Procedures for increasing exhaust gas temperatures

Abstract

Method comprising: Operating a diesel engine (102) having a plurality of cylinders (106a-f) connected via an exhaust path (903) to a selective catalytic reduction (SCR) system (910) in a standard operating mode (200); Determining that the selective reduction catalyst (SCR) system (910) requires desulfurization; and in response to determining: Operating the diesel engine (102) in a desulfurization mode (202) which includes: Operating a first number of cylinders (106a-f) of the diesel engine (102) in a combustion mode and a second number of cylinders (106a-f) of the diesel engine (102) in a shutdown mode; Reducing a bar pressure in the desulfurization mode (202) relative to the standard operating mode (200); Injecting a first main amount of fuel into each of the cylinders (106a-f) operating in the combustion mode no earlier than 2 degrees before top dead center (TDC); and Injecting a first post-fuel quantity into each of the cylinders (106a-f) operating in the combustion mode after the main injection of fuel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 13 / 644,214, filed October 3, 2012, which is incorporated herein by reference in its entirety. BACKGROUND

[0002] The present application relates generally to the operation of internal combustion engines and, more particularly but not exclusively, to increasing temperatures of an exhaust stream produced by an internal combustion engine to facilitate, by way of non-limiting example, the regeneration of one or more components of an aftertreatment system.

[0003] Modern combustion engines must meet strict emission standards, including a maximum level of nitrogen oxides (NO x) that may be released. Many engines now use aftertreatment systems to reduce emissions from the engine to prescribed levels before they are released into the atmosphere. Aftertreatment systems often include several components, including particulate filters, oxidation catalysts, NO x -Adsorber, NO x Reduction catalysts, three-way catalysts, four-way catalysts, and may also contain multiple components of the same type at different locations along the aftertreatment system flow path. A well-known method for removing nitrogen oxides (NO x ) from engine exhaust gases is selective catalytic reduction (SCR). In this system, a catalyst is used to initiate a reaction between NO x molecules and a reducing agent to facilitate the NO x into ordinary atmospheric gases.

[0004] Over time, one or more components of the aftertreatment system may become masked by deposits of certain exhaust gas constituents, which can reduce the effectiveness of such components and lead to an undesirable increase in emissions. In particular, and by way of non-limiting example, SCR systems may become masked with sulfur deposits, which can reduce their effectiveness in removing nitrogen oxides (NO x ) from engine exhaust, particularly in situations where engines operate with high-sulfur fuels (e.g., with a sulfur content above 50 ppm) and load cycles at low temperatures. Accordingly, there is a need for further improvements in this technology area.

[0005] DE 102 58 452 A1 discloses a catalytic converter with early light-off using cylinder deactivation. US 2011 / 0 139 136 A1 relates to procedures for increasing the regenerative capacity of an aftertreatment system. DE 101 29 126 A1 relates to methods for influencing the operating temperature and a catalyst. US 2003 / 0 121 249 A1 relates to the deactivation of engine cylinders to improve the performance of exhaust gas purification systems. DE 10 2007 056 216 A1 relates to methods for accelerating the heating of a catalyst in the exhaust system of a turbocharged internal combustion engine with variable valve timing. SUMMARY

[0006] The invention is defined in the independent claims. Advantageous embodiments are defined in the dependent claims.

[0007] One embodiment is a particular strategy for increasing exhaust temperatures that includes deactivating a first group of cylinders while a second group of cylinders remains in a combustion mode, and injecting fuel into each cylinder of the second group of cylinders no earlier than 2 degrees before top dead center (TDC). The strategy also includes directing fuel-rich exhaust from the second group of cylinders into an exhaust path and oxidizing at least a portion of the fuel-rich exhaust gases in the exhaust path. In one embodiment, the oxidizing occurs independent of any catalytic influence. Other embodiments include particular methods, systems, and apparatus for increasing exhaust temperatures and / or regenerating one or more components of an aftertreatment system.Further embodiments, configurations, objects, features, advantages, aspects and benefits will become apparent from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of an application with an internal combustion engine and an aftertreatment system. Fig. Figure 2 is a schematic block diagram of a system for increasing exhaust gas temperatures. Fig. 3 is a schematic block diagram of a control of the Fig. 2 system shown. Fig. Figure 4 is an illustration of several fuel injection events. Fig. 5 is a schematic representation of an aftertreatment system Fig. Figure 6 is a schematic flow diagram illustrating a procedure for increasing exhaust gas temperatures. DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0008] Although the present invention is susceptible of many different forms, for the purpose of better understanding the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and the same will be described using technical language. It should be understood, however, that this is not intended to limit the scope of the invention. All variations and further modifications of the described embodiments and all further applications of the principles of the invention described herein as would normally occur to one skilled in the art to which the invention pertains are contemplated.

[0009] Fig. 1 is a schematic representation of an application 900 with a vehicle 902 having an internal combustion engine 102 from which an exhaust path 903 extends. The application 900 includes an aftertreatment system 904 in the exhaust path 903 that treats NO x-emissions and requires periodic regeneration operations. The engine 102 includes fuel injectors and a processing subsystem that controls the injectors and other aspects of the engine 102, which are discussed in more detail below. The application 900 serves as an exemplary platform for the presently described systems, procedures, methods, and apparatus for generating temperature and other exhaust conditions to contribute to the regeneration of one or more components of the aftertreatment system 904.

[0010] The aftertreatment system 904 includes one or more aftertreatment components that benefit from specific adaptations to the exhaust environment and / or require periodic regeneration events to remove soot, renew catalytic activity, and / or remove sulfur deposits, to name a few non-limiting possibilities. Example aftertreatment components include soot filters, catalyzed soot filters, NO x adsorbers, SCR catalyst components and / or oxidation catalysts. Examples of non-limiting regeneration processes include oxidizing soot from a soot filter, desorbing NO x from a NO x -Adsorber using rich and / or hot exhaust gases, dissolving adsorbed NH3 on an SCR catalyst and / or desulfurizing a catalyst using heat.

[0011] Fig.2 is a schematic block diagram 100 of a system for increasing exhaust gas temperatures. The system 100 includes the engine 102 having a plurality of reciprocating pistons 104a-f disposed within respective cylinders 106a-f. Although the engine 102 is illustrated as including six reciprocating pistons 104a-f and six corresponding cylinders 106a-f, it should be understood that configurations are possible in which the engine 102 has a different number of reciprocating pistons and corresponding cylinders, including configurations in which the engine 102 includes only four reciprocating pistons and four corresponding cylinders. The engine 102 further includes a plurality of fuel injectors 108a-f capable of performing multiple fuel injection events with respect to one or more of the cylinders 106a-f per one or two revolutions of a crankshaft (not shown) of the engine 102.In the illustrated form, the injectors 108a-f receive fuel from a pressurized common rail 110 connected to a high-pressure fuel pump 112. The fuel pump 112 is further connected directly or indirectly to a fuel source via the fuel line 114. Although the fuel injector shown in . Fig. While the engine 102 illustrated in Figure 2 includes a high-pressure common rail fuel injection system, any device capable of delivering multiple fuel injection events with respect to one or more cylinders 106a-f per revolution (or per two revolutions) of the crankshaft of the engine 102 is contemplated in the present application. In certain embodiments, the system 100 includes an engine position sensor (not shown) that detects a current position of the crankshaft.

[0012] The system 100 further includes a processing subsystem 116 with a controller 118. The processing subsystem 116 may be constructed with controllers, modules, sensors, regulators, communication links, and other devices known in the art for performing the operations described herein. The controller 118 may be a single device or a distributed device, and the functions of the controller 118 may be performed by hardware or software. All instructions and information may be provided in alternative embodiments; some information may not be present in certain embodiments; and additional information may be present in certain embodiments. Information may be evaluated from sensor inputs, from data link communications, from parameters on a computer-readable storage medium, or from other information-gathering devices known in the art.

[0013] In certain embodiments, the controller 118 includes one or more modules configured to functionally carry out its operations. The present description including modules emphasizes the structural independence of the aspects of the controller 118 and illustrates a collection of operations and tasks of the controller 118. It is understood that other collections performing similar general operations are considered within the scope of the present application. Modules may be implemented in hardware and / or software on a computer-readable medium, and modules may be distributed across various hardware or software components. More detailed descriptions of certain embodiments of the controller operations are provided below with reference to the schematic representation of the Fig. 3.

[0014] The controller 118 is generally configured to operate the engine 102 in a standard operating mode 200 and a secondary mode 202 in which exhaust gas temperatures are elevated relative to the standard operating mode 200. The engine 102 may be operated in the secondary mode 202 to facilitate, among other things, the regeneration of one or more components of an aftertreatment system 904, such as desulfurizing a catalyst. Further details of the operation of the engine 102 in the secondary mode 202 are provided below. In particular, the controller 118 includes a system condition module 204 that evaluates a command to increase the exhaust gas temperature 206 and determines that the engine 102 should be operated in the secondary mode 202 rather than the standard mode 200.In one embodiment, the exhaust temperature increase command 206 is provided by a diagnostic or maintenance tool based on a determination that regeneration of one or more components of the aftertreatment system 904 is required. However, it is also contemplated that the exhaust temperature increase command 206 is generated by the system conditions module 204 or another module of the controller 118 in response to evaluating one or more of the commands or signals received by the controller 118.

[0015] To operate in secondary mode 202, controller 118 is generally configured to control the speed of engine 102 based on speed rather than fueling. Similarly, after system condition module 204 determines to controller 118 that engine 102 is to be operated in secondary mode 202, speed control module 208 provides a speed control command 210. Generally, speed control command 210 specifies that the speed of engine 102 during secondary mode 202 be above the normal idle speed of engine 102 during operation in standard operating mode 200. For example, in one embodiment, speed control command 210 specifies that engine 102 operate at greater than 1000 rpm in secondary mode 202. In a further embodiment, the speed control command 210 specifies that the motor 102 is operated in the secondary mode 202 in the range of 2000-2600 rpm.In yet another embodiment, the command to control speed specifies that the engine 102 operate in the range of 2200-2500 rpm in the secondary mode 202. Furthermore, although not previously discussed, it should be understood that the engine 102 is not operated under a load condition in the secondary mode 202. For example, in one non-limiting embodiment, the vehicle 902 may be removed from normal operation for maintenance when the engine 102 is operating in the secondary mode 202.

[0016] The controller 118 also includes a fuel control module 212 that provides fuel system commands 214. If the system control module 204 determines that the engine 102 is to be operated in the standard operating mode 200, the fuel control module 212 provides unmodified fuel system commands 214 according to the normal operation of the system 100. However, to operate the engine 102 in the secondary mode 202, the fuel control module 212 of the controller 118 is configured to provide a cylinder deactivation command as part of the fuel system commands 214. A first number of injectors 108a-f are responsive to the cylinder deactivation command to interrupt fuel injection to a first number of corresponding cylinders 106a-f such that each cylinder of the first number of cylinders 106a-f is deactivated and operates in a deactivation mode.With reference to the illustrated embodiment, it is conceivable that the first number of cylinders operated in the deactivation mode may include only one of the cylinders 106a-f and up to four cylinders 106a-f. In a particular embodiment of the illustrated embodiment, the first number of cylinders operated in the deactivation mode includes three of the cylinders 106a-f. However, further modifications are possible and conceivable. For example, in embodiments not shown in which the engine 102 includes only four cylinders, it is contemplated that only one or up to two of the four cylinders may be operated in the deactivation mode.

[0017] The fuel control module 212 of the controller 118 is further configured to provide a delayed fueling command as part of the fuel system commands 214 when the system control module 204 determines that the engine 102 should be operated in the secondary operating mode 202. A second number of injectors 108a-f are responsive to the delayed fueling command to implement a delayed fuel injection scheme for a second, remaining number of cylinders 106a-f operating in a combustion mode. Specifically, for the second number of cylinders 106a-f operating in the combustion mode, the second number of injectors 108a-f are responsive to the delayed fueling command to perform a main fuel injection event no earlier than 2 degrees before top dead center (TDC).

[0018] Depending on the characteristics of the fuel system, the terms fuel supply, fuel injection, and / or performing a fuel injection event at a particular crankshaft angle degree indicate that the fuel supply event or injection start begins at the particular crankshaft angle degree. For example, a supply after 3 degrees after TDC generally indicates an injection start after 3 degrees after TDC. Similarly, as in Fig. 4, the injection start 122 of the main fuel injection process 120 occurs at 3 degrees after TDC. However, it is understood that the illustration in Fig.4 is not limiting and that other times for the start of injection 122 of the main fuel injection event 120 are possible. For example, in one embodiment, the start of injection 122 of the main fuel injection event 120 takes place no earlier than 2 degrees before TDC. However, in another embodiment, the start of injection 122 of the main fuel injection event 120 takes place at or after 2 degrees before TDC. In another embodiment, the start of injection 122 of the main fuel injection event 120 is not earlier than TDC. In yet another embodiment, the start of injection 122 of the main fuel injection event 120 is not earlier than 3 degrees after TDC. In yet another embodiment, the start of injection 122 of the main fuel injection event 120 is in the range of 2 degrees before TDC and 8 degrees after TDC. In another embodiment, the start of injection 122 of the main fuel injection event 120 occurs between TDC and 8 degrees TDC.In yet another embodiment, the start of injection 122 of the main fuel injection event 120 is in the range of 3-8 degrees after TDC. In yet another embodiment, the start of injection 122 of the main fuel injection event 120 is in the range of 4-7 degrees after TDC. Other variants of the timing of the main fuel injection event 120 are also conceivable. Furthermore, it is understood that the main fuel injection event 120 may include one or more combustion fuel quantities for the main injection.

[0019] The second number of injectors 108a-f further responds to the delayed fueling command to perform a post-fuel injection event 124 following the main fuel injection event 120. In the Fig.In the non-limiting embodiment shown in FIG. 4, the injection start 126 of the post-fuel injection event 124 occurs with a delay 128 in the range of 14-16 degrees after the end of injection of the main fuel injection event 120. In another embodiment, the injection start 126 of the post-fuel injection event 124 is in the range of 13-17 degrees after the end of injection of the main fuel injection event 120. In yet another embodiment, the injection start 122 of the post-fuel injection event 124 is in the range of 13-18 degrees after the end of injection of the main fuel injection event 120. Still other variations of the timing of the post-fuel injection event 124 are conceivable. Furthermore, it is understood that the post-fuel injection event 124 may include one or more combustion fuel quantities for the post-injection.

[0020] Although not previously discussed, when operating the engine 102 in the standard operating mode 200 includes a pilot fuel injection event, the fuel control module 212 of the controller 118 is further configured to provide a pilot fuel injection cancel command 214 as part of the fuel system commands 214 for operating the engine in the secondary operating mode 202. The second number of injectors 108a-f are responsive to the pilot fuel injection cancel command to deactivate the pilot fuel injection event. Furthermore, it is understood that the amounts of fuel injected during the main fuel injection event 120 and the post fuel injection event 124 result in a total amount of fuel injected during a respective combustion cycle.In an embodiment in which the cylinders 106a-f have a volume of 1.15 liters, the total amount of fuel injected per cylinder is in the range of 50-80 mg / stroke, or 55-75 mg / stroke, or 70-80 mg / stroke, to name a few non-limiting possibilities. It should be understood that the total amount of fuel injected per cylinder during each stroke will change accordingly in embodiments in which the cylinders 106a-f have a different volume. Further, in one embodiment, the amount of fuel injected during the main fuel injection event 120 is in the range of 70-90% of the total amount of fuel injected. In another embodiment, the amount of fuel injected during the main fuel injection event 120 is in the range of 75-85%, 70-80%, or 80-90% of the total amount of fuel injected, to name a few examples.

[0021] The fuel control module 212 of the controller 118 is further configured to provide a rail pressure reduction command as part of the fuel system commands 214 for operating the engine 102 in the secondary mode 202. A high-pressure fuel pump 112 responds to the rail pressure reduction command to provide a rail pressure below 1000 bar. In a particular embodiment, the rail pressure is in the range of 300-700 bar. In yet another embodiment, the rail pressure is in the range of 350-600 bar. Alternative values for the rail pressure during operation of the engine 102 in the secondary mode 202 are contemplated.

[0022] With particular reference to Fig. 5, it is understood that the controller 118 may also be configured to communicate with one or more components of the aftertreatment system 904. In particular, in the schematic representation of the Fig.5 the aftertreatment system 904 comprises a particulate filter 906, a decomposition pipe or line 908, a NO x -reduction catalyst 910, such as an SCR system, and an ammonia oxidation catalyst 912. The aftertreatment system 904 also includes a reductant injector or reductant doser 914 connected to the decomposition line 908. Further, it should be understood that the aftertreatment system 904 may include one or more components in addition to or in place of the illustrated components, including, by way of non-limiting example, a diesel oxidation catalyst, and that the components may be provided in one or more arrangements not shown in Fig. 5 are shown.

[0023] The controller 118 also includes an aftertreatment control module 216 configured to provide one or more aftertreatment system commands 218. During operation of the engine 102 in the standard operating mode 200, the aftertreatment control module 216 is configured to provide dosing commands to the doser 914 at appropriate times as part of the aftertreatment system commands 218. The doser 914 is responsive to the dosing commands to inject a reductant (e.g., urea, a hydrocarbon, and / or ammonia) into the exhaust path 903 upstream of the NO x-reduction catalyst 910. However, in one embodiment of operation of the engine 102 in the secondary mode 202, the aftertreatment control module 216 is further configured to provide a dosing cancellation command to the controller 118 as part of the aftertreatment system commands 218. In this embodiment, the doser 914 is deactivated in response to the dosing cancellation command when the engine 102 is operated in the secondary mode 202. However, it should be understood that embodiments in which the doser 914 is not deactivated when the engine 102 is operated in the secondary mode 202 are also contemplated.

[0024] The system 100 may also include a number of sensors, including one or more temperature sensors, located upstream of the aftertreatment system 904, between the particulate filter 906 and the NO xreduction catalyst 910 and / or downstream of the aftertreatment system 904. In the illustrated embodiment, the system 100 includes a NO x -Sensor 916, which is located downstream of the NO x reduction catalyst 910. The sensor 916 is generally configured to detect NO x -values in exhaust path 903 downstream of the NO x reduction catalyst 910 and provides a corresponding signal to the controller 118 as part of the exhaust conditions 220. In one embodiment, the controller 118 is configured to determine whether the signals received from the sensor 916 indicate NO x values that exceed a predetermined threshold and, if so, generate a command for an indicator light 222 to provide an indication to a user of the engine 102 that the current NO xvalues are unacceptable. The controller 118 may also be configured to perform additional functions in response to receiving the signals from the sensor 916. The system 100 may also include one or more NO x -Sensors located upstream of the NO x-reduction catalyst 910 and / or downstream of the ammonia oxidation catalyst 912. The selection and location of sensors are not limiting, and a variety of sensor arrangements are conceivable. However, the system 100 may also include one or more of the following components: a turbocharger, an EGR system, or an injector upstream of the particulate filter 906 that injects hydrocarbons to help regenerate the particulate filter 906.In embodiments where a hydrocarbon injector is disposed upstream of the particulate filter 906, the controller 118 may be further configured to provide a command to turn off the hydrocarbon injector such that the hydrocarbon injector is deactivated when the engine 102 is operated in the secondary mode 202, although embodiments where the hydrocarbon injector is not deactivated are also contemplated.

[0025] While not intended to be bound by any particular theory, it is believed that the increases in exhaust gas temperature achieved by operating the engine 102 in the secondary mode 202 are generated in whole or in part by facilitating the oxidation of hot, fuel-rich exhaust gases downstream of the engine 102. More specifically, operating the engine 102 with the first number of cylinders 106a-f in the shutdown mode generally produces higher operating temperatures, thereby, among other things, providing air pumped through the first number of cylinders 106a-f at a higher temperature relative to the standard operating mode in which each of the cylinders 106a-f is operated in the combustion mode. Similarly, the exhaust gases expelled from the second number of cylinders 106a-f operating in the combustion mode also generally have a higher temperature compared to the standard operating mode.Additionally, the delayed fueling pattern and reduced rail pressure discussed above are believed to result in an excess of unburned hydrocarbons (HCs) in the exhaust gas emitted from the second set of cylinders 106a-f. When the hot exhaust gases containing excess HCs combine with or impinge upon hot air pumped through the first set of cylinders 106a-f, at least a portion of the excess HCs is believed to be oxidized to generate additional heat in the exhaust path 903 and increase the temperature of the exhaust gas.

[0026] Although not discussed above, it is understood that the oxidation of at least a portion of the excess HC occurs independently of catalytic influences. In other words, even in embodiments such as the illustrated embodiment in which no diesel oxidation catalyst is present, oxidation of the exhaust gases containing excess HC occurs downstream of the engine 102. Furthermore, in embodiments in which a diesel oxidation catalyst is present, it is conceivable that the oxidation of exhaust gases containing excess HC occurs upstream of the diesel oxidation catalyst, so that the diesel oxidation catalyst does not promote or initiate the oxidation. Nevertheless, embodiments in which a diesel oxidation catalyst is present and promotes the oxidation of the exhaust gases containing excess HC are also conceivable.

[0027] As mentioned above, in one embodiment, the system 100 may be used to raise the exhaust gas to a temperature effective for regenerating one or more components of the aftertreatment system 904. In particular, in one non-limiting embodiment, the system 100 is used to desulfurize the NOx reduction catalyst 910 when in the form of an SCR system. Further details regarding an exemplary procedure 300 for using the system 100 in this manner will now be described in connection with the Fig. 6 is explained in the schematic flow diagram shown.

[0028] The procedure 300 includes an operation 302 for determining whether desulfurization of the SCR system is required. The determination that desulfurization of the SCR system is required may be based on events received and analyzed by the controller 118, such as receiving various signals indicative of exhaust gas parameters from one or more downstream sensors, whether a predetermined period of time or use of the engine 102 has occurred, or by receiving a corresponding command from a diagnostic service tool. For example, in one embodiment, the diagnostic service tool may be placed in communication with the controller 118 by a service technician, and the service technician may provide an indication or command, based on the diagnostic service tool, that desulfurization of the SCR system is necessary.In other embodiments, the diagnostic service tool may provide an indication or command to the controller 118 that desulfurization of the SCR system is necessary, with little or no intervention from the service technician. In response to determining that desulfurization of the SCR system is not necessary, the procedure 300 includes an operation 304 to perform or maintain operation of the engine 102 in the standard operating mode 200.

[0029] However, in response to determining that desulfurization of the SCR system is required, such as by receiving a desulfurization command from the diagnostic service tool, the method 300 may include an act 306 of performing operation of the engine 102 in the standard operating mode 200 until a predetermined engine coolant temperature is reached. In one non-limiting embodiment, the predetermined engine coolant temperature is 75°C, although it is understood that other alternatives are possible. Once the predetermined engine coolant temperature is reached, the method 300 includes an act 308 of performing operation of the engine 102 in the secondary operating mode 202 as described above. In act 308, the speed of the engine 102 may be slowly increased until it reaches a desired operating speed, such as that described above.Once the desired operating speed is reached, the remaining conditions of secondary operating mode 202 are executed in operation 308. Operation of engine 102 in secondary operating mode 202 may continue until a desired exhaust gas temperature is reached for a time period necessary for desulfurization of the SCR system. In one embodiment, the desired temperature is at least 300°C. In another embodiment, the desired temperature is in the range of 300-550°C. However, it is understood that other values for the desired temperature are possible and conceivable. Furthermore, in one embodiment, the period of time for the exhaust gas to be at the desired temperature is at least 60 minutes. In another embodiment, the period of time for the exhaust gas to be at the desired temperature is in the range of 30-180 minutes. However, it is understood that other values for the desired period of time are conceivable and conceivable.

[0030] The procedure 300 also includes an operation 310 to determine whether the conditions for desulfurization of the SCR system are met. For example, in one embodiment, the operation 310 may determine whether the exhaust gas has been at the desired temperature for a period of time sufficient to desulfurize the SCR system. If it is determined in operation 310 that the conditions for desulfurization of the SCR system have not been met, the procedure 300 proceeds to operation 308, in which operation of the engine 102 is performed in the secondary mode 202. If it is determined in operation 310 that the conditions for desulfurization of the SCR system have been met, the procedure 300 proceeds to an operation 312, in which the engine 102 is operated in the standard operating mode 200 for a period of time sufficient to adequately cool the engine before shutdown. EXAMPLES

[0031] The following examples are provided for illustrative purposes and should not be construed as limiting the invention disclosed in this document to the embodiments disclosed in these examples.

[0032] The experimental data for Examples I-VI presented in Table I below relate to experiments conducted in the context of engine operation to increase exhaust gas temperatures. Specifically, the experiments related to increasing the exhaust temperatures of a six-cylinder diesel engine to a level high enough to facilitate desulfurization of a vanadium pentoxide catalyst of an SCR system. Generally, desulfurization of the vanadium pentoxide catalyst can occur at exhaust gas temperatures of at least 300°C. In addition, while not necessary, it is generally desirable that the HCs in the exhaust gas entering the SCR be less than 1000 ppm. TABLE I Example No. I II III IV V VI Engine speed (rpm) 2262 2262 248 7 2487 237 9 2379 Start of main injection (degrees after TDC) 6,8 6,8 4,37 4,37 6,09 6,09 Separation between the end of the main injection and the start of the post-injection (degrees) 14,6 14,6 15,5 15,5 15,9 15,9 Groin pressure (bar) 560 560 589 589 391 391 Number of cylinders in combustion mode 3 3 3 3 3 3 Total fuel supply (mg / stroke) 73 73 58 58 73 73 Fuel supply (mg / stroke) 10,7 10,7 14,3 14,3 11,2 11,2 Catalyst inlet temperature (°C) 341 338 283 303 404 397 HCs at catalyst inlet (ppm) 551 581 524 260 249 121

[0033] The experimental data for Example VII presented in Table II below relate to experiments conducted in conjunction with engine operation to increase exhaust temperatures. Specifically, the experiments involved increasing the exhaust temperatures of a four-cylinder diesel engine to a level high enough to facilitate desulfurization of a vanadium pentoxide catalyst of an SCR system. Generally, desulfurization of the vanadium pentoxide catalyst can occur at exhaust temperatures of at least 300°C. In addition, while not necessary, it is generally desirable that the HCs in the exhaust entering the SCR be less than 1000 ppm. TABLE II Example No. VII Engine speed (rpm) 2379 Start of main injection (degrees after TDC) 6,09 Separation between the end of the main injection and the start of the post-injection (degrees) 15,9 Groin pressure (bar) 391 Number of cylinders in combustion mode 2 Total fuel supply (mg / stroke) 73 Fuel supply (mg / stroke) 11,2 Catalyst inlet temperature (°C) 283 HCs at catalyst inlet (ppm) 350

[0034] As can be seen from the figures and text presented above, a number of different embodiments according to the present invention are conceivable.

[0035] One embodiment is a method that includes operating an internal combustion engine above idle speed, including a plurality of cylinders and an exhaust path. Operating also includes deactivating a first group of cylinders while maintaining a second group of cylinders in a combustion mode; injecting a first amount of fuel into each of the cylinders of the second group of cylinders no earlier than 2 degrees before top dead center (TDC); directing fuel-rich exhaust from the second group of cylinders into the exhaust path; and oxidizing at least a portion of the fuel-rich exhaust in the exhaust path independent of any catalytic influence.

[0036] In one aspect of this embodiment, operating is performed while the internal combustion engine is in the unloaded state. In another aspect of this embodiment, the engine further includes at least one aftertreatment component, and oxidizing occurs upstream of the at least one aftertreatment component. In one aspect of this embodiment, the at least one aftertreatment component is a selective reduction catalyst (SCR) system, and operating includes delivering exhaust gases into the exhaust path at a temperature effective to facilitate desulfurization of the SCR system. In another aspect, the temperature is in the range of 300-550°C.

[0037] In yet another aspect of this embodiment, the fuel is diesel fuel. In yet another aspect, the method further includes, after the first amount of fuel, injecting a second amount of fuel into each cylinder of the second cylinder group. In one aspect of this embodiment, the first and second amounts of fuel define a total amount of injected fuel, and the first amount of fuel is in the range of 70-90% of the total amount of injected fuel. In another aspect, the total amount of injected fuel is in the range of 50-80 mg / stroke. In another aspect of this embodiment, injecting the first amount of fuel into each cylinder of the second cylinder group begins in the range of 2 degrees before TDC to 8 degrees after TDC.In one aspect of this embodiment, the method further includes injecting a second amount of fuel into each cylinder of the second cylinder group, and injecting the second amount of fuel begins in the range of 13-17 degrees after the end of injection of the first amount.

[0038] In a further embodiment of this embodiment, the injection of the first quantity of fuel into each cylinder of the second cylinder group is carried out at a rail pressure of less than 1000 bar. In a particular aspect of this embodiment, the rail pressure is in the range of 300-700 bar. In a further aspect of this embodiment, the rail pressure is in the range of 350-600 bar. In a further embodiment of this embodiment, the method further includes deactivating a doser arranged in the exhaust path. In yet another embodiment of this embodiment, the first group of cylinders includes at least two of the plurality of cylinders. In one aspect of this embodiment, the engine has six cylinders and the group of cylinders includes three of the six cylinders.

[0039] In yet another aspect of this embodiment, operating the engine is performed at an engine speed in the range of 2100-2600 rpm. In yet another aspect of this embodiment, the method further includes accepting a regeneration command, and operating is performed in response to accepting the regeneration command. In one aspect of this embodiment, injecting the first amount of fuel into each of the cylinders of the second cylinder group is performed at a rail pressure of less than 1000 bar.

[0040] In another embodiment, a method includes determining that a selective reduction catalyst (SCR) system requires desulfurization. In response to the determining, the method also includes operating a diesel engine connected to the SCR system via an exhaust path and engaging a plurality of cylinders in a desulfurization mode, including: operating a first number of cylinders of the diesel engine in a combustion mode and a second number of cylinders of the diesel engine in a shutdown mode; injecting a main amount of fuel into each of the cylinders operating in the combustion mode no earlier than 2 degrees before top dead center (TDC); and injecting a post-fuel amount into each of the cylinders operating in the combustion mode after the main injection of fuel.

[0041] In one embodiment of this embodiment, operating the engine in desulfurization mode is performed above idle speed and in the unloaded state of the engine. In another embodiment, the method further includes, prior to operating the engine in desulfurization mode, operating the engine in a standard operating mode until coolant temperatures have exceeded 75°C. In yet another embodiment, operating the engine in desulfurization mode further includes canceling a pilot injection of fuel and deactivating a doser disposed in the exhaust path. In yet another embodiment, the main and post-fuel amounts are equal to a total fuel amount during the combustion cycle, and the main fuel amount is in the range of 70-90% of the total fuel amount.In a further embodiment, the injection of the main fuel quantity into each of the cylinders operating in the combustion mode begins in the range of 2 degrees before TDC to 8 degrees after TDC, and the injection of the post-fuel quantity into each of the cylinders operating in the combustion mode begins in the range of 14-17 degrees after the end of the injection of the main fuel quantity.

[0042] In yet another aspect of this embodiment, the method further includes, prior to operating the engine in desulfurization mode, operating the engine in a standard operating mode and reducing the rail pressure when the engine is operated in desulfurization mode relative to the standard operating mode. In yet another aspect, injecting the main and post-fuel quantities into each of the cylinders operating in combustion mode is performed at a rail pressure in the range of 300-700 bar. In yet another aspect, the method further includes, in response to the determining, utilizing a service tool to instruct a control module of the diesel engine to transition from a standard operating mode to the desulfurization mode.

[0043] In yet another embodiment, a system includes an internal combustion engine including a plurality of cylinders and operable to generate an exhaust stream, and a selective reduction catalyst (SCR) system configured to treat the exhaust stream. The system also includes a controller configured to provide a cylinder deactivation command and a delayed fueling command while the engine is operating above idle speed and in an unloaded state after determining that desulfurization of the SCR system is required.

[0044] In one aspect of this embodiment, the system further includes a fuel injection system responsive to the cylinder deactivation command to deactivate fuel injection to a first number of the plurality of cylinders and responsive to the delayed fueling command to inject a main injection of fuel into each of a second number of the plurality of cylinders no earlier than 2 degrees before top dead center (TDC). In one aspect of this embodiment, the fuel injection system is further responsive to the delayed fueling command to inject a post injection of fuel into each of the second number of cylinders. In another aspect, the main injection of fuel begins in the range of 2 degrees before TDC to 8 degrees after TDC, and the post injection of fuel begins in the range of 14-17 degrees after the end of the injection of the main injection of fuel.

[0045] In a further embodiment of this embodiment, the controller is further configured to provide a command to cancel pilot injection and a command to cancel metering after determining that desulfurization of the SCR system is required. In yet another embodiment of this embodiment, the controller is further configured to provide a command to reduce rail pressure after determining that desulfurization of the SCR system is required. In one aspect of this embodiment, the system further includes a fuel injection system, and the fuel injection system is responsive to the command to reduce rail pressure to reduce the rail pressure to a value in the range of 300-700 bar.

[0046] In another embodiment, a system includes an internal combustion engine including a plurality of cylinders and a controller configured to operate the engine in a standard operating mode and a regeneration mode, wherein a first number of the cylinders are deactivated, a delayed fueling scheme is applied in conjunction with a second number of cylinders, and oxidation of at least a portion of fuel-rich exhaust gases occurs downstream of the engine and independent of any catalytic influence.

[0047] In one aspect of this embodiment, the system further includes a service tool operable to communicate with the controller and, upon determining that desulfurization of a selective reduction catalyst (SCR) system is desirable, instruct the controller to begin operation in regeneration mode. In one aspect of this embodiment, the delayed fueling scheme includes injecting a main injection of fuel no earlier than 2 degrees before top dead center (TDC) and a post-injection of fuel following the main injection of fuel. In another embodiment, the engine is operated above idle and in an unloaded state during regeneration mode. In yet another embodiment, the oxidizer provides an exhaust stream having a temperature in the range of 300-550°C.In a further embodiment, the delayed fuel supply scheme includes a bar pressure in the range of 300-700 bar.

[0048] Although the invention has been particularly illustrated and described in the drawings and the foregoing description, it is to be considered as illustrative and not restrictive, it being understood that only the preferred embodiments have been shown and described, and that all changes and modifications which come within the spirit of the invention are intended to be protected. It is to be understood that although the use of words such as preferable, preferred, more preferred or exemplary used in the foregoing description indicates that the feature so described may be particularly desirable or characteristic, it is nevertheless not absolutely necessary, and embodiments without it may be contemplated as being within the scope of the invention, the scope being defined by the following claims.When reading the claims, it is intended that the use of words such as "a," "an," "at least one," or "at least a part" is not intended to limit the claim to only one subject matter unless expressly stated otherwise in the claim. When terms such as "at least a part" and / or "a part" are used, the subject matter may include part and / or all of the subject matter unless expressly stated otherwise.

Claims

[1] Method comprising: Operating a diesel engine (102) having a plurality of cylinders (106a-f) connected via an exhaust path (903) to a selective catalytic reduction (SCR) system (910) in a standard operating mode (200); Determining that the selective reduction catalyst (SCR) system (910) requires desulfurization; and in response to determining: Operating the diesel engine (102) in a desulfurization mode (202) which includes: Operating a first number of cylinders (106a-f) of the diesel engine (102) in a combustion mode and a second number of cylinders (106a-f) of the diesel engine (102) in a shutdown mode; Reducing a bar pressure in the desulfurization mode (202) relative to the standard operating mode (200); Injecting a first main amount of fuel into each of the cylinders (106a-f) operating in the combustion mode no earlier than 2 degrees before top dead center (TDC); and Injecting a first post-fuel quantity into each of the cylinders (106a-f) operating in the combustion mode after the main injection of fuel. [2] A method according to claim 1, wherein the operation of the engine in the desulfurization mode is carried out above the idle speed and in the unloaded state of the engine. [3] The method of claim 1, further comprising, prior to operating the engine in the desulfurization mode, operating the engine in a standard operating mode until the coolant temperatures exceed 75°C. [4] The method of claim 1, wherein operating the engine in the desulfurization mode further includes canceling a pilot injection of fuel and deactivating a doser disposed in the exhaust path. [5] A method according to claim 1, wherein the main and post-fuel quantities are equal to a total fuel quantity injected during the combustion cycle, the main fuel quantity being in the range of 70-90% of the total fuel quantity. [6] A method according to claim 1, wherein the injection of the main fuel quantity into each of the cylinders operating in the combustion mode begins in the range of 2 degrees before TDC to 8 degrees after TDC, and the injection of the post-fuel quantity into each of the cylinders operating in the combustion mode begins in the range of 14-17 degrees after the end of the injection of the main fuel quantity. [7] A method according to claim 1, wherein the injection of the main and post-fuel quantities into each of the cylinders (106a-f) operating in combustion mode is carried out at a rail pressure in the range of 300-700 bar. [8] The method of claim 1, further comprising, in response to the determining, utilizing a maintenance tool to instruct a control module of the diesel engine (102) to transition from a standard operating mode (200) to the desulfurization mode (202). [9] System (100), with: an internal combustion engine (102) including a plurality of cylinders (106a-f) and operable to generate an exhaust gas stream (903); a selective reduction catalyst (SCR) system (910) configured to treat the exhaust stream (903); and a controller (118) configured to provide, in response to a determination that desulfurization of the SCR system (910) is required, a command to deactivate cylinders (106a-f) and a command to delay fueling while the engine (102) is operating above idle speed and in an unloaded state, wherein the controller (118) is further configured to provide a command to reduce the rail pressure in response to determining that desulfurization of the SCR system (910) is required. [10] The system (100) of claim 9, further comprising a fuel injection system responsive to the cylinder deactivation command (106a-f) to deactivate fuel injection to a first number of the plurality of cylinders (106a-f) and responsive to the delayed fueling command to inject a main injection of fuel into each of a second number of the plurality of cylinders (106a-f) no earlier than 2 degrees before top dead center (TDC). [11] The system (100) of claim 10, wherein the fuel injection system is further responsive to the delayed fueling command to inject a post-injection of fuel into each of the cylinders (106a-f) of the second number of cylinders (106a-f). [12] The system (100) of claim 11, wherein the main injection of fuel begins in the range of 2 degrees before TDC to 8 degrees after TDC, and the post injection of fuel begins in the range of 14-17 degrees after the end of the injection of the main injection of fuel. [13] The system of claim 9, wherein the controller (118) is further configured to provide a pre-injection cancel command and a dosing cancel command in response to determining that desulfurization of the SCR system (910) is required. [14] The system of claim 9, further comprising a fuel injection system, wherein the fuel injection system is responsive to the rail pressure reduction command to reduce the rail pressure to a value of 300-700 bar.

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