Internal-combustion engines – Charge forming device – Combined liquid and gaseous fuel
Reexamination Certificate
2001-03-21
2003-07-15
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Charge forming device
Combined liquid and gaseous fuel
C526S276000
Reexamination Certificate
active
06591817
ABSTRACT:
BACKGROUND OF THE INVENTION
This application pertains to a dual fuel method and system for use with internal combustion engines of vehicles.
As gasoline supplies have decreased and become more costly, the need for alternative fuels and fuel conservation has become greater. Accordingly, alternate sources of fuels and methods of fuel conservation have become more attractive, particularly for internal combustion engines for automotives.
Operation of an internal combustion engine on a liquid fuel and a gaseous fuel increases fuel economy and engine efficiency while at the same time maintaining low levels of undesirable exhaust emissions. Vehicles adapted to operate on either a liquid fuel or a gaseous fuel are sometimes called “dual fuel” or “multi-fuel” vehicles.
In order to maximize fuel economy and minimize engine emissions, there has been a trend to use gaseous fuels, such as compressed natural gas (CNG), liquid natural fuels (LNG), such as ethanol, and liquid or liquified petroleum gas (LPG). Gaseous fuels, such as CNG, and LPG, not only provide good fuel economy and low engine emissions, but also provide better cold starting of internal combustion engines.
Gaseous fuels comprise combustible fuels which are gaseous at standard temperature and pressure. Gaseous fuels used by dual fuel vehicles include methane comprising natural gas or compressed natural gas (CNG), hydrogen, etc. The term gaseous fuels also includes liquified petroleum gas (LPG). LPG is particularly desirable as gaseous fuel. LPG under pressure may be either in the gaseous phase, the liquid phase, or both. Examples of LPG are propane, butane, dimethyl ether (DME), etc.
Atmospheric pollution from combustion of hydrocarbon fuels, such as emitted from the exhaust of gasoline fueled automotive internal combustion engines, if not properly controlled, can cause problems. Substantial effort and research has gone into the development of vehicle engines which operate on various lighter hydrocarbon fuels as an alternative to gasoline, such as ethanol, and even those fuels having less complex hydrocarbon molecules with fewer carbon atoms per molecule, i.e., pentane, butane, propane, methane, and even ethane. Natural gas (methane) has been used because of its abundance and clean burning performance, its relatively low costs and its use as a fuel for stationary internal combustion engines. In order to provide an adequate supply in vehicles for fueling vehicle internal combustion engines, the fuel must be stored in highly compressed form, requiring heavy duty, highly pressurized fuel tanks and fuel system components capable of storing gaseous methane at ambient temperatures ranging up to 125° F. (51.6° C.) and be capable of withstanding high pressures.
Propane on the other hand, can be stored in liquid form and at much lower pressures than methane, e.g. 0 psi at −44° F. (−42.2° C.), 125 psi at about 70° F. (21.1° C.) and 260 psi at 125° F. (51.6° C.). In some geographic locations, supplies of liquid propane fuel for a variety of uses are already relatively abundant and economical.
Various dual fuel systems have been developed utilizing propane as the alternative fuel of choice with pressurized containment and delivery of propane. Typical vehicle propane fuel tank systems commercially available supply propane in gaseous form to the engine intake manifold via a carburetor fuel feed system or an electronic fuel injection (EFI) system.
Many conventional dual fuel systems are expensive and unreliable. Furthermore, conventional dual fuel systems often have two separate systems with many duplicate, redundant and/or extra sets of parts, components, or equipment, such as computers, hoses, burner assemblies, second stage regenerators, etc. Further, conventional dual fuel systems are often bulky and occupy valuable space in the hood (bonnet) of the vehicle. The extra weight of duplicate equipment of conventional dual fuel systems can increase fuel consumption.
Moreover, conventional dual fuel systems often encounter vehicle performance problems at switchover to different fuels. Switchover to different fuels can be unstable due to timing delays of two fuels. For example, when a conventional carbureted dual fuel system is switched from a gasoline mode to a liquified petroleum gas (LPG) mode, gasoline continues to be fed into the engine at the same time as LPG until the gasoline in the float bowl of the carburetor is empty. This can cause flooding and stalling of the internal combustion engine. When a conventional carbureted dual fuel system is switched from an LPG mode to a gasoline mode, the LPG is shut off, but no gasoline will be fed into the engine until the gasoline fills the float bowl of the carburetor. This can cause choking or sputtering of the internal combustion engine.
Conventional dual fuel system with electronic fuel injectors (EFI) encounter similar problems. For example, when a conventional EFI dual fuel system is switched from a gasoline mode to an LPG mode, gasoline continues to be fed to the engine at the same time as LPG until the residual gasoline in the fuel rail and hoses are depleted. This can cause an undesirable mixture of gasoline and LPG which can cause malfunction and/or engine performance problems. Moreover, when a conventional EFI dual fuel system is switched from a LPG mode to a gasoline mode, residual LPG in the fuel rail and hose will continue to flow into the engine with gasoline which can create unstable, rough and uneven vehicle performance.
It is, therefore, desirable to provide an improved dual fuel method and system, which overcomes most, if not all, of the preceding problems.
SUMMARY OF THE INVENTION
An improved dual fuel method and system is disclosed which provides a smooth transition from a first fuel to a second fuel. The first fuel can be a liquid fuel, such as gasoline or petro, and the second fuel can be a gaseous fuel, such as liquified petroleum (LPG). The dual fuel system can also be constructed to eliminate costly control elements and duplicate sets of equipment for the LPG system, such as computers, hoses, burners assemblies, second stage regenerators, etc. Advantageously, the improved dual fuel method and system is economical, easy-to-use, and convenient. Desirably, the user-friendly dual fuel method and system is reliable, safe, efficient, and effective. Significantly, the inventive dual fuel method and system provides for better fuel economy, occupies less space, and uses less fuel than conventional bulky dual fuel methods and systems.
The preferred liquid fuel is gasoline, although other types of liquid fuels can be used in some circumstances, if desired. The preferred LPG is propane, although other types of LPG can be used if desired, such as butane, dimethyl ether (DME), etc. The preferred gaseous fuel is LPG, although other types of gaseous fuels can be used in some circumstances, such as compressed natural gas (CNG), etc.
The improved dual fuel method and system is especially useful in a vehicle, such as: an automobile, a taxicab, a sport utility vehicle (SUV), a van, a station wagon, a truck, a motorcycle, a snow mobile, a jet ski, an all terrain vehicle, a ship, an airplane, a tractor, a backhoe, a bulldozer, a crane, or road grading equipment. The improved dual fuel method and system can also be used in other mobile engines as well as stationary engines, such as in power plants, generating systems, etc.
The special method for operating a dual fuel system in accordance with principles of the present invention, comprises the steps of: pumping a first fuel, such as gasoline, to a fuel feeding device; feeding the first fuel (e.g., gasoline) from the fuel feeding device to an engine; and operating the engine with the first fuel in a first fuel mode. When it is desired to change the mode of operation of the engine to operate on a second fuel, such as liquid petroleum gas (LPG), the flow of the first fuel (e.g., gasoline) to the fuel feeding device is stopped. In order to prevent flooding, stalling and malfunction of the internal combustion engine, it is best to wait u
Kamen Noah P.
Labudda Kenneth D.
Miller Thomas V.
Motorola Inc.
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