Post on 30-May-2018
Diesel Aftertreatment Systems
Jeff KohliTim Johnson
14 August 2007
11th ETH Conference on Combustion Generated Nanoparticles
2Corning Incorporated
Summary and Outline
“DPFs are becoming as much a part of the modern diesel engine as direct injection and turbocharging.” Ulrich Dohle, President Bosch Diesel, 2006.
• Diesel system trends described• Sophisticated regeneration control strategies emerging• Materials and filter design optimization in progress
– Three major DPF materials in the market– Pore size effects on filtration efficiency (~ 20 μm threshold)– Wall attributes, cell structure, and cell density – Ash management
• NOx aftertreatment trends and complexity being addressed
3Corning Incorporated
Light-Duty Diesel Vehicle Production & Filter Demand
CAGR 07-11
9.6%
5.3%
23.3%
Non Filter OEM’s: India & China Local
11,81611,1489,882
8,025
6,2994,824
3,563
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
2006 2007 2008 2009 2010 2011 2012
Veh
icle
s (0
00)
Filters
Filter Penetration 29% 37% 44% 53% 63% 69% 71%
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
2006 2007 2008 2009 2010 2011 2012
Vehi
cles
/ Fi
lters
(000
)
Non Filter OEM'sFilter OEM's
4Corning Incorporated
Light-Duty Diesel Systems Trend Close-Coupled Filters
Dur
aTra
p®A
C
Dur
aTra
p®A
T
CC CSF
CC DOC + CSF
*Asymmetric Cell Technology
• Drivers– Potential for fewer components → cost, space considerations– More continuous regeneration due to higher temperatures– Less post-injection fuel penalty and oil dilution
• Enablers– Smaller filters
• More ash-storage capacity (→ ACT)– Integration of catalyst function on the filter (CSF) with optimal pressure
drop performance• Optimized porosity & washcoat interaction
5Corning Incorporated
Summary of LDD Trends for PM and NOx Aftertreatment
• Clear majority of systems include a DOC with the DPF
• Two major architectures are emerging
– Close-coupled filter• AT and SiC optimized for higher SML applications
• Cordierite applicable with proper controls
– Under-floor filter with secondary fuel injector or vaporizer • Allows long oil-change intervals (oil dilution addressed)
• Interest in combining functionality is strong, but modular systems are the norm for the near term
– DOC + DPF + LNT/SCR (as needed)
6Corning Incorporated
DPF
DOC+DPF
DOCIPR
LNC+DPF
SCRDPF+SCR
NRD DOC+DPF
NRD DPF
0
500
1000
1500
2000
2500
3000
2006 2007 2008 2009 2010 2011 2012
Growth of filter systems continues with tightening global HDD regulations
US07 EUVKOR EUIV
JP PNLTBRZ EUIV
US10EUVI 1%KOR EUV
IN/CH EUIV
EUVI 5%NRD
Global OEM System Forecast: On-road & Non-road
Source: Corning Forecast
Key Assumptions
• EUVI timing: ’12-13 w/ some pull ahead
• US10/EUVI systems– LHD Chassis: SCR + DPF– LHD Engine: DPF + SCR– M/HHD: DPF + SCR
• Brazil: SCR and DOC+DPF
• China: SCR
• India: IPR and SCR
• 75-750 HP Non-road: DOC+DPF
(000s)EUVI 25%
7Corning Incorporated
Potential System Configurations for Future L-HD, MD and HD On-road Legislation (US2010 and EUVI)
DOCDOC
DO
C
CSF
DO
C
CSF
LNTLNT
Optional for SFISCR
SCR
Urea
DOCDOC
DO
C
CSF
DO
C
CSF
Optional for SFI
DO
C
CSF
DO
C
CSF SCRSCR
Urea
Most common HD and MDSCR Layout
SFI
Trends:
• Typical soot loads 3-5g/l
• Some applications might require higher soot loads
Most common L-HDLayout
8Corning Incorporated
Sophisticated Regeneration Control Strategies
Adaptive learning tightens A/F control and allows better soot estimation.
DPF bed temperature is controlled by oxygen level.
Oxygen control is very good in transient conditions.
Nissan SAE 2007-01-1061
9Corning Incorporated
Key Properties of Diesel Particulate Filter Materials
Property DuraTrap®AC
DuraTrap®AT SiC
Material (assuming ~ 50% porosity) CordieriteStabilized Aluminum Titanate
Silicon Carbide
Structure Monolith Monolith Segmented
Thermal Conductivity @ 500 oC (W/mK) ~1.0 ~1.0 10-20*
Coefficient of Thermal Expansion (x10-7/oC) (22-1000oC)
<6 <9 ~ 45
Specific Heat Capacity @ 500 oC (J/cm3 oC) 2.79 3.60 3.63
Thermal Shock Parameter (oC) a >800 >900 <300
Strain to Failure (%) (bending strength/elastic modulus) ~0.05 ~0.10 ~0.05
Allowable Thermal Gradient high very high lowa: MOR/(E mod x CTE) * Dependent upon bonding type
10Corning Incorporated
General Material and Design Interactions
Influencing Parameters
Strength Bulk Heat
Capacity
Soot Mass Limit
Pressure Drop
Filtration Efficiency
Catalyst Storage Space
% Porosity (constant cell density & wall thickness)
ρ = density, P = wall porosity, cp = heat capacity, OFA = open frontal area = (L-T)2/L2
• Bulk density, ρbulk = ρmaterial x (1-P) (1-OFA)
• Bulk heat capacity, cpbulk = cp
material x ρbulk
amount of ceramic material t
LWall Porosity 50% 60% 50% 60%Bulk Density - Matrix 394 g/l 315 g/l 590 g/l 470 g/lOFA - TotalOFA - Inlet Channels
200/12 300/15
53.0%26.4%
68.5%34.3%
11Corning Incorporated
Cordierite DPF reaches soot burning temperatures in about half the time of SiC. Attributed to lower thermal conductivity.
NGK Euro V&VI Conf. 6-06
12Corning Incorporated
• Oxides exhibit higher regeneration efficiencies at the same inlet temperatures.• For oxides (low thermal conductivity), slightly lower filter inlet temperatures are
desirable to initiate regeneration (higher safety & lower fuel penalty to regenerate).
Material Properties Impact Regeneration Conditions Modified Regeneration Conditions are Desired for Lower Conductivity Materials
ATSiC: low porositySiC: high porosity
ATSiC: low porositySiC: high porosity
Similar Temperature
response
13Corning Incorporated
PMP: Mass-Based Measurementsmean PM emissions (all vehicles)
0.1
1.0
10.0
100.0
Au-
Vehi
cle
DPF#
1
DPF#
2
DPF#
3
DPF#
4
DPF#
5
MP
I
GDI
#1
GDI
#2
GD
I#3
non-
DPF#
1
non-
DPF#
2
non-
DPF#
3
non-
DPF#
4
non-
DPF#
5
non-
DPF#
6
PM
em
issi
ons
[mg/
km]
3 mg/km
Jon Andersson et al., PMP LD Interlab. Final Report January ‘07
14Corning Incorporated
PMP: Number-based Measurementsmean N emissions (all vehicles)
1.0E+10
1.0E+11
1.0E+12
1.0E+13
1.0E+14
Au-V
ehic
le
DPF#
1
DPF#
2
DPF#
3
DPF#
4
DPF#
5
MPI
GDI
#1
GDI
#2
GDI
#3
non-
DPF
#1
non-
DPF
#2
non-
DPF
#3
non-
DPF
#4
non-
DPF
#5
non-
DPF
#6
Parti
cle
Num
ber e
mis
sion
s [k
m-1
]
5x1011/km
High Porosity and MPD Filter
Jon Andersson et al., PMP LD Interlab. Final Report January ‘07
15Corning Incorporated
Filtration efficiency drops significantly if DPF has significantnumber of pores >20 μm. Balancing porosity and catalyst loading is important for optimum performance.
DPF with pores larger than 18 μm show much higher full load smoke numbers. Thermal properties of the filter affect soot cake regeneration properties, giving different efficiencies vs. RPM.
All filters meet the Euro 5 PM requirements (3 mg/km) on the NEDC test cycle.
Initial filtration efficiency drops for DPFs with pores >20 μm.
NGK, SAE 2007-01-0923
Pressure drop at 4 g/l soot loading is not improved with larger pores, but is more affected by total porosity.
16Corning Incorporated
Soybean biodiesel blends produce less soot, drop balance point temperature, and result in faster burn rate.
Diesel PM production rates using diesel, B20 and B100 fuel at 2000 rpm and 20 ft-lbs. torque. Cummins 5.9 liter ISB engine, MY2002. Balance point temperature results at 1700 rpm.
2000 rpm, 250 ft-lbs., 354C
Soot combustion temperature is 550-580C for biodiesel blends, and 650-680C for diesel fuel. Difference is due to carbon structure.
NREL, Cummins SAE 2006-01-3280
17Corning Incorporated
Asymmetric cell design results in lower lifetime backpressure
Symmetric
Asymmetric
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25 30 35 40 45 50
Ash Loading (g/l)
dP21
0cfm
(kPa
)
Clean
Soot Loaded 5g/l
Standard
ACT
Standard
ACT
Source: Corning
18Corning Incorporated
DPF ash accumulation tracks lube oil consumption. Some ash goes back to the sump.
Ash accumulated on the DPF tracks lube oil consumption quite well. Only 50-56% of the total ash in the consumed oil ends up on the DPF.
Some of the ash from consumed lube oil goes back to the sump.
Back pressure – ash accumulation behavior is explained. With soot, early ash accumulation prevents deep bed filtration, which increases back pressure. Then, loss of filtration area by ash causes pressure increase. Later, loss of hydraulic diameter causes rapid increase. Asymmetric cell geometry gives +30% ash capacity.
Corning, DEER 8/06
19Corning Incorporated
Regulations Differ by Region
Note the advantage given to diesel in Europerelative to NOx
This partially explains the clear difference in market share of diesel vehicles in these two regions
Source: Michael P. Walsh
* MDPV Medium Duty Passenger Vehicles (>8,500 lb) must comply with Bin 5 standards beginning with 2009 model year** Euro 5 standards (model years 2009/10+)*** Euro 6 standards recently fixed (model years 2014/15+)
20Corning Incorporated
LDD NOx Roadmap
2006 2008 2010 2012 2014
NOx Sensor NH3 Sensor?
USEU
Japan
EU 4 EU 5 EU 6
T2B5
JP ‘09
T2B8 NOx OBD
NOx OBD
JP ‘13
<15%
50%
< 5%
2015 Diesel Market Penetration
EGR/Engine Technologies
Long-Loop EGR
US
EU
Japan
LNT, HC-SCRNH3-SCR
LNT
LNT
SCR
Smaller vehicles
Larger vehicles
BlueTec-1BlueTec-2
LNT
21Corning Incorporated
Summary
“DPFs are becoming as much a part of the modern diesel engine as direct injection and turbocharging.” Ulrich Dohle, President Bosch Diesel, 2006.
• Diesel system trends described• Sophisticated regeneration control strategies emerging• Materials and filter design optimization in progress
– Three major DPF materials in the market– Pore size effects on filtration efficiency (~ 20 μm threshold)– Wall attributes, cell structure, and cell density – Ash management
• NOx aftertreatment trends and complexity being addressed