# Patent

## Title
Multi-fuel system and method

## Abstract

A method provides for operating an engine configured to use a plurality of differing fuels. The method includes determining a fuel combustion ratio of the plurality of the fuels associated with at least one engine cylinder of the engine based at least in part on one or more of a plurality of characteristic profiles. This maintains one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values. The fuel combustion ratio includes a ratio of the plurality of fuels to be delivered to the at least one engine cylinder. A fuel delivery system delivers the plurality of fuels to the at least one engine cylinder based on the fuel combustion ratio.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of International Application No. PCT/US12/64929, which was filed on 14 Nov. 2012. International Application No. PCT/US12/64929 claims priority to U.S. application Ser. No. 13/328,438, which was filed on 16 Dec. 2011, now U.S. Pat. No. 8,682,512.


BACKGROUND
1. Technical Field
Aspects of the invention relate to a multi-fuel system for engines and an associated method of operation.
2. Discussion of Art
Some mobile assets may have engines, for example, compression-ignition engines operate by directly injecting a fuel (e.g., diesel fuel) into compressed air in one or more piston-cylinder assemblies, such that the heat of the compressed air ignites the fuel-air mixture. The direct fuel injection atomizes the fuel into droplets, which evaporate and mix with the compressed air in the combustion chambers of the piston-cylinder assemblies. The fuel-air ratio affects engine performance, efficiency, exhaust constituents, and other engine characteristics. Exhaust emissions may include carbon oxides (e.g., carbon monoxide), nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM). The amount and relative proportion of these constituents may vary in response to changes in the fuel-air mixture, fuel quality, compression ratio, injection timing, environmental conditions (e.g., atmospheric pressure, temperature, etc.), and so forth.
A dual-fuel engine is an alternative internal combustion engine designed to run on more than one fuel, for example, natural gas and diesel, each stored in separate vessels. Such engines are capable of burning a mixture of the resulting blend of fuels in the combustion chamber and the fuel injection or spark timing may be adjusted according to the blend of fuels in the combustion chamber. For dual fuel operation where one of the fuel is premixed with air, a reduction in nitrogen oxide (NOx) and particulate matter (PM) emissions is enabled by combusting a relatively larger fraction of the premixed fuel. It may be desirable to have a system and method for engines operating on more than one fuel that differs from those currently available.
BRIEF DESCRIPTION
In accordance with one embodiment, a method is provided for operating an engine configured to use a plurality of differing fuels. The method includes determining a fuel combustion ratio of the plurality of the fuels associated with at least one engine cylinder of the engine based at least in part on one or more of a plurality of characteristic profiles. This is to maintain one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values. The fuel combustion ratio includes a ratio of the plurality of fuels to be delivered to the at least one engine cylinder. A fuel delivery system delivers the plurality of fuels to the at least one engine cylinder based on the fuel combustion ratio.
In one embodiment, a fuel system is provided that includes a fuel controlling unit. The fuel controlling unit delivers a plurality of fuels to at least one engine cylinder of an engine based at least in part on a fuel combustion ratio. The fuel combustion ratio comprises a ratio of the plurality of fuels to be delivered to the at least one engine cylinder and is based at least in part on one or more of a plurality of characteristic profiles. The fuel controlling unit maintains one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values.
In one embodiment, an engine is disposed within a mobile asset operable to travel along a defined path. A global positioning sensor provides, and the fuel controlling unit receives from the global positioning sensor, location information and thereby determines the one or more of the plurality of characteristic profiles as a function of time and a corresponding location of the mobile asset along the defined path.



DRAWINGS
These and other features and aspects of the invention may be understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
FIG. 1 is a diagrammatical representation of a mobile asset, for example a locomotive, having a fuel controlling unit in accordance with an exemplary embodiment of the present invention;
FIG. 2 is a diagrammatical representation of a mobile asset with detailed view of a fuel controlling unit in accordance with an exemplary embodiment of the present invention; and
FIG. 3 is a flow diagram illustrating exemplary steps involved in optimization of fuel in a mobile asset in accordance with an exemplary embodiment of the present technique.



DETAILED DESCRIPTION
In accordance with the embodiments discussed herein, a method and a fuel system for use operating an engine using a plurality of fuels is disclosed. The engine may power or propel a stationary asset or a mobile asset.
A suitable mobile asset can be a vehicle or other engine powered assembly. Suitable vehicles may include locomotives, passenger and non-passenger automotive vehicles, hybrid vehicles, off-highway vehicles, on-road vehicles (such as tractor trailers), tracked vehicles, air-borne vehicles, rail vehicles, mining vehicles, industrial and construction vehicles, and marine vessels. Suitable mobile assets may use other fuels instead of diesel and natural gas. Other suitable liquid fuels may include gasoline, kerosene, ethanol, bio-diesel, and the like. Other suitable gaseous fuels may include propane, hydrogen, syn-gas, and the like.
A mobile asset's configuration may include performance variables such as the peak output rating of the mobile asset, the correlation between the power level settings and the percentage of full power generated, engine emissions curves, acoustic emissions, electro-magnetic emissions, the number of traction motors used, fuel economy performance, adhesion limits, the organization, presentation and functionality of operator controls, communications protocol, auxiliary functions, security measures, and the like. External factors that can affect the mobile asset's desired configuration can include tax liabilities for operation, weather considerations, damage risk (due to crime or conflict), proximity to population centers, and the like. The control of fuel usage may be determined with reference to various characteristic profiles associated with the engine operation and/or mobile asset and may vary as a function of time and a corresponding location of the asset along the path.
A reduction in nitrogen oxide (NOx) and particulate matter (PM) emissions may be enabled by combusting a relatively larger fraction of premixed fuel. Relative costs and availability of different fuels may be in flux. For example, in some embodiments, diesel and natural gas may be utilized to drive the engine. If the cost of diesel increases relative to the cost of the natural gas, more natural gas may be used resulting in reduced cost and emissions. If the cost of natural gas increases relative to the cost of the diesel, then more diesel may be used to drive the engine.
The term “profiles” is used herein to describe the overall operating parameters and conditions of the engine and/or mobile asset. These profiles may alter the manner in which the operating systems of the mobile asset can be controlled in response to operational inputs.
Referring to FIG. 1, a mobile asset 10 moving from a first operating point 12 to a second operating point 14 along a defined path 16 is disclosed. In the illustrated embodiment, the mobile asset may be driven by an engine 18 using a plurality of fuels. A fuel controlling unit 20 may control fuel utilization based on cost and availability while ensuring emission compliance along the travel from the first operating point to the second operating point along the defined path.
Referring to FIG. 2, the mobile asset includes a turbocharger 22 and the compression-ignition engine, e.g. the diesel engine. A motor-generator unit (not shown) may be mechanically coupled to the turbocharger. As discussed in further detail below, embodiments of the technique provide monitoring and control features, such as sensors and control logic, to control/control the utilization of fuel.
The illustrated engine includes an air intake manifold 24 and an exhaust manifold 26. The turbocharger includes a compressor 28 and a turbine 30 and may be operated to supply compressed air to the intake manifold for combustion within the engine. The turbine may be coupled to the exhaust manifold for extracting energy from exhaust gases for rotating a turbocharger shaft 32 connected to the compressor. The compressor draws ambient air through a filter 34 and provides compressed air to a heat exchanger 36. The temperature of air may be increased due to compression. The compressed air flows through the heat exchanger such that the temperature of air may be reduced prior to delivery into the intake manifold of the engine. In one embodiment, the heat exchanger may be an air-to-water heat exchanger, which utilizes a coolant to facilitate removal of heat from the compressed air. In another embodiment, the heat exchanger may be an air-to-air heat exchanger, which utilizes ambient air to facilitate removal of heat from compressed air. The fuel controlling unit may be used for another type of engine or mobile asset using a plurality of fuels so as to control fuel utilization based on cost and availability while ensuring emission compliance during travel.
The fuel controlling unit may include a plurality of sensors and a control unit 38. Suitable sensors may include one or more of an engine emission level sensor 40, a fuel usage level sensor 42, a power output sensor 44, an engine load sensor 46, an engine speed sensor 48, fuel cost meter 50, a fuel injection profile sensor 52, a knock sensor (not shown), an oxygen content sensor (not shown), temperature sensors (not shown), pressure sensors (not shown), a valve sensor (not shown), and the like. A global positioning sensor (GPS) 53 may communicate with the fuel controlling unit.
A suitable control unit may be an electronic fuel injection control unit for the engine or an electronic logic control unit that may be programmable by a user. The control unit may produce a signal to control operation of a fuel delivery system 41. The fuel delivery system may have one or more fuel injection pumps, gas control valves, a communication path to regasification unit 67 (which, in one embodiment, may be located on another mobile asset coupled to the mobile asset that supports the engine and the fuel controlling unit), a gas recirculation pump, and the like. The fuel injection pumps may provide fuel, under pressure, to a plurality of plurality of fuel injectors (not shown) for injecting fuel into a cylinder of the engine.
A piston (not shown) may be slidably disposed in each cylinder and reciprocates between a top dead center and a bottom dead center position. The control unit may receive an engine emission level signal from the level sensor, a fuel usage level signal from the sensor, a power output signal from the power sensor, an engine load signal from the load sensor, an engine speed signal from the speed sensor, fuel cost from the meter, and a fuel injection profile signal from the injection sensor.
The control unit may receive one or more signals associated with at least one of a distance from the first operating point to the second operating point along the defined path, terrain profile associated with the path, ambient temperature and pressure, time required to traverse the distance, and location of one or more fuel stations along the defined path from the GPS unit. The terrain profile can include information relating to the path, such as the grade, the curvature, the altitude, and the path condition. Path condition can include the state of repair or wear of the path, for example the condition of rail track.
The control unit may include a memory 54, an algorithm 56, and a processor 58. The memory may store information associated with the mobile asset, the path, the engine, environmental conditions (such as snow during a winter or leaf cover in the fall), and the like. The memory may store information relating to average temperatures and pressures associate with either the ambient or of operations of the engine. Other stored information may include maps, tables and models relating to, for example, fuel injection timing and pressure, engine speed, power output of the engine, engine emission level, fuel usage level, engine load, fuel cost, distance from the first operating point to the second operating point along the defined path, terrain profile associated with the path, ambient temperature and pressure, time required to traverse the distance, and location of one or more fuel stations along the defined path, or the like.
Regarding injection timing, more than diesel fuel is contemplated herein and the term is used to indicate aspects of fuel flow (both gas and liquid) into the cylinder relative to the combustion cycle. Thus, injection timing information may include a duration that a solenoid opens in the injector to ingress fuel into the cylinder, the pressure of the fuel being injected, the timing of the injection relative to the piston location in the cylinder, and the like. Additionally, injection timing may additionally refer to the fumigation or injection of gaseous fuel into the air intake valve for the cylinder. In this aspect, injection timing may refer to the flow rate of the gas, the volume of EGR in the manifold, the oxygen content (calculated or measured) in the manifold, and the like. Furthermore, the memory may store actual sensed/detected information from the above-mentioned sensors.
The algorithm facilitates the processing of signals from one or more of the plurality of sensors. The characteristic profiles associated with the mobile asset may include the output from the sensors and information stored in the memory.
The processor may include a range of circuitry types, such as a microprocessor, a programmable logic controller, a logic module, etc. The processor in combination with the algorithm may perform the various computational operations relating to determination of a combustion ratio of the plurality of fuels to be delivered to at least some cylinders of the engine. The combustion ratio is determined by the ratio of the plurality of fuels delivered to cylinders of the engine. For an engine using diesel and natural gas, a combustion ratio would be ratio of diesel content to natural gas content to be delivered to each cylinder. As noted, the diesel content may be measured as an injection time and diesel pressure through an injector. The natural gas content may be measured by a flow rate through a gas valve as metered into an air intake stream. The ratio, then, could be selected as the energy content of each fuel component present in a cylinder during combustion. Alternatively, other calculations may be used to form the ratio.
The processor may determine the fuel combustion ratio of the plurality of the fuels associated with each engine cylinder of the mobile asset based on the plurality of characteristic profiles. In some embodiments, the processor determines the combustion ratio based on the output from the sensors 40, 42, 44, 46, 48, 50 and 52. In certain other embodiments, the processor 58 determines the combustion ratio based on the output from the GPS 53. In a specific embodiment, the processor 58 utilizes information from the GPS 53 in conjunction with the information from the other sensors 40, 42, 44, 46, 48, 50 and 52 to determine the combustion ratio. Additionally, the processor 58 may also use the information stored in the memory 54.
In the illustrated embodiments, the mobile asset has a first fuel source 60 and a second fuel source 62 for feeding a first fuel and a second fuel respectively, to corresponding cylinders of the engine. The first and second fuels may be injected to the cylinders via the intake manifold or may be injected directly to the cylinders, or a combination of both or other ingress techniques. More than two fuels may be used.
The processor outputs a control signal to the fuel delivery system to deliver the plurality of fuels to the cylinders based on, at least partially, the combustion ratio. The combustion ratio may be determined to maintain a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values. In one embodiment, an actual cost associated with usage of the plurality of fuels may be maintained to less than or equal to a defined threshold cost; an actual emission level associated with usage of the plurality of fuels may be maintained to less than or equal to a defined threshold emission level; and, an actual quantity of fuel in the mobile asset may be maintained to less than or equal to a defined threshold quantity. The fuel controlling unit may control fuel utilization, and the ratio of use of the plural fuels relative to each other, based on cost and availability while ensuring emission compliance along the entire travel from the first operating point to the second operating point along the defined path. For example, if two fuels are used, the controlling unit may control a relatively larger usage of a secondary fuel and so that adequate primary fuel exists to complete the travel, taking into consideration the characteristics profiles.
Relative costs, purity, type and availability of different fuels may be in flux. Also, proportions of different fuels may also have an effect on the exhaust constituents from the engine. In one embodiment, the fuel controlling unit takes into consideration sensed engine emission level, a fuel usage level (i.e. quantity of fuel required for the travel, remaining quantity of fuel in the fuel sources 60, 62) the engine power output, the engine load, the engine speed, fuel cost, and the fuel injection profile. In an embodiment, the fuel controlling unit may consider distance from the first operating point to the second operating point along the defined path, terrain profile associated with the path, ambient temperature and pressure, time required to traverse the distance, and location of one or more fuel stations along the defined path, or the like. Other suitable parameters may be also envisaged.
Parameters may vary dynamically as a function of time and location of asset. In accordance with an embodiment, the plurality of characteristic profiles associated with the mobile asset may be determined as a function of time and a corresponding location of the mobile asset along the defined path. Hence, the fuel controlling unit may also determine the fuel combustion ratio as a function of time and a corresponding location of the mobile asset based on the one or more of the plurality of characteristic profiles. The frequency of sensing the characteristics profiles and determination of the combustion ratio may be based on the type of application.
In certain embodiments, the control unit may output data to a user interface 64. The user interface may facilitate inputs via a touch screen 66 from a user to the control unit and provide a mechanism through which a user can manipulate data and sensed properties from the control unit. The user interface may include a command line interface, menu driven interface, and/or graphical user interface. The control unit may be operable to adjust the combustion ratio affecting the cost and engine emissions associated with the fuel usage. In some embodiments, the control unit may communicate to a user via the user interface whether it may be possible to reach a predetermined destination with available of fuel(s) in the asset, while meeting emissions targets.
Referring to FIG. 3, a flow diagram 68 illustrating a plurality of steps involved in optimization of fuel for a mobile asset may be disclosed. Initially, a plurality of characteristic profiles associated with the mobile asset moving from one operating point to another operating point along a defined path may be determined as represented by the step 70. In one embodiment, the characteristic profiles may include asset sensed information, the characteristics profiles may include GPS information, the characteristics profile may include memory stored information, and the characteristics profile may be determined as a function of time and location of the mobile asset. Then, a fuel combustion ratio of the plurality of the fuels associated with at least one engine cylinder of the mobile asset may be determined based on the plurality of characteristic profiles as represented by the step 72. The fuel combustion ratio refers to a ratio of the plurality of fuels to be delivered to the at least one engine cylinder of the mobile asset, and may be determined as a function of time and location of the mobile asset.
A fuel delivery system may be controlled based on the determined fuel combustion ratio as represented by the step 74. The fuel delivery system delivers the plurality fuels based on the determined fuel combustion ratio as represented by the step 76. As a result, the actual emission level associated with usage of the plurality of fuels may be maintained to less than or equal to a defined threshold emission level as represented by the step 78. An actual quantity of the plurality of fuels in the mobile asset may be maintained less than or equal to a defined threshold quantity as represented by the step 80. The actual cost associated with usage of the plurality of fuels may be maintained to less than or equal to a defined threshold cost as represented by the step 82.
In one embodiment, a method includes determining a plurality of characteristic profiles associated with a mobile asset moving from a first operating point to a second operating point along a defined path. A fuel combustion ratio is determined for the plurality of the fuels associated with at least one engine cylinder of the mobile asset based on the plurality of characteristic profiles so as to maintain a plurality of actual values associated with usage of the plurality of fuels to less than or equal to defined corresponding threshold values. The fuel combustion ratio is a ratio of the plurality of fuels to each other, and may be calculated in one of several ways depending on the application. As used here, suitable determination methods may include by measured volume, mass, flow rate, injection time, and the like, and may take into account purity, energy density, the presence, type and quantify of fuel additives, environmental considerations, EGR content, and the like. A fuel delivery system of the mobile asset may deliver the plurality of fuels to the at least one engine cylinder based on the fuel combustion ratio.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
This written description uses examples to disclose the invention, and to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

## Claims

1. A method for operating an engine configured to use a plurality of differing fuels, the method comprising:
determining a fuel combustion ratio of the plurality of the fuels associated with at least one engine cylinder of the engine based at least in part on one or more of a plurality of characteristic profiles comprising at least fuel cost and a location of one or more fuel stations along a defined path of a mobile asset in which the engine is disposed, to maintain one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values; wherein the fuel combustion ratio comprises a ratio of the plurality of fuels to be delivered to the at least one engine cylinder; and
controlling a fuel delivery system to deliver the plurality of fuels to the at least one engine cylinder based on the fuel combustion ratio, where the plurality of characteristic profiles further comprises global positioning sensor (GPS) information, terrain profile associated with a defined path, ambient temperature, and ambient pressure.

2. The method of claim 1, wherein the plurality of characteristic profiles comprises at least one asset sensed information comprising at least one of an engine emission level, a fuel usage level, a power output, an engine load, an engine speed, or a fuel injection profile.

3. The method of claim 1, further comprising controlling a measured exhaust emission constituent level relative to a defined threshold emission level.

4. A fuel system, comprising:
a fuel controlling unit configured to deliver a plurality of differing fuels to at least one engine cylinder of an engine based at least in part on a fuel combustion ratio,
wherein the fuel combustion ratio comprises a ratio of the plurality of fuels to be delivered to the at least one engine cylinder and is based at least in part on one or more of a plurality of characteristic profiles including a condition of a defined path on which a mobile asset in which the engine is disposed is operable to travel, and
thereby the fuel controlling unit is operable to maintain one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values, where the condition of the defined path includes a state of wear of the defined path.

5. The system of claim 4, wherein the fuel controlling unit is configured to receive fuel cost information, and to control the fuel combustion ratio associated with the plurality of fuels based at least in part on the fuel cost information.

6. The system of claim 4, wherein the system further comprises a global positioning sensor and the fuel controlling unit is operable to receive location information from the global positioning sensor and thereby to determine the one or more of the plurality of characteristic profiles as a function of time and a corresponding location of the mobile asset along the defined path.

7. The system of claim 6, wherein the plurality of characteristic profiles comprises a distance from a first operating point to a second operating point along the defined path, a terrain profile associated with the defined path, time required to traverse the distance, an altitude, and a location of a fuel station along the defined path.

8. The system of claim 4, wherein the plurality of characteristic profiles comprises ambient temperature and pressure.

9. The system of claim 4, wherein the fuel controlling unit is further configured to deliver the plurality of differing fuels to the at least one engine cylinder of the engine to maintain an actual emission level associated with usage of the plurality of fuels relative to a defined threshold emission level.

10. The system of claim 4, wherein the fuel controlling unit is configured to maintain an actual quantity of at least one of the plurality of fuels in the mobile asset to less than or equal to a defined threshold quantity for that fuel.

11. The system of claim 4, further comprising one or more sensors operable to communicate sensor information with the fuel controlling unit, and the fuel controlling unit is operable to receive the sensor information and thereby to determine the one or more of the plurality of characteristic profiles.

12. The system of claim 11, wherein the sensor information includes at least one of an engine exhaust component emission level or an engine exhaust component oxygen level.

13. The system of claim 11, wherein the sensor information includes at least one of a fuel usage level or an available fuel quantity level.

14. The system of claim 11, wherein the sensor information includes at least one of an engine power output level, an engine load, or an engine speed.

15. The system of claim 11, wherein the sensor information includes fuel injection timing information comprising a duration of injection or a fuel pressure.

16. The system of claim 11, wherein the sensor information includes a knock level.

17. The system of claim 16, wherein the fuel controlling unit is configured to respond to receipt of the sensor information including the knock level that is greater than a determined threshold knock level by changing the fuel combustion ratio.

18. The system of claim 4, wherein the fuel controlling unit is configured to signal a fuel demand to a regasification unit to supply at least one of the plurality of fuels.

19. A vehicle comprising:
a fuel controlling unit configured to deliver a plurality of differing fuels to at least one engine cylinder of an engine based at least in part on a fuel combustion ratio, wherein the fuel combustion ratio comprises a ratio of the plurality of fuels to be delivered to the at least one engine cylinder and is based at least in part on one or more of a plurality of characteristic profiles,
one or more sensors operable to communicate with fuel controlling unit sensor information, the fuel controlling unit operable to receive the sensor information and thereby to determine the one or more of the plurality of characteristic profiles,
the sensor information including a knock level, and wherein the fuel controlling unit is configured to respond to receipt of the sensor information including the knock level that is greater than a determined threshold knock level by changing the fuel combustion ratio, and thereby the fuel controlling unit is operable to maintain one or more of a plurality of actual values associated with usage of the plurality of fuels relative to defined corresponding threshold values, and
the fuel controlling unit is further configured to signal a fuel demand to a regasification unit to supply at least one of the plurality of differing fuels.