GASOLINE DITHERING FOR SPARK-IGNITED GASEOUS FUEL INTERNAL COMBUSTION ENGINE

Abstract

An internal combustion engine system of the present application includes a spark-ignited internal combustion engine that is powered by a gaseous fuel. The engine system also includes an exhaust system that is in exhaust gas receiving communication with the internal combustion engine. The exhaust system includes an exhaust treatment component. Additionally, the exhaust system includes a liquid fuel injection system in liquid fuel injecting communication with the exhaust system to inject liquid fuel into exhaust gas upstream of the exhaust treatment component.

Description

FIELD

This disclosure relates to spark-ignited gaseous fuel internal combustion engines, and more particularly to an exhaust system that dithers an liquid fuel for such internal combustion engines.

BACKGROUND

Emissions regulations for internal combustion engines have become more stringent over recent years. Environmental concerns have motivated the implementation of stricter emission requirements for internal combustion engines throughout much of the world. Governmental agencies, such as the Environmental Protection Agency (EPA) in the United States, carefully monitor the emission quality of engines and set acceptable emission standards, to which all engines must comply. Generally, emission requirements vary according to engine type. Emission tests for spark-ignited gasoline (e.g., aqueous or non-gaseous fuel) engines typically monitor the release of carbon monoxide, nitrogen oxides (NOx), and unburned hydrocarbons (UHC). Catalytic converters (e.g., oxidation catalysts) implemented in an exhaust gas aftertreatment system have been used to eliminate many of the regulated pollutants present in exhaust gas generated from gasoline powered engines. For example, some known three-way catalysts include carefully selected catalytic material formulations to specifically oxidize carbon monoxide and unburned hydrocarbons, and reduce nitrogen oxides to less harmful components, present in the exhaust gas. Conventional three-way catalysts are designed to oxidize or reduce such pollutants more efficiently for engines running above the stoichiometric air-to-fuel ratio (i.e., rich conditions).

Recently, due at least in part to high crude oil prices, environmental concerns, and future fuel availability, many internal combustion engine designers have looked to at least partially replace crude oil fossil fuels, e.g., gasoline and diesel, with so-called alternative fuels for powering internal combustions engines. Desirably, by replacing or reducing the use of fossil fuels with alternative fuels, the cost of fueling internal combustion engines is decreased, harmful environmental pollutants are decreased, and/or the future availability of fuels is increased. Known alternative fuels include gaseous fuels or fuels with gaseous hydrocarbons, such as, for example, natural gas, petroleum gas (propane), and hydrogen. The combustion byproducts present in exhaust gas generated by spark-ignited gaseous-powered engines are similar to those present in exhaust gas generated by spark-ignited non-gaseous-powered engines. Accordingly, conventional gaseous-powered engine systems utilize the same or similar oxidation catalysts found in non-gaseous-powered engine systems to oxidize the regulated pollutants generated by gaseous-powered engines.

Traditionally, gaseous-powered engines are operated at rich air-to-fuel ratios (e.g., richer than stoichiometric) in order to reduce oxygen concentrations within the exhaust gas, and thus the formation of carbon monoxide and nitrogen oxides. However, lower oxygen concentrations in the exhaust gas may fail to adequately replenish oxidation catalysts configured to store oxygen for NOx reduction purposes.

Additionally, operating a gaseous-powered engine under stoichiometric or richer air-to-fuel ratios results in a relatively low brake thermal efficiency of the engine. Operating at such air-to-fuel ratios causes high combustion temperatures, which result in high component temperatures in the engine, and the necessity to reduce output power to avoid component failure. However, in view of the premium placed on satisfying exhaust emissions regulations, conventional gaseous-powered engines are designed to meet exhaust emissions regulations at the expense of thermal efficiency and power density.

Finally, many internal combustion engine systems experience long delays between a cold start of the engine and the exhaust gas reaching temperatures necessary for efficient reduction of NOx in the exhaust gas.

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 art that have not yet been fully solved by currently available exhaust systems for gaseous-powered internal combustion engines. Accordingly, the subject matter of the present application has been developed to provide an exhaust system for a gaseous-powered engine that overcomes at least some shortcomings of prior art systems. For example, in some embodiments described herein, an exhaust system for a gaseous-powered engine dithers an aqueous or liquid fuel, such as gasoline, into the exhaust system for NOx reduction purposes to allow the engine to run leaner (e.g., with a higher air-to-fuel ratio, such as greater than 1.0) compared to conventional systems, which results in an increase in the thermal efficiency and power density of the engine. Additionally, in certain embodiments described herein, the dithering of liquid fuel into the exhaust system promotes a faster increase in exhaust gas temperature after a cold start than conventional systems.

According to some embodiments, an internal combustion engine system of the present application includes a spark-ignited internal combustion engine that is powered by a gaseous fuel. The engine system also includes an exhaust system that is in exhaust gas receiving communication with the internal combustion engine. The exhaust system includes an exhaust treatment component. Additionally, the exhaust system includes a liquid fuel injection system in liquid fuel injecting communication with the exhaust system to inject liquid fuel into exhaust gas upstream of the exhaust treatment component.

In certain implementations of the internal combustion engine system, the gaseous fuel is natural gas. In yet some implementations, the liquid fuel is gasoline.

According to some implementations of the internal combustion engine system, the liquid fuel injection system injects liquid fuel into the exhaust gas based on an air-to-fuel ratio of the exhaust gas generated by the spark-ignited internal combustion engine. The spark-ignited internal combustion engine may generate exhaust gas with an air-to-fuel ratio above 1.0.

In some implementations, the exhaust treatment component stores oxygen, and the liquid fuel injection system injects liquid fuel into the exhaust gas based on an oxygen storage capacity of the exhaust treatment component. Alternatively, or additionally, the liquid fuel injection system injects liquid fuel into the exhaust gas during a cold start of the spark-ignited internal combustion engine.

The exhaust system of the internal combustion engine, in some implementations, includes an exhaust manifold that is coupled to the spark-ignited internal combustion engine. The liquid fuel injection system can inject the liquid fuel into the exhaust manifold.

According to certain implementations, the engine system also includes a gaseous fuel injection system that is in gaseous fuel injecting communication with the spark-ignited internal combustion engine. The liquid fuel injection system can be configured to inject liquid fuel into the exhaust gas independently of the injection of gaseous fuel injected into the engine by the gaseous fuel injection system. The quantity and timing of the injection of liquid fuel into the exhaust gas by the liquid fuel injection system may be based solely on conditions of the internal combustion engine system downstream of the spark-ignited internal combustion engine.

The exhaust treatment component is an oxidation catalyst in some implementations, a three-way catalyst in some implementations, and a nitrogen oxide reduction catalyst in yet some implementations. The liquid fuel injection system is a retrofitted diesel exhaust fluid injection system in some certain implementations. The gaseous fuel can be substantially solely natural gas.

According to another embodiment, an electronic control module for a spark-ignited internal combustion engine powered by a gaseous fuel includes an exhaust system condition module that determines a condition of an exhaust system in exhaust gas receiving communication with the spark-ignited internal combustion engine. The electronic control module can also include a liquid fuel control module that commands the dithering of a liquid fuel into the exhaust system based on the condition of the exhaust system.

In some implementations of the electronic control modules, the exhaust system includes an oxidation catalyst, and the condition of the exhaust system includes an oxygen storage capacity of the oxidation catalyst. The condition of the exhaust system can be an air-to-fuel ratio of exhaust gas generated by the spark-ignited internal combustion engine in certain implementations. The condition of the exhaust system can be an exhaust gas temperature below a minimum threshold in yet some implementations.

According to yet another embodiment, a method for dithering a liquid fuel into an exhaust system in exhaust receiving communication with a spark-ignited internal combustion engine powered by a gaseous fuel is disclosed. The method includes determining a condition of the exhaust system, and injecting a liquid fuel into exhaust gas flowing through the exhaust system based on the condition of the exhaust system.

The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more embodiments and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of embodiments of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular embodiment or implementation. In other instances, additional features and advantages may be recognized in certain embodiments and/or implementations that may not be present in all embodiments or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which:

FIG. 1 is a schematic diagram of an internal combustion engine system having an exhaust system that dithers a liquid fuel according to one embodiment;

FIG. 2 is a schematic diagram of an electronic control module of an internal combustion engine system;

FIG. 3 is a schematic diagram of an internal combustion engine system having an exhaust system with a three-way catalyst and a gasoline injector that dithers gasoline into the exhaust system according to another embodiment; and

FIG. 4 is a schematic flow chart diagram of a method for retrofitting an existing exhaust system if necessary and dithering a liquid fuel into the exhaust system according to one embodiment.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the subject matter of the present disclosure. Appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. Similarly, the use of the term “implementation” means an implementation having a particular feature, structure, or characteristic described in connection with one or more embodiments of the subject matter of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more embodiments.

According to one general embodiment of an internal combustion engine system 100 shown in FIG. 1, the system includes an internal combustion engine 110 coupled to an exhaust system 120. The engine 110 is a spark-ignited engine fueled by gaseous hydrocarbons or fuel 140, such as natural gas, petroleum gas (propane), and hydrogen. As defined herein, gaseous fuels, as opposed to non-gaseous liquid or aqueous fuels (e.g., gasoline and diesel), are those that are introduced and managed within the engine in a gaseous state, as opposed to, a liquid state. In specific implementations, the engine 110 is a spark-ignited engine fueled by natural gas. Spark-ignited gaseous fuel engines are configured and calibrated differently than spark-ignited non-gaseous fuel engines. Gaseous fuel engines introduce considerations not present with non-gaseous engines. For example, non-gaseous engines do not produce significant amounts of certain combustion byproducts produced by gaseous engines. Of particular relevance to the illustrated embodiments of the system 100 of the present disclosure, non-gaseous fuel engines produce no more than nominal amounts of methane compared to gaseous fuel engines, which produce large amounts of methane when the gaseous fuel itself contains a large amount of methane, which is normal with natural gas and a wide variety of other gaseous fuels.

The internal combustion engine system 100 also includes an air intake system that receives and directs air into the engine 110. Accordingly, the air intake system includes an air inlet that is at essentially atmospheric pressure, thus enabling fresh air to enter the air system. In one embodiment, prior to the fresh air entering the engine 110, it receives a metered amount of gaseous fuel 140. The quantity and timing of the gaseous fuel 140 added to the air is controlled by an electronic control module 130 based on any of various operating conditions of the engine 100, such as engine speed, torque demand, air temperature and pressure, exhaust temperature and pressure, and the like. The gaseous fuel 140 can be stored in a storage tank and injected into the fresh air via a fuel injector and fuel pump specifically configured to dose a gaseous material. Although not shown, the fresh air may also be mixed with recirculated exhaust gas from an exhaust gas recirculation (EGR) line. The fuel and air mixture may enter a compressor of a turbocharger before entering the engine. Alternatively, the gaseous fuel 140 can be added to the air after the compressor. For example, in one implementation, the gaseous fuel 140 is directly injected into the combustion chambers of the engine via a common rail and a plurality of fuel injectors. Whether the fuel is injected directly into the combustion chambers or injected into the air upstream of the engine, the combined fuel and air mixture is ignited, and the fuel is combusted, via a spark-ignition system to generate a pressure differential within the chambers for powering the engine.

Combustion of the gaseous fuel in the engine 110 produces exhaust gas that is operatively vented to the exhaust system 120 after driving a turbine of a turbocharger in some implementations. Generally, the exhaust system 120 treats, regulates, and directs the exhaust gas received from the engine. The exhaust system 120 can include one or more exhaust treatment components, such as, for example, three-way catalysts, oxidation catalysts, filters, adsorbers, and the like, for treating (i.e., removing pollutants from) the exhaust gas. Additionally, the exhaust system 120 can include exhaust flow regulation devices to regulate the exhaust gas flow rate and pressure (e.g., backpressure) of exhaust gas flowing into, through, and out of the system 120. Also, the exhaust system 120 can include actuators and valves to direct exhaust gas to one or more destinations. For example, the exhaust system 120 can include an EGR valve that is actuatable to direct (e.g., vent) a portion of the received exhaust gas into the atmosphere as expelled exhaust and direct a portion of the received exhaust gas into one or more EGR lines for recirculation back into the combustion chambers.

The internal combustion engine system 100 also includes a sub-system for dithering liquid fuel 150 into the exhaust gas generated by the engine 110 before the exhaust gas passes through the exhaust system 120. Although not shown, the liquid fuel 150 can stored in a storage tank and injected into the exhaust gas via a fuel injector and fuel pump specifically configured to dose a liquid material. Generally, liquid material injectors and pumps are able to more precisely, accurately, and responsively administer doses of liquid material than gaseous material injectors and pumps. Moreover, liquid fuels, such as gasoline, have a lower light-off temperature than gaseous fuels, such as natural gas. Accordingly, the liquid fuel added to the exhaust gas lowers the temperature at which the oxidation of the exhaust gas occurs, which leads to improved thermal management of the exhaust system.

As shown in FIG. 1, in certain embodiments, the liquid fuel 150 is injected into the exhaust gas upstream of the exhaust system 120. In other words, in certain embodiments, the liquid fuel 150 is configured to be injected into the exhaust gas upstream of the exhaust treatment components of the exhaust system 120. The liquid fuel 150 can be injected into the exhaust gas upstream of all exhaust treatment components, or downstream of some components and upstream of others. Generally, the liquid fuel 150 is injected upstream of the component or components that utilize excess hydrocarbons in the exhaust gas to effectuate desired results. For example, the excess hydrocarbons generated by the injected liquid fuel 150 can be utilized by an oxidation catalyst to increase exhaust gas temperature or a three-way catalyst to increase the NOx reduction efficiency of the exhaust system 120.

The quantity and timing of the liquid fuel 150 dithered into the exhaust gas is controlled by the electronic control module 130 based on any of various operating conditions of the engine 100, such as exhaust flow rate, exhaust temperature and pressure, exhaust air-to-fuel ratio, exhaust system operating conditions (e.g., NOx conversion capacity, oxygen storage capacity, and age of the system), and the like. In some implementations, the electronic control module 130 controls the injection of the gaseous fuel 140 into the engine independently of the injection of the liquid fuel 150 into the exhaust system 120. In other words, the quantity and timing of the injection of liquid fuel 150 is not dependent on the quantity and timing of the injection of the gaseous fuel 140. Generally, the electronic control module 130 communicates with and/or receives communication from various components of the system 100 via electronic signals (as indicated by dashed lines). The electronic control module 130 controls the operation of the engine system 100 and associated sub-systems, such as the engine 110 and exhaust system 120. The electronic control module 130 is depicted in FIG. 1 as a single physical unit, but can include two or more physically separated units or components in some embodiments if desired. In certain embodiments, the electronic control module 130 receives multiple inputs, processes the inputs, and transmits multiple outputs. The multiple inputs may include sensed and/or calculated measurements from the sensors and various user inputs. The inputs are processed by the electronic control module 130 using various algorithms, stored data, and other inputs to update the stored data and/or generate output values. The generated output values and/or commands are transmitted to other components of the controller and/or to one or more elements of the engine system 10 to control the system to achieve desired results.

According to a specific embodiment, and referring to FIG. 2, the electronic control module 130 includes an exhaust system condition module 160 and a liquid fuel control module 164. Generally, the exhaust system condition module 160 and liquid fuel control module 164 cooperate to generate a liquid fuel dosing command 168 based on sensor inputs 166. The sensor inputs 166 may include measured or calculated conditions of the engine system 100 as discussed above. For example, in one implementation, the sensor inputs 166 include at least one of an air-to-fuel ratio input, a catalyst oxygen storage input, an exhaust temperature input, and an engine ON input. In some implementations, the sensor inputs 166 indicate only conditions of the engine system downstream of the engine 110 (e.g., solely based on conditions of the exhaust system 120). Based on the sensor inputs 166, the exhaust system condition module 160 determines an exhaust system condition 162 of the exhaust system 120. Generally, the exhaust system condition 162 represents a condition of the exhaust system affected by the presence of unburned hydrocarbons in the exhaust gas. In one implementation, the exhaust system condition 162 can be the exhaust gas temperature and/or the NOx reduction efficiency of the exhaust system 120. Based on the exhaust system condition 162, the liquid fuel control module 164 determines the quantity of liquid fuel necessary to achieve a desired result, and issues the liquid fuel dosing command 168, which commands the engine system 100 to inject the determined quantity of liquid fuel into the exhaust gas at an appropriate time to realize the desired result.

In one implementation, the input includes one of an engine ON input indicating the initiation of a cold start of the engine 110 and the exhaust system condition 162 is the exhaust gas temperature. Alternatively, the input includes a measurement from an exhaust temperature sensor. The liquid fuel control module 164 compares the exhaust gas temperature received from the exhaust system condition module 160 to a corresponding predetermined threshold. If the exhaust gas temperature is below the threshold, the liquid fuel control module 164 determines a quantity of liquid fuel necessary to reach the exhaust gas temperature threshold, and issues a liquid fuel dosing command 168 corresponding with the determined quantity.

In another implementation, the input includes an air-to-fuel ratio input and a catalyst oxygen storage input, and the exhaust system condition 162 is the NOx reduction efficiency or performance of the exhaust system 120. The air-to-fuel ratio input can be determined based on an estimation of the amount of oxygen and fuel in the exhaust gas based on known operating conditions of the engine. The catalyst oxygen storage input indicates the quantity of oxygen stored on an catalyst (e.g., three-way catalyst) of the exhaust system 120, or the capacity of the catalyst to store oxygen. The liquid fuel control module 164 compares the NOx reduction efficiency of the exhaust system 120 received from the exhaust system condition module 160 to a corresponding predetermined threshold. If the NOx reduction efficiency is below the threshold, the liquid fuel control module 164 determines a quantity of liquid fuel necessary to reach the NOx reduction efficiency threshold, and issues a liquid fuel dosing command 168 corresponding with the determined quantity.

Referring to FIG. 3, a specific embodiment of an internal combustion engine system 200 is shown. The engine system 200 is similar to the engine system 100 of FIG. 1, with like numbers and titles referring to like features. Accordingly, unless otherwise indicated, the description of the features of the engine system 100 applies equally to the corresponding features of the engine system 200. Like the engine system 100, the engine system 200 includes a gaseous fuel internal combustion engine 210 and an electronic control module 230. The engine 210 is a spark-ignited engine fueled by natural gas supplied from a natural gas tank 240. The natural gas from the tank 240 is supplied to the engine 210 via a natural gas injector 242 that is controlled by the electronic control module 130. The natural gas is injected into the air before or after the air enters the engine 210. The combusted natural gas produces exhaust gas that is received by an exhaust manifold 212 in exhaust receiving communication with the engine 210. The engine 210 is in exhaust providing communication with an exhaust system that includes a three-way catalyst 220.

The three-way catalyst 220 can be a flow-through type catalyst having a catalyst bed exposed to the exhaust gas flowing through a main exhaust line of the exhaust system and past the bed. The catalyst bed includes a catalytic layer disposed on a washcoat or carrier layer. The carrier layer can include any of various materials (e.g., oxides) capable of suspending the catalytic layer therein. The catalyst layer is made from one or more catalytic materials selected to react with (e.g., oxidize) one or more pollutants in the exhaust gas. The catalytic materials of the three-way catalyst 220 can include any of various materials, such as precious metals platinum, palladium, and rhodium, as well as other materials, such as transition metals cerium, iron, manganese, and nickel. Further, the catalyst materials can have any of various ratios relative to each other for oxidizing and reducing relative amounts and types of pollutants as desired.

Generally, the three-way catalyst 220 is so termed because it contains catalytic materials specifically selected to react with and oxidize or reduce three specific pollutants. The three specific pollutants include carbon monoxide (CO), unburned hydrocarbons (UHC), and nitrogen oxides (NOx). In some implementations, the three-way catalyst 220 is housed within the same housing, and the catalyst includes three catalyst beds positioned adjacent each other to form three separate catalyst stages. Although the three-way catalyst 220 is depicted as a single unit in FIG. 3, in some embodiments, the three-way catalyst can be formed of two or more separate, disparate units. For example, in one embodiment, the three-way catalyst 220 is housed within a single housing, while in another embodiment, the three-way catalyst 220 includes three separate catalysts (e.g., a CO oxidation catalyst, a methane oxidation catalyst, and a NOx reduction catalyst) each housed within a separate housing. In one embodiment, the NOx catalyst of the three-way catalyst 220 is a NOx adsorber catalyst. In another embodiment, the NOx catalyst of the three-way catalyst 220 is a selective catalytic reduction (SCR) catalyst that forms part of a SCR system. Although not shown, the main exhaust line of the exhaust system may include other exhaust treatment devices, such as filters, that further treat the exhaust gas before it vents into the atmosphere.

Like the engine system 100, the engine system 200 includes a sub-system for dithering gasoline into the exhaust gas generated by the engine 210 before the exhaust gas enters the three-way catalyst 220. The gasoline is stored in a gasoline tank 250 and injected into the exhaust gas via a gasoline injector 252, which can receive gasoline from the tank via a fuel pump 254 operatively coupled with the engine 210. In the illustrated embodiment of FIG. 3, the gasoline injector 252 is positioned such that gasoline is injected into the exhaust gas located within the exhaust manifold 212. Alternatively, the gasoline injector 252 can be positioned downstream of the exhaust manifold 212 to inject gasoline into the exhaust gas downstream of the exhaust manifold. The quantity and timing of the gasoline dithered into the exhaust gas is controlled by an electronic control module 230 Like the electronic control module 130, the electronic control module 230 is configured to dither gasoline directly into the exhaust gas on an as-needed basis to promote exhaust gas conditions conducive to achieving desired exhaust system performance.

According to certain implementations associated with an existing internal combustion engine that has an exhaust system equipped with a diesel exhaust fluid (DEF) injection system, the components of the DEF injection system can be utilized to inject gasoline (or other liquid fuel) instead of DEF. As mentioned above, certain internal combustion engine systems have an exhaust aftertreatment system with a selective catalytic reduction (SCR) system configured to reduce NOx on an SCR catalyst in the presence of ammonia. The ammonia is introduced into the exhaust gas stream in the form of an aqueous reductant, such as urea, that decomposes into ammonia after being injected into an exhaust gas stream. The aqueous reductant is stored in a reductant storage tank. In some implementations, each internal combustion engine system 100, 200 can be an internal combustion engine system with a DEF injection system that has been retrofitted to inject a liquid fuel instead of DEF. For example, the DEF injection system can be evacuated of DEF by, among other things, emptying DEF from the DEF storage tank. Then, the DEF storage tank can be filled with aqueous fuel. Because DEF is in a liquid or aqueous state, the components of the DEF injection system (e.g., storage tank, pump, injector, delivery lines, etc.) are conducive to handling liquid or aqueous fuel. Accordingly, a DEF injection system can be easily retrofitted to handle and inject a liquid fuel without substantial modifications, if any, to the structural components of the DEF injection system. In certain implementations, the DEF injection control system, including injection algorithms and mapping, is replaced with a liquid fuel injection control system as part of the retrofit.

The exhaust system may include an oxygen storage capacity (OSC) sensor 222 and an air-to-fuel ratio sensor 224 configured to calculate and detect, respectively, the OSC of the three-way catalyst 220 and the air-to-fuel ratio of exhaust gas entering the three-way catalyst. The OSC sensor 222 can be a virtual sensor that estimates the OSC of the three-way catalyst 220 based on various sensed and/or estimated inputs. In one implementation, the OSC of the three-way catalyst 220 is determined based on a difference between the air-to-fuel ratio of the exhaust gas upstream and downstream of the three-way catalyst. The determination of the OSC by the OSC sensor 22 can be further based on the application of the air-to-fuel ratio difference to a three-way catalyst model 228 that models the behavior of the three-way catalyst 220. The air-to-fuel ratio of exhaust gas downstream of the three-way catalyst can be determined by an air-to-fuel sensor 226. The air-to-fuel sensors 224, 226 can be a physical sensor that detects the air-to-fuel ratio of the exhaust gas. The OSC sensor 222 and air-to-fuel ratio sensor 224 are in electronic communication with the electronic control module 230 to supply the electronic control module with the calculated and detected OSC of the three-way catalyst 220 and the air-to-fuel ratio of the exhaust gas. The exhaust system condition module of the electronic control module 230 utilizes the OSC and air-to-fuel ratio inputs from the sensors 222, 224 to determine an exhaust system condition as described above. The electronic control module 230 also has a gasoline control module that utilizes the exhaust system condition to generate a gasoline dosing command that commands actuation of the gasoline injector 252 to inject a desired amount of gasoline into the exhaust gas.

Referring to FIG. 4, according to one embodiment, a method 300 for dithering liquid fuel into an exhaust system of an internal combustion engine system is shown. In certain implementations, each of the electronic control modules 130, 230 may be configured to execute the steps of the method 300. The method 310 starts by determining whether an existing DEF injection system is being retrofitted for liquid fuel injection at 310. If the determination at 310 is answered affirmatively, then the method 300 replaces the DEF in the DEF injection system with a liquid fuel, such as gasoline, at 320. Should an internal combustion engine system be equipped with a liquid fuel injection system such that the determination at 320 is answered in the negative, or after replacing DEF in an existing DEF injection system with liquid fuel at 320, the method 300 proceeds to determine one or more operating conditions of the exhaust system, as well as in some implementations one or more operating conditions of the engine, at 330. The operating conditions of the exhaust system may include the air-to-fuel ratio of the exhaust and/or the OSC of an oxidation catalyst. The operating conditions of the engine may include engine speed and cold-start conditions. Based on the operating conditions of the exhaust system, and engine system in some implementations, the method 300 dithers the liquid fuel into the exhaust system (e.g., the exhaust gas upstream of exhaust treatment components of the exhaust system) at 340. Generally, the method 300 dithers liquid fuel into the exhaust system at 340 to facilitate more efficient reduction of NOx in the exhaust gas and/or improve thermal management of the exhaust gas.

Although mentioned above, the liquid fuel dithering systems, apparatus, and methods provides one or more advantages over conventional systems. For example, in some implementations, the liquid fuel dithering systems, apparatus, and methods of the present disclosure may provide one or more of the following advantages additional advantages: (1) fewer constraints on engine performance and tuning as liquid fuel is dithered downstream of engine; (2) smaller oxidation catalysts as less oxygen is required to be stored when engine is running leaner; (3) lower oxidation catalyst cost because fewer precious metals or catalytic materials are required; (4) reduction in methane emissions; and (5) improved response under transient operating conditions of the engine.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method, and/or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module,” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having program code embodied thereon.

Many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by various types of processors. An identified module of program code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

Indeed, a module of program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. Where a module or portions of a module are implemented in software, the program code may be stored and/or propagated on in one or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storage medium storing the program code. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

More specific examples of the computer readable storage medium may include but are not limited to a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, a holographic storage medium, a micromechanical storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, and/or store program code for use by and/or in connection with an instruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signal medium. A computer readable signal medium may include a propagated data signal with 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 program code for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wire-line, optical fiber, Radio Frequency (RF), or the like, or any suitable combination of the foregoing

In one embodiment, the computer readable medium may comprise a combination of one or more computer readable storage mediums and one or more computer readable signal mediums. For example, program code may be both propagated as an electro-magnetic signal through a fiber optic cable for execution by a processor and stored on RAM storage device for execution by the processor.

Program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++, PHP or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

The computer program product may be shared, simultaneously serving multiple customers in a flexible, automated fashion. The computer program product may be standardized, requiring little customization and scalable, providing capacity on demand in a pay-as-you-go model.

The computer program product may be stored on a shared file system accessible from one or more servers. The computer program product may be executed via transactions that contain data and server processing requests that use Central Processor Unit (CPU) units on the accessed server. CPU units may be units of time such as minutes, seconds, hours on the central processor of the server. Additionally the accessed server may make requests of other servers that require CPU units. CPU units are an example that represents but one measurement of use. Other measurements of use include but are not limited to network bandwidth, memory usage, storage usage, packet transfers, complete transactions etc.

Aspects of the embodiments may be described above with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and computer program products according to embodiments of the invention. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by program code. The program code may be provided to a processor of a general purpose computer, special purpose computer, sequencer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

The program code may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

The program code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the program code which executed on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions of the program code for implementing the specified logical function(s).

It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated Figures.

Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and program code.

Instances in this specification where one element is “coupled” to another element can include direct and indirect coupling. Direct coupling can be defined as one element coupled to and in some contact with another element. Indirect coupling can be defined as coupling between two elements not in direct contact with each other, but having one or more additional elements between the coupled elements. Further, as used herein, securing one element to another element can include direct securing and indirect securing. Additionally, as used herein, “adjacent” does not necessarily denote contact. For example, one element can be adjacent another element without being in contact with that element.

As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of” means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

In the above description, certain terms may be used such as “up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” “over,” “under” and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same object. Further, the terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. Further, the term “plurality” can be defined as “at least two.”

The subject matter of the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. An internal combustion engine system, comprising:

a spark-ignited internal combustion engine powered by a gaseous fuel;

an exhaust system in exhaust gas receiving communication with the internal combustion engine, the exhaust system comprising an exhaust treatment component; and

a liquid fuel injection system in liquid fuel injecting communication with the exhaust system to inject liquid fuel into exhaust gas upstream of the exhaust treatment component.

2. The internal combustion engine system of claim 1, wherein the gaseous fuel comprises natural gas.

3. The internal combustion engine system of claim 1, wherein the liquid fuel comprises gasoline.

4. The internal combustion engine system of claim 1, wherein the liquid fuel injection system injects liquid fuel into the exhaust gas based on an air-to-fuel ratio of the exhaust gas generated by the spark-ignited internal combustion engine.

5. The internal combustion engine system of claim 1, wherein the spark-ignited internal combustion engine generates exhaust gas with an air-to-fuel ratio above 1.0.

6. The internal combustion engine system of claim 1, wherein the exhaust treatment component stores oxygen, and wherein the liquid fuel injection system injects liquid fuel into the exhaust gas based on an oxygen storage capacity of the exhaust treatment component.

7. The internal combustion engine system of claim 1, wherein the liquid fuel injection system injects liquid fuel into the exhaust gas during a cold start of the spark-ignited internal combustion engine.

8. The internal combustion engine system of claim 1, wherein the exhaust system comprises an exhaust manifold coupled to the spark-ignited internal combustion engine, and wherein the liquid fuel injection system injects liquid fuel into the exhaust manifold.

9. The internal combustion engine system of claim 1, further comprising a gaseous fuel injection system in gaseous fuel injecting communication with the spark-ignited internal combustion engine, wherein the liquid fuel injection system injects liquid fuel into the exhaust gas independently of the injection of gaseous fuel injected into the engine by the gaseous fuel injection system.

10. The internal combustion engine system of claim 1, wherein quantity and timing of the injection of liquid fuel into the exhaust gas by the liquid fuel injection system is based solely on conditions of the internal combustion engine system downstream of the spark-ignited internal combustion engine.

11. The internal combustion engine system of claim 1, wherein the exhaust treatment component comprises an oxidation catalyst.

12. The internal combustion engine system of claim 1, wherein the exhaust treatment component comprises a three-way catalyst.

13. The internal combustion engine system of claim 1, wherein the liquid fuel injection system comprises a retrofitted diesel exhaust fluid injection system.

14. The internal combustion engine system of claim 1, wherein the exhaust treatment component comprises a nitrogen oxide reduction catalyst.

15. The internal combustion engine system of claim 1, wherein the gaseous fuel comprises substantially solely natural gas.

16. An electronic control module for a spark-ignited internal combustion engine powered by a gaseous fuel, comprising:

an exhaust system condition module that determines a condition of an exhaust system in exhaust gas receiving communication with the spark-ignited internal combustion engine; and

a liquid fuel control module that commands the dithering of a liquid fuel into the exhaust system based on the condition of the exhaust system.

17. The electronic control module of claim 16, wherein the exhaust system comprises an oxidation catalyst, and wherein the condition of the exhaust system comprises an oxygen storage capacity of the oxidation catalyst.

18. The electronic control module of claim 16, wherein the condition of the exhaust system comprises an air-to-fuel ratio of exhaust gas generated by the spark-ignited internal combustion engine.

19. The electronic control module of claim 16, wherein the condition of the exhaust system comprises an exhaust gas temperature below a minimum threshold.

20. A method for dithering a liquid fuel into an exhaust system in exhaust receiving communication with a spark-ignited internal combustion engine powered by a gaseous fuel, the method comprising:

determining a condition of the exhaust system; and

injecting a liquid fuel into exhaust gas flowing through the exhaust system based on the condition of the exhaust system.