DRAFT v1a 30/11/03
PARTICULATES
Characterisation of Exhaust Particulate
Emissions from Road Vehicles
Deliverable 15:
Relevance of current PM emission standards and further
aspects of particulate properties to be taken into account
Urban’s comments 2003-12-07
Neville, I rely on you to correct my English. Thanks!
Version 1 – 12/2003
A project sponsored by:
I
EUROPEAN COMMISSION
Directorate General Transport and Environment
In the framework of:
Fifth Framework Programme
Competitive and Sustainable Growth
Sustainable Mobility and Intermodality
Contractors
LAT/AUTh:
CONCAWE:
VOLVO:
AVL:
EMPA:
MTC:
TUT:
TUG:
IFP:
AEAT:
JRC:
REGIENOV:
INRETS:
DEKATI:
SU:
DHEUAMS:
INERIS:
LWA:
TRL:
VKA:
VTT
Aristotle University of Thessaloniki, Laboratory of Applied Thermodynamics - EL
CONCAWE, the oil companies' European organisation for environment, health and
safety - B
AB Volvo - S
AVL List GmbH - A
Swiss Federal Laboratories for Material Testing and Research - CH
MTC AB - S
Tampere University of Technology - FIN
Institute for Internal Combustion Engines and Thermodynamics, Tech. University
Graz - A
Institut Français du Pétrole - F
AEA Technology plc - UK
European Commission – Joint Research Centre - NL
REGIENOV - RENAULT Recherche Innovation - F
Institut National de Recherche sur les Transports et leur Securité - F
DEKATI Oy - FIN
Department of Analytical Chemistry, Stockholm University - S
Department of Hygiene and Epidemiology, University of Athens Medical School EL
Institut National de l’ Environment Industriel et des Risques - F
Les White Associates - UK
Transport Research Laboratory - UK
Institute for Internal Combustion Engines, Aachen University of Technology – D
VTT ENERGY – Engine Technology and Energy in Transportation - FI
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Publication data form
1. Framework Programme
2. Contract No
European Commission – DG TrEn, 5th Framework Programme
Competitive and Sustainable Growth
Sustainable Mobility and Intermodality
3. Project Title
2000-RD.11091
4. Coordinator
Characterisation of Exhaust Particulate Emissions from Road Vehicles
(PARTICULATES)
5. Deliverable Title
LAT/AUTh
6. Deliverable No
Relevance of current PM emission standards and further aspects of
particulate properties to be taken into account
7. Deliverable Responsible
8. Language
CONCAWE/Volvo
English
14
9. Publication Date
{December 2003}
10. Author(s)
11. Affiliation
N Thompson, U Wass
CONCAWE, Volvo
12. Summary
{See report summary}.
13. Notes
{Version Notes}.
14. Internet reference
{http://}
15. Key Words
16. Distribution statement
FREE
17. No of Pages
18. Price
19. Declassification date
FREE
{DATE}
III
20. Bibliography
NO
Summary and Key Messages

Tremendous improvements in automotive particulate emissions control have been
demonstrated for advanced vehicle technologies, in particular those with Diesel
Particulate Filters, when operating on low sulphur fuels
o Greater than 95% reduction in particulate mass
o Several orders of magnitude reduction in particle number

Particle mass measurement appears to still have potential to be used for the next
step in regulatory emissions control and would provide continuity with previous data.

Particle number measurement techniques offer the potential for greater measurement
sensitivity and discrimination, and are of particular value for further research and
development into cleaner vehicles and fuels.

There is some evidence that the number of “solid” particles emitted does not always
correlate with PM mass. However, further methodology development, including
definition of suitable instrument calibration procedures and standards and multi-lab
validation exercises would be required prior to use of “solid” particle number
standards in regulation.

Further research is needed on the health relevance of measurements of volatile
“nucleation” mode particles, their chemical composition and their fate in the
atmosphere. We propose the term “nanodroplets” for such particles because they
seem to be composed predominately of droplets of sulphuric acid or heavy
hydrocarbons
4
Introduction
Health effects of particulate emissions from road transport have been of concern for many
years. To date, particulate emissions from vehicles have been controlled via legislation based
on particulate mass. Recent studies have however suggested that adverse health effects may
not only correlate with be dependent on total particulate mass, but also with on other metrics
including size, number and surface area. Smaller particles have been claimed by some to
cause more adverse effects per mass unit than large particles. This has led to revision of the
particulates Air Quality Standard in the U.S.A to include measurement of finer particulates
(PM10  PM2.5) and to further evaluation of the best metric for air quality standards worldwide.
In Europe, further tightening of controls on particulate mass emissions from vehicles is being
implemented through the Euro-3 and Euro-4 standards for light duty (LD) vehicles and Euro3, 4, and 5 standards for heavy duty (HD) engines [1,2], with discussions already started on
potentially even stricter limits for Euro-5 LD and Euro-6 HD.
Since health effect studies on particulate emissions remain unclear on the causal factors [3-7]
(one could perhaps also refer to a recent WHO report here), the Particulates Consortium
investigated a range of measures of automotive particle emissions, in particular focusing on:
mass, size, number and surface area. The results for a wide range of vehicles, fuels and test
cycles, were reported in Deliverables 10-14. The following section summarises the main
findings with regard to the relevance of current automotive particulate emissions
measurement and future aspects to be considered, illustrated by examples of the data from
the Consortium Deliverables.
Relevance of current automotive particulate emissions measurement
and future aspects to be considered
Regulated Particulate Mass
The current regulated PM mass method has been shown to be capable of repeatable
measurements even at very low emission levels down to those seen from DPF-equipped
diesel vehicles (Figures 1 and 2). Continued use of this method has advantages for
continuity of data and to provide a link with the existing air quality database, which is also
based on mass measurement. The relative standard deviation will, however, increase by
decreasing PM mass and the precision of the method may have to be improved for low mass
determinations.
5
Figure 1.
Regulated particulate mass - NEDC (CONCAWE)
Euro 3 limit
0.05
PM, g/km
0.04
0.03
Golf
Euro 4 limit
Peugeot
0.02
0.01
0
D2
D3
D4
D5
D6
D7
Fuel Code
Note: Car A without DPF, Car B with DPF (Change “Golf” to A etc. in the figure, explain
what the error bars represent, sd or standard error?)
Figure 2.
Regulated particulate mass ESC (AVL).
Euro 3 limit
0.1
PM, g/kWh
0.08
Engine
0.06
Euro3
Euro4
Euro5
0.04
Euro 4 &
Euro 5 limit
0.02
0
D2
D3
D4
D5
D6
D7
Fuel Code
Note: Euro 4 engine with EGR & CRT
Euro 5 engine with SCR/urea, without DPF
Note: Figs 1 and 2 could be replaced with Figs with all Consortium data, as in the proposed
SAE paper – but for this purpose, linear scale would best illustrate the situation.
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Particulate Size / Number Distribution
Automotive particle emissions have been shown to reside mainly at the (very low end???)
lower end of the PM10 size range currently used for Air Quality measurements. A bi-modal
distribution of solid “accumulation mode” and volatile “nucleation mode” particles, as shown in
Figure 3, is often observed.
Figure 3
Typical Size distributions in automotive Particulate emissions
Typical Diesel Particle Size Distributions
Number, Surface Area, and Mass Weightings
Particulates dealt
with both
separately
Normalized Concentration,dC/Ctotal /dlogDp
0.25
0.2
Nuclei Mode - Usually consists of
particles formed from volatile
precursors as exhaust mixes
with air during dilution
Fine Particles
Dp < 2.5 m
Nanoparticles
Dp < 50 nm
PM10
Dp < 10 m
0.15
Ultrafine Particles
Dp < 100 nm
0.1
Accumulation Mode- Usually consists
mainly of carbonaceous agglomerates
that have survived the combustion process
Coarse Mode- Usually
consists of re-entrained
particles, crankcase fumes
0.05
0
0.001
0.010
0.100
1.000
10.000
Diameter ( m)
Mass Weighting
Number Weighting
Surface Weighting
Source: D.Kittelson
The Particulates Consortium took up the difficult challenge to measure both types of
automotive particle emissions, solid “accumulation mode” and volatile “nucleation mode”. To
this end, a detailed sampling and measurement protocol was developed, which included both
a “wet” and a “dry” branch [8].
Using this protocol, a wide range of vehicles and fuels were tested. It has been shown that
detailed measurements based on particle size and number are possible and can offer
improved sensitivity and discrimination over the current regulated mass method. Under well
controlled laboratory conditions, repeatable particle number measurements were
demonstrated (Figures 4-6). However, further development would be needed if such methods
were to be considered for certification testing, in particular especially with regard to calibration
issues and complexity of the sampling and measurement methodologies. At this stage, the
main value of particle number measurements is for further research into vehicle and fuel
effects. (just a question: what is meant by “discrimination” here?)
ELPI counts are approximately the same as the CPC counts. Do we need to comment this?
No nucleation during these conditions??
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Figure 4
duplicate??
LD Vehicle data (LAT – Total Dry Particle Number, ELPI) Lag D4 in
ELPI N Stages 1-7 - Cold NEDC
Euro II Diesel
Euro III Diesel
1.0E+15
1.0E+14
Euro III
Gas
1.0E+13
Euro I
Diesel
Euro I
Gas
1.0E+12
1.0E+11
1.0E+10
km-1
1.0E+09
1.0E+08
1.0E+07
1.0E+06
1.0E+05
1.0E+04
1.0E+03
1.0E+02
1.0E+01
1.0E+00
Lag D2 Lag D3 Lag D4 Lag D5 Cor G3 Cor G1
BMW
G1
BMW
G3
Golf Cat Golf Cat Golf Cat Golf D2 Lag trp1 Lag trp1 Lag D4 Lag trp2
D4
D3
D2
D4
D3
D4
Euro III Diesel + trap
Figure 5
duplicate??
LD Vehicle data (LAT – Total Particle Number, CPC) Lag D4 in
Euro III Diesel
1.0E+15
Euro II Diesel
Euro I
Diesel
CPC Total N - Cold NEDC
Euro III
G as
Euro I
G as
1.0E+14
1.0E+13
1.0E+12
1.0E+11
1.0E+10
km-1
1.0E+09
1.0E+08
1.0E+07
1.0E+06
1.0E+05
1.0E+04
1.0E+03
1.0E+02
1.0E+01
1.0E+00
Lag D2 Lag D3 Lag D4 Lag D5 Cor G3 Cor G1
BMW
G1
8
BMW
G3
Euro III Diesel + trap
Golf Cat Golf Cat Golf Cat Golf D2 Lag trp1 Lag trp1 Lag D4 Lag trp2
D4
D3
D2
D4
D3
D4
Figure 6
LD Vehicle data (LAT – Active Surface Area, ASMO)
Active Surface Area - Cold NEDC
1.0E+06
Euro II Diesel
Euro III Diesel
Euro I
Diesel
1.0E+05
cm2 km-1
1.0E+04
Euro III
Gas
Euro I
Gas
1.0E+03
1.0E+02
1.0E+01
1.0E+00
Lag D2 Lag D3 Lag D4 Lag D5 Cor G3 Cor G1
BMW
G1
BMW Golf Cat Golf Cat Golf Cat Golf D2 Lag trp1 Lag trp1 Lag D4 Lag trp2
G3
D4
D3
D2
D4
D3
D4
While sensitivity and discrimination is one issue, there is also some evidence that the number
of “solid” particles emitted does not always correlate with PM mass. Comparison of Figure 7
with Figure 2 shows that while a Euro-4 (DPF-equipped system) and a Euro-5 (SCR/urea
system without DPF) both substantially reduced regulated particulate mass versus a Euro-3
engine, the DPF system gave much lower dry particle number emissions. Comparison of
Figure 7 with Figure 2 shows that while a Euro-4 (DPF-equipped system) and a Euro-5
(SCR/urea system without DPF) emitted similar amounts of regulated particulate mass (both
substantially reduced versus a Euro-3 engine), the DPF system showed two orders of
magnitude lower dry particle number emissions than the SCR/urea system without DPF.
9
Figure 7.
Total count ELPI stages 1-7 (30-1000nm) + thermodenuder, ESC (AVL).
HD engine test results (ESC) (geometric means)
ELPI stages 1-7, Total N, kWh-1 (ESC)
1.00E+13
ELPI stages 1-7, Total N, kWh-1
1.00E+12
EURO3
EURO4
EURO5
1.00E+11
1.00E+10
1.00E+09
D2
D3
D4
D5
D6
D7
Fuel
There is therefore merit in a measurement method, which covers the number/size distribution
of “solid” particles. The current programme included only limited measurements of dry
particles (ELPI + thermodenuder). If such methodologies were to be considered for future
regulation, much more work would be needed to agree on the most suitable sampling and
measurement methods, and to define suitable calibration standards and procedures. Further
work in this direction is currently taken up by the UN-ECE PMP group [7].
As described above, the programme demonstrated the ability to measure both ‘wet’ and ‘dry’
particles through suitable choice of the sampling conditions. However, it also confirmed that
the volatile “nucleation” mode is very sensitive to the exhaust sampling conditions (Figure 8).
10
Figure 8
Nucleation mode highly sensitive to dilution conditions [9}. The
temperature of the dilution air was changed while residence time and air humidity were
kept constant.
Despite the above uncertainties, the PARTICULATES programme has demonstrated that
under well controlled laboratory operation, the main effects of fuel sulphur, vehicle technology
and operating conditions/history on emissions of nano-particles can be clearly distinguished.
When there is potential to form nucleation mode particles, the PARTICULATES sampling and
measurement system generally finds them. We really don’t know this, do we?
On light duty vehicles, nucleation mode particles are mainly emitted under high speed/load
(high temperature) operation, which is where fuel sulphur effects become most apparent. In
this work, the effects were most obvious at constant 120 km/h operation and on the Artemis
Motorway driving cycle.
Other emissions, e.g. NOx emissions, were also increased on the Artemis motorway cycle
versus the standard NEDC cycle; the relevance of the test cycle is another issue to be
reviewed with regard to future legislation. This will be considered further under the sister
project, ARTEMIS.
Figure 9 illustrates 120 km/h data for two cars, one with and one without a DPF, and shows
the large benefits that can be achieved with a DPF-equipped vehicle operating on low sulphur
fuels - around 4 orders of magnitude (10,000 times) lower particle number emissions versus
the Euro-3 non-DPF vehicle / 300 ppm sulphur fuel case. Figure 9 also confirms that the full
benefits of the DPF are only achieved with the low sulphur fuels. Present a list of the fuels
somewhere in the text (in the beginning?) so that people can find out what D2, D3, D4 etc.
are.
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Figure 9
LD Vehicles, SMPS data N<30 nm and N>30 nm @ 120 km/h
LD vehicle test results (120 km/h) (geometric means)
SMPS, N, km-1 (120 km/h)
1.00E+16
1.00E+15
SMPS, N, km-1
1.00E+14
D2
D3
D4
D5
D6
D7
1.00E+13
1.00E+12
1.00E+11
1.00E+10
1.00E+09
1.00E+08
N ≥ 30nm
N < 30nm
N ≥ 30nm
N < 30nm
GOLF
PEUGEOT
Engine
The main effects of diesel fuel sulphur reduction and particle traps are already in the process
of being implemented and as described above will bring large reductions in automotive
particulate emissions across the size range.
However, the health implications of volatile nucleation mode particles remain largely
unknown. One could perhaps introduce the term “nanodroplets” for such particles because
they seem to be composed mainly of sulphuric acid or heavy hydrocarbons. Further research
is needed on the health relevance of measurements of such nanodroplets nucleation mode
particles, their chemical composition and their fate in the atmosphere. Inclusion of such
measures in regulations is inappropriate until the air quality and health implications are
understood. As an example of the uncertainties involved, it can be mentioned that particle
number (or surface area) may not necessarily be an issue for nanodroplets depositing in
lungs. The droplets may be dissolved in the lung lining fluid (a film of surfactants covering the
airways) and thus cease to exist as individual particles. Nevertheless, continued development
of measurement methods for small particles is important for on-going research into vehicle
and fuel effects.
12
On gasoline vehicles, particulate emissions from the current generation of direct injection
gasoline vehicles have been confirmed to be increased versus conventional MPI gasoline
vehicles. The particulate emissions remain far below the current Euro 4 diesel PM emissions
standard, but are higher than the DPF-equipped diesel case. Figure 10 illustrates this effect
based on total solid particle number count measured on the “dry” branch with the ELPI.
Figure 10.
Total solid Particle Number over NEDC, ELPI data (explain the
abbreviations used)
1,E+15
NEDC
Solid particle emission rate [km-1]
D
1,E+14
DISI
1,E+13
1,E+12
1,E+11
DPF
G
1,E+10
D2
D3
D4
D5
G1
13
G2
G3
1.
References
1. EU (1998) Directive 98/69/EC of the European Parliament and of the Council of 13
October 1998 relating to measures to be taken against air pollution by emissions from
motor vehicles and amending Council Directive 70/220/EEC. Official Journal of the
European Communities No. L 350/1, 28.12.98
2. EU (1999) Directive 1999/96/EC of the European Parliament and of the Council of 13
December 1999 on the approximation of the laws of the Member States relating to
measures to be taken against the emission of gaseous and particulate pollutants from
compression ignition engines for use in vehicles, and amending Council Directive
88/77/EEC. Official Journal of the European Communities No. L044, 16.02.2000
3. DG TREN PARTICULATES Consortium. Characterisation of exhaust particulate
emissions from road vehicles. Deliverable 2, April 2000. Vehicle exhaust particulates
characterisation, properties, instrumentation and sampling requirements
4. INERIS report for PARTICULATES
5. CRC International Workshop on PM. October 2002 San Diego
6. UNICE letter responding to Commission’s Draft Particulates Position Paper, October
2003.
7. Report of the GRPE Particle Measurement Programme (PMP) Government Sponsored
Work Programmes. July 2003
8. D3. PARTICULATES WP 300 report, part II: Relevant protocol for exhaust particulates
characterisation
9. D3. PARTICULATES WP 300 report, part I: Investigations for the definition of sampling
conditions for the defined instrumentation
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