U.S. patent number 3,783,849 [Application Number 05/195,949] was granted by the patent office on 1974-01-08 for dual fuel system.
This patent grant is currently assigned to Ethyl Corporation. Invention is credited to Thomas Hugh Bramfitt.
United States Patent |
3,783,849 |
Bramfitt |
January 8, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
DUAL FUEL SYSTEM
Abstract
A fuel system for a spark ignited internal combustion engine
which feeds gasoline and a volatile gasoline fraction to the engine
has a volatile fuel generation means with an appropriate valve
switching system designed to allow operation of the engine on the
volatile fuel during start and warm-up and then switch to normal
fuel during warmed-up operation. The self-generation system
utilizes engine vacuum as an aid in vaporizing a portion of the
normal gasoline.
Inventors: |
Bramfitt; Thomas Hugh
(Pasadena, TX) |
Assignee: |
Ethyl Corporation (Richmond,
VA)
|
Family
ID: |
22723490 |
Appl.
No.: |
05/195,949 |
Filed: |
November 5, 1971 |
Current U.S.
Class: |
123/576;
123/179.16; 123/578 |
Current CPC
Class: |
F02M
13/06 (20130101); F02B 1/04 (20130101) |
Current International
Class: |
F02M
13/00 (20060101); F02M 13/06 (20060101); F02B
1/04 (20060101); F02B 1/00 (20060101); F02m
013/06 () |
Field of
Search: |
;123/2,3,179G,133,134,127 ;196/98,104 ;208/356,359,361,366 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Attorney, Agent or Firm: Johnson; Donald L. Sieberth; Jack
F. Pelton; James M.
Claims
I claim:
1. In a fuel system which feeds gasoline and a volatile gasoline
fraction to a spark ignited internal combustion engine during
selected periods of engine operation, the improvement comprising a
vacuum line connected at one end to a source of engine vacuum, a
vaporizing chamber connected by a liquid fuel line to a gasoline
tank, a vacuum chamber connected to the other end of said vacuum
line, said vacuum chamber comprising a lower section for collecting
the condensate and an upper section communicating with said engine
vacuum source by said vacuum line whereby the upper section of said
vacuum chamber is maintained under vacuum during operation of said
fuel system to produce said volatile gasoline fraction, said vacuum
chamber having a pervious vapor-liquid impingement separator means
whereby sid condensate is separated from any uncondensed vapor, a
vapor conduit connecting said vaporizing chamber with said vacuum
chamber, condensing means in said vapor conduit whereby the vapor
produced from said gasoline in said vaporizing chamber is
substantially completely condensed, producing a liquid volatile
gasoline fraction, a heater in heat exchange relationship with said
liquid fuel line whereby said gasoline is heated prior to entering
said vaporizing chamber thereby facilitating vaporization, a
pressure responsive valve mans connected to said liquid fuel line
and downstream of said heater, whereby a portion of said gasoline
is vaporized in response to a predetermined pressure drop across
said valve from the upstream side of said valve to the downstream
side of said valve caused by said engine vacuum, and a volatile
fuel storage tank having an inlet connected to said vacuum chamber
through pump means and one-way check valve means, an outlet
connected by a liquid volatile fuel conduit to the fuel induction
means of said engine, pressure relief valve means adapted to open
on reaching a predetermined pressure, and pressure regulating valve
means in said liquid volatile fuel conduit adapted to deliver
liquid volatile fuel to said fuel induction means at a preset
pressure.
2. In a fuel system which feeds gasoline and a volatile gasoline
fraction to a spark ignited internal combustion engine during
selected periods of engine operation, the improvement
comprising
a. a vacuum line connected at one end to a source of engine
vacuum,
b. a vaporizing chamber connnected by a liquid fuel line to a
gasoline tank,
c. a vacuum chamber connected to the other end of said vacuum
line,
d. a vapor conduit connecting said vaporizing chamber with said
vacuum chamber,
e. a heater in heat exchange relationship with said liquid fuel
line whereby said gasoline is heated prior to entering said
vaporizing chamber thereby facilitating vaporization,
f. a pressure responsive valve means connected to said liquid fuel
line and downstream of said heater, whereby a portion of said
gasoline is vaporized in repsonse to a predetermined pressure drop
across said valve to the downstream side of said valve caused by
said engine vacuum, and
g. a volatile fuel storage tank having an inlet connected to said
vacuum chamber through pump means and one-way check valve, an
outlet connected by a liquid volatile fuel conduit to the fuel
induction means of said engine, pressure relief valve means adapted
to open on reaching a predetermined pressure, and pressure
regulating valve means in said liquid volatile fuel conduit adapted
to deliver liquid volatile fuel to said fuel induction means at a
preset pressure.
3. In a fuel system which feeds gasoline and a volatile gasoline
fraction to a spark ignited internal combustion engine during
selected periods of engine operation, the improvement
comprising
a. a vacuum line connected at one end to a source of engine
vacuum;
b. a vaporizing chamber connected by a liquid fuel line to a
gasoline tank;
c. a vacuum chamber connected to the other end of said vacuum line,
said vacuum chamber comprising a lower section for collecting the
condensate and an upper section communicating with said engine
vacuum source by said vacuum line whereby the upper section of said
vacuum chamber is maintained under vacuum during operation of said
fuel system to produce said volatile gasoline fraction;
d. a vapor conduit connecting said vaporizing chamber with said
vacuum chamber;
e. a heater in heat exchange relationship with said liquid fuel
line whereby said gasoline is heated prior to entering said
vaporizing chamber thereby facilitating vaporization;
f. a pressure responsive valve means connected to said liquid fuel
line and downstream of said heater, whereby a portion of said
gasoline is vaporized in response to a predetermined pressure drop
across said valve from the upstream side of said valve to the
downstream side of said valve caused by said engine vacuum; and
g. a volatile fuel storage tank having an inlet connected to said
vacuum chamber through pump means and one-way check valve means, an
outlet connected by a liquid volatile fuel conduit to the fuel
induction means of said engine, pressure relief valve means adapted
to open on reaching a predetermined pressure, and pressure
regulating valve means in said liquid volatile fuel conduit adapted
to deliver liquid volatile fuel to said fuel induction means at a
preset pressure.
Description
BACKGROUND OF THE INVENTION
The exhaust gas of internal combustion engines contains various
amounts of unburned hydrocarbons, carbon monoxide, and nitrogen
oxides (NO.sub.x). Emission of these materials to the atmosphere is
undesirable. The problem is more acute in urban areas having a high
concentration of motor vehicles.
During recent years, researchers have investigated extensively
means of reducing exhaust emission. This research has been quite
fruitful. As a result, present-day automobiles emit but a fraction
of undesirable materials compared to those of less than a decade
ago. These improved results have come about through such means as
improved carburetion, ignition timing modifications, exhaust
recycle, exhaust manifold air injection, use of lean air/fuel
ratios, positive crankcase ventilation, and the like.
Despite the tremendous advances that have been made, further
improvements are desirable. Federal standards by 1975 are expected
to require reduction of emissions to only about 10 percent of the
level of 1970. A major obstacle in achieving further reduction in
exhaust emissions is the fact that the engine requires a richer
air/fuel mixture during start and warm-up. During this period
exhaust emissions of even the lowest emitting engine is appreciably
increased. In the case of carburetor induction engines, the
required richer air/fuel mixture is usually attained by placing a
choke valve in the air passage above the carburetor venturi, which
serves to restrict air flow. In most, but not all, gasoline-powered
vehicles the choke is automatically controlled by engine
temperature. As soon as the engine reaches an adequate operating
temperature (i.e., a temperature at which it can operate smoothly
without choking), the choke opens. In normal operation this takes
about 2-3 minutes.
In the past, attempts have been made to eliminate the need for this
rich operating warm-up period by operating the engine on liquid
petroleum gas (LPG) during the warm-up period and switching to
gasoline after operating temperature is attained. A drawback of
this system is that it requires the vehicle operator to obtain two
different kinds of fuel--gasoline and LPG. Of even greater
consequence is the fact that the use of a liquid an a gaseous fuel
requires a separate metering system for each fuel. For example, the
LPG fuel system is separate from the gasoline fuel system and
provides LPG vaporization, pressure regulation, and finally, vapor
induction into the intake air stream through a separate metering
jet. Because of this, the system using LPG fuel is considered
impractical.
An object of the present invention is to provide a fuel induction
system that results in lower exhaust emissions. A further object is
to provide a fuel induction system that allows an engine to start
and warm-up without the necessity of operating the engine at a rich
air/fuel ratio. A still further object of the invention is to
provide a novel liquid fuel system with self-generation of the more
volatile liquid fuel from the normal gasoline fuel, thus
eliminating the necessity of the vehicle operator obtaining two
separate fuels. Another object is to provide a method of operating
a gasoline engine in a manner that will result in reduced exhaust
emissions.
SUMMARY OF THE INVENTION
The present invention in its broadest aspect relates to a novel
fuel system for a spark ignited internal combustion engine
(hereinafter simply referred to as an engine) with a
self-generation system for producing a liquid hydrocarbon fuel of
the lower gasoline boiling range referred to hereafter as a
"volatile gasoline fraction" and the method of accomplishing the
generation of the volatile gasoline fraction in the engine fuel
system. Therefore, this invention provides in a novel fuel system a
vacuum line connected to a source of engine vacuum, vaporizing
means in communication with said vacuum line whereby a portion of
the liquid hydrocarbon fuel of the gasoline boiling range, referred
to hereafter as gasoline, is vaporized, vapor-liquid separator
means connected to said vaporizing means whereby the vapor produced
in said vaporizing means is separated from the residual liquid fuel
which is depleted in volatile components, and a volatile fuel
conduit for delivery of said vapor to the fuel induction means of
said engine for operating during a selected period of start and
warm-up. In a preferred aspect of the invention a heater is used to
aid vaporization. In another preferred aspect the vaporizing means
is responsive to a pressure difference caused by opening a valve in
the vacuum line and causing reduced pressure to develop in the
vaporizing means. When the pressure difference attains a
predetermined level, gasoline from the tank is drawn into the
vaporizing means and a portion thereof is volatilized. In another
preferred aspect of the invention condensing means are connected to
the vaporizing means whereby the vapor is substantially completely
condensed to form a liquid volatile gasoline fraction or
"condensate." In a further preferred aspect of the invention, a
vacuum chamber having a lower section and an upper section is
connected to the condensing means whereby the condensate is
collected in the lower section and pumped through a one-way check
valve to a volatile fuel storage tank; and the upper section is
connected to the source of engine vacuum and maintained under
substantially reduced pressure during operation of the volatile
fuel generation system.
Another broad aspect of this invention is the method of operating
an engine having a fuel system which feeds gasoline and a volatile
gasoline fraction to said engine, the improvement comprising using
engine vacuum to vaporize a portion of gasoline and separating the
vapor from the residual liquid thereby producing a volatile
gasoline fraction for operating said engine during a selected
period. In another preferred aspect of this invention, the vapor is
condensed forming condensate which is stored in a volatile fuel
storage container for delivery to the fuel induction means during
start and warm-up. A still further aspect of the invention is the
method wherein the residual liquid fuel from the vaporization which
is separated from the vapor and is depleted in volatile components
is stored in a volatile depleted fuel storage container for
delivery to the fuel induction means during warmed-up operation of
said engine. In another preferred aspect the method includes
heating the gasoline to aid vaporization. A still further preferred
aspect of the invention is the method of using engine vacuum
wherein the vacuum is supplied from either the intake manifold or a
venturi in a carburetor.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic of the basic dual liquid fuel system showing
a reservoir for both volatile fuel and normal gasoline and conduits
for delivering either through a switching valve to the fuel bowl of
the carburetor. Also shown is a carburetor drain conduit having a
valve which allows the carburetor to drain when the engine is
turned off.
FIG. 2 is a cross-section of a carburetor having separate fuel
bowls for the normal gasoline and the volatile fuel and interlocked
valves for switching from one fuel to the other. The drawing shows
the valves functioning to permit delivery of the fuel from the
volatile fuel bowl such as would occur during start and
warm-up.
FIG. 3 is a schematic representation of the self-generation system
for producing the volatile fuel in broad conceptual aspects showing
a fuel line leading into a vaporizer which is connected to a
vapor-liquid separator having a vacuum line, volatile fuel line,
and residual fuel line.
FIG. 4 is a schematic of the dual fuel system's volatile fuel
self-generation system including a vaporizing means, a vapor-liquid
separator having a condenser for the volatile fuel and a vacuum
chamber in which the vapor space is connected to the source of
engine vacuum.
FIG. 5 is a schematic of the dual liquid fuel system showing the
connection of the volatile fuel self-generation system of FIG. 4 to
a carburetor on an internal combustion engine. Fuel switching
valves are shown for delivery of either volatile fuel or normal
gasoline to the engine. Vent lines and pumps are shown.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a preferred embodiment of the invention is a
fuel delivery system for a gasoline operated spark ignited internal
combustion engine adapted to feed gasoline and a volatile gasoline
fraction to the engine having a gasoline tank 1 for gasoline and a
container for liquid hydrocarbon fuel of the lower gasoline boiling
range 2.
Gasoline is a mixture of hydrocarbons having a boiling range of
from about 80.degree.F to about 430.degree.F as measured by ASTM
method D-86. Of course, these mixtures can contain individual
constituents boiling above or below these figures. These
hydrocarbon mixtures contain aromatic hydrocarbons, saturated
hydrocarbons and olefinic hydrocarbons. The bulk of the hydrocarbon
mixture is obtained by refining crude petroleum by either straight
distillation or through the use of one of the many known refining
processes, such as thermal cracking, catalytic cracking, catalytic
hydroforming, catalytic reforming, and the like. Generally, the
final gasoline is a blend of stocks obtained from several refinery
processes. The final blend may also contain hydrocarbons made by
other procedures such as alkylate made by the reaction of C.sub.4
olefins and butanes using an acid catalyst, such as sulfuric acid
or hydrofluoric acid.
Preferred gasolines are those having a Research Octane Number of at
least 85. A more preferred Research Octane Number is 90 or greater.
It is also preferred to blend the gasoline such that it has a
content of aromatic hydrocarbons ranging from 10 to about 60 volume
percent, an olefinic hydrocarbon content ranging from 0 to about 30
volume percent, and a saturate hydrocarbon content ranging from
about 40 to 80 volume percent, based on the whole gasoline.
In order to obtain fuels having properties required by modern
automotive engines, a blending procedure is generally followed by
selecting appropriate blending stocks and blending them in suitable
proportions. The required octane level is most readily accomplished
by employing aromatics (e.g., BTX, catalytic reformate, or the
like), alkylate (e.g., C.sub.6.sub.-9 saturates made by reacting
C.sub.4 olefins with isobutane using a HF or H.sub.2 SO.sub.4
catalyst), or blends of different types.
The balance of the whole fuel may be made up of other components
such as other saturates, olefins, or the like. The olefins are
generally formed by using such procedures as thermal cracking,
catalytic cracking and polymerization. Dehydrogenation of paraffins
to olefins can supplement the gaseous olefins occurring in the
refinery to produce feed material for either polymerization or
alkylation processes. The saturated gasoline components comprise
paraffins and napthenes. These saturates are obtained from (1)
virgin gasoline by distillation (straight run gasoline), (2)
alkylation processes (alkylates), and (3) isomerization procedures
(conversion of normal paraffins to branched-chain paraffins of
greater octane quality). Saturated gasoline components also occur
in so-called natural gasoline. In addition to the foregoing,
thermally cracked stocks, catalytically cracked stocks and
catalytic reformates contain saturated components.
Utilization of non-hydrocarbon blending stocks or components in
formulating the fuels used in this invention is feasible and, in
some instances, may actually be desirable. Thus, use may be made of
methanol, tertiary butanol and other inexpensive, abundant and
non-deleterious oxygen-containing fuel components.
The normal gasoline may contain any of the other additives normally
employed to give fuels of improved quality, such as tetraalkyllead
antiknocks including tetramethyllead, tetraethyllead, mixed
tetraethyltetramethyllead, and the like. They may also contain
antiknock quantities of other agents such as cyclopentadienyl
nickel nitrosyl, methylcyclopentadienyl manganese tricarbonyl, and
N-methyl aniline, and the like. Antiknock promoters such as
tert-butyl acetate may be included. Halohydrocarbon scavengers such
as ethylene dichloride, ethylene dibromide and dibromo butane may
be added. Phosphorus-containing additives such as tricresyl
phosphate, methyl diphenyl phosphate, diphenyl methyl phosphate,
trimethyl phosphate, and tris(.beta.-chloropropyl)phosphate may be
present. Antioxidants such as 2,6-di-tert-butylphenol, 2,6-di-tert
butyl-p-cresol, phenylenediamines such as
N-iospropylphenylenediamine, and the like, may be present.
Likewise, the gasoline can contain dyes, metal deactivators, or any
of the additives recognized to serve some useful purpose in
improving the gasoline quality.
The liquid hydrocarbon fuel of the lower gasoline boiling range,
referred to as a volatile gasoline fraction, is a hydrocarbon
having a final boiling point below that of normal gasoline. In the
present invention it is not necessary to place an exact value on
this final boiling point and, in fact, it can vary when the novel
fuel system is used with different engines. The requirement is that
the volatile fuel have a final boiling point low enough such that
the particular engine to which the novel fuel system is connected
will start and operate smoothly during warm-up without resorting to
a richer air/fuel ratio than is required for operation at normal
operating temperature. This is not to say that the use of a richer
air/fuel ratio is excluded because under very cold conditions a
slightly richer mixture may be required, especially to start the
engine. This richer mixture is readily furnished by such means as
choking the engine. However, the amount of time that the enriched
air/fuel ratio is used will be substantially less than required
without the novel fuel system of this invention; and accordingly,
even when some choking is required, the overall exhaust emissions
will be still greatly reduced by the use of the novel fuel system
of this invention.
The optimum final boiling point for the volatile gasoline fraction
to be used in the novel fuel system on a particular engine is best
determined experimentally taking into account the conditions such
as temperature and humidity, etc., under which the engine will be
operated. A useful boiling range for the volatile gasoline fraction
is from about 60-300.degree.F. Especially good results are obtained
in most applications using a volatile fraction having a normal
boiling range of from about 70-150.degree.F (ASTM D-86). The most
preferred volatile fuel is made up of the light ends (low boilers)
obtained from normal gasoline. In fact, embodiments of this
invention, to be described in detail hereafter, include in the
novel liquid fuel system means for removing the light ends from
normal gasoline and using these as the volatile gasoline fraction
during start and warm-up.
Referring again to FIG. 1, the dual fuel system includes a liquid
fuel conduit 3 connecting gasoline tank 1 through fuel selector
valve 4 to fuel pump 5 which connects to fuel bowl 6 of carburetor
7. The carburetor shown is a single venturi type but the fuel
system is equally applicable to multiple venturi carburetors such
as those having two, three, or four venturi.
Volatile fuel tank 2 is connected by volatile liquid fuel conduit 8
to fuel selector valve 4 which connects through fuel pump 5 to fuel
bowl 6 of carburetor 7. As shown in FIG. 1, fuel selector valve 4
is set to deliver normal gasoline from gasoline tank 1 to
carburetor 7. By revolving the selector valve counter-clockwise, as
shown by the arrow, fuel selector valve 4 will function to deliver
volatile fuel from volatile fuel tank 2 to carburetor 7.
Fuel bowl 6 has a fuel drain 9 which can drain residual fuel from
the bowl 6 through drain conduit 10 to gasoline tank 1. Drain valve
11 in drain conduit 10 is shown closed and is opened when it is
desired to drain fuel bowl 6.
In operation, the embodiment shown in FIG. 1 functions as follows.
Starting with a cold engine, fuel selector switch 4 is set to open
the flow path from volatile fuel tank 2 through fuel pump 5 to fuel
bowl 6. Fuel selector valve 4 may be set manually, but is
preferably positioned automatically in response to engine
temperature. A temperature responsive bimetal switch can be used to
signal valve actuating means to set fuel selector valve 4 to supply
the proper fuel to fuel bowl 6 depending upon a predetermined
engine temperature. The bimetal switch can be positioned to respond
to engine temperature at any of several locations such as
carburetor temperature, coolant temperature, oil temperature, or
multiple bimetal switches can be used to respond to temperature at
more than one location, thus requiring more than one location to
attain a predetermined operating temperature before the circuit is
completed to signal the valve actuating means to switch fuel
selector valve 4 from one fuel to another. The predetermined
temperature should be such that when the selector valve 4 is
signalled to switch from delivering fuel from volatile fuel tank 2
to normal gasoline tank 1 the engine will operate smoothly with
little, or preferably no, enrichment in the air/fuel ratio by means
such as choking. This operating temperature need not be the final
normal operating temperature of the engine but, rather, an
intermediate temperature somewhere between the cold engine and the
final normal operating temperature. The operating temperature at
which selector valve 4 switches from volatile fuel to normal
gasoline approximates the same temperature at which the well-known
automatic choking in a conventional fuel system would be open
because, in essence, the delivery of the volatile fuel replaces, or
substantially replaces, the use of the choke.
When the engine starter is engaged, fuel pump 5 fills fuel bowl 6
with volatile fuel. This is delivered through fuel nozzle 12 to
carburetor venturi 13 where it is mixed with air and inducted into
the engine. By the use of the present fuel system, nozzle 12
delivers fuel at a leaner air/fuel ratio than would otherwise be
required to start the engine using normal gasoline. For example,
the engine can be started at air/fuel ratios of about 13-17:1
whereas conventional systems require a much richer ratio. Under
very adverse conditions, such as very low temperature, only minimal
enrichment may be required to allow the engine to start and operate
smoothly during warm-up.
When the engine reaches an operating temperature at which it can
operate smoothly on normal gasoline with little or no choking,
selector valve 4 is switched such that it closes the path from
volatile fuel tank 2 and opens the path from normal gasoline tank 1
such that fuel bowl 6 is supplied with normal gasoline. As
mentioned above, this can be accomplished manually but is
preferably accomplished automatically in response to engine
temperature.
After the engine has operated using normal gasoline and is turned
off fuel bowl 6 will contain residual normal gasoline. Once the
engine cools it will not start and run smoothly of this residual
normal gasoline without some enrichment of the air/fuel ratio--in
other words, some choking would be required. To avoid this, fuel
bowl 6 is preferably drained after each use so that on the next
start-up the initial fuel supplied to the carburetor will be
volatile fuel. This is accomplished by opening drain valve 11
allowing the residual normal gasoline in fuel bowl 6 to drain
through drain conduit 10 to normal gasoline tank 1. Optionally, the
fuel bowl could drain to some other container provided for that
purpose. Opening of drain valve 11 can be accomplished manually but
preferably it is made automatic. One method of accomplishing this
is to provide valve actuating means such as an electrical solenoid
which keep valve 11 closed when the engine electrical engine system
is turned on and open valve 11 when the ignition system is turned
off. By this means when the engine is again started, drain valve 11
will automatically close and either volatile fuel or normal
gasoline will be delivered to fuel bowl 6 depending upon engine
temperature.
Referring now to FIG. 2, another embodiment of the invention is
shown in which a dual fuel carburetor 20 is provided which has a
fuel bowl for normal gasoline 21 and a separate fuel bowl for
volatile fuel 22. Selection of fuel delivered to carburetor venturi
23 is accomplished by interlocked valves 24 and 25. The
interlocking provides that when one valve is open the other is
closed. As shown, valve 25 is open and volatile fuel is being
delivered to venturi 23 which would be the proper selection at
engine start-up and warm-up. When the engine attains operating
temperature, valve 25 is closed and valve 24 opens such that normal
gasoline is delivered to venturi 23.
In FIG. 2 each of fuel bowls 21 and 22 have individual fuel
delivery passages. In a similar arrangement the carburetor can be
modified such that only a single fuel delivery passage through a
main nozzle is provided for each venturi. This single nozzle is
supplied with fuel from either the volatile fuel bowl or the normal
gasoline bowl as required and the selection of which fuel is
delivered to the single nozzle is controlled by valves in the fuel
passage connecting the individual fuel bowls to the common nozzle.
These valves function in a manner similar to valves 24 and 25.
Referring to FIG. 3, the normal gasoline is taken from the gasoline
tank 38 by liquid fuel line 31 and enters the vaporizing means 32
where it is partially vaporized. The vapor and liquid are separated
in vapor-liquid separator 33, which is connected by vapor-liquid
line 34 to the vaporizing means 32. The vapor exits from
vapor-liquid separator 33 via volatile fuel line 35, which connects
with the fuel induction means (not shown) such as carburetor. The
liquid which is depleted in volatile fuel components is discharged
from the vapor-liquid separator means 33 via volatile-depleted fuel
line 36 and according to automatically or manually predetermined
conditions is either returned to the gasoline tank or delivered to
the fuel induction means. The vapor-liquid separator 33 must
operate under such conditions that the volatile fuel produced is
substantially completely condensed. Thus, the vacuum drawn on the
volatile fuel self-generating system by means of vacuum line 37
connected to the vaporizing means 32 through vapor-liquid separator
33 and to the engine is substantially free of vapor avoiding undue
richness of the air/fuel mixture, fuel economy losses, and fuel
metering problems.
From the foregoing it is readily apparent that a preferred
embodiment of this invention is a method of separating normal
gasoline into a volatile fraction and a portion depleted in
volatile components by partially vaporizing said gasoline under
vacuum, said vacuum being derived from the engine vacuum of a spark
ignited internal combustion engine. The volatile fraction is then
separated from the portion depleted in volatile components, i.e.,
the volatile depleted fuel, and the volatile fraction is used
during a selected period of engine operation. To facilitate the
production of the volatile fraction, the gasoline may be heated
prior to vaporization. The amount of vacuum should be that required
to vaporize from about 10 to about 50 weight percent of the normal
gasoline. Operating under varying conditions, such as idle, normal
cruising, and acceleration, engine vacuum can range from about 10
to about 21 inches of mercury or more depending on the particular
engine. While any convenient source of engie vacuum may be used,
for example, the carburetor venturi vacuum or intake manifold
vacuum, the latter is preferred. The portion depleted in volatile
components need not be completely depleted but the separation
should be such that a major portion of the volatile components in
normal gasoline are vaporized and separated in the vapor-liquid
separator.
It should also be clear that the vapor-liquid separator 33 of FIG.
3 may include a condenser which is slightly efficient, liquefying
the volatile portion substantially completely such that a liquid
seal is maintained between the engine vacuum source and the
vaporizing means. This may be accomplished, without limiting the
invention, by using refrigeration to obtain substantially complete
condensation of the vapor. For the amount and composition of
volatile fuel produced if from about 10 to about 50 weight percent
of the normal gasoline, the volatile fuel would condense at a
temperature from about 30 to about 50.degree.F. A convenient source
of refrigeration in an automobile is the air-conditioning system if
available. A person of ordinary skill in the art can suggest the
necessary arrangement of means to connect the condenser to the
automobile air-conditioning system. Other mechanical refrigeration
systems using either vapor-compression machines having
positive-displacement compressors, such as reciprocating, rotary,
or centrifugal compressors, steam jets or continuous or
intermittent absorption systems using, for example, ammonia or
lithium bromide as the refrigerant are typical.
The condenser is connected to a vacuum chamber which acts as a
collector for the condensate. The vacuum chamber has an upper
section which is essentially free vacuum, assuming that the
condenser has substantially completely liquefied the vapor and a
lower section which collects the condensate. The lower section can
be connected to a suitable pump which advances the condensate into
a volatile fuel storage container. The upper section is connected
by vacuum line to the source of engine vacuum. the volatile fuel
generation system is preferably operated when the vapor is
completely condensed. This prevents the vapor from entering the
engine vacuum causing fuel metering problems, unnecessarily rich
engine operation and penalizing fuel economy. However, a small
non-condensable fraction would not significantly affect operation
of the engine.
Referring to FIG. 4, a preferred embodiment of the invention is a
system for self-generation of a volatile fuel including a liquid
fuel conduit 42 connected to the gasoline tank 46C and to expansion
valve 41 through pump 44C and heater 40 in heat exchange
relationship with conduit 42 and adapted to heat the liquid fuel in
conduit 42. Expansion valve 41 is connected to vaporizing chamber
43 which has vapor conduit 44 connected to the vapor discharge
outlet, volatile-depleted fuel conduit 46 connected to the liquid
discharge outlet and a vent line 45B in which is located relief
valve 45A. Volatile-depleted fuel line 46 connects to gasoline tank
46C through pump 47 and one-way check valve 42C. Pump 47 is
actuated by liquid-level switch 40C in vaporizing chamber 43,
employing actuating means 41C. Located in vapor conduit 44 is
one-way check valve 45 which maintains flow in one direction only
through vapor conduit 44 to the inlet of condenser 48. Condenser 48
can conveniently be connected to the automobile air-conditioning
system (not shown) or any suitable refrigeration means (not shown)
to substantially completely condense the volatile fuel. The outlet
of condenser 48 is connected to vacuum chamber 49 which has upper
and lower sections. The lower section of vacuum chamber 49 is
connected to volatile fuel storage tank 40A by means of liquid fuel
conduit 43C containing pump 41A and one-way check valve 42A. The
upper section of vacuum chamber 49 communicates with a source of
engine vacuum by vacuum line 49A in which is located valve 49B.
Also, the upper section of vacuum chamber 49 has vent line 46B in
which is located pressure relief valve 46A and connects with the
gasoline tanke 46C or a suitable absorption system (not shown).
The volatile fuel storage container 40A has in addition to liquid
fuel conduit 43C from vacuum chamber 49, a liquid-level switch 43A
connected by actuating means 43B to valve 49B, liquid fuel conduit
44A in which is located pressure regulating valve 45C for delivery
of volatile fuel to the carburetor (not shown), and vent line 47B
having pressure relief valve 47A. The vent line is connected to the
gasoline tank 46C or any suitable absorption system (not shown). If
necessary, an auxiliary fuel pump may be inserted in conduit
44A.
In operation the volatile fuel self-generation system of this
preferred embodiment produces a volatile fuel from normal gasoline
in which normal gasoline from the gasoline tank 46C is fed through
liquid fuel line 42 by pump 44C to expansion valve 41 and is heated
by means of heater 40 located in heat exchange relationship with
liquid fuel line 42. The heater 40 may be an electrically operated
resistance heating coil wrapped around fuel line 42 or any other
suitable means for heating may be employed. The heater should be
adapted to bring the fuel to a temperature high enough to
facilitate vaporization when passed through expansion valve 41. For
best results the temperature should be from about 150.degree.F to
about 275.degree.F and preferably from about 175.degree.F to about
250.degree.F. The amount of fuel vaporized depends both on
temperature and pressure and the two are not independent variables.
For best vaporization, conditions should be set experimentally for
each particular engine. Typical examples of suitable heaters are
heat exchangers using hot engine coolant, direct or indirect
gas-fired heaters or the like. The expansion valve 41 may be a
pressure responsive valve allowing passage and partial vaporization
of liquid fuel delivered to it in response to a predetermined
pressure differential caused by application of engine vacuum and
pressure from pump 44C. The pressure level of expansion valve 41
should be set at a level to obtain the desired vaporization in
relation to the valve pressure can adapted vacuum. For best results
the pressure should not be less than about 30 psig and preferably
the expansion valve should be set for about 60 psig. The
vapor-liquid mixture passes into a vaporizing chamber 43 where the
vapor is drawn into vapor conduit 44 through one-way check vlve 45
in response to the decreased ressure caused by the engine vacuum.
The liquid separated from the vapor and depleted in volatile fuel
components is collected and drained from the vaporizing chamber 43
through volatile-depleted fuel line 46, and pump 47 responding to
liquid-level switch 40C, pumps the volatile depleted fuel from
vaporizing chamber 43 into the gasoline tank 46C through one-way
check valve 42C by means of conduit 46. Volatile-depleted fuel line
46 can be adapted to return the volatile-depleted fuel to the
gasoline tank 46C or with appropriate valving cna be adjusted to
deliver fuel to the carburetor or separate storage.
The vapor in vapor conduit 44 is delivered to the condener 48
adapted to substantially completely condense the vapor thus
producing the volatile fuel. The complete condensation prevents the
vapor from entering the vacuum source, which is the engine vacuum,
upsetting fuel/air mixtures and lowering fuel economy. As described
above, a preferred embodiment of the condenser 48 is a
refrigeration unit such as those used for an automotive
air-conditioning unit. The condensate is conducted into vacuum
chamber 48 where the liquid volatile fuel is collected in the lower
section for delivery by liquid volatile fuel conduit 43C to the
volatile fuel storage tank 40A by means of pump 41A through one-way
check valve 42A. The pump 41A can conveniently be controlled by a
conventional liquid-level controller (not shown) which is connected
through the side wall of vacuum chamber 49. The upper section of
vacuum chamber 49 is maintained under vacuum by means of vacuum
line 49A when vacuum valve 49B is in the open position and engine
vacuum is drawn on the system.
The opening or closing of vacuum valve 49B is controlled by the
liquid-level switch 43A in volatile fuel storage tank 40A and
signals the vacuum valve 49B through actuating means 43B. When the
amount of liquid volatile fuel falls below a predetermined level,
the switch 43A signals vacuum valve 49B via actuating means 43B,
the valve is opened and engine vacuun is drawn on the system
causing vaporization of the normal gasoline to produce more
volatile fuel. The liquid level in volatile fuel storage tank 40A
should be high enough to allow sufficient volatile fuel for cold
start and warm-up operations.
From the volatile fuel storage tank 40A the liquid volatile fuel is
delivered to the engine fuel induction means (not shown), such as a
conventional carburetor, by liquid fuel conduit 44A. Valve 45C
passes the liquid volatile fuel from the volatile fuel storage tank
by conduit 44A to the carburetor. A valve switching arrangement as
described in FIG. 5, but not shown here, determines when volatile
fuel is delivered to the carburetor.
For safety purposes relief valves 45A, 46A, and 47A are located in
vent lines 45B, 46B, and 47B, respectively, which are attached to
the vaporizing chamber 43, vacuum chamber 49, and volatile fuel
storage tank 40A, respectively. The vent lines can be connected to
the gasoline tank 46C or any other suitable vapor absorption system
used on the automobile.
From the foregoing description of FIG. 4, it can be seen that a
preferred embodiment of this invention is in a fuel system which
feeds gasoline and a volatile gasoline fraction to a spark ignited
internal combustion engine during selected periods of engine
operation, the improvement comprising
a. a vacuum line connected at one end to a source of engine
vacuum,
b. a vaporizing chamber connected by a liquid fuel line to a
gasoline tank,
c. a vacuum chamber connected to the other end of said vacuum line,
and
a vapor conduit connecting said vaporizing chamber with said vacuum
chamber. In another more preferred embodiment of the above fuel
system, the vaporizing chamber is pressure responsive whereby a
portion of said gasoline delivered to said chamber through said
liquid fuel line is vaporized in response to a predetermined
pressure drop from said liquid fuel line to said vaporizing chamber
caused by said engine vacuum. Another more preferred embodiment of
the above fuel system has heating means in heat exchange
relationship with said liquid fuel line whereby said gasoline is
heated prior to entering said vaporizing chamber. Another preferred
embodiment of this invention has a condensing means in said vapor
conduit whereby the vapor produced from said gasoline in said
vaporizing chamber is substantially completely condensed, producing
a liquid volatile gasoline fraction. In another preferred
embodiment the vacuum chamber comprises a lower section for
collecting the condensate and an upper section communicating with
said engine vacuum source by said vacuum line whereby the upper
section of said vacuum chamber is maintained under vacuum during
operation of said fuel system to produce said volatile gasoline
fraction. A most preferred embodiment has in the vacuum chamber a
pervious vapor-liquid impingement separator means whereby said
condensate is separated from any uncondensed vapor. In another most
preferred embodiment of this invention the fuel system has
a. a heater in heat exchange relationship with said liquid fuel
line whereby said gasoline is heated prior to entering said
vaporizing chamber thereby facilitating vaporization,
b. a pressure responsive valve means connected to said liquid fuel
line and downstream of said heater, whereby a portion of said
gasoline is vaporized in response to a predetermined pressure drop
across said valve from the upstream side of said valve to the
downstream side of said valve caused by said engine vacuum, and
c. a volatile fuel storage tank having an inlet connected to said
vacuum chamber through pump means and one-way check valve means, an
outlet connected by a liquid volatile fuel conduit to the fuel
induction means of said engine, pressure relief valve means adapted
to open on reaching a predetermined pressure, and pressure
regulating valve means in said liquid volatile fuel conduit adapted
to deliver liquid volatile fuel to said fuel induction means at a
preset pressure.
Referring to FIG. 5, a preferred embodiment of the invention is
shown in which the volatile fuel self-generation system of FIG. 4
is connected to a spark ignited internal combustion engine. FIG. 5
shows a normal gasoline tank 50 connected to the volatile fuel
self-generation system and also directly to the engine. A fuel
switching arrangement is provided to alternately deliver the normal
gasoline or the volatile gasoline fraction to the fuel induction
means, for example a carburetor, during selected periods of engine
operation. The normal gasoline tank 50 is connected to fuel inlet
52 of the carburetor by liquid fuel conduit 51 in which is located
fuel pump 53 and fuel selector valve 54. A second liquid fuel
conduit 55, connected to line 51 between pump 52 and valve 54,
connects gasoline tank 50 through heater 59C and expansion valve 56
to vaporizing chamber 57. Vaporizing chamber 57 is connected
through its top end closure by vapor conduit 58 through one-way
check valve 59 to the inlet of condenser 50A. The outlet of
condenser 50A connects to vacuum chamber 51A through volatile fuel
conduit 50B. Vacuum chamber 51A connects through its top end
closure to the engine intake manifold 52A by means of vacuum
conduit 54A in which valve 55A is located. In the event that the
vapor is not completely condensed in condenser 50A, vacuum chamber
51A can also contain a vapor-liquid impingement separator to
completely separate the liquid volatile fuel from said vapor. The
use of a vapor-liquid separator would prevent the vapor from
carrying entrained liquid volatile fuel with it into the engine
vacuum. Vacuum chamber 51A is also connected through its bottom end
closure by liquid volatile fuel conduit 53D to volatile fuel
storage tank 56A through pump 57A and one-way check valve 58A. The
bottom of volatile fuel storage tank 56A is connected by volatile
fuel conduit 59A through fuel selector valve 52B to the fuel inlet
52 of the carburetor. Located in conduit 59A is pump 51B. The top
of volatile fuel storage tank 56A is connected through pressure
relief valve 53B by a second vapor conduit 54B back to the gasoline
tank 50.
The vacuum chamber 51A is also connected through its top end
closure by a vapor 55B through pressure relief valve 56B to the
gasoline tank 50. Vaporizing chamber 57 is connected through its
top end closure to gasoline tank 50 by a vapor conduit 57B having
pressure relief valve 58B.
Vaporizing chamber 57 connects through its bottom end to the
gasoline tank 50 through volatile-depleted fuel conduit 59B having
located therein pump 52D and one-way check valve 50C. Located in
vaporizing chamber 57 is liquid-level switch 51C which is connected
to pump 52D by actuating means 51D and is adapted to close
volatile-depleted fuel line 59B.
Drain conduit 52C connects a drain outlet at the bottom of the
carburetor fuel bowl such as drain 9 in FIG. 2 through valve 53C to
fuel conduit 51 between gasoline tank 50 and fuel pump 53.
Bimetal thermal switch 54C is connected by actuating means 55C and
56C to valves 52B and 54 respectively.
Located inside volatile fuel storage tank 56A is liquid-level
switch 57C which connects through the side wall of tank 56A by
actuating means 58C to a valve 55A.
In operation starting with a cold engine turning the igntiion on
causes drain valve 53C to close. Thermal switch 54C responding to
the low engine temperature has valve 52B in an open position and
valve 54 in a closed position. Volatile gasoline fraction from
volatile fuel storage tank 56A is delivered through conduit 59A by
pressure regulating valve 51B in response to conventional
signalling means, such as by a standard float actuated fuel bowl
valve and fills the fuel bowl of the carburetor. Actuating the
starter starts the engine which operates without choking using the
volatile gasoline fraction.
After 2 to 3 minutes of operation the liquid engine coolant
temperature rises to a predetermined level at which experience has
shown the particular engine can operate on normal gasoline without
choking. Thermal switch 45C senses this temperature and actuates
valve 52B to close and valve 54 to open. During continued
operation, normal gasoline is supplied to the carburetor from
gasoline tank 50 through fuel conduit 51.
Assuming the liquid level in volatile fuel storage tank 56A has
dropped below a predetermined level (which level should provide
sufficient reserve volatile fuel to start and warm-up the engine),
liquid-level actuated switch 57C closes and by actuating means 58C
opens valve 55A. A vacuum from the engine manifold 52A is drawn on
the volatile fuel generation system which operates in the manner
described in FIG. 4.
Therefore, it can be seen that without limiting the invention, the
foregoing description provides a preferred embodiment of another
aspect of the invention which is in a fuel system for feeding
gasoline and a volatile gasoline fraction to a spark ignited
intneral combustion engine, comprising means for delivering
gasoline to the fuel induction means, means for delivering a
volatile gasoline fraction to said fuel induction means, fuel
switching means adapted to deliver said volatile gasoline fraction
to said fuel induction means during a selected period of engine
operation, and self-generation means for producing said volatile
gasoline fraction by vaporizing a portion of said gasoline in a
vaporizing chamber, separating the vapor and condensing said vapor
to form said volatile gasoline fraction, the improvement comprising
engine vacuum means connected by a vacuum conduit to said
self-generation means, vacuum valve means connected in said vacuum
conduit between said vacuum means and said self-generation means,
and means to signal said vacuum valve means to open causing a
reduction in pressure in said vaporizing chamber of said
self-generation means to produce said volatile gasoline fraction
and to close causing the production of said volatile gasoline
fraction to cease.
In a most preferred embodiment of the above fuel system the vacuum
means is the engine intake manifold of said engine. In another
preferred embodiment of the invention is the fuel system above
having in said self-generation menas a container for said volatile
gasoline fraction connected by a volatile liquid fuel conduit to
said fuel induction means. A still further preferred embodiment of
the invention is the fuel system above wherein said vacuum valve
means is controlled by a liquid-level sensing means in said
container for said volatile gasoline fraction whereby at a liquid
level below a predetermined level said liquid-level sensing means
causes said vacuum valve to open which causes a reduction in
pressure in said vaporizing chamber resulting in the vaporization
of a portion of said gasoline producing said volatile gasoline
fraction and at a liquid level above a predetermined level said
liquid-level sensing means causes said vacuum valve to close which
causes the production of said volatile gasoline fraction to
cease.
* * * * *