Patent Description:
Known embodiments of the state of the art are disclosed for example by <CIT>, <CIT> or <CIT>.

Internal combustion engines are ideally operated in a way that the combustion mixture contains air and fuel in the exact relative proportions required for a stoichiometric combustion reaction (i.e., where the fuel is burned completely. ) A rich-burn engine may operate with a stoichiometric amount of fuel or a slight excess of fuel, while a lean-burn engine operates with an excess of oxygen (O<NUM>) compared to the amount required for stoichiometric combustion. The operation of an internal combustion engine in lean mode may reduce throttling losses and may take advantage of higher compression ratios thereby providing improvements in performance and efficiency. Rich burn engines have the benefits of being relatively simple, reliable, stable, and adapt well to changing loads. Rich burn engines may also have lower nitrogen oxide emissions, but at the expense of increased emissions of other compounds.

In order to comply with emissions standards, many rich burn internal combustion engines utilize catalysts, such as nonselective catalytic reduction (NSCR) subsystems (known as <NUM>-way catalysts). Catalysts may reduce emissions of nitrogen oxides such as nitric oxide (NO) and nitrogen dioxide (NO<NUM>) (collectively NOx), carbon monoxide (CO), ammonia (NH<NUM>), methane (CH<NUM>), other volatile organic compounds (VOC), and other compounds and emissions components by converting such emissions components to less toxic substances. This conversion is performed in a catalyst component using catalyzed chemical reactions. Catalysts can have high reduction efficiencies and can provide an economical means of meeting emissions standards (often expressed in terms of grams of emissions per brake horsepower hour (g/bhp-hr)).

According to the invention, a system according to claim <NUM> and a method according to claim <NUM> are provided in order to achieve low CO emissions levels.

The foregoing summary, as well as the following detailed description, is better understood when read in conjunction with the drawings. For the purpose of illustrating the claimed subject matter, there is shown in the drawings examples that illustrate various embodiments; however, the invention is not limited to the specific systems and methods disclosed.

These and other features, aspects, and advantages of the present subject matter will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:.

<FIG> is a chart illustrating example CO and NOx emissions curves relative to lambda (λ). As one skilled in the art will recognize, lambda is the air-fuel equivalence ratio (actual air-fuel ratio / stoichiometric air-fuel ratio). NOx and CO concentrations are not linear, but rather changed dramatically as the "knee" of each of the respective curve representing the concentration of NOx and CO is approached. In this example, as shown in <FIG>, the g/bhp-hr of NOx emitted may increase at a much greater rate as lambda surpasses <NUM> and approaches <NUM>, while the g/bhp-hr of CO emitted may increase at a much greater rate as lambda declines below <NUM> and retreats towards <NUM>. This chart also shows the compliance window, or operating window, in which CO and NOx emissions are below desired levels. The range of lambda in this window is dependent on the current NOx and CO emission levels. However, as conditions change in the engine and/or the environment in which the engine is operating, NOx and CO emissions levels for any particular lambda may change, and therefore the operating window may change in size and location relative to lambda. Thus, as NOx and CO emissions levels change for an engine operating with a particular air-fuel ratio, the air-fuel ratio may need to be adjusted to ensure that the engine maintains low emissions levels. Note that this chart is presented as a demonstrative aide only to illustrate the problem solved by the current disclosure. No limitation on the present subject matter is to be construed from the chart in <FIG>.

<FIG> illustrates exemplary system <NUM>, including engine <NUM> and catalyst <NUM>, that may be implemented according to an embodiment. Note that the entirely of system <NUM> may also be referred to as an "engine". System <NUM> is a simplified block diagram that will be used to explain the concepts disclosed herein, and therefore is not to be construed as setting forth any physical requirements or particular configuration required for any embodiment disclosed herein. All components, devices, systems and methods described herein may be implemented with or take any shape, form, type, or number of components, and any combination of any such components that are capable of implementing the disclosed embodiments. All such embodiments are contemplated as within the scope of the present disclosure.

Engine <NUM> may be any type of internal combustion engine or any device, component, or system that includes an internal combustion component that generates exhaust gases. In an embodiment, engine <NUM> may be a natural gas fueled internal combustion engine configured to operate with a stoichiometric amount of fuel or a slight excess of fuel in proportion to oxygen (i.e., rich). However, the disclosed embodiments are not limited to such an engine, and may be used with any type of stationary or mobile internal combustion engine. Engine <NUM> may exhaust gases through exhaust piping <NUM> into catalyst <NUM> which then exhausts converted exhaust gases. Catalyst <NUM> represents one or more catalysts of any type, and any combination of any types of catalysts.

In an embodiment, rather than requiring manual adjustment of the air-fuel mixture to ensure that low emissions are maintained, sensors may be used at various points along the exhaust flow to collect data regarding the content of exhaust gases. The collected data may be provided to emissions control module <NUM>, which may be any type of device, component, computer, or combination thereof, that may be configured to determine an appropriate air-fuel mixture based on the level of one or more compounds in exhaust gases. Emissions control module <NUM> may, upon determining the optimal air-fuel mixture or an appropriate adjustment in the air-fuel mixture, transmit instructions to or otherwise control air-fuel regulators <NUM> and <NUM> so that air-fuel regulators <NUM> and <NUM> cause the correct air-fuel mixture to be sent to engine <NUM>. Each of air-fuel regulators <NUM> and <NUM> may be a fuel system, carburetor, fuel injector, fuel pass regulator, any system including one or more of these, or any combination thereof.

In an embodiment, system <NUM> may include pre-catalyst sensors, mid-catalyst sensors, and post-catalyst sensors. In this embodiment, post-catalyst sensor <NUM> may be an oxygen (e.g., O<NUM>) sensor and post-catalyst sensor <NUM> may be a NOx sensor. Post-catalyst sensor <NUM> may also, or instead, be a CO sensor. Post-catalyst sensor <NUM> may feed data reflecting detected levels of oxygen to emissions control module <NUM> and post-catalyst sensor <NUM> may feed data reflecting detected levels of NOx and/or CO to emissions control module <NUM>. Post-catalyst sensors <NUM> and/or <NUM> may sense overall catalyst efficiency, but may be relatively slow to report changes in the composition of exhaust gases to emissions control module <NUM> because it senses the gases only after they have been through the entire catalyst system used by engine <NUM>.

Mid-catalyst sensor <NUM> may be configured within any one catalyst brick within catalyst <NUM>, or may be any number of sensors configured in any number of catalyst bricks within catalyst <NUM>. Alternatively, mid-catalyst sensor <NUM> may be configured between two catalyst bricks within catalyst <NUM>, or may configured between two separate catalysts, each of which having one or more catalyst bricks. Note that catalyst <NUM> represents any number of individual catalysts of any type having any number of catalyst bricks, and mid-catalyst sensor <NUM> represents any number and type of sensors that may be configured to detect any type of content within a catalyst. All such variations are contemplated as within the scope of the present disclosure. Mid-catalyst sensor <NUM> may be an oxygen (e.g., O<NUM>) sensor and may provide an indication of the efficiency of catalyst <NUM>, reporting changes in exhaust gases to emissions control module <NUM> more rapidly than post-catalyst sensors <NUM> and <NUM> as mid-catalyst sensor <NUM> is configured to detect the level of oxygen at catalyst <NUM>. Pre-catalyst sensors <NUM> and <NUM> may be oxygen (e.g., O<NUM>) sensors and due to their location may react the fastest among the sensors as they will sense and report to emissions control module <NUM> the content of exhaust gas as it is emitted from engine <NUM> and before it travels into catalyst <NUM>.

Using the data received from one or more of post-catalyst sensors <NUM> and <NUM>, mid-catalyst sensor <NUM>, and pre-catalyst sensors <NUM> and <NUM>, emissions control module <NUM> may determine an appropriate air-fuel mixture and transmit data indicating the determined air-fuel mixture or otherwise instruct air-fuel regulators <NUM> and <NUM> to operate engine <NUM> using the determined air-fuel mixture.

In one embodiment, emissions control module <NUM> may determine an air-fuel mixture set point based on data from pre-catalyst sensors <NUM> and <NUM>, and then may modify that set point to determine a second set point based on data from mid-catalyst sensor <NUM>. The second set point may then be further modified based on data from post-catalyst sensors <NUM> and <NUM>.

In this embodiment, fewer sensors may be used to accomplish the same goals of automating efficient catalyst control. Specifically, in <FIG>, there is no mid-catalyst sensor. Data collected from post-catalyst sensors <NUM> and <NUM> and pre-catalyst sensors <NUM> and <NUM> may be provided to emissions control module <NUM>, which may be any type of device, component, computer, or combination thereof, that is configured to determine an appropriate air-fuel mixture based on the level of one or more compounds in exhaust gases. Emissions control module <NUM> may, upon determining the optimal air-fuel mixture or an appropriate adjustment in the air-fuel mixture, transmit instructions to or otherwise control air-fuel regulators <NUM> and <NUM> so that air-fuel regulators <NUM> and <NUM> cause the correct air-fuel mixture to be sent to engine <NUM>. Each of air-fuel regulators <NUM> and3242 may be a fuel system, carburetor, fuel injector, fuel pass regulator, any system including one or more of these, or any combination thereof.

In this embodiment, post-catalyst sensor <NUM> may be an oxygen (e.g., O<NUM>) sensor and post-catalyst sensor <NUM> may be a NOx sensor. Post-catalyst sensor <NUM> may also, or instead, be a CO sensor. Post-catalyst sensor <NUM> may feed data reflecting detected levels of oxygen to emissions control module <NUM> and post-catalyst sensor <NUM> may feed data reflecting detected levels of NOx and/or CO to emissions control module <NUM>. Post-catalyst sensors <NUM> and/or <NUM> may sense overall catalyst efficiency, but may be relatively slow to report changes in the composition of exhaust gases to emissions control module <NUM> because it senses the gases only after they have been through the entire catalyst system used by engine <NUM>. Pre-catalyst sensors <NUM> and <NUM> may be oxygen (e.g., O<NUM>) sensors and due to their location may react the fastest among the sensors as they will sense and report to emissions control module <NUM> the content of exhaust gas as it is emitted from engine <NUM> and before it travels into catalyst <NUM>.

Using the data received from one or more of post-catalyst sensors <NUM> and <NUM> and pre-catalyst sensors <NUM> and <NUM>, emissions control module <NUM> may determine an appropriate air-fuel mixture and transmit data indicating the determined air-fuel mixture or otherwise instruct air-fuel regulators <NUM> and <NUM> to operate engine <NUM> using the determined air-fuel mixture.

In one embodiment, emissions control module <NUM> may determine an air-fuel mixture set point based on data from pre-catalyst sensors <NUM> and <NUM>, and then may modify that set point to determine a second set point based on data from post-catalyst sensors <NUM> and <NUM>.

In an embodiment, an initial post-catalyst O<NUM> set-point level may be determined and loaded into a bias table stored at, or accessible by, emissions control module <NUM>. Based on the bias table, emissions control module <NUM> may modify the pre-catalyst O<NUM> air-fuel ratio set-point as the post-catalyst O<NUM> levels change. In this embodiment, emissions control module <NUM> may determine the catalyst operating window (an example of which is shown in <FIG>) through a sub-routine and set the determined air-fuel ratio set-point as a zero (<NUM>) bias point. Emissions control module <NUM> may then modify the pre-catalyst O<NUM> set-point as the post-catalyst O<NUM> level moves. The post-catalyst NOx sensor may be used in determining the initial set-point and in modifying the post-catalyst O<NUM> set-point bias table up and down as NOx levels change.

In an embodiment, emissions control module <NUM> may be configured with a predetermined emissions compliance level and/or catalyst efficiency. In such an embodiment, preconfigured NOx and/or CO grams level may be set and, upon detection of one or both of these levels being approached, met, and/or exceeded, a user may be notified of the out-of-compliance condition and/or a shutdown of the engine may be performed automatically by emissions control module <NUM>. In some embodiments, catalyst efficiency may be based on a determined amount of modification of pre-catalyst O<NUM> setpoints and/or other conditions, such as engine operating hours and load and monitored environmental conditions.

Any system or engine described herein may be operated to achieve an optimum O<NUM> set-point for NOx and CO compliance. For example, one or more NOx sensors as described herein may be used to determine a CO concentration that may be represented as an increase in the NOx parts-per-million (ppm) output as the rich knee of the lambda curve (see <FIG>) is approached. The increasing CO concentration when an air-fuel mixture is rich may create stable interference in a NOx sensor, where a NOx reading from such a sensor may indicate a higher level of NOx concentration where actually ammonia is being detected. In a lean air-fuel ratio, such a sensor may read similar levels of NOx as normal. Ammonia created at extremely rich air-fuel ratios may be reported as NOx concentration by a NOx sensor.

<FIG> illustrates exemplary, non-limiting method <NUM> of implementing an embodiment as disclosed herein. Method <NUM>, and the individual actions and functions described in method <NUM>, may be performed by any one or more devices or components, including those described herein, such as the systems illustrated in <FIG> and <FIG>. In an embodiment, method <NUM> may be performed by any other devices, components, or combinations thereof, in some embodiments in conjunction with other systems, devices and/or components. Note that any of the functions and/or actions described in regard to any of the blocks of method <NUM> may be performed in any order, in isolation, with a subset of other functions and/or actions described in regard to any of the other blocks of method <NUM> or any other method described herein, and in combination with other functions and/or actions, including those described herein and those not set forth herein. All such embodiments are contemplated as within the scope of the present disclosure.

At block <NUM>, data may be received at an emissions control module from one or more pre-catalyst sensors. Such sensors may be oxygen (e.g., O<NUM>) sensors and/or any other type of sensor. At block <NUM>, data may be received at an emissions control module from one or more mid-catalyst sensors. Such sensors may be oxygen (e.g., O<NUM>) sensors and/or any other type of sensor. At block <NUM>, data may be received at an emissions control module from one or more post-catalyst sensors. Such sensors may be oxygen (e.g., O<NUM>) sensors, NOx sensors, CO sensors, and/or any other type of sensor. Note that in an alternate embodiment, no mid-catalyst sensors may be present, and therefore the functions of block <NUM> may be omitted. It is contemplated that any number of sensors of any type may be used, and such sensors may be located at any location within an engine and catalyst system.

At block <NUM>, an emissions control module may make a determination, based on the data received from one or more sensors, of an appropriate air-fuel ratio. In many embodiments, this determination may be the selection of an air-fuel ratio that maintains or brings the emissions levels of an engine below predetermined levels, such as those mandated by the EPA. At block <NUM>, the emissions control module may instruct or otherwise cause one or more air-fuel regulators to implement the determined air-fuel ratio; i.e., operate the engine using the determined air-fuel ratio.

The technical effect of the systems and methods set forth herein is the ability to more efficiently control the air-fuel mixture used in an engine, and thereby more efficiently ensure that emissions of the engine are kept at desired levels. As will be appreciated by those skilled in the art, the use of the disclosed processes and systems may reduce the emissions of such engines to low levels and maintain those emissions at low levels without requiring manual intervention. Those skilled in the art will recognize that the disclosed systems and methods may be combined with other systems and technologies in order to achieve even greater emissions control and engine performance. All such embodiments are contemplated as within the scope of the present disclosure.

<FIG> and the following discussion are intended to provide a brief general description of a suitable computing environment in which the methods and systems disclosed herein and/or portions thereof may be implemented. For example, the functions of emissions control modules <NUM> and <NUM> may be performed by one or more devices that include some or all of the aspects described in regard to <FIG>. Some or all of the devices described in <FIG> that may be used to perform functions of the claimed embodiments may be configured in a controller that may be embedded into a system such as those described with regard to <FIG> and <FIG>. Alternatively, some or all of the devices described in <FIG> may be included in any device, combination of devices, or any system that performs any aspect of a disclosed embodiment.

Although not required, the methods and systems disclosed herein may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer, such as a client workstation, server or personal computer. Such computer-executable instructions may be stored on any type of computer-readable storage device that is not a transient signal per se. Generally, program modules include routines, programs, objects, components, data structures and the like that perform particular tasks or implement particular abstract data types. Moreover, it should be appreciated that the methods and systems disclosed herein and/or portions thereof may be practiced with other computer system configurations, including hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers and the like. The methods and systems disclosed herein may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices.

<FIG> is a block diagram representing a general purpose computer system in which aspects of the methods and systems disclosed herein and/or portions thereof may be incorporated. As shown, the exemplary general purpose computing system includes computer <NUM> or the like, including processing unit <NUM>, system memory <NUM>, and system bus <NUM> that couples various system components including the system memory to processing unit <NUM>. System bus <NUM> may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory may include read-only memory (ROM) <NUM> and random access memory (RAM) <NUM>. Basic input/output system <NUM> (BIOS), which may contain the basic routines that help to transfer information between elements within computer <NUM>, such as during start-up, may be stored in ROM <NUM>.

Computer <NUM> may further include hard disk drive <NUM> for reading from and writing to a hard disk (not shown), magnetic disk drive <NUM> for reading from or writing to removable magnetic disk <NUM>, and/or optical disk drive <NUM> for reading from or writing to removable optical disk <NUM> such as a CD-ROM or other optical media. Hard disk drive <NUM>, magnetic disk drive <NUM>, and optical disk drive <NUM> may be connected to system bus <NUM> by hard disk drive interface <NUM>, magnetic disk drive interface <NUM>, and optical drive interface <NUM>, respectively. The drives and their associated computer-readable media provide non-volatile storage of computer readable instructions, data structures, program modules and other data for computer <NUM>.

Although the exemplary environment described herein employs a hard disk, removable magnetic disk <NUM>, and removable optical disk <NUM>, it should be appreciated that other types of computer readable media that can store data that is accessible by a computer may also be used in the exemplary operating environment. Such other types of media include, but are not limited to, a magnetic cassette, a flash memory card, a digital video or versatile disk, a Bernoulli cartridge, a random access memory (RAM), a read-only memory (ROM), and the like.

A number of program modules may be stored on hard disk drive <NUM>, magnetic disk <NUM>, optical disk <NUM>, ROM <NUM>, and/or RAM <NUM>, including an operating system <NUM>, one or more application programs <NUM>, other program modules <NUM> and program data <NUM>. A user may enter commands and information into the computer <NUM> through input devices such as a keyboard <NUM> and pointing device <NUM>. Other input devices (not shown) may include a microphone, joystick, game pad, satellite disk, scanner, or the like. These and other input devices are often connected to the processing unit <NUM> through a serial port interface <NUM> that is coupled to the system bus, but may be connected by other interfaces, such as a parallel port, game port, or universal serial bus (USB). A monitor <NUM> or other type of display device may also be connected to the system bus <NUM> via an interface, such as a video adapter <NUM>. In addition to the monitor <NUM>, a computer may include other peripheral output devices (not shown), such as speakers and printers. The exemplary system of <FIG> may also include host adapter <NUM>, Small Computer System Interface (SCSI) bus <NUM>, and external storage device <NUM> that may be connected to the SCSI bus <NUM>.

The computer <NUM> may operate in a networked environment using logical and/or physical connections to one or more remote computers or devices, such as remote computer <NUM>, air-fuel regulators <NUM>, <NUM>, <NUM>, and/or <NUM>. Each of air-fuel regulators <NUM>, <NUM>, <NUM>, and/or <NUM> may be any device as described herein capable of performing the regulation of air and/or fuel entering an engine. Remote computer <NUM> may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and may include many or all of the elements described above relative to the computer <NUM>, although only a memory storage device <NUM> has been illustrated in <FIG>. The logical connections depicted in <FIG> may include local area network (LAN) <NUM> and wide area network (WAN) <NUM>. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and the Internet.

When used in a LAN networking environment, computer <NUM> may be connected to LAN <NUM> through network interface or adapter <NUM>. When used in a WAN networking environment, computer <NUM> may include modem <NUM> or other means for establishing communications over wide area network <NUM>, such as the Internet. Modem <NUM>, which may be internal or external, may be connected to system bus <NUM> via serial port interface <NUM>. In a networked environment, program modules depicted relative to computer <NUM>, or portions thereof, may be stored in a remote memory storage device. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between computers may be used.

Computer <NUM> may include a variety of computer-readable storage media. Computer-readable storage media can be any available tangible media that can be accessed by computer <NUM> and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer-readable media may comprise computer storage media and communication media. Computer storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other tangible medium which can be used to store the desired information and which can be accessed by computer <NUM>. Combinations of any of the above should also be included within the scope of computer-readable media that may be used to store source code for implementing the methods and systems described herein. Any combination of the features or elements disclosed herein may be used in one or more embodiments.

Claim 1:
A system (<NUM>) comprising:
a catalyst (<NUM>);
an emission control module (<NUM>) configured to determine an air-fuel ratio and to control at least in air-fuel regulation to operate an engine (<NUM>) at the air-fuel ratio;
a first oxygen sensor (<NUM>) configured to detect oxygen content of gases entering the catalyst (<NUM>) and to report the oxygen contents of the gases entering the catalyst (<NUM>) to the emissions control module (<NUM>);
a second oxygen sensor (<NUM>) configured to detect oxygen content of gases exiting the catalyst (<NUM>) and to report the oxygen contents of the gases exiting the catalyst (<NUM>) to the emissions control module (<NUM>);
wherein the emissions control module (<NUM>) is configured to determine a first air-fuel ratio based on the contents of the gases entering the catalyst (<NUM>) based on the signal from the first oxygen sensor (<NUM>); and to determine a second air-fuel ratio by modifying the first air-fuel ratio based on the contents of the gases exiting the catalyst (<NUM>) at least based on the signal from the second oxygen sensor (<NUM>), and to control an air-fuel regulator (<NUM>,<NUM>) to operate an engine at the air-fuel ratio using the second air-fuel ratio;
the system being characterized in that it further comprises:
a carbon monoxide sensor (<NUM>) configured to detect carbon monoxide content of gases exiting the catalyst (<NUM>) and to report the carbon monoxide contents of the gases exiting the catalyst (<NUM>) to the emissions control module (<NUM>);
and that the determination of the second air-fuel ratio is further modifying the first air-fuel ratio based on the signal from the carbon monoxide sensor (<NUM>).