on-road measurement of emissions of reactive nitrogen ... · vojtisek et al.: 16on-road measurement...

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


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.


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


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


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


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


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)


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?


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.


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


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)


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]


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.


15

ADAC tests:

EU diesel cars produce more NOx during WLTC

than during NEDC


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


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


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


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


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)


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


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


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


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


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


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


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


r2=0.956 r2=0.961


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


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



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


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


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


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 ???


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”.


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


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

on-road measurement of emissions of reactive nitrogen ... · vojtisek et al.: 16on-road measurement...

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