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Portable Emission MeasurementStrategy

U.S. EPAOffice of Transportation and Air Quality

February 13, 2002

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Why Not the Lab?

• Accuracy

• Cost

• Practicality

• Sample Bias and Recruitment

• New Technology is Available

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1

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4

5

6

7

8

9

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Bus377 Bus363 Bus383 Bus364 Bus372 Bus361 Bus380 Bus381 Bus384 Bus379 Bus375 Bus360 Bus385 Bus386 Bus382

Avera

ge N

Ox (

g/b

hp

-hr)

On-Road Bus Data Emission Standard MOBILE6

On-Road Data On 15 1996 MY Urban Buses:36% higher than standard52% higher than MOBILE6 prediction from cert data

Real World Bus Emissions

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Second-by-Second Cold StartData

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Accel More Important

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Better Data Collection Methods

• Data collection is expensive– Recruiting costs from $2,000 to $100,000 per engine

– Data collection budgets have diminished dramatically

• New approach and changes in datacollection needed– Laboratory based recruitment and testing is a

compromise both in terms of sampling and geography

– Laboratory testing regimes don’t reflect real world, in-use operation of vehicles and engines

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FTP

Real World vs. Lab

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Measuring Emissions in the Field

• Portable emission measurement systems– Allows us to bring the lab to the car or engine and test it on

the road or in the field under normal operating conditions• These conditions are not adequately represented by laboratory driving

cycles and “correction” factors used in models

• Shows both how and where emissions are generated

– Frees us from the few laboratories around the country• We can test anywhere, any time

– Reduces problems related to sampling and modeling• Can test anything we can recruit

• Less intrusive technology increases chances of high recruitmentparticipation

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Emissions Where They Occur

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Technology Development

• Goals– Bring technology to market– Make accurate, accepted equipment readily available– Specify EPA needs so manufacturers can respond

• Approach– Cooperative Research and Development Agreements

• Measure gasoline and diesel emissions• Operate unattended for extended periods of time• Accuracy requirements approach lab measurement• Goal is to have commercially available products in ~6 months

– OTAQ lab and contractor development• PM and toxics measurement capability• Measurement strategy development

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MAF(V)

Linear Calibration

Cubic Calibration

O2(V)

NOx(V) NOx(ppm)

O2(%)

MAF(scfm)

TMAF(mV) TMAF(C)

Texh(mV) Texh(C)

RH(V)

Pbarom(V)

Tamb(mV) Tamb(C)

RH(%)

Pbarom(kPa)

Alt Freq(Hz) Eng Spd.(rpm)

CO2(%)

Exh.Flow(scfm)

FuelFlow(g/hr)

Power(bhp)

BSNOx(g/bhp-hr)

Emissions Calculations

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SPOTSimple Portable Onboard Test

• Magnetic mounts

• Heavy-duty locks

• Cellular, GPS, & CAN capability

• Zirconia sensor: total-NOx & O2

• Unique exhaust flow measurement

• Fuel-specific & mass rateemissions

• Brake-specific emissions based onpower estimate

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EPA-supported innovation

MAFsensor

Airflow in

Partialexhaustflow

Annulareductor

NOx/O2

sensor

§Low pressure drop§Fast response§Durable sensors§Linear calibration§Self-cleaning

Non-roadExhaust Flow Measurement

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Non-road Exhaust Flow Device

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ExhFlow(scfm)=(C1(Dexh/Dmeter)2+C2)*MAF*(Tmafabs/Texhabs)0.5

FuelFlow(g/hr)=ExhFlow*CO2/100*(12.01+H:Cratiofuel*1.008)(g/mol)*60(min/hr)*1.178(mol/scf)

In-Use vs. Laboratory Exhaust Flow

0

200

400

600

0 200 400 600Laboratory Exhaust Flow (SCFM)

In-u

se

Ex

ha

us

t F

low

(S

CF

M)

-10%

+10%

In-Use vs. Laboratory Fuel Flow

0

10000

20000

30000

40000

50000

0 10000 20000 30000 40000 50000

Laboratory Fuel Flow (g/hr)

In-U

se F

uel F

low

(g

/hr)

-10%

10%

Fuel and Exhaust Flows

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CO2(%)=(20.99*(1-(RH/100)*(Psat/Pbarom))-%O2-0.55*(NOx/10000)/(1+0.3025*(H:Cratiofuel))

Psat(kPa)=1.775E-9*Tamb5+3.687E-7*Tamb

4+2.483E-5*Tamb3+1.395*E-3Tamb

2+4.578*E-2Tamb+.6031

In-Use vs. Laboratory NOx Concentration

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200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200 1400

Laboratory NOx (ppm)

In-U

se N

Ox (

pp

m)

+5%

-5%

In-Use vs. Laboratory CO2 Concentration

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2

4

6

8

10

0 2 4 6 8 10

Laboratory CO2 (%)

In-U

se

CO

2 (

%)

+5%

-5%

Emissions Concentrations

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Flow Device Version 3

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Flow Device Version 3

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Nonroad Emissions Data

0100200

300400

500600700

4800

0

4822

9

4845

8

4868

7

4891

6

4914

5

4937

4

4960

3

4983

2

5006

1

5029

0

5051

9

5074

8

5097

7

Seconds of Vehicle Operation

NO

x (

pp

m)

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PM Development

• Developing related measurement capability– Proportional sampling system

– Humidity conditioning of exhaust sample

– Preclassifier

• Evaluating continuous PM monitoring– Quartz crystal microbalance

– Tapered element oscillating microbalance

• Time line– Expect prototype evaluations completed by Summer