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Application of Particulate Filter Technology to a CNG Engine
Jonathan HarrisWestport Innovations Inc.
Introduction
• Project had three main areas of work;– Investigation into the effect of the addition of a
Particulate Filter (PF) on the emissions from a CNG-fueled Heavy-duty engine.
– Investigation into the impact of lubricants on emissions from CNG engines.
– Assess emission-reduction potential, performance, and reliability of the catalyzed particulate filters during a six-month in-use demonstration program.
• Funded by SCAQMD, Sempra Utilities and NREL.
Introduction
• Project was lead by Westport Innovations with support from the following;– West Virginia University (WVU)
• Chassis Dynamometer facilities and regulated emissions
– University of Wisconsin (UWI) • Chemical speciation
– University of Minnesota (UMN) • Aerosol concentrations and size distributions
– SunLine Transit Agency • Field Trial Partner
Contents
• Suitability of Particulate Filters for use with CNG engines
• Aftertreatment Configuration Selection• Testcell Setup and Investigation • Vehicle Installation• Chassis Dynamometer Testing and Results• Field Trial Results• Conclusions
PF Suitability for CNG Engines.
• Composition of PM from CNG engines is significantly different to that from Diesel Engines
• CNG PM in general has: – Lower engine out PM levels – Larger fraction of Ash and VOF – Lower elemental carbon levels
• For Lean Burn SI (LBSI) engines– Higher NOx to carbon ratio (vs. diesel)– Higher minimum exhaust temperatures (vs. diesel)– O2 in exhaust stream
• LBSI engine exhaust conditions should be favorable to PF continuous regeneration
Selected Engine
• Engine selected is the CWI C Gas Plus. • Launched in 2001• Lean-burn Spark Ignited (LBSI) engine.• Turbocharged • Fuel metered into intake (fumigation)• Air to Fuel (AFR) control via oxygen sensor in
exhaust stream. • Drive-by-wire throttle.
Selected Engine
• The CWI C Gas Plus is certified to the following emissions levels:– US EPA 2004– EPA CFFV ULEV– CARB Optional Low NOx (1.8 gm/bhp-hr)– Euro 3 (with THC specific catalyst)
• Certification PM emissions < 0.01 g/bhp-hr • Peak Torque 850 lb-ft (1153 Nm) at 1400 rpm • Rated Power 280 HP (209 kW) at 2400 rpm.
Aftertreatment Configuration Selection
• Selection to find best combination for CNG operation.
• 2 PF’s selected:– Engelhard DPXTM [Catalyzed Diesel Particulate Filter]– Engelhard PF [Uncatalyzed Particulate Filter]
• 2 Oxidation Catalysts selected:– Standard C Gas Plus formulation– HEX-1107 [predominantly Palladium]
Testcell Setup•Testcell located at Westport Innovations in Vancouver, Canada.
•PM emissions measured using Sierra BG-2 Mini-dilution tunnel.
•Horiba emissions bench used for gaseous emissions measurement.
•Modular exhaust system allows for combinations of PF and oxidation catalyst to be tested.
Testcell Investigation
• Engine was base-lined for engine out emissions and with standard OEM Oxidation Catalyst fitted.
• Various aftertreatment configurations fitted and compared by:– Measured PM mass emissions.– Effect on gaseous emissions.– PF mass increase over 100 hours.
• Results allowed selection of configuration for field trial.
Testcell Investigation
• Selected Configuration combined in series:– Standard C Gas Plus Oxidation Catalyst + Uncatalyzed
Engelhard PF PM Mass flow AVL 8 Mode
0
0.5
1
1.5
2
2.5
3
3.5
4
Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8
AVL Mode
Mas
s flo
w g
/h
Standard C+ CatStd C+ & DPF2
Vehicle Installation
• SunLine Transit supplied a 40-ft transit bus fitted with a CWI C Gas Plus.
• Aftertreatment system fitted for a 6 Month Field Trial in revenue service.
Vehicle Installation
• Available space for packaging was limited in this chassis.
Oxidation Catalyst
Particulate Filter
Engine
Chassis Dynamometer Testing
• “Real-world” testing of selected Aftertreatment system completed on WVU portable Chassis Dynamometer.
• “Clean” CVS tunnel (reserved for low-emitting applications) was used for this study.
Chassis Dynamometer Testing
• Test cycles used:– 3 steady state modes (idle, 20 mph, 40 mph)– Quad Central Business District Cycle (QCBD)
CBD Cycle Profile
Instrumentation
• UMN (physical characterization)– Condensation Particle Counter (CPC)
• to measure total particle number concentrations]
– Engine Exhaust Particle Spectrometer (EEPS)• Aerosol size distributions
– Scanning Mobility Particle Sizer (SMPS)• 10 to 300 nm for steady state testing only
• UWI (chemical characterization)– Media was collected on-site and processed once
testing was completed.
Chassis Dynamometer Results• Gaseous emission results
HC Mass Flow
0
50
100
150
200
250
300
350
400
Idle Run 1 Idle Run 2 20 MPH 40 MPH
Mas
s Fl
ow [g
/hou
r]
OC only.
OC + PF
CO2 Mass Flow
0
10000
20000
30000
40000
50000
60000
Idle Run 1 Idle Run 2 20 MPH 40 MPH
Mas
s Fl
ow [g
/hou
r]
OC OnlyOC + PF
NOx Mass Flow
0
50
100
150
200
250
300
Idle Run 1 Idle Run 2 20 MPH 40 MPH
Mas
s Fl
ow [g
/hou
r]OC OnlyOC + PF
• PF does not adversely affect gaseous emissions from engine.
Chassis Dynamometer Results• PM mass emissions
PM Mass Emissions on a g/mile basis from WVU measurements.
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
OC Only OC + PF
PM g
/mile
Run 1
Run 2
Run 3
Chassis Dynamometer Results• Particulate Filter reduces particle number.
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E+04
1.0E+05
0 200 400 600 800 1000 1200 1400 1600
Elasped Time, s
CPC
Num
ber,
par
ticle
s/cm
3
End-Of-Life, OCEnd-Of-Life, OC+PF
Plot of CPC number concentration for the average quad-CBD cycle for the end-of-life oil condition, with the OC and with the OC and PF together.
Chassis Dynamometer Results• Start up spikes removed with addition of PF
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E+06
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Elasped Time, s
CPC
Num
ber,
par
ticle
s/cm
3
New, OCMid-Life, OCEnd-Of-Life, OCEnd-Of-Life, OC+PF
Particle number measured during 40 mph tests, not corrected for dilution ratio.
Chassis Dynamometer Results• Distribution of particles unaffected by addition of PF
1.0E+10
1.0E+11
1.0E+12
1.0E+13
1.0E+14
1.0E+15
1 10 100 1000
Dp, nm
dN/d
logD
p pe
r mile
, par
ticle
s/m
ile
Oil: End-Of-Life, Aftertreatment: OC
Oil: End-Of-Life, Aftertreatment: OC + PF
40 mph cruise condition SMPS size distribution with and without the particle filter (PF).
Chassis Dyno Results Summary
• The addition of the PF does not produce a statistically significant change in PM mass emissions
• In many cases and under many conditions, particle number concentrations were not detectable above background.
• The addition of a particulate filter is effective at removing start-up spikes in particle number concentration
• By adding the particulate filter the size distribution is unchanged but the overall number is reduced.
Field Trial Results
• SunLine Bus 531 covered over 30,000 miles in 6 months. • No mechanical issues incurred. • Fuel consumption effect minimal.
0
20
40
60
80
100
120
Janu
ary
Febru
ary
March
April
May
June
July
August
Septem
ber
October
Novembe
rDec
ember
Janu
ary
Month
Tem
pera
ture
(deg
rees
F)
0.5
1
1.5
2
2.5
3
3.5
4
Fuel
Eco
nom
y (g
.g.e
.)
Daily Average High Temperature
Bus 531 Fuel Economy with PF
Bus 531 Fuel Economy without
Conclusions
• The experience of the 6-month field trial was positive with no serious issues encountered during operation.
• The addition of the Particulate Filter to the Aftertreatment system reduced the particle number emissions from the engine.
• During engine and vehicle dynamometer emissions testing, the addition of the Particulate Filter did not adversely affect the standard engine operation.
• The filter used in the 6-month field trial has been stored and could be examined (for ash content / composition etc.) further if a suitable opportunity arose.