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Description  |
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FIELD OF THE INVENTION
This invention relates to fuel handling systems for internal combustion
engines and more particularly to a fuel handling system for a
fuel-injected marine internal combustion engine.
BACKGROUND OF THE INVENTION
Modern fuel-injected, fuel delivery systems are currently in use for
supplying fuel to marine internal combustion engines because fuel
injection precisely regulates fuel flow enabling accurate control of the
air and fuel mixture entering the engine. This improves engine
performance, particularly over the wide range of operating loads and
conditions typically encountered by a marine engine providing better fuel
efficiency while significantly reducing undesirable exhaust gas emissions.
During operation of a typical fuel handling system for a non-marine,
fuel-injected, internal combustion engine, an electrically powered, high
pressure fuel pump transfers liquid fuel from a remote tank, along a fuel
line, into a fuel rail that communicates the fuel to individual fuel
injectors of the engine. During engine operation, fuel not consumed by the
engine is returned to the remote tank while unburned fuel vapor is
typically remixed with air entering the engine or the fuel vapor is
returned to a vapor storage container until it can be later remixed with
engine intake air.
For the marine industry, exhaust gas emission regulations and the likely
future trend of these regulations have made it highly desirable, and even
virtually necessary, for engineers and designers to apply fuel injection
systems to marine internal combustion engines used to power boats and
other watercraft. However, because fuel handling for fuel injected fuel
delivery systems requires fuel to be supplied to the engine at a high
pressure of typically at least twenty pounds per square inch (PSI) or
more, Coast Guard safety regulations designed to prevent marine engine and
fuel handling system related fires and explosions have made use of
fuel-injection technology for marine applications a challenge.
To comply with these Coast Guard safety regulations, which limit the length
of pressurized fuel lines in marine fuel handling systems to no more than
twelve inches, fuel is delivered by the high pressure fuel pump to the
injectors from a fuel reservoir, referred to as a vapor separator, located
close to the engine. A lower pressure fuel pump transfers fuel, as it is
needed, from the remote fuel tank to the vapor separator so the high
pressure pump always has an adequate supply of liquid fuel to deliver to
the engine. Typically, to keep the length of the pressurized fuel line as
short as possible, the high pressure fuel pump, vapor separator and
pressurized fuel line are all carried by the engine and housed under its
cowling.
Since it is impractical and possibly unsafe to return unused fuel to the
remote fuel tank and because excess pressurized fuel not used by the
injectors must also have a short return line preferably to conform to
these same Coast Guard safety regulations, the reservoir also functions as
a vapor separator. To perform as a vapor separator, the reservoir has a
gas dome above a pool of liquid fuel in the reservoir. During operation,
unused fuel and vapor is typically returned from the engine to the
reservoir and vapor vented from the gas dome is mixed with air entering
the engine to be burned during engine operation. An example of such a
vapor separator is disclosed in U.S. Pat. No. 5,368,001.
Typically, pressurized fuel must be returned to the vapor separator because
excess fuel is supplied by the fuel pump to ensure an adequate supply and
fuel pressure at each fuel injector. In addition to pressurized fuel not
used by the fuel injectors, unburned liquid fuel, fuel vapor and air from
the engine are also returned to the separator. For example, in two-stroke
marine engine applications, fuel collected in an unburned fuel collection
system, called a puddle drain system, is periodically purged from the
engine into the vapor separator to prevent the engine from running rich
and thereby reducing its fuel economy and undesirably increasing exhaust
gas emissions.
Unfortunately, fuel is often returned to the reservoir under high pressure
as well as high velocity causing the returned fuel to undesirably foam in
the reservoir. Additionally, air and fuel vapor being returned to the
reservoir can stir up the pool of liquid fuel also causing fuel to foam
and vaporize. Fuel foaming is highly undesirable because it can interfere
with maintaining enough liquid fuel in the vapor separator for adequate
high pressure fuel pump operation. Should the amount of foam in the
reservoir become excessive, foam may be pumped to the engine resulting in
lean engine operation, stalling or, even worse, overheating of the engine
due to fuel starvation.
To reduce fuel foaming, a flat baffle constructed of solid sheet material
has been used in the past as a barrier to prevent any stream of returned
fuel, vapor and/or air from impinging against the liquid fuel in the vapor
separator. Unfortunately, returned fuel often foams as it impinges against
the solid baffle and this foam drops below into the pool of liquid fuel
because of a gap between the outer edge of the baffle and the sidewall of
the vapor separator. Additionally, fuel vapor and air returned to the
vapor separator can pass through this gap around the baffle and churn up
the liquid fuel, also causing foaming, while undesirably increasing fuel
vaporization.
Too much fuel vapor in the separator is also undesirable because it can
result in a great deal of fuel vapor being uncontrollably vented from the
separator into the intake manifold of the engine, thereby resulting in
rough engine operation, spark plug fouling, and increased exhaust gas
emissions. Moreover, for two-stroke engines at wide open throttle (WOT)
engine operating conditions, the puddle drain system can return a large
amount of air to the vapor separator, pressurizing the separator and
forcing an excess amount of fuel vapor to vent from the separator into the
intake manifold, further compounding these problems.
Complicated mechanisms have been developed in response to these problems.
To help control or at least reduce the amount of fuel vapor venting from
the separator back into the engine, there usually is a check valve in the
vent between the vapor separator and engine intake manifold. To better
control and typically reduce the amount of air under high velocity
returned by the puddle drain system, a complex mechanical valving system
cooperates with the throttle so it opens periodically at idle and low
speed engine operating conditions to return fuel and vapor and remains
closed at WOT to prevent overpressurizing the vapor separator helping to
ensure smoother engine operation.
Unfortunately, these mechanisms contribute additional cost to constructing
each fuel handling system because of the additional components and extra
assembly required. During manufacturing, this added complexity also can
increase the number of fuel handling systems that are rejected during
quality control inspection, requiring them to be expensively refurbished
or scrapped. Just as bad, mechanisms of this complexity can become dirty,
sticky or otherwise inoperable over time, reducing their effectiveness or
even adversely affecting engine operation, requiring servicing. Finally,
all of these mechanisms do not always suitably retard or prevent fuel
foaming and excessive fuel vaporization.
SUMMARY OF THE INVENTION
A fuel handling system for an internal combustion engine, such as a marine
outboard engine, having a vapor separator for receiving fuel under
relatively low pressure from a remote fuel tank and having a fuel pump for
delivering fuel under relatively high pressure to a fuel injector of the
engine while enabling fuel vapor in the separator to be returned to the
engine. The vapor separator has a housing with a top and bottom and a
sidewall defining a reservoir for receiving a pool of liquid fuel therein
while maintaining a gas dome above the liquid fuel. The vapor separator
has an inlet for receiving fuel from the remote fuel tank, an outlet in
communication with an inlet of the fuel pump enabling fuel to be withdrawn
from the liquid fuel pool, at least one fuel return enabling fuel not used
by the engine to be returned to the vapor separator, and a vapor vent for
enabling fuel vapor to be removed from the gas dome and vented to the
engine. To retard and preferably prevent liquid fuel in the pool from
foaming while encouraging separation of liquid fuel from any return stream
of fuel, vapor and/or air received from the engine, the vapor separator
has a perforate baffle between any such return and the liquid fuel pool.
To controllably admit fuel from the remote tank into the vapor separator,
the inlet has a valve that cooperates with a float for maintaining a
desired liquid fuel level in the fuel pool so that the fuel pump always
has an adequate supply of fuel during operation. If desired, the vapor
separator can have a return from the fuel rail or a return from a pressure
regulator downstream of the fuel pump for returning excess pressurized
fuel to the vapor separator. Preferably, the separator also has a return
for receiving fuel and vapor not consumed by the engine, such as from a
puddle drain fuel return system of a two-stroke engine.
To retard and preferably prevent fuel foaming while encouraging separation
of liquid fuel from any return stream by enabling liquid fuel to
controllably pass through the perforate baffle and drop into the liquid
fuel pool below the baffle, the baffle has through-openings or
perforations for allowing liquid fuel to pass through while deflecting any
return stream away from the liquid fuel pool in the separator. Preferably,
liquid fuel returned to the vapor separator "percolates" downwardly
through the openings in the baffle thereby retarding any fuel foam on or
above the baffle from passing through the baffle and dropping into the
fuel pool. Preferably, at least a portion of the baffle is inclined to a
return stream and preferably the surface of the baffle is substantially
non-planar to further encourage separation of liquid fuel entrained in any
return stream while absorbing at least some momentum of each stream and
deflecting each stream away from the liquid fuel pool. To create such a
non-planar baffle, the baffle is preferably constructed of corrugated
sheet, wire cloth, wire mesh or screen.
Preferably, the periphery of the baffle bears against the separator
sidewall to prevent any return stream from passing around the baffle and
impinging against the liquid fuel pool thereby preventing foaming and fuel
vaporization. If the fuel pump is received in the vapor separator and
through the baffle, the baffle preferably bears against the outer housing
of the pump to prevent any return stream from passing between the baffle
and the pump.
Preferably, the baffle divides the gas dome into an upper dome and a lower
dome and the return stream creates a pressure differential across the
baffle. This pressure differential causes the lower gas dome to be at
least slightly pressurized for encouraging condensation of fuel vapor in
the dome into liquid fuel while preventing fuel vaporization and retarding
excess fuel vapor from being vented to the engine thereby preventing the
engine from running rich and emitting undesirable exhaust gases.
Objects, features and advantages of this invention are to provide a fuel
handling system which enables fuel to be transported from a remote tank
under low pressure and pressurized at the engine for supplying highly
pressurized fuel to a fuel injector of an internal combustion engine, has
a vapor separator with a baffle therein for preventing any stream of
returned fuel, vapor and/or air from directly impinging against a pool of
liquid fuel in the separator for retarding fuel foaming and thereby
preferably preventing fuel foaming from adversely affecting fuel pump
operation and minimizing vaporization of liquid fuel in the separator,
pressurizing at least a portion of the gas dome to prevent an excessive
amount of fuel vapor from being uncontrollably Vented to the engine for
preventing rich engine operation while encouraging condensation of fuel
vapor into liquid fuel, reducing undesirable exhaust gas emissions and
increasing fuel economy, encouraging separation of liquid fuel entrained
in any vapor or gas stream returned to the separator, can be easily
mounted under the cowling of a marine outboard engine in close proximity
to the engine for enabling compliance with Coast Guard regulations
requiring pressurized fuel lines to have a length no greater than twelve
inches, and is of compact construction, and is rugged, durable, of simple
design, of economical manufacture and easy to assemble and use.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects, features and advantages of this invention will be
apparent from the following detailed description of the best mode,
appended claims and accompanying drawings in which:
FIG. 1 illustrates a fuel handling system having a perforate baffle of this
invention for preventing excess fuel vaporization and retarding fuel
foaming;
FIG. 2 is a sectional view of the vapor separator taken along line 2--2 of
FIG. 1 illustrating a top view of the baffle;
FIG. 3 is an enlarged fragmentary view of that portion of FIG. 1 of the
baffle and vapor separator enclosed by the circle 3 illustrating in more
detail the construction and arrangement of the baffle in the separator;
FIG. 4 is a sectional view of the fuel handling system having a fuel pump
within the separator and received through a second baffle embodiment;
FIG. 5 is a sectional view of the vapor separator taken along line 5--5 of
FIG. 4 illustrating more clearly the second baffle; and
FIG. 6 is a fragmentary view on an enlarged scale of that portion of FIG. 5
of the vapor separator and baffle enclosed by the circle 5 and
illustrating in more detail the construction of the second baffle.
DETAILED DESCRIPTION
With reference to the drawings, FIGS. 1-3 illustrate a fuel handling system
20 having a vapor separator 22 of this invention for receiving fuel under
low pressure from a remote source, such as a fuel tank 24, and delivering
the fuel under high pressure to a fuel injector 26 of an internal
combustion engine 28. The vapor separator 22 also receives unused and
excess liquid fuel and fuel vapor from the engine 28 and vents fuel vapor
from the separator 22 to the engine 28 for mixing it with air entering the
engine 28 where it is later burned during engine operation. To retard and
preferably prevent returned fuel from undesirably foaming and displacing
liquid fuel in the separator 22 with foam, the vapor separator 22 has a
baffle 30 between any fuel return and the liquid fuel in the separator 22.
Preferably, the engine 28 is a two-stroke or four-stroke fuel injected,
internal combustion engine used for marine applications, such as an
inboard or outboard engine for a boat. As is shown in FIG. 1, the engine
28 has an intake manifold 32 for receiving air and directing it into the
engine 28 to be mixed with fuel to be combusted during engine operation.
Fuel from the vapor separator 22 is delivered under high pressure by a
fuel pump 34 to a fuel rail 36 on the engine 28 that communicates fuel to
each injector 26. During engine operation, each injector 26 sprays a
precise amount of fuel from the rail 36 that is mixed with air from the
intake manifold 32 before it enters the engine 28 to ensure efficient
engine operation.
As is shown in block diagram form in FIG. 1, the remote fuel tank 24 is
connected by a fuel line 38 to the vapor separator 22. Although not shown
in the drawings, a low pressure fuel pump, that preferably is directly
powered by the engine 28, draws fuel from the tank 24 and pumps it under
relatively low pressure to the vapor separator 22. If the engine 28 is a
two-stroke engine, the low pressure pump preferably is a pulse-type fuel
pump powered by changes in engine crankcase pressure during engine
operation. If the engine is a four-stroke engine, the fuel pump preferably
is a mechanical fuel pump that is driven by the engine camshaft or
distributor shaft.
To supply fuel from the vapor separator 22 to the engine 28, the high
pressure fuel pump 34 draws liquid fuel from the separator 22 and
transports it through a fuel line 40 to the fuel rail 36 of the fuel
injection system. Preferably, there is also a pressure regulator 42
downstream of the fuel pump 34 and upstream of the fuel rail 36 for
regulating fuel pressure to each injector 26. To return excess fuel not
required by the injectors 26, the pressure regulator 42 has a fuel return
line 44 that returns the excess fuel to the vapor separator 22. Although
FIG. 1 illustrates fuel being returned from the pressure regulator 42, the
vapor separator 22 and baffle 30 of this invention could also be used with
a system having a fuel return line from the fuel rail 36 to the vapor
separator 22. Alternatively, the vapor separator 22 and baffle 30 of this
invention are also well suited for use with a returnless, fuel injected,
fuel delivery system.
A high pressure fuel pump having this construction capable of supplying
fuel under a pressure of at least twenty pounds per square inch (PSI) is
disclosed in U.S. Pat. No. 5,248,223 assigned to the assignee hereof,
incorporated by reference herein, and to which reference may be had for a
more detailed background discussion of such pump structure and operation.
To enable fuel vapor to be vented from the vapor separator 22, there is a
vent line 46 from the vapor separator to the engine 28 to communicate fuel
vapor from the separator 22 to air entering the engine 28 through its
intake manifold 32 for being mixed with incoming air. Preferably, the vent
line 46 extends from the separator 22 to the intake manifold 32 for
enabling fuel vapor from the separator 22 to be mixed with the air
entering the engine. Preferably, there also is a return line 48 from the
engine 28 to the separator 22 for returning unused liquid fuel and vapor
from the engine 28 to the separator 22. If the engine 28 is a two-stroke
engine, the fuel return line 48 communicates with a puddle drain system 49
of the two-stroke engine, as is depicted in FIG. 1, for returning unburned
liquid fuel and fuel vapor to the separator 22.
The vapor separator 22 has a housing 50 with a top wall 52 and a bottom
wall 54 spaced apart by a sidewall 56 for defining a reservoir 57 for
containing a pool of liquid fuel 58 therein while maintaining a gas dome
60 holding a mixture of air and fuel vapor above the liquid fuel pool 58.
To admit fuel from the remote tank 24 and enable liquid fuel to be removed
from the reservoir 57, the vapor separator housing 50 has a fuel inlet
nipple 62 fluidtightly connected to the fuel line 38 from the tank 24 and
an outlet nipple 64 connected by a fuel line 66 to the inlet of the high
pressure fuel pump 34. The separator 22 also has an inlet nipple 68
sealingly connected to the return line 44 from the pressure regulator 42
and another inlet nipple 72 sealingly connecte | | |
