Fuel reforming system for an internal combustion engine

A system for converting a rich air-fuel mixture to a reformed gaseous mixture containing hydrogen and for feeding the reformed gaseous mixture to an internal combustion engine comprises a carburetor for producing the rich air-fuel mixture, a vortex combustion type burner for imperfectly burning the mixture to produce heat and partially oxidized gaseous mixture, and a reactor vessel provided therein with a catalyst bed of annular cross-section. The partially oxidized gaseous mixture flows radially inwardly through the catalyst bed into a central passage defined by the annular catalyst bed so that the partially oxidized gaseous mixture is completely converted into the reformed gaseous mixture during the passage through the catalyst bed.

BACKGROUND OF THE INVENTION 
1. FIELD OF THE INVENTION 
The present invention relates generally to an internal combustion engine 
operable with a mixture of air and a fuel such as hydrocarbon fuel (for 
example, gasoline) or alcohols (for example, methyl alcohol) and, more 
particularly, to a fuel reforming system for converting a rich mixture of 
air and the fuel into an easily combustible reformed gaseous mixture 
containing hydrogen and for feeding the reformed gaseous mixture into a 
combustion chamber or chambers of the engine for the improved combustion 
therein to thereby reduce the emission of the harmful components of the 
engine exhaust gases. 
2. Description of the Prior Art 
In order to reduce the harmful components of engine exhaust gases, there 
has been proposed an intake system for an internal combustion engine. The 
proposed intake system was provided with a fuel reforming system in which 
a hydrocarbon fuel such as gasoline was merely added with water, air and 
the engine exhaust gas to form a mixture which was then introduced into a 
reactor provided with a catalyst for the catalytic reaction between the 
components of the mixture at a temperature of from about 250 to about 
1,000.degree. C. so that a part of the fuel was reformed into hydrogen, 
carbon monoxide and/or methane to be fed into the engine. There has also 
been proposed another type of intake system designed to supply an 
associated engine with a mixture of hydrogen gas from a hydrogen container 
and a hydrocarbon fuel from a fuel tank. 
The proposed fuel reforming system of the first-mentioned type of intake 
system required a water container, which caused a problem that the water 
in the container was frozen with a burst of the container in winter season 
or a cold district. In the case where the fuel used contained a compound 
of lead, the engine exhaust gas recirculated into the reactor contained 
the lead compound by which the catalyst was damaged. Even in the case 
where the fuel did not contain the lead compound, soot and/or tar was 
included in the engine exhaust gas and deposited on the surface of the 
catalyst carrier to reduce the efficiency of the catalyst. The reformed 
gaseous mixture, moreover, included gaseous components which were 
unnecessary for the engine operation and which reduced the efficiency of 
charge of the reformed gaseous mixture into the combustion chambers of the 
engine and adversely affected the engine performance. 
The second-mentioned type of intake system required a hydrogen container 
which was accompanied by a danger of explosion, inevitably bulky in size 
and heavy. Thus, this type of intake system was not suitable for an 
internal combustion engine for an automobile. 
SUMMARY OF THE INVENTION 
In order to eliminate or minimize the disadvantages of the prior art intake 
systems for internal combustion engine, the present invention aims to 
provide an improved fuel reforming system for an internal combustion 
engine which is operative to convert safely, economically and without 
adversely affecting the engine performance, a rich mixture of air and a 
fuel into a reformed gaseous mixture rich with hydrogen and which can be 
compact and installed in a narrow engine compartment of an automobile. 
The fuel reforming system according to the present invention includes means 
for producing a rich mixture of air and a fuel such as gasoline. The rich 
mixture producing means may preferably be a conventional carburetor, but a 
fuel injection device can alternatively be employed. A burner is provided 
to imperfectly burn the thus produced rich air-fuel mixture for causing 
partial oxidizaton of the fuel contained in the rich air-fuel mixture 
thereby to produce a partially oxidized gaseous mixture. In order to 
stably and continuously obtain the imperfect burning of the rich air-fuel 
mixture of a small air-fuel ratio, the burner used in the present 
invention is of vortex combustion type and has a preswirling chamber 
connected to the rich mixture producing means so that the rich air-fuel 
mixture is introduced into the pre-swirling chamber to form a vortex of 
the rich air-fuel mixture therein, an ignition chamber disposed in 
communication with the pre-swirling chamber and provided with an igniting 
means for igniting the rich air-fuel mixture received from the 
pre-swirling chamber, and an imperfect combustion chamber disposed in 
communication with the ignition chamber for receiving the thus ignited 
rich air-fuel mixture from the ignition chamber to cause the partial 
oxidization of the fuel and produce the partially oxidized gaseous 
mixture. 
A reactor vessel is connected to the burner and provided with an inlet 
through which the interior of the vessel is communicated with the 
imperfect combustion chamber of the burner. The reactor vessel is also 
provided with an outlet leading to the combustion chamber of an associated 
engine. 
Generally tubular means defining therein a central passage and a generally 
tubular chamber surrounding the central passage and being in fluid flow 
communication therewith are disposed in the reactor vessel so that the 
tubular means and the reactor vessel cooperate to define the therebetween 
a second passage surrounding the tubular chamber and being in fluid flow 
communication with the imperfect combustion chamber and with the tubular 
chamber and so that the central passage is connected to the outlet of the 
reactor vessel, whereby the partially oxidized gaseous mixture can flow 
from the imperfect combustion chamber through the second passage into the 
tubular chamber. The tubular means may preferably be in the form of a pair 
of substantially cylindrical and perforated walls formed of punched sheet 
metals or wire screens. 
A catalyst means is disposed in the tubular chamber for facilitating 
catalytic conversion of the partially oxidized gaseous mixture to a 
reformed gaseous mixture containing hydrogen. The reformed gaseous mixture 
thus produced flows out of the tubular chamber into the central passage 
and then through the outlet of the reactor vessel toward the combustion 
chamber of the engine. The catalyst may be in the form of granular 
catalyst carriers or particles which form a catalyst bed received in the 
tubular chamber. 
The provision of the second passage between the generally tubular means and 
the reactor vessel and in fluid flow communication with the imperfect 
combustion chamber and with the tubular chamber in which the catalyst 
means is disposed assures that the imperfect burning of the rich air-fuel 
mixture initiated in the ignition chamber of the burner stably continues 
by the time the ignited rich air-fuel mixture has moved through the second 
passage, so that the partial oxidization of the rich air-fuel mixture is 
facilitated. Then, the partially oxidized rich air-fuel mixture flows into 
contact with the catalyst means and is converted into the reformed gaseous 
mixture by catalytic reforming reaction produced between components of the 
partially oxidized rich air-fuel mixture. The reformed gaseous mixture 
thus produced contains a large percentage of hydrogen and is easily 
ignitable and combustible in the engine combustion chamber at a very large 
air-fuel ratio at which an ordinary mixture of air and a merely atomized 
hydrocarbon fuel is hardly ignitable and combustible. This greatly 
contributes to the reduction in the emission of harmful exhaust 
components; hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxides 
(NO.sub.x), and particularly the reduction in the emission of nitrogen 
oxides. 
In addition, the particular arrangement of the burner and the reactor 
vessel and, particularly, the arrangement of the reactor vessel and the 
catalyst means, as discussed above, ensures that the entire system can be 
made very compact and thus installed in a very small or narrow engine 
compartment of an associated automobile. 
The above and other objects, features and advantages of the present 
invention will be made more apparent by the following description with 
reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, a preferred embodiment of the fuel reforming system 
according to the present invention is generally indicated by 100 and 
designed to be used with an internal combustion engine generally indicated 
by 10. The engine 10 is shown as being of the type that comprises a 
cylinder 12, cylinder head 14 mounted on the top of the cylinder 12, a 
piston 16 reciprocally mounted in the cylinder 12 and cooperating with the 
cylinder 12 and the cylinder head 14 to define a combustion chamber 18, 
intake and exhaust ports 20 and 22 formed in the cylinder head 14, and 
intake and exhaust valves 24 and 26 movably mounted on the cylinder head 
14 to control the communication of the intake and exhaust ports 20 and 22 
with the combustion chamber 18. An intake pipe 30 extends between an air 
filter 32 and the intake port 20. A throttle valve 34 is pivotally mounted 
in the intake pipe 30 and operatively connected to an acceleration pedal 
(not shown) of an associated automobile by any conventional mechanical 
connecting means such as a link mechanism (not shown). The intake pipe 30 
has an expanded or bulged portion 36 disposed downstream of the throttle 
valve 34 and defining therein a mixing chamber 38 for the purpose to be 
made apparent later. 
The fuel reforming system 100 shown in FIG. 1 comprises means 110 for 
producing a rich mixture of air and a hydrocarbon fuel, such as gasoline, 
and a fuel reforming device for converting the rich air-fuel mixture into 
a reformed gaseous mixture containing hydrogen and feeding the thus 
converted, reformed gaseous mixture into the internal combustion engine 10 
for the ignition and combustion therein. 
In the illustrated embodiment of the invention, the rich air-fuel mixture 
producing means 110 is a carburetor connected by an air pipe 112 to the 
intake pipe 30 between the air filter 32 and the throttle valve 34. An air 
pump 114 is provided in the air pipe 112 to pump air from the intake pipe 
30 to the carburetor 110. The fuel is supplied in liquid state from a fuel 
tank 116 to the carburetor 110 by a fuel pump 118. 
The fuel reforming device includes a burner 160 of vortex combustion type 
and a generally cylindrical reactor vessel 200 connected to the burner. 
The burner 160 is for igniting the rich air-fuel mixture produced by the 
carburetor 110 to cause "partial or imperfect oxidization" of the mixture. 
The words "partial or imperfect oxidization" are used herein to mean such a 
reaction that carbon (C), for example, is oxidized not to such an extent 
as to produce carbon dioxide (CO.sub.2) but to such an extent as to 
produce carbon monoxide (CO). The burner 160 includes a pre-swirling 
chamber 162 defined by a generally cylindrical peripheral wall 164 and end 
walls 166 and 168. The carburetor 110 is connected to the pre-swirling 
chamber 162 by a rich mixture supply pipe 170 extending tangentially to 
the periphery of the pre-swirling chamber 162 so that the rich air-fuel 
mixture supplied from the carburetor 110 into the pre-swirling chamber 162 
is formed into a vortex of the rich air-fuel mixture therein. One of the 
end walls 168 of the pre-swirling chamber 162 is formed therein with a 
discharge aperture 172 through which the chamber 162 is communicated with 
an ignition chamber 174 defined by the end wall 168 of the pre-swirling 
chamber 162 and a generally cylindrical peripheral wall 176 connected to 
the end wall 168. The ignition chamber 174 is of a diameter slightly 
smaller than that of the pre-swirling chamber 162 and provided with a 
sparking plug 178 mounted on the peripheral wall 176 by means of a holder 
180 to ignite the rich air-fuel mixture flowing from the pre-swirling 
chamber 162 through the aperture 172 into the ignition chamber 174. 
Preferably, the sparking plug 180 is of a design that has a single or 
center electrode 181 which is somewhat longer than the center electrode of 
an ordinary type sparking plug and which is bent at the free end portion 
to form a spark gap between the end extremity of the electrode 181 and a 
part of the peripheral wall 176. The sparking plug 178 is electrically 
connected to an ignition control system 182 which may be of a conventional 
construction and arrangement. 
The end of the ignition chamber 174 remote from the pre-swirling chamber 
162 is open to a generally cylindrical, partial or imperfect combustion 
chamber 184 of a diameter larger than that of the pre-swirling chamber 
162. The imperfect combustion chamber 184 is defined by a generally 
cylindrical peripheral wall 186 and annular end walls 188 and 190. The 
annular end wall 188 defines therein a generally circular opening 192 of a 
diameter larger than that of the ignition chamber 174, while the other 
annular end wall 190 is connected along its inner peripheral edge to the 
end of the ignition chamber peripheral wall 176 remote from the 
pre-swirling chamber 162. A secondary air pipe 194 is connected at one end 
to the air pipe 112 between the air pump 114 and the carburetor 110. The 
other end of the secondary air pipe 194 is connected to the peripheral 
wall 186 of the imperfect combustion chamber 184 so that the downstream 
end of the secondary air pipe 194 is tangentially open to the imperfect 
combustion chamber 184 to cause the secondary air to swirl therein. 
The imperfect combustion chamber 184 is communicated through the opening 
192 with the interior of the reactor vessel 200 having an inner diameter 
larger than that of the imperfect combustion chamber 184. The reactor 
vessel 200 has a substantially cylindrical peripheral wall 202, a first 
annular end wall 204 connected to the peripheral wall 186 of the imperfect 
combustion chamber 184 and a second annular end wall 206 defining therein 
an outlet opening 208. A pair of substantially cylindrical and radially 
spaced walls 210 and 212 formed therein with a plurality of apertures 211 
and 213, respectively, are disposed within the reactor vessel 200 so that 
the cylindrical walls 210 and 212 are substantially coaxial with the axis 
of the reactor vessel 200 and so that the outer cylindrical wall 210 is 
radially inwardly spaced from the peripheral wall 202 of the reactor 
vessel 200 to define therewith an annular passage 214. The cylindrical 
walls 210 and 212 are preferably formed by punched sheet metals or wire 
screens and have downstream ends connected to the downstream end plate 206 
of the reactor vessel 200. The upstream ends of the cylindrical walls 210 
and 212 are spaced from the upstream end plate 204 of the reactor vessel 
200. A disc-like closure plate 216 is secured to the upstream ends of the 
cylindrical walls 210 and 212, so that the closure plate 216 cooperates 
with the annular end wall 188 of the imperfect combustion chamber 184 and 
with the annular upstream end wall 204 of the reactor vessel 200 to define 
a circumferentially continuous space or passage 218 which is communicated 
with the annular passage 214, while a part of the closure plate 216, the 
pair of cylindrical walls 210 and 212 and a part of the downstream end 
wall 206 of the reactor vessel 200 define an annular chamber 220 which is 
filled with catalyst particles forming a catalyst bed 222. Thus, the 
annular chamber 220 is called hereunder "catalyst chamber". The central 
part of the closure plate 216 and the inner cylindrical wall 212 define a 
central passage 224 which is closed at its upstream end by the closure 
plate 216. The annular passage 214, the catalyst chamber 220 and the 
central passage 224 are communicated with each other by the apertures 211 
and 213 in the cylindrical walls 210 and 212. A delivery pipe 226 
interconnects the reactor vessel 200 and the bulged portion 36 of the 
intake pipe 30 of the engine 10 so that the central passage 224 in the 
reactor vessel 200 is communicated with the mixing chamber 38 in the 
intake pipe 30 through the outlet opening 208 in the reactor vessel end 
wall 206 and through the delivery pipe 226. A conventional flap valve 228 
is pivotally mounted in the delivery pipe 226 and operatively connected by 
a conventional mechanical connecting means 230 to the throttle valve 34 in 
the intake pipe 30 for the purpose to be made apparent later. 
The catalyst bed 222 formed by the catalyst particles may alternatively be 
in the form of an integral catalyst carrier (not shown) having a tubular 
and hollow shape defining therein an axial central passage like the 
passage 224 in the embodiment shown and a plurality of small radial 
passages. The alternative catalyst carrier may comprise a honeycomb 
structure of a ceramic material. 
Examples of the catalyst carried by the catalyst particles forming the 
catalyst bed 222 or by the alternative integral catalyst carrier are 
nickel, copper, chromium, cobalt, platinum, rhodium and a combination of 
some of these materials. These catalyst materials, when contacted by a 
mixture of air and a hydrocarbon fuel, facilitate thermal decomposition of 
the fuel and stream reforming of the air-fuel mixture. 
In operation, the carburetor 110 produces a rich mixture of air and a 
hydrocarbon fuel. In the case where gasoline is used, the rich air-fuel 
mixture should be of an air-fuel ratio ranging from 3 to 9. The rich 
air-fuel mixture is supplied through the rich mixture supply pipe 170 
tangentially into the pre-swirling chamber 162 so that the rich air-fuel 
mixture swirls in the pre-swirling chamber 162 to form a vortex, whereby 
the fuel contained in the swirling air-fuel mixture is effectively 
atomized. The air-fuel mixture then flows through the discharge aperture 
172 into the ignition chamber 174 and is ignited by the sparking plug 178. 
The ignited air-fuel mixture then flows into the imperfect combustion 
chamber 184 in which an imperfect combustion or partial oxidization of the 
mixture is initiated while the mixture is diluted by secondary air 
introduced through the secondary air pipe 194 tangentially into the 
imperfect combustion chamber 184 in such a manner that the air swirls in 
the chamber 184, as diagrammatically illustrated in FIG. 2. It is to be 
noted that, although the air-fuel mixture produced by the carburetor 110 
is very rich and not easily combustible, the tangential introduction of 
the secondary air facilitate stable and continuous imperfect combustion of 
the mixture so that an imperfectly burnt gas-mixture is produced. The 
air-fuel ratio of the total of the rich air-fuel mixture produced by the 
carburetor 110 and the secondary air fed into the imperfect combustion 
chamber 184 ranges from 5 to 10 when the fuel is gasoline and, preferably, 
5 to 6.5 at which the hydrogen content of a reformed gaseous mixture to be 
obtained is maximum. The imperfectly burnt gas mixture is then introduced 
through the opening 192 into the circumferentially continuous space or 
passage 218 in the reactor vessel 200 and then into the annular passage 
214. The partial oxidization of the fuel by the imperfect combustion of 
the air-fuel mixture stably continues by the time the mixture has moved 
through the annular passage 214. Then, the mixture flows through the 
apertures 211 in the outer cylindrical wall 210 into the catalyst chamber 
220 in which the catalyst bed 222 has already been heated to and kept at a 
temperature ranging from about 600.degree. to 900.degree. C. (in certain 
cases, to higher than 1,000.degree. C.) partly by the imperfect combustion 
of the air-fuel mixture entering the catalyst chamber 220 and partly by 
the heat produced by a catalytic reaction which is induced on the surfaces 
of the catalyst particles of the catalyst bed 222 between small amounts of 
non-reacted parts of oxygen and the fuel. Thus, the catalyst carried by 
the catalyst particles of the catalyst bed 222 has been activated, so that 
the imperfectly burnt air-fuel mixture entering the catalyst chamber 220 
is completely converted into a reformed gaseous mixture containing a large 
percentage (about 5% by weight) of hydrogen during the passage of the 
air-fuel mixture through catalyst bed 222 and in contact with the catalyst 
particles thereof. The reformed gaseous mixture thus obtained flows 
through the delivery pipe 226 into the mixing chamber 38 and is mixed with 
air from the air filter 32. The flap valve 228 and the throttle valve 34 
are operable to control the flow of the reformed gaseous mixture through 
the delivery pipe 226 into the mixing chamber 38 and the flow of the air 
to the mixing chamber 38, respectively, so that the reformed gaseous 
mixture and the air are mixed in the mixing chamber 38 at a proper mixing 
ratio to form a diluted reformed gaseous mixture to be introduced into the 
combustion chamber 18 in the engine 10. The diluted reformed gaseous 
mixture is easily combustible in the engine combustion chamber 18 even at 
a very lean air-fuel ratio because of the presence of hydrogen in the 
diluted reformed gaseous mixture. Thus, the system of the present 
invention is effective to reduce three harmful components, hydrocarbon 
(HC), carbon monoxide (CO) and nitrogen oxides (NO.sub. x), of the engine 
exhaust gases. 
FIG. 3 illustrates a modification of the fuel reforming system shown in 
FIG. 1. The modification is characterized by a feature that the rich 
air-fuel mixture produced by the carburetor 110 is first pre-heated by the 
reformed gaseous mixture produced by the fuel reforming system 100 and 
then fed into the pre-swirling chamber 162. More specifically, the rich 
mixture supply pipe 170 of the embodiment 100 shown in FIG. 1 is replaced 
by a rich mixture supply pipe 170' which includes a first part 170a 
connected to the carburetor 110 and extending radially inwardly through 
the peripheral wall 202 of the reactor vessel 200, the annular passage 
214, the outer cylindrical wall 210, the catalyst bed 222 and the inner 
cylindrical wall 212 into the central passage 224. The first part 170a is 
connected to one end of a second part 170b in the form of a spiral coil of 
tube disposed in the central passage 224 and extending axially thereof. 
The first part 170a is so positioned with respect to the reactor vessel 
200 that said end of the spiral coil of tube 170b is located adjacent to 
the downstream end of the central passage 224 in the vessel 200. The other 
end of the spiral coil of tube 170b is located near to the upstream end of 
the central passage 224 and connected to a third part 170c of the rich 
mixture supply pipe 170'. The third part 170c extends axially through the 
disc-like closure plate 216, radially outwardly through the 
circumferentially continuous passage 218 and the peripheral wall 202 of 
the reactor vessel 200 and is connected to the peripheral wall 164 of the 
pre-swirling chamber 162 as in the embodiment shown in FIG. 1. 
The rich air-fuel mixture produced by the carburetor 110 is heated by the 
heat produced in the reactor vessel 200, so that the fuel contained in the 
rich air-fuel mixture is effectively atomized before the rich air-fuel 
mixture is introduced into the burner 160. This improves the ignitability 
of the air-fuel mixture in the burner 160 with a resultant advantage that 
the partial oxidization of a part of the fuel due to imperfect combustion 
of the remainder of the fuel is more stably induced. In addition, because 
the spiral coil of tube 170b is disposed in the central passage 224, the 
spiral coil of tube 170b does not require any extra space and the entire 
system can be very compact. 
The burner 160, the reactor vessel 200 and the third part 170c of the rich 
mixture supply pipe 170' may be covered with layers of a heat insulating 
material to keep the interiors of them at elevated temperatures so that 
the rate and efficiency of the thermal decomposition reaction in the fuel 
reforming system can be improved. The delivery pipe 226 may be provided 
with a cooler for cooling the reformed gaseous mixture to a temperature 
appropriate for the introduction of the reformed gaseous mixture into the 
engine 10. The delivery pipe 226 may also be provided with a filter for 
removing any foreign particles, such as soot, from the reformed gaseous 
mixture. The flap valve 228 has been described and illustrated as being 
operatively connected to the engine throttle valve 34 but may 
alternatively be controlled by signals which represent engine operation 
parameters such as the engine speed, load on the engine and the 
composition of the engine exhaust gases. Moreover, a second carburetor 40 
may be installed in the intake pipe 30 between the air filter 32 and the 
throttle valve 34, as shown in FIG. 4, to produce a lean mixture of air 
and a fuel so that the lean air-fuel mixture is mixed in the mixing 
chamber 38 with the reformed gaseous mixture from the fuel reforming 
system 100 according to the present invention. The intake system shown in 
FIG. 4 is advantageous in that the emission of the harmful components of 
engine exhaust gases is reduced by the operation of the engine with a lean 
air-fuel mixture and, at the same time, the efficiency of charge to the 
engine is improved with resultant advantageous increase in the engine 
output. 
The engine 10 associated with the fuel reforming system 100 according to 
the present invention has been described and illustrated as being of 
conventional or ordinary type. However, the engine 10 may be of a 
stratified charge engine having a combustion chamber comprising a main 
combustion chamber and an auxiliary or sub-combustion chamber. In the case 
where the fuel reforming system of the present invention is associated 
with the second type of engine, the reformed gaseous mixture produced by 
the system of the invention may be fed into the auxiliary or 
sub-combustion chamber, while the main combustion chamber may be supplied 
with air alone or a lean air-fuel mixture, so that the reduction in the 
emission of harmful exhaust gas components, which reduction per se is a 
characteristic of the stratified charge engine, can be further 
facilitated.