1

10th ETH-Conference on Combustion Generated Nanoparticles21st -23rd August 2006

Characterization of particles emitted from modern 2- stroke scooters by electron microscopy and tandem DMA

D. Etissa, D. Schreiber, M. Mohr

Laboratory for internal combustion engines, EMPA, Switzerland

2

Outline

Motivation and background

Experimental setup

Investigated 2- stroke scooter

Results

- DMA, TEM

Conclusion

3

Motivation

Significant emissions and pollution effects of 2-stroke engine

Structure and composition of exhaust particles are not well known

4

Source: Particle emission of different combustion sources, Dept. IC. , EMPA (Diesel passenger car, 50km/h)

Source: Emission Factors & Influences on Particle Emissions modern 2-Stroke Scooters. Final rep. BUWAL / VLR.03.05 (50 cm3, speed 30 km/h with catalytic converte, Oil : Panolin Synth Aqua gasoline)

J. Czerwinski, Dipl. Ing. Dr. techn.

Measurements on dynamometer

Diesel passenger car2-stroke scooter

Motivation and background

Dp [nm]

0.0E+00

1.5E+07

3.0E+07

4.5E+07

6.0E+07

10 100 1000Dp [nm]

dN/d

logd

p [1

/cm

3]

5

To get a better understanding of the nature of the particles emitted from two stroke scooters

Influence of engine technology on the emitted particles

Influence of catalytic converter on the emitted particles

Objective

6

Investigated 2 –stroke scooters

Methods for particle analysis

• SMPS ( 7 to 322 nm )

• Tandem DMA

• Thermodesorber (25 – 400°C)

• TEM – EDX

• Cryo electron microscopy

Measuring procedures

• constant speed: 60 km/h

• before and after catalytic converter

• raw gas sampling

• quick two step dilution (first stage heated to 150 °C)

3.94.8Power [kW]

CarburetorDirect injection

20012002Model [Y]

49

Kymco

49

Peugeot

Displacement [cm3]

7

Experimental Setup - I

Electrometer

Scooter

CatalyticconverterTest bench

Dilution

Bypass

High tension

TD

SMPS

N

Coronacharger

TEM sampler

P

Pump

pump

Sheath air

Fan

Electrostatic sampler

TEM-grid

CPC

CPC

8

Schematic diagram of the Tandem DMA

DMA-1

N

Sheath air

CPC DMA-2

CPC

1.5 lpm

Excess air

TD

N 9.1 lpm

12.25 lpm

Sheath air

1.5 lpm

Excess air

Bypass

Experimental setup - II

9

0.0E+00

3.0E+08

6.0E+08

9.0E+08

1 10 100 1000Dp [nm]

dN/d

logd

p [c

m^-

3]

amb. 25°C

100°C

200°C

400°C

0.0E+00

6.0E+07

1.2E+08

1.8E+08

1 10 100 1000Dp [nm]dN

/dlo

gDp

[cm

^-3]

amb. 25°C

100°C

200°C

400°C

Carburetor

Before Cat

After Cat

Particles sampled before catalyst are more volatile thandownstream of it

SMPS Results

10

0.0E+00

3.0E+08

6.0E+08

9.0E+08

1.2E+09

1 10 100 1000Dp [nm]

dN/d

log

dp[c

m^-

3]

amb. 25°C

100°C

200°C

400°C

0.0E+00

5.0E+07

1.0E+08

1.5E+08

1 10 100 1000Dp [nm]

dN/d

log

dp[c

m^-

3]

amb. 25°C

100°c

200°C

400°C

SMPS Results 2- stroke direct injector

Thermal treatment strongly provoke evaporation

of the particles

After Cat

Before Cat

TSDI°

0.0E+00

3.0E+06

6.0E+06

9.0E+06

1 10 100 1000

DP [nm]

DN

/dlo

gdp[

1/cm

^3]

Beofe cat-400 °C

After cat- 400 °C

11

0

30

60

90

25 100 200 400Temp. [°C]

Volu

me

[%]

before Cat

After Cat

0

30

60

90

25 100 200 400Temp. [°C]

Volu

me[

%]

Before Cat

After Cat

Effect of catalytic converter

Carburetor

Direct injector

relative volume loss of the particles emitted by 2- stroke scooters (DI, Carburetor) sampledupstream of the catalyst were higher than that of the downstream of the catalyst

12

K-20 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Dp [nm]

Nor

mal

ized

dN

/dlo

gdp 25°C

100°C

200°C

400°C

K-30 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Dp [nm]

Nor

mal

ized

dN

/dlo

gdp 25°C

100°C

200°C

400°C

highly volatile and no indication of solid core

K-13 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Dp [nm]

Nor

mal

ized

dN

/dlo

g dp

25°C

100°C

200°C

400°C

Tandem DMA Carburetor- after catalyst

13

P-16 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Dp [nm]

Nor

mal

ized

dN

/dlo

gdp

25°c

100°C

200°C

400°C

P-25 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000

Dp [nm]

Nor

mal

ized

dN

/dlo

gdp 25°C

100°C

200°c

400°C

P-55 nm

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Dp [nm]

Nor

mal

ized

dN

/dlo

gdp

25°C

100°C

200°C

400°C

Tandem DMA

Direct injector- after catalyst

Particles selected at 16, 25 and 55 nm

are highly volatile particles

14

TEM images

size 15- 30 nm

HRTEM showed the internal structure of soot like particles are not graphitized

the size in agreement with the SMPS measurement

Calcium rich particles

Cryo microscopy investigation

Soot like particles

100 nm

100 nm

100 nm

Volatile particles

Lubrication oil related particles

15

HRTEM images of particles from 2- stroke scooter and Diesel passenger cars

stacked graphitic layers of the soot primary particles

2-stroke particle showing amorphous microstructures

10 nm

10 nm

Diesel soot

100 nm

10 nm

2- stroke particle

100 nm

16

EDX- Spectra

the presence Ca and S in the spectra is mostprobably from lub oil

the Cu signal is from the carbon coated copper TEM-grids

The EDX spectra of these group of particles shows Carbon, Oxygen, Sulphur and Calcium

17

Conclusion• Particles emitted from 2-stroke scooters were highly volatile.

• The relative volume loss of the exhaust particles upstream of the catalyst is higher than their downstream counterparts. This is, most likely, due to theremoval of highly volatile particles by the catalytic converter

No solid core was detected within the size range of the SMPS

• No significant difference could be identified between particles sampled from the two different scooters (TSDI, carburetor) .

• Volatile particles observed under cryo-electron microscopy are in agreement with theSMPS measurement.

• The microstructure of the soot like particles seem to be less graphitized than diesel engine soot particles.

• The presence of Ca and S in some particles gives clear indication on the contributionof lubrication oil.

18

Acknowledgment

• Silke Weimer (Empa, PSI)

• Claudio Rüdy (Empa)

• Marco Cantoni (EPFL)

19

Thank you for your attention