1

Real-Time Particulate Filter Soot and Ash

Measurements, Optimized Control, and

Diagnostics via Radio Frequency Sensing

Alexander Sappok, Paul Ragaller, Leslie Bromberg

alexander.sappok@dpfsensor.com

www.dpfsensor.com

CLEERS Workshop

April 28, 2015

2

Challenge: Determination of Filter/Catalyst State

Stanton, D., "Systematic Development of Highly Efficient and Clean Engines to Meet Future Commercial Vehicle Greenhouse Gas Regulations," SAE Int. J. Engines 6(3):1395-1480, 2013

1

2

3

Conventional Exhaust Sensors• Measure properties of exhaust gas directly

– Temperature, Pressure– Gas Composition, Particle Content

• Provide only indirect indication of DPF state• Often require complex models or calibration

to estimate state of aftertreatment device

RF Based Exhaust Sensing• RF signal propagates through ceramic media

– Must be non-conducting• Responds to changes in dielectric

properties of aftertreatment device• Provides a direct measure of the

aftertreatment device’s loading state

Measurement of Aftertreatment State Variables

4

minminmoxmox moutmout

Soot and Ash Plugging

Source: K. Aravelli

DPF Loading State and Current Approach• Pressure drop (∆P) and model based controls to estimate loading

• Low-exhaust flow (idle), transients, regeneration, non-uniform soot distribution and oxidation in the wall pores are challenging for ∆P

• Loading state of filter continually changing with ash over lifetime

• Accurate sensing required to optimize fuel consumption and filter life

Image: SAE 2013-01-0528

Many Factors Impact DPF Loading State Determination

5

DPF

DPF Loading

1. Amount

2. Type (PM vs. Ash)

3. Distribution

• Single or dual RF Antenna

• Fast response < 1 second

RF sensor responds to changes in DPF dielectric properties

Signal fully-contained in DPF housing

• Antenna (RF Probe), similar size to exhaust temperature sensor

• Stainless steel rod-type antenna (passive component)

RF Measurement System Configuration and Operation

RF Control Unit

6Frequency

Transmission [S12]

* Adam, Stephen, F., Microwave Theory and Applications, Prentice Hall, Inc., Engelwood Cliffs, New Jersey, 1969.

Resonance Measurements and Spatial Sensitivity

7

Motivation: Aftertreatment Controls Optimization

Total FEP (Ref)

Regeneration Interval

Fu

el P

enal

ty

Total FEP ∆PR

egen

erat

ion

• Direct measure of loading state – advanced feedback controls.

• Additional advantages with alternative fuels and advanced combustion

• Adaptive controls as system ages (ash accumulation)

• Applications for OBD

Concept: Apply inexpensive radio frequency (RF) technologies to directly monitor DPF soot and ash levels and distribution with low-∆P DPF materials.

RF Sensors

DP

F

DO

C

ATS Controller

ECU

Motivation: Enable reduced energy consumption, cost, and increased durability of particulate filter systems through improved sensing and controls.

RF Sensing

DPF Materials

Advanced Controls

8

Technical Highlights: Parallel Testing Activities

• Pressure drop (OE)

• Gravimetric PM

• Gravimetric Ash

• ∆P + Models

• AVL micro-soot

• Gravimetric PM/Ash

• AVL micro-soot, TEOM

• Pressure drop

• Gravimetric PM/Ash

• Stock OEM controls (∆P + Model)

• Gravimetric PM/Ash

• Stock Volvo/Mack DPF controls

• On-road durability

•Develop RF sensors

•Sensor calibration

•PM/Ash loading

•Advanced DPF materials

•Mercedes engine test (LD)

•Navistar engine test (HD)

•AVL benchmarking

•TEOM benchmarking

•Fuels & adv. combustion

•Controls development

•DDC engine platform

•2013+ aftertreatment

•On-road fleet test

•Volvo/Mack trucks (’09 & ’13)

•24 Months total, up to 4 trucks

Technical Focus Areas Performance Metrics

9

Single Probe RF Sensor Integration for DPF Control

Hardware and System Setup• MY 2013 DD-13 diesel engine

• Stock controls and aftertreatment

• Open ECU M461 for RF-based control of regeneration

• HC dosing system upstream of DPF

• Single antenna RF sensor

SAE 2015-01-0996

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Single Probe RF Sensor Integration for DPF Control

Loading Sample Set: 24 cyclesPM Load Range: 6 g – 126 g

+ 0.68 g/L+ 0.45 g/L

Regen Sample Set: 15 DPF cyclesPM Load Range: 1 g – 18 gAftertreatment

DPF and SCR

• Stock aftertreatment system with 22.03 L DPF (27.73 kg base weight)

• DOC upstream of DPF (same can) and RF antenna mounted at DPF outlet

• RF sensor validation over multiple loading and regeneration cycles

• Comparison with gravimetric, AVL MSS, BG3, and smoke meter measurements

SAE 2015-01-0996

11

RF-Based Regeneration Management

• Reduction in regeneration duration 15% - 30% relative to stock ECU control

• RF system directly monitors PM levels in DPF during regeneration and terminates HC dosing once oxidation is complete (vs. time-based ECU approach)

Regeneration Duration Test Procedure

• DPF loaded to three different levels of PM

- High, medium, low load

• Stock ECU controlled regenerations carried out

• RF-controlled regenerations repeated at similar conditions

• Duration normalized to account for small differences in PM load and temperature

SAE 2015-01-0996

12E

GR

Turbo

DPF

DO

C

TEOMΔΔΔΔP, T

RF Control Unit

EG

R

Turbo

DPF

DO

C

TEOMΔΔΔΔP, T

RF Control Unit

RF System Transient Response Evaluation

Engine Dynamometer Testing• Testing on 1.9L GM turbo diesel engine

• Transient mode evaluation of RF response

• AVL MSS and TEOM measurements for comparison with RF and gravimetric PM

DPF: Cordierite, Catalyzed D 5.66” x 6” (2.47 L)

GM 1.9L

DPF

DOC

AVL

- AVL MSS

- TEOM

13

GM 1.9L

DPF

DOC

AVL

9.6

9.7

9.8

9.9

10

10.1

10.2

10.3

10.4

10.5

10.6

10.7

11:54 11:57 12:00 12:02 12:05 12:08 12:11 12:14 12:17 12:20

RF

Sig

nal (

RA

W)

-5

0

5

10

15

20

25

30

35

40

RF

AVL MSS Intergal

TEOM

60

65

70

75

80

85

90

95

100

11:54 11:57 12:00 12:02 12:05 12:08 12:11 12:14 12:17 12:20

Time [hh:mm]

0

20

40

60

80

100

MAF (EGR)

Torque

• Testing on 1.9L GM turbo-diesel at ORNL

• Catalyzed cordierite DPF

• 1 Hz sampling rate for AVL MSS and TEOM

• 2.5 Hz sampling rate for RF sensor

MA

F [

kg/h

r]R

F S

ign

al [

RA

W]

TE

OM

PM

[µ

g],

AV

L P

M (

inte

gra

ted

, mg

)T

orq

ue

[ft-

lb]

RF slope change due to EGR steps

12

34

5

-0.05

0.00

0.05

0.10

0.15

11:54 11:57 12:00 12:03 12:06 12:09

Time [hh:mm]

RF

Par

amet

er R

ate

-20

0

20

40

60

80

100

120

140

Soo

t [m

g/m

^3]

RF Differential

AVL MSS

1 23

4

5

RF

AVL MSS

Fast transient response to small changes in engine-out PM

Transient Response Well-Correlated with AVL MSS

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Transient Response Details of Throttle Tip-In Events

-0.100.000.100.200.300.400.500.600.700.800.90

-1000100200300400500600700800900

RF

AVL

20

25

30

35

40

45

60

70

80

90

100

110

120

130

Throttle Position

Torque

8.88.9

99.19.29.39.49.59.69.79.8

11:38 11:41 11:44 11:47 11:49 11:52

5

10

15

20

25

30

35

TE

OM

PM

[ug

], A

VL

MS

S

RF

AVL

TEOM

Derivative of RF signal compared to AVL MSS for throttle tip-in events

Time [hh:mm]

To

rqu

e [f

t-lb

]T

EO

M [µ

g],

AV

L

(In

teg

rate

d, m

g)

AV

L M

SS

[m

g/m

^3]

RF

(D

eriv

ativ

e)T

hro

ttle

[%

]R

F S

ign

al [

Raw

]

Raw RF signal vs. TEOM and AVL (Integrated)

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Ash Distribution Impacts Performance Over DPF Life

Ash distribution and deposit characteristics may result in very different ∆P measurements for same ash level in DPF.

Passive Active

Source: SAE 2012-01-1732

Source: SAE 2007-01-0920

~2X

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DPF Soot Load Measurements with Ash

0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 1 2 3 4 5 6 7

Gravimteric Soot [g/L]

RF

Soo

t [g

/L],

dP

So

ot [

g/L

]

RF_Ash 0g

RF_Ash 10g

RF_Ash 20g

RF_Ash 30g

RF_Ash 40g

RF_Ash 50g

1:1

dP_Ash 0g

dP_Ash 10g

dP_Ash 20g

dP_Ash 30g

dP_Ash 40g

dP_Ash 50g

+0.5 g/L

-0.5 g/L

+ 0.5 g/L

RF and dP (∆P) measurements both scaled to 0 g/L ash case to develop simple calibration function

RF soot load measurements unaffected by ash unlike ∆P

0

3

6

9

12

15

0 10 20 30 40 50

Ash Load [g/L]

PM

Loa

d [g

/L]

RF dP

3 g/L PM Comparison

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RF System Configuration (Mack MP-7) DSNY Fleet• MY 2009 and MY 2010+ vehicles over two year (24 months)• Antennas mounted directly into DPF assembly• Control unit mounted external to aftertreatment system• Real-time monitoring and logging of DPF loading state• System operation with stock OEM controls

Sensing System Fleet Testing on Urban Cycles (NYC)

Generation 1 Generation 2

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Time [min]

RF

Soo

t [%

]

0

100

200

300

400

500

600

700

800

900

Tem

pera

ture

[C]

RF-DPF [%] T_avg [C]

RF sensor measurement data for 150 hr period with stock 2009 Volvo/Mack DPF regeneration control system.

Regeneration

at low PM

load.

• Data from 150 hours with 21 regenerations, avg. 18 min per regeneration• OEM control triggers regenerations (~ every 7.1 hrs) at low soot loads• Vehicles spends 4% - 5% of operating time in regeneration

Fleet Vehicle Data Shows Frequent Regenerations

Self-calibration based only

on max observed soot load.

SAE 2014-01-2349

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 25 50 75 100 125 150 175 200

0

100

200

300

400

500

600

700

800

• Back-to-back regenerations occasionally observed due to vehicle shut-down

• Real-time measurement of soot load can end regeneration when complete

16.8 min

Regen

19.2 min

Regen

30 min

Unnecessary

Regeneration

Regeneration

Complete

DP

F S

oo

t Lo

ad

[%

Ta

rge

t]

Av

era

ge

DP

F T

em

pe

ratu

re [

C]

Time [min]

RF Measured Soot Oxidation to End Regeneration

RF measurements can provide direct feedback control to end regeneration.

SAE 2014-01-2349

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Summary and Technical Highlights

Outlook and Additional Applications• Current work focused on controls optimization and sensor validation in a

range of light-duty and heavy-duty applications with project partners.

• Additional opportunities for GPF and catalyst applications to monitor gas species adsorbed on catalysts

Demonstrated direct measurement of DPF soot and ash levels via RF sensing in test cell and vehicle applications.

Technical Highlights

• Developed single antenna RF system and demonstrated high level of accuracy for DPF soot level measurements

• Demonstrated combined DPF soot AND ash measurements

• RF transient response well-correlated with AVL micro-soot sensor

• Demonstrated fast sensor response < 1 second

• Evaluated RF performance over 380,000 mile equivalent DPF aging

• Fuel savings potential via extend regeneration interval and reduced regeneration duration relative to stock OEM controls

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Acknowledgements

This material is based upon work supported by the Department of Energy DE-EE0005653.

• Roland Gravel, Ken Howden, and Gurpreet Singh from the DOE

• Ralph Nine, Trevelyn Hall, and David Ollett from NETL

Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Commercial and National Laboratory Project Partners

• Corning Incorporated

• Oak Ridge National Laboratory

• Daimler Trucks NA / Detroit Diesel

• FEV

• DSNY