Internal-combustion engines – Charge forming device – Cooling of combustible mixture
Reexamination Certificate
2000-04-06
2001-06-26
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Charge forming device
Cooling of combustible mixture
Reexamination Certificate
active
06250290
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fuel rail for a fuel injection system on a vehicle and especially a fuel rail for delivering LPG fuel.
BACKGROUND OF THE INVENTION
As concerns for the environment increase and the need for better fuel economy is required, the use of alternate fuels in a vehicle is becoming more desirable. Liquified petroleum gas, or LPG may be used in more or less standard gasoline-type engines equipped with special fuel systems. LPG is made up of certain light hydrocarbon molecules. Therefore, LPG is a fuel that is liquid only under pressure. When the pressure on LPG is reduced, it vaporizes. Typical LPG fuels used for automotive engines include propane and butane. Because butane boils and turns to vapor at approximately 32° F. (0° C.) at atmospheric pressure, butane generally cannot be used in regions where temperatures fall below 32° F. because the butane does not vaporize adequately. On the other hand, propane boils at −44° F. (−42.2° C.) at atmospheric pressure and therefore will vaporize at air temperatures in which the vehicle operates. Although LPG fuel includes some disadvantages such as greater cost of transporting and storing LPG because of special handling requiring pressurized tanks, its advantages are beginning to outweigh the disadvantages and especially for use in fleet operations.
It is known from tests using LPG fuel made on a number of transit companies on their fleet vehicles that LPG fuel offers many advantages. Some advantages using LPG fuel over conventional gasoline fuel include that LPG has a high octane number which allows for compression ratios in the engine over 10:1 which results in increased engine power output. Further, because LPG quickly vaporizes, little or no engine deposit is left in the cylinders. In addition, the LPG fuel cannot wash down the cylinder walls and remove lubricant therefrom. Therefore, cylinder wall, piston and piston ring wear is decreased which reduces engine wear, increases engine life, and keeps maintenance costs low.
Although LPG fuel may require a special pressurized fuel tank in the automobile to maintain the fuel in liquid form, many of the components traditionally used in a gasoline fuel injection system may be continued to be used when using LPG fuel. In the fuel delivery system of internal combustion engines, it is customary to connect electronically controlled fuel injectors to a fuel rail. The injectors deliver fuel to the engine in metered pulses which are timed to control the amount of fuel delivered and to coordinate the delivery with the operation of the engine. Because it is more difficult to meter the LPG fuel into the injectors when the fuel is in gaseous state, it is desirable to maintain the LPG fuel in the liquid state in the fuel rail. After a hot soak condition or during certain driving conditions it is difficult to keep the LPG fuel in the fuel rail in a liquid form. It is the intent of the present invention to address this concern.
SUMMARY OF THE INVENTION
The invention provides an improved fuel rail assembly for delivering liquid LPG fuel under high pressure from a fuel tank to its internal combustion engine whereas the fuel rail assembly includes a first end for receiving fuel and a second end for purging fuel to the fuel tank. At least one fuel delivery socket extends from the fuel rail assembly and has a port opened between the fuel delivery socket and the fuel rail assembly. The delivery socket is configured for receiving a fuel injector. An improvement to the fuel rail assembly includes a means for cooling at least a portion of the fuel rail assembly with the fuel at selective intervals.
In one embodiment of the invention, a primary conduit of the fuel rail is opened to an expansion chamber. At least one small aperture communicates fluid from the primary conduit to the expansion chamber. The expansion chamber communicates with a vapor fuel return conduit ultimately plumbed to the fuel tank. The flow path between the expansion chamber and the vapor fuel return conduit may be selectively opened or closed. When the expansion chamber is opened to the vapor fuel return conduit, liquid fuel as well as vapor fuel in the primary conduit enters the expansion chamber through the small aperture. As the liquid LPG enters the expansion chamber, the liquid expands rapidly as it transforms to gas. The heat of vaporization produced by the transformation between the liquid state and vapor state of the LPG fuel causes a cooling of the vapor which absorbs heat or energy from the surrounding material. Therefore, any portion of the primary conduit in contact with the cooled vapor will have its heat absorbed so that the fuel rail is cooled to maintain the LPG inside the primary conduit as a liquid.
In a corresponding aspect of the invention, the expansion chamber is configured as a secondary fuel rail at least partially encapsulating a primary fuel rail. A plurality of small apertures extends through the wall of the primary fuel rail into the secondary fuel rail. The secondary fuel rail further has a port to a vapor fuel return conduit to the fuel tank. The port from the secondary fuel rail to the vapor fuel return conduit is selectively opened by attaining predetermined parameters. These parameters may include temperature or pressure. When the port to the vapor fuel return conduit is opened, liquid LPG in the primary fuel rail expands to vapor as it enters the secondary fuel rail through the apertures. The transformation of the liquid LPG to vapor cools the vapor. Further, as the cooled LPG vapor travels in the secondary fuel rail, adjacent to the primary fuel rail, and to the port leading to the vapor fuel return conduit, the cooled vapor absorbs heat from the adjacent primary fuel rail. As a result, the primary fuel rail is cooled to help maintain the LPG fuel located in the primary fuel rail in a liquid state. Once the primary fuel rail has been cooled to a predetermined temperature, the port from the secondary conduit to the vapor fuel return conduit is closed.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.
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Kamen Noah P.
Transportation Design & Manufacturing Co.
Young & Basile P.C.
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