An Innovative AfterTreatment System

1
An Innovative After-Treatment System for Diesel
PM Removal Shuiliang Yao, Shin Yamamoto, Satoshi
Kodama, Chieko Mine, Chihiro Fushimi, Yuichi
Fujioka Research Institute of Innovative
Technology for the Earth, Kyoto 619-0292,
Japan Kazuya Naito, Kazuhiko Madokoro, Yoon-Ho
Kim Daihatsu Motor Co., Ltd., Siga 520-2593,
Japan Seiichi Soma, Toru Nakajima, Gen
Sugiyama Japan Automobile Research Institute
(JARI), Tsukuba 305-0822, Japan
2

• Background 1.1 Why diesel

24.3 ?
CO2 emission (10-15 mode) (g-CO2/km)
53.6 ?
27.3 ?
Total CO2 emission from Well to Wheel.
Data from a report of JHFC, 2006.
?
Diesel vehicles contribute reduction of CO2 green
house gas.
3
1. Background 1.2 PM formation mechanism
Refhttp//www.abo.fi/instut/pcg/
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1. Background 1.3 PM journey in a human body
?
An excess risk of lung cancer.
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1. Background 1.4 PM properties
SEM photo of diesel PM
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1. Background 1.5 PM thermal combustion
Heat flow
PM weight
PM weight () and heat flow (mV)
CO and CO2 mass signals
CO
CO2
Temperature (oC)
PM thermal combustion in oxygen-containing
atmosphere. Experimental condition O2
concentration 10 (He balance), scanning
temperature rate 10 oC/min.
?
570 oC is required for PM thermal combustion.
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1. Background 1.6 Emission standards
0.10
1997 NOx 0.4 PM 0.08
Japan
2002 NOx 0.28 PM 0.052
0.08
1997 NOx 0.78 PM 0.062
USA
EU
0.06
2004 NOx 0.19 PM 0.037
PM (g/km)
0.04
2000(Euro 3) NOx 0.50 PM 0.05
2009(EURO 5) NOx 0.18 PM 0.005
2005(EURO 4) NOx 0.25 PM 0.025
0.02
2009 NOx 0.05 PM 0.005
2005 NOx 0.14 PM 0.013
0.00
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
2014(EURO 6) NOx 0.08 PM 0.005
NOx (g/km)
Emission standards for light-duty vehicles.
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1. Background 1.7 PM removal methods
Gas in
Gas out
Gas before filtration
Trapped PM
SiC membrane
Gas after filtration
Photo of DPF samples
Mechanism of PM removal using a diesel
particulate filter (DPF).
1) Honeycomb structure. 2) Multi-membranes with
10s mm pores. 3) Regeneration by heating at gt 600
oC.
?
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1. Background 1.7 PM removal methods
Fuel penalty due to the use of DPF.
Regeneration gap (oC)regeneration temperature
(600)-exhaust temperature
RefK. Ohno. Doctoral thesis of Waseda
University, 2006.
?
Fuel penalty 6-11 in 150-380 oC (typical for
light-duty vehicles).
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1. Background 1.8 PM removal methods Our
studies
12VDC power
Pulse power supply
High-voltage output
Diesel engine (2L)
Earth
NOx reduction using EGR
Plasma reactor (DBD reactor)
A non-thermal plasma PM removal system.
Targets for light-duty vehicles tested with JC08
mode
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1. Background 1.9 PM Plasma PM removal mechanism
UV, O, OH, O3, NO2 contributed sp2 ratio
decreases sp3 ratio increases
sp2 bonding
O3, NO2 contributed sp2 ratio increases sp3 ratio
decreases
Graphene with sp2 terminals
Graphene with sp3 terminals
Mechanism of PM oxidation/combustion by plasma
discharges.
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1. Background 1.10 Object of this study
To characterize the DBD reactor using a chassis
dynamometer system under JC08 mode.
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2. Experimental 2.1 Chassis dynamometer system
SOF/SOOT emission Particle concentration (EEPS,
CPC) NOx concentration HC concentration
Air
To CVS
Full flow dilution tunnel
DOC
Diesel Engine
Tail pipe
Muffler
Dynamo meter
DBD reactor
Experimental setup for emission measurements
using a chassis dynamometer.
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2. Experimental 2.2 Discharge system
Silicone insulator
Alumina plate
Alumina spacer
Al plate
CTa
V-P
High voltage
Alumina tube
Exhaust gas
Pulse power supply
12V dc Power
Reactor frame
CTc
Oscilloscope
Earth
Assembly of the DBD reactor and discharge system.
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2. Experimental 2.3 DBD reactor
Basic structure of a DBD reactor.
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2. Experimental 2.3 DBD reactor
A
B
Side views of DBD reactor without (A) or with (B)
discharges.
?
1) 21 pairs of electrodes. 2) Volume 2.6 L.
Basic structure of DBD reactor.
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2. Experimental 2.4 Definitions
Energy injection in Watts
PM removal by PM weight emission measurement
PM removal by PM number measurement using EEPS or
CPC
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2. Experimental 2.5 Conditions
Test mode JC08, hot or cold start Diesel
fuel JIS2 Discharge conditions Pulse
frequency 110220 Hz Peak voltage 08
kV Experiment cycles JC08Cold start x 2
cycles JC08Hot start x 7 cycles
Speed profile of JC08 mode.
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3. Results discussion 3.1 Typical discharge
waveforms
?
Pulse voltage rise time 15 ms, pulse width 18
ms.
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3. Results discussion 3.2 Energy injection
?
Energy injection is at a level of 0.85 J/pulse
within 56 ms.
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3. Results discussion 3.3 Exhaust temperature
pressure loss
?
1) Pressure loss ? 10 kPa. 2) T 150160 oC.
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3. Results discussion 3.4 NOx emission
NOx emission (g/km)
Energy injection (W)
?
NOx emission does not increase obviously.
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3. Results discussion 3.5 PM number
concentration-EEPS
PM concentration (/cm3)
Without discharges
PM diameter (nm)
With discharges (93W)
PM diameter (nm)
Elapsed time (one JC08 cycle)
?
PM number concentration decreased due to plasma
discharges.
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3. Results discussion 3.5 PM number
concentration-EEPS
Peak PM concentration used for removal
calculation at various diameters
PM concentration (x106 /cm3)
Speed (km/h)
Elapsed time (min)
?
PM number concentration decreased due to plasma
discharges.
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3. Results discussion 3.6 PM number
removal-EEPS
data from peak PM concentration
PM concentration (x106 /cm3)
PM removal ()
PM diameter (nm)
?
1) PM number removal is 80 at a diameter gt35
nm. 2) 15 nm particle number increased.
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3. Results discussion 3.7 PM number removal-CPC
PM concentration (/test)
PM removal ()
Energy injection (W)
?
PM number removal is 76 at 93 W, 90 at 400W.
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3. Results discussion 3.6 PM weight removal
Post new long-term emission standard0.005g/km
PM removal ()
PM emission (g/km)
PM
SOOT
SOF
Energy injection (W)
?
1) Clear the post new long-term emission standard
at ?93 W. 2) SOOT can be removed effectively. 3)
Plasma discharges have no effect on SOF removal.
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3. Results discussion 3.7 PM mass balance
Table 1 PM mass balance in the DBD reactor
Calculated from mileage Due to PM deposition
in the DBD reactor estimated from results under a
certain engine condition.
?
PM removed 3.285g by deposition 1.25g (38)
by oxidation 2.035g (62)
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3. Results discussion 3.8 Fuel penalty
DPF611
Reactor structure improved
Current reactor
3.4 at 93W
6.2 at 93W
Total
Total
Fuel penalty decrease ratio ()
Fuel penalty decrease ratio ()
Due to energy injection
Due to energy injection
Due to pressure loss
Due to pressure loss
Energy injection (W)
Energy injection (W)
Estimation of fuel penalty due to pressure loss
and electric power consumption.
?

• 6.2 using current reactor.
• 3.4 is realizable using improved reactor.
• 2) The cost of the system is a problem.

Calculation on Engine efficiency 40 Power
(12V) efficiency 80 Pulse power efficiency 80
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4. Conclusion

• PM can be removed by plasma discharges. The
  results are summarized as follows
• At 93 W, PM emission is 0.005 g/km,
• satisfying Japanese post new long-term
  emission standard.
• 2) PM is removed by oxidation (62) and by
  deposition (38).
• 3) Pressure loss on the reactor and energy
  injection create fuel penalty.
• At 93 W, total fuel penalty is 6.2 using the
  current reactor
• 
  can be reduced to 3.4 if using an improved
  reactor.
• 4) The cost of the system is a problem.

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Acknowledgments This work was supported by the
New Energy Industrial Technology Development
Organization (NEDO) under a government fund from
the Ministry of Economy, Trade and Industry
(METI), Japan. Special appreciation would be
extended to Prof. Y. Nihei at Tokyo University
of Science, Prof. H. Fujimoto at Doshisha
University, Prof. Y. Hori at the University of
Tokyo and Prof. Y. Teraoka at Kyushu
University.