US2393125A - High pressure fuel carburetor - Google Patents

Description

Jan. 15, 1946. T A; 5T CLMR v 2,393,125

' HIGH PRESSURE FUEL CARBURETOR vAcuuM r. -VALVE MANUAL ENRICHING DEVICE so 23 33 mm 24 FUELINLET 1' 40A l2 P11, 4 l4 EXHAUST MANIFOLD INTAKE MANIFOLD INVENTOR T. STCLAI Q BY V ATTORNEY 1946- T. A. sT CLAIR HIGH PRESSURE FUEL CARBURETOR Filed N ov. 22}. 1941 2 Sheets-Sheet 2 AIR INLET FUEL mu;

INTAKE MANIFOLD INVENTOR T. A. ST CLAIR BY ;7/ M

A ORNE Patented Jan. 15, 1946 PATENT- OFFICE HIGH PRESSURE CARBURETOR Theodore A. st. Clair, Pontiac,.Mich., assignor to Phillips Petroleum Company, a corporation of Delaware Application November 22, 1941, Serial No. 420.115

\ I 3 Claims.

This invention relates to charge forming deces for internal combustion engines of the type adapted to handle fuels having a considerably higher vapor pressure than ordinary gasoline.

Prior to a comparatively recent period, carbureting arrangements for internal combustion engines were either adapted to handle fuel in an entirely liquid or gaseous state. The ordinary carburetor utilized in the present day automobile is designed entirely for the carburetion of liquid fuel. A further type of carburetor was developed inwhich the fuel was stored in a high pressure tank in liquid phase under pressure and on release of pressure the fuel was entirely converted to the gaseous phase and the arrangement provided means for mixing the gas in the proper proportion with air prior to introduction into the manifold. Quite recently devices have been proposed for the carburetion of fuel maintained in the liquid phase under pressure in high pressure storage tanks but which assume a liquid and a gaseous phase upon reduction to atmospheric pressure. Quite a number of devices have been suggested for the separation of fuels of the latter type into two phases and separately feeding the phases in the proper proportions to the gasoline engine. Some of these arrangements have been successful to some extent, but from a practical standpoint involve rather elaborate and costly apparatus. The ideal condition for the carburetion of high pressure fuels is one inof vapor lock in carburetors by the use of a heat exchanger located in the conduit for handling liquid fuel to the conventional carburetor inlet,

the heat exchanger having separate passages in heat exchange relation for the incoming liquid fuel and the vapor fuel after vaporization and mixture with the air stream at the carburetor Jet. This arrangement, although probably satisfactory for use with hydrocarbon fuels having a does not provide means for accomodating the wide pressurechange which these fuels undergo with change in atmospheric conditions. The present invention facilitates the carburetion of high pressure fuels in liquid phase and at relatively low pressure by cooling the fuel to a sufliciently low temperature that vaporization does not occur on pressure reduction.

An object of the present invention is to provide a liquid feed arrangement for the carburetion of fuels having a considerably higher vapor pressure than ordinary gasoline. A further ob- .iect 0f the present invention is the. maintenance of the fuel in liquid phase until discharged from the carburetor jet. Another object is'the' submission of an arrangement which, with minor adjustments. is capable of converting the con-w ventionalinternal combustion engines to the use of ,higher than normal vapor pressure fuel of high octane number and efliciency. A still further' object is the deliverance of the high pressure fuel to the carburetor float chamber at a constant pressure irrespective of atmospheric conditions, which will enable the conventional .float valve to fishutoif. Another and most. important object is the provision of an arrangement for reducing the pressure of fuels having a considerably higher vapor pressure than ordinary gasoline at asufliciently low temperature to deliver said fuels to the carburetor jet without substantialvaporization or the occurrence of vapor lock.

Referringtothe drawings,

Figure 1 illustrates diagrammatically in partial section a preferred form of the present invention.

Figure 2 shows a specially constructed carlouretor embodying'the principle of this invention and provided with means for cooling the float chamber.

Referring to Figure 1 of the drawings, the numeral l designates generally a standard type of liquid carburetor such as manufactured by the Carter Company connected with the manifold 2 of an internal combustion engin through an intake tube extension 3. The mainthrottle valve t is mounted on a shaft 5 .in' a separate connection 6' and actuated by the foot accelerator (not shown) through the lever B and rod 8 in av conventional manner. The throttle in carburetor i has been removed. The connection 6 is insulated from the extension 3 by a flange 0r gasket 9 of cork, asbestos, or similar material to prevent transfer of heat by conduction from said connection'. By positioning the throttl valve connection on the down-stream side of the heat 55 exchange zone where it is subjected to heat radiation from the exhaust manifold, the formation of ice at this point is prevented.

An idling line I connects the carburetor float chamber with the fuel intake tube at the connection 6 and is provided with air and liquid adjustment screws II and I2, respectively. The normal idling jet in carburetor I has been made ineffective. As will be obvious, the idling fuel from line l0 discharges through orifice |0A into the connection 6 at a point just below the edge of the upper half of the butterfly 4 when closed. A rod 3 controls the carburetor accelerating pump and main orifice needle, not shown, from a lever It fixed on the projecting end of the throttle shaft 5. The carburetor is provided with a float chamber |5 having a float l6 actuating a needle valve I! to control the fuel inlet passage |8 according to the liquid level therein. An air inlet l9 and choke lever 20 are likewise provided, above the point at which the fuel is introduced into the fuel intake tube from the conventional carburetor jet 20A.

The liquid fuel inlet tube 2| is connected to a. high pressure fuel storage tank,- not shown, which may contain any higher than normal vapor pressure fuel such as 26 or 48 pound Reid vapor pressure natural gasoline, mixtures thereof or the like. Incidentally, the device of the present invention is so constructed and arranged as to handle low pressure fuels with equal expediency, although it is primarily adapted for fuels having a vapor pressure considerably above ordinary gasoline.

The tube 2| prior to connection with the carburetor inlet I8 is coiled around the fuel intake extension 3, as shown in the drawings. A pressure reducing regulator 22 is connected to the coiled tube, preferably at an intermediate point thereof, adapted to reduce the pressure of the high pressure fuel to a substantially constant value after it has been cooled to a sufficiently low tempera- .diaphragm loader, the core valve is opened wider than during normal regulator operation, venting the vapor through the regulator and carburetor and allowing passage of liquid. The carburetor then is rapidly cooled. In order to facilitate heat transfer from the liquid fuel to the vaporous fuel in the intake tube, solder or other suitable conducting material is supplied between thecoils of the liquid tube and between the liquid tubeand the fuel intake tube. For illustration; the metallic conducting material is shown as extending only partially around the extension exposing the inlet tube.

.A vacuum operated shut-off valve 36 is provided in the liquid fuel inlet line just before the fuel enters the carburetor float chamber. This device includes a connection 31 to the starter pedal and a vacuum line 38 communicating with the intake manifold. Depression of the starter retracts the valve allowing fuel flow into the float chamber and when the motor starts, suction from the intake manifold maintains the valve in open positure. The regulator 22 includes a diaphragm 23 of synthetic rubber or other hydrocarbon resistant material clamped between the cap 24 and base 25. The base is secured to the carburetor intake tube and the lower section of the coiled tube 2| is connected to the chamber 26 to the left of the diaphragm by a short tube 21, which extends directly through the intake tube and hence is subjected to the low temperature vapors passing to the manifold. A valve core 28, which may be of the ordinary tire valve type, is threaded to the interior of the tube 21 and the valve stem 29 is provided with an actuating member 30 bearing on the bottom of diaphragm 23. The upper section of the coiled tube 2| connects the outlet of diaphragm chamber 26 with the carburetor float chamber inlet.

A coil spring 3|, contained within two interfltting and relatively movable cup shaped members 32 and 33, is interposed between the cap 24' and diaphragm 23, the cup shaped members forming a manually controlled diaphragm loader. Member 32 is secured to the diaphragm and movable therewith, while member 33 has an actuating pin 34 which passes through an opening in the top of the cap. An operating lever 35 is connectedto a Bowden cable 35a which extends to the dash-board of the automobile. By means of the foregoing arrangement, engine starving is prevented where the motor is stopped for a short period and heat is picked up from the exhaust manifold which may cause some vaporization to take place at the regulator. Bydepressing the regulator valve several times with the manual tion. Since the vacuum operated valve forms no part of this invention it will not be described in detail. Other valves, for instance electrically operated shut-off valves, may be employed.

In operation, by depressing the starter the shut-off valve 36 is opened wide permitting fuel flow from the cooling coil to the carburetor float chamber. If the engine has been at standstill,

the small volume of fuel remaining in the float chamber has been heated and possibly a small amount of evaporation of the lightest ends of the hydrocarbon fuel will take place. The fuel remaining in the float chamber, however, is supplemented on starting by fresh fuel admitted through the shut-off valve and having been deprived of the lighest ends, does not cause vapor lock in the carburetor jets. The fuel passing from the high pressure tank, where it is stored under its own vapor pressure, for example, in. the case of 26 pound Reid vapor pressure natural'gasoline may have a pressure considerably above or below 26 pounds per square inch, depending upon atmospheric temperature and the temperature of the tank. When the engine is started, flow takes place through the liquid inlet tube and lower sec tion of the cooling coil'into the pressure regulator 22. In the pressure regulator 22 the fuel pressure is reduced to from 1.5 to 2.5 pounds per square inch. The regulator outlet pressure is rather critical inasmuch as pressures much above the upper limit will not allow the carburetor float valve to shut off, while if the pressure falls below the lower limit sufficient fuel is not supplied to the engine upon acceleration.

As the fuel is vaporized in the carburetor let the latent heat of evaporation necessary to vaporize the fuel is abstracted from the incoming air thereby cooling the vaporto a very low temperature. As the vapor passes downwardly through'the intake tube 3, heat t'ransfertakes place from the liquid fuel flowing through the liquid fuel inlet tube coil 2| through the wall ,of the vapor intake tube. The transfer of heat in this manner lowers the temperature of the high pressure fuel sufficiently to enable the reduction of pressure in the pressure regulator without evaporation. The pressure regulator is advantageously located at an intermediate point in the cooling coil to discourage vaporization at the throttling orifice. Ordinarily the temperature is reduced to a suflicient value prior to entry in the regulator to prevent vaporization. In extremely warm climates, however, it may be adof the liquid fuel flowing thereto. Referring to Figure 2, wherein aeoarac vantageous to provide a further cooling section. Should the presure'of the fuel be reduced without previously being cooled, the light ends contained in the fuel which may constitute which as .50

per cent in liquid volume thereof, are flashed off causing vapor lock and disturbing the fuel metering devices. with the arrangement of the present invention, however, pressure reduction to as low a point as from 1.5 to 2.5 pounds per square inch can be accomplished without substantial vaporization either in the cooling 'coil or in the carburetor float chamber. The pressure is preferably maintained constant within this approximate range. After the engine has been started the fuel in the carburetor float chamber is cooled suffloiently so that no vaporization occurs in the carburetor jet. The cooling effect of the cold vapors passing to the inlet manifold is adequate to maintain hydrocarbonfuels havingvapor pres sure as high even as 40 pound Reid vapor pres sure natural gasoline in liquid phase. The carburetion of high pressure, high octane fuels is thus possible by the practice of the present invention with the conventional carbureting arrangement. The labor and expense necessary to make this conversion is very small. The carburetor may still be suitable for handling ordinary gasoline with minor adjustments.

The manual diaphragm loader 3t enables rapid starting of the engine in warm weather when some vaporization may occur in the upper section of the cooling coil after the engine has been at standstill for a short period of time and heat transfer has taken place from the exhaust manifold. Depression of the diaphragm loader through the dashboard control-vents any vapor which may have formed through the regulator and carburetor which is followed by liquid fuel, rapidly cooling the coil and carburetor float chamber. To avoid icing in and around the main throttle valve which tends to occur with the higher pressure fuels, such as at) pound natural gasoline, the short tubing section 6 which carries the throttle valve is placed between the intake tube extension and the intake manifold where The diaphragm chamber ti communicates with the float chamber of the carburetor through a passage 52, provided with a-valve t3 likewise of the tire core type. The float chamber at is provided with a float 5d which closely fits the interior ofthe chamber and actuates the valve 53 through a push pin 85. The float chamber communicates with the interior of the fuel intake tube through a balance line 55. By these means the pressure on the fuel in thefioat chamber is maintained the same as thepressure within the intake tube. The force transmitted on the push pin 56 by the float is regulated by means of a coil spring fil contained within a central assage 58 of a cover as. The compression of. the spring is regulated by means of an adjustment screw 50. The liquid fuel from the float chamber passes to the fuel intake tube through a discharge orifice or jett ti. A needle valve 82 provided with a lock nut 53 meters the flow of liquid fuel to the discharge jet from the float chamber. The fuel intake tube is provided with the conventional venturi t t and main throttle valve 65, as shown in the drawings.

A shut-off valve, shown diagrammatically at 66, may be connected with a vacuum control device as shown in Figure l or a suitable electric circult. This device is adapted to remain closed during standstill but is opened wide allowing fuel flow to the float chamber when the motor is started. 1

The operation of the Figure 2 carburetor is quite similar to that of ,the arrangement prevh ously described in connection with Figure 1. Due to the fact that the liquid inlet tube is coiled around the float chamber as well as the fuel intake tube to the manifold; heat is transferred from the interior of the carburetor float chamber .to the liquid fuel passing through the coil which in turn loses heat to the cold vap'ors following vaporization at the carburetor jet. With the ar rangementof the Figure 2 carburetor the regulator outlet pressure is preferably set around 2 pounds per square inch. This pressure, however,

it is subjected to heat radiation from the exhaust v manifold 2A. Various other supplemental heating means may be employed for the throttle such as electrical means or a short section of pipe connected with the exhaust manifold and wrapped around the intake tube in the vicinity of the throttle valve.

A modified form of carburetor is shown in Fig ure 2 wherein the fuel line from the high pressure fuel storage tank embraces the carburetor float chamber as well as the vapor intake tube to the manifold. This arrangement allows the transfer of the cooling effect in the vapor intake tube to the float chamber through the medium for the sake of brevity reference numerals'to similar elements in Figure 1 are omitted, the fuel inlet line. 39 from the high pressurefuel storage tank is connected with a coil tube 40 which surrounds the fuel intake tube M and carburetor float chamber 62. The cooling coil 40 is connected with a passage 63 which communicates with the pressure regulator, shown generally at 44, through a the core valve 55. The pressure regulator includes a cap at and diaphragm clamped between the cap and the body of. the'carburetor. A valve operating element or push pin" is held between the valvestem 49 and. the diaphragm 41' by a loading spring and the valve spring, not shown.

the core valve is balanced by the adjustable spring 51 which acts as a loading'means for the float.

It is thus obvious that by the arrangement of the present invention-fuels having a considerably higher pressure than ordinary gasoline may be employed with expediency, thereby utilizing hydrocarbon fractions hitherto considered im-= practical as a fuel for internal combustion engines. The degree of cooling necessary to maintain the fuel in liquid phase following pressure reduction varies as to. the particular fuel being employed. In the case of 26 pound natural gasoline a temperature reduction to approximately 60 F. is suflicient, while a somewhat lower temperature, 1. 'e., about 416 F. is necessary in the case of 401 pound natural gasoline. The cooling coil, of course, is of suillcient length to secure the desired results and may be provided with a valved bypass prior to the point of pressure reduction to regulate'the degree of cooling for the specific fuel employed. This and other changes andmodifications may be made in the arrangement shown in the accompanying figures without departing from the spirit and scope of the present invention.

therein, an engine mixture inlet tube for leading the vapors from said carburetor to the intake manifold of the engine, a liquid fuel inlet for incoming high pressure fuel, conduit means surrounding the engine mixture inlet tube for conveying said incoming fuel from said inlet to said carburetor, the liquid fuel being cooled as it is conveyed to said carburetor by the heat exchange relationship between the conduit means surrounding the engine mixture inlet tube and the vaporized fuel in the engine mixture inlet tube to thereby prevent vaporization of said liquid fuel at least until it reaches the main jet in the carconduit means at an intermediate point therein 7 comprising a reducing valve, said valve being loaded by a spring pressed diaphragm and provided with manually operated means for opening said valve wider than normal in starting the englue and said reducing valve being coo ed by heat exchange relation with the engine mixture inlet tube for reducing without vaporizing the pressure buretor, pressure reducing means located in the conduit means at an intermediate point therein and said'pressure reducing means being cooled by heat exchange relation with the engine mixture inlet tube for reducing without vaporization the pressure of said liquid fuel before it reaches said float-operated valve to a constant low value for thereby preventing interference with free operation of said valve.

1 2. A device used for carbureting a high pressure liquid fuel and feeding the same to an internal combustion engine comprising, in combination, a carburetor having a main liquid fuel jet, a float chamber and a float-operated valve of said liquid fuel before it reaches said floatoperated valve to a constant low value, for

thereby preventing interference with free operation of said valve.

3. A device used for carbureting a high pressure liquid fuel and feeding the same to an internal combustion engine comprising, in combination, a carburetor having a main liquid fuel jet, a float chamber and a float-operated valve therein, an engine mixture inlet tube for leading the vapors from said carburetor to the intake manifold of the engine, a liquid fuel inlet for incoming high pressure fuel comprising a tube coiled about said engine mixture inlet tube from the engine side to the carburetor side thereof,

I the liquid fuel being cooled as it is conveyed to therein, an engine mixture inlet tube for leading the vapors from said carburetor to theintake manifold of the engine, a liquid fuel inlet for incoming high pressure fuel, conduit means surrounding the engine mixture inlet tube for conveying said incoming fuel from said inlet to said carburetor, the liquidfuel being cooled as it is conveyed to said carburetor by the heat exchange relationship between the conduit means surrounding the engine mixture inlet tube and the vaporized fuel in the engine mixture inlet tube to thereby prevent vaporization of said liquid fuel at least until it reaches the main jet in the car buretor, pressure reducing means located in the said carburetor by the heat exchange relationship between the conduit means surrounding the engine mixture inlet tube and the vaporized fuel in the engine mixture inlet tube to thereby prevent vaporization of said liquid fuel at least until it reaches the main jet in the carburetor, pressure reducing means located in the conduit means at an intermediate point therein and said pressure a reducing means being cooled by heat exchange relation with the engine mixture inlet tube for reducing without vaporization the pressure of said liquid fuel before it reaches said float-operated valve to, a constant low value for thereby preventing interference with free operation of said valve.

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