Air-fuel-ratio dithering using a dual fuel path source

An apparatus for dithering fuel into an internal combustion engine includes a turbine that is powered by the internal combustion engine and a first fuel injector that injects a first fuel into an air stream to create a fuel/air stream. The apparatus also includes an air/fuel compressor that provides a compressed fuel/air stream to the internal combustion engine. The air/fuel compressor is powered by the turbine, and the air/fuel compressor compresses the fuel/air stream to create the compressed fuel/air stream. Additionally, the apparatus includes a second fuel injector that injects a second fuel into the compressed fuel/air stream prior to the compressed fuel/air stream entering the engine and after the compressed fuel/air stream exits the air/fuel compressor.

FIELD

This invention relates to fuel systems internal combustion engines and more particularly relates to air/fuel ratio dithering in a fuel system for an internal combustion engine.

BACKGROUND

For internal combustion engines, the engine often runs in an optimal condition at steady state. For example, when the engine is in a vehicle and the vehicle is traveling at a constant speed on a flat road. During the steady state condition, a multi-stage catalyst that receives exhaust from the engine and removes a portion of pollutants and particulate from the exhaust may perform at an optimum level or may operate within specified limits.

However, there are often conditions where the engine is in transient state, such as sudden acceleration or deceleration, encountering a hill, etc. During the transient conditions, the engine and/or catalyst may not run at optimally or may operate outside the specified limits. One reason for the decreased performance of the engine is a transport delay where an increase in fuel rate input into the engine is delayed by various components, such as a compressor and/or a charge air cooler.

SUMMARY

The subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the internal combustion engine system art associated with transient operating conditions that have not yet been fully solved by currently available systems. Accordingly, disclosed herein are apparatus, methods, and systems that overcome many of the shortcomings of the prior art.

According to one embodiment, an apparatus for dithering fuel into an internal combustion engine includes a turbine that is powered by the internal combustion engine and a first fuel injector that injects a first fuel into an air stream to create a fuel/air stream. The apparatus also includes an air/fuel compressor that provides a compressed fuel/air stream to the internal combustion engine. The air/fuel compressor is powered by the turbine, and the air/fuel compressor compresses the fuel/air stream to create the compressed fuel/air stream. Additionally, the apparatus includes a second fuel injector that injects a second fuel into the compressed fuel/air stream prior to the compressed fuel/air stream entering the engine and after the compressed fuel/air stream exits the air/fuel compressor.

In some implementations, the apparatus also includes a catalyst in exhaust receiving communication with the engine. The apparatus may also include a charge air cooler that cools the compressed fuel/air stream. The charge air cooler is positioned in the compressed fuel/air stream between the fuel/air compressor and the engine. The second fuel injector injects the second fuel into the compressed fuel/air stream after the compressed fuel/air stream leaves the charge air cooler.

According to some implementations of the apparatus, the second fuel injector injects a compressed second fuel into the compressed fuel/air stream. The apparatus can include a fuel compressor separate from the fuel/air compressor, where the fuel compressor is configured to compress the second fuel injected by the second fuel injector. The fuel compressor can be powered by a power source other than the turbine.

In certain implementations of the apparatus, the second fuel injector injects the second fuel into the compressed fuel/air stream only in response to a transient loading condition of the engine. The second fuel injector may, in some implementations, inject the second fuel into the compressed fuel/air stream during steady-state and transient loading conditions of the engine. In such latter implementations, the second fuel injector injects more of the second fuel into the compressed fuel/air stream during increased transient loading conditions on the engine, and injects less of the second fuel into the compressed fuel/air stream during decreased transient loading conditions of the engine.

According to some implementations of the apparatus, at least one of the first and second fuels is a gaseous fuel. The first and second fuels can be the same fuel. However, in certain implementations, the first and second fuels are different.

In another embodiment, an apparatus for dithering fuel into an internal combustion engine includes a turbine powered by exhaust from the internal combustion engine, a first fuel injector that injects a portion of fuel into an air stream to create a fuel/air stream, and an air/fuel compressor that provides a compressed fuel/air stream. The air/fuel compressor is powered by the turbine, and compresses the fuel/air stream to create the compressed fuel/air stream. The apparatus also includes a charge air cooler that cools the compressed fuel/air stream, where the charge air cooler receives the compressed fuel/air stream from the compressor and provides the compressed fuel/air stream to the engine. Further, the apparatus includes a fuel compressor that compresses another portion of the fuel to form a compressed fuel and a second fuel injector that injects the compressed fuel from the fuel compressor into the compressed fuel/air stream prior to the compressed fuel/air stream entering the engine and after the compressed fuel/air stream exits the charge air cooler.

According to some implementations of this embodiment, the fuel compressor is powered by a source other than the turbine. The apparatus may further include an alternator, where the fuel compressor is powered by the alternator. The second fuel injector can inject the compressed fuel into the compressed fuel/air stream in response to a transient loading condition on the engine. Additionally, the apparatus may include a fuel flow module that adjusts flow volume of the compressed fuel/air stream into the engine to adjust engine output, and a dithering module that adjusts an amount of fuel injected by the second fuel injector into the compressed fuel/air stream in response to a transient loading condition of the engine.

According to yet another embodiment, a method for dithering fuel into an internal combustion engine includes injecting fuel into an air stream to create a fuel/air stream, compressing the fuel/air stream to create a compressed fuel/air stream, combusting the compressed fuel/air stream, and dithering fuel into the compressed fuel/air stream before the fuel/air stream is combusted. In some implementations of the method, fuel is dithered into the compressed fuel/air stream only in response to a transient loading condition of the engine. According to yet some implementations of the method, dithering fuel into the compressed fuel/air stream includes adjusting the quantity of the dithered fuel in response to a transient loading condition of the engine.

DETAILED DESCRIPTION

FIG. 1is a schematic block diagram illustrating one embodiment of an apparatus100for dithering fuel in accordance with one embodiment of the present invention. The apparatus100includes an internal combustion engine102, a first fuel injector104, a fuel/air stream106, a fueUair compressor108, a compressed fuel/air stream110, a second fuel injector112, a dithering fuel stream114, exhaust gas piping116, a turbine118, and power120from the turbine118to the fuel/air compressor108, which are described below. Note that a “fuel injector,” as used herein may include a fuel metering device that may be a linear device, a time-based pulse-width modulated device, a crank synchronized device that is synchronized with a crank shaft position, or other device known to those in the art to inject fuel into an air stream or into an engine102.

The apparatus100includes an internal combustion engine102that provides power to a vehicle, a generator, a pump, or some other load appropriate for the engine102. The engine102, in one embodiment, is fed by a fuel that is in a gaseous state. For example, the fuel may be natural gas, autogas, biogas, etc. In another embodiment, the fuel is in a liquid state and then is converted to a gaseous state prior to use by the engine102. In one embodiment, the engine102includes a turbocharger that includes a turbine118that provides power120to a fuel/air compressor108. The apparatus100includes a first fuel injector104that injects the fuel into an air stream to create a fuel/air stream106, which is fed into the fuel/air compressor108.

The fuel/air compressor108compresses the fuel/air stream106to a suitable pressure for injection into the engine102. The fuel/air compressor108typically can be used to overcome low pressure issues associated with the fuel, such as, for example, where the fuel is low pressure pipeline natural gas or other condition where the fuel pressure is lower than an ideal pressure or a pressure within a specified range. In one embodiment, fuel and air are fed directly to the fuel/air compressor108and the fuel/air compressor108may include regulating functions of the first fuel injector104.

The fuel/air compressor108compresses the fuel/air stream106to create a compressed fuel/air stream110. The first fuel injector104and the fuel/air compressor108and possibly other components add time to a fuel cycle and typically increase transport delay. The transport delay may cause compressed fuel/air stream110to the engine102to be too lean or too rich under transient conditions of the engine102. For example, a vehicle powered by the engine102may encounter a hill and an operator may press a fuel pedal to increase fuel to the engine102. Transport delay caused by at least the first fuel injector104(e.g., it's distance away from the engine102) and the fuel/air compressor108may cause the compressed fueUair stream110to be at a lower level than required by the engine102based on the increased load of the hill so the engine102may run lean, which may affect performance of the engine102and downstream components, such as an exhaust catalyst.

The second fuel injector112injects fuel (i.e. a dithering fuel stream114) into the compressed fuel/air stream110prior to the compressed fuel/air stream110entering the engine102and after the compressed fuel/air stream110exits the fuel/air compressor108. By injecting the dithering fuel stream114into the compressed fuel/air stream110just ahead of the engine102, the second fuel injector112typically is able to react quicker to a transient condition than the transport delay, thus allowing the engine102to operate in more efficient conditions (e.g., by more responsively receiving a fuel/air stream with a more accurate or desirable air-to-fuel ratio) than an engine without the second fuel injector112. The fuel injected by the second fuel injector112can be the same fuel as or a different fuel than the fuel injected by the first fuel injector104. One or both of the fuels injected by the first and second fuel injectors can be a gaseous fuel.

A turbine118is powered by the engine102, typically by exhaust from the engine102. The turbine118, in one embodiment, provides power120to run the fuel/air compressor108in a typical turbocharger application. In one embodiment, the turbine118is connected to the fuel/air compressor108through a shaft and the shaft provides power120to run the fuel/air compressor108. In another embodiment, the turbine118generates electrical power120that runs the fuel/air compressor108. In another embodiment, the turbine118provides power to one or more additional devices. Exhaust from the engine102travels through exhaust gas piping116to the turbine118and from the turbine118to additional exhaust gas piping116and eventually may be expelled to the atmosphere. While the turbine118provides power120to the fuel/air compressor108, another power source may provide power to the second fuel injector112, such as power from an alternator. In one embodiment, by powering the second fuel injector112separately from the fuel/air compressor108and other components that contribute to the transport delay, the second fuel injector112may react quicker than the transport delay caused by the fuel/air compressor108, the first fuel injector104, etc. to increase or decrease the dithering fuel stream114.

In one embodiment, the second fuel injector112does not inject fuel during steady-state conditions and reacts to transient conditions by injecting fuel. In another embodiment, the second fuel injector112does not inject fuel during steady-state conditions as well as small transient conditions and reacts only to larger transient conditions by injecting fuel. In another embodiment, the second fuel injector112injects some amount of fuel during steady-state conditions and reacts to larger transient conditions by increasing the amount of injected fuel, possibly for an increased loading condition, or by decreasing the amount of injected fuel, possibly for a decreased loading condition. One of skill in the art will recognize other ways to change the amount of fuel injected by the second fuel injector112.

FIG. 2is a schematic block diagram illustrating another embodiment of an apparatus200for dithering fuel in accordance with one embodiment of the present invention. The apparatus200includes an internal combustion engine102, a first fuel injector104, a fuel/air stream106, a fuel/air compressor108, a compressed fuel/air stream110, a second fuel injector112, a dithering fuel stream114, exhaust gas piping116, a turbine118, and power120from the turbine118to the fuel/air compressor108, which are substantially similar to those described above in relation to the apparatus100ofFIG. 1. The apparatus200, in various embodiments, includes a charge air cooler202, a fuel compressor204, a compressed fuel stream206, a catalyst208, a tail pipe210, an alternator212, a drive train214, and a controller220with a fuel flow module222and a dithering module224, which are describe below.

In one embodiment, the apparatus200includes a charge air cooler202that cools the compressed fuel/air stream110. When a gas is compressed, typically temperature of the gas increases. The charge air cooler202cools the compressed fuel/air stream110coming out of the fuel/air compressor108. Cooling the compressed fuel/air stream110before the compressed fuel/air stream110reaches the engine102may increase efficiency of the engine102. The charge air cooler202is typically positioned in the compressed fuel/air stream110between the fuel/air compressor108and the engine102. In one embodiment, the second fuel injector112injects the fuel into the compressed fuel/air stream110after the compressed fuel/air stream110leaves the charge air cooler202. In another embodiment, the second fuel injector112injects the fuel into the compressed fuel/air stream110before the charge air cooler202to cool the compressed fuel/air stream110and the dithering fuel stream114. However, injecting the dithering fuel stream114before the charge air cooler202may increase transport delays of the dithering fuel stream114.

The apparatus200, in another embodiment, includes a fuel compressor204that compresses fuel to create a compressed fuel stream206that is input to the second fuel injector112. The dithering fuel stream114from the second fuel injector112is combined with the compressed fuel/air stream110before entering the engine102. In one embodiment, the fuel compressor204increases pressure of the fuel to a pressure comparable with the compressed fuel/air stream110. The fuel compressor204may compensate for low fuel pressure of a fuel system, as described above. In other embodiments, the fuel compressor204increases pressure of the fuel to a pressure above or below the compressed fuel/air stream110.

In one embodiment, the fuel compressor204and the second fuel injector112have an order that is switched from the order shown inFIG. 2. In another embodiment, the fuel compressor204and/or the second fuel injector112are powered from a source different than the turbine118. For example, the apparatus200may include an alternator212and/or a battery (not shown) that provides power to the fuel compressor204and/or the second fuel injector112. Having a power source separate from the turbine118may allow a quicker response to reduce transport delay. In addition, the fuel compressor204and/or the second fuel injector112may be sized or designed to operate more quickly than components that cause fuel transport delay.

In one embodiment, the apparatus200includes a catalyst208that processes the exhaust gasses from the engine102and expels the processed exhaust through a tail pipe210. In one example, the catalyst208is an advanced three-way catalyst, which is known in the art. The advanced three-way catalyst may be for natural gas systems or for other fuels appropriate for the apparatus200. In another embodiment, the apparatus200includes a catalyst208with fewer stages than an advanced three-way catalyst or a catalyst with a different number of stages but of a different design. In one embodiment, adding the dithering fuel stream114to the compressed fuel/air stream110allows a wider range of operation while operating within specified ranges, such as ranges required by the United States Environmental Protection Agency (“EPA”).

In one embodiment, the apparatus200includes a drive train214powered by the engine102. For example, the apparatus200may be part of a vehicle with a drive train214. In other embodiments, the apparatus200includes gears, belts, etc. which are connected to the engine102and that drive equipment. In another embodiment, the engine102connects to a generator.

In one embodiment, the apparatus200includes a controller220with a fuel flow module222and a dithering module224. The controller220may control operation of the engine102along with other systems associated with the engine102. The controller220may be a single component or may have functions divided into multiple components that may be in multiple locations. In one embodiment the fuel flow module222adjusts flow volume of the compressed fuel/air stream110into the engine102to adjust engine output. For example, the fuel flow module222may be responsive to a floor pedal in a vehicle or a lever or other mechanism on a generator or other device. The fuel flow module222may be used to increase or decrease engine speed and/or power. In another embodiment, the dithering module224adjusts an amount of fuel injected by the second fuel injector112into the compressed fuel/air stream110in response to a transient loading condition for the engine102. The dithering module224may include an ability to determine a transient condition for the engine102and may increase or decrease fuel injected by the second fuel injector112. The dithering module224may use measurements from various engine parts, from the catalyst208, etc. to determine an amount of increase or decrease for the fuel injected by the second fuel injector112.

FIG. 3is a schematic flow chart diagram illustrating one embodiment of a method300for dithering fuel in accordance with one embodiment of the present invention. The method300begins and the first fuel injector104injects302fuel into an air stream of an internal combustion engine102to create a fuel/air stream106. The fuel/air compressor108compresses304the fuel/air stream106to create a compressed fuel/air stream110. The second fuel injector112injects306the dithering fuel stream114into the compressed fuel/air stream110. The dithering module224determines308if there is a transient condition for the engine102. If the dithering module224determines308that there is a transient condition for the engine102, the second fuel injector112adjusts310the dithering fuel stream114into the compressed fuel/air stream110and the method300inputs312the compressed fuel/air stream110, along with the dithering fuel stream114to the engine102, and the method300returns and the first fuel injector104injects302fuel into the air stream. If the dithering module224determines308that there is not a transient condition for the engine102, the method300inputs312the compressed fuel/air stream110without changing the dithering fuel stream114and the method300returns and the first fuel injector104injects302fuel into the air stream.

The computer readable medium may also be a computer readable signal medium. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electrical, electro-magnetic, magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport computer readable program code for use by or in connection with an instruction execution system, apparatus, or device. Computer readable program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, Radio Frequency (RF), or the like, or any suitable combination of the foregoing