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SAE TECHNICAL
PAPER SERIES
SAE 1999-01-3338
JSAE 9938093
Best Available Technology for Emission
Reduction of Small 4S-SI-Engines
A. Mayer
J. Czerwinski
TTM
AFHB
M. Wyser
E. Stadler and U. Wolfensberger
BUWAL
FAT
U. Matter
P. Mattrel
ETHZ
EMPA
G. Hüthwohl and A. Schindler
HJS
Reprinted From: Proceedings of the 1999 SAE Small Engine Technology Conference
(P-348)
Small Engine Technology Conference & Exposition
Madison, Wisconsin
September 28-30, 1999
400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A.
Tel: (724) 776-4841 Fax: (724) 776-5760
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SAE 1999-01-3338 / JSAE 9938093
Best Available Technology for Emission Reduction
of Small 4S-SI-Engines
A. Mayer
TTM
J. Czerwinski
AFHB
M. Wyser
BUWAL
E. Stadler and U. Wolfensberger
FAT
U. Matter
ETHZ
P. Mattrel
EMPA
G. Hüthwohl and A. Schindler
HJS
1. ABSTRACT
ready in 1996. The results are marked in table 1 with
"Frey/EMPA" [11].
Small off-road 4-stroke SI-engines have extraordinarily
high pollutant emissions. These must be curtailed to
comply with the new Swiss clean air act LRV 98. The
Swiss environmental protection agency (BUWAL) investigated the state of the technology. The aim was a cleaner
agricultural walk behind mower with a 10kW 4-stroke SIengine. Two engine designs were compared: side-valve
and OHV.
Table 1.
A commercially available 3-way catalytic converter system substantially curtailed emissions: In the ISO 8178 G
test-cycle-average, HC was minimized to 8% and CO to
5% of raw emissions. At part load points, the residual
emission was < 1%. Simultaneously, fuel consumption
improved 10%. Using a special gasoline (Swiss standard
SN 181 163), the aromatic hydrocarbons were curtailed,
e.g. Benzene < 1%, and fuel consumption further
improved. Those results were confirmed in field tests.
The engine is approved for retrofitting. Disquieting are the
high emissions of ultrafine particulates: the catalytic converter only minimizes the volatile but not the solid particulates.
Exhaust Emissions from 4S-SI-Engines
g/kWh
CO
HC
(HC+NOx)
Swiss Offroad Inventory [1]
100 - 1200
7 - 55
UBA [10]
200 - 600
5 - 35
Briggs & Stratton OHV
384
11.5
CARB Certification 1996
20 - 450
1 - 12
CARB Limit
402
(13.4)
549
(12)
549
(9.4)
1995
CARB Limit 2000
2004
EPA-Limit 1997
610
(12.0)
EUROMOT-Proposal
Stage 1[13]
519
(13.4)
Frey/EMPA 96 [11]
5 - 40
0.5 - 2
ULEV für PKW
5
0.12
Table 1:
2. INTRODUCTION
The total emission contribution for CO and HC of these
small engines in Switzerland (Fig. 2) has already attained
a high proportion, in comparison to the emissions from
vehicular traffic. The main sources of pollution are the
agriculture and horticulture sectors.
Small equipment SI-engines have extremely high specific
exhaust gas emissions. Table 1 shows the range based
on the Swiss off-road inventory [1] and the newer UBAtests [10]. The table also shows the relatively modest
improvements obtained after California enacted the first
limits in 1996.
The relative proportion of these emittants is forecasted
[1] to substantially increase. Hence, the Swiss environmental protection agency (BUWAL) enacted in 1998 a
curtailment of these emissions along with the revised
Swiss clean air act [2].
Nevertheless, lawn-mower engines in California, too,
have emission factors that are 100times higher than
those of modern automobiles. This can be remedied as
shown in an earlier Swiss technology test performed all1
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The air intake is usually from above. The exhaust gases
are expelled behind towards the operator.
These manual machines are deployed in the Swiss hilly
country during the entire vegetation period to mow fresh
fodder. The farmer usually leaves the mower outside and
runs it twice daily during 10 - 30 minutes, early morning
and evening. This short duration of operation naturally
worsens the emission situation compared to loaboratory
results since the contribution of the cold start phase is
very high.
Two typical engines were investigated. These are widely
represented in the Swiss market.
Engine 1
Figure 1. Swiss inventory for the emissions of small
SI-engines [1]
Briggs & Stratton Vanguard (2 cyl. V) Modell 294446
Cylinder volume:
A typical application of such engines, in the power range
10 kW, is the agricultural single-axle mowers. These are
very popular in the constrained hilly Swiss landscape.
There are about 100,000 mowers deployed. Such "walkbehind" mowers directly expose the farmer to exhaust
gas emissions with limited dilution. Hence, it is an urgent
requirement, particularly for these applications, to quickly
find a retrofit solution that efficiently curtails the most
toxic components of the exhaust gas.
VH = 0.479 dm3
Compression ratio:
e = 8.25
Rated power:
9.2 kW
Rated RPM:
3600 RPM
OHV arrangement
Engine 2
Briggs & Stratton 11 HP (1 Cylinder) Modell 256426
Side valves
3. ENGINES, APPLICATIONS AND
DEPLOYMENT
This project focussed on the so-called yoke-mower
(Fig. 2). The exhaust gases from this agricultural
machine should be substantially de-toxified. These agile
mowers are constructed with single axle and delivered
with either mechanical or hydrostatic drive. The engines
are in the rated power range of 8 - 10 kW. They are generally single or two cylinder 4-stroke engines.
Cylinder volume:
VH = 0.399 dm3
Compression ratio:
e = 7.3
Rated power:
8.1 kW
Rated RPM:
3600 RPM
The investigations mainly concentrated on the more modern OHV engine.
Engine 2, the older side-valved design, was solely measured on the test rig to compare the raw emissions and
thus document the technical progress in the engine
development.
The manufacturer supplied the engines and maintained
them.
According to the manufacturer's specifications, both
engines comply with the CARB 1/96 limits.
The combustion mixture is prepared in a carburetor with
fixed throttle. The machines have an electrical power circuit. This is an important prerequisite for the retrofitting.
Figure 2. Yoke mower manufactured by RAPID /
Dietikon (Switzerland): the test object
2
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means of high-performance liquid
(HPLC) with UV-detection at 360 nm,
4. TEST CYCLE AND TEST METHOD
chromatography
The polycyclic aromatic hydrocarbons (PAH) were sampled from the undiluted exhaust gas on a teflon coated
glass fiber filter in combination with a backup adsorption
filter. The filter extracts were fractionated according to the
VDI-method 3872 [3] and the four- to six-ring PAH fraction analyzed with HPLC with fluorescence and UV
detection.
Particulate mass was measured using the standard dilution-tunnel at a dilution ratio of about 1:5 and temperature
< 52°C. Furthermore particulate number and particulate
substance were analyzed using SMPS and the new ETH
Zürich procedures PAS and DC [4, 5]
5. EMISSION ABATEMENT TECHNOLOGY
Essential aspects of the emission curtailment strategy
are:
Figure 3. Fig. 3:ISO 8178, Type G test cycle
• High performance oxidation catalytic converter (product of HJS)
This cycle is purely steady state and suitably represents
the typical deployment of these engines.
• Electronic mixture control with Lambda sensor in the
exhaust gas ahead of the catalytic converter.
This cycle was run as prescribed for the standard measurements of CO, HC and NOx. The usual parameters,
e.g. power, fuel consumption and through-flow were measured, too.
• Gasoline according to Swiss standard SN 181 163
free of aromatics (Product of ASPEN).
The engine was not modified, with one exception: the fuel
nozzle of the carburetor was replaced by another, slightly
smaller one to allow for lean mixture.
The HC, CO and NOx were measured on-line, undiluted,
according to the standard procedures.
The complex VOC analysis was restricted to a selected
number of test points:
• low idling at 1300 RPM
3-WAY CATALYTIC CONVERTER WITH MIXTURE
REGULATION – Most small engines having catalytic
converters use the common oxidation catalytic converter.
They do not intervene in the engine system. This scheme
only brings negligible improvement because the engines
are operated with a relatively rich mixture. Hence, there is
insufficient oxygen for the oxidation catalysis and the
reduction reaction to curtail the NOx is generally impossible.
• 75% load at 2800 RPM
The comprehensive analysis of the polycyclic aromatic
hydrocarbons was only performed at the 75% load point.
For the VOC determination, a part of the exhaust gas
was continuously drawn through a heated filter (140°C)
and diluted with nitrogen (1 part exhaust + 9 parts nitrogen). Adjustment and periodic checking of the dilution
ratio was done by replacing the exhaust gas at the inlet of
the dilution system with a calibrated carbon dioxide reference gas and monitoring the carbon dioxide concentration after the dilution. The exhaust samples were
collected in tedlar bags and analyzed within four hours at
the EMPA by means of gas chromato-graphy (GC) with
flame ionization detection (FID) using two different GCsystems for the light-end (C2-C5) and the mid-range
hydrocarbons (C6-C12).
Much more impact can be achieved using the regulated
3-way catalysis, as practiced in automobile engines for
decades. Usually, in car engines, the fuel is injected to
enable the necessary mixture control. The small engines
are however simple carburetor engines. The German retrofitting company HJS (project partner) is successfully
marketing a retrofitting system. This was investigated in
the project and is illustrated in Fig. 4.
The new module in this arrangement is the bypass valve
controlled from the central processing unit. This valve circumvents the generally rich-tuned carburetor. Based on
the signal from the oxygen sensor ahead of the catalytic
converter, the processor increases the additional air
quantity. Thus the targeted Lambda value is attained.
The aldehydes were collected by drawing the undiluted
exhaust gas through two impingers in series filled with an
absorption solution of 2,4-dinitrophenylhydrazine (DNPH)
in acetonitrile. The formaldehyde- and acetaldehyde- 2,4dinitrophenylhydrazones produced were analyzed by
3
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GASOLINE FOR SMALL ENGINES ACCORDING TO
SWISS STANDARD SN 181 163 [6] – This fuel is a socalled alcylate gasoline, containing no aromatics at all. It
has been widely used, particularly in the Scandinavian
countries, for several years. In 2-stroke engines, e.g.
chain saws, it curtails the pollutant load of forestry workers. Experience showed that the workplace exposure to
extremely high Benzene concentrations could be drastically minimized. Hence, the typical complaints, e.g. headache, nausea, lack of concentration – consequences of
the aromatics – mostly disappeared.
The project partner company ASPEN and research in
Sweden [7] comprehensively investigated the toxicity and
environmental aspects of this non-aromatic fuel.
The essential properties of this fuel are compared in
Table 2 with the Swiss standard SI-fuel. ("Unleaded 95").
A high priority in the control strategy is to curtail the CO
and HC emissions of these engines. Minimizing NOx is,
however, not given much significance. Within the engine
map, optimum values must be attained in those ranges
where the engine is most likely to operate. Complete regulation at the full load point was sacrificed to prevent
engine component temperature peaks.
Two catalytic converters were employed during the
project:
• Metal substrate catalytic converter;
wound structure, precious metal coating.
Diameter 50 mm, Length 50 mm
This first used catalytic converter attained conversion
rates of 80 - 90%. These values appeared sufficiently
interesting to start the first field test. Verification after 200
hours, however, indicated a noticeable aging. This is due
to overloading the catalytic converter with the very high
raw emissions, at space velocities of over 200,000 1/h.
• Metal substrate catalytic converter;
wound structure precious metal coating
Diameter 70 mm, length 90 mm long,
i.e. the space velocity was quartered.
Further, this catalytic converter had better mass transfer
and substantially improved activity through further development of the coating.
Only the results from the second catalytic converter are
discussed.
4
Example of
product available in Switzerland
Swiss standard
Different criteria influence the choice of the control strategy. The aim can be to minimize certain emission components. However, also engine specific aspects must be
considered. These are, e.g. restricting component temperatures endangered by lean mixtures, and sustaining
engine smooth running (risk of misfiring).
"Quality guidelines for small engine gasoline"
SN 181 163 Swiss quality guidelines for small
engine gasoline.
Swiss standard 181 16 3
Table 2.
Therefore, all elements of the regulated 3-way system
are present. The control unit can contain the engine map
for the entire operating range.
"Unleaded 95"
Figure 4. 3-way catalytic converter system
(HJS/Menden, Germany)
Knock resistance
(octane index)
min.
95
95
97
Density (at 15°C)
kg/m3
725780
680720
696
Vapor pressure
kPa
35-70
35-65
55
Sulfur
max. %
0.1
0.002
Lead
max.
mg/L
13
5
<1
n-Hexane
max.
Vol.%
0.5
< 0.1
Cycloalkane
max.
Vol.%
0.5
< 0.1
Benzene
max.
Vol.%
5
0.1
< 0.005
Aromatics
max.
Vol.%
(30)
0.5
< 0.005
Olefin
max.
Vol.%
7.6
0.5
< 0.005
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Table 4 summarizes the measurements of the 75% part
load point, which is also the basis for the VOC and PAH
analysis.
HC
6. CURTAILING HC, CO, NOX AND FUEL
CONSUMPTION
The following results are the weighted averages according to the ISO 8178 G cycle:
Vehicle
[9]
ULEV
Alcylate
gasoline
with catalyst
Alcylate
gasoline
without catalyst
Standard fuel
with catalyst
HC
9.1
0.7
9.0
0.7
0.09
NOx
3.5
6.3
2.3
4.5
0.04
CO
280
13.1
273
10.2
1.8
Fuel
cons.
461
414
451
396
approx.
350
0.2
6.1
vehicle
[9]
ULEV
Alcylate
gasoline
with catalyst
0.3
0.09
NOx
3.7
8.8
1.7
7.7
0.04
CO
199
0.7
215
0.3
1.8
The impressive performance of this catalytic converter
system is evidenced by the 99.8% conversion rate for CO
and 96% for HC. Further, the absolute values are close to
the ULEV data for modern sophisticated automobile technology. These excellent results were obtained despite the
considerably higher specific raw emissions of this engine
compared to a modern automobile engine in the 100 kW
range. Even better results were obtained during idling,
e.g. a 99% conversion rate for HC and amazing 99.9%
CO - a challenge to the measurement technology.
Emissions accoring to ISO 8178 G weighted
averages of all 6 measured points
Standard fuel
without catalyst
g/kWh
Table 3.
6.2
Alcylate
gasoline
without cat.
g/kWh
Special canister-nozzles are available for refueling this
gasoline. These extract the gasoline vapors from the canister. The fuel flow is automatically stopped as soon as
the tank is full, thus preventing the otherwise not insubstantial spillage losses.
Exhaust gas emissions at 75% load,
2800 RPM
Standard fuel
without cat.
Table 4.
Standard fuel
with catalyst
Switzerland has standardized this fuel at the beginning of
1998. It has surprisingly quickly found a big market. Four
different products are available. 60% of the professional
2-stroke engine market uses this fuel [8]. The Swiss Canton of Bern has legislated the exclusive use of this fuel to
comply with occupational health regulations in forestry.
7. VOC AND PAH ANALYSIS
The VOC-analysis covered the hydrocarbon emission in
the range of C2 to C12, but only the compounds listed in
table 5 were quantified.
The criterion for the selection of the compounds was their
toxicological potency. Although not toxicologically relevant, acetylene was included in the target list as a possible precursor in the formation of benzene and higher
condensed aromatics. An eventual coherence between
the concentration of acetylene and aromatics in the
exhaust would be of special interest in the case of alkylate fuel.
This engine is one of the best according to the Californian certification data. The comparison shows that it nevertheless has all the raw emission components about
100 times higher than a modern automobile engine conforming to the Californian ULEV standard.
The catalytic converter curtails the HC by 92% and the
CO by 96%. The NOx increase was accepted as a consequence of the lean mixture.
The analyzed PAH-fraction (four to six ring PAH) includes
all the probably or possibly carcinogenic PAH according
to the International Agency for Research on Cancer
(IARC) and the US Environmental Protection Agency
(EPA).
Fortunately there is a 10% improvement in fuel consumption.
The use of alcylate gasoline further minimized the emissions, and also benefited the fuel consumption. Its real
advantages however are in minimizing the highly toxic
aromatic compounds as shown in section 7.
In table 5, some of the results at the 75%-part-load with
the new catalyst are presented. The measurements after
a field test showed almost identical emission rates with
the aged catalyst (see table 6).
The efficiency of the catalytic converter system is much
more noticeable at those load points where the mixture
could be completely regulated. In contrast, the averaged
values in Table 3 are spoiled by the rich full load point,
where emission could not be very much improved
because of still rich mixture.
5
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Table 5.
On the other hand there was a significant increase in the
formaldehyde and acetaldehyde emissions with alkylate.
The catalyst was very efficient for these compounds,
although the combination catalyst/alkylate didn't show
the same low aldehyde emissions as the combination
catalyst/standard gasoline.
VOC and PAH species analyzed at two loads
(75%-part-load and low idle)
Analyzed VOC
Ethylene, Acetylene, 1,3-Butadiene1), n-Hexane
The reduction of the carcinogenic PAH to 7 – 10% of the
initial emissions is another impressive example for the
efficiency of these emission reduction strategies.
Benzene1), Toluene, Xylene (ortho-/meta-/para)Ethylbenzene
Formaldehyde1), Acetaldehyde1)
The combination catalyst/alkylate gave even better
results with the engine at idle conditions. No aromatic
hydrocarbons were found in the exhaust gas and for the
other organic compounds, including formaldehyde and
acetaldehyde, the reduction was > 98%.
Analyzed PAH
Fluoranthene, Pyrene, Benzo[b]naphtho[2,1-d]thiophene,
Benz[a]anthracene 2),3), Chrysene2)
Benzo[b]fluoranthene2),3), Benzo[k]fluoranthene2),3),
Benzo[a]pyrene2),3), Benzo[e]pyrene, Dibenz[a,h]anthracene2),3)
8. PARTICULATE EMISSIONS
Ideno[1,2,3-cd]pyrene2),3), Benzo[ghi]perylene, Anthanthrene,
Coronene
Data is available on the particulate emission of small 4stroke SI-engines, e.g. the summary reported in [1].
These indicate a specific emission of 0.5 g/kWh for
engines in the 10 kW range. The German Environment
Agency UBA investigated [10] the state of the technology
for equipment engines. The measured particulate emission values for 2-stroke engines were up to 8 g/kWh and
0.5 g/kWh for 4-stroke engines. The UBA results thus
substantiate the older data as given in [1].
1)
Toxic air pollutant from mobile sources according to US Clean Air
Act, Amendments 1990
2)
Carcinogen according to EPA (Environmental Protection Agency,
Washington, D.C.)
3)
Carcinogen according to IARC (WHO) (International Agency for
Research on Cancer)
Table 5A. VOC- and PAH-emissions at 75%-part-load
These measurements were performed in a manner similar to those for Diesel engines. Information is only available for the total particulate mass at a dilution ratio of
about 1:6 and a mixing temperature of <52°C. No data is
available on the composition of these particulates and
their size distribution. Most authors presume that the particulates from these engines are mainly condensates of
hydrocarbons.
In the present investigations, conventional gravimetric
particulate measurements were performed at the operating points as shown in Fig. 6.
As expected, the use of alkylate reduced the emissions
of aromatics (benzene, toluene, ethylbenzene, xylene) to
0.8 – 3% of the emissions with standard gasoline. The
catalyst brought a similar reduction for the aromatics. The
combination alkylate/catalyst lowered the emission of
these toxic compounds to trace levels, partly below the
detection limit of the analytical method (< 0.1 mg/hr).
Figure 5. Distribution of the operating points for
characterizing the particulates.
Supplementary full load points 1,3,4 were
measured in addition to the operating points
required in ISO 8178 G.
6
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Fig. 6 shows the measured total mass for both engines at
the individual operating points.
1.0E+7
ohne Katalysator
mit Katalysator
1.0E+6
These measurements, too, indicate particulates mass of
similar magnitud, to those cited above. The older engine
attained a level of 0.5 g/kWh (a comparable Diesel
engines has 2 - 3 g/kWh).
Concentration [#/cc]
-3]
Interestingly, the ASPEN fuel has almost no influence on
the particulate formation. In contrast, the catalytic converter (for the particulate emission investigation only the
older catalyst type was used) drastically curtails the particulates at all operating points, on average at least halving the mass. Here, too, both fuels have similar results.
1.0E+5
1.0E+4
1.0E+3
1.0E+2
1.0E+1
10
Durchmesser [nm]
100
1000
100
1000
1.0E+7
1.0E+6
0.25
Bleifrei ohne Kat
Concentration [#/cc]
PM [g/kWh]
1.0E+5
Aspen ohne Kat
0.20
Bleifrei mit Kat
Aspen mit Kat
0.15
0.10
1.0E+4
1.0E+3
ohne Katalysator
mit Katalysator
1.0E+2
0.05
1.0E+1
0.00
10
1
2
3
4
5
6
7
Figure 7. Number count as a function of the mobility
diameter (SMPS method) for both engines at
full load with/without catalytic converter
PM [g/kWh]
PM
0.50
0.40
0.30
0.20
0.10
0.00
1
2
3
4
5
6
top:
the modern OHV 2-cylinder engine 1
bottom:
the older side valve 1 cylinder engine 2
top:
engine 1, 2800 RPM full load ASPEN
above:
engine 2, 2800 RPM full load ASPEN
Both engines indicate very high particulate emissions.
The distribution is noticeably different from those for diesel engines. Diesel engines usually have a maximum for
the size distribution at about 100 nm. However, smaller
particulate diameters predominate in the tested gasoline
engines. The number count without catalytic converter is
quite comparable to those for Diesel engines. The catalytic converter curtails the ultra-fine particulates from the
older engines. However, there is an inexplicable increase
in the range of larger particulate diameters and the
remaining concentrating of fine and ultrafine particles is
very high.
7
Figure 6. Particulate mass at 7 operating points for the 4
variants: 2 fuels, each w/o cat. converter
Bars left → right
Mobility [nm]
Standard w/o Cat
In case of the modern UHV engine, the catalytic converter attains a marked curtailment of the ultrafine particulates. These ultrafine particulates are thus clearly
identified as HC condensates. There is no change in the
profile above 80 nm, i.e. an indication for solid particulates. The attained level is almost as low as the "background" ambient level, i.e. extremely low. The older
engine, however, has a very high particulate count and
may thus be an unacceptable health risk.
Aspen w/o Cat
Standard with Cat
Aspen with Cat
To obtain more information about these particulate emissions, the size distribution of the particulates was measured, using to the SMPS procedure. Fig. 7. shows the
results for comparable full load points, again for both
engines.
It is unclear whether the indeed very small catalytic converter has sufficient capacity to convert the particulate
forming hydrocarbons. Therefore, the tests were
extended to heating the exhaust gas sample, as shown in
Fig. 8.
7
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the ultrafine particulates. The spectrum, after heating to
300°C, is comparable to the ambient background.
These investigations substantiate the suspicion that,
depending on engine design many ultrafine particulates
can be emitted. These are solid particulates and should
not be ignored.
9. FIELD DEPLOYMENT
The engine was first optimized with the compact catalytic
converter. Subsequently, three yoke-mowers were
equipped with the converter system and deployed in the
field during the summer of 1998. The operating duration
was maximum 200 hours. This appears meager but
indeed is representative of the agricultural season.
The field test revealed aging of the first, obviously too
small, catalytic converter. Therefore the system was
improved as described in Section 5. After optimization on
the test rig, the machine was re-deployed in the field during the winter of 98/99.
Measurements were reported after 110 hours of field
operation.
Table 6 summarizes the average results as per ISO 8178 G.
Table 1.
Emissions before and after field test, with
both fuel variants, according to ISO 8178 G
Figure 8. Concentration count as a function of the
mobility diameter (SMPS method) for both
engines at full load with/without catalytic
converter
top:
engine 1, 2800 RPM full load ASPEN
above: engine 2, 2800 RPM full load ASPEN
The procedure [5] is as follows: The exhaust gas is sampled from the dilution tunnel at approx. 50°C, i.e. condensation has occurred. The sample is now reheated. This
vaporizes all condensates with boiling points below the
re-heating temperature. Subsequently, the gas sample
passes through an active carbon trap. The trap adsorbs
the HC vapors and removes them from the gas sample.
The sample still contains the condensates having higher
boiling temperatures, and obviously the solids.
During this period, no deterioration or aging tendencies
were observed, neither for standard fuel nor for alcylate
gasoline. Indeed there was a slight improvement pertaining to CO and fuel consumption. Operations with alcylate
gasoline and catalytic converters (i.e. target) improved
the fuel consumption by 15%, compared to the baseline
of normal fuel and no catalytic converter.
10. CONCLUSIONS
The lower part of the Figure 8 shows the results of the
older side-valve engine. Similar to the results of catalytic
converter deployment, there is only a relatively weak
response to the heating. Re-heating to 300°C certainly
vaporizes all relevant hydrocarbon aromatics. The very
high particulate emissions must therefore be identified as
solid particulates. They may originate from the fuel or
from the lubricant; the source was not traced.
Retro-fitting the modern Briggs & Stratton OHV-engine,
with the innovative 3-way catalytic converter concept
from HJS, curtailed the exhaust gas emissions far
beyond expectations. Simultaneously, using the non-aromatic gasoline also curtailed the entire group of VOC and
PAH to a few percent. Further, compared to its predecessor, with the OHV-engine no serious emissions of
ultrafine particulates could be detected. Therefore, this
system can be recommend for retrofitting. This recom-
The newer OHVengine is shown in the upper part of Figure 8. Its response is similar to the results of the catalytic
converter variant in Figure 7. Heating disperses most of
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mendation was substantiated by the very good results
from field-testing. Parallel investigations indicate that the
changed engine settings only increased engine component temperatures by a few degrees. Hence, the engine
manufacturer has approved the system.
12. REFERENCES
1. Schadstoffemission und Treibstoffverbrauch des OffroadSektors (Pollutant emission and fuel consumption of the
off-road sector) BUWAL, Umwelt-Materialien Nr. 49 / 1996
2. Schweizerische Luftreinhalte-Verordnung (LRV), §89,
Stand 3. Februar 1998,(Swiss clean air act, Status 2-Feb1998
Paragraph 89: The emissions from motorized tools, e.g.
chain saws and lawn mowers, must be curtailed using
improved engine technology, suitable fuels and exhaust
after-treatment, to the extent that the measures are technically and operationally feasible and affordable.)
3. Measurement of Polycyclic Aromatic Hydrocarbons (PAH)
in the Exhaust Gas from Gasoline and Diesel Engines of
Passenger Cars VDI-Richtlinie 3872, Verein Deutscher Ingenieure, Düsseldorf (1989)
4. Particulate Traps for Retro-Fitting Construction Site
Engines VERT: Final Measurements and Implementation
A. Mayer et al., SAE 1999-01-0116
5. Particle Emissions from Diesel Engines - Measurement of
Combustion Exhaust Occupational Exposure
U. Matter et al. 2nd ETH Workshop "Nanoparticle Measurement", Zurich, 7-Aug-1998
6. Qualitätsrichtlinien für Gerätebenzine Schweizer Norm SN
181 163, gültig ab 1.1.98 (Quality guidelines for equipment
gasoline Swiss standard SN 181 163, valid 1-1-98)
7. Alcylate Petrol, Environmental Aspects of Volatile Hydrocarbon Emissions U. Östermark, Doctoral Thesis,
University of Göteborg, Sweden, 1996
8. Aromatenfreie Gerätebenzine lassen Maschinisten aufatmen (Machine operators breath up with non-aromatic gasoline) M. Wyser BUWAL-Bulletin Umweltschutz 2/99
9. Using Advanced Emission Control Systems to Demonstrate LEV II ULEV on Light-Duty Gasoline Vehicles
C. Webb et al. SAE 1999-01-0774
10. Stand der Technik bei den Schadstoffemissions der
Motoren von mobilen Maschinen und Geräten (Benzinmotoren) Abschlussbericht des F & E-Vorhabens 105 06 011
des Deutschen Umweltbundesamtes/Berlin, Juni 1997
(State of the technology for pollutant emissions from
engines powering mobile machines and equipment, Final
report of the R&D proposal 105 06 011 of the German
Environmental Ministry, Berlin, June 1997)
11. Frey/EMPA (EMPA-Report 30.11.1996)
12. Innovative Abgastechnik für die Grenzwerte von heute und
morgen (innovative emission abatement technology to
reach limits of today and tomorrow) HJS Fahrzeugtechnik
GmbH/Menden,
MT/
Motortechnische
Zeitschrift
60(1999)4
13. Industry proposal on a basic outline for the draft amendment to Directive 97/68/EC on Exhaust Emissions from SI
Petrol Engines at or below 18kW
EUROMOT/Frankfurt, 1998
The retrofitting costs are approx. 5 - 7% of the equipment
cost. This is reasonable. Presently, alcylate gasoline is
comparatively expensive. The absolute fuel consumption
of these engines is however very small. Hence, the fuel
costs are not significant.
The proposed system enables suppressing the high
emissions of these intrinsically dirty engines to a level
comparable with modern automobile engines. The environmental and the occupational health benefits are very
substantial. This system can therefore be generally recommended.
11. ACKNOWLEDGMENT
This investigation was performed in collaboration with the
Swiss air quality enforcement authorities, agricultural
research and the industry. The authors particularly thank
the industrial partners that financially supported this
project and also actively participated. They are the
engine manufacturer Briggs & Stratton, the equipment
manufacturer Rapid / Dietikon (Switzerland), the manufacturer of the catalytic converter system HJS / Menden
(Germany) and the manufacturer of the alcylate fuel
ASPEN / Göteborg (Sweden).
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ABBREVIATIONS
AFHB
Abgasprüfstelle Fachhochschule Biel
Biel School of Engineering and Architecture
(Switzerland) http://www.isbiel.ch/A/e.html
ASPEN
ASPEN Petroleum AB / Göteborg (Sweden)
BAT
Best Available Technology
BUWAL
Bundesamt für Umwelt, Wald und Land
schaft Swiss Agency for the Environment, Forests and
Landscape (SAEFL) "Swiss Environmental Protection
Agency" http://www.admin.ch/buwal/e/index.htm
DC
Diffusion Charging
EMPA
Eidg. Materialforschungs- und -prüfanstalt /
Dübendorf (Switzerland) Swiss Federal Laboratories for
Materials Testing and Research, http://www.empa.ch/
FAT
Eidg. Forschungsanstalt für Landtechnik /
Tänikon, Swiss Federal Research Center for Agriculture /
Tänikon (Switzerland)
PAH
Polycyclic aromatic hydrocarbons
PAS
Photoemission Sensor
SMPS
"Scanning Mobility Particle Analyzer" from
TSI / Minneapolis (USA)
TTM
Technik Thermische Maschinen Engineering
Consultants
/
Niederrohrdorf
(Switzerland),
ttm.a.mayer@bluewin.ch
VOC
Volatile Organic Compounds
PARTNER COMPANY WEBSITES
ASPEN / Gothenburg (Sweden):http://www.aspen.se/
HJS / Menden (Germany):http://www.hjs.com/
Rapid / Dietikon (Switzerland):http://www.rapid.ch/
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