1

Real-Time Particulate Filter Soot and Ash Measurements via Radio

Frequency Sensing

Alexander Sappok, Paul Ragaller, Leslie Bromberg alexander.sappok@dpfsensor.com www.dpfsensor.com

19th ETH Conference on Combustion Generated Nanoparticles Zurich, Switzerland

June 29, 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

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 Sensors for Direct Measurement of DPF Loading

RF Control Unit

4

RF System Measurement Methodology

Frequency

S12

Tra

nsm

issi

on

Mode 1

Mode 2

Mode 3 Mode 4 Mode 5 Increasing Filter

Contaminant Levels

Example: Two-antenna measurement system

Antennas Antennas

Filter

Antenna

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

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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 cycles PM Load Range: 6 g – 126 g

+ 0.68 g/L + 0.45 g/L

Regen Sample Set: 15 DPF cycles PM Load Range: 1 g – 18 g Aftertreatment

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

7

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

8 EG

R

Turbo

DPF DO

C

TEOMΔP, T

RF Control Unit

EGR

Turbo

DPF DO

C

TEOMΔP, 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 1.9LDPF

DOC

AVL

- AVL MSS - TEOM

9

GM 1.9LDPF

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

Sg

a (

)

-5

0

5

10

15

20

25

30

35

40

RFAVL MSS IntergalTEOM

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 12:20Time [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

MAF

[kg/

hr]

RF

Sign

al [R

AW]

TEO

M P

M [μ

g], A

VL P

M (i

nteg

rate

d, m

g)

Torq

ue [f

t-lb]

RF slope change due to EGR steps

1 2

3 4

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

-20020406080100120140

Soo

t [m

g/m

^3]

RF DifferentialAVL MSS

1 2 3 4

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Transient Response Well-Correlated with AVL MSS

RF

AVL MSS

EGR steps result in variation in engine-out PM measured by RF sensor

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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

RFAVL

20

25

30

35

40

45

60

70

80

90

100

110

120

130

Throttle PositionTorque

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

RFAVLTEOM

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

Time [hh:mm]

Torq

ue [f

t-lb]

TE

OM

[μg]

, AVL

(In

tegr

ated

, mg)

AV

L M

SS [m

g/m

^3]

RF

(Der

ivat

ive)

Th

rottl

e [%

] R

F Si

gnal

[Raw

]

Raw RF signal vs. TEOM and AVL (Integrated)

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R2 = 0.984

0

2

4

6

8

10

12

14

16

18

0 10 20 30 40 50 60

Ash Load [g/l]

Freq

uenc

y S

hift

[MH

z]

• Ash loading level equivalent to ~ 380,000 miles of on-road accumulation

• Frequency shift at resonance well-correlated to ash level in DPF

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 10 20 30 40 50 60Ash Level [g/L]

Del

ta_P

[kP

a]

Pressure Drop

Δf ~ 20 MHz with 60 g/L of ash

Δf

Frequency Shift Well-Correlated to DPF Ash Levels

R2 = 0.98

Images: SAE 2007-01-0920

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DPF Soot Load Measurements with Ash

0

2

4

6

8

10

12

14

16

18

20

22

24

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0 1 2 3 4 5 6 7Gravimteric Soot [g/L]

RF_Ash 0gRF_Ash 10gRF_Ash 20gRF_Ash 30gRF_Ash 40gRF_Ash 50g1:1dP_Ash 0gdP_Ash 10gdP_Ash 20gdP_Ash 30gdP_Ash 40gdP_Ash 50g+0.5 g/L-0.5 g/L

0

3

6

9

12

15

0 10 20 30 40 50Ash Load [g/L]

PM

Loa

d [g

/L]

RF dP

ΔP

RF

Soot

[g/L

], Δ

P So

ot [g

/L]

+ 0.5 g/L

RF and dP (ΔP) measurements both scaled to 0 g/L ash case to develop simple calibration function 3 g/L PM

Comparison

ΔP regeneration frequency increases with ash (over-estimate PM load)

30g 20g 40g 50g 50g

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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 2000

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

Unnecessary Regeneration

Regeneration Complete

DPF

Soot

Load

[% T

arge

t]

Aver

age

DPF

Tem

pera

ture

[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