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1
PM REMOVAL SYSTEM FOR
DIESEL PASSENGER VEHICLE
USING NON-THERMAL PLASMA
Kazuhiko Madokoro, Y. H. Kim, K. Naito, T. Ogawa
H. Fujikawa, K. Hasegawa, H. Tanaka
Daihatsu Motor Co., Ltd., Japan
S. Yamamoto, S. Kodama, C. Mine
S. Yao, Y. Fujioka
Research Institute of Innovative Technology for the Earth (RITE), Japan
S. Soma, T. Nakajima, G. Sugiyama
Japan Automobile Research Institute (JARI), Japan
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Outline
 Introduction
- Diesel emission regulations
- What is plasma?
- Advantages and problems of plasma technology
 Experimental
 Results
 Conclusion
Diesel emission regulations (Passenger vehicles)
EU
11, 10･15 , JC08 mode
0.10
0.080
0.
08
0.06
0.052
0.04
1997
0.08
0.06
2002
Our target
0.02
0.013
2005
0.005 2009
0.00
0.08 0.14 0.28 0.4
0.0
0.2
0.4
US
NEDC mode
0.10
0.6
Vehicle speed [ km/h ]
PM [g/km]
Japan
80
0.05
20
Japanese JC08 mode
0.062 1994 Tier1
0.06
2000 Euro3
NOx [g/km]
0.04
0.037
2005 Euro4
0.02
0 0.005
0.00
0
0.8
0.0
FTP mode
0.10
0.08
60 0.04
40 0.025
3
2004～06 Tier2 (Bin#9)
0.02
2009 Euro5
0.18
0.5
200 0.25 400
0.2
0.4
0.6
0.006 2007 Tier2 (Bin#5)
0.00
600
800 0.19 1000
1200
0.044
0.78
0.8
0.0
0.2
0.4
0.6
0.8
Elapsed time [ s ]
NOx [g/km]
NOx [g/km]
 Stricter regulations for emission control are being set all over the world.
 The Japanese post new long-term emission regulation comes into force.
 A newly established emission test mode (JC08) has also been introduced.
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What is Plasma ?
Lightning
 Plasma is called a "Fourth State of Matter".
Aurora
 Plasma is a partially ionized gas mixture
and contains electrons, ions, neutral atoms,
molecules, reactive free radicals and photons.
Three states of matter
Solid
Liquid
Melting
Fourth state
Gas
Evaporation
Electrolytic
dissociation
Plasma
Application of the plasma to diesel exhaust gases
It is generally known that highly reactive species such as
O3, O, NO2 and OH are generated in the plasma of diesel exhaust gases.
These reactive species can lead to oxidation of PM.
Exhaust gases
O2, NO, H2O
PM
etc
Discharge plasma
O3, O, NO2
etc
CO2
CO
Advantages and problems of plasma technology
 Advantages




Successive PM removal irrespective of ambient temperature
No using Platinum-Group Metals
Easily controllable of PM removal rates by power management
Simple reactor configuration for low pressure drop
 Hurdles to overcome before practical use





Designing of a novel plasma reactor
Reduction of energy consumption
Improvement of power supply system & power delivery for plasma generation
Elucidation of PM removal mechanism
Durability of the system
Target
PM emission : below 0.005 g/km
Pressure drop: below 5 kPa
Fuel penalty : below 2.5% (at Japanese JC08 mode)
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Outline
 Introduction
 Experimental
- Discharge system
- Emission measurement system
- Modal emission test
 Results
 Conclusion
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Discharge system
High voltage probe
Oscilloscope
Current Transformer
Pulse Power
Supply
Discharge
DC Power
Supply
AC 100V
Plasma Reactor
Ref: S. Yao (RITE), AIChE J., Vol. 53, 1891-1897 (2007)
Dielectric barrier discharge reactor
driven by high-voltage pulses
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Non-thermal plasma reactor
Dielectric plate
Electrode
High
voltage
Earth
Gas flow
Temporary trap
PM
(c)
Gas flow
Oxidation
(Combustion)
Electrode
CO2
(CO)
Dielectric (General flat plate of alumina)
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Emission measurement system
PM mass emission
Chassis dynamometer
Soluble organic fraction (SOF)
Insoluble organic fraction (ISF)
Soxhlet
extraction
Sampling
bag
Dilution Air
PM filter
CFV-CVS
Full flow dilution tunnel
Dilutor
Vehicle data
Engine
1.5 L 4-cycle diesel engine
Original Emission level
Euro4
Original aftertreatment
Diesel oxidation catalyst (DOC)
Engine Exhaust
Particulate Sizer
(EEPS-3090)
Particle number
concentration
Vehicle emission measurement was carried out at JARI.
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Modal emission test
 Japanese JC08 mode (hot and cold start)
Warm-up period
Vehicle speed [ km/h ]
120
Hot mode start
Cold mode start (without warm-up)
Emission measurement start
100
80
60
40
20
0
-200
0
200
400
600
800
1000
1200
Elapsed time [ s ]
 Evaluated aftertreatment system
Without aftertreatment
Engine
Engine
DOC
Engine
DOC
Original aftertreatment (DOC)
Plasma
reactor
Original & Plasma reactor
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Outline
 Introduction
 Experimental
 Results
- Inlet gas temperature of the plasma reactor
- PM mass emission
- Particle size distributions
- Appearance of alumina plates
- Pressure drop of plasma reactor
 Conclusion
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Vehicle speed [ km/h ]
Inlet gas temperature of the plasma reactor
100
Target vehicle speed
80
Real vehicle speed
60
40
20
0
Gas temperature [ °C ]
250
200
150
Gas temperature
100
Cold start mode
Hot start mode
Maximum : 222.0 ºC
Maximum : 222.6 ºC
Average : 147.0 ºC
Average : 170.4 ºC
50
hot
cold
0
0
200
400
600
800
1000
Elapsed time [ s ]
 Inlet gas of the plasma reactor was under low temperature during mode.
1200
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PM mass emission
Cold
* Combine emission = Cold mode emission × 0.25 + Hot mode emission ×
0.75
Hot
Combine*
0.06
Emission [ g/km ]
0.05
0.04
w/o aftertreatment
Original
Original & Plasma
w/o aftertreatment
Original
Original & Plasma
51%
62%
0.03
59%
15%
0.02
77%
86%
26%
81%
79%
w/o aftertreatment
Original
Original & Plasma
91%
(0.0048 g/km)
93%
23%
91%
79%
84
%
86%
0.01
54%
35%
23%
0.00
PM
SOF
ISF
PM
SOF
ISF
PM
SOF
ISF
Japanese new regulation
(JP 2009)
 The plasma reactor showed almost same removal capability in both modes.
 The oxidative ability of plasma showed elective affinity for soot.
 PM emission of our plasma reactor achieved JP2009 regulation
(combine emission value 0.0048 g/km).
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Particle size distributions
Cold
Hot
Particle concentration [ #/cm 3 ]
Good
1.E+07
9.E+06
8.E+06
w/o aftertreatment
w/o aftertreatment
Original
Original
Original & Plasma
Original & Plasma
7.E+06
6.E+06
5.E+06
81.3%
4.E+06
87.6%
3.E+06
2.E+06
1.E+06
0.E+00
1
10
100
Particle size [ nm ]
1000 1
10
100
Particle size [ nm ]
 Particle concentrations after the plasma reactor were clearly reduced.
 Non-thermal plasma could also remove nano-particles.
1000
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Appearance of alumina plates
With plasma
Exhaust gas flow
Without plasma
Temporary
trap
Oxidation
(Combustion)
Area of electrode
After about 300 km mode driving
 PM was clearly removed on the alumina plate with plasma.
 PM adsorption was observed less at downstream side.
It is suggested that reactive species which came from the upstream side
contributed to oxidize PM at the downstream side.
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Pressure drop [ kPa ]
5
100
Hot
Cold
Vehicle speed
4
3
80
60
2
40
1
20
0
200
Maximum pressure drop [ kPa ] .
0
400
600
Elapsed time [ s ]
800
1000
Vehicle speed [ km/h ] .
Pressure drop of the plasma reactor
0
1200
8
7
6
5
4
3
2
1
0
0
5
10
Number of mode test [ n ]
15
 The plasma reactor maintained lower pressure drop during consecutive mode tests.
 It is suggested that PM was successively removed by the plasma reactor.
Conclusion
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1. PM emission could satisfy JP2009 emission regulation of 0.005 g/km
by installing the plasma reactor after the original DOC.
The plasma reactor showed successive high removal rate for ISF
which is not easily oxidized with catalytic reactions compared with SOF.
2. The plasma reactor could remove PM under low temperature.
Such a removal ability is a great advantage compared with a catalyst
or a DPF which requires active regeneration.
3. The plasma reactor showed low pressure drop during JC08 mode.
Such low pressure drop was achieved due to the structural characteristic
of plasma reactor.
This plasma system is expected to be one of the
promising technologies for diesel emission control.
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Acknowledgement
This work is supported by
Japanese government through NEDO.
New Energy Industrial Technology Development Organization
Comprehensive Technological Development of Innovative, Next-Generation,
Low-Pollution Vehicles R&D of Innovative After-Treatment Systems
We would like to thank
Professor
Professor
Professor
Professor
Yoshimasa Nihei
Hajime Fujimoto
Yoichi Hori
Yasutake Teraoka
[Tokyo University of Science]
[Doshisha University]
[The University of Tokyo]
[Kyushu University]
Thank you for your attention !
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END
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NOx emission
0.8
Hot
w/o aftertreatment
DOC
w/o aftertreatment
DOC
DOC & Plasma
0.6
DOC & Plasma
0.5
0.4
0.3
0.2
0.1
0.0
NOx
CO
0.8
0.7
Emission [ g/km ]
Emission [g/km]
0.7
Cold
NMHC
NOx
Combine
w/o aftertreatment
DOC
DOC & Plasma
0.6
0.5
0.4
0.3
0.2
0.1
0.0
NOx
CO
NMHC
CO
NMHC
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Discharge system
High voltage probe
Oscilloscope
Current Transformer
Pulse Power
Supply
DC Power
Supply
AC 100V
Plasma Reactor
DC powersupply
(DC voltage : 0-600V)
Pulse power supply
driven by DC power supply
(Pulse peak voltage : ~ 10kV)
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Plasma reactor and new electrode
New electrode
Glass wool spacer
Alumina plate
(dielectric)
Gas flow
Gas flow
Discarge
PM
Gas flow
Ref: S. Yao (RITE), AIChE J., Vol. 53, 1891-1897 (2007)
Electrode
Electrode
Dielectric
(Mass-produced flat plate of general alumina)
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Thermal and Non-thermal plasma
Gas Temperature Rise [C]
106
105
ne ~ 1018cm-3
104
Arc
MW Torch
103
Pulsed
Corona(+)
Dielectric Barrier
Discharge
wire cylinder
rod barrier cylinder
ne ~ 1015cm-3
RF
Jet ne ~ 1012cm-3
102
Pulsed Corona & DBD
ne ~ 1012cm-3
101
0
5
10
Electron Temperature [eV]
15
20
MH Cho, postech, 8th APCPST, 2006
 Thermal plasma : All particles are in state of high temperatures.
Gas show high temperatures.
 Non-thermal plasma : Only electrons show high temperatures.
Gas remains in state of almost 'cold' (ambient temperature).
Our concept for reducing each emissions
NOx
reduction
2CD
NOx
reduction
Cooled EGR
DOC
CO, HC and SOF
reduction
Plasma
Reactor
NOx
catalyst
Soot and SOF
reduction
 NOx is reduced by control of engine combustion or NOx catalyst.
 CO, HC and SOF are reduced by the diesel oxidation catalyst.
 Soot and SOF are reduced by the plasma reactor.
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Equation for PM removal rates
PM removal rate
from emission w/o =
aftertreatment
ー
Emission w/ o
aftertreatment
Original or
Original & Plasma emission
× 100 (%)
Emission w/ o aftertreatment
PM removal rate
from original DOC =
emission
Original DOC
emission
ー
Original & Plasma
emission
× 100 (%)
Original DOC emission
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PM number emission (CPC)
8.E+13
Cold
Hot
7.E+13
6.E+13
5.E+13
4.E+13
3.E+13
2.E+13
1.E+13
0.E+00
w/o
DOC
9.E+13
PM number Emission [ #/km ]
PM number Emission [ #/km ]
9.E+13
8.E+13
DOC &
Plasma
w/o
Combine
7.E+13
6.E+13
5.E+13
4.E+13
3.E+13
2.E+13
1.E+13
0.E+00
w/o
DOC
DOC &
Plasma
DOC
DOC &
Plasma
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Japanese 10-15 mode and JC08 mode
Vehicle speed [ km/h ]
 Japanese 10-15 mode
80
60
40
20
0
0
200
400
800
1000
1200
800
1000
1200
Elapsed time [ s ]
 Japanese JC08 mode
Vehicle speed [ km/h ]
600
80
60
40
20
0
0
200
400
600
Elapsed time [ s ]
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V ehicle speed [ km /h ]
Gas temperature and pressure drop
100
T arget vehicle speed
R eal vehicle speed
80
60
40
20
Gas temperature
Gas temperature [ °C ]
0
250
 Cold start mode
Maximum : 222.0 ºC
Average : 147.0 ºC
 Hot start mode
Maximum : 222.6 ºC
Average : 170.4 ºC
200
150
100
hot
50
cold
Pressure drop [ kPa ]
0
5
Pressure drop
hot
4
cold
 Cold start mode
Maximum : 3.4 kPa
 Hot start mode
Maximum : 3.8 kPa
3
2
1
0
0
200
400
600
800
1000
1200
Elapsed time [ s ]
 The plasma reactor could remove PM effectively even under low temperatures.
 The plasma reactor showed lower pressure drop below 3.8 kPa during mode.
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PM mass emission (JP2009)
* Combine emission = JC08 Cold mode emission × 0.25 + 10-15 Hot mode emission × 0.75
Hot (10-15)
Cold (JC08)
Combine*
0.06
0.05
Emission [ g/km ]
w/o aftertreatment
Original
Original & Plasma
w/o aftertreatment
Original
Original & Plasma
w/o aftertreatment
Original
Original & Plasma
0.04
0.03
0.02
0.01
0.00
PM
SOF
ISF
PM
SOF
ISF
PM
SOF
ISF
Japanese new regulation
(JP 2009)
Combine emission value
0.0038 g/km
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V ehicle speed [ km /h ]
Total particle concentrations
100
T arget vehicle speed
R eal vehicle speed
80
60
40
20
Total concentration [ #/cm3 ]
0
3.5E+06
w/o aftertreatment
3.0E+06
Original
2.5E+06
Original + DBD (200W)
2.0E+06
1.5E+06
1.0E+06
5.0E+05
0.0E+00
0
200
400
600
Elapsed time [ s ]
800
1000
1200
Fluctuation of pressure drop during mode tests
Maximum pressure drop [ kPa ]
8
7
6
5
4
3
2
1
0
0
5
10
15
Number of mode test [ n ]
 Maximum pressure drop didn't increase during consecutive mode tests.
 It is suggested that PM was successively removed by the plasma reactor.
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