Fuel system for a combustion engine

A fuel system includes an air and fuel mixer configured to mix air and fuel provided to a combustion engine and a fuel path coupled to the air and fuel mixer. The fuel path includes an electronically controlled fuel control valve configured to regulate an air to fuel ratio of an air/fuel mixture provided to the engine, a gas pressure regulator disposed upstream of the fuel control valve and configured to control a pressure of the fuel in relation to an air pressure of the air and fuel mixer, and a manual adjust valve disposed downstream of the gas pressure regulator and configured to mechanically tune a performance of the fuel path to minimize an adjustment by the electronically controlled fuel control valve to regulate the air to fuel ratio. The fuel system is configured to operate with different fuels that differ in physical and chemical properties.

BACKGROUND

The subject matter disclosed herein relates to combustion engines, and more specifically, to fuel systems for combustion engines.

Combustion engines typically combust a carbonaceous fuel, such as natural gas, gasoline, diesel, and the like, and use the corresponding expansion of high temperature and pressure gases to apply a force to certain components of the engine, e.g., piston disposed in a cylinder, to move the components over a distance. Accordingly, the carbonaceous fuel is transformed into mechanical motion, useful in driving a load. Sometimes combustion engines may be moved between and utilized in different sites. The different sites may include gases (e.g., field gases) having different properties (e.g., hydrocarbon composition, specific gravity, heating value, etc.). To accommodate the different gases, the combustion engines may require hardware changes upon moving to a different site that may result in having to certify the combustion engine for the gas (e.g., fuel) produced at the site.

BRIEF DESCRIPTION

In accordance with a first embodiment, a fuel system for a combustion engine is provided. The fuel system includes an air and fuel mixer configured to mix air and fuel provided to the combustion engine and a fuel path coupled to the air and fuel mixer. The fuel path includes an electronically controlled fuel control valve configured to regulate an air to fuel ratio of an air/fuel mixture provided to the combustion engine in response to control signals from a controller, a gas pressure regulator disposed upstream of the electronically controlled fuel control valve and configured to control a pressure of the fuel in relation to an air pressure of the air and fuel mixer, and a manual adjust valve disposed downstream of the gas pressure regulator and configured to mechanically tune a performance of the fuel path to minimize an adjustment by the electronically controlled fuel control valve to regulate the air to fuel ratio. The fuel system is configured to operate with different fuels that differ in physical and chemical properties.

In accordance with a second embodiment, a fuel system for a combustion engine is provided. The fuel system includes a carburetor configured to mix air and fuel provided to the combustion engine, wherein the carburetor includes a carburetor cone having a profile. The fuel system also includes a fuel path coupled to the carburetor. The fuel path includes an electronically controlled fuel control valve configured to regulate an air to fuel ratio of an air/fuel mixture provided to the combustion engine in response to control signals from a controller, a gas pressure regulator disposed upstream of the electronically controlled fuel control valve and configured to control a pressure of the fuel in relation to an air pressure of the carburetor, and a manual adjust valve disposed downstream of the gas pressure regulator and configured to mechanically tune a performance of the fuel path to minimize an adjustment by the electronically controlled fuel control valve to regulate the air to fuel ratio. The profile of the carburetor cone and regulation of the electronically controlled fuel control valve, the gas pressure regulator, and the manual adjust valve enable the fuel system to operate with different fuels that differ in physical and chemical properties.

In accordance with a third embodiment, a method is provided. The method includes beginning operation of a combustion engine utilizing an electronically controlled fuel control valve to regulate an air to fuel ratio of an air/fuel mixture provided to the combustion engine in response to control signals from a controller, wherein the electronically controlled fuel valve is disposed along a fuel path coupled to an air and fuel mixer of a combustion engine. The method also includes adjusting, subsequent to beginning operation of the combustion engine and prior to the combustion engine reaching full speed, a pressure of a fuel within the fuel path based on the physical and chemical properties of the fuel via adjustment of a gas pressure regulator disposed along the fuel path upstream of the electronically controlled fuel control valve. The method further includes, subsequent to adjusting the pressure of the fuel while the combustion engine approaches full speed, mechanically tuning a performance of the fuel path to minimize an adjustment by the electronically controlled valve to regulate the air to fuel ratio by adjusting a position of a manual adjust valve disposed along the fuel path disposed downstream of the gas pressure regulator.

DETAILED DESCRIPTION

The present disclosure is directed to systems and methods for providing a fuel system for a combustion engine (e.g., a spark-ignited gaseous fuel internal combustion engine) that can be utilized with a wide range of different fuels having different physical and chemical properties (e.g., chemical heat content, specific gravity, hydrocarbon composition, etc.) with a combustion engine (e.g., a spark-ignited gaseous fuel internal combustion engine). The fuel system includes an air and fuel mixer (e.g., carburetor) that mixes air and fuel provided to the combustion engine. The fuel system also includes a fuel path for a fuel (e.g., gaseous fuel such as natural gas from a natural gas field) coupled to the air and fuel mixer. In certain embodiments, the fuel path includes an electronically controlled fuel control valve (e.g., fuel control valve) that regulates (e.g., maintains) the air to fuel ratio (or lambda (λ) or equivalence ratio, i.e., ratio of actual AFR to stoichiometric AFR) of an air/fuel mixture provided to the combustion engine in response to control signals from a controller. The AFR is the mass ratio of air to fuel. The fuel path may include a gas pressure regulator (e.g., located upstream of the electronically controlled fuel control valve) to control a pressure of the fuel in the fuel path. The fuel system may also include a manual adjust valve to mechanically tune a performance of the fuel path to minimize an amount of adjustment by the electronically controlled fuel control valve to regulate (e.g., maintain) the air to fuel ratio. A controller may be coupled to the combustion engine and/or components of the fuel system (e.g., air and fuel mixer, electronically controlled fuel control valve, air and fuel control valve (e.g., throttle valve), etc.). The controller may be programmed to change the set AFR utilized by the electronically controlled fuel control valve based on the different physical and chemical properties of the fuel to be utilized. The air and fuel mixer may include a gas valve or gas metering valve (e.g., carburetor cone) having a specific geometry or profile that enables the gas valve to be utilized with a range of different fuels having different physical and chemical properties. Also, the gas valve's geometry and profile enables the gas valve to be utilized over a wide range of AFRs (e.g., up to a 16 to 1 AFR). The geometry of the gas valve in conjunction with the gas pressure regulator, electronically controlled fuel control valve, and manual adjust valve enables the combustion engine to be utilized with different fuels having different physical and chemical properties (e.g., from different sites such as natural gas field sites). For example, the fuel system and combustion engine may be utilized with different fuels having a heating value range and/or specific gravity range spanning from a low limit (e.g., lower end or lower threshold) to an upper limit (e.g. upper end or threshold) and the ratio of the upper limit to the lower limit is 3 to 1. The disclosed embodiments enable the combustion engine and associated fuel system to be utilized at different sites with different fuels for a wide variety of applications without having to change any hardware on the fuel system. Thus, a combustion engine and associated fuel system may be certified a single time (e.g., U.S. EPA Mobile certification) for utilization at the different sites. In addition, the disclosed embodiments save costs associated with hardware changes and stocking multiple certified engines for specific fuels.

Turning to the drawings,FIG. 1illustrates a block diagram of an embodiment of a portion of an engine driven power generation system10. As described in detail below, the system10includes an engine12having one or more combustion chambers14(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 18, 20, or more combustion chambers14). The engine12may include a reciprocating or piston engine (e.g., internal combustion engine). The engine12may include a spark-ignition engine. An air supply16is configured to provide a pressurized oxidant18, such as air, oxygen, oxygen-enriched air, oxygen-reduced air, or any combination thereof, to each combustion chamber14via an air and fuel mixer20(e.g., carburetor). The combustion chamber14is also configured to receive, via a fuel system22, a fuel24(e.g., a gaseous fuel such as unprocessed field gas from a natural gas field) from a fuel supply26. The fuel system22is configured to operate with different fuels having different physical and chemical properties (e.g., pure methane versus pure propane). For example, the fuels may include different chemical heat contents, specific gravities, hydrocarbon compositions, and/or other properties. For example, the fuel system22may operate with different fuels having a heating value range and/or specific gravity range spanning from a low limit (e.g., lower end or lower threshold) to an upper limit (e.g. upper end or threshold) and the ratio of the upper limit to the lower limit is 3 to 1. A fuel-air mixture32ignites and combusts within each combustion chamber14. The hot pressurized combustion gases cause a piston34adjacent to each combustion chamber14to move linearly within a cylinder36and convert pressure exerted by the gases into a rotating motion, which causes a shaft38to rotate. Further, the shaft38may be coupled to a load40, which is powered via rotation of the shaft38. For example, the load40may be any suitable device that may generate power via the rotational output of the system10, such as an electrical generator. Additionally, although the following discussion refers to air as the oxidant16, any suitable oxidant may be used with the disclosed embodiments. Similarly, the fuel24may be any suitable gaseous fuel, such as natural gas, associated petroleum gas, propane, biogas, sewage gas, landfill gas, coal mine gas, for example.

The system10disclosed herein may be adapted for use in stationary applications (e.g., in industrial power generating engines) or in mobile applications (e.g., in cars or aircraft). The engine12may be a two-stroke engine, three-stroke engine, four-stroke engine, five-stroke engine, or six-stroke engine. The engine12may also include any number of combustion chambers14, pistons34, and associated cylinders (e.g., 1-24). For example, in certain embodiments, the system10may include a large-scale industrial reciprocating engine having 4, 6, 8, 10, 16, 24 or more pistons34reciprocating in cylinders36. In some such cases, the cylinders36and/or the pistons34may have a diameter of between approximately 13.5-34 centimeters (cm). In some embodiments, the cylinders36and/or the pistons34may have a diameter of between approximately 10-40 cm, 15-25 cm, or about 15 cm. The system10may generate power ranging from 10 kW to 10 MW. In some embodiments, the engine12may operate at less than approximately 1800 revolutions per minute (RPM). In some embodiments, the engine12may operate at less than approximately 2000 RPM, 1900 RPM, 1700 RPM, 1600 RPM, 1500 RPM, 1400 RPM, 1300 RPM, 1200 RPM, 1000 RPM, 900 RPM, or 750 RPM. In some embodiments, the engine12may operate between approximately 750-2000 RPM, 900-1800 RPM, or 1000-1600 RPM. In some embodiments, the engine12may operate at approximately 1800 RPM, 1500 RPM, 1200 RPM, 1000 RPM, or 900 RPM. Exemplary engines12may include General Electric Company's Jenbacher Engines (e.g., Jenbacher Type 2, Type 3, Type 4, Type 6 or J920 FleXtra) or Waukesha Engines (e.g., Waukesha VGF, VHP, APG, 275GL), for example.

The fuel system22includes an electronically controlled fuel control valve configured to regulate (e.g., maintain a desired or set AFR or lambda) the air to fuel ratio of the air/fuel mixture32provided to the engine12in response to control signals from a controller such as an engine control unit42(e.g., ECU). The engine driven power generation system10may include the ECU42coupled to the engine12, different components of the fuel system22(e.g., air and fuel mixer20, electronically controlled fuel control valve, fuel and fuel control valve (e.g., throttle valve) in the air and fuel mixer20, etc.), and one or more sensors disposed throughout the system10(e.g., sensor in the air and fuel mixer20to measure air pressure). In certain embodiments, the components of the fuel system22may be coupled to one or more controllers separate from the ECU42or both the ECU42and the one or more controllers. The ECU42controls engine operations as well as may be programmed to change the set AFR utilized by the electronically controlled fuel control valve for a wide range of different fuels utilized by the engine12. The ECU42when changing between different fuels may also change engine ignition timing and desired AFR to an appropriate engine ignition timing and an appropriate desired AFR for the specific fuel oncoming to the engine12. Components of the fuel system22may act together to enable the electronically controlled valve to remain within a control range for both engine operating speeds and loads for a wide range of different fuels that the engine12may operate with.

The ECU42includes a processor44and a memory46(e.g., machine-readable medium). The ECU42may include the processor44or multiple processors. The processor44may include multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), system-on-chip (SoC) device, or some other processor configuration. For example, the processor44may include one or more reduced instruction set (RISC) processors or complex instruction set (CISC) processors. The processor44may execute instructions or non-transitory code. These instructions may be encoded in programs or code stored in a tangible non-transitory computer-readable medium, such as the memory46and/or other storage. The memory46, in the embodiment, includes a computer readable medium, such as, without limitation, a hard disk drive, a solid state drive, diskette, flash drive, a compact disc, a digital video disc, random access memory (RAM and/or flash RAM), and/or any suitable storage device that enables the processor44to store, retrieve, and/or execute instructions (e.g., software or firmware) and/or data (e.g., thresholds, ranges, etc.). The memory46may include one or more local and/or remote storage devices.

FIG. 2illustrates a schematic diagram of an embodiment of the fuel system22. The fuel system22may be coupled to the engine12described inFIG. 1. The fuel system22includes the air and fuel mixer20(e.g., carburetor) coupled to a fuel path48. The fuel system22is configured to operate with different fuels having different physical and chemical properties (e.g., pure methane versus pure propane). For example, the fuels may include different chemical heat contents, specific gravities, hydrocarbon compositions, and/or other properties. For example, the fuel system22may operate with different fuels having a heating value range and/or specific gravity range spanning from a low limit (e.g., lower end or lower threshold) to an upper limit (e.g. upper end or threshold) and the ratio of the upper limit to the lower limit is 3 to 1. For example, the heating value range for the different fuels may be between approximately 850 Btu/scf (7.5 cal(IT)/cm3) and 2350 Btu/scf (20.9 cal(IT)/cm3).

As depicted, the fuel system22includes an electronically controlled fuel control valve50disposed along the fuel path48. The electronically controlled fuel control valve50may be located upstream of the air and fuel mixer20. The electronically controlled fuel control valve50in response to control signals from the ECU42regulates (e.g., maintains) a desired AFR or lambda of an air/fuel mixture (e.g., for a wide range of fuels having different physical and chemical properties) provided to the engine12.

The fuel system22also includes a gas pressure regulator52(e.g., gas pressure regulator valve) disposed along the fuel path48that controls or regulates the pressure of the fuel in relation to an air pressure of the air and fuel mixer20. For example, the gas pressure regulator52may be coupled to a sensor or transducer54that measures a pressure of the air entering the air and fuel mixer20. The pressure of the fuel entering the air and fuel mixer20has a significant effect on the AFR when the engine12is starting, idling, or running under light loads. Adjustments to the gas pressure regulator52occur during, idling, or running under light loads prior to any adjustments to a manual adjust valve56. The gas pressure regulator52is disposed along the fuel path48upstream of both the air and fuel mixer20and the electronically controlled fuel control valve50.

The fuel system22also includes the manual adjust valve56disposed along the fuel path48that mechanically tunes the performance of the fuel path48to minimize an amount of adjustment by the electronically controlled valve50to regulate (e.g., maintain) the AFR. The manual adjust valve56(i.e., a position) is adjusted as the engine12approaches or nears full power (i.e., rated speed under full load). Although the manual adjust valve56is depicted inFIG. 2downstream of the electronically controlled valve50, the manual adjust valve56may be disposed along the fuel path48upstream or downstream of the electronically controlled valve50but downstream of the gas pressure regulator52. In certain embodiments, the manual adjust valve56may be part of the air and fuel mixer20(e.g., upstream of mixing valve58where it can be adjusted to restrict gas flow upstream of the mixing valve58). The gas pressure regulator52is disposed along the fuel path48between the air and fuel mixer20and the electronically controlled fuel control valve50. The gas pressure regulator52and the manual adjust valve56, acting together, enable the electronically controlled valve50to remain within a control range for both engine operating speeds and loads for a wide range of different fuels that the engine12may operate with.

As depicted, the air and fuel mixer20(e.g., carburetor) includes a mixing valve58(e.g., air and gas valve mixer) and an air and fuel control or load control valve60(e.g., throttle valve) located downstream of the mixing valve58. The air and fuel control valve60controls the amount of fluid (i.e., combustible air/fuel mixture) provided to the engine12affecting the load or power of the engine12. The air and fuel control valve60is coupled to the ECU which provides control signals to actuate the valve60(e.g., via an actuator) and changes positions of the valve60. The mixing valve58mixes the air and the fuel (e.g., fuel path48) received by the air and fuel mixer20. The mixing valve58includes a gas valve or gas-metering valve (e.g., carburetor cone). The shape of the gas valve is configured to maintain the correct AFR over the entire operating range of the engine12. As discussed in greater detail below, the gas valve is shaped (i.e., has a profile) that enables the gas valve to be utilized with a wide range of different fuels having different physical and chemical properties as described above. The gas valve enables the air and fuel mixer20to operate up to an AFR of 16 to 1. The gas valve also enables the air and fuel mixer20to operate with fuel and air pressures between 0 and 12 inches water column (2.99 kPa). In addition, the gas valve further enables the air and fuel mixer20to operate from an approximately 10 percent engine load to 100 percent engine load for the wide range of different fuels.

In adjusting the settings for the fuel system22in response to utilizing a different fuel. The ECU42changes and/or sets the desired AFR based on the specific fuel to be utilized with the engine12. During startup or the beginning of engine operation, the electronically controlled valve50is controlled to desired AFR by the ECU42to regulate the AFR of the air/fuel mixture provided to the combustion engine12. Subsequent to beginning operation of the combustion engine12and prior to the combustion engine reaching full speed, a pressure of the fuel within the fuel path48is adjusted based on the physical and chemical properties of the fuel via adjustment of the gas pressure regulator52. Subsequent to adjusting the pressure of the fuel and while the combustion engine12approaches or nears full speed, a position of the manual adjustment valve56is tracked and adjusted to mechanically tune the performance of the fuel path22to minimize an adjustment by the electronically controlled fuel control valve50to regulate the AFR. Together the shape of the gas valve and regulation of the electronically controlled fuel control valve50, the gas pressure regulator52, and the manual adjust valve56enable the fuel system22to operate with different fuels that differ in physical and chemical properties. Thus, the combustion engine12and associated fuel system22may be utilized at different sites with different fuels for a wide variety of applications without having to change any hardware on the fuel system22. Also, the combustion engine12and associated fuel system22may be certified a single time (e.g., U.S. EPA Mobile certification) for utilization at the different sites. Thus, saving costs associated with hardware changes and stocking multiple certified engines for specific fuels.

FIG. 3is a schematic diagram of an embodiment of an air and fuel mixer20(e.g., carburetor). The air and fuel mixer20includes an air inlet62configured to receive air and an air/fuel mixture outlet64to discharge an air/fuel mixture to the combustion engine12. The air and fuel mixer20also includes the mixing valve58(e.g., air and gas valve mixer) located upstream or above the air and fuel control or load control valve60(e.g., throttle valve). The mixing valve58includes a fuel inlet66that provides fuel to a fuel chamber68. The mixing valve58includes a jet70coupled to the fuel chamber68(which includes an inner diameter that forms a fuel outlet) and a gas valve or gas metering valve72(e.g., tapered gas valve or carburetor cone) that moves into and out (as indicated by double arrow74) of the inner diameter of the jet70to regulate how much fuel flows from the fuel chamber68and out of the mixing valve58into the air and fuel mixer20. Thus, the gas valve72acts a restriction to fuel flow. The mixing valve58is configured to create a slight pressure drop (e.g., negative pressure) as air76is drawn into the air and fuel mixer20through the air inlet62. A negative pressure signal is communicated to an upper side78of a diaphragm80through passages in the mixing valve58, while atmospheric pressure acts on an under side82of the diaphragm to force it upward. An amount of negative pressure generated is determined by the position of the air and fuel control valve60and an amount of air flowing through the air and fuel mixer20. As the diaphragm80rises (e.g., with valve60open), it lifts the gas valve72from the jet70or seat that enables fuel (as indicated by arrow84) to exit out of the fuel chamber68and the mixing valve58to mix with the air76to form an air/fuel mixture86that exits via the outlet64to the engine12.

The shape (e.g., geometry or profile) of the gas valve72or carburetor cone maintains the correct AFR over the entire operating range of the engine12. The shape of the gas valve72is most important in the low flow (e.g., starting and light load) operating conditions. As discussed in greater detail below, the gas valve72is shaped (i.e., has a profile) to enable the gas valve72to be utilized with a wide range of different fuels having different physical and chemical properties as described above. The gas valve72enables the air and fuel mixer20to operate up to an AFR of 16 to 1. The gas valve72also enables the air and fuel mixer20to operate with fuel and air pressures between approximately 0 and 12 inches water column (2.99 kPa). In addition, the gas valve72further enables the air and fuel mixer20to operate from an approximately 10 percent engine load to 100 percent engine load for the wide range of different fuels.

FIG. 4is a side view of an embodiment of the gas valve72(e.g., carburetor cone) of the air and fuel mixer20(e.g., carburetor). In the following discussion, reference may be made to axial direction88, a radial direction90, and/or a circumferential direction92of the engine12defined relative to a central axis94of the gas valve72. The gas valve72includes a base portion96(e.g., seat or annular base portion) and a conical portion98(e.g., annular conical portion). The gas valve72also includes a first end100at the base portion96and a second end102at a distal end (i.e., relative to the base portion96) of the conical portion98. The base portion96includes an annular wall104that defines a diameter, A, adjacent the first end100. The conical portion98includes an annular, angled wall106extending between the base portion96and the second end102. At the second end102, the wall106defines a diameter, B. As depicted, a ratio of diameter A to diameter B may range from 2:1 to 3:1 and all subranges therebetween. The diameter A may be between approximately 2.7 and 3.2 cm. In certain embodiments, the diameter A may be approximately 3.175 cm. The diameter B may be between 1 and 1.4 cm. The angular wall106includes an angle, C°, which is constant along the wall106in the axial direction88. The angle C° range between approximately 28 and 32 degrees and subranges therebetween. For example, the angle C° may be approximately 28, 29, 30, 31, or 32 degrees. The gas valve72includes a height or length, D, from the first end100to the second end102in the axial direction88. The base portion96includes a height or length, E, in the axial direction88. The diameter, A, of the base portion96may be constant along the height, E. The ratio of height, D, to the height, E, may range from 3.6:1 to 4.2:1 and all subranges therebetween.

Technical effects of the disclosed embodiments include providing the fuel system22for the combustion engine12that can be utilized with a wide range of different fuels having different physical and chemical properties (e.g., chemical heat content, specific gravity, hydrocarbon composition, etc.) with the combustion engine12. The fuel system22may include the air and fuel mixer22that includes the gas valve72having a geometry or profile that enables it to be utilized over the wide range of different fuels. The fuel system22includes the path48that includes the gas pressure regulator52, the electronically controlled fuel control valve50, and the manual adjustment valve56. Together the shape of the gas valve72and regulation of the electronically controlled fuel control valve50, the gas pressure regulator52, and the manual adjust valve56enable the fuel system22to operate with different fuels that differ in physical and chemical properties. Thus, the combustion engine12and associated fuel system22may be utilized at different sites with different fuels for a wide variety of applications without having to change any hardware on the fuel system22. Also, the combustion engine12and associated fuel system22may be certified a single time (e.g., U.S. EPA Mobile certification) for utilization at the different sites. Thus, saving costs associated with hardware changes and stocking multiple certified engines for specific fuels.