Fuel reforming system

A fuel reforming system for an internal combustion engine comprises a fuel circuit connected at its downstream end to the engine and including a carburetor for producing a rich air-fuel mixture and a fuel reforming reactor vessel containing a catalyst for facilitating a catalytic reformation of the mixture into a reformed gaseous mixture rich with free hydrogen. The carburetor is provided with a primary air intake passage with a venturi into which air and fuel are fed to produce a rich air-fuel mixture. The carburetor is also provided with a secondary air intake passage bypassing the venturi and connected to the fuel circuit downstream of the venturi. A valve is provided on the carburetor to control the cross-sectional area of the secondary air intake passage in accordance with the temperature in the engine or the reactor vessel, by the carburetor is adjusted according to the engine or reactor vessel temperature.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a system for converting a mixture of air 
and a fuel into a reformed gaseous mixture rich with free hydrogen and 
feeding the reformed gaseous mixture into an internal combustion engine. 
2. Description of the Prior Art 
In an attempt to reduce the emission of harmful components of engine 
exhaust gases or improve the fuel consumption of internal combustion 
engines, there has been proposed an internal combustion engine equipped 
with a fuel reforming system designed to convert a mixture of air and a 
fuel, such as hydrocarbon fuels, alcohols, aldehydes, ethers or a mixture 
of them, into a reformed gaseous mixture rich with free hydrogen and feed 
the reformed gaseous mixture into the engine, as disclosed in U.S. Pat. 
No. 3,908,606 issued Sept. 30, 1975 to Eiji Toyoda et al. There has also 
been proposed a fuel reforming system for an internal combustion engine 
which is operative to convert a mixture of air, a fuel, such as ones 
referred to above, and steam (or water) into a reformed gaseous mixture 
rich with free hydrogen and then introduce the reformed mixture into the 
engine. The prior art systems include reactor vessels each containing a 
catalyst for facilitating a fuel reforming catalytic reaction. When or 
just after the engine is cold-started, the catalyst is at a low 
temperature and thus incapable of sufficiently facilitate the fuel 
reforming reaction. 
The applicants' co-pending earlier application Ser. No. 641,603 filed Dec. 
17, 1975 discloses a fuel reforming system for an internal combustion 
engine, in which a mixture of air and methanol is subjected to a catalytic 
reformation and converted into a reformed gaseous mixture rich with free 
hydrogen. The reformed mixture is then fed into the engine together with 
another mixture of air and a hydrocarbon fuel. The disclosure in the 
co-pending earlier application referred to is incorporated herein by 
reference. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved fuel 
reforming system for converting a mixture of air and a fuel into a 
reformed gaseous mixture rich with free hydrogen and feeding the thus 
reformed gaseous mixture into an internal combustion engine. 
The fuel reforming system according to the present invention includes a 
fuel circuit which includes a carburetor for producing a mixture of air 
and a fuel, such as methanol, and a fuel reforming reactor vessel 
containing therein a catalyst for facilitating a catalytic fuel reforming 
reaction therein. The fuel circuit has its downstream end connected to an 
associated internal combustion engine so that a reformed gaseous mixture 
produced in the fuel reforming reactor vessel is introduced into the 
engine. An ignition means is provided in the fuel circuit between the 
carburetor and the reactor vessel and may be operated, when required, to 
ignite the air-fuel mixture produced by the carburetor. The carburetor is 
provided with a primary air intake passage with a venturi therein. The 
fuel is fed into the venturi so that the fuel is mixed with air passing 
through the venturi to form the air-fuel mixture. The carburetor is also 
provided with a secondary air intake passage which bypasses the venturi 
and is connected to the fuel circuit downstream of the venturi. 
Advantageously, means are provided on the carburetor and operative in 
response to the increase in the temperature in the engine or the reactor 
vessel to decrease the cross-sectional area of the secondary air intake 
passage to vary the air-fuel ratio of the mixture produced by the 
carburetor. Preferred arrangement is such that, when the temperature is 
increased, the air-fuel ratio is decreased (i.e., the air-fuel mixture is 
enriched). 
The fuel to be reformed may preferably be methanol, but another kind of 
fuel, such as a hydrocarbon fuel, may also be used with the system of the 
present invention. 
The above and other objects, features and advantages of the present 
invention will be made apparent by the following description with 
reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIGS. 1A, 1B and 2, a first embodiment of a fuel reforming 
system according to the present invention is generally designated by 100 
and adapted to be used with an internal combustion engine which is 
generally indicated by 10 and shown as being a conventional four cycle 
reciprocated piston engine which comprises a cylinder block 12 and a 
cylinder head 14 mounted on the top of the cylinder block 12. The cylinder 
block 12 defines therein cylinders 16 only one of which is shown. A piston 
18 is reciprocally received in the cylinder 16 to cooperate with the 
cylinder 16 and the bottom surface of the cylinder head 14 to define a 
combustion chamber 20. The cylinder head 14 is formed therein with an 
intake port 22 and an exhaust port (not shown). An intake valve 24 is 
reciprocally mounted on the cylinder head 14 so that a valve head 26 of 
the intake valve is operative to open and close the intake port 22 in 
conventional manner. A spark plug 28 is mounted on the cylinder head 14 so 
that electrodes of the spark plug are exposed to the combustion chamber 
20. 
The intake port 22 is connected at its upstream end with an intake pipe 27 
which in turn is connected at its upstream end with a primary fuel circuit 
comprising a primary carburetor 30 having a venturi 32 for producing a 
lean mixture of air and a hydrocarbon fuel, such as gasoline. A throttle 
valve 34 is provided in the primary fuel circuit downstream of the venturi 
32 for controlling the primary fuel supply into the respective combustion 
chambers 20 in known manner. An air cleaner 36 having an air filter 38 
therein is mounted on the top of the primary carburetor 30. Exhaust gases 
from respective exhaust ports (not shown) are gathered into an exhaust gas 
gathering portion 40. 
The fuel reforming system 100 provides a secondary fuel circuit for the 
engine 10 and designed to be operative to convert or reform a mixture of 
air and methanol into a reformed gaseous mixture rich with free hydrogen 
and feed the reformed gaseous mixture into the engine 10. For this 
purpose, the fuel reforming system 100 includes a secondary carburetor 102 
for producing a mixture of air and methanol, a rotary throttle valve 104 
operatively connected to the primary throttle valve 34 by a conventional 
link mechanism (not shown), a pipe 106 connected at its upstream end to 
the downstream side of the throttle valve 104, a spark plug 108 mounted on 
the upper side of the pipe 106, a fuel reforming, catalytic reactor vessel 
110 connected to the downstream end of the pipe 106, and a second pipe 112 
extending between the reactor vessel 110 and the primary fuel circuit at a 
point between the primary throttle valve 34 and the intake pipe 28. 
The secondary carburetor 102 is of constant vacuum, horizontal draft type 
and comprises a carburetor housing 120 which defines therein a float 
chamber 122 on the under side of a primary air intake passage 124 and a 
space on the upper side of the air intake passage 124. A diaphragm 126 
extends substantially horizontally across the space to divide the same 
into a first or upper pressure chamber 128 and a second or lower pressure 
chamber 130. A compression coil spring 132 is disposed in the first 
pressure chamber 128 to downwardly bias the diaphragm 126. A suction 
piston 134 is mounted on the under surface of the diaphragm 126 and 
slidably extends through the carburetor 102 and across the air intake 
passage 124 toward the float chamber 122. A needle 136 is also mounted on 
the diaphragm 126 coaxially with the suction piston 134 and reciprocally 
extends into an opening of a nozzle 148 extending from the air intake 
passage 124 into the float chamber 122 and terminating in an open bottomed 
end positioned adjacent to the bottom of the float chamber 122. The first 
chamber 128 is communicated by a passage 128a with the air intake passage 
124 downstream of the suction piston 134, while the second chamber 130 is 
communicated with the atmosphere by a passage 130a. The suction piston 134 
is arranged such that the differential pressure in the air intake passage 
124 across the suction piston 134 is kept at a constant value which is 
determined by the load on the diaphragm 126 exerted by the spring 132 
thereto. In other words, the suction piston 134 cooperates with the air 
intake passage 124 to define a variable venturi the opening of which is 
determined by the air flow through the passage 124. The fuel is fed from 
the float chamber 122 through the nozzle 148 into the venturi so that a 
mixture of air and the fuel is produced. The float chamber 122 is vented 
by an air vent 150 and can be drained by removing a blind plug 152 from 
the bottom of the float chamber. The interior of the nozzle 148 is 
communicated with the second pressure chamber 130 by an air bleeder 154. A 
secondary air intake passage 160 extends through the secondary carburetor 
102 and bypasses the venturi and is opened to the air intake passage 124 
downstream of the venturi, i.e., at a point between the suction piston 134 
and the rotary throttle valve 104. 
The secondary carburetor 102 is provided with an air-methanol ratio 
adjusting means 162 operative to control the air flow through the bypass 
passage 160 in accordance with the temperature in the reactor vessel 110. 
Details of the air-methanol ratio adjusting means 162 will be described 
later. 
The spark plug 108 is operated by a conventional ignition system 109 when 
required, i.e., for example when the reactor vessel 110 is at a low 
temperature, to ignite and burn a part of air-methanol mixture produced by 
the secondary carburetor 102. 
A flame arrester 105 is provided in the pipe 106 between the rotary 
throttle valve 104 and the spark plug 108 to guard the secondary 
carburetor 102 against flame or flames produced by the combustion of the 
air-methanol mixture caused by the ignition thereof by the spark plug 108. 
The flame arrester 105 may be a honeycomb structure of ceramic material or 
made of a stack of several sheets of metal screens. 
The fuel reforming, catalytic reactor vessel 110 is connected to the 
exhaust gas gathering portion 40 of the exhaust manifold and contains a 
layer 170 of catalyst particles. The layer 170 extends substantially 
across the entire cross-sectional area of the vessel 110. The air-methanol 
mixture produced by the secondary carburetor 102 flows through the pipe 
106 into the layer 170 of the catalyst particles. A plurality of axial 
passages 172 extend through the catalyst particle layer 170 so that 
exhaust gases from the engine 10 flow from the exhaust gas gathering 
portion 40 into and through the axial passages 172 in heat exchanging 
relationship with the catalyst particle layer 170 and the air-methanol 
mixture flowing therethrough. Thus, the catalyst particles are heated to a 
temperature sufficient for the catalytic reformation or conversion of the 
air-methanol mixture into a reformed gaseous mixture rich with free 
hydrogen, which is then supplied through the pipe 112 into the primary 
fuel circuit and introduced into the engine 10 together with a lean 
air-gasoline mixture from the primary carburetor 30. The engine exhaust 
gases flow from the vessel 110 into and through an exhaust pipe 42 and are 
then exhausted into the atmosphere. 
The construction and operation of the fuel reforming, catalytic reactor 
vessel 110 may be similar to those disclosed in U.S. patent application 
Ser. No. 641,603 referred to above. Preferred examples of the catalyst 
particles which form the layer 170 are pellets of alumina coated with a 
metal such as nickel or copper. 
The air-methanol ratio adjusting means 162 mentioned above include an air 
conduit 182 interconnecting the interior of the air cleaner 36 and one end 
of a temperature detector in the form of a U-shaped tube 184 of a metal 
mounted on the reactor vessel 110 with the looped end of the tube 
extending into the layer 170 of the catalyst particles in the vessel 110 
so that the air from the air cleaner 36 flows through the temperature 
detector 184 in heat-exchange relationship with the catalyst particles. 
The air from the air cleaner 36 is heated when the air flows through the 
temperature detector 184. The heated air then flows through a second air 
conduit 186 into a temperature measuring chamber 188 defined by a housing 
200, from which chamber the air is returned through a third air conduit 
202 into the primary fuel circuit of the engine 10 downstream of the 
primary throttle valve 34. The housing 200 is mounted on the carburetor 
housing 120. The temperature measuring chamber 188 is defined between the 
housing 200 and a support plate 204 extending across the interior of the 
housing 200. The support plate 204 supports an expansible means 206 which 
comprises a cylinder member 208 rigidly mounted on the support plate 204 
by means of a stay 210, a piston reciprocally received within the cylinder 
member 208, a mass of heat expansible material 214 filled in the space 
defined between the cylinder member 208 and the piston 212, and a coil 
spring 216 urging the piston against the heat expansible material 214, as 
shown in FIG. 2. The heat expansible material may be an inorganic compound 
such as MgO, a metal such as Pb or an alloyed metal such as solder 
(Pb-Sn). In the case where the second air conduit 186 is so long that the 
air heated during its passage through the temperature detector 184 is 
substantially cooled before the air reaches the temperature measuring 
chamber 188, the heat expansible material may preferably be paraffin or a 
wax. 
Thus, the piston 212 will be moved downwardly when the heat expansible 
material 214 is expanded by the heated air supplied to the temperature 
measuring chamber 188. The piston 212 has a piston rod 218 which is in 
engagement with the upper surface of a piston-type valve 220 which is 
slidably received in a bore formed in the secondary carburetor 102 and has 
a lower valve part extending into the secondary air intake or bypass 
passage 160 in the carburetor 102. It will be appreciated that, when the 
heat expansible material 214 is expanded, the valve part of the 
piston-type valve 220 is moved downwardly to decrease the sectional area 
of the bypass passage 160 to thereby decrease the air flow therethrough. A 
compression coil spring 222 is provided to always bias the piston-type 
valve 220 upwardly. 
The operation of the described embodiment will be described. At the time 
of, or just after the cold-starting of the engine 10, the catalyst 
particle layer 170 in the reactor vessel 110 is at a low temperature, so 
that the air flowing through the temperature detector 184 enters the 
temperature measuring chamber 188 at a low temperature. Thus, the heat 
expansible material 214 in the expansible means 206 is in almost 
non-expanded state, so that the lower valve part of the piston-type valve 
220 is in a position to substantially fully open the bypass passage 160. 
For this reason, a relatively large amount of secondary air is supplied 
through the bypass passage 160 to a rich air-methanol mixture produced by 
the air passing through the primary air intake passage 124 and methanol 
jetted from the nozzle 148 into the air. Thus, the air-methanol mixture is 
diluted by the secondary air to an air-methanol ratio which is larger than 
normal air-methanol ratio obtained during normal operation of the engine, 
i.e., after the engine is appropriately warmed. The larger air-methanol 
ratio, however, is much smaller than the stoichiometric air-methanol ratio 
of 6.5. The arrangement is such that the air-methanol ratio after the rich 
air-methanol mixture is diluted by the secondary air from the bypass 
passage 160 ranges from 1.6 to 3.0 when the reactor vessel 110 is at a low 
temperature. Because the air-methanol ratio is relatively large at the 
point of the spark plug 108, at least a part of the air-methanol mixture 
can be stably ignited by the spark plug 108 and burnt to produce heat of 
reaction, whereby a fuel reforming reaction can surely be induced in the 
reactor vessel 110 to reliably produce a reformed gaseous mixture rich 
with free hydrogen even when the reactor vessel 110 is at the low 
temperature. 
By a continued operation of the engine, the layer 170 of the catalyst 
particles in the reactor vessel 110 is heated to an elevated temperature 
with the result that the air passing through the temperature detector 184 
is also heated. The heated air is introduced into the temperature 
measuring chamber 188, so that the heat expansible material 214 of the 
heat expansible means 216 is expanded with resultant increase in the load 
on the compression spring 222, which causes downward displacement of the 
piston-type valve 200 into the bypass passage 160, whereby the 
cross-sectional area of the bypass passage 160 and thus the air flow 
therethrough are decreased. For the reason, the air-methanol ratio of the 
air-methanol mixture produced by the secondary carburetor 102 is gradually 
decreased. The secondary carburetor 102 is arranged such that, when the 
layer 170 of the catalyst particles in the reactor vessel 110 is heated to 
a temperature high enough to induce a fuel reforming reaction (i.e., a 
temperature of about 350.degree. C. in the case of Ni or Cu catalyst 
particles), the air-methanol ratio of the air-methanol mixture produced 
falls within a range of from 0.3 to 1.5. An air-methanol mixture of as 
small air-methanol ratio as possible is preferred in the view point of 
avoiding loss of chemical energy but should fall within a range of 
air-methanol ratio where the mixture does not produce a large amount of 
soot when the mixture is subjected to the catalytic reforming reaction. 
As such, the air-methanol mixture is converted by the catalytic action of 
the catalyst particles into a reformed gaseous mixture rich with free 
hydrogen. 
The reformed gaseous mixture flows through the pipe 112 into the intake 
pipe 28 of the engine 10, in which the mixture is mixed with a lean 
air-hydrocarbon fuel mixture from the primary carburetor 30 to form a 
composite mixture which is supplied into the combustion chamber 20. The 
existence of free hydrogen in the composite mixture assures a reliable 
combustion of a very lean air-fuel mixture in the combustion chamber and a 
reduction in the emission of harmful components of the engine exhaust 
gases. It will be also apparent from the above description that the 
air-methanol mixture is converted into the reformed gaseous mixture even 
at the time the engine is operating at a low temperature, whereby the 
engine can be smoothly operated even from the time the engine is at a low 
temperature. 
The air-methanol ratio adjusting means 162 may also be operable by another 
high temperature fluid, such as engine exhaust gas, reformed gaseous 
mixture or engine cooling water. FIG. 3 illustrates a modified heat 
expansible means 206a which is particularly designed to be operable by 
engine exhaust gas and comprises a rod member 214a of a heat resistant 
metal extending through a temperature measuring chamber 188a defined in a 
housing 208a which is rigidly secured or connected to a support plate 204a 
secured to the carburetor housing 120. The rod member 124a is secured at 
its top end to the housing 208a and has a lower end portion 218a which is 
freely movable through an opening in the support plate 204a. The lower end 
extremity of the rod member 214a may be in abutment contact with the top 
of the piston-type valve 220 so that the temperature variation in the 
engine exhaust gas can be directly converted into displacement of the 
valve 220 for the control of the cross-sectional area of the bypass 
passage 160, as in the embodiment described with reference to FIGS. 1A, 1B 
and 2. 
FIG. 4 illustrates a further modification of the air-methanol ratio 
adjusting means generally designated by 162b, in which the temperature in 
the fuel reforming reactor vessel 110 is electrically detected to control 
the cross-sectional area of the bypass passage 160. For this purpose, the 
modified air-methanol ratio adjusting means 162b includes an electric 
temperature detector 184b in the form of a conventional thermistor or a 
thermocouple which is mounted on the reactor vessel 110 to detect the 
temperature therein and emit an electrical signal representing the 
detected temperature. The electrical temperature signal is supplied to a 
controlling circuit 230 which is operative to compare the signal with a 
reference signal and decide as to whether or not the temperature in the 
reactor vessel 110 is high enough to achieve the catalytic reformation of 
the air-methanol mixture into the required reformed gaseous mixture. The 
controlling circuit 230 is electrically connected by a line 186b to an 
electromagnetic coil 214b mounted in a housing 200b which is secured to 
the carburetor housing 120. A core 212b is movably disposed within the 
coil 214b and connected by a rod 218b to a piston-type valve 220b which is 
adapted to be moved into and out of the bypass passage 160 in the 
secondary carburetor 102. A compression coil spring 222b extends around 
the rod 218b between the valve 220b and a support plate or spring retainer 
plate 204b secured to the carburetor housing 120, the rod 218b slidably 
extending through the spring retainer plate 204b. The arrangement is such 
that the electromagnetic coil 214b is energized by an electric current 
from the controlling circuit 230 during normal operation of the engine and 
deenergized when the temperature signal received by the controlling 
circuit 230 indicates that the temperature in the reactor vessel 110 is 
not high enough for the intended catalytic reformation of the air-methanol 
mixture in the vessel. The air-methanol ratio adjusting means 162b 
discussed above will be operative in a manner substantially similar, but 
not exactly similar, to that of the preceding embodiments. In the 
embodiment discussed with reference to FIG. 4, the electromagnetic coil 
214b is energized and deenergized according to whether the temperature in 
the layer 170 of the catalyst particles in the reactor vessel 110 exceeds 
the predetermined temperature or not. However, the controlling circuit 230 
may be modified such that its output gradually and continuously varies in 
proportion to the variation in the temperature within the reactor vessel 
110 so that the air-methanol ratio adjusting means 162b is operative in an 
exactly similar manner to that of the preceding embodiments. 
Embodiments of the invention have been described and illustrated as being 
used with a conventional, spark-ignition internal combustion engine. 
However, it will be apparent to those skilled in the art that the fuel 
reforming system according to the present invention can also be used with 
a torch-ignition internal combustion engine having an auxiliary combustion 
chamber. In this instance, the reformed gaseous mixture may effectively be 
fed into the auxiliary combustion chamber for ignition and combustion by a 
spark plug, while a lean mixture of air and a hydrocarbon fuel may be 
supplied to a main combustion chamber of the engine for the ignition and 
combustion by a torch jet or jets produced by the combustion of the 
reformed gaseous mixture. 
It will also be apparent to those in the art that the constant vacuum, 
horizontal draft type secondary carburetor 102 employed in the described 
embodiments of the present invention may be replaced by a conventional 
down-draft type carburetor, which provides substantially similar results.