Non-Destructive X-ray Measurement of Soot, Ash, Washcoat and

Managed by UT-Battellefor the Department of Energy

Non-Destructive X-ray Measurement of Soot, Ash, Washcoat and

Regeneration Damage for DPFs

Charles E.A. Finney, Todd J. Toops, C. Stuart DawOak Ridge National Laboratory

Jan Zandhuis3DX-RAY

Thomas FoxX-Metrix

DEER

August 7, 2008


Need for non-destructive technique for ash and soot analysis

•

Typical techniques to determine the soot and ash location require destruction of DPF–

May disrupt layers

–

Sequential measurements not possible–

Resolution along the length not possible


Typical EPMA preparation illustrates potential ash/soot layer disruption•

First step:–

Cut into pieces–

Possible mechanical disruption

•

Second step:–

Fill channels with epoxy–

Possible disturbance of ash from the walls; flowing

•

Third step:–

Electron microprobe–

Low probability of disruption

Middle ExitInlet

Inlet Middle Exit

+ =


Opportunity to use X-ray instrument at ORNL for short-term DPF analysis

•

Loaned from 3D X-ray (Ltd.) for 6 weeks–

MDXi

400

•

Linear low noise detector•

12 bit, 4096 gray scale levels•

Control over sample height•

Control over sample angle•

Batch file capability

–

Evolved from airport security screening devices

–

Scan can be recorded in 15s

•

Can it be used to detect ash and soot distributions in a DPF?


Basics of X-ray imaging

Collimated line-scan imaging


Goals of analysis

•

Measure and corroborate ash distributions from rapid ash loading projects

•

Measure soot distribution –

In-can soot distribution from engine

–

Quantification and calibration with simulated soot loading

•

Measure thermal damage in DPFs–

Purposefully damaged


Ash Loading and Distribution


DPF

DOC

Experimental setup for accelerated ash loading at ORNL

(ash part 1)•

517cc Hatz

Engine

is operated at 1500 RPM continuously

•

5% lube oil mixed with ULSD fuel

•

700cc DPF

•

Active regeneration


Ash deposits observed in rear section

•

Shows good correlation to EPMA results

Flow

~7% signal

X-Ray transmission image

X-Ray transmission profile

Channels start filling Saturation all channels are filled

Inlet 150 mm


Accelerated ash loading at MIT (ash part 2)•

Sloan Automotive Laboratory accelerated ash loading system (Sappok

et al.

–

DEER 2008)

•

DPF received in two halves–

One with ash loaded, one unusedSystem Specifications

• Exhaust heat exchangers – counter flow • Centrifugal blower – backpressure control• D5.66” x 6” DPF


Ash in segmented DPF

•

X-ray confirms ash plugs ~4

cm from end

CLEAN FLATTENEDClean

Ash loaded

Transmission Difference

X-ray Transmission Comparison

Shifted profile

ASH FILLED FLATTENEDAsh loaded

FLOW


Quantification of ash loading determine ash density and specific loading profile•

Area under curve correlates to ash mass

•

Local packing densities can be calculated

0.169 0.181

0.338

0.260

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Field 200CPSI

Field ACT Field ACT Lab 200CPSI

Ash

Pac

king

Den

sity

[g/c

m3 ]

0 20 40 60 80 100 120

Length (mm)

0

0.05

0.1

0.15

0.2

0.25

0.3

Ash density (g/cm

3)

Observed ash plug fromdestructive analysis

•

X-ray corroborates destructive analysis–

density measurement –

approximate plug length

•

Unusual packing distribution not detected during destructive analysis–

Difficult to do through lab measurements


Soot Loading Studies


Controlled soot loading for calibration and quantification (part 1: laboratory soot loading)

•

75mm (0.6L) uncatalyzed Cordierite

•

Artificially vacuum loaded•

One half sooted (0.3L), other half clean (masked off)

Added Weight Loading

0

reference

0.00 g/L

1

0.59g

1.97g/L

2

1.16g

3.87g/L

3

1.77g

5.90g/L

A

B

clean

sooted

FLOW


Lab-loaded DPF shows gradual decrease in X-ray transmission with increasing soot

DISTANCE

REFERENCE & SOOTED TRANSMISSION DIFFERENCE PROFILES

TRA

NSM

ISSI

ON

DIF

FER

ENC

E %

0.00 g

0.00 g/L

0.59 g

1.97 g/L

1.16 g

3.87 g/L

1.77 g

5.90 g/L


X-ray response shows good correlation to soot mass in lab-loaded DPF

•

Linear regression shows good correlation to soot mass

•

Suggests detection limits of ~0.1 g

X-ray measurement of soot mass by accumulating difference signal across sooted

section

y = 2.74x + 0.03R2 = 1.00

0

0.5

1

1.5

2

0 0.2 0.4 0.6 0.8X-ray response (a.u.)

Soot

Loa

ding

(g)


Soot loading conditions (part 2 in-can)

•

DPF was filled using exhaust from Mercedes 1.7 L engine for 5 hours –

2300 rpm, 4.2 bar condition with 2007 ULSD

•

Cordierite DPF –

14 cm x 15 cm–

5.6 liters

•

16 grams of soot loaded (2.9 g/L)


Flow


Mass Difference 16.7g ( 3 g/L) soot

17.3g ( 3.1g/L) acclimatised

Flow


Mass Difference 16.7g ( 3 g/L) soot

17.3g ( 3.1g/L) acclimatised

Soot measurement in can

•

X-ray device can detect soot distribution at loadings of 3 g/L–

Adsorption of 0.1 g/L H2

O is detectable

•

Marginally higher soot accumulated in front section


Soot and ash response summary

•

X-rays much more sensitive to ash than soot

•

Ease of measurement may limit absolute resolution–

However, small changes still detectable in can

Transmission Signal

Ash 30-40% 4-7%

Soot 30-40% ~1%

Soot in can ~5% ~0.1%


Substrate Damage


Thermal damage inside can

Flow

Simulated melt inside canned DPFSimulated melt inside canned DPF

300mm

340mm


Conclusions•

Ash deposits are readily detectable and can be quantified

•

Corroborates other analysis techniques with increased detail and without sample destruction

•

DPF soot distribution can be measured inside and outside the can

•

Soot mass distributions can be measured

•

Possible approach that we weren’t able to perform:–

Sequential ash and soot loading to determine the distribution of soot as a function of ash accumulation

–

Direct calibration of soot/ash density and transmission attenuation


Supplemental slides


Contact:Contact:

Contact details:Contact details:Jan ZandhuisJan Zandhuis3DX3DX--Ray LimitedRay LimitedPera Innovation ParkPera Innovation ParkMelton MowbrayMelton MowbrayLeicestershire,LE13 0PBLeicestershire,LE13 0PBUKUKTel:Tel:

+44 (0) 1664 503 600+44 (0) 1664 503 600Email:Email:

[email protected]@ish.co.ukURL:URL:

www.3dxwww.3dx--ray.comray.com

Dr Thomas J. FoxDr Thomas J. FoxPresidentPresidentXX--Metrix IncMetrix Inc(US Distributor for 3DX(US Distributor for 3DX--Ray Ltd)Ray Ltd)2513 Early Court2513 Early CourtVirginia Beach, VA 23454Virginia Beach, VA 23454Tel: 757Tel: 757--450450--59785978Email:Email:

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Non-Destructive X-ray Measurement of Soot, Ash, Washcoat and

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