Assessment of a laser-induced incandescence sensor for real-time particulate emissions measurement

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Proceedings of the 18th CRC On-Road Vehicle Emissions Workshop, 2008, 2008

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Assessment of a laser-induced incandescence sensor for real-time

particulate emissions measurement

Gujarathi, Ritesh C.; Kumar, Virendra; Shimpi, Shirish A.; Bachalo, William

D.; Smallwood, Gregory J.

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Institute for

Chemical Process

and Environmental Technology

Motivation

• Support increased technical productivity by developing process technology to more effectively and efficiently estimate concentrations of particulate matter (PM) in Diesel engine exhaust

• This will enable the further development of emissions compliant engine products

–Develop efficient and effective soot management and dosing strategy for DPF’s

–Develop effective engine calibrations for reducing PM levels at different engine conditions –Facilitate further development of emissions

compliant engine products

Background

• Currently “Gravimetric PM Sampling System” is used to measure PM, which is not real-time

• Laser Induced Incandescence (LII) is a real time, non-intrusive soot measurement techniques for rapid characterization of diesel particulate emissions • The LII method has the advantage of being able to

sample and report particulate emissions from either the direct exhaust or from a dilution tunnel facility

Approach

• In the present investigation, the LII instrument was evaluated extensively at the Constant Volume Sampling (CVS) emission laboratory at the Cummins Technical Center, where a Cummins’ standard gravimetric PM measurement system is available as a comparative standard

• Collaborative efforts between Cummins Inc. and Artium Technologies are ongoing with the goal of advancing the LII capability for measuring real time soot at pre- and post DPF locations at transient and steady state engine operating conditions

Artium LII-200 Instrument

• LII technique evaluated was developed and patented by NRC Canada • Artium Technologies Inc.

commercialized LII-200 • LII-200 has 4 sub-systems:

–LII power supply –Gas Flow Controller –LII Sensor Head –On-board computer with

AIMS software (Advanced Instrument Management Software)

LII Advantages and Features

• Measures real-time soot concentration (ppb & mg/m3₎

• Sample dilution not required, can be used to estimate SVF in raw exhaust

• Insensitive to presence of other emission gas species • Data recording frequency: 1–20 Hz and connectivity

with host data acquisition system • Ease of operation, portable to transport and

maintenance free working • Absolute intensity calibration

• High resolution (0.01mg/m3_{) and high repeatability}

(2-5%)

Example AIMS results from LII-200

Soot mass concentration (mg/m3) vs. time (s)Data summary [Top – validated particle size (counts vs. size); Below – validated mass concentration histogram (counts vs. mg/m3) ]

Comparison Between Two LII-200 Instruments

Initial LII Steady State Response

Five-mode steady-state tests with 3 repeats

• LII steady-state response higher by ~ 1.7-2.5 * TPM • Short-term steady-state repeatability (COV) –LII: 3-7% –Gravimetric TPM: 2-5% –SOF extracted PM: 3-25%

PM mass (gm) representation for 5 mode s/s tests (with 3 repeats)

Initial Transient Response

LII transient test response, hot FTP cycle (20 min.)

Five repeats of LII transient test response, hot FTP cycle (20 min.)

5 repeats of LII response vs. speed and torque for transient tests, hot FTP cycle (20 min.)

PM emissions (gm) from five repeats of transient testing

• LII transient response higher by 1.6 * TPM and 2.0 * SOF extracted PM

• Short-term transient repeatability (COV)

–LII: 3.5%

–Gravimetric TPM: 2.1% –SOF extracted PM: 5.3%

Latest Results with Correct Calibration

• An issue was discovered with the neutral density filters in the LII instrument; it was recalibrated on-site

–LII now is reporting lower SVF values than TPM

• At high load, in both diluted and raw exhausts, LII measures about 95% of Dry PM from diluted exhaust measured by the Cummins Gravimetric method • At low load, in raw exhausts, LII measures higher

(ranging from 1.1 to 3 times), and in diluted exhaust substantially lower, as compared to Dry PM from diluted exhaust measured by the Cummins Gravimetric method

• Above graph shows the historical development of LII system at Cummins. This involved combined partnership to work with Artium and NRC to resolve sampling and instrument issues including: Leak in the system, software issues, improving sampling system, correcting Neutral Density filter issues

• There is still work in progress to further refine the system to expected traceability and accuracy

Critical Parameter Measurement

• Cummins, Artium, & NRC worked during the on-site visit at Cummins (13-15 Nov’07) to identify sources of uncertainty

Summary

• LII current status:

–The LII technique is capable of monitoring PM emissions by estimating soot concentration and primary particle size

–The currently implemented improvements to the LII resulted in repeatable measurements of soot volume fraction from the LII with a short term Coefficient of Variation (COV) of 3-7% for steady state cycles and a COV of 3-5% for FTP transient cycles for the equivalent gravimetric PM level ranging from 0.01 to 1.00 g/bhp-hr –The correlation between time-integrated LII

signals and the standard gravimetric PM measurement system was found to be robust with a correlation regression coefficient ranging from 96%-99.8%

–LII has been tested for Steady States,

Transients, Raw Exhaust, PM Trap-out

–LII reported similar readings compared to Dry PM measured using Cummins gravimetric method at higher load conditions, and much lower to about 0.9 to 3 times at low load conditions –LII-200 is nearing readiness for Prime Testing –

Expected in the near future

• Work Ahead:

–Reliable calibration of Neutral Density filters from

3rd_{party laboratory}

–Determine most appropriate values of Soot Absorption Function E(mλ) and relative absorption function

–Ongoing work to increase sensitivity through improved signal averaging and processing –Packaging – Feasibility of installing exhaust gas

Sampling System to control volumetric flow and pressure in the sample cell

Assessment of a Laser-Induced Incandescence Sensor for

Real-Time Particulate Emissions Measurement

Ritesh C. Gujarathi

_{, Virendra Kumar}

_{, Shirish A. Shimpi}

_{, William D. Bachalo}

_{, and Gregory J. Smallwood}

a_{Cummins Technical Center, Cummins Inc., 1900 McKinley Ave, Columbus, IN – 47201} b_{Artium Technologies Inc., 150 West Iowa Ave, Sunnyvale, Unit 202, CA – 94086} c_{National Research Council, Bldg. M-9, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada}

18thCRC On-Road Vehicle Emissions Workshop San Diego, California, March 31 – April 2, 2008

LII Comparison 0 1 2 3 4 5 6 7 8 9 10 11 12 0 1 2 3 4 5 6 7 8 9 10 11 12 LII #1, mg/m3 LI I # 2 , m g/ m 3 1 2 3 4 5 Mode change 1 2 3 4 5 Insoluble PM mass I Insoluble PM mass II Insoluble PM mass III

PM system I PM system II PM system III LII I LII II LII III 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 PM ma ss (g m)

Steady State points

1 2

3 4

5 Insoluble PM mass I

Insoluble PM mass II Insoluble PM mass III

PM system I PM system II PM system III LII I LII II LII III 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 PM ma ss (g m)

Steady State points

1 2 3 4 5 1 2 3 4 5 0 5 10 15 20 25 30 35 40 45 50 3000 3200 3400 3600 3800 4000 4200 4400 4600 4800 5000

datapoints for 1200 sec (recording frequency - 5 Hz)

C on cen tr at io n ( m g /m ³) -3,000 -2,500 -2,000 -1,500 -1,000 -500 0 500 1,000 1,500 2,000 S pe ed (R P M ) a nd Tor que (lb-f t)

Hot FTP-1 Hot FTP-2 Hot FTP-3 Hot FTP-4 Hot FTP-5 Speed Torque High Repeatability with a COV of 4% 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 1 2 3 4 5 PM ( g m) 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 BS CV S P M E m is s ions (g m /bhp-hr)

Insoluble PM mass (gm) BS CVS PM Emissions (gm) LII PM Emissions (gm) 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 1 2 3 4 5 PM ( g m) 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 BS CV S P M E m is s ions (g m /bhp-hr)

Insoluble PM mass (gm) BS CVS PM Emissions (gm) LII PM Emissions (gm)

Correlation Development Correlation Development

LII Total soot mass (gm)

LII

Total soot mass (gm)

Gravimetric PM system Gravimetric PM system

Exhaust sample Press. & Temp.

Exhaust sample Press. & Temp.

Sampling frequency (Hz) Sampling frequency (Hz) LII concentration(mg/m3) LII concentration (mg/m3) CVS flow rate (scfm or m3/sec) CVS flow rate (scfm or m3/sec) Total & insolubleTransient

PM mass (gm)

Transient Total & insoluble PM mass (gm)

Steady State

Total & insoluble PM mass (gm)

Steady State Total & insoluble PM mass (gm) AIMS signal processing for estimating SVF AIMS signal processing for

estimating SVF Laser PropertiesLaser Properties Incandescence measurement Incandescence measurement Operating conditions (Gas chamber) Operating conditions (Gas chamber)

Single shot / Multi Pulse Analysis Fixed / Dynamic

Single shot / Multi Pulse Analysis Fixed / Dynamic Auto Gain ErrorAuto Gain Error

STP Compensation

STP Compensation Soot density

(gm/cc) Soot density (gm/cc) Neutral Density Filter calibration Neutral Density Filter calibration Absolute Light Absorption function E(mλ) Absolute Light Absorption function E(mλ) Laser properties Profile Uniformity Laser properties Profile Uniformity PM Wave length

Center / width

PM Wave length Center / width S/N ratio

in concentration S/N ratio in concentration Probe volume: Width of Laser Sheet Probe volume: Width of Laser Sheet Sample cell Temperature Sample cell Temperature Sample cell pressure Sample cell pressure Soot Temperature Soot Temperature Calibration Factor n(λ) Calibration Factor n(λ) Relative Absorption Factor E(mλ1) / E(mλ2) Relative Absorption Factor E(mλ1) / E(mλ2) Photomultiplier signals and calibration Photomultiplier signals and calibration Optical Contamination Optical Contamination Maintain Laser fluence Maintain Laser fluence

Purge Air dilution to sample

Purge Air dilution to sample

Source of Uncertainty

Error

LII Sampling Dilute Exhaust

1.2278 0.2269 1.0427 0.1412 1.0665 0.0045 1.0326 0.0052 0.2518 0.0596 0.2513 0.0631 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 0 1 2 3 4 5

Steady state points

PM ( g m) 0.00 0.05 0.10 0.15 0.20 0.25 0.30 B S C VS P M Em is s io n s (g m/ bh p -h r)

LII PM Emissions (g) CVS PM Emissions (g)

CVS Dry PM (g) BS CVS PM Emissions

LII Sampling Raw Exhaust

0.8052 0.3020 1.1034 0.2073 0.8724 0.4543 0.8886 0.4389 0.2685 0.0578 0.2801 0.0583 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 0 1 2 3 4 5

Steady state points

PM (g m) 0.00 0.05 0.10 0.15 0.20 0.25 0.30 B S C V S P M E m is sion s ( gm /bh p-hr )

LII PM Emissions (g) CVS PM Emissions (g)

CVS Dry PM (g) BS CVS PM Emissions

Historical Development of LII 200 at Cummins Using Baseline Engine at CVS Lab ISB ISM 2004 Model

0 4 8

17-Jun-07 06-Aug-07 25-Sep-07 14-Nov-07 03-Jan-08

P ar tic ul at e M a ss ( g ) 0 10 20 30 40 LII (g) CUM_PM (g) Cum_Gravimetric_Dry LII (g) before NDFI

Neutral Density Calibration Window getting Dirty and Calibration