?
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0 1 2 3 4 5 6 7 8
CVS Horiba NOx/CO2
FT
IR N
Ox/C
O2
Octavia TSI
Octavia TDI
Octavia CNG
VW Caddy TDI
Fiat CNG
Fiat Doblo Euro 5
VW Touran CNG
Fiat Doblo Euro 5 NO
VW Caddy Diesel NO
FTIR NOx vs. CLD NOx
FTIR NO vs. CLD NOx
FTIR m
g NO,N
Ox /
g C
O2
CVS mg NOx / g CO2
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
30
1E+08
1E+09
1E+10
1E+11
1E+12
1E+13
1E+14
1E+15
1E+08 1E+09 1E+10 1E+11 1E+12 1E+13 1E+14 1E+15
CVS PN PMP [#/km]
NanoM
et
PN
[#/k
m]
Octavia TSI
Octavia TDI
Octavia CNG
VW Caddy TDI
Fiat CNG
Fiat Doblo Euro 5
VW Touran CNG
Fiat Doblo 6
Total number of non-volatile particles (PN) NanoMet3 – raw exhaust, relies on calculated exhaust flow and data synchronization; diffusion charger measures approximately total particle length (different principle); correlation with PN (PMP) established on diesel vehicles (EC Joint Research Center)
Direct injection gasoline
Van without functional
DPF
Euro 6 interim limit for DISI 6x1012 #/km
Euro 6 limit
6x1011 #/km
Vojtisek-Lom et al., Sci. Tot. Env (in review)
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
31
0
200
400
600
800
1000
1200
1400
1600
Škoda
Octavia
Diesel
Opel
Zafira
Diesel
VW
Caddy
Diesel
Fiat
Doblo
Diesel
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
NO
X [
mg/
km]
Art urban Lab Cold
Art urban Lab Hot
On-road urban Cold
On-road urban Hot
0
5
10
15
20
25
30
35
40
45
50
Škoda
Octavia
Diesel
Opel
Zafira
Diesel
VW
Caddy
Diesel
Fiat
Doblo
Diesel
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
NH
3 [
mg/
km
]
Art urban Lab Cold
Art urban Lab Hot
On-road urban Cold
On-road urban Hot
NOx: CNG – NOx in tens of mg/km
Diesel – consistently in hundreds of mg/km
NH3: Diesel – negligible, CNG – several tens of mg/km
Ammonia contributes to secondary PM formation (but how severe are the health effects?)
NH3
NOx
NOy - Artemis urban vs. urban on-road
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
32
In this test, NEDC run not „as per type approval“,
but with a hot start (engine at operating temperature).
Results vary… (limits: EU 6 cars: 80 mg/km, EU 5 (Caddy) 180 mg/km)
NOx – What about NEDC?
0
200
400
600
800
1000
1200
1400
1600
Škoda
Octavia
D
Opel
Zafira
D
VW
Caddy
D
Fiat
Doblo
D
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
NO
X [mg/
km]
Art urbanArt ruralArt motorwayNEDCWLTPUS06NYCC
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
33
0
200
400
600
800
1000
1200
Škoda
Octavia
D
Opel
Zafira
D
VW
Caddy
D
Fiat
Doblo
D
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
0
200
400
600
800
1000
1200Urban route coldUrban route hotMixed routeArtemis urban coldArtemis urban hotArtemis full cycleUrban route coldUrban route hotMixed routeArtemis urban coldArtemis urban hotArtemis full cycle
Share of NO2 in NOx
CNG – Negligible
(as expected from stoichiometric operation & three-way catalyst)
Diesel – tens of percent (as expected from many types of DOC) Problem: We have as much NO2 as we „expected” to have NOx (when Euro legislation enacted) – NO2 worse than NO – now we have concentrated NO2 in the streets …
NOx
NO2
0
200
400
600
800
1000
1200
Škoda
Octavia
D
Opel
Zafira
D
VW
Caddy
D
Fiat
Doblo
D
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
Art urbanArt ruralArt motorwayNEDCWLTPUS06NYCCArt urbanArt ruralArt motorwayNEDCWLTPUS06NYCC
mg/km NOx
NO2
mg/km NOx
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
34
0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6 7 8
N2
O [
mg/
km]
Art urban Lab Cold
Art urban Lab Hot
On-road urban Cold
On-road urban Hot
0
50
100
150
200
250
Škoda
Octavia
Diesel
Opel
Zafira
Diesel
VW
Caddy
Diesel
Fiat
Doblo
Diesel
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
CH
4 [
mg/
km]
Art urban Lab Cold
Art urban Lab Hot
On-road urban Cold
On-road urban Hot
Greenhouse gases – Artemis urban, urban on-road
N2O CH4
CH4: 28x higher 100-yr global warming potential vs. CO2 (IPCC)
CNG – corresponds to < 1 g/km CO2
Diesel – essentially limited to DPF and LNT regeneration
N2O: 265x higher 100-yr global warming potential vs. CO2 (IPCC)
Diesel – corresponds to several g/km CO2e, CNG – negligible
??? Will diesel N2O increase once SCR will be really put to work ???
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
35
0
200
400
600
800
1000
1200
1400
1600
Škoda
Octavia
Diesel
Opel
Zafira
Diesel
VW
Caddy
Diesel
Fiat
Doblo
Diesel
Škoda
Octavia
CNG
VW
Touran
CNG
VW
Caddy
CNG
Fiat
Doblo
CNG
NO
X [
mg/
km]
Art urban Lab Cold
Art urban Lab Hot
On-road urban Cold
On-road urban Hot
On no vehicle, malfunction was indicated or noticed by the test personnel (all with degrees in automotive engineering).
The vehicles were rented from rental fleets and tested as received.
The authors were not in a position to determine whether the malfunction leading to excessive NOx was “unintended” or
deliberately created at the factory or by „aftermarket” tampering.
Legal disclaimer about „excess NOx”
Implications of findings to CNG support policy:
The real benefits of CNG are increased by the „excess” PM caused by non-functional or
absent DPF and by the “excess” NOx caused by the
“current EU diesel car technology”.
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
36
Summary of results (full paper in review at Science of the Total Environment)
0.1
1
10
100
1000
10000
NOx -
diesel
NH3 -
diesel
CH4 -
diesel
N2O -
diesel
NOx -
CNG
NH3 -
CNG
CH4 -
CNG
N2O -
CNG
emis
sio
n r
ates
[m
g.km
-1]
avg.
of
4 v
eh
icle
s, e
rro
r b
ars
= m
in-m
axOn-road urban route - cold startOn-road urban route - hot startDyno - Artemis urban - cold startDyno - Artemis urban - hot start
Vojtisek et al.: On-road measurement of emissions of reactive nitrogen compounds and greenhouse gases from Euro 6 diesel and natural gas vans using an on-board FTIR. ETH Conference on Combustion Generated Nanoparticles 2017
37
Conclusions
• The effects of compressed natural gas (CNG) on emissions addressed.
• Exhaust emissions from 4 diesel and 4 CNG light-duty utility vehicles measured in the laboratory and on the road.
• On-board FTIR used to measure unregulated gaseous pollutants.
• All vehicles – CNG and diesel with DPF – low emissions of non-volatile particles (PN), not clear about nano & volatiles.
• Diesel: non-type-approval NOx order of magnitude higher than Euro 6 limit.
• Diesel: N2O global warming potential equivalent of several g/km CO2.
• CNG: Methane emissions equivalent to < 1 g/km CO2.
• CNG: Non-problematic emissions due to relatively clean burning fuel, stoichiometric air-fuel ratio, three-way catalyst, relatively new engines. Just like with any other engines, quality of design, calibration, maintenance and usage to be monitored and ensured.
Acknowledgments: Measurements funded by the Czech Gas Association. Additional analysis funded by Czech Ministry of Education LO1311.
Instrumentation funded by the Czech Ministry of Education CZ.1.05/2.1.00/19.04.08