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Nanoparticles from road vehicle Nanoparticles from road vehicle exhaust: an artefact or a reality?exhaust: an artefact or a reality?

Diane Hall BP/CONCAWEDiane Hall BP/CONCAWE

Lemnos Meeting: Round Table Discussion

11th September 2003

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Purpose of DiscussionPurpose of Discussion

To examine data which demonstrates the emission of nanoparticles from vehicles and engines

To understand whether these measurements reflect genuine real-time engine emissions or are affected by sampling and/or methodology

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concawe light duty investigationconcawe light duty investigation

Source: CONCAWE Report 98/51; SAE paper 982600

•First research – had no explanation for consistency of distribution between vehicles

•Possible explanation is that we were not seeing genuine engine emissions

Source: concawe report 98/51

Gasoline vehicles at 120km/h

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Diesel vehicles

No. / km

10**10

10**11

10**12

10**13

10**14

10**15

50 km/h 120 km/h Hot MVEG

Gasoline vehicles

Total number of particles emitted per Total number of particles emitted per kilometer for each vehiclekilometer for each vehicle

Source: CONCAWE Report 98/51; SAE paper 982600Source:concawe report 98/51

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• Accumulation mode particles stabilise instantaneously• Nucleation mode particles take time to stabilise

Stabilisation time is importantStabilisation time is important

Source: concawe report 01/51

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• Accumulation mode unaffected by dilution ratio• Nucleation mode sensitive to dilution ratio• Temperature (rather than dilution ratio) is believed to be the dominating influence on

nucleation particle formation

Nucleation mode sensitive toNucleation mode sensitive to temperaturetemperature

Source: concawe report 01/51

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0.0E+0

2.0E+8

4.0E+8

6.0E+8

8.0E+8

1.0E+9

1.2E+9

1.4E+9

1 10 100 1000

Particle Diameter (nm)

Dilu

tio

n C

orr

ec

ted

Co

nc

en

tra

tio

n (

dW

/dlo

gD

p)/

cm

3

MODE1;R49#1

MODE7;R49#1

MODE13;R49#1

DETR/SMMT/CONCAWE Particulate Research Programme

•Size of idle mode appears dependent on preceding test condition

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Implications from studiesImplications from studies

Nanoparticles are emitted from Gasoline vehicles at high speed, independent of fuel and vehicle technology

Nanoparticles emitted during heavy duty engine testing are sensitive to sampling conditions

Nanoparticles measured during heavy duty testing are sensitive to preceding engine history

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BP Study – gasoline particle emissions at BP Study – gasoline particle emissions at 120km/h (measured over a week)120km/h (measured over a week)

Source: SAE 2000-01-2957

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Relationship of particle emissionsRelationship of particle emissionswith temperaturewith temperature

Source: SAE 2000-01-2957

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On-road testsOn-road tests

Source: SAE 2000-01-2957

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IndicationsIndications

continual running at high speed was ‘clearing’ the system of particles

material appeared to be laid down on surfaces at cooler conditions with particle release appearing to be temperature related

Hypothesis tested with cut off piece of exhaust sampling pipe

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Tests on old exhaust pipeTests on old exhaust pipe

Source: SAE 2000-01-2957

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TEST PROGRAMMETEST PROGRAMME

Vehicle: VW Golf 1.9l TDi, with and without oxicat

Fuels: Current EN 590 (300ppm S) Swedish Class 1

Chassis Dynamometer at BP, with measurements by AEA Technology SMPS (7-320nm); UPM total count >3nm

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RESULTSRESULTS

At road load, no nucleation particles were observed at any of the test conditions, with either fuel and independent of the presence of the catalyst

Tests were repeated at high load (30kW)

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Summary of High Load Tests at 50km/hSummary of High Load Tests at 50km/h

0.0E+00

1.0E+08

2.0E+08

3.0E+08

4.0E+08

5.0E+08

6.0E+08

7.0E+08

8.0E+08

9.0E+08

1.0E+09

EN590 EN590+CAT Swedish Swedish+CAT

Part

icle

concentr

ation [#/c

c]

SMPS

UPM

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SummarySummary

Nucleation particles were not seen under any test condition at road load

Nucleation particles were only seen at high load with the catalyst in place appear to be temperature related

Test sequence and pre-conditioning critical

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‘System release’ during heavy-duty sampling

0.0E+00

5.0E+12

1.0E+13

1.5E+13

2.0E+13

2.5E+13

3.0E+13

3.5E+13

4.0E+13

4.5E+13

5.0E+13

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Parti

cle

Con

cent

ratio

n [#

/cc]

System burn off

Stabilisation following fitting of ‘loaded’ trap

Source: SAE 2003-01-3167

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Conclusions (1)Conclusions (1)

The formation of nanoparticles (nucleation mode) is extremely sensitive and varies with sampling (temperature, dilution, humidity); thus repeatable measurement requires tight control and carefully defined conditions

High concentrations of small particles have been measured from gasoline vehicles operating at high speeds and from Diesel vehicles at high load

These particles have been shown to be strongly linked to the temperature of both the exhaust and sampling system

Material emitted from the engine is deposited on cool surfaces and released as particles as the temperature profile increases

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Conclusions (2)Conclusions (2)

Sustained periods of high temperature will ‘clean’ the system and reduce the number concentration to that measured at low speed

Subsequent operation at progressively higher speeds will result in further release of deposited material

The measurement of particle numbers is strongly dependent on the pre-history of both vehicle and sampling system

Further research continues to be needed to understand the formation mechanism and atmospheric fate of nucleation particles