Uncovering Fundamental Ash-Formation Mechanisms and …

 

 

Uncovering Fundamental Ash-Formation
Mechanisms and Potential Means to
Control the Impact on DPF Performance
and Engine Efficiency

Carl J. Kamp, Alexander Sappok and
Victor W. Wong

Sloan Automotive Laboratory
Massachusetts Institute of Technology

DEER 2012

Ash Affects DPF Performance

Soot Depth Filtration
Eliminated

X

42 g/L
Ash
33 g/L
Ash

No
Ash

12.5 g/L
Ash

Cake Filtration

0

2
[SAE 2010-01-0811]

1

3

4

5

6

7

Cummumlative PM Load [g/l]

Ca

ρPack = 0.25
g/cm3

10

8

6

4

2

0

3.0

2.5

2.0

1.5

1.0

0.5

0.0

]
a
P
k
[

p
o
r
D

e
r
u
s
s
e
r
P

]
a
P
k
[

p
o
r
D

e
r
u
s
s
e
r
P

0

5

10

15

20

25

30

35

40

45

[SAE 2010-01-1213]

Cummumlative Ash Load [g/L]

CJ-4
ρPack = 0.30
g/cm3

ε = 91%

ε = 91%

Zn

ρPack = 0.19
g/cm3

ε = 95%

[SAE 2007-01-0920]

• Ash accumulates in the
wall flow-through filter
and raises ΔP

• Ash fills DPF surface

pores and forms a cake
layer

• ΔP plot shows

accumulation mode
• Lubrication chemistry

shows and effect on ΔP

Filtration concepts

Depth filtration

Cake filtration

DPF/Ash/Soot at Scale

Primary Catalyst particles

Ash Agglomerates

Ash Primary particles

Ash Plug

DPF

Span of Experimental Interest/Focus
10-5

Soot Primary particles

10-6

10-4

10-3

10-8

10-7

10-2

Ash Wall Layer &
Soot Cake Thickness

DPF Surface
Pores

DPF Wall
Thickness

m

10-1

Ash Precursors

m

10-10

10-9

Soot Precursors

m
µ
1

DPF

Catalyst
particles

Ash

Soot

40
20
0

y
c
n
e
u
q
e
r
F

DPF pore size

0

25 50 75 100
Pore diameter [µm]

Elemental
mapping

EDX

Coupled Experimental System

Sub-surface, interfacial information

FIB

HR-ESEM/BSe-
Hi-res imaging

1.

High Resolution Environmental Scanning Electron
Microscopy with Back-Scattered Electron and Energy
Dispersive X-Ray imaging
(HRSEM/BSe-/EDX)
Focused Ion Beam milling (FIB)
Quartz Crystal Microbalance with Dissipation (QCMD)
X-Ray Diffraction (XRD)
X-Ray Computed Tomography (X-Ray CT)
Temperature Programmed Oxidation (TPO)
X-Ray Fluorescence (XRF)
Small Angle X-Ray Scattering (SAXS)
Atomic Force Microscopy (AFM)

2.
3.
4.
5.
6.
7.
8.
9.
10. X-Ray Photoelectron Spectroscopy (XPS)

Aged samples:
Lab
•
• Field

X-Ray CT
3D imaging

Structure and composition

XRD

Lubrication-Derived Ash

Incombustible, inorganic, ionic compounds
•
In general, high melting temperatures and low solubilities
•
• Ca, Zn, Mg in the form of sulfates, phosphates and oxides
• Trace: Fe, B, Mo, Al, Si, Na(biofuels)
• ≈0.5-1% by mass of soot, bound to soot
• Enter as Å-nm size, grow to 100’s of µm
• Oil consumption ≈ fuel consumption/1000

Base+Ca

Base+ZDDP

CJ4

Base+Mg

20 nA

3 nA

0.3 nA

93 pA

Focused Ion Beam

[SAE 2012-01-0836]

C
W

’

n
e
k
o
r
B

‘

• FIB+SEM+EDX
• Useful for observing
interfaces, structure

• nm-µm
• Ga+ ions at 5-50 keV

• Forced sputtering
• Subsurface detail

C
W
d
e

l
l
i

m
B
I
F

10µm

Interfacial observations

Ash-DPF: Some gaps observed, Ca and Zn ash appears to form bound layer
Soot-DPF: Gaps observed at interface
Soot-Ash: Tight interface, ash acts as filter surface, very little soot penetration
[SAE 2012-01-0836]
Soot-Ash

Soot-DPF

= Interface

Ash-DPF

m
µ
0
1

m
µ
1

m
µ
0
4

m
µ
1

m
µ
5

m
µ
0
4