Embed Size (px)
Citation preview
Page 1 of 6
2015-26-0098
“Application of a LS Metal Catalyst Substrate for BS IV Two and Three Wheelers”
Jayat Francois 1, Seifert Sven 1, Babu KVR 2, Waje Shrivaj 2 1Continental Emitec GmbH,
2Emitec Emission Control Technologies India Pvt. Ltd. - India
Copyright © 2014 SAE International
Abstract
Affordable, efficient and durable catalytic converters for the two and three wheeler industry in developing countries are required to reduce vehicle emissions and to maintain them at a low level; and therefore to participate in a cleaner and healthier environment. The LS-DesignTM (Longitudinal Structure) metallic substrates with LS foils have been proved to be capable of improving conversion behavior, even with smaller catalyst size. Specially this developed foil structure, which transforms a laminar exhaust gas flow into a turbulent one, significantly improves exhaust gas mixing behaviour in the catalyst.
In this special period of time where BS4 applications will start appearing in the Indian market in the near future, this publication will deal with the experimental results achieved with different metallic substrate foil structures on one leading “state of the art” BS3 four stroke motorcycle technology, developed for the Indian market. The impact of turbulent substrate LS-DesignTM foil structures compared to standard and other TS-DesignTM (Transversal Structure) structures tested under WMTC driving cycle on roller bench in fresh state are discussed in depth. Emissions results are showing that substrate with LS-DesignTM perform better than the other and help to fulfil the proposed BS IV emission legislation.
Introduction
The International Council on clean Transportation (ICCT) published in 2013 a document with title “ Overview of India’s Vehicle Emissions Control Program” [1]. This document reports on the projected total NOx emissions in the absence of further emission reduction policy from the year 2010. The contributions of the 2 and 3 wheelers to NOx and PM emissions would grow slowly but constantly, proportionally to the increase of the 2 / 3 wheeler vehicle population. In the same document, recommendations are provided to reduce further emissions by applying more severe emission limit norm BS VI from 2022 and extending the durability requirement from 30,000 km to 50,000 km and as including in use compliance control.
In order to prepare the future affordable, efficient and durable catalytic converters for the two and three wheeler industry, Emitec started a comprehensive testing program with a state of the art BS III motorcycle. The program consists of testing the state of the art of Metallic substrates with structured foils with various catalyst sizes and positions (original or close coupled).
This publication deals with the first experimental results achieved with different metallic substrate foil structures : TS-DesignTM (Transversal Structure) structures and LS-DesignTM foil structures compared to standard foils. The aim of this preliminary study is to study the influence of the substrate foil structure on the emission reduction performance, keeping constant the basis BS III catalyst solution volume and cell density. Experimental results achieved over the new WMTC driving cycle on roller bench with fresh catalyst are discussed.
Metal Turbulent Structured Catalysts
It is a well known fact that catalyst effectiveness in warmed-up condition is influenced by substrate properties, i.e. by increasing the specific surface (the Geometric Surface Area: GSA) and improving contact between gas and wall, regardless of the type of catalytic reaction which takes place. This is characterized by the mass transfer coefficient β that describes the transport by diffusion of the pollutants from the core flow where their concentration is high to the catalytically active wall where their concentration is low. Flow conditions in Standard catalysts (Std) with straight and smooth channels are laminar after a first and short inlet section of the catalytic channel where the flow is not fully developed. Under laminar flow conditions the catalytic process is determined by a low mass transfer coefficient β, whose value could be five times lower than in the channel inlet section [2]. Beside the improvement of the mass transfer by mean of channel or cell size reduction, i.e. increasing the cell density for a given catalyst section, an innovative solution has been the development of “turbulent” metal substrates, whose foil structures introduced channel flow perturbations and therefore enhanced the mass transfer [2]. Of particular interest for the paper subject are the metal substrates with Transversal foil Structures (TS-Design™) and Longitudinal foil Structures (LS-Design™)
Page 2 of 6
TRANSVERSAL FOIL STRUCTURE (TS-Design™) Substrates
The initial development on TS substrates was carried out in 1994 when EMITEC developed the first generation of turbulent catalysts [3]. The corrugated foils, embossed with secondary micro- corrugations (Figure 1) are arranged transverse to the direction of flow, i.e. at 90 degree to the flow. These counter corrugations in unstructured channels lead to radial flow components which improve the mass transfer of the pollutant from the core of the channel nearer to the channel walls. Hence the conversion efficiency in the catalyst is improved.
Figure 1. TS structure design with flow details
TS substrate entered commercial production and is widely used in mass-produced components for automotive applications. More particularly TS substrates are already used on Indian series motorcycles. The benefits of the TS substrate can be summarized as:
• Improve the conversion efficiency for given catalyst dimensions.
• Reduce the cell density and therefore the back
pressure of the system while remaining at the same emission performance as catalysts with standard substrate.
LONGITUDINAL FOIL STRUCTURE (LS-Design™) Substrates
The substrate with longitudinal foil structure, applied in mass production [4], is characterized by LS-Counter corrugations (Figure 2) built in the corrugated foil during the manufacturing process. The LS-Counter corrugations is formed by pushing a fraction of the corrugated foil into the center of the channel, resulting in a local subdivision of the channel into two parts, aiming to recreate the “inlet length like” turbulent flow conditions, but also to bring the catalytically active wall to the center of the flow where pollutant concentrations are higher. Therefore, and especially at low exhaust pollutant concentrations, the diffusion process is no longer limiting the mass transfer, which improves the total catalytic efficiency.
Figure 2. LS-Design™ substrate structure
LS-Design™ structured substrates had previously been presented in the year 1990 [5,6] but no coating technologies for them were available at this time. Since the year 2002 it has been possible to coat them and they are since 2008 mass-produced for automotive Diesel or Gasoline applications.
Experimental Setup
TEST Vehicle
The test motorcycle is described in Table 1.
Table 1. Technical data of test vehicle
Test Vehicle
Engine Displacement 180 cm³
Exhaust Gas After Treatment Three Way Catalyst
Transmission 5 gears manual
Vehicle Kerb Weight [kg] 145
Maximum Speed (measured on roll bench)
[km/h]
112
Homologation BHARAT III
WMTC Class Sub-class 2.1
Test setup
The original exhaust muffler has been modified in order to be able to change catalysts in the exhaust pipe several times and at the same time assure complete tightness of the exhaust system, while preserving its layout. In addition, four temperature sensors: three at pre-catalyst positions 50 mm, 190 mm and 450 mm after engine out (this one is also 20 mm upstream the catalyst) and one at 20 mm post-catalyst position were inserted into the exhaust system (Figure 3). For emission measurements two gas sample extractions are carried out upstream and downstream the catalyst for second by second modal concentration measurements. Unfortunately due to the low exhaust gas quantity emitted by the motorcycle, it is impossible with the available measurement equipment to
Page 3 of 6
derive the right modal emission quantity in g/s. Bag emission measurements complete this setup.
Figure 3. Scheme of the exhaust system setup on tested vehicle and picture of the set up for a quick exchange of the catalyst.
WMTC Driving cycle
As the maximum speed obtained on the roller bench for the test vehicle was 112 kmph, emission measurements are carried out over the new World-wide Motorcycle Test Cycle (WMTC) for Indian Sub-Class 2.1 vehicles: Driving cycle part one with reduced vehicle speed cold and subsequent Driving cycle part one with reduced vehicle speed warm. Emissions of parts one cold and warm are weighted 50% each for the final emission result.
The vehicle coefficients applied to the roll test bench are this motorcycle: F0 = 19.4 N, F1 = 0 N/(km/h), F2 = 0.0223 N/(km/h)² and a vehicle inertia of 220 kg.
Test fuel is standard commercial Gasoline 98 ROZ 5 ppm S.
Tested Catalyst matrix
All catalysts tested in this work have a diameter of 40 mm and a PGM loading of 14 g/ft³. Other characteristics of the catalysts presented in this paper are listed in Table 2. All catalysts have been preconditioned during 4 WMTC cycles before emission measurements.
Table 2. Matrix of tested fresh catalysts
Catalyst numbers
# Substrate type
Cat. length [mm]
Foil thickness
(µm) Coating and
PGM Loading
#1 Std 50.8 110 BS III Series
#2 TS Design™ 50.8 110 BS III Series
#3 LS Design™ 50.8 65 BS III Series
Vehicle Emission Results
Exhaust gas temperatures
Catalyst efficiency is depending on the exhaust gas temperatures at catalyst inlet. The figure 4 shows the exhaust gas temperatures along the exhaust pipe from the engine out up to the position upstream the catalyst. The temperatures in front of the catalyst reach very quickly values above 300°C, what is good the catalyst light off, and then vary between 350°C and 500°C after 200 seconds of testing.
Figure 4. WMTC Exhaust gas temperatures at different location of the exhaust pipe for the Sub-Class 2.1 180 CC motorcycle. Measured during the emission test with Catalyst #2.
Result with fresh catalysts
Bag results
Emissions were collected with two bags: The first one for the first cold WMTC part one with reduced speed and the second bag for the subsequent warm WMTC part one. Doing so helps to distinguish between the cold start phase and the warm phase. The results for HC, CO, NOx and HC+NOx are shown in Figure 5, 6, 7 and 8 and compared to the BS IV emissions limits, applying Evaporative Emission Norms for 2-Wheelers (here for the option of vehicle with evaporative emission norm of 6 g/test) as proposed by the Indian Central Government as Central Motor Vehicles (Amendment) Rules, 2014.
0
100
200
300
400
500
600
700
800
900
0 200 400 600 800 1000 1200
Te
mp
era
ture
s (°
C)
WMTC time (s)
50 mm
190 mm
450 mm (pre - catalyst)
SetSpeed.SysComp.Dyno
Page 4 of 6
Figure 5. WMTC HC bag emissions of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Figure 6. WMTC CO bag emissions of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Figure 7. WMTC NOx bag emissions of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Figure 8. WMTC HC+NOx bag emissions of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Figure 7 is showing that the NOx emissions of this vehicle are not a problem. NOx emissions are almost 50% below proposed BS IV NOx emission limit whatever the catalyst. Figure 8 is showing that HC + NOx emissions are below proposed BS IV emission limit with all catalysts. Figure 5 is showing that TS-Design™ structured substrates is performing slightly better than the Standard substrate with non-structured foils but less than the LS-Design™ structured substrates to convert HC. Figure 6 is showing that BS IV CO emission are fulfilled with the LS structured catalyst only: LS-Design™ structured substrate helps to reduce the CO emissions by 0.4 g/km in comparison to the Standard substrate, while the CO emission reduction gain with TS-Design™ structured substrate compared to Standard catalyst is 0.2 g/km only. All Figures are showing a better behavior of LS-Design™ structured substrate in cold start as well as in warm operation.
Second by second modal pollutant concentration results
Second by second modal concentrations for HC, CO and NOx and their conversion rates with the three catalysts are shown in Figure 9, 10 and 11.
Figures 9 and 10 show and confirm for HC and CO emission reduction the benefit of the structured foil substrates, especially the advantage gained with of LS-Design™ structured substrate at cold start and during warm operation.
Figure 11 confirms that NOx emission reduction is slightly better with structured substrates but the measurements could not allow to clearly confirm the benefit of the of LS-Design™ structured substrate for NOx reduction in the condition of the test, with an underbody catalyst position.
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0,45
Cold WMTC
part one
Warm WMTC
part one
Total WMTC
cycle
HC
em
isis
on
s (g
/km
)
Catalyst #1, Std
Catalyst # 2, TS
Catalyst #3, LS
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
Cold WMTC
part one
Warm WMTC
part one
Total WMTC
cycle
CO
em
isis
on
s (g
/km
)
Catalyst #1, Std
Catalyst # 2, TS
Catalyst #3, LS
Sub Class 2.1 BS
IV limit with DF
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
Cold WMTC
part one
Warm WMTC
part one
Total WMTC
cycle
NO
x e
mis
iso
ns
(g/k
m)
Catalyst #1, Std
Catalyst # 2, TS
Catalyst #3, LS
Sub Class 2.1 BS
IV limit with DF
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
Cold WMTC
part one
Warm
WMTC part
one
Total WMTC
cycle
HC
+N
Ox
em
isis
on
s (g
/km
)
Catalyst #1, Std
Catalyst # 2, TS
Catalyst #3, LS
Sub Class 2.1 BS
IV limit with DF
Page 5 of 6
Figure 9. Modal engine out and tail pipe HC concentrations and derived HC conversion rates versus vehicle speed over WMTC cold part one with reduced speed of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Figure 10. Modal engine out and tail pipe CO concentrations and derived CO conversion rates versus vehicle speed over WMTC cold part one with reduced speed of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
0
10000
20000
30000
40000
50000
60000
70000
80000
0 200 400 600
En
gin
e O
ut
HC
co
nce
ntr
ati
on
s (p
pm
)Catalyst # 1, STD
Catalyst #2,TS
Catalyst #3, LS
0
5000
10000
15000
20000
25000
0 200 400 600
Ta
il p
ipe
HC
co
nce
ntr
ati
on
s (p
pm
)
40
50
60
70
80
90
100
0 200 400 600
HC
co
nv
ers
ion
s ra
te (
%)
0
10
20
30
40
50
60
0 200 400 600
Ve
hic
le s
pe
ed
(k
m/h
)
WMTC time (s)
0
1
2
3
4
5
6
7
0 200 400 600
En
gin
e O
ut
CO
co
nce
ntr
ati
on
s (%
)
Catalyst # 1, STD
Catalyst #2,TS
Catalyst #3, LS
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
0 200 400 600
Ta
il p
ipe
CO
co
nce
ntr
ati
on
s (p
pm
)
0
20
40
60
80
100
0 200 400 600
CO
co
nv
ers
ion
s ra
te (
%)
0
10
20
30
40
50
60
0 200 400 600
Ve
hic
le s
pe
ed
(k
m/h
)
WMTC time (s)
Page 6 of 6
Figure 11. Modal engine out and tail pipe NOx concentrations and derived NOx conversion rates versus vehicle speed over WMTC cold part one with reduced speed of the Sub-Class 2.1 180 CC motorcycle for the different catalysts.
Summary/Conclusions
This paper is reporting preliminary results gained within a comprehensive testing program with a state of the art BS III motorcycle, aiming to develop catalyst solutions for BS IV legislation and beyond. Preliminary emissions results gained in series catalyst position (underbody) over the new WMTC driving cycle with structured foil catalysts are showing that LS-Design™ structured substrate performs better than standard substrate and TS-Design™ structured substrate and allows the catalyst to achieve BS IV emission legislation by keeping the same cell density, washcoat, PGM loading and catalyst volume as the BS III basis catalyst solution.
References
1. “Overview of India’s Vehicle Emissions Control Program, Past Successes and Future Prospects”, Gaurav Bansal and Anup Bandivadekar. ICCT 2013
2. Brueck R., Hirth P., Maus W., Deutschmann O., Mladenov N., “Fundamentals of Laminar and Turbulent Catalysis; Turbulent beats Laminar”, 27. Internationales Wiener Motorensymposium, 2006
3. Held, Rohlfs: VW AG; W. Maus, Swars, R. Brueck, F.W. Kaiser: Emitec GmbH" Improved Cell Design for increased Catalytic Conversion Efficiency”, SAE 940932
4. Nagel T., Kruse C. “Einsatz hocheffektiver, turbulenter Metallträger unter den begrenzten Bauraumverhältnissen heutiger EU V Großserien-Diesel PKW“; 4. Emission Control, Dresden, Mai 29-30, 2008
5. Behr GmbH; “Schlitze für mehr Leistung – Katalysatorträger METALIT-S“; Automobil-Produktion, 1989, 3, Seite 166
6. R. Brück, J. Diringer, U. Martin, W. Maus; Emitec GmbH: ”Flow Improved Efficiency by New Cell Structures in Metallic Substrates”; SAE 950788
Contact Information
If any question please contact Dr. Francois Jayat at following e-mail address [email protected].
Acknowledgments
The Authors gratefully thank the firm Automotive Catalyst
Umicore AG & Co. KG for the supply of the catalyst coating used in this development work.
0
500
1000
1500
2000
2500
3000
0 200 400 600
En
gin
e O
ut
NO
x c
on
cen
tra
tio
ns
(pp
m)
Catalyst # 1, STD
Catalyst #2,TS
Catalyst #3, LS
0
500
1000
1500
2000
2500
0 200 400 600
Ta
il p
ipe
NO
x c
on
cen
tra
tio
ns
(pp
m)
0
20
40
60
80
100
0 200 400 600
NO
x c
on
ve
rsio
n r
ate
(%
)
0
10
20
30
40
50
60
0 200 400 600
Ve
hic
le s
pe
ed
(k
m/h
)
WMTC time (s)
