REGENERATION ISSUES

Institute for Energy and Transport Joint Research Centre

B. Giechaskiel, J. Andersson, G. Martini

3 April 2014

Overview

• Legislation• Heavy duty R-49• Light duty WLTP

• Literature survey / Past experience• PN emissions / Robust protocol• Pre-conditioning procedure / effect on repeatability

• Open issues• Next steps

Legislation

• GTR 4, Regulation 49 (Heavy duty)• Continuous

Oxygen with temperatures >550°CNO2 with temperatures >250°C

Declared regeneration conditions (soot load, temperature, exhaust back-pressure)At least 3 WHTC with regeneration, emissions within 15%

• Periodic in cylinder or post injection exhaustactive heating

Measurement during regeneration, (before and after). Number of cycles between regenerationsAlternatively emission within 15% between regenerations then 1 test

Legislation (Light Duty, WLTC)

• Continuous (no special procedure)• Periodic

• Single regenerative system• Multiple periodic regenerative system

• Procedure• If emissions during regeneration below limit not necessary• If emissions between regeneration events within 15%, Type I value can

be used• Otherwise arithmetic mean of equidistant Type I tests. At least before

and after regeneration. Loading with WLTC

PMP robustness

• No issues with PMP systems (eg due to high temperatures)

• Indications for volatile artifact below 23 nm, especially below 10 nm

Mamakos et al. 2011, PMP-26-07Zhang et al. 2012

PMP robustness

• Confirmation of volatile artifact below 10 nm

• Between 10 and 23 nm no clear indications of volatile artifact

• No immediate need to move below 23nm

• Monitoring advisable

Giechaskiel et al. 2014, PMP 30

CVS PCRF 100x10Tailpipe: PCRF 15x15

PCRF selection

• PCRF at least 1000• (PND1>100)

• Sulfuric acid might re-nucleate• Important not to grow to

>10nm• HCs at inlet of PND1• For sub10nm even higher

PCRF is needed

Yamada 2013

Background

• Tailpipe: PCRF=225 PN=3.3x10^9 p/km

• CVS: PCRF=1000 PN=5.5x10^9 p/km

Ki factor

• NEDC• Golden vehicle: Negligible increase

Cold start very high emissions

EUDC higher but over 1000 km negligible effect

• WLTC or CADC: • DPF1: Msi=1x10^11 (D=350-510 km), Mri=4x10^12 (d=8.2 or 23.2)

Mpi=1.9-3.4x10^11 p/km, Ki=1.9-3.4• DPF2: Msi=2x10^10 (D=220-260 km), Mri=2x10^12 (d=8.2 or 23.2)

Mpi=<1.4x10^11 p/km, Ki=4-7 With Msi=2x10^9Mpi=<1.4x10^11, Ki=35-65

or Ki~Mpi (offset method)

• Emissions always below 6x10^11

DPF 3

• Msi=5x10^9 p/km (D=300 km),

• Mri=7x10^12 p/km (d=23.2)

• Mpi=5x10^11 p/km, • Ki=100

Nature of particles

• Probably soot due to the decreased efficiency of the filter as it regenerates

• Metal from fuel additives and lubricant cannot be excluded

• Heavy molecular hydrocarbons that do not evaporate at 350°C and residence time 025-0.4 s.

Mamakos et al. 2013

Open issues

• High temperatures• Release (volatiles, ash) from DPF• Higher penetration of DPF• Ash that was previously attached on the soot• Release from tubes due to high temperatures

• More porous DPFs• Loading might affect nature of deposited material

Loading of DPF / Pre-conditioning• WLTC Frequency?• DPF fill status affects filtration efficiency and repeatability• Difference for small – large engines

Andersson et al. 2007, PMP reportYamada 2013

Pre-conditioning (setup)

• No studies discussing effect of sampling system preconditioning

• However there could be an effect from contaminated tunnels

Dobes et al. 2011, Vienna symp.

• Recommendation: • 120 km/h >20 min

Durability

• Light-duty Diesel vehicles with DPF are durable and effective to at least 160000km (AECC 2006)

• VERT procedures at least 2000 h• Accumulation of ash: Release

during regeneration

GPF

• GPFs will experience different temperatures• Passive regeneration very likely

Mamakos et al. 2013

GPF

• Lower efficiencies are needed• More porous DPF are possible (Eff >50%)

Mamakos et al. 2013

Partial Filters

• Still high efficiency for <23nm

• No special issues for sub23nm particles

Heikila et al. 2009

Summary

• Protocol: • PCRF >1000 for regenerations• Measurement of >10nm in parallel• Absolute PN levels should be monitored for many vehicles• Recommendations for WLTC exist

• Preconditioning• Setup: Ensure no desorption from vehicle, transfer tube

• Loading of DPF / GPF• Continuous systems: DPF fill state (repeatability)• Periodic system: Extremes: Small – Large vehicle

Discussions slides

Areas for investigation

• Targets (testing)• Test many vehicles Euro 6+• Confirm robustness of PMP• Confirm weighted emissions do not exceed limit

Ki factor, Frequency Levels of emissions during regeneration

Areas for investigation

• How (measurement protocol)• >23nm and >10nm, PCRF >1000 (PND1>100)

Looking for differences >50%

• System with Catalytic stripper in parallel if possible• Addition of a system at the tailpipe (for pre-con study)• Organics, sulfates, nitrates, ammonium if possible (at least for regeneration tests)• Pre-conditioned (clean) tunnel, pipes etc.

At least the temperature that will be experienced Recommendation: Gasoline vehicle at high speed eg 130 km, no low particle concentration measured

by VPR

• For measurements below 10 nm see ‘Sub23nm’ presentation• For nature of sub23nm particles see report

Areas for investigation

• Special attention on the following:• LNT: Stored sulfates etc…• FBC: Solid sub 23 nm (needs robust protocol)• SCR: Formation of solid particles, desorption of material• SCRF: Similar with SCR• GPF: Different filtration efficiency• DPF with SCR coating• Hybrids

Areas for investigation

• Extra tests• Prolonged high speed operation /lean spikes (Gasoline)• Fuel shut off: <23nm metal oxides from ash, oil (Gasoline)• Pre-conditioning effect on fill state / emissions levels

GPFs need more info

• Monitoring of background / Effect of regenerations

Collection of data

• Euro 6 testing from OEMs (NEDC data)• JRC can test if Euro 6 available (focus on WLTC)

• Preparation of a test plan/protocol• Info from OEM (e.g. when regen is about to start)

• Investigation of worst case (e.g. high loading with Granny cycle)

• Loading effect: without passive regeneration vs WLTC loading (focusing on Gasoline)