Note: Descriptions are shown in the official language in which they were submitted.
135~13
TUR8OCHARGED DIESEL ENGINE COMBINED WITH ~PPARATUS
FOR EXHAUST PVRIFICATION
This invention relates to a turbocharged diesel engine
in combination with apparatus for oxidising particles i~ exhaust
gas emieted from the engine.
Exhaust gas emit~ed from a diesel engine contains
solid/liquid particles (ie solid particles having a liquid outer
covering layer)~ Also prese~t are solid chain aggregate~ (in
which spherical particles of between 100 to 800 x 10-1 m diameter
link up together), liquid sulphates~ liquid hydrocarbons and
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gaseous hydrocarbons such as aldehydes. The solid/liquid
partlcles generally comprise carbon particles with adsorbed liquid
hydrocarbons whereas the solid chain aggregates are generally
composed of high molecular weight organic compounds and/or
inorganic sulphates.
Abou~ 90Z of these particles have maximum dimensions of
less than one micron which i8 within the respirable particle size
and the maxlmum dlmensions of the remaining iO~ of these particles
are le~s than four ~icrons. Usually, the catalytic oxidation of
carbon particles takes place at about 400C whereas their normal
(ie uncatalysed) temperature o~ combustion is 700 to 800C. For
hydrocarbon par~icles cataly~lc oxidation will take place at
~e~peratures about 200C.
~ n ob~ect of the present inventlon is to reduce the
quantity both of noxious gases and particles especially carbon
particles present in exhaust gas emltted fro~ a turbocharged
diesel engine. Noxious gases include hydrocarbons, oxide~ of
nitrogen a~d carbon monoxide.
Accordingly this invention provides a turbocharged
diesel engine in combination with apparatu~ suitable for oxidislng
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particles in exhaust gas emitted from the engine wherein
(a) the apparatus comprises ~alls defining a chamber havi.ng
entry means for receiving exhaust gas from the engine
and exit means through which the e~haust gas can leave
the chamber,
(b) the chamber contains at least one interstitial catalyst
system comprising an interstitial support made from wire
on -~llch is disposed a layer of refractory metal oxide
and in turn there is disposed on or throughout the layer
a catalyst comprising at least one of the metals
platinum, palladium, rhodium, ruthen~um or iridium~
lS (c) the support is shaped 50 as to define an inner
passageway within the support and i~ spaced fro~ -the
chamber walls so as tG define an outer passageway
outside the support,
20 (d) the inner passageway is closed in the region of one end
of the support and the outer passageway is closed at
least in the region of the other end and one oE the
passageways communicates with the entry means and the
other communicates with the exit means so that exhaust
gas received through the entry means passes into one
closed passageway and is then compelled to pass Phrough
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the interstitital catalyst system into the other closed
passgeway and
(e) the inner and outer passage~ays are aligned relative to
the entry mean~ such that exhaust glas flowing through
the chamber is compelled to flo~ $n a direction
transverse of the entry means during a portion of its
passage through the chamber thereby increasing
turbulence,
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~he catalyst comprises the metals platinum, palladium9
rhodi~m, ruthenium or iridium either alone or as an alloy or
intermetallic compound containing at least 20 wt % o~ one or more
of the metals.
The layer of refractory metal ogide is preferably a
washcoat layer containing oxides o~ one or more members of the
group consi~ting of Mg~ Ca, Sr, Ba, Sc, Y, the lanthanides, Ti,
Zr, Hf, Th, Ta, V, Cr, ~n, Co, Ni, B, Al, Si and Sn~ Preferred
washcoat material~ are A1203 and alumina hydrates and stabllsing
oxides such as BaO and oxides promoting catalytic activity 8uch as
TiO2, ZrO2, HfO2, ThO2, Cr203 and NiO are also preferably present.
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The wire from which the support is made is preferably
formed from base metal alloys which are corrosion resistant and
preferably oxidation resistant. Examples of such base metal
alloys are nickel and chromill~ alloys having an aggregate Ni plus
Cr content greater than 20% by weight and alloys of iro~ including
at least one of the elements chromium (3 to 40) w~ %, aluminium (1
to 10) wt %, cobalt (trace to 5) wt %, nickel ~trace to 72) wt %
and carbon (trace to 0.5) wt %. Such supports are described in
German DOS 2450664.
Other examples of base metals capable of withstanding
the rigorous conditions required are iron-aluminium-chromium
alloys which may also contaiD yttrium. The latter alloys may
contain 0.5 to 12 wt-Z Al, 0.1 to 3.0 wt % Y, O to 20 ~t % Cr and
balance Fe. These are described in United States Patent
~o. 302725Z.
.
Alternatively the base metal alloys may have less
corrosion resistance, eg mild steel, but with a protective coating
compositlon covering the surface of the substrate as described in
our co-pending British Patent application No. 7903817 dated
2 February 197g (now GB 2013517A).
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The thickness of the wire is pref~rably be~ween 0.254 to
508 mm and especially betwee~ 0.0254 to 0.305 mm~ Preferably
prior to its fabrication into woven, knitted or crushed form, the
wire is rolled down to a ribbon having two flat opposite surfaces.
The invention i6 further illustrated by the following
specific embodiments described with reference to Figures 1 to 7 o~
the drawings and by the following Examples. In the drawings,
Figure 1 show~ a section through an apparatus
suitable for use in combination with a
turbocharged diesel engine acording to the
inventlon,
Figures 2, each show on a larger scale sections
5, 6 and 7 through e~bodiments o~ alternative
apparatus,
Figure 3 shows in perspective an assembly of
spaclng bars suitable for acting as a
central framework to prevent the
interstitial support collapsing in~ardly.
Figure 4 shows in perspective an alterna~ive central
framework.
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Figure 1 shows an apparatus 1 for use in combination
with a turbocharged diesel engine (not shown~ in order to oxidise
particles contained in exhaust gas emitted from the engine.
Apparatus 1 comprises walls 21a and 21b which define chamber 2
having entry ports 27 to 30 for receiving exhaust gas from the
engine and having exit port 32 through which exhaust gas can leave
chamber 2 and enter exhaust pipe 31. Entry ports 27 to 30 are
suitable for mounting adjacent to and in communication wlth
exhaust ports in the engine.
Chamber 2 contains interstitial catalyst system 23
comprising all interstitial support, a layer of refractory metal
oxide and a catalyst. Interstitia1 catalyst system 23 is shaped
around spacing tube 22 so as to define cylindrical inner
passageway 3. Spacing tube 22 should be perforated or made from
wire mesh so as to permit exhaust gas to flow from catalyst system
23 into inner passgeway 3, One end of inner passage~ay 3 is
closed by disc 26 located at one end of catalyst system 23 and the
other end of inner passageway 3 communicates with exit port 32.
Spaclng tube 22 i.9 supported centrally withl~ chamber 2
by means of annular disc 25 with the result that the support (not
shown) within catalyst system 23 is spaced from chamber wall 21b
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so as to define outer passageway 4 which communlcates with entry
ports 27 to 30. Both ends of outer passageway 4 are closed by
walls 21a. Inner and outer passage~ays 3 and 4 extend
transversely of the direction of entry of exhaus~ gas into cha~ber
2 as shown by arrows F41 to F44.
Exhaust gas from the engine received by entry ports 27
to 30 passes into outer passagewy 4 and is then eompelled to pass
through interstitial catalyst system 23 into inner passagew~y 3
where it ls compelled to execute a sharp turn as shown by arrow
before leaving chamber 2 via exit port 32. Interstitial
catalyst system 23 induces turbulence in the flow of exha~tst gas
and the general direction of the turbulent flow through chamber 2
is indicated by arrows F41 to F45. In particular, flow ~ithin
inner passa~eway 3 is transverse of the flow in entry ports F41 to
F44.
The in~erstltial support in the catalyst system is
preferably made of knitted wire mesh. This may be fabricated lnto
a slngle monolith or it may be made up in annular secti.ons, The
layer of reractory metal oxide ~7ashcoat and the catalyst may be
applied to each sectlon of the wire support separately or after
the sections have been linked together~ .
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Figure 3 shows an alternative central structure in which
in place of tube 22 ~here is provided a series of 5 rlgid spacing
bars, 100 to 500, running the length of chamber 2~ Bars 100 to
500 are maintained in fixed spatial relationship to one another by
spacing plates 600. Accordingly bars 100 to 500 hold catalyst
system 23 rigidly in place within chamber 2. Spacing plates 600
in pairs connect thrae of the fi~e bars and are usually at right
angles to each other thus being disposed along a diameter of
central cylindrical passageway 3~ Two or more pairs of spacing
plates 600 may be adapted to extend the whole leng~h of chamber
21b as shown in Figure 4 whereupon ~hey may be used as spacing
means instead of bars 100 to 500.
Rods and spac~ng ~lates need to be constructed of a
material resistant to oxidatlon up to at least 800C.
Figure 2 shows an alternative apparatus 5 in which a
chamber 6 is defined by walls 100~ Chamber 6 has en~ry ports 101
and 102 comprising sleeves 106 and 107 adjacent to and in
communication with engine exhaust ports ~not shown). Chamber 6
also has exit port 103 adjacent ~o an exhaust pipe (not shown).
Chamber 6 contains an interstitial catalyst system 104
(comprising a support, a layer of re~ractory metal oxide and a
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catalyst) shaped around spacing plates 105 as shown in Figure 4 so
as to define an ~nner passageway 110. Catalyst system 104 is
disposed centrally within chamber 6 and transversely of entry
ports 101 and 102 so as to define an outer transverse passageway
104a. One end of inner passageway 110 is closed by disc 108 and
one end of outer passageway 104a is closed by end ~all 104a.
Exhaust gas received by entry ports 101 and 102 flows
into inner passageway 110 where it executes a sharp turn as
lndicated by arrows Fg2 to Fgg and and is compelled to pass
through interstit~al cataiyst system 104 into outer pasgeway
104a. In outer passageway 104a, the flow execu~es a further sharp
turn so that the exhaus~ gas passes along outer pasageway 104a in
a direction tra~sverse of its direction through entry ports 101
and 102. Passage through intersei~al catalyst system 104 imparts
turbulence ~o the flow of exhaust gas and the ge~eral direction of
turbulen~ flow through chamber 6 ls indicated by arrows FgO to
F109
Apparatus 5 would usually be used with more than two
entry ports, but for simplicity only two are shown in Figure 2.
The support for the catalyst system 104 is preEerably of
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knitted wlre which may be made up into four sections or three
units. If the support is in sections, eg of doughnut
configuration, these are normally linked together before the
support ~s placed in the chamber.
Figures 5 and 6 show a further alternative apparatus 7
in which walls 51 define a chamber 8 containing openiDgs 52 and
53. Chamber 8 contalns an interstitial catalyst sys~em 64
comprising a support 7 a layer of refractory metal oxide and a
catalys~ and is shaped around spacing plates 65 so as to define
innar passageway 60. Catalyst system 64 is spaced from walls 51
so as to define outer passageway 56. One end of inner passageway
60 is closed by disc 67 and the end of outer passageway 56 which
is remote from disc 67 is closed by end wall 51 so that gas
flowing from one passageway to the other is compelled to pass
through interstitial catalyst system 64.
Figure 5 ShoW8 a chamber 8 sultable ~or yositioning
between a turbocharger and an exhaus~ pipe ~neither shown).
Opening 52 i9 positioned ad~acent and in communication wlth the
outlet from the turbocharger and so functlons as an entry por~
receiving exhaust gas. Opening 53 is positioned ad~acent the
exhaust pipe and serves as an exit for the exhaust gas leavlng
chamber 8. The ~low of exhaust gas ~hrough chamber 8 ls lndicated
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by arrows Fsl to F66 from which it will be seen that the exhaust
gas executes sharp turns and flows transversely of the axes of
openings 52 and 53 during its passage through catalyst system 64.
Figure 6 lllus~rates the use of apparatus 7 downstream
of a turbocharger whereupon opening 53 functions as the entry port
. and o?ening 52 as the exit port. The flow of exhau3t gas is
reversed as compared with th~t shown in Flgure 5. The flow is
indicated by arrQW~ F71 to ~86-
Figure 7 shows a modification of the embodiment show~ in
Figure 5, the modification being suitable for use with large
capacity engines.
The essential difference between the embodiment shown in
Yigure 5 and the modiication is that chamber 9 of the
modification contaLns a plural:Lty of ad~acent catalyst systems 203
to 205. System 204 is spaced apart from both systems 203 and 205
so as to define additional outer passageways between both systems
203 and 204 and systems 205 and 204.
Discs 209 to 211 close inner passageways in systems 203
to 205 and plate 212 closes ends of outer passagewaysO The flow
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of exhaust gas through chamber 9 is indicated by arrows P20 to
F24~.
~XAMPLE 1
In order to illustrate the per~ormance oE this
lnvention, the exhaust syste~ leading from a turbocharged
multicylinder engine of capacity 2000 cc and suitable for powering
a commercially available diesel engined automobile was ~odified by
fitting one of two alter~atlve e~haust-purification apparatus
. dDwnstrea~ of the turbocharger between the outlet from the
turbocharger and the exhaust pipe.. The alternative apparatus will
be referred to as Apparatus A and Apparatus B~ Apparatus A was as
described above with reference to Figure 6, tha~. is to say wlth
e~haust gas flowing from central passageway 60 radially outwards
into outer passageway 56. Apparatus B was as described above with
reference to Figure 5, that is to say with exhaust gas flowlng
radially i~ward~.
~ 1e inters~itial support for the catalyst was fabricated
from knitted 310 stainless s~eel wire of diameter 0~254 mm which
had been flattened. A layer of washcoat containlng alumina,
barium oxide and ceria was applied at a loading of 0.34 g/g of
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wire. The washcoated support was impregna~ed with 5.7% Rh, 94.5%
Pt at a loadlng of 918 g c~-3. The volume of support used was
2114.6 cm~3. The measurements were taken after the car had been
driven 250 miles (400 km).
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The results were obtained by d~iving tha automobile
through the LA4 diesel cycle. The L~4 cycla ~the Los Angeles
cycle) is laid down by the Environmental Portection Age~cy (EPA~
in the United States aud is a standard tes-t cycle deivsed to
simulate a dri~e to work in Los ~ngeles trafic conditions. It is
furthermore a test which is used to show the effectiveness or
otherwise of an exhaust-purification apparatus fitted to an
automobile. The hydrocarbons, carbon monoxide, nitrogen oxides
and particles present in the exhaust gas e~issions were measured
in g/mile (or g/km). Baseline measure~ents were taken of the
pollutant levels in the exhaust gas beore it passed through the
apparatus.
The results are given in Table 1 as follows:-
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TABLE 1
Baseline Apparatus Apparatus
_ _ B
Particles 0.4 0.31 0032
g/mile (g/km)
percen~age change (0.25) ~0,19) (0.20)
NOX 1.75 2 2.1
g/mile (glkm)
percen~age change (0.10) (1.24) (0.75)
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CO 1.25 0.2 0.46
g/mile (g/km) .
percentage change tO.76) (0~12) (0.29)
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Eydrocarbons 0.2 0.07 0.11
g/mile (g/bm)
percentage change (0.12~ (0.04) (0.07)
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Back ~axlmum~ 13545 22011 2268
Pressure percentage .
~m~2 difference ~ _ -62~5 -67.5
lS Minimum 3386 4402 4402
percentage
.- difference -30 -30
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EXAMPLE 2
A commercially available car with a 2.2 litre
turbocharged diesel engine was fitted with Apparatus A downstream
of the turbocharger as described above. The catalyst was
supported on an interstitial support ~ade of knitted wire
fabricated from 304 stainless steel wire of diameter 0.254 mm and
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O.127 mm before being treated to produce flattened wire. Knitmesh
fabricated from the small diameter wire was used to make up the
inner portion of the support and the outer portion was made up
from the knitmesh fabricated from the larger diameter wire. A
washcoat of alumina at a loading of 0.22 g/litre of the catalyst
system. The catalytic metal used was 7-~ Rh 92~X Pt at a loading
of 0.09% by weight~ The total volume of the catalyst system uas
2.6 litres~
With the car running through the LA4 cycle the baseline
measurement of particles was 0.4 g/mile (0~25 g/~m3. After the
exhaust had passed through the chamber the level of partlcles
present was 0.19 gtmile (0.12 g¦km) which is a reduction o~
52.5%. The maximum back pressure over the whole system was 13545
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EXAl~LE 3
A serles of tests were conducted using a diesel engine of capacity
14748 cm3 turbocharged to 1.6 bar. Apparatus was fitted 1.22 m
from the turbocharger and contained catalyst systems arranged
in parallel as shown in Figure 7 except that nine systems were
used in parallel instead of three shown in Figure 7. The volume
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of the total catalyst system used was 21303 cm 3. The support,
washcoat and catalytic metals used were the sa~e as for the
catalyst system tested in Example 2.
The engine was run through the EPA 1980 new transient
cycle test as laid dow~ by the EPA in the USA. Measurements of
the lavel of particles present in the exhaust gas after tha
catalyst chamber were taken at intervals of 5 hours, The results
are given in Table 2 below.
TABLE 2
Particles in g MLT-l
BaselineAfter catalyst Percentage
cha~ber change
_ _ . _
0~224 0.0745 66.7
0.0782 65
0.0745 66.7
0.1043 53.4
0.0820 63.4
0.0708 68.4
0.0782 65
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The level of hydrocarbons in the exhaust gas wa5 reduced
from 600 ppm to 12 ppm by the apparatus. The maximum temperature
of the exhaust through the apparatus was 388C. The ~aximum back
pressure of the chamber was 249 ~m-2.
The examples show the effectiveness of the apparatus in
removing particles and other pollutants from an exhaust gas
emitted from a diesel e~gine even when the appartus is posi~ioned
at a di~tance from the engine and has to operate at a }ower
temperature.
