Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
METHOD AN~ APPARATUS FOR
~ ON
BACKGROUND OF THE INVENTION
1. Technical Pield.
The present invention relates to the conversion of
liquid fuel to gaseous form and particularly to a method
and apparatus for producing a flow of combustlble
gaseous mixture of fuel and air by centrifugal action
~or use in a combustion apparatus, particularly in an
internal combustion engine.
2~ Backqround Art.
Nonuniform mixing of fuel and air and fuel condensation
in the intake passages of internal combustion engines
are known to increase fuel consumption and pollution.
Conventional venturi carburetors deliver liquid fuel in
a finely-divided spray, part of which tends to condense
upon cold intake passage walls. To assure that a
combustible mixture will reach the cylinders, the
carburetor must be adjusted to give a rich mixture
during engine warm up. In addition, the delivery of
fuel in the form of droplets makes it diff icult to
achieve completely uniform mixing with the intake air
- flowing through the carburetor~ -
Various proposals have been made for producing a
homoqeneous mixture of vaporized fuel and air by
rotational mixing, sometimes in combination with heating
or exposure to a gasifying catalyst, as in U.S. Patents
No. 2,351,072 of H. H. Schmidt, No. 4,053,013 of P.
Guba, No. 4,264,539 of R. E. Berg, and No. 3,946,717 of
England.
Schmidt introduces a fuel/air mixture from a carburetor
or other source into a stationary chamber containing a
disc-like rotor having vanes extending from the center
to the circumference on both sides of the disc. The
rotor disc subdivides the chamber into two halves, and
the mixture is introduced into each half through a
respective opening spaced from the axis of rotation
approximately two-thirds of the radius of the chamber.
The portions of the mixture entering these openings come
into engagement with the rotor vanes and are gi~en a
violent centrifugal whirling motion, causing them to be
thrown outwardly toward the periphery of the
partitioning disc and into contact with the side walls
of the chamber. The whirled mixture then leaves the
chamber through a tangential outlet passage.
Guba imparts a centrifugal force to a fuel/air mixture
supplied from a carburetor by passing the mixture
through a rotor comprising a plurality of tubular
members arranged in a circle and extending in directions
that are slightly skewed from parallel to the axis of
rotation. The tubular members are heated by a second
fluid passing in contact with the outside surfaces of
the tubes, so that the fuel/air mixture is pumped out of
the tubular members centrifugally in a preheated
condition.
Berg supplies fuel and air through separate coaxial
tubes to the center of a squirrel ca~e type of
.
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centrifugal fan that rotates in a stationary housing
which has a single off-center outlet~ England discloses
a fuel vaporizer having a flow-driven spinning bowl
suspended from a conical sieve fixed in an inlet passage
downstream from a carburetor. According to England,
liquid fuel droplets impact the bottom of the bowl, and
the captured liquid is centrifugally forced outward by
the spin of the bowl. The bowl sides are described as
directing the liquid flow to the backside of the sieve.
Since the bowl rim is at the maximum diameter of the
bowl, however, it would be inevitable that much of any
captured liquid fuel would be sprayed outward from the
rim of the spinning bowl into contact with the wall of
the intake passage.
SUMMARY OF T~E INVENTION
The applicant has discovered that, contrary to the
teachings of the above-mentioned patents, imparting a
strong rotational motion to a flow of air entraining
sprayed droplets of liquid fuel does not necessarily
improve the uniformity of mixing or promote the
vaporization of all the fuel. In fact, the centrifugal
forces acting on the rotating particles of the mixture
tend to cause the heavier fuel particles to separate
from the air and to condense on the surrounding
stationary wall of the mixing chamber or the intake
passage~ Thus, centrifugal mixing devices can even
aggravate the problem they are attempting to solve.
It is the principal object of the present invention to
provide a method and apparatus for converting a flow of
liquid fuel into essentially gaseous form by centxifugal
action and for uniformly mixing the gaseous fuel with a
flow of air for efficient burning in a combustion
~ apparatus.
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D ~
It is a further object of the invention to reduce the
rotational velocity of a centrifugally mixed flow of air
and fuel before the flowing mixture comes into contact
with any stationary peripheral wall, so as to minimize
5 centrifugal separation of ~he fuel from the air.
These and other objects are achieved by a method for
providing a gaseous mixture of fuel and air to a
combustion apparatus, and a device for performing the
method.
lO The method comprises:
delivering a flow of volatile liquid fuel to a fuel
chamber lGcated inside an intake passage of a combustion
apparatus, the fuel chamber having an axis of symmetry
coincldent with the axis of the intake passage and an
15 upstrèam-faclng surface extending transversely outward
to a circumferential edge spaced radially inward fr~om a
peripheral outer wall of the chamber, and the fuel being
delivered through an axial fuel conduit to flow onto the
fuel distribution surface;
20 rotating the fuel distribution surface and the
peripheral outer wall of the fuel mixing chamber about
said axis of symmetry at sufficient velocity to spread
the liquid fuel in a thin film across said fuel
distribution surface for promoting evaporation of the
25 fuel and to maintain by centrifugal force any liquid
fuel discharged from the circumferential edge of the
surface in contact with the peripheral outer wall until
the fuel evaporatesi and t
delivering a flow of air through the intake passage into
the chamber through an inlet opening on the upstream
side of the chamber and out of the charnber through an
outlet opening on the downstream side of the chamber,
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the inlet and outlet openings being located closer to
the axis of the chamber than the circumferential edge of
the upstream-facing fuel distribution surface, and the
peripheral outer wall extending from said inlet opening
5 to said outlet opening, such that the flow of air passes
over the fuel distribution surface, around the
circumferential edge thereof, and then inwardly toward
the axis of the chamber for thorough mixing with
evaporated fuel before lea~ing the chamber through said
10 outlet opening, and such that no liquid fuel is
-discharged through the outlet opening of the chamber.
Preferably, the method of the invention further
comprises directing the flow of air radially inward
around an annular baffle connected to the surrounding
15 outer wall of the chamber adjacent to the outlet opening
and extending in the upstream direction to terminate in
an edge spaced axially from the downstream side of said
transverse surface and radially inward from the
peripheral outer wall ~or assuring that no liquid fuel
20 is entrapped in the fuel/air mixture discharged through
the outlet opening of the rotating chamber.
The device of the invention comprises:
a housing having an intake passage with an upstream end
communicating with the atmosphere and a downstream end;
25 an enclosed fuel mixing chamber positioned centrally
within the intake passage, said fuel mixing chamber
having an axis of symmetry, axially spaced upstream and
downstream walls extending transversely to said axis, t
each of said upstream and downstream walls having an
30 opening therethrough for communicating the intake
passage with the interior of the fuel mixing chamber, a
fuel distri~ution member disposed between the upstream
and downstream walls, said member having a surface
facing the upstream wall and bounded by a peripheral
edge, and a peripheral wall encircling said fuel
distribution member in radially spaced relation to the
peripheral edge of said member and connecting the
5 upstream wall with the downstream wall;
means for supporting the fuel mixing chamber for
rotation about its axis of symme~ry within the intake
passage;
a conduit for delivering liquid fuel to said surface of
10 the fuel distribution member of the fuel mixing chamber
via said supporting means; and
means for rotating the fuel mixing chamber about said
axis to force the fuel centrifugally across said surface
in a thin film for promoting evaporation of the fuel and
15 to maintain by centrifuqal force any liquid fuel
discharged from the peripheral edge of said sur~ace in
contact with the peripheral wall until the fuel
evaporates and mixes with a flow of air through the fuel
mixing chamber via said openings in the upstream and
20 downstream walls.
Additional features and advantages of the invention are
described below in connection with the preferred
embodiment shown in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
25 The invention will be more clearly understood by
reference to the accompanying drawings and the t
associated detailed description.
FIG. l is an exploded perspective view of a device
according to the invention.
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FIG. 2 is a simplified elevation view in cross section
of the device cf FIG. lo
DETAILED DESCRIPTION OF THE PREFEP~RED EMBODIMENTS
With reference to FIGS. 1 and 2, one embodiment of a
device according to the invention has an intake housing
10 which is adapted for mounting on an intake manifold
of an internal combustion engine in place of a
conventional carburetor. The housing contains a
throttle valve 11 positioned below a fuel/air mixing
apparatus 12. The mixing apparatus includes an electric
motor 13 centrally positioned by struts 14 in the
housing and a fuel mixing chamber 15 fixed to the motor
shaft 16.
The fuel mixing chamber is assembled from a lower cup-
15 ~like shell 17 and an upper cup-like shell 18~ which is
inverted and fastened to the lower shell by screws 19 to
form a leak-tight joint.
The lower shell 17 is formed with a raised central
hollow boss 20 having a flat top 21 on which is mounted
a flat disc 22 by suitable means such as screws 23. The
flat top of the boss preferably is formed with a raised
cylindrical stud 24 whioh mates with a hole 25 in the
disc to center the disc in the chamber. The base of the
lower shell 18 serves as a downstream wall 26 of the
~uel mixing chamber, this wall having an outlet opening
27 coaxial with and closely adjacent to the central
boss 20. The outlet opening may be formed by a
plurality of holes 28 (for example, twelve) arranged in
a circle around the boss. A baffle in the form of an
annular wall 29 surrounds the outlet openingO The lower
end of the ~affle wall joins the downstream wall of the
lower shell, and the upper end terminates in a
circumferential edge 30 that is spaced axially from the
downstream face 31 of the disc 2Z and radially inward
from the peripheral edge 32 of the disc.
The upper shell 16 has a flat top that serves as an
upstream wall 33 of the fuel mixing chamber. A
5 counterbored hole 34 in the center of the upstream wall
carries a ball bearing 35 in the bore of which is fitted
an axial fuel conduit in the form of a tube 36 having a
head 37 drilled with passages 38 for delivering streams
of liquid fuel onto the upstream-facing surface 39 of
10 the disc 22. An inlet opening 40 through the upstream
wall of the chamber coaxially surrounds the fuel
conduit. As in the case of the outlet opening 27, the
inlet opening 40 may be constituted by a plurality of
holes 41 arranged in a circle. The inlet and outlet
15 holes may be circular or any other convenient shape; in
each case it is desirable that the total area of the
inlet and ~penings be no smaller than the flow area
provided past throttle ]1 when it is fully opened.
The upstream and downstream walls of the fuel mixing
20 chamber are joined to respective side walls 42 and 43,
which together constitute a peripheral outer wall 44 of
the fu~l mixing chamber. Each of the side walls 42 and
43 is frusto-conical, so that the inner diameter of the
peripheral wall of the chamber increases from the
25 junctions of the respective side walls with the upstream
and downstream walls to a maximum value at the junction
of the two shells intermediate the upstream and
downstream walls. Preferably the region of maximum
diameter lies below (i~e., downstream~ of a plane
30 defined by the upstream edge of the baffle 29, for t
reasons that will be explained below in connection with
the description of the operation of the device.
The assembly of the device is completed by a cover plate
45 that is fastened to the top of the housing by screws
46. The center of the cover plate is provided with a
hollow block 47 which serves as a distributing connector
for a fue] line 48 from a fuel metering valve 49, as
well as for a fuel line 50 from an idling adjustment
valve 51 (see FIG. 3). A central bore 52 extending
through the upstream wall and the bottom of the hollow
block slidingly receives the upper end of the fuel
conduit tube 36, the connection being sealed by an O-
ring 53.
As shown in FI~. 1, the cover plate 45 has an annular
opening 54 surrounding the hollow block 47 to permit air
to enter the upstream end of the housing. Because the
clearance between the peripheral outer wall of the fuel
~ixing chamber and the wall of the intake passage
through the housing is only enough to avoid contact
~preferably about 1/16th inch), essentially all of the
air flow will enter the inlet opening in the upstream
wall of the fuel mixing chamber and will exit from the
outlet opening in the downstream wall of the chamber.
The fuel metering valve 49 is a needle-type of valve
having a valve rod 55 reciprocally mounted in a valve
housing 56. The upper end of the rod comprises a needle
valve which coacts with a seat 57~ The axial position
of the seat is adjustable by means of a screw 58 at the
top of the valve housing. The lower end of valve rod
55 is provided with a row of teeth to form a rack 59.
Valve housing 56 is mounted on the side of intake
housing 10 so that the axis of valve rod 55 is
perpendicular to a plane containing the axis of a shaft
60 carrying the butterfly valve 11. In FIG. 2 this
shaft is turned 90 degrees for clarity in showing the
butterfly throttle valve 11.
The other end of butterfly valve shaft 60 may be
connected by a conventional crank arrangement to an
~ 3~
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accelerator pedal. It is apparent that the rack and
pinion combination provides a direct conversion of
angular rotation of the throttle valve to linear
movement of the fuel needle valve 55. The previously
mentioned valve seat 57 mounted on the lower end of
screw 58 is adjustable axially by rotation of the screw
in an internally threaded sleeve 61 having also an
externally threaded body screwed into the upper end of
the valve housing. This axial adjustment of the valve
seat provides a simple means to set the opening of the
fuel metering valve in relation to the openlng of the
throttle valve. If desired, thls adjustment can be used
to obtain a proper idling mixture, and the separate
idling adjustment valve 51 can be eliminated.
As shown in FIG. 2, the fuel/air mixing device 10 is
intended to be connected to a combustion apparatus, as
by mounting on the intake manifold of an internal
combustion engine 62 in place of a conventional
carburetor. Liquid fuel, such as gasoline, from a fuel
tank 63 is fed through a supply line 64 to a fuel pump
65. The pump delivers fuel under pressure to inlet port
66 of the fuel metering valve via lines 67 and 68. An
amount of fuel determined by the opening of the needle
valve 55 flows from outlet port 69 via line 48 to the
distribution block 47. A preset amount of fuel may also
be delivered from line 68 via line 70 to the idling
adjustment valve 51, if such a separate valve is used.
As shown, valve 51 may be a conventional, manually
adjustable needle valve.
It has been found that fuel delivery by the device is
sensitive to the delivery pressure from the fuel pump.
The optimum pressure range is 1-1/2 to 2 psi, but
mechanical fuel pumps, for examplel may have an output
pressure that varies from 4 to 6 psi. A simple yet
effective way to reduce pressure fluctuations and to
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obtain the optimum pre~sure at the inlet of the fuel
me~ering valve is to provide an adju~ta~le bypa~s valve
71 in the supply llne. Valve 71 ha~ aQ inlet port 72
connected to fuel line 67, an outlet port 73 connected
to fuel line 68, and a bypass port 74 connected to a
fuel return line 75 leading back to the supply tank.
Inle~ port ~2 communica~e~ internally wi~h outlet port
73 via a valve chamber 76 ~urrounding a needle valve 77.
The needle valve has a threaded stem 78 to per~.it
adjustment of the spacing of the valve with respect to
it~ seat 79~ the seat leadin~ to ~he bypas~ port 74. A~
the valve is opened~ a greater portion o the output
from the fuel pump i~ bypassed and returned to the
~upply tank, causing the supply pressure in the valve
chamber to drop and pres~ure variations to diminish~
a re~ult, the pressure delivered to the fuel metering
valve can be maintained substantially constant at an
optimum value under all operating conditions of the
engine with only a single presetting adjust~ent of the
bypass needle valve.
In addition to connection to a fuel supply, the mixing
device 10 also requires connection to an electric power
source, such a~ a battery (not shown), through an
ignition switch (not shown) for operatin~ the electric
motor 13~ It i~ also de~irable to provide an
electrically a~tuated hut of valve (not shown3 in the
fuel ~upply line, particularly if the engine is equipped
with an electric fuel pumpO The electric valve should
be controlled by a switch re~pon~ive ~o engine
operation, such as a vacuum switch actuated by intake
manifold vacuum~ so that the fuel supply will be
po31tively shut off if the engine ~talls~ to prevent
flooding. ~n electric control arrangement for a fuel
~upply ~hut off valYe is more fully described in the
applicant's U.S. Patent No~ 4,430,095 issued on
7 February 1984.
~12-
The operation of the device should be apparent rom the
oregoing description, but it will be briefly de~cribed
for ake of completeness~ When the en~ine ignition
s~itch is turned on, the electric motor 13 will be
energized, causing the ~uel mixing chamber to start to
spinO Preferably~ the motor spins the chamber at a
speed on the order of 10,000 rpm. Clo~ing of the
starter swltch to crank the enqine will create
3uffieient qacuum in the intake manifold to a~tuate the
vacuum switch nd open the fuel ~upply line. Fue-l will
then flow through the idle adjustment valve 51, or
through the fuel metering valve 49 if there i~ no
~eparate idle adjustment valve, to the distribution
block 47, then down through tube 36 and passage 38 in
head 37 to flow onto the spinning disc 22.
When the liquid fuel contaets the upper surface 39 of
the d;sc, it spread~ rapidly outward in a thin film
under the influence of centrifugal forces induced by the
di3c~ The thin film promotes evaporation of the fuel
from the surface of the disc. Any unevaporated liguid
that reaches the edge of the disc is flung outward into
contact with the peripheral outer wall 44 of th~
spinning chamber. Since ~11 part3 of ~he mixing chamber
~except the stationary fuel supply head 37) rotate at
the ~ame angular velocity, liquid fuel cont~cting any
internal surface of the chamber will be subjected to ~
centrifugal force that increase~ with di$tance from the
axi~ of rotation. Thus, any unevaporated fuel in the
chamber will tend to end up at the region of m~ximum
circumference of the peripheral outer wall of the
chamber. Th~re, the high surface speed of the spinning
wall will spread the fuel into an extremely thin layer
which will rapidly evaporateO
Meanwhile, air from the surrounding atmosphere will be
. .
b. ~
drawn into the cranked engine through the annular
opening 54 in the cover plate of the housing, then into
the intlet openlng 40 of the chamber, over and around the
edges of the disc 22 and the baffle 29, and out of the
chamber through the outlet opening 27, to flow past the
throttle valve 11 into the intake manifold. A strong
turbulence i5 imparted to the air flowing through the
inlet holes 41. This turbulence enhances the mixing of
the air with evaporated fuel Erom the surface of the
disc.
The incoming air also is given a circular rotation, or
swirl, as it passes through the inlet holes and then
flows in contact with the spinning surfaces of the
chamber. The swirl motion, as well as the generally
outward flow of the air over the upper surface of disc
~2 and the abrupt change of direction of flow around the
edge of the disc, imparts an outward momentum to any
particles of liquid fuel that may be entrained in the
air flow, either from the streams leaving the passages
38 or ~rom droplets splashed up from the streams when
they strike the surface of the disc.
As a resul~ of the outward momentum, the entrained
liquid particles will be thrown against the peripheral
outer wall of the chamber as the mixture flows around
the edge of the disc, and the high circumferential speed
of the peripheral wall will hold the separated liquid
until it completely evaporates. It should be noted,
moreover, that the design of the fuel mixing device
minimizes liquid fuel entrainment in the first place, by
bringing the air into the chamber radially outward from
the fuel and by placin~ the supply head close to the
spinning disc.
After the mixture of air and completely vaporized fuel
flows around the edge of the disc 22, as shown by arrows
80, it is guided into a toroidal circulation, as shown
by arrows 81, by the converging lo~er peripheral wall 43
and the outer wall of the baffle 29. This circulation
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tends to separate any remaining liquid fuel particles
from the stream of air and vaporized fuel before the dry
mixture flows over the edge of the baffle (arrows 82)
and through the outlet holes 28. Liquid particles that
strike the baffle or the bottom surface of the chamber
will tend to move under centrifugal force toward the
region of maximum diameter. In the disclosed
embodiment, this region is located axially downstream of
the edge of the baffle. This location removes the
liquid film from the direct path of air flow over the
baffle, thereby further minimizing the possibility of
liquid particles becoming entrained in the flow of air.
Additional turbulence is imported to the mixture as it
flows through the outlet holes, but the circular
momentum of the outflowing mixture is reduced by
looating the outlet holes as close as practical to the
axis of rotation. Thus, the mixture leaving the chamber
is thoroughly and turbulently mixed, but it does not
have a high centrifugal component. That is, the flow
does not have a high rotational ~elocity because it
leaves the mixing chamber through an outlet opening
having a relatively small diameter. As a result, any
possible tendency for the vaporized fuel to separate
from the air and condense on the walls of the intake
passage is greatly reduced7
Most importantly, however, the design of ~he mixing
chamber assures that all liquid fuel particles are
maintained in contact with a rapidly rotating surface
until the liquid is completely vaporiæed to particles of
essentially molecular dimensions. The liquid fuel is
thus converted into a dry gaseous vapor. The vapor is
thoroughly mixed with the turbulent air stream before
the mixture enters the intake passage, and the potential
for subsequent condensation of any fuel prior to entry
` 35 of the mixture into a combustion chamber of an engine is
. ~
negligible.
Althou~h the invention has been described in connection
with its application to internal combustion engimes, as
a replacement for a conventional carburetor, the method
and apparatus is also applicable for use wlth other
types of combustion apparatusr such as furnaces and
boilers. The essentially complete evapor~tion of the
liquid fuel and the subsequent turbulent mixing of the
dry vapor with air produce a highly uniform combustible
10 -mixture that is substantially immune to recondensation
of the fuel during its flow to the combustion chamber of
the apparatus.
