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=2x10^9Mpi=<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 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: • • • • 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)
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