Real-Time Catalyst Monitoring and Diagnostics using Radio Frequency Sensors

Paul Ragaller, Alexander Sappok, Leslie Bromberg, CTS Corporation

Josh Pihl, Oak Ridge National Laboratory

October 2017

2

Project Objectives

Remove Technical Barriers of aftertreatment-related fuel consumption

and improve system durability, reduce system cost and complexity.

Develop RF Sensing Platform for direct measurements of catalyst state for

clean diesel, lean gasoline, and low temperature combustion modes.

The Specific Objectives of this Project Include:

1. Develop RF sensors and evaluate the feasibility of RF sensing for the following catalysts and applications:

• Selective Catalytic Reduction (SCR): Ammonia storage, diesel & gasoline

• Three-Way Catalyst (TWC): Oxygen storage, gasoline

• Hydrocarbon Traps: HC storage, low temperature combustion

2. Develop implementation strategies for the most promising applications to enable low-cost and robust emission controls to enable advanced combustion engines.

3. Demonstrate and quantify improvements in fuel consumption and emissions reduction through RF sensing in engine and vehicle tests with industry and national laboratory partners.

Technology Overview and Concept

3

CONCEPT: Multi-function RF sensing platform to enable more robust and more efficient emission controls for gasoline, clean diesel and advanced low temperature combustion modes.

Technology Assessment

Sensor Type NOx or O2 Ammonia Soot (PM) RF Sensor

Applications NOx or O2 Only NH3 Only PM Only NH3, O2, NOx, HC, PM, Ash

Catalyst State Model/Estimate Model/Estimate Model/Estimate Direct Measurement

Sensing Element Active Active Active Passive

• Direct measurement of multiple catalysts

• Adaptive feedback controls adjusts as system ages

Current systems use many different types of exhaust gas sensors.

DOE Supported Test Program: Project Partners

4

•Production gas sensors

•Storage models

•Gravimetric (PM/Ash)

•Production gas sensors

•Emissions bench (FTIR)

•Storage models

•Emissions bench (FTIR)

•Adv. Instruments Spaci-MS

•Catalyst models

•Stock Volvo/Mack SCR controls

•On-road durability

•Develop RF sensors

•Sensor calibration

• Catalyst aging

•Advanced substrates

•Model catalysts

•HD engine dyno testing

•Catalyst bench testing

•Model validation

•Engine dyno testing

•On-road fleet test

•Volvo/Mack trucks (SCR+DPF)

•18 Months total, 2 trucks

Team Member Contributions Performance Metric

• System requirements

• Production sensors

• In-house models

•OEM technical advisors

•Catalyst samples

•Design of experiments

•Parallel testing

Catalyst Configurations Evaluated

5

Catalyst Condition Application Baseline Test Conditions Facilities

SCR Degreened Cummins 8.9L ISL (2015)

N2, Air 25 °C – 400 °C NH3 Storage 150, 200, 250, 300, 350, 400°C

CTSORNL

SCRF Degreened Non-Production[VW]

N2, Air 25 °C – 400 °C NH3 Storage 250°C CTS

SCRF Soot / Ash Non-Production[VW]

N2, Air 25 °C – 400 °C NH3 Storage 250°C CTS

TWC Degreened GM Malibu 2L DI(2016)

N2, Air 25 °C – 400 °C O2 Storage, Lean / Rich Pulses (C3H8)

CTSORNL

TWC Degreened Chrysler V8 (2016)

N2, Air 25 °C – 400 °C O2 Storage, Lean / Rich Pulses (C3H8)

CTS

HC Trap TBD Non-Production To be completed To be completed ORNL

General Catalyst Test Conditions

• Reference / baseline testing with air and inert conditions to characterize RF signal response to catalyst over temperature range

• SCR: 5-13% H2O, CO2; 0-10% O2; 0-2% CO, H2; 0-800 ppm HC, NH3

• SCRF – soot/ash loading from exhaust of diesel engine and burner

• TWC: 5-13% H2O, CO2; 0-10% O2; 0-2% CO, H2; 0-800 ppm NO; 0-0.3% HC

Same catalyst core samples used with all project partners and for engine testing in Phase II.

RF Cavity Simulations Developed and Validated

6

(A)

(C)(A) (B) (C)

Simulated Cavity Resonances

Results of Cavity Electric Field Simulations

(B)

Frequency

Catalyst Core

RF Cavity

S1

S2

Higher Order Modes

• Electric field distributions provide spatial sensitivity to monitor local storage of gas species

• Potential to monitor location of stored ammonia (front back of SCR)

Bench Reactor Systems for Catalyst Evaluations

NH3, Nox, O2

Sensors

Temp Sensor

VNA RF Software

CatalystFurnace

FTIR

ORNL Bench Reactor Setup for RF Calibration

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Mixture Preparation• N2, NO, NH3, O2, H2O,

CO, CO2, HC• Temp: 100 – 550 °C• Flow: 0 – 100 slpm

Heaters

AB

C

ATemp

Sensor

B

RF Antennas

B

C

DEF Vessel

Water Vapor

CTS Reactor Setup Mimics Production System Configuration for Performance BenchmarkingUsed for comparison of RF vs production exhaust sensors

Sensors• RF Sensor• NOx/O2, λ• NH3 Sensors

RF Sensor Calibration• ORNL bench reactor• Gas mixture control and FTIR

measurements pre- / post- catalyst• Standard test protocols for catalyst

preconditioning, loading, and desorption tests

• Calculated NH3, O2 storage levels supplied as reference for RF sensor calibration of SCR and TWC

• Standard core samples used at ORNL and CTS

RF Response to Ammonia Storage on SCR

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Mode 1

Mode 2

Mode 3

Mode 4

Mode 5

Catalyst Bench Reactor Testing Confirmed NH3 Impact on RF Signal

• Maximum 5 dB reduction in signal amplitude with NH3 storage

• Fully-desorbed state (sharp resonant modes) – No ammonia storage

• Reduction in amplitude and shift in frequency with ammonia storage

SCR core samples evaluated on bench reactor at CTS and ORNL

Ammonia Storage

Ammonia storage measurements demonstrated on laboratory bench reactor

No NH3

NH3

Loaded

Temperature Compensation of SCR: System Calibration

RF sensor calibrated for SCR performance using a series of desorption isotherm tests

• Catalyst loaded to saturation, then ammonia injection is reduced to allow for desorption

• High-temperature SCR regeneration performed between desorption isotherms

• RF response measured at each temperature to allow for incorporation of temperature compensation

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250ᵒC Isotherm150ᵒC200ᵒC 250ᵒC

Catalyst Temperature

RF Signal

Ammonia Inventory

Raw RF signal well correlated to each ammonia desorption step

RF

Sign

al [

dB

]

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

0.0 0.5 1.0 1.5 2.0 2.5

RF

Ma

gn

itu

de

Pa

ram

ete

r

NH3 Inventory [g/L]

Ammonia Inventory Measurement with RF

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Go / No-Go Decision Criteria Achieved:• Developed RF calibration for ammonia storage

measurements including temperature compensation within 10% of full-scale

• Calibrated RF sensor for the SCR has a mean measurement error of 0.000 g/L and a standard deviation of 0.036 g/L

0

200

400

600

800

1000

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05 0

0.05 0.

10.

15 0.2

0.25 0.

3

RF Error [g/L]

Fre

qu

en

cy

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5

RF

In

ve

nto

ry [

g/L

] .

NH3 Inventory [g/L]

150C

200C

250C

300C

350C

Oxygen Storage Readily Detected on TWC

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Mode 1

Mode 2

Mode 3

Mode 4

Mode 5

Large RF Response to Change in TWC Oxidation State

• Lean Conditions: Oxygen storage inhibits Ce conductivity (sharp resonances)

• Rich Conditions: Oxygen depleted state results in large dielectric loss

• Impact on specific resonances function of local electric fields

TWC core samples evaluated on bench reactor at CTS and ORNL

Oxygen storage measurements confirmed on laboratory bench reactor

Oxygen Depletion

Response to TWC O2 Storage / Depletion

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RF Resonances

• RF resonance response to O2

depletion

• Modes respond quickly when HC added to system and stored O2 on catalyst is consumed

• Characteristics of each mode vary, possibly indicating spatial sensitivity of signal to O2

consumption

0

40

80

120

160

200

240

280

320

360

400

-0.3

5-0

.3

-0.2

5-0

.2

-0.1

5-0

.1

-0.0

5 00.

05 0.1

0.15 0.

20.

25 0.3

0.35

O2 Measurement Error [g/L]

Fre

qu

en

cy

Oxygen Inventory Measurement on TWC

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TWC Calibration Developed• Developed RF calibration for oxygen storage

measurements including temperature compensation within 10% of full-scale

• Calibrated RF sensor for the TWC has a mean measurement error of 0.000 g/L and a standard deviation of 0.040 g/L

1

1.2

1.4

1.6

1.8

2

2.2

2.4

0 0.2 0.4 0.6 0.8 1 1.2

O2 Inventory [g/L]

RF

Ma

gn

itu

de

Pa

ram

ete

r

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 0.2 0.4 0.6 0.8 1 1.2

O2 Inventory [g/L]

RF

O2

Me

asu

rem

en

t [g

/L] 250C

350C

450C

Summary

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RF Sensor Catalyst Application Feasibility Study

• Developed production-intent RF sensors

• Applied models for RF cavity response to guide experimental design and data analysis

• Coordinated experiments with industry and national lab project team

• Confirmed feasibility to directly measure stored ammonia on SCR and oxygen on TWC

• Developed initial SCR and TWC RF sensor calibrations to meet project accuracy targets

• Demonstrated NH3 storage measurements from 0 to 2.5 g/L with 2σ = 0.072 g/L [lab]

• Started vehicle fleet testing on heavy-duty and medium-duty vehicles

• Conducted systematic analysis of noise factors for RF measurements

Outlook and Project Impact

• RF sensing may provide a paradigm shift for emissions control by providing a direct measurement of catalyst state – optimize control and system diagnostics

• Robust and low cost emission controls are needed to overcome key barriers limiting the widespread use of advanced combustion engines

Acknowledgements

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• This material is based upon work supported by the U.S. Department of Energy DE-EE0007214

• Roland Gravel, Ken Howden, and Gurpreet Singh

• Jason Conley from NETL

• The authors are grateful to collaborations and input from the following project partners:

• Corning Incorporated (Filter and Substrate Materials Evaluation)

• Oak Ridge National Laboratory (Catalyst / Filter Testing)

• Daimler Trucks North America, Cummins, FCA (OEM Advisors)

• New York City Dept. of Sanitation (Fleet Testing)

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.