Patent Application
20080022657
Each of combustion chambers 30 may be configured with a slideably mounted piston (not shown) and may be configured to receive and combust materials including fuel and air, among other things (e.g., performance enhancing substances). A piston associated with a combustion chamber from combustion chambers 30 may be connected to a crankshaft (not shown) such that a rotation of the crankshaft results in a corresponding reciprocating motion of the piston.
Power source 18 may be configured to operate using a two-stroke, four-stroke, or any other suitable combustion cycle. A “stroke” may be defined as one-half rotation of the crankshaft wherein the piston moves from top-dead-center to bottom-dead center or vice versa. A standard combustion cycle may be based on power source configuration and defined as one complete set of piston strokes resulting in combustion of a fuel within combustion chambers 30 and a derivation of heat/power from the combustion. For example, a four-stroke combustion cycle may include an intake stroke during which, air is provided to the combustion chamber, a compression stroke during which, the air is compressed, a combustion stroke during which, fuel is combusted and power derived as the piston is driven downward by the resulting expansion of gases, and an exhaust stroke during which, the resulting gases are expelled from the combustion chamber. Other suitable combustion cycles known in the art may also be used without departing from the scope of this disclosure.
Combustion chambers 30 may be configured for compression ignition (CI), spark ignition (SI), homogeneous charge compression ignition (HCCI), or any other type of combustion ignition. For example, a diesel engine may initiate combustion as pistons (not shown) within combustion chambers 30 near top-dead-center and critical temperature and pressure are reached.
Combustion chambers 30 may be configured to receive a supply of fuel from fuel sources 38. Fuel sources 38 may include injectors or atomizers configured to inject fuel directly into combustion chambers 30. Fuel sources 38 may be configured to supply fuel at a specific time (timed injection) or, alternatively, may be configured to introduce fuel continuously or at random intervals. Configuration of fuel sources 38 may depend upon the combustion configuration of combustion chambers 30 (e.g., CI, SI, or HCCI and two-stroke, four-stroke, or other suitable configuration).
Fuel sources 38 may be operatively connected to fuel pump 34. Fuel pump 34 may be configured to deliver fuel from fuel storage 36 to fuel sources 38. Fuel pump 34 may include an injection pump of the rotary or distributor variety, or any other suitable pump, and may be driven indirectly by gears or chains from the crankshaft or by other methods (e.g., electrically). One of skill in the art will recognize that many types of pumps may function adequately and fall within the scope of the current disclosure.
The fuel supplied to combustion chambers 30 may include, for example, diesel fuel, gasoline, alcohols, propane, methane, or any other suitable fuel. The fuel may be supplied to fuel sources 38 under pressure, and/or fuel sources 38 may, themselves, be configured to further increase the pressure or velocity of the fuel. Fuel storage 36 may be configured to store fuel, among other things, and may include a tank or other similar container. Fuel may be supplied at timed intervals (e.g., based on power source 18 rotational position), randomly, and/or continuously. Control of the fuel source 38 may be regulated by methods known by those of ordinary skill in the art and appropriate for the type of power source in operation.
Intake manifold 26 may be configured to draw air from atmosphere or from an air source (e.g., a turbocharger) and provide an air charge to combustion chambers 30 via intake passages 24. For example, intake manifold 26 may be fluidly connected to a forced induction system such as the outlet of a turbocharger or supercharger. Intake manifold 26 may further be fluidly connected to at least one intake passage 24 which, in turn, may be fluidly connected to a combustion chamber 30. Fuel or other additive substances (e.g., performance boosting substances including propane) may also be supplied to intake manifold 26.
Intake passages 24 may be configured to carry substances including, air, fuel, and other substances, or any combination thereof, to combustion chambers 30. For example, at power source idle operation, intake passages 24 may be configured to provide an air charge to combustion chambers 30 containing between about three and ten times the amount of air necessary to execute one combustion stroke of a combustion cycle.
Intake passages 24 may be opened to combustion chambers 30 via intake valve assemblies (not shown) and/or airflow control elements 25 which may open and close as desired to facilitate, substantially limit, or stop the flow of materials (e.g., air) into combustion chambers 30. Airflow control elements 25 may include valves, flaps, actuators, and other components suitable for enabling or limiting flow of a gas through a passage (e.g., intake passages 24). Airflow controls elements 25 may function as and take the place of intake valve assemblies, or alternatively, both airflow control elements 25 and intake valve assemblies (not shown) may be present. Further, airflow control elements 25 may operate independently of separate intake valve assemblies (where present) or may operate in tandem to control airflow to combustion chambers 30. Additionally, it is important to note that airflow control elements 25 may be located in any location suitable for substantially limiting or stopping the flow of air to combustion chambers 30. For example, airflow control elements 25 may be located within intake manifold 26 or at an air source.
Airflow control elements 25 and intake valve assemblies associated with combustion chambers 30 may be directly or indirectly connected to the crankshaft by way of a timing device such that a rotation of the crankshaft results in corresponding opening and closing movements of the associated control or assembly. In addition, airflow control elements 25 and intake valve assemblies may include mechanical and/or electro-mechanical systems and may be activated or operated using any suitable method (e.g., pushrod, solenoid, etc.) to allow, substantially limit, or stop the flow of air to combustion chambers 30. Further, airflow control elements 25 and intake valve assemblies maybe operatively connected to controller 52 such that controller 52 may affect an activation or deactivation of both airflow control elements 25 and intake valve assemblies. Intake passages 24 may contain more or fewer elements as desired.
Combustion of a first fuel charge within combustion chambers 30 may result in at least a portion of the fuel reacting with a portion of an air charge provided to combustion chambers 30 during an intake stroke. Heat and/or power may be derived from the combustion of the fuel and air and, as a result, an exhaust gas including particulate matter (e.g., unburned hydrocarbons), NOx, CO2, and water, among other things, may be generated. Because the initial air charge may have contained three to ten times the amount of air necessary for combustion, the exhaust gas may be mixed with remaining air within combustion chambers 30. Depending on current temperatures and operating conditions, the remaining air within combustion chambers 30 may allow subsequent combustion strokes to be executed within combustion chambers 30 without the introduction of additional air and without allowing the generated exhaust gas to exit combustion chambers 30.
Exhaust passages 29 may be fluidly connected to combustion chambers 30 and configured to receive the exhaust gas generated as a result of combustion of the fuel within combustion chambers 30. The fluid connection from combustion chambers 30 to exhaust passages 29 may be opened and closed via exhaust valve assemblies (not shown) and/or exhaust flow control elements 27 which may open and close as desired to facilitate, substantially limit, or stop the flow of materials (e.g., exhaust) out of combustion chambers 30. Exhaust flow control elements 27 may include valves, flaps, actuators, and other components suitable for enabling or limiting flow of a gas through a passage (e.g., exhaust passages 29). Exhaust flow control elements 27 may function as and take the place of exhaust valve assemblies, or alternatively, both exhaust flow control elements 27 and exhaust valve assemblies (not shown) may be present. Further, exhaust flow control elements 27 may operate independently of exhaust valve assemblies (where present) or may operate in tandem to control exhaust flow from combustion chambers 30. Additionally, it is important to note that exhaust flow control elements 27 may be located in any location suitable for substantially limiting or stopping the flow of exhaust from combustion chambers 30. For example, exhaust flow control elements 27 may be located within exhaust manifold 28 or within exhaust system 17.
Exhaust flow control elements 27 and exhaust valve assemblies associated with combustion chambers 30 may be directly or indirectly connected to the crankshaft by way of a timing device such that a rotation of the crankshaft results in corresponding opening and closing movements of the associated control or assembly. In addition, exhaust flow control elements 27 and exhaust valve assemblies may include mechanical and/or electromechanical systems and may be activated or operated using any suitable method (e.g., pushrod, solenoid, etc.) to allow, substantially limit, or stop the flow of an exhaust gas from combustion chambers 30. Further, exhaust flow control elements 27 and exhaust valve assemblies may be operatively connected to controller 52 such that controller 52 may affect an activation or deactivation of both exhaust flow control elements 25 and exhaust valve assemblies.
Exhaust passages 29 may also be fluidly connected to an additive supply device 44 configured to provide an SCR reductant and/or an RPF catalyst to the exhaust gas. For example, additive supply device may inject an SCR reductant (e.g., ethanol or urea), to exhaust gas flowing out of combustion chambers 30 such that upon reaching SCR system catalyst 31, NOx emissions may be reduced. Although additive supply device 44 is depicted in
Exhaust manifold 28 may be fluidly linked to at least one exhaust passage 29 and may collect and receive an exhaust gas from the at least one exhaust passage 29. Exhaust manifold may operate to link several exhaust passages 29 together and receive the cumulative exhaust from exhaust passages 29. Exhaust manifold 28 may further include devices for supplying other substances (e.g., urea, ethanol, etc.) for mixture in the exhaust gas, or, alternatively, no such additional devices may be present. For example, exhaust manifold 28 may be fluidly connected to additive supply device 44, which may be configured to supply an SCR reductant and/or an RPF catalyst additive to exhaust manifold 28. Exhaust manifold 28 may be well insulated to prevent heat loss and assist in maintaining exhaust temperatures conducive for operation of an RPF and/or an SCR system.
Exhaust manifold 28 may include sensors (not shown) for detecting exhaust-gas temperatures, levels of exhaust-gas pollutants, and levels of other substances within the exhaust gas. Where the sensors indicate low exhaust-gas temperatures, controller 52 may cause appropriate steps to be taken to increase exhaust-gas temperatures (e.g., activating airflow control elements 25 and exhaust flow control elements 27, among other things). Exhaust manifold 28 may further include fluid connections to allow for recirculation of some exhaust gas and/or coupling of exhaust gas to the turbine of a turbocharger (not shown), among other things.
Exhaust manifold 28 may be fluidly connected to an exhaust system 17, which may be configured to receive the exhaust gas from exhaust manifold 28. Exhaust system 17 may include pipes, tubes, clamps, etc., and may direct the flow of the exhaust gas in various directions. Exhaust system 17 may also include sensors, mixing devices, and fluid connections to recirculation devices and turbocharger turbines (not shown), among other things.
RPF 23 may be fluidly connected to exhaust system 17 downstream of exhaust manifold 28 and configured to receive an exhaust gas. RPF 23 may be constructed from many materials and may be configured to remove particulate matter from the exhaust gas using physical, chemical, or other suitable methods, and any combination thereof. For example, a particulate filter utilizing physical methods of filtration may be manufactured from semi-penetrable or semi-porous materials including coredierite and/or silicon carbide. The filter may include a honeycomb type structure and each channel within the structure may be blocked at alternating ends. Such a configuration may force exhaust gas flowing into RPF 23 to pass through the semi-penetrable material into a surrounding channel. While exhaust gas may pass through the semi-penetrable material, particulate matter within the exhaust gas may be trapped on the walls of the semi-penetrable material, thereby removing the matter from the exhaust gas. Other types of filters and materials may also be used including, for example, sintered metal plates, foamed metal structures, fiber mats, and any other suitable filtration mediums.
RPF 23 may include a passively or actively regenerated particulate filter, or may be a combination thereof. Regeneration of a particulate filter may be useful for substantially limiting or eliminating accumulation of particulate matter within RPF 23. For example, a passively regenerated particulate filter may combust particulate matter within RPF 23 in the presence of a catalyst material and while exhaust temperatures are maintained above a predetermined temperature. Therefore, RPF 23 may include a metal promoter or catalyst dispersed within the filter material. The catalyst material may be designed to facilitate combustion or oxidation of particulate matter within RPF 23 such that substantial accumulation of particulates does not occur within RPF 23. Such catalyst materials may include coatings of precious metals (e.g., platinum, silver, etc.) on the filter substrate. Additionally, injection of catalytic materials (e.g., heavy metals) into the exhaust gas stream, combustion chamber, or other suitable locations may also be used to aid in regeneration of RPF 23.
Passive RPF regeneration may oxidize particulate matter (e.g., carbon and hydrocarbon materials) and may proceed via multiple complex chemical reactions. Simplified reactions may be summarized by the following equations:
C+O2→CO2 (1)
NO2+C→NO→+CO2 (2)
NO+O2→NOx (3)
Carbon present in particulate matter may be combusted in the presence of oxygen to produce CO2 as shown in equation 1. By reacting in the presence of a catalyst, the oxidation reaction may be initiated at temperature between about 200 degrees C. and 350 degrees C. As shown in equation 2, it may further be possible to react particulate matter with NO2 to form NO and CO2. The resulting NO may then react with available O2 to re-form NO2 as illustrated by equation 3. While NO2 is a NOx variant, the resultant NO2 may subsequently be treated utilizing SCR system catalyst 31 and a SCR reductant (e.g., ethanol) introduced to the exhaust gas stream, or by other suitable methods.
SCR system catalyst 31 may be disposed in exhaust system 17 downstream of RPF 23, or, alternatively, may be disposed upstream of RPF 23 as desired. Exhaust system 17 may direct flow of the exhaust gas such that the exhaust gas is received by SCR system catalyst 31 and caused to contact the contained catalytic materials.
SCR system catalyst 31 may be made from a variety of materials. SCR system catalyst 31 may include a catalyst support material and a metal promoter dispersed within the catalyst support material. The catalyst support material may include at least one of alumina, zeolite, aluminophosphates, hexaluminates, aluminosilicates, zirconates, titanosilicates, and titanates. In one embodiment, the catalyst support material may include at least one of-alumina and zeolite, and the metal promoter may include silver metal (Ag). Combinations of these materials may be used, and the catalyst material may be chosen based on the type of fuel used, the ethanol additive used, the air to fuel-vapor ratio desired, and/or for conformity with environmental standards. One of ordinary skill in the art will recognize that numerous other catalyst compositions may be used without departing from the scope of this disclosure. Further, multiple SCR system catalysts may also be included in exhaust system 17.
The lean-NOx catalytic reaction is a complex process including many steps. One of the reaction mechanisms, however, that may proceed in the presence of SCR system catalyst 31 can be summarized by the following reaction equations:
HC+O2 oxygenated HC (4)
NOx+oxygenated HC+O2→N2+CO2+H2O (5)
SCR system catalyst 31 may catalyze the reduction of NOx to N2 gas, as shown in equation (5). Further, as shown in equation (4), a hydrocarbon reducing agent may be converted to an activated, oxygenated hydrocarbon that may interact with the NOx compounds to form organo-nitrogen containing compounds. These materials may possibly decompose to isocyanate (NCO) or cyanide groups and eventually yield nitrogen gas (N2) through the series of reactions as summarized above. A well mixed reductant (e.g., ethanol) within the exhaust gas may further react in the presence of any remaining hydrocarbons (e.g., unburned fuel) in order to aid in the production of oxygenated hydrocarbons, as represented by equation (4).
Controller 52 may be a mechanical or an electrical based controller configured to control fuel flow, airflow, and exhaust flow, among other things, to and from combustion chambers 30. Controller may also be operatively connected to intake and exhaust valves and/or airflow control elements 25 and exhaust flow control elements 27. For example, controller 52 may send electric signals causing intake and exhaust valves and/or airflow control elements 25 and exhaust flow control elements 27 to open and close thereby allowing, substantially limiting, or stopping the flow of air and exhaust to and from combustion chambers 30. Flow control may be based on factors including RPF temperature, SCR system catalyst temperature, exhaust-gas temperature, power requirements, emissions requirements, and other suitable parameters. For example, during low load or idle operation of power source 18, exhaust temperatures and/or RPF temperatures may fall below a predetermined threshold temperature for operation of RPF 23 and/or SCR system catalyst 31 (e.g., around 200 degrees C.). Where a sensor present in RPF 23 or SCR system catalyst 31 indicates such a temperature condition, controller 52 may limit or stop the flow of air and exhaust by activating airflow control elements 25 and exhaust flow control elements 27, thereby effecting a decrease in current emissions to RPF 23 and/or SCR 31 and an increase in temperature of the resulting exhaust gas. Upon allowing the flow of exhaust and air, the increased temperature of the exhaust gas may allow RPF 23 and SCR system catalyst 31 to continue operation.
Controller 52 may store data related to fuel to air ratios for combustion in memory or other suitable storage location. Such data may enable a determination of how many combustion cycles may be executed within combustion chambers 30 before deactivating airflow control elements 25 and exhaust flow control elements 27 such that a fresh air charge is allowed to enter and heated exhaust gas to exit combustion chambers 30. Data may be experimentally collected and based on engine size, engine rotations per minute (RPM), engine load, among other things. Such data may be stored in a lookup table within controller 52 for reference or data may be calculated using algorithms stored within controller 52 and based on similar parameters. For example, controller 52 may contain data indicating that one combustion chamber of a particular engine operating at 600 RPM may complete six combustion strokes with a single air charge. Upon completion of six combustion strokes, or upon other suitable conditions, controller 52 may cause a fresh air charge to be introduced to combustion chambers 30 and exhaust gas to flow from combustion chambers 30.
The disclosed systems and methods may be applicable to any powered system that includes an exhaust gas producing power source, such as an engine. The disclosed systems and methods may allow for thermal management and emissions reduction from a power source. In particular, the disclosed systems and methods may assist in maintaining a predetermined exhaust-gas and catalyst temperature during idle and low-load operation of the power source. Operation of the disclosed systems and methods will now be explained.
Operation of combustion chambers 30 may be dependant on the ratio of air to fuel-vapor that is supplied during operation. When determining the air to fuel-vapor ratio, primary fuel as well as other combustible materials in combustion chamber 30 (e.g., propane, etc.) may be included as fuel-vapor. The air to fuel-vapor ratio is often expressed as a lambda value, which is derived from the stoichiometric air to fuel-vapor ratio. The stoichiometric air to fuel-vapor ratio is the chemically correct ratio for combustion to take place. A stoichiometric air to fuel-vapor ratio may be considered to be equivalent to a lambda value of 1.0.
Combustion chambers may operate at non-stoichiometric air to fuel-vapor ratios. A combustion chamber with a lower air to fuel-vapor ratio has a lambda less than 1.0 and is said to be rich. A combustion chamber with a higher air to fuel-vapor ratio has a lambda greater than 1.0 and is said to be lean.
Lambda may affect combustion chamber and exhaust temperatures, emissions, and fuel efficiency. A lean-operating combustion chamber may have higher combustion temperatures, improved fuel efficiency, and residual air within a combustion chamber following combustion as compared to a combustion chamber operating under stoichiometric or rich conditions. However, as lean operation may increase temperature, NOx production may also increase creating a need to maintain the temperature of an SCR system catalyst at predetermined level for efficient NOx reduction.
During low load and idle of a power source, lambda values of between 3.0 and 10.0 may be found within a combustion chamber following a first intake stroke. Also during such operation, exhaust gas temperatures may fall because a minimal amount of fuel may be combusted to maintain idle and low load operation. Because RPFs and SCR systems may provide maximum efficiency when maintained at a predetermined temperature, a method for managing the thermal output and exhaust emissions of an engine may be useful. In an exemplary embodiment of the present disclosure, upon sensing a low exhaust or catalyst temperature (e.g., RPF catalyst and/or SCR catalyst) a controller may take appropriate action to manage thermal characteristics of the power source to effect a temperature rise in exhaust gas while controlling power source emissions.
Where controller 52 determines that insufficient air exists within combustion chamber 30 (step 315: no) or that a temperature or temperatures are above a predetermined threshold (step 320: no), controller 52 may cause the deactivation of airflow control elements 25 and exhaust flow control elements 27 (step 335) allowing exhaust gas to flow from combustion chamber 30 into exhaust manifold 28 and a fresh air charge to flow through intake passage 24 into combustion chamber 30. A fluid connection between exhaust manifold 28 and exhaust system 17 may then allow the exhaust gas to be received by exhaust system 17. Exhaust system 17 may be configured to direct the exhaust gas flow through RPF 23 and/or SCR system catalyst 31 via a fluid connection (step 340). Because the exhaust gas may be maintained at least above a minimum temperature, RPF 23 may be enabled to filter and regenerate particulate matter, while SCR system catalyst 31 may reduce NOx emissions. This may result in the reduction efficiencies for particulate matter and NOx emissions greater than 90 percent and may meet federal regulations for year 2007 emissions.
Several advantages may be associated with the disclosed systems and method for power source thermal management and emissions reduction. For example, because a power source may continue to operate all combustion chambers, the power source may maintain balance and may be more responsive to sudden demands for additional power. Maintenance of power source balance may result in smoother low-load and idle operation. Also, there may be little or no lag time during re-activation of combustion chambers because the combustion chambers may continue to operate during thermal management.
Moreover, by continuing to provide fuel to all combustion chambers of the power source, more efficient combustion may be achieved by limiting combustion of rich mixtures within the combustion chambers. While lambda may decrease as additional combustion strokes occur, lambda may not fall below a predetermined value before additional air is introduced. This may lead to more efficient lean combustion and therefore, to better fuel economy and an overall reduction in hydrocarbon and other emissions.
Additionally, because combustion may continue in all cylinders, more fuel may be burned than if a portion of the cylinders were combusting additional fuel. More fuel being combusted may then result in a greater potential temperature rise of the resulting exhaust gas. This may, therefore, allow an RPF and an SCR system to reach and maintain a minimum or optimal operating temperature during low-load or idle operation in a decreased amount of time.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system and methods for power source thermal management and emissions reduction. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed systems and methods for power source thermal management and emissions reduction. 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.
