Patent Application
20070151230
This disclosure relates to a system for controlling emissions, and more particularly to a method and apparatus for controlling exhaust emissions.
Combustion engines, such as, for example, compression or spark ignition engines, can produce a variety of byproducts that may be environmentally harmful, such as, for example, nitric oxides, sulfur-containing acidic species, and/or hydrocarbons. Various systems and methods have been used to minimize the release of such byproducts to the environment. For example, new fuels are being developed which lower the levels of sulfur-acids produced during fuel combustion. Additionally, exhaust systems are available which absorb, e.g., by trapping, and/or convert, e.g., by transforming into innocuous substances, harmful chemicals before release to the environment.
Usually, engine exhaust systems include one or more catalysts that are configured to absorb and/or convert hydrocarbons and thus reduce potentially harmful exhaust emissions to the environment. Often, such catalysts have an optimum temperature range for absorption of hydrocarbons. Specifically, such catalysts, may be incapable or less capable of absorbing and/or converting hydrocarbons when cold, e.g., after a cold engine start or after extended periods of engine idling, as when warm. Until cold catalysts are heated above a threshold temperature, significant amounts of hydrocarbons may be released to the environment.
U.S. Pat. No. 6,666,021 (“the '021 patent”) issued to Lewis et al. discloses a method for adaptive engine control for vehicle starting. The system of the '021 patent compares an exhaust temperature, subsequent to engine cranking, to a predetermined temperature. If the exhaust temperature is below the predetermined temperature, the engine is operated in a cold mode to minimize emissions of hydrocarbons to a cold catalyst. A cold mode operation provides a lean air-fuel ratio and retards the ignition timing to minimize hydrocarbon emissions. The system of the '021 patent, monitors the exhaust temperature and subsequently operates the engine in a run mode when the exhaust temperature is above the predetermined temperature.
Although the system of the '021 patent may minimize hydrocarbon emissions during a cold mode, the system of the '021 patent estimates the operability of the catalyst based on exhaust temperatures. Additionally, the system of the '021 patent may inadequately estimate when the catalyst is within a suitable temperature range and may unnecessarily sacrifice engine performance for lower emissions when the catalyst may be capable of absorbing and/or converting a sufficient amount of hydrocarbons from the exhaust.
The present disclosure is directed at overcoming one or more of the shortcomings set forth above.
In a first aspect, the present disclosure is directed to a method for controlling exhaust emissions. The method includes producing exhaust having hydrocarbons and directing the exhaust through a converter. The method also includes directing the exhaust from the converter to an environment and determining a first rate indicative of a rate of hydrocarbons directed to the environment. The method further includes comparing the first rate with a predetermined rate and adjusting the production of exhaust, if the first rate is greater than the predetermined rate.
In another aspect, the present disclosure is directed to a system for monitoring emissions. The system includes an engine configured to produce hydrocarbons at a first rate. The system also includes a converter configured to convert hydrocarbons at a second rate and release hydrocarbons to an environment at a third rate. The system further includes a controller configured to adjust parameters of the engine to produce hydrocarbons at a fourth rate less than the first rate when the third rate is greater than a predetermined rate.
In yet another aspect, the present disclosure is directed to a method of operating an engine. The method includes monitoring at least one engine parameter indicative of an operational condition of an engine configured to produce exhaust including hydrocarbons. The method also includes monitoring a temperature and a pressure, each indicative of an operational condition of a converter, the converter including a catalyst configured to convert the hydrocarbons at a first rate and release the hydrocarbons to an environment at a second rate. The method further includes changing a status of the engine when the second rate is greater than a predetermined rate.
Engine 12 may include, for example, a diesel engine, a gasoline engine, a gaseous fuel driven engine, or any other engine known in the art. Engine 12 may be configured to supply power to operatively connected loads, such as, for example, traction devices, hydraulic pumps, and/or other loads known in the art. Specifically, engine 12 may be configured to operate in one or more operational modes in which engine 12 may have different operating conditions. For example, engine 12 may be configured to operate in a first mode in which an exhaust is produced including an amount of hydrocarbons less than an amount of hydrocarbons produced in a second mode. Engine 12 may be controlled to operate in different modes by controller 18 as a function of a determined desired status of engine 12. It is contemplated that engine 12 may include one or more piston-cylinder arrangements disposed in an “in-line” or “V” configuration defining combustion chambers and connected to a crankshaft, one or more valves operatively associated with the combustion chambers to affect the flow of fluids into and out of the combustion chambers, and a fuel delivery system configured to deliver fuel to the combustion chamber as is conventional in the art. It is also contemplated that engine 12 may capable of operating in any number of different modes in which operational parameters, such as, for example, fuel delivery timing, valve timing, ignition timing, clean exhaust recirculation amounts, fuel amounts, and/or any other parameter known in the art may be varied either in conjunction or independently. It is further contemplated that engine 12 may, alternatively, include a rotary engine.
Converter 14 may include any conventional catalyst device such as, for example, a catalyst trap, a catalytic converter, and/or a particulate filter, and may be configured to absorb and/or convert hydrocarbons. Specifically, converter 14 may include a catalyst such as, for example, platinum or ammonia, in any mass phase, such as, for example, gaseous, aqueous, or solid, configured to absorb and/or convert hydrocarbons present within an exhaust. Converter 14, via the catalyst, may convert hydrocarbons into innocuous elements or molecules such as, for example, inert gases and/or water. Converter 14, via the catalyst, may absorb hydrocarbons by physically trapping molecules within the catalyst and/or any other suitable filter. It is contemplated that converter 14, and in particular, the catalyst, may be less active, e.g., may be less capable of absorbing and/or converting hydrocarbons, within certain temperature ranges. For example, the catalyst may, above a first threshold temperature, be capable of absorbing and/or converting substantially all hydrocarbons from an exhaust, may below the first threshold temperature and above a second threshold temperature be capable of absorbing and/or converting significantly less hydrocarbons from an exhaust, and may below the second threshold temperature be capable of absorbing and/or converting substantially no hydrocarbons from an exhaust. It is also contemplated that first and second threshold temperatures may be any temperature and may be dependent upon the type of catalyst. It is further contemplated that an innocuous substance may be any substance less harmful to environment 16 than the hydrocarbons produced by engine 12.
Controller 18 may be configured to affect the operation of engine 12 between the different modes. Controller 18 may include one or more microprocessors, a memory, a data storage device, a communications hub, and/or other components known in the art. It is contemplated that controller 18 may be integrated within a general control system capable of controlling additional various functions of a exhaust system 10 and/or system other than exhaust system 10. Controller 18 may be configured to receive input signals from sensors 20, 22, 24, 26 via respective communication lines. Controller 18 may perform one or more algorithms to determine appropriate output signals to affect the operation of engine 12 and may deliver the output signals via one or more suitable communication lines. It is contemplated that controller 18 may be further configured to receive additional inputs indicative of various operating parameters of exhaust system 10, such as, for example, exhaust flow rate.
Sensors 20, 22 may include any conventional sensor configured to deliver a signal indicative of a temperature. Sensor 20 may be disposed between engine 12 and converter 14 and may be configured to communicate a signal indicative of a temperature of an exhaust upstream of converter 14. Sensor 22 may be disposed between converter 14 and environment 16 and may be configured to communicate a signal indicative of a temperature of an exhaust downstream of converter 14. Sensor 24 may include any conventional sensor configured to deliver a signal indicative of a pressure. Sensor 24 may be disposed relative to converter 14 and may be configured to communicate a signal indicative of a pressure within converter 14, e.g., indicative of the pressure of an exhaust within converter 14. It is contemplated that sensors 20, 22, 24 may be disposed at any location suitable for sensing and communicating temperature or pressure, as desired. It is also contemplated that sensors 20, 22, 24 may be configured to communicate any type of signal such as, for example, a voltage or a current.
Sensor 26 may include any conventional sensor configured to deliver a signal indicative of an operating parameter of engine 12. For example, sensor 26 may include one or more sensors disposed relative to components of engine 12 and may be configured to communicate signals indicative of one or more parameters, such as, for example, rotational speed of a crankshaft, valve position, air-fuel ratio, temperature, pressure, and/or any other parameter known in the art.
Status logic 30 may include one or more algorithms configured to be performed and/or executed by controller 18 to determine a desired operating status of engine 12. Specifically, status logic 30 may include one or more databases, two- or three-dimensional maps, look-up tables, equations, functions, and/or any other mathematical relationship known in the art. Status logic 30 may manipulate inputs received from sensors 20, 22, 24, 26 as a function of one or more variable or non-variable parameters, and/or predetermined constants, to determine status output 60. For example, status logic 30 may be configured to determine if a rate of hydrocarbons released to environment 16 by converter 14, e.g., that converter 14 has not absorbed and/or converted from the exhaust, is above a predetermined value. Controller 18 may be configured to vary one or more parameters of engine 12 as a function of status output 60, to reduce the amount of hydrocarbons produced by engine 12. It is noted that the references within the description of status logic 30 set forth below regarding algorithms including a particular mathematical relationship, e.g., an equation or a two-dimensional map, are for exemplary purposes only and it is contemplated that controller 18 may perform algorithms via any suitable mathematical relationship known in the art, e.g., an equation, any-dimensional map, a physics based model, an empirical model, and/or a look-up table, to determine a desired variable. It is contemplated that each and/or any of the variables determined via one or more algorithms within status logic 30 may include predetermined minimum and/or maximum values which status logic 30 may utilize within subsequent algorithms regardless of the determined variable as is conventional in the art. For example, one or more of the mathematical relationships within status logic 30 may determine a first variable by a division of a second variable that could be zero. As such, status logic 30 may determine the first variable to be a predetermined maximum value instead of determining the first variable to be a mathematical unknown, e.g., a positive number divided by zero.
Step 42 may be configured to determine a rate of hydrocarbons produced (d_Produced/d_Time) by engine 12. Specifically, step 42 may include one or more two- or three-dimensional maps and may be configured to determine an amount of hydrocarbons produced by engine 12 per a unit time. For example, step 42 may include one or more maps configured to relate engine input 40 and predetermined rates of hydrocarbon produced.
Step 44 may be configured to determine a temperature indicative of an average temperature (Avg-Temp) of converter 14. Specifically step 44 may include one or more equations configured to functionally relate temperature inputs 32, 34 to determine an average thereof as is conventional in the art. Hereinafter the temperature as determined in step 44 will be referenced as an average converter temperature, however, it is noted that the temperature determined in step 44 may be indicative of the average temperature of converter 14 and may or may not be equal to an actual average temperature of converter 14.
Step 46 may be configured to determine a rate of hydrocarbons converted (d_Converted/d_Time), e.g., converted into an innocuous substance, by converter 14 and may include one or more equations and/or one or more two- or three-dimensional maps. Specifically, step 46 may compare a current average converter temperature, e.g., the average converter temperature determined in step 44, a previous average converter temperature, e.g., an average converter temperature determined when controller 18 performed a prior sequence of status logic 30, and an elapsed time since determining the previous average temperature to determine a rate of change in average temperature of converter 14 (d_Avg-Temp/d_Time). It is contemplated that a previous average converter temperature, e.g., zero, may be assumed when controller 18 performs the first sequence of status logic 30.
Additionally, step 46 may determine a current available hydrocarbon conversion capacity of converter 14 via one or more two- or three-dimensional maps relating average converter temperatures and predetermined hydrocarbon conversion capacities of converter 14. For example, step 46 may determine a capacity as a function of the current average converter temperature via one or more two- or three-dimensional maps relating capacity and temperatures. Step 46 may further compare the current capacity of converter 14, a previously determined capacity of converter 14, e.g., a determined capacity determined when controller 18 performed a prior sequence of status logic 30, and a change between the current and previous average temperatures to determine a change in hydrocarbon conversion capacity relative to a change in temperature (d_Converted/d_Avg-Temp). It is contemplated that the conversion capacity of converter 14 may be indicative of the rate of hydrocarbons converted by converter 14. For example, converter 14 may be configured to convert hydrocarbons at substantially full capacity less an efficiency factor. As such, step 46 may relate the determined rate of change of average temperatures (d_Avg-Temp/d_Time) and the determined change in hydrocarbon conversion capacity relative to the change in temperature (d_Converted/d_Avg-Temp) to determine a hydrocarbon conversion rate (d_Converted/d_Time). It is also contemplated that a previously determined capacity of converter 14, e.g., 100%, may be assumed when controller 18 performs the first sequence of status logic 30.
Step 48 may be configured to determine a rate of hydrocarbons released (d_Released/d_Time), e.g., a rate of hydrocarbons that are neither absorbed nor converted by converter 14. Specifically, step 48 may include one or more two- or three-dimensional maps configured to relate the current average converter temperature, a cumulative amount of hydrocarbons absorbed by converter 14, and predetermined amounts of hydrocarbons released by converter 14. It is contemplated that the cumulative amount of hydrocarbons absorbed by converter 14 may be determined in step 56, however, an initial amount of hydrocarbons absorbed by converter 14, e.g., zero, may be assumed when controller 18 performs the first sequence of status logic 30.
Step 50 may be configured to determine a standardizing factor and may include one or more equations and/or one or more two- or three-dimensional maps. Specifically, step 50 may be configured to determine a standardizing factor as a function of a space velocity of converter 14. For example, the average converter temperature may be functionally related with an appropriate universal gas constant and pressure input 36 to establish a density of the exhaust. Step 50 may additionally include receiving additional parameters to determine a mass flow rate of exhaust which may be functionally related with the density to determine a gas flow rate which may be functionally related with a volume of converter 14 to establish a space velocity (Gas_flowrate/Volume). Step 50 may further include one or more two- or three-dimensional maps relating space velocities and predetermined standardized factors. As such, a determined standardized factor may be configured to adjust a determined rate of hydrocarbons released, as determined in step 48, as a function of operational conditions of exhaust system 10. It is contemplated that step 50 may resolve received inputs according to any system of units known in the art. It is also contemplated that an exhaust rate may be established in any suitable manner known in the art, such as, for example, as a function of one or more operating parameters of engine 12 or flow meters disposed within exhaust system 10.
Step 52 may be configured to determine a standardized rate of hydrocarbons released by converter 14 (d_Released′/d_Time). Specifically, step 52 may include one or more equations configured to functionally relate the determined rate of hydrocarbons released by converter 14, as determined in step 48, and the determined standardized factor, as determined in step 50, to approximate the determined rate of hydrocarbons released as a function of the current operating conditions of exhaust system 10, e.g., average temperature, pressure, or flow rate, of exhaust system 10. As such, step 52 may adjust the rate of hydrocarbons released as a function of current operating conditions to, for example, improve the accuracy of the determined rate of hydrocarbons.
Step 54 may be configured to determine a rate of hydrocarbons absorbed by converter 14. Specifically, step 54 may resolve the rate of hydrocarbons produced by engine 12 (d_Produced/d_Time), the rate of hydrocarbons converted by converter 14 (d_Converted/d_Time) and the standardized rate of hydrocarbons released by converter 14 (d_Released′/d_Time). For example, step 54 may functionally combine the rate of hydrocarbons produced by engine 12, the rate of hydrocarbons converted by converter 14, and the rate of hydrocarbons released by converter 14 to determine the rate of hydrocarbons absorbed by converter 14 (d_Absorbed/d_Time). It is contemplated that step 54 may functionally subtract the rate of hydrocarbons converted and the rate of hydrocarbons released from the rate of hydrocarbons produced to determine the rate of hydrocarbons absorbed by converter 14.
Step 56 may be configured to determine a cumulative amount of hydrocarbons absorbed by converter 14. Specifically, step 56 may functionally relate the rate of hydrocarbons absorbed (d_Absorbed/d_Time), determined in step 54, and an elapsed time (d_Time) to determine an amount of hydrocarbons absorbed by converter 54, e.g., an amount of hydrocarbons currently absorbed by converter 14. Step 56 may combine the currently absorbed amount of hydrocarbons with a previously determined amount of hydrocarbons absorbed, e.g., an amount of hydrocarbons absorbed by converter 14 as determined by controller 18 performing a prior sequence of status logic 30, to determine the cumulative amount of hydrocarbons absorbed by converter 14. The determined cumulative amount of hydrocarbons absorbed may be related within step 48 to determine a rate of hydrocarbons released by converter 14. It is contemplated that an initial amount of hydrocarbons absorbed by converter 14, e.g., zero, may be assumed when controller 18 performs the first sequence of status logic 30.
Step 58 may be configured to compare the rate of hydrocarbons released by converter 14, as determined in step 48, with a predetermined value. Step 58 may further be configured to establish status output 60 to indicate a first mode if the rate of hydrocarbons released by converter 14 is greater than a predetermined value. Step 58 may also be configured to establish status output 60 to indicate a second mode if the rate of hydrocarbons released by converter 14 is less than a predetermined value. Specifically, step 58 may include one or more equations configured to functionally relate the determined rate of hydrocarbons released and a predetermined value to determine if the rate of hydrocarbons released to environment 18 is greater than the predetermined value. As such, controller 18 and, in particular status logic 30, may affect control of engine 12 to operate in at least two modes, a first and a second mode.
Controller 18 may be configured to control one or more parameters of engine 12 in response to status output 60. For example, in response to a status output 60 indicative of a first mode, controller 18 may, for example, advance ignition timing, increase the amount of clean exhaust recirculated into engine 12, operate engine 12 with a lean air-fuel ratio, and/or may vary other operational parameters of engine 12. Additionally, in response to status output 60 indicative of a second mode, controller 18 may not adjust the operational parameters of engine 12. As such, engine 12 may, in the first mode, produce less hydrocarbons than that produced by engine 12 in the second mode. Accordingly, status logic 30 may be configured to control engine 12 as a function of a rate of hydrocarbons released to environment 16. Specifically, control logic 30 may be configured to control engine 12 to produce less hydrocarbons when converter 14 is less capable of absorbing and/or converting hydrocarbons and control engine 12 to produce more hydrocarbons when converter 14 is more capable of absorbing and/or converting hydrocarbons.
The present disclosure provides a system for controlling exhaust emissions and may be applicable to any exhaust system. The disclosed system may absorb and/or convert hydrocarbons within exhaust and may adjust the production of exhaust as a function of the hydrocarbons directed to an environment. The operation of exhaust system 10 will be explained below.
Exhaust system 10 may be operated at different conditions. For example, engine 12 may be operated in a start-up, idle, shut-down, or at various power, e.g., torque and rotational speed, output conditions. As such, engine 12 may produce exhaust having different properties, such as, for example, temperature or emissions, at different conditions. Additionally, converter 14 may be operated at various conditions as a function of the condition of engine 12. For example, during a start-up or an idle engine condition, converter 14 may be operating at a cold condition, whereas during a prolonged power output condition, converter 14 may be operating at a warm condition. A cold operational condition of converter 14 may adversely impact the performance of a catalyst therein, e.g., a catalyst may be capable of converting less hydrocarbons at a cold condition than at a warm condition. As such, during operation of converter 14 at cold conditions, an undesirable amount and/or rate of hydrocarbons may released by converter 14 and may be directed to environment 16. Because converter 14 may not be capable of absorbing and/or converting hydrocarbons as desired, engine 12 may be controlled by controller 18 to produce less hydrocarbons.
Controller 18 may receive inputs from sensors 20, 22, 24, 26 to monitor the parameters of converter 14 and engine 12. Specifically, controller 18 may perform status logic 30 to determine a rate of hydrocarbons released by converter 14 and establish an appropriate status output 60 as a function thereof. For example, controller 18 may determine a rate of hydrocarbons released by converter 14 to be greater than a desirable rate. Accordingly, controller 18 may determine a status output 60 configured to adjust the performance of engine 12 to produce less hydrocarbons, e.g., determine status output 60 to indicate a first mode. It is contemplated that controller 18 may be configured to adjust any suitable parameter of engine 12 so as to produce less hydrocarbons, such as, for example, advance ignition timing, retard valve timing, operate engine 12 with a leaner air-fuel ratio, and/or adjust any other parameter.
Controller 18 may be configured to repeat status logic 30 at any desired frequency, such as, for example, periodically, substantially continuously, and/or at non-uniform cycle times. As such, controller 18 may determine status output 60 as a function of a rate of hydrocarbons released by converter 14, which may be determined as a function of operational conditions of exhaust system 10 and, in particular, engine 12 and converter 14. Accordingly, controller 18 may adjust the operation of engine 12 as a function of a rate of hydrocarbons released by converter 14.
Because controller 18 determines a rate of hydrocarbons released by converter 14, engine 12 may be controlled to produce less hydrocarbons when converter 14 is less capable of absorbing and/or converting hydrocarbons. For example, controller 18 may control engine 12 to produce less hydrocarbons when converter 14 and, in particular, a catalyst therein, may be incapable of absorbing and/or converting hydrocarbons from an exhaust as desired. Because controller 18 controls engine 12 as a function of a rate of hydrocarbons released by converter 14, engine 12 may be more accurately controlled than if controlled in response to a temperature or time sensor configured to indicate when a catalyst may be capable of absorbing and/or converting hydrocarbons as desired. The above disclosure has been described with reference to reducing hydrocarbons generically for clarification purposes and it is contemplated that the present disclosure may be applicable to control any type of hydrocarbons, such as, for example, unburned fuel and/or soluble organic fractions.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system for reducing exhaust emissions. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
