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°C
NO2 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 exhaust
active heating
Measurement during regeneration, (before and after).
Number of cycles between regenerations
Alternatively 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-26-07
Zhang 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
CVS PCRF 100x10
Tailpipe: PCRF 15x15
Giechaskiel et al. 2014, PMP 30
PCRF selection
• PCRF at least 1000
• (PND1>100)
• Sulfuric acid might renucleate
• 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=2x10^9Mpi=<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 report
Yamada 2013
Pre-conditioning (setup)
• No studies discussing
effect of sampling system
preconditioning
• However there could be
an effect from
contaminated tunnels
• Recommendation:
• 120 km/h >20 min
Dobes et al. 2011, Vienna symp.
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:
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•
•
•
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:
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•
•
•
•
•
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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)