AND RETROFIT KIT INCORPORATING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 13/829,193, filed March 14, 2013, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Diesel engines have long been direct injected engines wherein fuel is injected at or near top dead center (TDC) directly into the combustion chamber. Many gasoline engines are now being developed as direct injected engines in order to take advantage of the efficiencies associated with direct injection. Direct injected gasoline engines are now possible due to advances in injector technology as well as advances in engine control strategy. However, direct injecting gaseous fuels such as natural gas or hydrogen have not yet gained similar feasibility.

[0003] One of the practical difficulties with using a gaseous fuel in a direct injected system is providing the fuel at a high enough pressure to be injected near top dead center while providing a volume of fuel, which may be 3000 times the volume of operation on diesel fuel. Typical compressed natural gas (CNG) tanks are designed to contain fuel at approximately 3600 psi. In order to direct inject a gaseous fuel at or near top dead center, fuel may be at approximately 5800 psi. This high pressure helps to overcome the cylinder pressure under compression as well as to provide enough fuel into the cylinder.

Gaseous fuel has a lower energy density by volume when compared to diesel and gasoline, thus a much higher volume of fuel may be introduced into the cylinder in order to produce the same power. Existing infrastructure, tank technology, and fuel systems are designed around the standard 3600 psi system. Accordingly, there is a need for a gaseous fuel system capable of operating as a direct injected fuel system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Non-limiting and non-exhaustive embodiments of the devices, systems, and methods, including the preferred embodiment, are described with reference to the following figure, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0005] FIG. 1 is a schematic representation of a high pressure direct injected gaseous fuel system.

DETAILED DESCRIPTION

[0006] The representative embodiments disclosed herein include a high pressure direct injection gaseous fuel system and retrofit kit incorporating the same. In one embodiment, the system comprises a fuel tank capable of storing fuel at a first pressure and a compressor including an inlet capable of receiving the fuel, and operative to supply, at an outlet, compressed fuel at a second pressure higher than the first. The system also includes an accumulator connected to the outlet and one or more injectors connected to the accumulator. The injectors are adapted to inject fuel directly into a combustion chamber. In some embodiments, the injectors are injector- igniters. The system may further include a pressure relief valve interconnecting the fuel tank and the outlet, wherein the pressure relief valve is operative to allow fuel flow between the fuel tank and outlet if the second pressure exceeds a threshold pressure.

[0007] In certain aspects of the disclosed technology, the compressor further comprises a blow-by vent and in some embodiments, the system is installed on an engine and the blow-by vent is connected to an intake of the engine. In other aspects of the technology, the compressor is powered by an engine driven hydraulic pump. In some embodiments, the compressor is an engine driven variable displacement compressor.

[0008] In another representative embodiment, a high-pressure direct injection gaseous fuel system includes a fuel tank capable of storing fuel at a first pressure and a compressor including an inlet capable of receiving the fuel, and operative to supply, at an outlet, compressed fuel at a second pressure higher than the first. The system further includes an accumulator connected to the outlet and one or more injector- igniters connected to the accumulator, wherein the injector-igniters are adapted to inject fuel directly into a combustion chamber.

[0009] In certain embodiments a heat exchanger is provided between the accumulator and one or more fuel injectors for heating or cooling the fuel to provide thermal conditioning of the fuel for direct injection by the injectors. Such thermal conditioning may increase or decrease the ability of the fuel to suspend a condensable phase such as propane or butane from natural gas fuel or another substance such as water without precipitation. In some instances cooling the fuel is provided to enable collection of a condensable substance such as water by a suitable filter or desiccant and thus prevent condensation of liquid water in any of the injectors. In another embodiment thermal conditioning is provided to increase or decrease the requirement for additional activation energy to initiate or accelerate combustion of injected fuel.

[0010] In addition, a pressure relief valve interconnects the fuel tank and the outlet, and is operative to allow fuel flow between the fuel tank and outlet if the second pressure exceeds a threshold pressure. In some embodiments, the compressor is a variable displacement compressor.

[0011] Also provided herein is a high pressure direct injection gaseous fuel system retrofit kit. In a representative embodiment, the kit comprises a compressor including an inlet capable of receiving fuel at a first pressure, and operative to supply, at an outlet, compressed fuel at a second pressure higher than the first. The kit can also include an electric motor or engine drivable hydraulic pump, operative to provide power to the compressor, an accumulator connectable to the outlet. The kit can also include one or more heat exchanger(s) for operation between the compressor and the accumulator and/or for operation between the accumulator and the injector(s) and one or more suitable filters and one or a plurality of injectors connectable to the accumulator, wherein the injectors are adapted to inject fuel directly into a combustion chamber. In other embodiments, the retrofit kit includes a pressure relief valve interconnectable to a fuel tank and the outlet, and operative to allow fuel flow between the fuel tank and outlet if the second pressure exceeds a threshold pressure.

[0012] In one aspect of the technology, the kit includes a fuel tank capable of storing fuel at a first pressure and connectable to the compressor. In other aspects, the hydraulic pump is engine mountable, and in still further aspects of the technology, the hydraulic pump is adapted to mount in place of or in conjunction with an engine- mounted fuel pump.

[0013] Specific details of several embodiments of the technology are described below with reference to FIG. 1 . Other details describing well-known structures and systems often associated with ignition systems, fuel systems, and electronic valve actuation, such as fuel pumps, regulators, heat exchangers, filters, valves, and the like, have not been further set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments of the technology. Many of the details, dimensions, angles, steps, and other features shown in the figures are merely illustrative of particular embodiments of the technology. Accordingly, other embodiments can have other details, dimensions, angles, steps, and features without departing from the spirit or scope of the present technology. A person of ordinary skill in the art, therefore, will accordingly understand that the technology may have other embodiments with additional elements, or the technology may have other embodiments without several of the features shown and described below with reference to FIG. 1 .

[0014] Some aspects of the technology described below may take the form of or make use of computer-executable instructions, including routines executed by a programmable computer or controller. Those skilled in the relevant art will appreciate that aspects of the technology can be practiced on computer systems other than those described herein. Aspects of the technology can be embodied in one or more special- purpose computers or data processors, such as an engine control unit (ECU), engine control module (ECM), fuel system controller, ignition controller, or the like, that is specifically programmed, configured, or constructed to perform one or more computer- executable instructions consistent with the technology described below. Accordingly, the term "computer," "processor," or "controller" as may be used herein refers to any data processor and can include ECUs, ECMs, and modules, as well as Internet appliances and hand-held devices (including diagnostic devices, palm-top computers, wearable computers, cellular or mobile phones, multi-processor systems, processor- based or programmable consumer electronics, network computers, mini computers and the like). Information handled by these computers can be presented at any suitable display medium, including a CRT display, LCD, or dedicated display device or mechanism (e.g., a gauge).

[0015] The technology can also be practiced in distributed environments, where tasks or modules are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules or subroutines may be located in local and remote memory storage devices. Aspects of the technology described below may be stored or distributed on computer- readable media, including magnetic or optically readable or removable computer disks, as well as distributed electronically over networks. Such networks may include, for example and without limitation, Controller Area Networks (CAN), Local Interconnect Networks (LIN), and the like. In particular embodiments, data structures and transmissions of data particular to aspects of the technology are also encompassed within the scope of the technology.

[0016] FIG. 1 illustrates a high pressure direct injection gaseous fuel system 100 according to a representative embodiment. In this embodiment, the fuel system 100 includes a pair of fuel storage tanks 102 and 104, which in this case are configured to contain LPG and/or a gaseous fuel such as CNG, carbon monoxide, or hydrogen, for example. Each tank 102 and 104 is coupled to the safety devices such as pressure relief devices 106, as well as the control valves such as control valve 108. In this embodiment, fuel tanks 102 and 104 are adapted to store gaseous fuel at approximately 3600 psi, which is typical of compressed natural gas. Tanks 102 and 104 are filled via one or more fill nozzles 1 10 as shown. Tanks 102 and 104 may include filters and/or suitable engine coolant and/or electric heaters to assure adequately rapid delivery of gaseous fuel.

[0017] Fuel flows from tanks 102 and 104 at a first pressure to compressor 1 12 which is operative to compress the fuel. Compressor 1 12 includes inlets 1 13 capable of receiving fuel from the fuel tanks 102 and 104 and is operative to supply at outlets 1 15 compressed fuel at a second pressure higher than the first pressure. For example, compressor 1 12 receives fuel from tanks 102 and 104 at approximately 3600 psi and provides compressed fuel at approximately 5800 psi. Compressor 1 12 provides the high pressure fuel to accumulator 1 14 which is connected to outlets 1 15. One or more heat exchanger and filter assembly units 1 17 may be installed before and/or after accumulator 1 14 to provide thermal conditioning for prevention of liquid substance condensation accumulations in any of the injector(s) and/or to adjust the requirement for further addition of activation energy for initiation of combustion upon direct injection into combustion chambers of the engine. Thermal conditioning by heat exchanger/filter units 1 17 may utilize heat (H-1 ) supplied by warm engine coolant, H-2 supplied by exhaust gases, and/or H-3 from regenerative braking or suspension system generators. Conversely, thermal conditioning to cool compressed fuel may utilize ambient air, return flow of radiator coolant, or fuel from a supply such as a pipeline or tank for removing heat from hot compressed fuel before or after passage to accumulator 1 14.

[0018] Illustratively in some homogeneous charge applications that require ignition considerably before top dead center (TDC) thermal conditioning may be applied to cool the fuel for prevention of undesirable detonation. In some instances this involves cooling the fuel to condense water from a fuel such as humid natural gas and the liquid water is then portioned back into the injected natural gas to produce evaporative cooling sufficient to prevent unwanted detonation in a warm engine operating with elevated temperature inlet air (e.g., at or near full torque production on a hot day). However in preparation for lower power operation or storage of the engine, thermal conditioning may be provided to filter and remove water to prevent accumulations that produce electrically conductive electrolytes and/or cause corrosive damage to the injector components. In stratified charge applications thermal conditioning may be applied to reduce the amount of electric spark or corona energy needed for initiating of combustion (e.g. at startup on a cold day and/or to gainfully utilize H-1 , H-2 and/or H-3 energy.) Accumulator 1 14 in turn supplies a plurality of injectors 1 16.

[0019] Injectors 1 16 are adapted to inject a gaseous fuel directly into a combustion chamber. Injectors 1 16 may be in the form of injector-igniters such as those described in co-pending U.S. Patent Application No. 12/653,085, filed December 7, 2009, the disclosure of which is incorporated herein by reference in its entirety. Injector-igniters may be used in a retrofit kit in order to provide spark as well as fuel in the confined spaces of an existing cylinder head. A pressure regulator 1 18 is connected between accumulator 1 14 and the plurality of injectors 1 16, and functions to supply fuel at a constant pressure to the injectors 1 16. Fuel system 100 also includes a pressure relief valve 120 interconnected between the fuel tanks 102, 104 and the outlets 1 15 of compressor 1 12. The pressure relief valve 120 is operative to allow fuel flow between outlets 1 15 and fuel tanks 102 and 104, if the second pressure exceeds a threshold pressure. Accordingly, pressure relief valve 120 is operative to prevent over-pressurization of the accumulator 1 14 and the downstream fuel injection system. In the event that pressure exceeds the threshold pressure, the high pressure coming from the outlets 1 15 is vented back to the lower pressure tanks 102 and 104.

[0020] In some embodiments, the compressor 1 12 is a hydraulically-driven double-acting intensifier. Other suitable compressors as are known in the art may also be used. For example, in some embodiments, compressor 1 12 can be a variable displacement compressor. In still other embodiments, compressor 1 12 can be directly driven by an engine. In an embodiment, compressor 1 12 includes a blow-by vent 123 to accommodate blow-by and leakage often associated with piston compression pumps. Any fuel vented through blow-by vent 123 flows through a blow-by flow meter 122 and is vented into the air intake 124 of an associated engine. Thus, rather than venting fuel to the atmosphere, the fuel is fed into the engine where it is burned in due course. Accordingly, because fuel is entering the intake system, the fuel injection system must account for the additional fuel in the air. To that end, the blow-by flow meter 122 communicates with an engine control module 200, which in turn adjusts the amount of fuel injected by fuel injectors 1 16 to the engine.

[0021] In this embodiment, compressor 1 12 is powered by an engine-driven hydraulic pump 126. The hydraulic pump 126 is part of an associated hydraulic system 128 which includes a tank 130 and the control valves such as control valve 132. The fuel system 100 may also include a cooling system 134 in order to cool the compressed fuel at the outlets 1 15 from compressor 1 12. Cooling system 134 may also cool the hydraulic fluid used to power the compressor 1 12. It may also be used to heat a pressure regulator 1 18 in order to prevent freezing due to expansion of fuel therethrough.

[0022] The fuel system 100 as described above may also be the basis for a retrofit kit to convert diesel engines to run on alternative fuels such as compressed natural gas. Accordingly, various combinations of the above described components may be packaged and provided as a kit in order to convert such vehicles. For example, in one embodiment, a high-pressure direct injected gaseous fuel system retrofit kit includes a compressor 1 12, an engine-drivable hydraulic pump 126, an accumulator 1 14, and a plurality of injectors 1 16. In other embodiments, the kit may also include a pressure relief valve 120 that is interconnectable between the fuel tank and outlet. In still further embodiments, the kit may include one or more fuel tanks capable of storing fuel. In some embodiments hydraulic pump 126 is engine mountable and is adapted to mount in place of an engine mounted fuel pump. In other embodiments, the kit may also include pressure regulator 1 18. In still further embodiments, the kit may include fittings, valves, tubing, wiring and control modules such as shown in FIG. 1 .

[0023] From the foregoing, it will be appreciated that, although specific embodiments of the technology have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the technology. Further, certain aspects of the new technology described in the context of particular embodiments may be combined or eliminated in other embodiments. Moreover, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Also contemplated herein are methods which may include any procedural step inherent in the structures and systems described. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein. The following examples provide additional embodiments of the present technology.