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
I
A project sponsored by:
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:AristotleUniversity of Thessaloniki, Laboratory of Applied Thermodynamics - EL
CONCAWE:CONCAWE, the oil companies' European organisation for environment, health and safety - B
VOLVO:AB Volvo - S
AVL: AVL List GmbH - A
EMPA: Swiss Federal Laboratories for Material Testing and Research - CH
MTC: MTC AB - S
TUT: TampereUniversity of Technology - FIN
TUG: Institute for Internal Combustion Engines and Thermodynamics, Tech.UniversityGraz - A
IFP: Institut Français du Pétrole - F
AEAT: AEA Technology plc - UK
JRC: European Commission – Joint Research Centre - NL
REGIENOV: REGIENOV - RENAULT Recherche Innovation - F
INRETS:Institut National de Recherche sur les Transports et leur Securité - F
DEKATI: DEKATI Oy - FIN
SU:Department of Analytical Chemistry, StockholmUniversity - S
DHEUAMS: Department of Hygiene and Epidemiology, University of AthensMedicalSchool -
EL
INERIS:Institut National de l’ Environment Industriel et des Risques - F
LWA:Les White Associates - UK
TRL:Transport Research Laboratory - UK
VKA:Institute for Internal Combustion Engines, AachenUniversity of Technology – D
VTTVTT ENERGY – Engine Technology and Energy in Transportation - FI
I
A project sponsored by:
EUROPEAN COMMISSION
Directorate General Transport and Environment
In the framework of:
Fifth Framework Programme
Competitive and Sustainable Growth
Sustainable Mobility and Intermodality
Publication data form
1. Framework ProgrammeEuropean Commission – DG TrEn, 5th Framework Programme
Competitive and Sustainable Growth
Sustainable Mobility and Intermodality / 2. Contract No
2000-RD.11091
3. Project Title
Characterisation of Exhaust Particulate Emissions from Road Vehicles
(PARTICULATES) / 4. Coordinator
LAT/AUTh
5. Deliverable Title
Relevance of current PM emission standards and further aspects of particulate properties to be taken into account / 6. Deliverable No
14
7. Deliverable Responsible
CONCAWE/Volvo / 8. Language
English / 9. Publication Date
{December 2003}
10. Author(s)
N Thompson, U Wass / 11. Affiliation
CONCAWE, Volvo
12. Summary
{See report summary}.
13. Notes
{Version Notes}.
14. Internet reference
{
15. Key Words / 16. Distribution statement
FREE
17. No of Pages / 18. Price
FREE / 19. Declassification date
{DATE} / 20. Bibliography
NO
1
Summary and Key Messages
- Tremendous improvements in automotive particulate emissions control have been demonstratedfor advanced vehicle technologies, in particularthose with Diesel Particulate Filters, when operating onlow sulphur fuels
- Greater than 95% reduction in particulate mass
- Several orders of magnitude reduction in particle number
- Particle mass measurementappears 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 intocleaner 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
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 withbe dependent on total particulate mass, but alsowithon other metrics including size, number and surface area. Smaller particles have been claimed by some to cause more adverse effects per mass unitthan 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 Euro-3, 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 findingswith 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.
Figure 1. Regulated particulate mass - NEDC (CONCAWE)
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).
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 scalewould best illustrate the situation.
Particulate Size / Number Distribution
Automotive particle emissions have been shown to residemainly at the (very low end???)lower end of the PM10 size range currently used for Air Quality measurements. Abi-modal distribution of solid “accumulation mode” and volatile “nucleation mode” particles, as shown in Figure 3, is often observed.
Figure 3Typical Size distributions in automotive Particulate emissions
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 fuelswere 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 particularespeciallywith 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??
Figure 4LD Vehicle data (LAT –Total Dry Particle Number, ELPI)Lag D4 in duplicate??
Figure 5LD Vehicle data (LAT –Total Particle Number, CPC)Lag D4 in duplicate??
Figure 6LD Vehicle data (LAT –Active Surface Area, ASMO)
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 Figure7 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.
Figure 7. Total count ELPI stages 1-7 (30-1000nm) + thermodenuder, ESC (AVL).
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).
Figure8Nucleation 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 maineffects of fuel sulphur, vehicle technology and operating conditions/historyon 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, whichis 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 9illustrates120 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 vehicleoperating 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.
Figure 9LD Vehicles, SMPS data N<30 nm and N>30 nm @ 120 km/h
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 volatilenucleation mode particles remainlargely 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 nanodropletsnucleation 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 intovehicle and fuel effects.
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 10illustrates 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.References
- 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
- 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
- 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
- INERIS report for PARTICULATES
- CRC International Workshop on PM. October 2002 San Diego
- UNICE letter responding to Commission’s Draft Particulates Position Paper, October 2003.
- Report of the GRPE Particle Measurement Programme (PMP) Government Sponsored Work Programmes. July 2003
- D3. PARTICULATES WP 300 report, part II: Relevant protocol for exhaust particulates characterisation
- D3. PARTICULATES WP 300 report, part I: Investigations for the definition of sampling conditions for the defined instrumentation
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