The European Commission’s scienceand knowledge service

Joint Research Centre

Current developments at PMPand future JRC activities

B. Giechaskiel, T. Lahde, R. Suarez-Bertoa, M. Clairotte,

T. Grigoratos, A. Zardini, A. Perujo, G. Martini

Workshop: Measurement and characterisation of nanoparticle emissions from powertrains

9 Oct 2018, Thessaloniki, Greece

Overview

• Introduction

• Solid Particle Number (SPN) regulation in EU

• Particle Measurement Program (PMP) activities

• SPN Portable Emissions Measurement Systems (PEMS)

• New Periodical Technical Inspection (NPTI)

• Market surveillance

• Non-exhaust particle emissions

For details and relevant citations see paper at Combustion Engines 2018 journal

Introduction

• Type approval

• In Service Conformity

• Roadworthiness

• OBD

Introduction of Particle Number limits

• The filter mass method failed to mandate the use of Diesel Particulate Filters (DPF)

• UN-ECE Particle Measurement Programme (PMP) was conceived, chaired by the UK

• Political will and drive came from the EC, but PMP operated under the auspices of UN-ECE to include Switzerland’s expertise, and other parties

Diesel

Particle

Filter (DPF)

PM in

PM out

Particle Measurement Programme (PMP)

• PMP Phases I (2001) & II (2003)

• Investigation of sampling and conditioning systems

• Investigation of measurement techniques

• Definition of the new (Solid) Particle Number method

• PMP Phase III

• Inter-laboratory exercises

• Light-duty vehicles (mid 2004 – mid 2007)

• Heavy-duty engines (2008-2009)

SPN regulations in EU

Regulation Cycle PM [mg/km or mg/kWh] SPN23 [p/km or p/kWh]

Light-duty (Euro 6)Type approval 2017/1151

2017/1154

WLTC

On-road (RDE)

4.5 6×1011

CF=1.5

ISC To be adopted end 2018 WLTC

On-road (RDE)

- 6×1011

CF=1.5

Heavy-duty (Euro VI)Type approval 582/2011 WHTC

WHSC

10

10

6×1011

8×1011

ISC On-road - CF under discussion

NRMM (Stage V)Type approval 2017/654

2016/1628

NRTC

NRSC

15 1×1012

ISC (monitoring) - -

L-category (Euro 4)Type approval 2013/168 WMTC 80 (diesel)

4.5 (diesel/GDI) (Euro 5)

-

PMP new Terms of Reference

• PMP activities closed with the introduction of LDV and HDE PN regulation

• 26th meeting: 11 Dec 2011 discussion on PN experiences

• EU and Switzerland requested further investigation of PN especially from GDIs

• 27th meeting: 16 May 2013 Terms of References were discussed (ToR Rev 2)

PMP extension of scope

• Calibration procedures update (and <23nm if necessary)

• Regeneration (PMP >23nm).

• Gasoline Direct Injection (GDI) vehicles

• PN equipment <23 nm

• Engine dyno tailpipe PN measurements for HD at Type Approval

• NRMM (only guidance document)

• Low Temperature testing (only feedback)

Calibration: Volatile Particle Remover

• PCRFs within 5% (with 3 exceptions)

• Concerns were raised for CAST and NaCl thermal stability even after thermal pre-treatment.

• Low cut-off CPC should be employed at the calibrations

• Suggestions for minor improvements in the calibration procedure

Calibration: Condensation Particle Counters

• Soot is in favor at the moment as calibration material

• Suggestions for improvement of the calibration procedure:

• Inclusion of k-factor

• Reference CPC according to ISO 27891

• Restriction of residuals during linearity

Regeneration

• Emissions during regeneration events are included in the heavy-duty and NRMM legislation, but not in the light-duty. The main reason was the low contribution (PMP inter-laboratory findings based on NEDC and golden vehicle)

• JRC confirmed that this is not the case for WLTC and all vehicles

• JRC confirmed the robustness of the PMP systems during regeneration events

Regeneration

• Robustness of PMP: Change of 10xPCRF does not affect the measured emissions, even the sub-23 nm measurements

• System with a catalytic stripper gives similar results

• The sub-23 nm particles were not seen at a subsequent test from the tailpipe. Indications of release of particles at high temperatures (could originate from the DPF, catalyst, even sampling lines)

Regeneration: Ki factors

Vehicle Msi [p/km] D [km] Mri [p/km] D [km] Mpi [p/km] Ki Ki offset [p/km]

Euro 4* 1.3×1011 1000 1.3×1011 11.0 1.3×1011 1.0 0

Euro 5 2.0×1010 250 2.0×1012 23.2 1.9×1011 9.4 1.7×1011

Euro 5 2.0×1011 250 1.4×1012 11.0 2.5×1011 1.3 5.1×1010

Euro 6 5.5×1009 300 6.9×1012 23.2 5.0×1011 91.0 4.9×1011

Euro 6 2.0×1010 800 2.0×1010 23.2 0.2×1011 1.0 0

Euro 6 1.0×1011 500 4.0×1012 23.2 2.7×1011 2.7 1.7×1011

Euro 6 2.0×1010 450 2.1×1011 11.0 0.3×1011 1.2 4.5×1009

Euro 6 6.7×1010 450 1.9×1012 23.2 1.6×1011 2.3 9.0×1010

Euro 6 2.7×1010 250 7.9×1010 11.0 0.3×1011 1.1 2.2×1009

* Golden vehicle PMP inter-laboratory exercise

Weighted emissionsRegeneration emissionsNon-regeneration emissions

Is there a need to regulate <23 nm?

• Literature review: Emission levels of sub23nm

• There are particles <23nm

• Experimental investigation at JRC

• There are particles <23nm

• Sometimes they are an artefact

• “Real particles” are on average 30-40% on average over a test cycle (GDI)

Monitoring of sub-23 nm particles

• Diesel: <50%

• GDIs: 20%

• CNG: 100%

• Motorcycles: >60%

• Fractions are important only if emissions are close to the SPN limit

• Extreme example of PMP systems

• At 10 nm penetration <50%

• The difference between the systems increases at lower particle sizes.

• The final result depends on the CMD (median size) of the size distribution

Can we measure <23 nm (accurately)?

(Volatile) artefact

• Volatile artefact: • Renucleation of volatiles after the

evaporation tube or the catalytic stripper results in volatile particles being counted as solid

• Typically at cold start (high amount of volatiles)

• Quite often with DPF equipped vehicles (low soot)

• Even with catalytic stripper volatile artifact at the 3 nm range can appear

(Solid) artefact

• Solid artefact: • Measurement of solid particles that are

formed after the vehicle tailpipe, but before the PN system

• Typically at high exhaust gas temperatures at unconditioned sampling lines

• Typical sizes at 10 nm or lower

• DPF regenerations

• Steady states of gasoline vehicles/motorcycles

motorcycle

Sub-23 nm activities

• Inter-laboratory exercise with two golden instruments with catalytic stripper measuring both >10 nm and >23 nm

• European phase finished

• Japan and maybe US will participate

• Horizon 2020 projects exploring other sampling methodologies, counting principles and minimum size

• DownToTen

• Sureal

• PEMS4Nano

Low Temperature (-7°C)

• Low temperature testing (-7°C) was not including SPN

• PMP confirmed the possibility to include it

• JRC has tested many vehicles

N=NEDC

Raw exhaust sampling via fixed dilution

• Interest in this approach confirmed by some engine manufacturers and some instrument manufacturers

• First analysis of potential benefits/issues presented

• Primary dilution (cold / hot)

• Losses (thermophoresis, agglomeration)

• Volatile removal efficiency (CS or ET)

• Pressure effects

• Time alignment

• Correlation with other methods (CVS and partial flow system) and advantages/disadvantages to be checked – Additional data required

Raw exhaust sampling via fixed dilution

• Experimental data hint on a 30% uncertainty

• Dedicated experimental campaign will follow (ACEA-JRC)

• Theoretical study will follow

• Technical requirements will be drafted

SPN Portable Emission Measurement Systems

Light-duty vehicles

• Regulation 715/2007 introduced the possibility to use Portable Emission Measurement Systems (PEMS) for Real Driving Emissions (RDE)

• Regulation 459/2012 focused on the emissions of Gasoline Direct Injection (GDIs) vehicles under real conditions

• Nov. 2012 call of interest for Particle Number SPN-PEMS

SPN PEMS: Program overview

• Theoretical evaluation of Diffusion Chargers (DC) (2013)

• Phase I (2013): Feasibility study

• Assessment of application and performance of portable PN instruments relative to a reference (Particle Measurement Program)

• Update of specifications (i.e. dilution and sampling system and efficiency of diffusion-chargers)

• Phase II (2014): Extensive experimental campaign

• Calibration procedures and more accurate estimates of uncertainty

• Inter-laboratory correlation exercise (2015)

SPN PEMS for HDV

Heavy-duty vehicles

• September 2015 HDV PEMS expert group decided to freeze PM method and evaluate SPN method

• October 2015: Kick off meeting SPN PEMS for HDV

• JRC main evaluation (Feb – June 2016)

• JRC second evaluation (Sept. 2016) / pre-validation

• OEMs validation program (Feb 2017 – Dec 2017)

• May 2017 theoretical SPN PEMS uncertainty study

SPN PEMS: Overview of all results

• Uncertainty of SPN PEMS is 40 – 65%. Today:• At the higher end for HDV

• In the middle for LDV

• At the lower end for CPC based systems

• Robust for most conditions (regeneration, ambient temperatures, volatiles, fuels) however until recently still some issues observed

Preliminary PN margin evaluation (HDV)

No CVS uncertainty was subtracted because the evaluation was done compared to PMP systems

Size dependency is higher than 15% when GMD is lower <30 nm or >75 nm

Particle losses are typically lower than 25%

final used values

Work 10.0% 10.0% 34.7% PN emissions uncertainty

EFM accuracy 2.0% 3.5% 3.5% 0% CVS

EFM drift 2.0% 3% Time alignment/dynamics

Linearity 2.0% 0% Boundary conditions

25% Particle losses

Analyser acc. 18.0% (+)

Size depend. 15.0% 33.0% 33.0%

62.7%

input

calculated 𝑈𝑛𝑐𝑒𝑟𝑡𝑎𝑖𝑛𝑡𝑦 = 𝑎𝑛𝑎𝑙𝑦𝑧𝑒𝑟2 + 𝑓𝑙𝑜𝑤2 + 𝑤𝑜𝑟𝑘2 + 𝑜𝑡ℎ𝑒𝑟 − 𝐶𝑉𝑆X

Comparison lab and on-road measurements

• Relative good agreement between lab and on-road

• No particular issue for GDIs fulfilling the 6x1012

p/km

• Differences could be explained in most cases (e.g. mass, ambient temperature, DPF fill state etc)

New Periodical Technical Inspection (NPTI)

• Initiative of VERT supported by Switzerland, the Netherlands, Belgium, Germany and EU

• Objective: Tamper-proof methods for exhaust assessment

• Proposal: Particle number for DPF (TNO)

• Technical specifications

Market surveillance

New type-approval framework Reg. 2018/858 (replaces Dir. 2007/46/EC) applicable from 2020 and introduces market surveillance

1) Raise the quality level and independence of type-approval and testing before a car is placed on the market

• Member states will be able to take measures in their national markets, instead of having to wait for the type-approval authority of the country that issued the vehicles’ type-approval certificate.

• National type-approval authorities will be subject to a peer review

2) Increase checks of cars that are already on the EU market by Member States

3) European oversight: Forum for exchange of information on enforcement

Although focus is on CO2 and NOx, SPN will also be monitored.

Non-exhaust particle emissions

• PMP on brakes focuses on

• a standardized test procedure for sampling and measurement (June 2019)

• a real-world braking test cycle (July 2018)

• Existing braking cycles are not representative of typical real world conditions

• Tyre wear particles were left outside the evaluation due to their dependency on the road and the limited resources available

Particles from brakes

• Results form WLTC (WMTC motos)

• Brake SPN emissions low, effect of measuring technique

• Brake PM mass relatively high

• Around 10% light absorbing carbon

NAO = Non-Asbestos Organic

ECE = European market pads

Conclusions 1/2

• For some technologies there is a significant fraction of particles below 23 nm. In absolute levels it seems not to be critical, i.e. high emitters can be identified with the PMP procedure

• Extreme differences between lab and on-road were not identified (non-GPF GDIs)

• Decreasing the lower size to 10 nm seems possible with minimum risks: definition of PCRF (losses), volatile artifacts, equipment investment (PMP and PEMS)

• Decreasing the lower size below 10 nm has high risk (today’s instruments)

Conclusions 2/2

• PN-PEMS and PMP systems can have differences up to 50%. Although up to 35% can come from the particle detector another 20% can come from the different location

• Particle “losses” (e.g. agglomeration, thermophoresis), but also solid particle formation (solid artefact) have been seen

• Tailpipe sampling is investigated for type approval and seems a step forward (less prone to artifacts and particle transformations). However improper setup has shown artefacts from condensation.

Further questions

• Ultrafine particles might be more dangerous than PM2.5. Are sub-23nm particles more dangerous than >23 nm?

• The 6x10^11 p/km(kWh) limit was based on best available technologies. What is the health relevance?

• There are health concerns for the (semi)volatile part of particles. Should it be included in the regulations?

• Sampling from the tailpipe opens the door for “total” particles measurements. Does it have an added value for regulations (i.e. does it address vehicle technologies?)

Thank you for your attention! Any questions?You can find me at barouch.giechaskiel@ec.europa.eu