[0001] The p resent invention relates to fuel delivery in a n internal combustion engine.
More particularly, a method and apparatus according to the invention provides at least
one heated capillary flow passage for vaporizing fuel supplied to an internal combustion
engine.
[0002] A variety of systems has been devised to supply fine liquid fuel droplets and air
to internal combustion engines. These systems either supply fuel directly into the
combustion chamber (direct injection) or utilize a carburetor or fuel injector(s)
to supply the mixture through an intake manifold into a combustion chamber (indirect
injection). In currently employed systems, the fuel-air mixture is produced by atomizing
a liquid fuel and supplying it as fine droplets into an air stream.
[0003] In conventional spark-ignited engines employing port-fuel injection, the injected
fuel is vaporized by directing the liquid fuel droplets at hot components in the intake
port or manifold, under normal operating conditions. The liquid fuel films on the
surfaces of the h ot components and is subsequently vaporized. The mixture of vaporized
fuel and intake air is then drawn into the cylinder by the pressure differential created
as the intake valve opens and the piston moves towards bottom dead center. To ensure
a degree of control that is compatible with modern engines, this vaporizing technique
is typically optimized to occur in less than one engine cycle.
[0004] Under most engine operating conditions, the temperature of the intake components
is sufficient to rapidly vaporize the impinging liquid fuel droplets. However, under
conditions such as cold-start and warm-up, the fuel is not vaporized through impingement
on the relatively cold engine components. Instead, engine operation under these conditions
is ensured by supplying excess fuel such that a sufficient fraction evaporates through
heat and mass transfer as it travels through the air prior to impinging on a cold
intake component. Evaporation rate through this mechanism is a function of fuel properties,
temperature, pressure, relative droplet and air velocities and droplet diameter. Of
course, this approach breaks down in extreme ambient cold-starts, in which the fuel
volatility is insufficient to produce vapor in ignitable concentrations with air.
[0005] In order for combustion to be chemically complete, the fuel-air mixture must be vaporized
to a stoichiometric gas-phase mixture. A stoichiometric combustible mixture contains
the exact quantities of air (oxygen) and fuel required for complete combustion. For
gasoline, this airfuel ratio is about 14.7:1 by weight. A fuel-air mixture that is
not completely vaporized, nor chemically stoichiometric, results in incomplete combustion
and reduced thermal efficiency. The products of an ideal combustion process are water
(H
2O) and carbon dioxide (CO
2). If combustion is incomplete, some carbon is not fully oxidized, yielding carbon
monoxide (CO) and unburned hydrocarbons (HC).
[0006] The mandate to reduce air pollution has resulted in attempts to compensate for combustion
inefficiencies with a multiplicity of fuel system and engine modifications. As evidenced
by the prior art relating to fuel preparation and delivery systems, much effort has
been directed to reducing liquid fuel droplet size, increasing system turbulence and
providing sufficient heat to vaporize fuels to permit more complete combustion.
[0007] However, inefficient fuel preparation at lower engine temperatures remain a problem
which results in higher emissions, requiring after-treatment and complex control strategies.
Such control strategies can include exhaust gas recirculation, variable valve timing,
retarded ignition timing, reduced compression ratios, the use of catalytic converters
and air injection to oxidize unburned hydrocarbons and produce an exothermic reaction
benefiting catalytic converter light-off.
[0008] Over-fueling the engine during cold-start and warm-up is a significant source of
unburned hydrocarbon emissions in conventional engines. Compounding the problem is
the fact that the catalytic converter is also cold during this period of operation
and, thus, does not reduce a significant amount of the unburned hydrocarbons that
pass through the engine exhaust. As a result, the high engine-out concentrations of
unburned hydrocarbons pass essentially unreacted through the catalytic converter and
are emitted from the tailpipe. It has been estimated that as much as 80 percent of
the total hydrocarbon emissions produced by a typical, modern passenger car occurs
during the cold-start and warm-up period, in which the engine is over-fueled and the
catalytic converter is essentially inactive.
[0009] Given the relatively large proportion of unburned hydrocarbons emitted during startup,
this aspect of passenger car engine operation has been the focus of significant technology
development efforts. Furthermore, as increasingly stringent emissions standards are
enacted into legislation and consumers remain sensitive to pricing and performance,
these development efforts will continue to be paramount. Such efforts to reduce start-up
emissions from conventional engines generally fall into two categories: 1) reducing
the warm-up time for three-way catalyst systems and 2) improving techniques for fuel
vaporization. Efforts to reduce the warm-up time for three-way catalysts to date have
included: retarding the ignition timing to elevate the exhaust temperature; opening
the exhaust valves prematurely; electrically heating the catalyst; burner or flame
heating the catalyst; and catalytically heating the catalyst. As a whole, these efforts
are costly and do not address HC emissions during and immediately after cold start.
[0010] A variety of techniques have been proposed to address the issue of fuel vaporization.
U.S. Patents proposing fuel vaporization techniques include
U.S. Patent No. 5,195,477 issued to Hudson, Jr. et al,
U.S. Patent No. 5,331,937 issued to Clarke,
U.S. Patent No. 4,886,032 issued to Asmus,
U.S. Patent No. 4,955,351 issued to Lewis et al.,
U.S. Patent No. 4,458,655 issued to Oza,
U.S. Patent No. 6,189,518 issued to Cooke,
U.S. Patent No. 5,482,023 issued to Hunt,
U.S. Patent No. 6,109,247 issued to Hunt,
U.S. Patent No. 6,067,970 issued to Awarzamani et al.,
U.S. Patent No. 5,947,091 issued to Krohn et al.,
U.S. Patent No. 5,758,826 issued to Nines,
U.S. Patent No. 5,836,289 issued to Thring, and
U.S. Patent No. 5,813,388 issued to Cikanek, Jr. et al.
[0011] Other fuel delivery devices proposed include
U.S. Patent No. 3,716,416, which discloses a fuel-metering device for use in a fuel cell system. The fuel cell
system is intended to be self-regulating, producing power at a predetermined level.
The proposed fuel metering system includes a capillary flow control device for throttling
the fuel flow in response to the power output of the fuel cell, rather than to provide
improved fuel preparation for subsequent combustion. Instead, the fuel is intended
to be fed to the fuel cell for conversion to H
2. In a preferred embodiment, the capillary tubes are made of metal and the capillary
itself is used as a resistor, which is in electrical contact with the power output
of the fuel cell. Because the flow resistance of a vapor is greater than that of a
liquid, the flow is throttled as the power output increases. The fuels suggested for
use include any fluid that is easily transformed from a liquid to a vapor phase by
applying heat and flows freely through a capillary. Vaporization appears to be achieved
in the manner that vapor lock occurs in automotive engines.
[0012] U.S. Patent No. 6,276,347 proposes a supercritical or near-supercritical atomizer and method for achieving
atomization or vaporization of a liquid. The supercritical atomizer of
U.S. Patent No. 6,276,347 is said to enable the use of heavy fuels to fire small, light weight, low compression
ratio, spark-ignition piston engines that typically burn gasoline. The atomizer is
intended to create a spray of fine droplets from liquid, or liquid-like fuels, by
moving the fuels toward their supercritical temperature and releasing the fuels into
a region of lower pressure on the gas stability field in the phase diagram associated
with the fuels, causing a fine atomization or vaporization of the fuel. Utility is
disclosed for applications such as combustion engines, scientific equipment, chemical
processing, waste disposal control, cleaning, etching, insect control, surface modification,
humidification and vaporization.
[0013] To minimize decomposition,
U.S. Patent No. 6,276,347 proposes keeping the fuel below the supercritical temperature until passing the distal
end of a restrictor for atomization. For certain applications, heating just the tip
of the restrictor is desired to minimize the potential for chemical reactions or precipitations.
This is said to reduce problems associated with impurities, reactants or materials
in the fuel stream which otherwise tend to be driven out of solution, clogging lines
and filters. Working at or near supercritical pressure suggests that the fuel supply
system operate in the range of 21.1 to 56.2 kg/cm
2 (300 to 800) psig. While the use of supercritical pressures and temperatures might
reduce clogging of the atomizer, it appears to require the use of a relatively more
expensive fuel pump, as well as fuel lines, fittings and the like that are capable
of operating at these elevated pressures.
[0014] EP 0 915 248 A1 proposes a fuel injection device for use in the intake manifold of an internal combustion
engine that operates on liquefied petroleum gas. The proposed device consists of an
injector whose body has a tip through which a fuel outlet hole passes, furthermore
consisting of an injection tube that extends the tip of said injector and whose channel
is located in line with said outlet hole, with said injection tube having a cantilevered
portion extending into said intake manifold, as well as means at least partially preventing
the formation of frost on said injection tube.
[0015] U.S. Patent No. 5,873,354 proposes a fuel delivery system for an internal combustion engine having an intake
air metering device, leading to individual combustion chambers several fuel injection
valves, each of which is assigned to one combustion chamber, and a central fuel vaporizer
to which fuel can be supplied by a separate fuel metering device. It is further proposed
that fuel vapor generated in the fuel vaporizer can be added to the intake air for
the combustion chambers downstream from the intake air metering device to reduce pollutant
emissions during the warm-up phase of the internal combustion engine after start-up,.
[0016] In one aspect, the present invention is directed to a fuel injector for vaporizing
a liquid fuel for use in an internal combustion engine according to claim 1.
[0017] In another aspect, the present invention is directed to a fuel system for use in
an internal combustion engine according to claim 10.
[0018] In yet another aspect, the present invention is directed to a method of delivering
fuel to an internal combustion engine according to claim 13.
[0019] The present invention provides a fuel injector and delivery system that can supply
vaporized fuel while requiring minimal power and warm-up time, without the need for
a high pressure fuel supply system, which may be utilized in a number of configurations
including conventional port-fuel injection, hybrid-electric, gasoline direct-injection,
and alcohol-fueled engines.
[0020] The invention will now be described in more detail with reference to preferred forms
of the invention, given only by way of example, and with reference to the accompanying
drawings, in which:
FIG. 1 illustrates a modified fuel injector, in partial cross section, which includes
a capillary flow passage in accordance with a preferred form;
FIG. 2 is a side elevation view of an embodiment of the fuel injector according to
another preferred form;
FIG. 2A is an isometric view of an outlet of the capillary of the embodiment illustrated
in Fig. 2;
FIG. 3 is a side elevation view of another embodiment of a fuel injector according
to another preferred form;
FIG. 3A is an isometric view of another outlet design of the capillary of the embodiment
illustrated in Fig. 3;
FIG. 4 is a side elevation view of yet another embodiment of a fuel injector according
to a preferred form;
FIG. 4A is an isometric view of another outlet design of the capillary of the embodiment
illustrated in Fig. 4;
FIG. 5 is a schematic illustration of still another embodiment of a fuel injector
according to a preferred form;
FIG. 6 is a side view of yet still another embodiment of a fuel injector according
to a preferred form;
FIG. 7 is a cross-sectional view of another embodiment of the fuel injector according
to yet another preferred form;
FIG. 8 is a side view of another embodiment employing dual injectors in accordance
with still another preferred form;
FIG. 9 is a side view of another embodiment of a fuel injector according to a preferred
form shown in partial cross-section;
FIG. 9A is an enlarged view of an identified portion of the embodiment shown in Fig.
9;
FIG. 10 is a side view of another embodiment of a fuel injector according to a preferred
form, shown in partial cross-section;
FIG. 10A is an enlarged view of an identified portion of the embodiment shown in Fig.
10;
FIG. 11 is a side elevation view of yet another preferred form of a fuel injector
in accordance herewith;
FIG. 11A is an isometric view of another outlet design of the capillary of the embodiment
illustrated in Fig. 11;
FIG. 12 is a side view of another embodiment of a fuel injector having a capillary
passage heated with recirculated exhaust gas;
FIG. 13 is a schematic of a fuel delivery and control system, in accordance with a
preferred form;
FIG. 14 is a chart illustrating engine parameters during the first 20 seconds of starting
in engine using the fuel delivery device of the invention;
FIG. 15 is a chart illustrating a comparison of engine emissions from the fuel delivery
device of the invention with conventional port-fuel injectors;
FIG. 16 is a graph of gasoline mass flow as a function of time showing the benefit
to operation achieved through the use of the oxidation cleaning method of the present
invention;
FIG. 17 is a graph of fuel flow rate vs. time for a commercial-grade gasoline;
FIG. 18 presents a graph of fuel flow rate vs. time comparing various gasolines;
FIG. 19 is a graph of fuel flow rate vs. time comparing a jet fuel to a No. 2 diesel
fuel;
FIG. 20 presents a graph of fuel flow rate vs. time for an unadditized diesel fuel
showing the effect of oxidation cleaning; and
FIG. 21 is a graph of fuel flow rate v s. time comparing an unadditized diesel fuel
to a diesel fuel containing an anti-fouling additive.
[0021] Reference is now made to the embodiments illustrated in Figs. 1-21 wherein like numerals
are used to designate like parts throughout.
[0022] The present invention provides a fuel preparation and delivery useful for cold-start,
warm-up and normal operation of an internal combustion engine. The fuel system includes
a fuel injector having a capillary flow passage, capable of heating liquid fuel so
that substantially vaporized fuel is supplied into an engine cylinder. The substantially
vaporized fuel can be combusted with reduced emissions compared to conventional fuel
injector systems. Furthermore, the fuel delivery system of the present invention requires
less power, and has shorter warm-up times than other vaporization techniques.
[0023] In general, gasolines do not readily vaporize at low temperatures. During the cold
start and warm-up period, relatively little vaporization of the liquid fuel takes
place. As such, it is necessary to provide an excess of liquid fuel to each cylinder
of the engine in order to achieve an air/fuel mixture that will combust. Upon ignition
of the fuel vapor, which is generated from the excess of liquid fuel, combustion gases
discharged from the cylinders include unburned fuel and undesirable gaseous emissions.
However, upon reaching normal operating temperature, the liquid fuel readily vaporizes,
so that less fuel is needed to achieve an air/fuel mixture that will readily combust.
Advantageously, upon reaching normal operating temperature, the air/fuel mixture can
be controlled at or near stoichiometry, thereby reducing emissions of unburned hydrocarbons
and carbon monoxide. Additionally, when fueling is controlled at or near stoichiometry,
just enough air is available in the exhaust stream for simultaneous oxidation of unburned
hydrocarbons and carbon monoxide and reduction of nitrogen oxides over a three-way
catalyst (TWC).
[0024] The system and method of the present invention injects fuel that has been substantially
vaporized into the intake flow passage, or directly into an engine cylinder, thereby
eliminating the need for excess fuel during the start-up and warm-up period of an
engine. The fuel is preferably delivered to the engine in a stoichiometric or fuel-lean
mixture, with air, or air and diluent, so that virtually all of the fuel is burned
during the cold start and warm-up period.
[0025] With conventional port-fuel injection, over-fueling is required to ensure robust,
quick engine starts. Under fuel-rich conditions, the exhaust stream reaching the three-way
catalyst does not contain enough air to oxidize the excess fuel and unburned hydrocarbons
as the catalyst warms up. One approach to address this issue is to utilize an air
pump to supply additional air to the exhaust stream upstream of the catalytic converter.
The objective is to generate a stoichiometric or slightly fuel-lean exhaust stream
that can react over the catalyst surface once the catalyst reach its light-off temperature.
In contrast, the system and method of the present invention enables the engine to
operate at stoichiometric or even slightly fuel-lean conditions during the cold-start
and warm-up period, eliminating both the need for over-fueling and the need for an
additional exhaust air pump, reducing the cost and complexity of the exhaust after
treatment system.
[0026] As mentioned, during the cold start and warm-up period, the three-way catalyst is
initially cold and is not able to reduce a significant amount of the unburned hydrocarbons
that pass through the catalyst. Much effort has been devoted to reducing the warm-up
time for three-way catalysts, so as to convert a larger fraction of the unburned hydrocarbons
emitted during the cold-start and warm-up period. One such concept is to deliberately
operate the engine very fuel-rich during the cold-start and warm-up period. Using
an exhaust air-pump to supply air in this fuel-rich exhaust stream, a combustible
mixture can be generated which is burned either by auto-ignition or by some ignition
source upstream of, or in, the catalytic converter. The exotherm produced by this
oxidation process significantly heats up the exhaust gas and the heat is largely transferred
to the catalytic converter as the exhaust passes through the catalyst. Using the system
and method of the present invention, the engine could be controlled to operate alternating
cylinders fuel-rich and fuel-lean to achieve the same effect but without the need
for an air pump. For example, with a four-cylinder engine, two cylinders could be
operated fuel-rich during the cold-start and warm-up period to generate unburned hydrocarbons
in the exhaust. The two remaining cylinders would be operated fuel-lean during cold-start
and warm-up, to provide oxygen in the exhaust stream.
[0027] The system and method of the present invention may also be utilized with gasoline
direct injection engines (GDI). In GDI engines, the fuel is injected directly into
the cylinder as a finely atomized spray that evaporates and mixes with air to form
a premixed charge of air and vaporized fuel prior to ignition. Contemporary GDI engines
require high fuel pressures to atomize the fuel spray. GDI engines operate with stratified
charge at part load to reduce the pumping losses inherent in conventional indirect
injected engines. A stratified-charge, spark-ignited engine has the potential for
burning lean mixtures for improved fuel economy and reduced emissions. Preferably,
an overall lean mixture is formed in the combustion chamber, but is controlled to
be stoichiometric or slightly fuel-rich in the vicinity of the spark plug at the time
of ignition. The stoichiometric portion is thus easily ignited, and this in turn ignites
the remaining lean mixture. While pumping losses can be reduced, the operating window
currently achievable for stratified charge is limited to low engine speeds and relatively
light engine loads. The limiting factors include insufficient time for vaporization
and mixing at higher engine speeds and insufficient mixing or poor air utilization
at higher loads. By providing vaporized fuel, the system and method of the present
invention can widen the operating window for stratified charge operation, solving
the problem associated with insufficient time for vaporization and mixing. Advantageously,
unlike conventional GDI fuel systems, the fuel pressure employed in the practice of
the present invention can be lowered, reducing the overall cost and complexity of
the fuel system.
[0028] The invention provides a fuel delivery device for an internal combustion engine which
includes a pressurized liquid fuel supply that supplies liquid fuel under pressure,
at least one capillary flow passage connected to the liquid fuel supply, and a heat
source arranged along the at least one capillary flow passage. The heat source is
operable to heat liquid fuel in the at least one capillary flow passage sufficiently
to deliver a stream of substantially vaporized fuel. The fuel delivery device is preferably
operated to deliver the stream of vaporized fuel to one or more combustion chambers
of an internal combustion engine during start-up, warm-up and other operating conditions
of the internal combustion engine. If desired, the at least one capillary flow passage
can be used to deliver liquid fuel to the engine under normal operating conditions.
[0029] The invention also provides a method of delivering fuel to an internal combustion
engine, including the steps of supplying the pressurized liquid fuel to at least one
capillary flow passage, and heating the pressurized liquid fuel in the at least one
capillary flow passage sufficiently to cause a stream of vaporized fuel to be delivered
to at least one combustion chamber of an internal combustion engine during start-up,
warm-up, and other operating conditions of the internal combustion engine.
[0030] A fuel delivery system according to the invention includes at least one capillary-sized
flow passage through which pressurized fuel flows before being injected into an engine
for combustion. A capillary-sized flow passage is provided with a hydraulic diameter
that is less than 2 mm, preferably less than 1 mm and more preferably less than 0.5
mm. Hydraulic diameter is used in calculating fluid flow through a fluid carrying
element. Hydraulic diameter is defined as the flow area of the fluid-carrying element
divided by the perimeter of the solid boundary in contact with the fluid (generally
referred to as the "wetted" perimeter). In the case of a fluid carrying element of
circular cross section, the hydraulic radius when the element is flowing full is (πD
2/4)/πD=D/4. For the flow of fluids in noncircular fluid carrying elements, the hydraulic
diameter is used. From the definition of hydraulic radius, the diameter of a fluid-carrying
element having circular cross section is four times its hydraulic radius. Therefore,
hydraulic diameter is defined as four times the hydraulic radius.
[0031] Heat is applied along the capillary passageway, resulting in at least a portion of
the liquid fuel that enters the flow passage being converted to a vapor as it travels
along the passageway. The fuel exits the capillary passageway as a vapor, which optionally
contains a minor proportion of heated liquid fuel, which has not been vaporized. By
substantially vaporized is meant that at least 50% volume of the liquid fuel is vaporized
by the heat source, more preferably at least 70%, and most preferably at least 80%
of the liquid fuel is vaporized. Although it may be difficult to achieve 100% vaporization
due to complex physical effects that take place, nonetheless complete vaporization
would be desirable. These complex physical effects include variations in the boiling
point of the fuel since the boiling point is pressure dependent and pressure can vary
in the capillary flow passage. Thus, while it is believed that a major portion of
the fuel reaches the boiling point during heating in the capillary flow passage, some
of the liquid fuel may not be heated enough to be fully vaporized with the result
that a portion of the liquid fuel passes through the outlet of the capillary flow
passage along with the vaporized fluid.
[0032] The capillary-sized fluid passage is preferably formed in a capillary body such as
a single or multilayer metal, ceramic or glass body. The passage has an enclosed volume
opening to an inlet and an outlet either of which, or both, may be open to the exterior
of the capillary body or may be connected to another passage within the same body
or another body or to fittings. The heater can be formed by a portion of the body
such as a section of a stainless steel tube or the heater can be a discrete layer
or wire of resistance heating material incorporated in or on the capillary body. The
fluid passage may be any shape comprising an enclosed volume opening to an inlet and
an outlet and through which a fluid may pass. The fluid passage may have any desired
cross-section with a preferred cross-section being a circle of uniform diameter. Other
capillary fluid passage cross-sections include non-circular shapes such as triangular,
square, rectangular, oval or other shape and the cross section of the fluid passage
need not be uniform. The fluid passage can extend rectilinearly or non-rectilinearly
and may be a single fluid passage or multi-path fluid passage. In the case where the
capillary passage is defined by a metal capillary tube, the tube can have an inner
diameter of 0.01 to 3 mm, preferably 0.1 to 1 mm, most preferably 0.15 to 0.5 mm.
Alternatively, the capillary passage can be defined by transverse cross sectional
area of the passage, which can be 8 x 10
-5 to 7 mm
2, preferably 8 x 10
-3 to 8 x 10
-1 mm
2 and more preferably 2 x 10
-3 to 2 x 10
-1 mm
2. Many combinations of a single or multiple capillaries, various pressures, various
capillary lengths, amounts of heat applied to the capillary, and different cross-sectional
areas will suit a given application.
[0033] The liquid fuel can be supplied to the capillary flow passage under a pressure of
at least 0.7 kg/cm
2 (10 psig), preferably at least 1.4 kg/cm
2 (20 psig). In the case where the capillary flow passage is defined by the interior
of a stainless steel tube having an internal diameter of approximately 0.051 cm (0.020
in) and a length of approximately 15.2 cm (6 in), the fuel is preferably supplied
to the capillary passageway at a pressure of 7 kg/cm
2 (100 psig) or less to achieve mass flow rates required for stoichiometric start of
a typical size automotive engine cylinder (on the order of 100-200 mg/s). The at least
one capillary passageway provides a sufficient flow of substantially vaporized fuel
to ensure a stoichiometric or nearly stoichiometric mixture of fuel and air that can
be ignited and combusted within the cylinder(s) of an engine without producing undesirably
high levels of unburned hydrocarbons or other emissions. The capillary tube also is
characterized by having a low thermal inertia, so that the capillary passageway can
be brought up to the desired temperature for vaporizing fuel very quickly, preferably
within 2.0 seconds, more preferably within 0.5 second, and most preferably within
0.1 second, which is beneficial in applications involving cold starting an engine.
The low thermal inertia also could provide advantages during normal operation of the
engine, such as by improving the responsiveness of the fuel delivery to sudden changes
in engine power demands.
[0034] During vaporization of liquid fuel in a heated capillary passage, deposits of carbon
and/or heavy hydrocarbons can accumulate on the capillary walls and the flow of the
fuel can be severely restricted which ultimately can lead to clogging of the capillary
flow passage. The rate at which these deposits accumulate is a function of capillary
wall temperature, fuel flow rate and fuel type. It is believed that fuel additives
may be useful in reducing such deposits. However, should clogging develop, such clogging
can be cleared by oxidizing the deposits.
[0035] FIG. 1 presents a fuel injector 10 for vaporizing a liquid fuel drawn from a source
of liquid fuel, in accordance with the present invention. Apparatus 10 includes a
capillary flow passage 12, having an inlet end 14 and an outlet end 16. A fluid control
valve 18 is provided for placing inlet end 14 of capillary flow passage 12 in fluid
communication with a liquid fuel source F and introducing the liquid fuel in a substantially
liquid state into capillary flow passage 12.
[0036] As is preferred, fluid control valve 18 may be operated by solenoid 28. Solenoid
28 has coil windings 32 connected to electrical connector 30. W hen the coil windings
32 are energized, the solenoid element 36 is drawn into the center of coil windings
32. When electricity is cut off from the coil windings 32, a spring 38 returns the
solenoid element to its original position. A pintle 40 is connected to the solenoid
element 36. Movement of the solenoid element 36, caused by applying electricity to
the coil windings 32, causes the pintle to be drawn away from a hole 42 allowing fuel
to flow through the hole 42.
[0037] A heat source 20 is arranged along capillary flow passage 12. As is most preferred,
heat source 20 is provided by forming capillary flow passage 12 from a tube of electrically
resistive material, a portion of capillary flow passage 12 forming a heater element
when a source of electrical current is connected to the tube at connections 22 and
24 for delivering current therethrough. Heat source 20, as may be appreciated, is
then operable to heat the liquid fuel in capillary flow passage 12 to a level sufficient
to change at least a portion thereof from a liquid state to a vapor state and deliver
a stream of substantially vaporized fuel from outlet end 16 of capillary flow passage
12.
[0038] Apparatus 10 also includes means for cleaning deposits formed during operation of
apparatus 10. The means for cleaning deposits shown in FIG.1 includes fluid control
valve 18, heat source 20 and an oxidizer control valve 26 for placing capillary flow
passage 12 in fluid communication with a source of oxidizer C. As may be appreciated,
the oxidizer control valve can be located at or near either end of capillary flow
passage 12 or configured to be in fluid communication with either end of capillary
flow passage 12. If the oxidizer control valve is located at or near the outlet end
16 of capillary flow passage 12, it then serves to place the source of oxidizer C
in fluid communication with the outlet end 16 of capillary flow passage 12. In operation,
heat source 20 is used to heat the oxidizer C in capillary flow passage 12 to a level
sufficient to oxidize deposits formed during the heating of the liquid fuel F. In
one embodiment, to switch from a fueling mode to a cleaning mode, the oxidizer control
valve 26 is operable to alternate between the introduction of liquid fuel F and the
introduction of oxidizer C into capillary flow passage 12 and enable in-situ cleaning
of capillary flow passage 12 when the oxidizer is introduced into the at least one
capillary flow passage.
[0039] One technique for oxidizing deposits includes passing air or steam through the capillary.
The flow passage is preferably heated during the cleaning operation so that the oxidation
process is initiated and nurtured until the deposits are consumed. To enhance this
cleaning operation, a catalytic substance may be either employed, a s a coating on,
or as a component of, the capillary wall to reduce the temperature and/or time required
for accomplishing the cleaning. For continuous operation of the fuel delivery system,
more than one capillary flow passage can be used such that when a clogged condition
is detected, such as by the use of a sensor, fuel flow can be diverted to another
capillary flow passage and oxidant flow initiated through the clogged capillary flow
passage to be cleaned. As an example, a capillary body can include a plurality of
capillary flow passages therein and a valving arrangement can be provided to selectively
supply liquid fuel or air to each flow passage.
[0040] Alternatively, fuel flow can be diverted from a capillary flow passage and oxidant
flow initiated at preset intervals. Fuel delivery to a capillary flow passage can
be effected by a controller. For example, the controller can activate fuel delivery
for a preset time period and deactivate fuel delivery after the preset amount of time.
The controller may also effect adjustment of the pressure of the liquid fuel and/or
the amount of heat supplied to the capillary flow passage based on one or more sensed
conditions. The sensed conditions may include inter alia: the fuel pressure; the capillary
temperature; and the air fuel mixture. The controller may also control multiple fuel
delivery devices attached to the application. The controller may also control one
or more capillary flow passages to clear deposits or clogs therefrom. For example,
cleaning of a capillary flow passage can be achieved by applying heat to the capillary
flow passage and supplying a flow of an oxidant source to the capillary flow passage.
[0041] The heated capillary flow passage 12, in accordance with the invention can produce
a vaporized stream of fuel, which condenses in air to form a mixture of vaporized
fuel, fuel droplets, and air commonly referred to as an aerosol. Compared to a conventional
automotive port-fuel injector, which delivers a fuel spray comprised of droplets in
the range of 150 to 200 µm Sauter Mean Diameter (SMD), the aerosol has an average
droplet size of less than 25 µm SMD, preferably less than 15 µm SMD. Thus, the majority
of the fuel droplets produced by the heated capillary according to the invention can
be carried by an air stream, regardless of the flow path, into the combustion chamber.
[0042] The difference between the droplet size distributions of a conventional injector
and the heated capillary flow passage according to the invention is particularly critical
during cold-start and warm-up conditions. Specifically, using a conventional port-fuel
injector, relatively cold intake manifold components necessitate over-fueling such
that a sufficient fraction of the large fuel droplets, impinging on the intake components,
are vaporized to produce an ignitable fuel/air mixture. Conversely, the vaporized
fuel and fine droplets produced by the fuel injector of the present invention are
essentially unaffected by the temperature of engine components upon start-up and,
as such, eliminate the need for over-fueling during engine start-up conditions. The
elimination of over-fueling combined with more precise control over the fuel/air ratio
to the engine afforded through the use of the heated capillary injector of the present
invention results in greatly reduced cold start emissions compared to those produced
by engines employing conventional fuel injector systems. In addition to a reduction
in over-fueling, it should also be noted that the heated capillary injector according
to the invention further enables fuel-lean operation during cold-start and warm-up,
which results in a greater reduction in tailpipe emissions while the catalytic converter
warms up.
[0043] Referring still to FIG. 1, capillary flow passage 12 can comprise a metal tube such
as a stainless steel capillary tube and the heater comprising a length of the tube
20 through which electrical current is passed. In a preferred embodiment, the capillary
tube is provided with an internal diameter of approximately 0.051 to 0.076 cm (0.020
to 0.030 in), a heated length of approximately 5.08 to 25.4 cm (2 to 10 in), and fuel
can be supplied to the tube 12 at a pressure of less than 7.0 kg/cm
2 (100 psig), preferably less than 4.9 kg/cm
2 (70 psig), more preferably less than 4.2 kg/cm
2 (60 psig) and even more preferably less than 3.1 kg/cm
2 (45 psig) or less. It has been shown that this embodiment produces vaporized fuel,
which forms a distribution of aerosol droplets, which mostly range in size from 2
to 30 µm SMD with an average droplet size of about 5 to 15 µm SMD, when the vaporized
fuel is condensed in air at ambient temperature. The preferred size of fuel droplets
to achieve rapid and nearly complete vaporization at cold-starting temperatures is
less than about 25 µm. This result can be achieved by applying approximately 10.2
to 40.8 kg/sec (100 to 400W), e.g., 20.4 kg/sec (200W) of electrical power, which
corresponds to 2-3% of the energy content of the vaporized fuel, to a six-inch stainless
steel capillary tube. The electrical power can be applied to the capillary tube by
forming the tube entirely from an electrically conductive material such as stainless
steel, or by providing a conductive material over at least a portion of a non-electrically
conducting tube or laminate having a flow passage therein such as by laminating or
coating an electrically resistive material to form a resistance heater on the tube
or laminate. Electrical leads can be connected to the electrically conductive material
to supply the electrical current to the heater to heat the tube along its length.
Alternatives for heating the tube along its length could include inductive heating,
such as by an electrical coil positioned around the flow passage, or other sources
of heat positioned relative to the flow passage to heat the length of the flow passage
through one or a combination of conductive, convective or radiative heat transfer.
[0044] Although, a preferred capillary tube has a heated length of approximately 15.2 cm
(6 in) and an internal diameter of approximately 0.051 cm (0.020 in), other configurations
of capillaries provide acceptable vapor quality. For example, the internal diameter
can range from 0.05 to 0.08 cm (0.02 to 0.03 in) and the heated portion of the capillary
tube can range from 2.5 to 25.4 cm (1 to 10 in). After cold-start and warm-up, it
is not necessary to heat the capillary tube such that the unheated capillary tube
can be used to supply adequate liquid fuel to an engine operating at normal temperature.
[0045] The vaporized fuel exiting from the fuel capillary according to the invention can
be injected into an engine intake manifold at the same location as existing port-fuel
injectors or at another location along the intake manifold. If desired, however, the
fuel capillary can be arranged to deliver vaporized fuel directly into each cylinder
of the engine. The fuel capillary provides advantages over systems that produce larger
droplets of fuel that must be injected against the back side of a closed intake valve
while starting the engine. Preferably, the outlet of the fuel capillary tube is positioned
flush with the intake manifold wall similar to the arrangement of the outlets of conventional
fuel injectors.
[0046] After approximately 20 seconds (or preferably less) from starting the engine, heat
to the capillary flow passage 12 can be turned off and liquid injection initiated
using conventional fuel injectors, for normal engine operation. Normal engine operation
can alternatively be performed by liquid fuel injection through an unheated capillary
flow passage 12 via continuous injection or possibly pulsed injection.
[0047] Referring to FIG. 2, a second exemplary embodiment of the present invention is shown.
A fuel injector 100 has a capillary flow passage 112. Capillary flow passage 112 is
heated along heated length 120. The capillary flow passage 112 is fitted with a flared
end 150 with a plurality of perforations 152 in a plate 154 covering the flared end
150 as illustrated by FIG. 2A. The fuel injector 100 can include a fluid control valve
such as a solenoid valve of the type described above and shown in FIG. 1, which allows
delivery of pressurized liquid fuel to the capillary flow passage 112. After the engine
is sufficiently heated, heating of the capillary flow passage 112 can be terminated
and liquid fuel can be supplied through the capillary flow passage 112.
[0048] Referring now to FIG. 3, a third exemplary embodiment of the present invention is
shown. A fuel injector 200 is depicted having a capillary flow passage 212. Capillary
flow passage 212 is heated along heated length 220. The capillary flow passage 212
is fitted with a flat end 250 with a plurality of perforations 252 in a plate 254
covering the flat end 250 as illustrated by FIG. 3A. The fuel injector 200 can include
a fluid control valve such as a solenoid valve of the type described above and shown
in FIG. 1, which allows delivery of pressurized liquid fuel to the capillary flow
passage 212. As described above, after an engine utilizing a plurality of fuel injectors
200 is started, heating of the capillary flow passage 212 can be terminated and liquid
fuel can be supplied through the capillary flow passage 212. Injector 200 can advantageously
be cleaned through the use of the oxidation technique described above.
[0049] Referring now to FIG. 4, a fourth exemplary embodiment of the present invention is
shown. A fuel injector 300 is depicted having a capillary flow passage 312. Capillary
flow passage 312 is heated along heated length 320. The capillary flow passage 312
is fitted with a conical end 350 with a plurality of perforations 352 in a conical
plate 354 covering the conical end 350 as illustrated by FIG. 4A. The fuel injector
300 can include a fluid control valve such as a solenoid valve of the type described
above and shown in FIG. 1, which allows delivery of pressurized liquid fuel to the
capillary flow passage 312. As described above, after an engine utilizing a plurality
of fuel injectors 300 is started, heating of the capillary flow passage 312 can be
terminated and liquid fuel can be supplied through the capillary flow passage 212.
Injector 300 can advantageously be cleaned through the use of the oxidation technique
described above.
[0050] Referring now to FIG. 5, a dual fuel injector 400, in accordance with the present
invention, is shown. FIG. 5 illustrates the dual function fuel injector 400, which
may comprise a conventional type fuel injector 460 and a heated capillary injector
410. In this embodiment, a heated capillary flow passage 412 is integrated into the
fuel injector 400. After about 20 seconds from starting the engine, or preferably
less, the capillary injector 410 can be deactivated via a solenoid activated plunger
436 and the conventional injector 460 activated via another solenoid-activated plunger
470 for continued operation of the engine.
[0051] Another exemplary embodiment of the present invention is shown in FIG. 6. As shown,
a fuel injector 500 may be fitted with a heated capillary flow passage 512 and a liquid
fuel injector nozzle 560. Fuel flow can be selectively directed to the heated capillary
flow passage 512 to provide vaporized fuel or the nozzle 560 to provide liquid fuel
through the use of valving arrangement 540, as shown in Fig. 6. After approximately
20 seconds from the start of the engine, or preferably less, fuel flow can be switched
from the capillary flow passage 512 to the liquid flow nozzle 560 by the valving arrangement
540 for normal operation of the engine. The valving arrangement 540 can be operated
by a controller, forming part of an electronic engine control system.
[0052] Referring now to FIG. 7, yet another exemplary embodiment of the present invention
is shown. A fuel injector 600 has a helical heated capillary flow passage 612 is wrapped
around within the interior of the fuel injector 600 as illustrated in FIG. 7. In this
embodiment, the capillary flow passage 612 is coiled around the solenoid assembly
628 and is heated along heated length 620, defined by electrical connections 622 and
624. This embodiment is useful in a situation where space is limited and a linear
capillary tube is not feasible. In addition, this embodiment could be adapted for
use with a conventional fuel injector (see FIG. 8) for delivering fuel to an engine
during normal operating conditions.
[0053] Referring now to FIG. 8, an engine intake port 700 is fitted with a heated capillary
injector 10 (of the type described with reference to FIG. 1) and a conventional liquid
fuel injector 750. In this embodiment, fuel will be delivered to the engine by the
capillary flow passage 12, heated along its length 20, during the cold-start and warm-up
of the engine. After the first approximately 20 seconds from starting the engine,
or preferably less, the heated capillary injector 10 will be deactivated and the conventional
fuel injector 750 activated for normal operation of the engine.
[0054] As will be appreciated, the apparatus and system for preparing and delivering fuel
depicted in FIGS. 1 through 4 and 7 may also be used in connection with another embodiment
of the present invention. Referring a gain to FIG. 1, the means for cleaning deposits
includes fluid control valve 28, a solvent control valve 26 for placing capillary
flow passage 12 in fluid communication with a solvent, solvent control valve 26 disposed
at one end of capillary flow passage 12. In one embodiment of the apparatus employing
solvent cleaning, the solvent control valve 26 (the oxidizer control valve in the
preferred form employing the oxidation cleaning technique, described above) is operable
to alternate between the introduction of liquid fuel and the introduction of solvent
into capillary flow passage 12, enabling the in-situ cleaning of capillary flow passage
12 when the solvent is introduced into capillary flow passage 12. While a wide variety
of solvents have utility, the solvent may comprise liquid fuel from the liquid fuel
source. When this is the case, no solvent control valve is required, as there is no
need to alternate between fuel and solvent, and the heat source should be deactivated
during the cleaning of capillary flow passage 12.
[0055] Another embodiment of the present invention is shown in partial cross-section in
FIG. 9. A fuel injector 800 having a heated capillary flow passage tube 812 for delivering
fuel to an internal combustion engine is shown in FIG. 9. Details of the tube for
delivering fuel to an internal combustion engine are illustrated in FIG. 9A. As shown,
an axially moveable rod 850 is positioned inside of capillary flow passage 812. The
distal end 816 of capillary flow passage 812 is flared and the distal end 852 of axially
moveable rod 850 is tapered to form a valve 854 wherein axial movement of the rod
850 opens and closes the valve 854. As may be appreciated, the repeated movement of
axially moveable rod 850 is effective for abrading deposits formed during operation
of the fuel injector of the present invention.
[0056] Referring now to FIG. 10, yet another embodiment of the present invention is shown
in partial cross-section. A fuel injector 900 having a heated capillary flow passage
tube 912 for delivering fuel to an internal combustion engine is shown in FIG. 10.
Details of the tube for delivering fuel to an internal combustion engine are illustrated
in FIG. 10A. As shown, an axially moveable rod 950 is positioned inside of capillary
flow passage 912. The distal end 916 of capillary flow passage 912 is flared and the
distal end 952 of axially moveable rod 950 is tapered to form a valve 954 wherein
axial movement of the rod 950 opens and closes the valve 954. Also arranged inside
the capillary flow passage 912 are a plurality of brushes 960 arranged along axial
moveable rod 950 for cleaning the capillary flow passage 912. As may be appreciated,
the repeated movement of axially moveable rod 950 is effective for abrading deposits
formed during operation of the fuel injector of the present invention.
[0057] Referring now to FIG. 11, another exemplary embodiment of the present invention is
shown in partial cross-section. A fuel injector 1000 has multiple capillaries 1012
arranged in parallel for delivering fuel to an internal combustion engine. In this
embodiment, fuel will be delivered to the engine by one or more of the capillary flow
passages 1012, heated along their length 1020, during specific periods of engine operation
(e.g., cold-start, warm-up and acceleration conditions). As less vaporized fuel is
required for reduction of unburned hydrocarbons, heat to one or more capillaries in
this configuration can be deactivated.
[0058] FIG. 12 shows, in simplified form, how a fuel injector 10, having a capillary flow
passage 12 can be arranged so that liquid fuel traveling therethrough can be heated
to an elevated temperature through the use of recirculated exhaust gas (EGR) to reduce
power requirements of the fuel-vaporizing resistance heater 20. As shown, capillary
flow passage 12 passes through EGR passage 1100 for heating. For initial engine start-up,
resistance heater 20 comprising a section of the capillary flow passage 12 or a separate
resistance heater is connected to a power source such as a battery, to initially vaporize
the liquid fuel F. After about 20 seconds of operation the capillary flow passage
12 can be heated by the heat of EGR to reduce the power otherwise needed for continued
vaporization of the fuel by the resistance heater 20. Thus, the fuel in the capillary
flow passage 12 can be vaporized without using the resistance heater 20 so that power
can be conserved.
[0059] FIG. 13 shows an exemplary schematic of a control system 2000 used to operate an
internal combustion engine 2110 incorporating a liquid fuel supply valve 2220 in fluid
communication with a liquid fuel supply 2010 and a liquid fuel injection path 2260,
a vaporized fuel supply valve 2210 in fluid communication with a liquid fuel supply
2010 and capillary flow passages 2080, and an oxidizing gas supply valve 2020 in fluid
communication with an oxidizing gas supply 2070 and capillary flow passages 2080.
The control system includes a controller 2050, which typically receives a plurality
of input signals from a variety of engine sensors such as engine speed sensor 2060,
intake manifold air thermocouple 2062, coolant temperature sensor 2064, exhaust airfuel
ratio sensor 2150, fuel supply pressure 2012, etc. In operation, the controller 2050
executes a control algorithm based on one or more input signals and subsequently generates
an output signal 2024 to the oxidizer supply valve 2020 for cleaning clogged capillary
passages in accordance with the invention, an output signal 2014 to the liquid fuel
supply valve 2220, an output signal 2034 to the vaporized fuel supply valve 2210,
and a heating power command 2044 to a power supply which delivers heat to the capillaries
2080.
[0060] In operation, the system according to the invention can be configured to feed back
heat produced during combustion through the use of exhaust gas recycle heating such
that the liquid fuel is heated sufficiently to substantially vaporize the liquid fuel
as it passes through the capillary flow passages 2080 reducing or eliminating or supplementing
the need to electrically or otherwise heat the capillary flow passages 2080.
Examples
Example 1
[0061] Tests were performed wherein JP 8 jet fuel was vaporized by supplying the fuel to
a heated capillary flow passage at constant pressure with a micro-diaphragm pump system.
In these tests, capillary tubes of different diameters and lengths were used. The
tubes were constructed of 304 stainless steel having lengths of 2.5 to 7.6 cm (1 to
3 in) and internal diameters (ID) and outer diameters (OD), in cm (in), as follows:
0.025 ID/0.046 OD (0.010 ID/0.018 OD), 0.033 ID/0.083 OD (0.013 ID/ 0.033 OD), and
0.043 ID/0.064 OD (0.017 ID/0.025 OD). Heat for vaporizing the liquid fuel was generated
by passing electrical current through a portion of the metal tube. The droplet size
distribution was measured using a Spray-Tech laser diffraction system manufactured
by Malvern. Droplets having a Sauter Mean Diameter (SMD) of between 1.7 and 4.0 µm
were produced. SMD is the diameter of a droplet whose surface-to-volume ratio is equal
to that of the entire spray and relates to the spray's mass transfer characteristics.
Example 2
[0062] Tests were performed again using gasoline that was vaporized by supplying the fuel
to a heated capillary flow passage at constant pressure with a micro-diaphragm pump
system. In these tests, capillary flow passages of different diameters and lengths
were used. The following table shows empirical findings for various capillary tube
configurations.
[0063]
Internal Diameter cm (in) |
Heated Length cm (in) |
Fuel Pressure kg/cm2 (psig) |
Results |
0.069 (0.027) |
17.2 (6.75) |
5.3 (75) |
Generated fully vaporized flow and flow rate of 180 mg/s. |
0.074 (0.029) |
18.4(7.25) |
4.6 (65) |
Generated high flow rates with a heating voltage of 20v. |
0.051 (0.020) |
15.2 (6.0) |
4.9 (70) |
Generated at least 200 mg/s flow rate with substantially adequate vapor characteristics. |
Example 3
[0064] In tests using a Ford 4.6 liter V8 engine, one bank of four cylinders was modified
to include fuel delivery devices of the invention as shown in FIG. 1. The capillary
heating elements were mounted with the tip of the capillary positioned flush with
the intake port wall, this being the location of the stock fuel injection nozzle.
The tests were carried out with continuous injection (100% duty cycle) and, therefore,
fuel pressure was used to regulate the fuel vapor flow rate.
[0065] Referring to FIG. 14, a graph illustrating results of the capillary fuel delivery
device during the first 20 seconds of cold start of an engine is presented. Plot line
1 represents the engine speed, in revolutions per minute, as time progresses along
the x-axis. Plot line 2 represents the fuel flow, in grams per second, as time progresses
along the x-axis. Plot line 3 represents lambda as time progresses along the x-axis,
wherein a lambda of unity represents the stoichiometric ratio of air to fuel. Plot
line 4 represents the total hydrocarbon emissions output, in methane equivalent parts
per million, from the exhaust of the engine as time progresses along the x-axis.
[0066] As illustrated by plot line 3 in FIG. 14, the initial over-fueling required for the
stock engine hardware and control strategy was eliminated through the use of the fuel
delivery device of the invention. That is, the fuel delivery device of the invention
efficiently vaporized liquid fuel during the initial start-up period such that the
engine was started with a near-stoichiometric fuel/air ratio. FIG. 15 is a graph,
which illustrates the emission reduction resulting from the near-stoichiometric start
achieved with the fuel delivery device of the invention (plot line 6), compared to
the conventional over-fueling start-up strategy (plot line 5). Specifically, the results
in FIG. 15 demonstrate that the fuel delivery device of the invention reduced integrated
hydrocarbon emissions by 46% during the first ten seconds of cold-start as compared
to the stock configuration, which requires over-fueling. The area indicated by circle
7 illustrates the dramatic reduction of hydrocarbon emissions during the first four
seconds of starting the engine.
Example 4
[0067] Tests were conducted to demonstrate the benefits of the oxidation cleaning technique
on a heated capillary flow passage using an unadditized, sulfur-free base gasoline
known to produce high levels of deposit formation. The capillary flow passage employed
for these tests was a 5.1 cm (2 in) long heated capillary tube constructed of stainless
steel, having an inner diameter of 0.058 cm (0.023 in). Fuel pressure was maintained
at 0.7 kg/cm
2 (10 psig). Power was supplied to the capillary to achieve various levels of R/R
o; where R is the heated capillary resistance and R
o is the capillary resistance under ambient conditions.
[0068] FIG. 16 presents a graph of fuel flow rate vs. time. As shown, for this gasoline
containing no detergent additive, significant clogging was experienced in a very short
period of time, with a 50% loss in flow rate observed in as little as 10 minutes.
[0069] After substantial clogging was experienced, fuel flow was discontinued and air at
0.7 kg/cm
2 (10 psig) substituted. Heating was provided during this period and, in as little
as one minute later, significant cleaning was achieved, with flow rates returning
to prior levels.
Example 5
[0070] This example demonstrates that clogging is far less severe in the heated capillary
flow passage of Example 4, when a commercial-grade gasoline employing an effective
additive package is employed. As shown in FIG. 17, less than a 10% reduction in fuel
flow rate was experienced after running the device for nearly four hours.
Example 6
[0071] To compare various gasolines and the impact of detergent additives on clogging, five
test fuels were run in the heated capillary flow passage of Example 4. The fuels tested
included an unadditized base gasoline containing 300 ppm sulfur, an unadditized base
gasoline containing no sulfur, the sulfur-free base gasoline with a commercially available
after-market additive (additive A) added and the sulfur-free base gasoline with another
commercially available after-market additive (additive B) added.
[0072] As shown in FIG. 18, the additized fuels performed similarly, while unadditized fuels
experienced severe clogging in less than one hour of operation.
Example 7
[0073] This example compares the operation over time of a capillary flow passage operating
on an unadditized jet fuel (JP-8) to the same capillary flow passage operating on
an unadditized No. 2 diesel fuel operated in a capillary flow passage having an I.D.
of 0.036 cm (0.014 in) and a 5.1 cm (2 in) length. Fuel pressure was set to 1.1 kg/cm
2 (15 psig). Power was supplied to the capillary to achieve a level of R/R
o of 1.19; where R is the heated capillary resistance and R
o is the capillary resistance under ambient conditions.
[0074] As shown in FIG. 19, the fuels performed similarly over the first ten minutes of
operation, with the diesel fuel suffering more severe clogging thereafter.
Example 8
[0075] Tests were conducted to assess the efficacy of the oxidation cleaning technique on
a heated capillary flow passage using an unadditized, No. 2 diesel fuel known to produce
high levels of deposit formation. The capillary flow passage employed for these tests
was a 5.1 cm (2 in) long heated capillary tube constructed of stainless steel, having
an inner diameter of 0.036 cm (0.014 in). Fuel pressure was maintained at 1.1 kg/cm
2 (15 psig). Power was supplied to the capillary to achieve a level of R/R
o of 1.19; where R, once again, is the heated capillary resistance and R
o is the capillary resistance under ambient conditions.
[0076] FIG. 20 presents a graph of fuel flow rate vs. time. As shown, for this fuel containing
no detergent additive, significant clogging was experienced in a very short period
of time, with a 50% loss in flow rate observed in about 35 minutes of continuous operation.
[0077] In a second run, after five minutes of operation, fuel flow was discontinued and
air at 0.7 kg/cm
2 (10 psig) substituted for a period of five minutes. Heating was also provided during
this period. This procedure was repeated every five minutes. As shown in FIG. 20,
the oxidation cleaning process increased fuel flow rate in virtually every instance
and tended to slow the overall decline in fuel flow rate over time. However, the efficacy
of the process was somewhat less than was achieved using an unadditized gasoline,
as described in Example 4.
Example 9
[0078] Tests were conducted to assess the effect of a commercial grade anti-fouling detergent
additive blended with the No. 2 diesel fuel of Example 8 on fuel flow rate over time
in a heated capillary flow passage. The capillary flow passage employed for these
tests, once again, was a 5.1 cm (2 in) long heated capillary tube constructed of stainless
steel, having an inner diameter of 0.036 cm (0.014 in). Fuel pressure was maintained
at 1.1 kg/cm
2 (15 psig) and power was supplied to the capillary to achieve a level of R/R
o of 1.19.
[0079] FIG. 21 presents a comparison of fuel flow rate vs. time for the additized No. 2
diesel fuel and an unadditized diesel fuel. As shown, for the fuel containing no detergent
additive, significant clogging was experienced in a very short period of time, with
a 50% loss in flow rate observed in about 35 minutes of continuous operation, while
the same base fuel containing the detergent showed far less clogging over an extended
period of time.
[0080] While the subject invention has been illustrated and described in detail in the drawings
and foregoing description, the disclosed embodiments are illustrative and not restrictive
in character. All changes and modifications that come within the scope of the invention
are desired to be protected. As an example, a plurality of capillary passages can
be provided, with the fuel being passed through the passages in parallel when a higher
volume flow rate is desired.
1. A fuel injector (10) for vaporizing a liquid fuel for use in an internal combustion
engine, comprising:
(a) at least one capillary flow passage (12), said at least one capillary flow passage
(12) having a hydraulic diameter of less than 2 mm, an inlet end (14) and an outlet
end (16), said capillary flow passage (12) comprising a channel formed within a monolithic
body produced from a material selected from the group consisting of ceramics, polymers,
metals and composites thereof or a multi-layer ceramic body;
(b) a fluid control valve (18) for placing said inlet end (14) of said at least one
capillary flow passage (12) in fluid communication with the liquid fuel source (F)
and introducing the liquid fuel in a substantially liquid state;
(c) a heat source (20) arranged along said at least one capillary flow passage (12),
said heat source (20) operable to heat the liquid fuel in said at least one capillary
flow passage (12) to a level sufficient to change at least a portion thereof from
the liquid state to a vapor state and deliver a stream of substantially vaporized
fuel from said outlet end (16) of said at least one capillary flow passage (12); and
(d) means for cleaning deposits formed during operation of the fuel injector (10),
said means for cleaning deposits includes said fluid control valve (18), said fluid
control valve (18) operable for placing said at least one capillary flow passage (12)
in fluid communication with a solvent, enabling in-situ cleaning of said capillary
flow passage (12) when the solvent is introduced into said at least one capillary
flow passage (12).
2. The fuel injector of claim 1, wherein said capillary flow passage (12) is formed within
a ceramic body.
3. The fuel injector of claim 1 or 2, wherein said means for cleaning deposits includes
said fluid control valve (18) and a solvent control valve (26) for placing said at
least one capillary flow passage (12) in fluid communication with a solvent, said
solvent control valve (26) disposed at one end of said at least one capillary flow
passage (12), and wherein said solvent control valve (26) for placing said at least
one capillary flow passage (12) in fluid communication with a solvent is operable
to alternate between the introduction of liquid fuel and the introduction of solvent
into said capillary flow passage (12) and enable in-situ cleaning of said capillary
flow passage (12) when the solvent is introduced into said at least one capillary
flow passage (12).
4. The fuel injector of any preceding claim, wherein the solvent comprises liquid fuel
from the liquid fuel source (F) and wherein the heat source (20) is phased-out during
cleaning of said capillary flow passage (12).
5. The fuel injector of any preceding claim, further comprising a nozzle (560) to atomize
a portion of the liquid fuel.
6. The fuel injector of any preceding claim, further including a solenoid (28) to actuate
said fluid control valve (18) for placing said inlet end (14) in fluid communication
with the liquid fuel supply (F).
7. The fuel injector of any preceding claim, wherein said fluid control valve (18) comprises
a solenoid-activated valve stem having a valve element at said outlet end (16) of
said at least one capillary flow passage (12) to open and close said outlet end (16)
of said at least one capillary flow passage (12).
8. The fuel injector of any preceding claim, further comprising a non-capillary liquid
fuel flow passage, said non-capillary liquid fuel flow passage having an inlet end
and an outlet end, said inlet end in fluid communication with the liquid fuel supply
(F), said non-capillary liquid fuel flow passage having a fuel injector nozzle at
said outlet end.
9. The fuel injector of any preceding claim, wherein said heat source (20) includes a
resistance heater.
10. A fuel system for use in an internal combustion engine, comprising:
(a) a plurality of fuel injectors (10), each injector (10) including (i) at least
one capillary flow passage (12), said at least one capillary flow passage (12) having
a hydraulic diameter of less than 2 mm, an inlet end (14) and an outlet end (16),
said capillary flow passage (12) comprising a channel formed within a monolithic body
produced from a material selected from the group consisting of ceramics, polymers,
metals and composites thereof or a multi-layer ceramic body; (ii) a fluid control
valve (18) for placing said inlet end (14) of said at least one capillary flow passage
(12) in fluid communication with the liquid fuel source (F) and introducing the liquid
fuel in a substantially liquid state; (iii) a heat source (20) arranged along the
at least one capillary flow passage (12), said heat source (20) operable to heat the
liquid fuel in said at least one capillary flow passage (12) to a level sufficient
to change at least a portion thereof from the liquid state to a vapor state and deliver
a stream of substantially vaporized fuel from said outlet end (16) of said at least
one capillary flow passage (12); and (iv) means for cleaning deposits formed during
operation of the fuel injectors (10), said means for cleaning deposits includes said
fluid control valve (18), said fluid control valve (18) operable for placing said
at least one capillary flow passage (12) in fluid communication with a solvent, enabling
in-situ cleaning of said capillary flow passage (12) when the solvent is introduced
into said at least one capillary flow passage (12);
(b) a liquid fuel supply system in fluid communication with said plurality of fuel
injectors (10); and
(c) a controller to control the supply of fuel to said plurality of fuel injectors
(10).
11. The fuel system of claim 10, wherein said capillary flow passage (12) is formed within
a ceramic body.
12. The fuel system of claims 10 or 11, wherein the solvent comprises liquid fuel from
the liquid fuel source and wherein the heat source is phased-out during cleaning of
said capillary flow passage (12).
13. A method of delivering fuel to an internal combustion engine, comprising the steps
of:
(a) supplying liquid fuel to at least one capillary flow passage (12) of a fuel injector
(10), the at least one capillary flow passage (12) having a hydraulic diameter of
less than 2 mm;
(b) causing a stream of substantially vaporized fuel to pass through an outlet (16)
of the at least one capillary flow passage (12) by heating the liquid fuel in the
at least one capillary flow passage (12);
(c) delivering the vaporized fuel to a combustion chamber of the internal combustion
engine (2110); and
(d) cleaning periodically the at least one capillary flow passage (12) by placing
the at least one capillary flow passage (12) in fluid communication with a solvent,
enabling in-situ cleaning of the capillary flow passage (12) when the solvent is introduced
into the at least one capillary flow passage (12),
wherein the capillary flow passage (12) comprises a channel formed within a monolithic
body produced from a material selected from the group consisting of ceramics, polymers,
metals and composites thereof or a multi-layer ceramic body.
14. The method of claim 13, wherein the solvent comprises liquid fuel and wherein said
heating is phased-out during said cleaning step.
1. Kraftstoffeinspritzvorrichtung (10) zum Verdampfen eines flüssigen Kraftstoffs für
die Verwendung in einem Verbrennungsmotor, umfassend:
(a) zumindest einen Kapillarströmungsweg (12), wobei der zumindest eine Kapillarströmungsweg
(12) einen hydraulischen Durchmesser von weniger als 2 mm, eine Einlaßseite (14) und
eine Auslaßseite (16) aufweist, wobei der Kapillarströmungsweg (12) einen Kanal aufweist,
der in einem monolithischen Körper, der aus einem Material hergestellt ist, das aus
der Gruppe von Keramiken, Polymeren, Metallen und Verbundstoffen davon ausgewählt
ist, oder einem mehrschichtigen Keramikkörper ausgebildet ist;
(b) ein Flüssigkeitsregelventil (18), um die Einlaßseite (14) des zumindest einen
Kapillarströmungswegs (12) in Fluidverbindung mit der Quelle (F) für flüssigen Kraftstoff
zu bringen und den flüssigen Kraftstoff in einem im wesentlichen flüssigen Zustand
einzuführen;
(c) eine Wärmequelle (20), die entlang des zumindest einen Kapillarströmungswegs (12)
angeordnet ist, wobei die Wärmequelle (20) so betrieben werden kann, daß der flüssige
Kraftstoff in dem zumindest einen Kapillarströmungsweg (12) auf einen ausreichenden
Wert erwärmt wird, so daß zumindest ein Teil davon vom flüssigen Zustand in den dampfförmigen
Zustand übergeht und aus der Auslaßseite (16) des zumindest einen Kapillarströmungswegs
(12) ein Strom von im wesentlichen verdampftem Kraftstoff abgegeben wird; und
(d) eine Einrichtung zum Entfernen von Ablagerungen, die während des Betriebs der
Kraftstoffeinspritzvorrichtung (10) gebildet worden sind, wobei die Einrichtung zum
Entfernen von Ablagerungen das Flüssigkeitsregelventil (18) einschließt, wobei das
Flüssigkeitsregelventil (18) so betrieben werden kann, daß es den zumindest einen
Kapillarströmungsweg (12) in Fluidverbindung mit einem Lösungsmittel bringt, womit
das Reinigen des Kapillarströmungswegs (12) in situ möglich wird, wenn das Lösungsmittel
in den zumindest einen Kapillarströmungsweg (12) eingeführt wird.
2. Kraftstoffeinspritzvorrichtung nach Anspruch 1, wobei der Kapillarströmungsweg (12)
in einem Keramikkörper ausgebildet ist.
3. Kraftstoffeinspritzvorrichtung nach Anspruch 1 oder 2, wobei die Einrichtung zum Entfernen
von Ablagerungen das Flüssigkeitsregelventil (18) und ein Lösungsmittelregelventil
(26) umfaßt, um den zumindest einen Kapillarströmungsweg (12) in Fluidverbindung mit
einem Lösungsmittel zu bringen, wobei sich das Lösungsmittelregelventil (26) an einem
Ende des zumindest einen Kapillarströmungswegs (12) befindet und wobei das Lösungsmittelregelventil
(26) für die Fluidverbindung des zumindest einen Kapillarströmungswegs (12) mit einem
Lösungsmittel so betrieben werden kann, daß es zwischen dem Einführen von flüssigem
Kraftstoff und dem Einführen von Lösungsmittel in den Kapillarströmungsweg (12) wechselt
und das in situ Reinigen des Kapillarströmungswegs (12) möglich ist, wenn das Lösungsmittel
in den zumindest einen Kapillarströmungsweg (12) eingeführt wird.
4. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, wobei das Lösungsmittel
flüssigen Kraftstoff aus der Quelle (F) für flüssigen Kraftstoff umfaßt und wobei
die Wärmequelle (20) während der Reinigung des Kapillarströmungswegs (12) schrittweise
außer Betrieb genommen wird.
5. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, die ferner eine
Düse (560) zum Zerstäuben von einem Teil des flüssigen Kraftstoffs umfaßt.
6. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, die ferner einen
Solenoid (28) umfaßt, um das Flüssigkeitsregelventil (18) zu betätigen, damit die
Einlaßseite (14) in Fluidverbindung mit der Quelle (F) für flüssigen Kraftstoff gebracht
wird.
7. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, wobei das Flüssigkeitsregelventil
(18) einen von einem Solenoid betätigten Ventilschaft mit einem Ventilelement an der
Auslaßseite (16) des zumindest einen Kapillarströmungswegs (12) umfaßt, um die Auslaßseite
(16) des zumindest einen Kapillarströmungswegs (12) zu öffnen und zu verschließen.
8. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, die ferner einen
nicht-kapillaren Strömungsweg für flüssigen Kraftstoff umfaßt, wobei dieser nicht-kapillare
Strömungsweg für flüssigen Kraftstoff eine Einlaßseite und eine Auslaßseite hat, wobei
die Einlaßseite in Fluidverbindung mit der Quelle (F) für flüssigen Kraftstoff steht,
wobei der nicht-kapillare Strömungsweg für flüssigen Kraftstoff an der Auslaßseite
eine Kraftstoffeinspritzdüse aufweist.
9. Kraftstoffeinspritzvorrichtung nach einem der vorstehenden Ansprüche, wobei die Wärmequelle
(20) eine Widerstandsheizeinrichtung einschließt.
10. Kraftstoffsystem für die Verwendung in einem Verbrennungsmotor, umfassend:
(a) eine Vielzahl von Kraftstoffeinspritzvorrichtungen (10), wobei jede Einspritzvorrichtung
(10) folgendes einschließt: (i) zumindest einen Kapillarströmungsweg (12), wobei der
zumindest eine Kapillarströmungsweg (12) einen hydraulischen Durchmesser von weniger
als 2 mm, eine Einlaßseite (14) und eine Auslaßseite (16) aufweist, wobei der Kapillarströmungsweg
(12) einen Kanal aufweist, der in einem monolithischen Körper, der aus einem Material
hergestellt ist, das aus der Gruppe von Keramiken, Polymeren, Metallen und Verbundstoffen
davon ausgewählt ist, oder einem mehrschichtigen Keramikkörper ausgebildet ist; (ii)
ein Flüssigkeitsregelventil (18), um die Einlaßseite (14) des zumindest einen Kapillarströmungswegs
(12) in Fluidverbindung mit der Quelle (F) für flüssigen Kraftstoff zu bringen und
den flüssigen Kraftstoff in einem im wesentlichen flüssigen Zustand einzuführen; (iii)
eine Wärmequelle (20), die entlang des zumindest einen Kapillarströmungswegs (12)
angeordnet ist, wobei die Wärmequelle (20) so betrieben werden kann, daß der flüssige
Kraftstoff in dem zumindest Kapillarströmungsweg (12) auf einen ausreichenden Wert
erwärmt wird, so daß zumindest ein Teil davon vom flüssigen Zustand in den dampfförmigen
Zustand übergeht und aus der Auslaßseite (16) des zumindest einen Kapillarströmungswegs
(12) ein Strom von im wesentlichen verdampftem Kraftstoff abgegeben wird; und (iv)
eine Einrichtung zum Entfernen von Ablagerungen, die während des Betriebs der Kraftstoffeinspritzvorrichtungen
(10) gebildet worden sind, wobei die Einrichtung zum Entfernen von Ablagerungen das
Flüssigkeitsregelventil (18) einschließt, wobei das Flüssigkeitsregelventil (18) so
betrieben werden kann, daß es den zumindest einen Kapillarströmungsweg (12) in Fluidverbindung
mit einem Lösungsmittel bringt, womit das Reinigen des Kapillarströmungswegs (12)
in situ möglich wird, wenn das Lösungsmittel in den zumindest einen Kapillarströmungsweg
(12) eingeführt wird.
(b) ein Zuführungssystem für flüssigen Kraftstoff in Fluidverbindung mit der Vielzahl
von Kraftstoffeinspritzvorrichtungen (10); und
(c) einen Regler, um die Zufuhr von Kraftstoff zu dieser Vielzahl von Kraftstoffeinspritzvorrichtungen
(10) zu steuern.
11. Kraftstoffsystem nach Anspruch 10, wobei der Kapillarströmungsweg (12) im Inneren
eines Keramikkörpers ausgebildet ist.
12. Kraftstoffsystem nach den Ansprüchen 10 oder 11, wobei das Lösungsmittel flüssigen
Kraftstoff aus der Quelle für flüssigen Kraftstoff umfaßt und wobei die Wärmequelle
während der Reinigung des Kapillarströmungswegs (12) schrittweise außer Betrieb genommen
wird.
13. Verfahren, um einem Verbrennungsmotor Kraftstoff zuzuführen, das die folgenden Schritt
aufweist:
(a) Versorgen von zumindest einem Kapillarströmungsweg (12) einer Kraftstoffeinspritzvorrichtung
(10) mit flüssigem Kraftstoff, wobei der zumindest eine Kapillarströmungsweg (12)
einen hydraulischen Durchmesser von weniger als 2 mm aufweist;
(b) Bewirken, daß ein Strom von im wesentlichen verdampftem Kraftstoff durch einen
Auslaß (16) des zumindest einen Kapillarströmungswegs (12) gelangt, indem der flüssige
Kraftstoff in dem zumindest einen Kapillarströmungsweg (12) erwärmt wird;
(c) Leiten des verdampften Kraftstoffs zu einer Verbrennungskammer des Verbrennungsmotors
(2110); und
(d) periodisches Reinigen des zumindest einen Kapillarströmungswegs (12), indem der
zumindest eine Kapillarströmungsweg (12) in Fluidverbindung mit einem Lösungsmittel
gebracht wird, womit das Reinigen des Kapillarströmungswegs (12) in situ möglich wird,
wenn das Lösungsmittel in den zumindest einen Kapillarströmungsweg (12) eingeführt
wird;
wobei der Kapillarströmungsweg (12) einen Kanal umfaßt, der in einem monolithischen
Körper, der aus einem Material erzeugt ist, das aus der Gruppe von Keramiken, Polymeren,
Metallen und Verbundstoffen davon ausgewählt ist, oder einem mehrschichtigen Keramikkörper
ausgebildet ist.
14. Verfahren nach Anspruch 13, wobei das Lösungsmittel flüssigen Kraftstoff umfaßt und
das Erwärmen während des Reinigungsschritts schrittweise abgeschaltet wird.
1. Injecteur (10) de carburant permettant de vaporiser un carburant liquide destiné à
un moteur à combustion interne, comprenant :
(a) au moins un passage d'écoulement capillaire (12), le ou chaque passage d'écoulement
capillaire (12) ayant un diamètre hydraulique inférieur à 2 mm, une extrémité d'entrée
(14) et une extrémité de sortie (16), ledit passage d'écoulement capillaire (12) comprenant
un canal formé dans un corps monolithique obtenu à partir d'un matériau choisi dans
l'ensemble constitué de céramiques, de polymères, de métaux et de composites de ceux-ci,
ou dans un corps céramique multicouche ;
(b) une soupape (18) de régulation du fluide permettant de placer ladite extrémité
d'entrée (14) du ou de chaque passage d'écoulement capillaire (12) en communication
fluidique avec la source (F) de carburant liquide et d'introduire la carburant liquide
dans un état sensiblement liquide ;
(c) une source (20) de chaleur disposée le long du ou de chaque passage d'écoulement
capillaire (12), ladite source (20) de chaleur étant à même de chauffer le carburant
liquide dans le ou chaque passage d'écoulement capillaire (12), à un niveau suffisant
pour faire passer au moins une partie de ce carburant de l'état liquide à l'état vapeur
et pour produire un jet de carburant sensiblement vaporisé à partir de ladite extrémité
de sortie (16) du ou de chaque passage d'écoulement capillaire (12) ;
(d) et un moyen permettant de nettoyer des dépôts formés pendant le fonctionnement
de l'injecteur (10) de carburant, ledit moyen de nettoyage de dépôts comprenant ladite
soupape (18) de régulation de fluide, ladite soupape (18) de régulation de fluide
étant à même de mettre le ou chaque passage d'écoulement capillaire (12) en communication
fluidique avec un solvant, ce qui permet un nettoyage in situ dudit passage d'écoulement capillaire (12) lorsque le solvant est introduit dans
le ou chaque passage d'écoulement capillaire (12).
2. Injecteur de carburant selon la revendication 1, dans lequel ledit passage d'écoulement
capillaire (12) est formé dans un corps en céramique.
3. Injecteur de carburant selon la revendication 1 ou 2, dans lequel ledit moyen de nettoyage
comprend ladite soupape (18) de régulation de fluide et une soupape (26) de régulation
de solvant afin de mettre le ou chaque passage d'écoulement capillaire (12) en communication
fluidique avec un solvant, ladite soupape (26) de régulation de solvant se situant
au niveau d'une extrémité du ou de chaque passage d'écoulement capillaire (12), et
dans lequel ladite soupape (26) de régulation de solvant permettant de mettre le ou
chaque passage d'écoulement capillaire (12) en communication fluidique avec un solvant
peut fonctionner de manière à alterner entre l'introduction de carburant liquide et
l'introduction de solvant dans ledit passage d'écoulement capillaire (12) et permettre
un nettoyage in situ dudit passage d'écoulement capillaire (12) quand le solvant pénètre dans le ou chaque
passage d'écoulement capillaire (12).
4. Injecteur de carburant selon l'une quelconque des revendications précédentes, dans
lequel le solvant comporte du carburant liquide issu de la source (F) de carburant
liquide, et dans lequel la source (20) de chaleur est réduite progressivement pendant
le nettoyage dudit passage d'écoulement capillaire (12).
5. Injecteur de carburant selon l'une quelconque des revendications précédentes, comprenant
en outre un gicleur (560) permettant d'atomiser une partie du carburant liquide.
6. Injecteur de carburant selon l'une quelconque des revendications précédentes, comprenant
en outre un solénoïde (28) destiné à actionner ladite soupape (18) de régulation de
fluide, afin de mettre ladite extrémité d'entrée (14) en communication fluidique avec
la source (F) de carburant liquide.
7. Injecteur de carburant selon l'une quelconque des revendications précédentes, dans
lequel ladite soupape (18) de régulation de fluide comprend une tige de soupape actionnée
par le biais d'un solénoïde comportant un élément formant soupape au niveau de ladite
extrémité de sortie (16) du ou de chaque passage d'écoulement capillaire (12), afin
d'ouvrir et de fermer ladite extrémité de sortie (16) du ou chaque passage d'écoulement
capillaire (12).
8. Injecteur de carburant selon l'une quelconque des revendications précédentes, comprenant
en outre un passage d'écoulement de carburant liquide non capillaire, ledit passage
d'écoulement de carburant liquide non capillaire présentant une extrémité d'entrée
et une extrémité de sortie, ladite extrémité d'entrée étant en communication fluidique
avec la source (F) de carburant liquide, ledit passage d'écoulement de carburant liquide
non capillaire présentant un gicleur d'injecteur de carburant au niveau de ladite
extrémité de sortie.
9. Injecteur de carburant selon l'une quelconque des revendications précédentes, dans
lequel ladite source (20) de chaleur comprend un dispositif de chauffage à résistance.
10. Système de carburation pour utilisation dans un moteur à combustion interne, comprenant
:
(a) une pluralité d'injecteurs (10) de carburant, chaque injecteur (10) contenant
(i) au moins un passage d'écoulement capillaire (12), le ou chaque passage d'écoulement
capillaire (12) ayant un diamètre hydraulique inférieur à 2 mm, une extrémité d'entrée
(14) et une extrémité de sortie (16), ledit passage d'écoulement capillaire (12) comprenant
un canal formé à l'intérieur d'un corps monolithique obtenu à partir d'un matériau
choisi dans un ensemble constitué de céramiques, de polymères, de métaux et de composites
de ceux-ci ou d'un corps céramique multicouches ; (ii) une soupape (18) de régulation
du fluide permettant de placer ladite extrémité d'entrée (14) du ou chaque passage
d'écoulement capillaire (12) en communication fluidique avec la source (F) de carburant
liquide et d'introduire le carburant liquide dans un état sensiblement liquide ;
(iii) une source (20) de chaleur disposée le long du ou de chaque passage d'écoulement
capillaire (12), ladite source (20) de chaleur étant à même de chauffer le carburant
liquide dans le ou chaque passage d'écoulement capillaire (12), à un niveau suffisant
pour faire passer au moins une partie de ce carburant de l'état liquide à l'état vapeur,
et pour produire un jet de carburant sensiblement vaporisé à partir de ladite extrémité
de sortie (16) du ou de chaque passage d'écoulement capillaire (12) ; et (iv) un moyen
permettant de nettoyer des dépôts formés pendant le fonctionnement des injecteurs
(10) de carburant, ledit moyen de nettoyage des dépôts comprenant ladite soupape (18)
de régulation de fluide, ladite soupape (18) de régulation de fluide étant à même
de mettre le ou chaque passage d'écoulement capillaire (12) en communication fluidique
avec un solvant, ce qui permet un nettoyage in situ dudit passage d'écoulement capillaire (12) lorsque le solvant est introduit dans
le ou chaque passage d'écoulement capillaire (12) ;
(b) un système d'alimentation en carburant liquide, en communication fluidique avec
ladite pluralité d'injecteurs (10) de carburant ;
(c) et un régulateur permettant de réguler l'alimentation en carburant vers ladite
pluralité d'injecteurs (10) de carburant.
11. Système de carburation selon la revendication 10, dans lequel ledit passage d'écoulement
capillaire (12) est formé dans un corps en céramique.
12. Système de carburation selon la revendication 10 ou 11, dans lequel le solvant comprend
du carburant liquide issu de la source de carburant liquide, et dans lequel la source
de chaleur est réduite progressivement pendant le nettoyage dudit passage d'écoulement
capillaire (12).
13. Procédé d'introduction de carburant d'un moteur à combustion interne, comprenant les
étapes suivantes :
(a) fournir en carburant liquide au moins un passage d'écoulement capillaire (12)
d'un injecteur (10) de carburant, le diamètre hydraulique du ou chaque passage d'écoulement
capillaire (12) étant inférieur à 2 mm ;
(b) provoquer un jet de carburant sensiblement vaporisé à travers une sortie (16)
de ou chaque passage d'écoulement capillaire (12) par chauffage de ce carburant liquide
dans le ou chaque passage d'écoulement capillaire (12) ;
(c) introduire le carburant vaporisé dans une chambre de combustion du moteur à combustion
interne (2110) ; et
(d) nettoyer périodiquement le ou chaque passage d'écoulement capillaire (12) par
placement du ou de chaque passage d'écoulement capillaire (12) en communication fluidique
avec un solvant, ce qui permet un nettoyage in situ du passage d'écoulement capillaire (12) lorsque le solvant est introduit dans le
ou chaque passage d'écoulement capillaire (12),
dans lequel le passage d'écoulement capillaire (12) comprend un canal formé à l'intérieur
d'un corps monolithique obtenu à partir d'un matériau choisi dans un ensemble constitué
de céramiques, de polymères, de métaux et de composites de ceux-ci ou d'un corps céramique
multicouches.
14. Procédé selon la revendication 13, dans lequel le solvant comprend du carburant liquide
et dans lequel ledit chauffage est réduit progressivement pendant ladite étape de
nettoyage.