Puel Identification and Control Svytem for an Internal Combustion Engine Using an Aqueous Fuel Emulsion

Technical Field

The present invention relates to a fuel identification and control system for an internal combustion engine, and more particularly, to a method and system for the detection and identification of a transported fuel within a fuel delivery system of a flexible fuel engine that utilizes an aqueous fuel emulsion as a source of fuel. Once identified, the fuel identi ication and control system optimizes the engine operating parameters for the identified fuel.

Background Art

Recent developments in aqueous fuels has resulted in a number of aqueous fuel emulsions comprised essentially of a carbon based fuel, water, and various additives. Although the water content of aqueous fuel emulsions vary, for purposes of this application, aqueous fuel emulsions include such fuel emulsions having a water content of 20 percent by weight or greater. These high water content aqueous fuel emulsions may play a key role in finding a cost- effective way for internal combustion engines including, but not limited to, compression ignition engines (i.e. diesel engines) to achieve the reduction in emissions below the mandated levels without significant modifications to the engines, fuel systems, or existing fuel delivery infrastructure.

Advantageously, such aqueous fuel emulsions tend to reduce or inhibit the formation of nitrogen oxides (NOx) as well as reduce or inhibit the formation of par iculates (i.e. combination of soot

and hydrocarbons) by altering the way the fuel is burned in the engine. Specifically, the aqueous fuel emulsions are burned at somewhat lower temperatures than a comparable non-aqueous fuel due to the presence of water. This, coupled with the realization that at higher peak combustion temperatures, more NOx is typically produced in the engine exhaust, one can readily understand the advantage of using such aqueous fuel emulsions. Thus, the reduction in NOx is achieved using aqueous fuel emulsions primarily because an aqueous fuel emulsion has a lower peak combustion temperature. The actual reduction achieved, however, depends on a number of factors including the composition of the aqueous fuel emulsion (e.g. fuel to water ratio) , engine/ignition technology, engine operating conditions, etc. Moreover, having a lower peak combustion temperature does not necessarily mean that the aqueous fuel is providing less total energy or doing less work for a given mass of hydrocarbon fuel. Rather, the addition of water only requires a proportional increase in the volume of aqueous fuel to be injected in order to achieve the equivalent amount of work. However, as the volume of fuel that has to be injected increases, the engine performance considerations change. The additional volume of fuel required in such systems in order to achieve the same amount of work also imposes additional constraints and other design considerations in the fuel delivery systems, fuel control systems, fuel storage systems and other related systems in the internal combustion engine. Thus where aqueous fuel emulsions are used, selected changes to the engine system must be incorporate .

Incorporating such fuel system changes is relatively straightforward except where the engine is a flex-fuel engine. Many compression ignition engine designs that could utilize an aqueous fuel emulsion could also be adapted to utilize other, more conventional fuels. An engine that is adapted to use more than one fuel type and periodically switch between such fuels is broadly referred to as a flex- fuel engine. In the operation of flex-fuel engines, it is often necessary to identify the fuel mixture being used and then appropriately make adjustments to certain engine operating characteristics. However, due to the unique characteristics of many aqueous fuel emulsions, the detection of the fuel is challenging and the adjustments in the fuel/engine control systems are much more complex and more significant than many of the prior art systems.

Thus, there is a need for a method and system for adjusting or otherwise optimizing selected engine performance characteristics of a flex-fuel engine that is particularly adapted to utilize an aqueous fuel emulsion as one source of fuel . The optimization of the engine performance characteristics should be based, in part, on the detection and identification of the fuel in the fuel delivery system.

Summary of the Invention The present invention addresses the above and other needs by providing a method and system for the detection and identification of the fuel being transported within a fuel delivery system of a flex- fuel engine system, wherein one of the fuels is an

aqueous fuel emulsion. Once identified, the fuel identification and control system optimizes the engine operating parameters for the identified fuel.

In one embodiment, the invention may be characterized as a fuel identification and control system for a flex-fuel engine system that utilizes an aqueous fuel emulsion as one source of fuel and a conventional fuel as another source of fuel. The fuel identification and control system includes a fuel identification sensor that provides an input to the control unit for the purposes of effectuating precise control over the fuel system, based on the type of fuel that is to be injected. The fuel identification sensor may be in the form of an optical sensor, conductivity meter, or similar device capable of distinguishing the aqueous fuel emulsion from a conventional fuel based on the optical, electrical or physical differences between the two types of fuels.

The invention may also be characterized as a method for the fuel identification and control in a flex-fuel engine adapted to use an aqueous fuel emulsion. In a broad sense, the preferred method involves: (a) detecting selected characteristics of the fuel in a fuel line of the flex-fuel engine proximate the fuel injectors using an optical, electrical or similar such fuel identification sensor; (b) identifying the fuel in the fuel line as either an aqueous fuel emulsion or a conventional diesel fuel based on the detected fuel characteristics determined by the fuel identification sensor; (c) using the specialized engine control algorithms associated with the aqueous fuel emulsion where the fuel is identified as an aqueous fuel emulsion; and (d) using the engine control algorithms associated with conventional fuel

where the fuel is identified as other than the aqueous fuel emulsion. In the presently disclosed embodiment, the engine control algorithms include specialized fuel injection timing maps, maximum fueling maps, engine cold start algorithms, light load algorithms, fuel switching control algorithms, and fuel metering algorithms.

Brief Description of the Drawings

The above and other aspects, features, and advantages .of the present invention will be more apparent from the following, more descriptive description thereof, presented in conjunction with the following drawings, wherein:

FIG.l is a schematic representation of the fuel identification and control system for a flex-fuel engine adapted for using an aqueous fuel emulsion in accordance with the present invention; FIG. 2 is a schematic representation of an embodiment of the fuel identification sensor in the fuel identification and control system of FIG. 1 that identifies the fuel based on the optical properties of the fuel; FIG. 3 is a schematic representation of an alternate embodiment of the fuel identification sensor of FIG. 1 that identifies the fuel based on the electrical properties of the fuel; and

FIG. 4 is a block diagram broadly depicting the preferred method for fuel identification and control in a flex-fuel engine adapted to use an aqueous fuel emulsion.

Corresponding reference numbers indicate corresponding components throughout the several views of the drawings.

Detailed Description of the Invention

The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principals of the invention. The scope and breadth of the invention should be determined with reference to the claims.

Turning now to the drawings and particularly to FIG. 1, there is shown a schematic representation of the fuel identification and control system for a flexible-fuel engine adapted for using an aqueous fuel emulsion as one source of fuel. As seen therein, the fuel identification system 10 includes a fuel delivery system that includes, for example, a first fuel tank 12, a second fuel tank 13, fuel line 14, fuel valve

15, fuel transfer pump 16, and fuel return conduit 18. The fuel identification and control system 10 further includes a fuel identification sensor 20 interposed in operative association along the fuel line 14 between the fuel tanks 12, 13 and the engine 22 downstream of the fuel transfer pump 16 and preferably close to the fuel injectors. The fuel identification sensor 20 is adapted to detect selected fuel characteristics of the fuel 24 being transported to the engine 22 within fuel line 14.

The fuel identification sensor 20 provides a fuel type signal 28 for the purpose of identifying the fuel 24 within the fuel delivery system based on the detected fuel characteristics. As with all flex-fuel

engines identifying the fuel used at any given time is of primary interest. The fuel identification sensor 20 in the preferred embodiment is adapted for identifying the fuel 24 being transported therein as either an aqueous fuel emulsion 25 or a conventional fuel 26, such as diesel fuel. In the present embodiment, the identification of the fuel 24 is preferably accomplished by using an optical sensor, an conductivity meter (or similar such electrical property sensor) , or other sensing device that is adapted to sense physical properties (i.e. density, viscosity, etc.) of the fuel 24. The fuel identification sensor 20 focuses on these fuel characteristics because the optical, electrical and physical properties of an aqueous fuel emulsion 25 differ from the optical, electrical and physical properties of conventional fuels 26 and the differences are such that one can readily distinguish an aqueous fuel emulsion 25 from a convention fuel 26, such as diesel fuel.

Finally, the fuel identification system 10 also includes an engine control unit 30 coupled with the fuel identification sensor 20. The engine control unit 30 is adapted to receive the fuel type signal 28 together with other engine parameters 90 and provide appropriate control of the engine 22 based on the type of fuel that is to be injected. As one can imagine, there are numerous differences in the control algorithms executed by the engine control system of an engine burning an aqueous fuel emulsion as compared to the control algorithms executed by the engine control system an engine burning a conventional fuel, such as diesel fuel.

As seen in FIG. 1, the fuel identification sensor 20 or device is located proximate to the fuel injectors 32 of the engine 22 so as to minimize or prevent discrepancies between what the fuel identification sensor 20 indicates is to be injected and what is actually injected. Since the engine timing is based, in part, on the output of the fuel identification sensor 20, it is most advantageous to coordinate, from a timing standpoint, the engine control unit outputs 36 with the timing lag between the fuel sensing and the fuel injection. In other words, the _. closer in proximity that the fuel identification sensor 20 is to the fuel injectors 32, the shorter the time lag between fuel sensing and fuel injection. The shorter time lag, in turn, minimizes timing errors and allows more precise control of the flex-fuel engine 22.

Turning now to FIGS. 2 and 3, there are shown schematic representations of various embodiments of a fuel identification sensor 20 which is utilized as part of the fuel identification and control system 10 of FIG. 1. As indicated above, the fuel identification sensor 20 is capable of distinguishing an aqueous fuel emulsion from a conventional fuel based on selected fuel characteristics, such as optical properties, electrical properties, or physical properties and produce a fuel type signal 28. The control unit 30 is adapted to receive the fuel type signal 28 and effectuate precise control of the engine based on the type of fuel identified.

In the embodiment illustrated in FIG. 2, the fuel identification sensor 20 consists of a optical probe or sensor 50 located near the fuel line 14 and in operative association with the fuel 24 flowing

therein. The optical sensor 50 is preferably used to determine the fuel type based on the optical characteristics of the fuel 24 in the fuel line 14. The optical characteristics, such as absorption at selected wavelengths, opacity, index of refraction, and other optical properties of an aqueous fuel emulsion often differ from the optical characteristics of diesel fuel. For example, a source of light passing through an aqueous fuel emulsion is either absorbed or reflected away whereas a diesel fuel is more transmissive in nature. In other words, many aqueous fuel emulsions do not allow light or other selected sources of radiation to simply pass through the fuel without significant absorption, reflection, or dispersion whereas diesel fuel readily transmits selected wavelengths of light with much lower levels of absorption, reflection and dispersion.

The illustrated optical sensor 50 includes a source of radiation or light 52 at a selected wavelength that is adapted to impinge a beam 54 on the fuel 24 transported within the fuel line 14 at a selected location 56. An optical receiver 58, such as a photodiode, charged couple device, or other conventional optical receiving device is disposed at a second location 60 within the fuel line 14 generally opposite the first location 56. Based on the intensity of the radiation or light received at the optical receiver 58, the type of fuel 24 being transported in the fuel line 14 can be ascertained. For example, because of the opacity of many aqueous fuel emulsions, little or no light originating from the source 52 at the first location 56 is received by the optical receiver 58 position at a second location 60 opposite thereto. For purposes of this

application, opacity is defined to be the capacity of a substance to obstruct, by absorption or reflection, the transmission of light or other forms of radiant energy. Conversely, where the fuel is a conventional diesel fuel, most of the light or radiation originating from the source 52 at the first location 56 is received by the optical receiver 58 positioned at the second location 60. The optical receiver 28 generates a signal 28 corresponding to the intensity of the light received by optical receiver 58 which is generally indicative of whether the fuel 24 is an aqueous fuel emulsion or not. In particular, the fuel identification signal 28 is forwarded to the engine control unit 30 which compares the received intensity against a predetermined optical threshold value associated with the aqueous fuel emulsion and stored in the engine control unit 30. If the intensity of the light received by the optical receiver 58 and embodied in the fuel identification signal 28 is less than the predetermined optical threshold value associated with the aqueous fuel emulsion, the fuel 24 in the fuel line 14 proximate the optical sensor 50 is an aqueous fuel emulsion and the engine control unit enables the aqueous fuel emulsion control algorithms. If, however, the intensity of the light received by the optical receiver 58 and embodied in the fuel identification signal 28 is equal to or greater than the predetermined optical threshold value, the fuel 24 in the fuel line 14 is other than the aqueous fuel emulsion and the engine control unit 30 enables the alternative engine control algorithms. For reasons related to the safe operation of a flex-fuel engine, it is advantageous to set the engine control algorithms associated with the aqueous fuel emulsions

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as the default control algorithms (except for the maximum fuel algorithms) within the engine control unit 30. The control algorithms for the maximum fuel strategy should default to the diesel engine strategy. An alternate form of the fuel identification sensor 20, as depicted in FIG. 3, uses a conductivity meter. As with the above-described embodiments, the fuel identification sensor 20 is capable of distinguishing an aqueous fuel emulsion from a conventional fuel based on selected fuel characteristics and produce a corresponding fuel type signal 28.. In this embodiment, the selected fuel characteristic is the electrical properties of the fuel because it has been realized that the electrical properties of aqueous fuel emulsions often differ from the electrical properties of diesel fuel . For example, the conductivity of an aqueous fuel emulsion is somewhat higher (i.e. the resistivity is lower) than that of conventional diesel fuel . The fuel identification sensor 20 illustrated in FIG. 3, includes a very low voltage source 82 oppositely coupled to a pair of leads 84 and 86 terminating in the fuel line 14 proximate to each other. The illustrated fuel identification sensor 20 also includes an ammeter 88 adapted to measure the electrical current passing through the circuit. The ammeter 88 generates a fuel identification signal 28 that is forwarded to a engine control unit 30. The engine control unit 30 illustrated in FIG. 3, is adapted to receive the fuel identification signal 28 from the ammeter 88 together with other related engine operating parameters 90 and provide the appropriate control of the engine 22 based on the type of fuel 24 detected in the fuel line 14.

More specifically, the engine control unit 30 compares the electrical current measured by the ammeter 88 against some empirically determined threshold value associated with the aqueous fuel emulsion and resident in read-only memory (ROM) of the engine control unit 30. If the electrical current measured by the ammeter 88 and embodied in the fuel identification signal 28 is equal to or above the threshold value associated with the aqueous fuel emulsion, the fuel 24 in the fuel line 14 proximate the leads 84 and 86 is deemed to be an aqueous fuel emulsion and the engine control unit enables the aqueous fuel emulsion control features. If, however, the electrical current measured by the ammeter 88 and embodied in the fuel identification signal 28 is less the threshold value associated with the aqueous fuel emulsion, the fuel 24 in the fuel line 14 proximate the leads 84 and 86 is deemed to a fuel other than the aqueous fuel emulsion and the engine control unit 30 enables the alternate control features.

Before describing the differences in the engine control algorithms between burning an aqueous fuel emulsion and a conventional fuel (e.g. diesel fuel) , it may be helpful to review some general background material relating to the use of aqueous fuel emulsions. One of the most promising benefits of aqueous fuel compositions is the small number of engine modifications required on select diesel engines in order to effectively use the fuel. Most of the modifications center around the fuel system.

Specifically, various modifications to the diesel engine should be considered to compensate for fuel compositions having a cetane quality lower than that of conventional diesel fuel. It is well known that

aqueous fuel emulsions typically reduce the cetane quality of the fuel to a point where combustion quality is marginal. To offset this problem, one such modification, disclosed herein, is to advance the fuel injection timing when utilizing the fuel in water emulsions. This is particularly necessary at light load conditions, engine starting conditions, and under engine warm-up conditions.

As indicated earlier, the aqueous fuel compositions can be used in internal combustion engines without significant modifications to the engine design. However, to .enhance fuel efficacy, several readily implemented changes are preferably incorporated into an engine structure. For example, the capacity of the engine fuel system must be increased to use the aqueous fuel compositions in diesel engines. The increased capacity of the engine fuel system is a function of the percent water contained in the fuel composition. In many cases, the engine fuel system capacity can be increased sufficiently by increasing the injector orifice size. Other engines may require an increase in the capacity of the injection pump or an increase in the capacity of the fuel transfer pump or both. Likewise, some engine modifica ions, such as the inclusion of a jacket water aftercooler may be required to warm the intake air under light load conditions. Similarly, the use of an engine block heater or inlet air heater may further be required to improve cold starting capability. Finally, as discussed more fully herein, the fuel injection timing, as implemented in the fuel system control algorithms, should preferably be adjusted (i.e.

advanced) to compensate for light loads conditions, cold starting conditions, etc.

Thus, the differences in the control algorithms that arise due to the different fuels (i.e. between burning aqueous fuel emulsions and conventional diesel fuel) in a flex-fuel engine are realized by the presently disclosed embodiment of the invention. For example, some of the important differences include: (1) the maximum fuel volume or quantity of the aqueous fuel emulsion injected is significantly greater than the fuel volume or quantity of diesel fuel; (2) the fuel injection timing is advanced at light loads when running on aqueous fuel emulsions as compared to conventional diesel fuel; (3) the fuel injection timing is advanced somewhat further by the various cold start algorithms when using aqueous fuel emulsions as compared to the timing advances implemented by the cold start algorithms for diesel fuel; (4) the control algorithms associated with the aqueous fuel emulsions are set as the default control algorithms in a flex-fuel engine; (5) a significant time delay should be imposed prior to changing between control algorithms (i.e. conventional fuel control algorithms to aqueous fuel control algorithms) when switching from diesel fuel control to aqueous fuel emulsions control to prevent over fueling; and (6) a relatively short time delay should be imposed prior to changing between control algorithms (i.e. aqueous fuel emulsion control algorithms to conventional fuel control algorithms) when switching from aqueous fuel emulsions control to diesel fuel control to likewise prevent over fueling.

Other forms of engine control strategies that differ for aqueous fuels compared to diesel fuels

may include the use of jacket water heater by-pass at light-load conditions only when using aqueous fuels to generally improve combustion. Also, it may be advisable to use varying strategies of hot exhaust gas recirculation at light load conditions when using aqueous fuels in an effort to improve combustion performance.

Turning now to FIG. 4, there is shown a block diagram broadly depicting the present method for the fuel identification and control in a flex-fuel engine adapted to use an aqueous fuel emulsion. The disclosed process includes the initial step of setting the default engine control algorithms. In the preferred embodiment, the default engine control algorithms are those engine control algorithms associated with the aqueous fuel emulsion. The next step involves detecting selected characteristics of the fuel in a fuel line of the flex-fuel engine proximate the fuel injectors using a fuel identification sensor, essentially as described above (block 102) . The detected fuel characteristics may be optical based fuel properties, electrical properties of the fuel, or even physical properties, such as density or viscosity of the fuel. Having detected selected characteristics of the transported fuel, the next step involves identifying the fuel in the fuel line as either an aqueous fuel emulsion or a conventional diesel fuel based on the detected fuel characteristics determined by the fuel identification sensor (block 104) . The step of identifying the fuel preferably includes identifying the fuel as an aqueous fuel emulsion if the detected characteristics correspond to some predetermined characteristics of permitted aqueous fuel emulsions. Otherwise the fuel

is identified as a conventional fuel if the detected characteristics do not correspond to the predetermined characteristics (block 106) . Where the fuel is identified as an aqueous fuel emulsion (YES branch of block 106) , the engine operation continues uninterrupted (block 108) using the default engine control algorithms. The control algorithms associated with the aqueous fuel emulsion include specialized fuel timing maps, engine torque maps, cold start algorithms, light load algorithms, fuel switching control algorithms, fuel metering algorithms, etc. However, if the identified fuel is not an aqueous fuel emulsion and therefore is a conventional fuel (NO branch of block 106) , then the engine control unit enables the alternate engine control algorithms (block 110) including fuel timing maps, engine torque maps, cold start algorithms, light load algorithms, fuel switching control algorithms, fuel metering algorithms, etc. The fuel identification process continues at a prescribed frequency so long as the engine is running and terminates once the engine is shut-off.

The above-identified method and system for the fuel identification and control of a flex-fuel engine can be utilized alone or in conjunction with other engine controlling techniques. Moreover, each of the specific steps involved in the preferred process, described herein, and each of the components in the preferred systems are easily modified or tailored to meet the peculiar design and operational requirements of the particular engine and the anticipated operating environment in which the engine is used.

For example, there are numerous other forms of suitable fuel identification sensors capable of detecting the differing physical properties, including such properties as viscosity or density, between an aqueous fuel emulsion and a conventional diesel fuel. Moreover, there are numerous measurement techniques adapted for sensing the physical, optical and electrical properties of fuels, all of which are contemplated for inclusion within the described system and methods.

From the foregoing, it should be appreciated that the present invention thus provides a method and system for the identification of the fuel within a fuel delivery system and subsequent control thereof. While the invention herein disclosed has been described by means of specific embodiments and processes associated therewith, numerous modifications and variations can be made thereto by those skilled in the art without departing from the scope of the invention or sacrificing all its material advantages.