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

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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)

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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%

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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

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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

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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%

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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

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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

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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.

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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