Low-temperature diesel oil after-treatment regeneration strategy

Abstract

A method of aftertreatment regeneration includes routing exhaust gas from a diesel engine through an exhaust system, and initiating nitrogen dioxide based aftertreatment regeneration of a diesel particulate filter (DPF) by at least partially deactivating a first DEF injector and an upstream selective catalytic reducer (SCR); increasing the level of nitric oxide within the exhaust gas from the engine; establishing and maintaining a target exhaust gas temperature at an intake port of the DPF by actively controlling combustion characteristics of the engine; a diesel oxidation catalyst (DOC) is used for converting NO in the waste gas entering the DOC into NO2; and converting the solid carbon-based particulate matter accumulated within the DPF into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidizing agent.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a control strategy for aftertreatment regeneration of an internal combustion engine exhaust system. BACKGROUND

[0002] Diesel oxidation catalysts (DOC), diesel particulate filters (DPF), lean NOx traps (LNT), and selective catalytic reduction (SCR) diesel exhaust system aftertreatment devices have become indispensable. O2-based regeneration of DPFs operates at extremely high temperatures, causing premature "aging" of the DPF components and SCR components and other components of the exhaust system due to thermal degradation.

[0003] Accordingly, there is a need for an improved system and method for providing aftertreatment regeneration of DPF and SCR for a diesel exhaust system, including primarily using NO2-based aftertreatment regeneration of the DPF, sometimes using O2-based short-term aftertreatment regeneration of the DPF when NO2-based aftertreatment regeneration is ineffective for soot abatement within the DPF, and sometimes using SCR desulfurization when O2-based aftertreatment regeneration has not been initiated recently. SUMMARY

[0004] According to aspects of the present disclosure, a method of aftertreatment regeneration in a diesel vehicle includes routing exhaust gas from a diesel engine through an exhaust system within the vehicle, the exhaust system including: a diesel oxidation catalyst (DOC) immediately downstream of the diesel engine; an upstream selective catalytic reduction (SCR) unit downstream of the DOC; a first diesel exhaust fluid (DEF) injector positioned between the DOC and the first SCR and adapted to inject DEF into the exhaust gas; a diesel particulate filter (DPF) downstream of the first SCR and adapted to collect particulate material from exhaust gas passing therethrough; and an exhaust system controller in communication with an engine controller, a plurality of sensors within the exhaust system, and the first DEF injector; and initiating a nitrogen dioxide (NO2)-based aftertreatment regeneration of the DPF by: deactivating, at least in part, the first DEF injector and the upstream SCR using the exhaust system controller such that NO2 is allowed to pass through the upstream SCR; increasing, using the exhaust system controller via communication with the engine controller, a level of nitric oxide (NO) within the exhaust gas from the engine; actively controlling, using the exhaust system controller via communication with the engine controller, combustion characteristics of the engine to establish and maintain a target exhaust gas temperature (EGT) at a DPF intake (DPF intake temperature) and a target EGT at a DOC intake (DOC intake temperature); converting, using the DOC, the NO within the exhaust gas entering the DOC to NO2; and converting, using the NO2 as an oxidizer, solid carbon-based particulate matter accumulated within the DPF to gaseous carbon dioxide (CO2) and NO.

[0005] According to another aspect, increasing, using the exhaust system controller via communication with the engine controller, a level of NO within the exhaust gas from the engine further includes selectively adjusting, using the exhaust system controller via communication with the engine controller, utilization of an exhaust gas recirculation (EGR) unit, injection timing, injection quantity, and fresh air quantity within the engine.

[0006] According to another aspect, actively controlling, using the exhaust system controller via communication with the engine controller, combustion characteristics of the engine to establish and maintain a target exhaust gas temperature (EGT) at a DPF intake (DPF intake temperature) and a target EGT at a DOC intake (DOC intake temperature) further includes: calculating, based on the target DPF intake temperature and the target DOC intake temperature and thermodynamic characteristics of the exhaust system, a target EGT of the exhaust gas from the engine; and selectively utilizing, using the exhaust system controller via communication with the engine controller, late injection and post injection within the engine to establish and maintain the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC.

[0007] According to another aspect, establishing and maintaining the target exhaust gas temperature (EGT) at the DPF inlet also includes establishing and maintaining the DPF inlet temperature between approximately 300 degrees Celsius and approximately 500 degrees Celsius.

[0008] According to another aspect, using DOC to convert NO in the exhaust gas entering DOC into NO2 also includes: using platinum as a catalyst to convert NO in the exhaust gas entering DOC into NO2.

[0009] According to another aspect, using the exhaust system controller to at least partially disable the first DEF injector and the upstream SCR, allowing NO2 to pass through the upstream SCR, also includes: establishing and maintaining a target DPF inlet temperature and a target DOC inlet temperature before the NO level in the exhaust gas from the engine increases, and using the DOC to convert NO in the exhaust gas entering the DOC into NO2; using the exhaust system controller to at least partially disable the first DEF injector; and allowing residual DEF in the upstream SCR to dissipate to an acceptable level.

[0010] According to another aspect, converting solid carbon-based particulate matter accumulated within a DPF into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant further includes: exposing the carbon particulate matter within the DPF to at least one of a platinum and a palladium catalyst, wherein the carbon particulate matter and NO2 react to form CO2 and NO, and further wherein NO reacts with oxygen (O2) to form NO2, wherein the newly formed NO2 further reacts with the carbon particulate matter.

[0011] According to another aspect, the method further includes: monitoring the level of carbon particulate matter in the DPF using an exhaust system controller via communication with a delta pressure sensor and the exhaust gas temperature in the DPF; and initiating a short-term O2-based aftertreatment regeneration of the DPF when one of the following occurs: the particulate matter level in the DPF increases during NO2-based aftertreatment regeneration; or the rate of decrease in the particulate matter level in the DPF is less than a predetermined rate during NO2-based aftertreatment regeneration.

[0012] According to another aspect, initiating short-term O2-based aftertreatment regeneration of the DPF also includes: selectively adjusting the utilization of the EGR unit, injection timing, injection quantity, and fresh air quantity within the engine by means of an exhaust system controller communicating with the engine controller, thereby controlling the O2 level in the exhaust gas from the engine through the exhaust system controller communicating with the engine controller, to manage the O2 level in the exhaust gas at the DPF inlet; establishing and maintaining a desired EGT between approximately 500 degrees Celsius and 650 degrees Celsius at the DPF inlet in the following manner: based on the desired EGT at the DPF inlet. The thermodynamic characteristics of the exhaust system are used to calculate the target EGT of exhaust gas from the engine and the target EGT of exhaust gas from the DOC; and to actively control the combustion characteristics of the engine by using the exhaust system controller via communication with the engine controller, and to selectively utilize delayed injection and post-injection within the engine by using the exhaust system controller via communication with the engine controller, in order to establish and maintain the target EGT of exhaust gas from the engine and the target EGT of exhaust gas from the DOC; and to convert solid carbon-based particulate matter accumulated in the DPF into gaseous CO2 by using O2 as an oxidant.

[0013] According to another approach, the method also includes initiating short-term SCR desulfurization within the upstream SCR and desorbing sulfur oxides SO₂. x Short-term SCR desulfurization includes: establishing and maintaining a target desorption EGT at the intake of the upstream SCR by: calculating the target EGT of exhaust gas from the engine and the target EGT of exhaust gas from the DOC based on the target desorption EGT and the thermodynamic characteristics of the exhaust system; actively controlling the combustion characteristics of the engine by using the exhaust system controller to communicate with the engine controller, and selectively utilizing delayed injection and post-injection in the engine by using the exhaust system controller to communicate with the engine controller, in order to establish and maintain the target EGT of exhaust gas from the engine and the target EGT of exhaust gas from the DOC.

[0014] According to several aspects of this disclosure, an exhaust system for a vehicle having a diesel engine includes: a diesel oxidation catalyst (DOC) located downstream of the diesel engine; an upstream selective catalytic reduction (SCR) unit located downstream of the DOC; a first diesel exhaust fluid (DEF) injector positioned between the DOC and the first SCR and adapted to inject DEF into the exhaust gas; a diesel particulate filter (DPF) located downstream of the first SCR and adapted to collect particulate material from the exhaust gas passing through it; and an exhaust system controller communicating with an engine controller, a plurality of sensors within the exhaust system, and the first DEF injector; and wherein the exhaust system controller is adapted to activate a second... A nitrogen oxide (NO2)-based aftertreatment regeneration method, wherein the exhaust system controller is adapted to: at least partially disable the first DEF injector and the upstream SCR, thereby allowing NO2 to pass through the upstream SCR; increase the level of nitrogen oxide (NO) in the exhaust gas from the engine via communication with the engine controller; and actively control the combustion characteristics of the engine via communication with the engine controller to establish and maintain a target exhaust gas temperature (EGT) at the DPF inlet and a target EGT at the DOC inlet; wherein the DOC is adapted to: convert NO in the exhaust gas entering the DOC into NO2, and convert solid carbon-based particulate matter accumulated in the DPF into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant.

[0015] On the other hand, in order to increase the level of NO in the exhaust gas from the engine, the exhaust system controller is also adapted to selectively adjust the utilization of the exhaust gas recirculation (EGR) unit, injection timing, injection quantity, and fresh air quantity within the engine via communication with the engine controller.

[0016] According to another aspect, in order to establish and maintain the target exhaust gas temperature (EGT) at the DPF inlet and the target EGT at the DOC inlet, the exhaust system controller is also adapted to calculate the target EGT of the exhaust gas from the engine based on the target DPF inlet temperature, the target DOC inlet temperature and the thermodynamic characteristics of the exhaust system; and to establish and maintain the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC by selectively utilizing delayed injection and after-injection within the engine via communication with the engine controller, wherein the target EGT at the DPF inlet is between approximately 300 degrees Celsius and approximately 500 degrees Celsius.

[0017] According to another aspect, DOC includes a platinum catalyst and is adapted to convert NO in the exhaust gas entering the DOC into NO2.

[0018] According to another aspect, in order to at least partially disable the first DEF injector and the upstream SCR, so that NO2 is allowed to pass through the upstream SCR, the exhaust system controller is also adapted to: establish and maintain a target DPF inlet temperature and a target DOC inlet temperature before the NO level in the exhaust gas from the engine increases, and use the DOC to convert NO in the exhaust gas entering the DOC into NO2; at least partially disable the first DEF injector; and allow residual DEF in the upstream SCR to dissipate.

[0019] According to another aspect, the DPF includes at least one of a platinum and a palladium catalyst, wherein when carbon particles within the DPF are exposed to at least one of the platinum and palladium catalysts, the carbon particles react with NO2 to form CO2 and NO, and NO reacts with oxygen (O2) to form NO2, wherein the newly formed NO2 further reacts with the carbon particles.

[0020] According to another aspect, the exhaust system controller is also adapted to monitor the level of carbon particulate matter in the DPF via inputs from a delta pressure sensor and a temperature sensor within the system; and to initiate short-term O2-based aftertreatment regeneration of the DPF when one of the following occurs: during NO2-based aftertreatment regeneration, the particulate matter level in the DPF increases; or during NO2-based aftertreatment regeneration, the rate of decrease of the particulate matter level in the DPF is less than a predetermined rate.

[0021] According to another aspect, when short-term O2-based aftertreatment regeneration of the DPF is initiated, the exhaust system controller is also adapted to: manage the O2 level in the exhaust gas at the DPF intake by selectively adjusting the utilization of the EGR unit, injection timing, injection quantity, and fresh air quantity within the engine, thereby controlling the O2 level in the exhaust gas from the engine via communication with the engine controller; calculate the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC based on the desired EGT between approximately 500 and 650 degrees Celsius at the DPF intake and the thermodynamic characteristics of the exhaust system; and actively control the combustion characteristics of the engine by communicating with the engine controller and selectively utilizing delayed injection and post-injection within the engine to establish and maintain the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC; and wherein, by using O2 as an oxidant, solid carbon-based particulate matter accumulated in the DPF is converted into gaseous CO2.

[0022] On the other hand, the exhaust system controller is also adapted to initiate short-term SCR desulfurization for desorbing sulfur oxides SO₂ from the upstream SCR. xThe exhaust system controller is adapted to: calculate the target EGT of exhaust gas from the engine and the target EGT of exhaust gas from the DOC based on the target desorption EGT at the upstream SCR intake and the thermodynamic characteristics of the exhaust system; and to actively control the combustion characteristics of the engine and selectively utilize delayed injection and post-injection within the engine by communicating with the engine controller in order to establish and maintain the target desorption EGT at the upstream SCR intake.

[0023] Further areas of application will become apparent from the description provided herein. It should be understood that these descriptions and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0024] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way.

[0025] Figure 1 These are schematic diagrams of a system according to exemplary embodiments of the present disclosure; and

[0026] Figure 2 This is a flowchart illustrating a method according to an exemplary embodiment of the present disclosure.

[0027] The accompanying drawings are not necessarily drawn to scale, and some features may be enlarged or minimized to show details of specific components. In some cases, well-known components, systems, materials, or methods have not been described in detail to avoid obscuring this disclosure. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but rather serve as the basis for the claims and as a representative basis for teaching those skilled in the art to apply this disclosure in different ways. Detailed Implementation

[0028] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses. Furthermore, it is not intended to be bound by any express or implied theory presented in the foregoing technical field, background art, summary of the invention, or the following detailed description. It should be understood that throughout the drawings, corresponding reference numerals denote similar or corresponding parts and features. Although the drawings shown herein depict examples with certain arrangements of elements, additional intermediate elements, devices, features, or parts may be present in actual embodiments. It should also be understood that the drawings are merely illustrative and may not be drawn to scale.

[0029] As used herein, the term "vehicle" is not limited to automobiles. While this document primarily describes the technology in the context of automobiles, the technology is not limited to automobiles. These concepts can be used in a variety of applications, such as aircraft, ships, other vehicles, and consumer electronics components. As used herein, the term "about" refers to plus or minus twenty-five degrees when referring to temperature, and to plus or minus twenty percent when referring to percentage.

[0030] Compared to internal combustion engines using other fossil fuels, diesel engines offer higher thermal efficiency, better torque performance, and greater reliability, leading to their widespread use in road transport and off-road machinery. Despite increasing electrification and hybridization of light vehicles, diesel engines continue to play a dominant role in many industries. Due to diffusion combustion, diesel engines emit nitrogen oxides (NOx) in their emissions. x Diesel engines exhibit high levels of particulate matter (PM) and other particulate matter, and there is a trade-off between these emissions. This trade-off makes emissions reduction from diesel engines challenging. With increasing emphasis on energy conservation and environmental pollution, global regulations on diesel engine fuel consumption and emissions control are being implemented. These regulations have placed immense pressure on the diesel engine industry, spurring technological innovation. To achieve energy conservation and emissions reduction goals, various in-cylinder purification technologies have been developed for diesel engines, including high-pressure fuel injection, multi-stage injection, variable geometry turbocharging (VGT), two-stage turbocharging, and exhaust gas recirculation (EGR). However, these in-cylinder technologies are insufficient to meet today's stringent emissions requirements. Therefore, aftertreatment devices such as diesel oxidation catalysts (DOC), diesel particulate filters (DPF), lean nitrogen oxide traps (LNT), and selective catalytic reduction (SCR) have become indispensable. This technology can also be used for aftertreatment regeneration in gasoline engine exhaust systems. Although the terminology used herein refers to diesel engines and diesel exhaust systems, those skilled in the art will understand that the novel features of this disclosure apply to gasoline-powered internal combustion engines.

[0031] Diesel particulate filters allow exhaust gases to pass through while capturing solid particulate matter. To eliminate the accumulation of these captured particles, many diesel exhaust systems incorporate O2-based aftertreatment regeneration within the DPF. This involves managing the oxygen (O2) level in the exhaust gas from the engine flowing through the DPF, and increasing the temperature of the exhaust gas to trigger a spontaneous reaction between particulate matter (carbon, C) and oxygen within the DPF, converting the solid carbon particles into CO2 gas. This CO2 gas can then pass through the DPF and the exhaust system, as shown in Equation 1.

[0032] Formula 1: C + O2 → CO2

[0033] The drawback of this system is that, when using O2 as the oxidant, the temperature required to maintain the chemical reaction is very high, ranging from approximately 500 to 650 degrees Celsius. Regeneration performance is a function of soot (particulate matter) load and temperature. This performance is linearly proportional to soot load and exponentially proportional to temperature. Continuous operation of this aftertreatment at such temperatures leads to premature "aging" of DPF components and other exhaust system components, especially SCR. In short, operation at such high temperatures causes degradation of the SCR, DPF, and other exhaust system components, potentially leading to emissions deterioration over time. Therefore, an improved system and method are needed to provide aftertreatment regeneration for DPF and SCR in diesel exhaust systems.

[0034] refer to Figure 1 According to various aspects of this disclosure, a diesel exhaust system 10 for a vehicle equipped with a diesel engine 12 includes: a diesel oxidation catalyst (DOC) 14, the DOC 14 being immediately downstream of the diesel engine 12; an upstream selective catalytic reduction (SCR) unit 16, the upstream SCR unit 16 being located downstream of the DOC 14; a first diesel exhaust fluid (DEF) injector 18, the first DEF injector 18 being positioned between the DOC 14 and the first SCR 16 and adapted to inject DEF into the exhaust gas; a diesel particulate filter (DPF) 20, the DPF 20 being located downstream of the first SCR 16 and adapted to collect particulate material from the exhaust gas passing through it; a downstream SCR 22, the downstream SCR 22 being located downstream of the DPF 20; and a second DEF injector 24, the second DEF injector 24 being positioned between the DPF 20 and the SCR 16. Between 22 and adapted to inject DEF into the exhaust gas; and an exhaust system controller 26 that communicates with an engine controller 28, multiple sensors 30A-30F and a first DEF injector 18 and a second DEF injector 24.

[0035] Both the exhaust system controller 26 and the engine controller 28 are non-general-purpose electronic control units. These units have a pre-programmed digital computer or processor, memory or non-transitory computer-readable medium, and transceivers (or input / output ports) for storing data such as control logic, software applications, instructions, computer code, data, lookup tables, etc. Computer-readable medium includes any type of media that can be accessed by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, optical disc (CD), digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable medium does not include wired, wireless, optical, or other communication links that transmit transient electrical or other signals. Non-transitory computer-readable medium includes media that can permanently store data and media that can store data and subsequently be rewritten, such as rewritable optical discs or erasable storage devices. Computer code includes any type of program code, including source code, object code, and executable code.

[0036] In an exemplary embodiment, the plurality of sensors 30A-30F includes at least: a first temperature sensor 30A adapted to monitor the temperature of exhaust gas moving from engine 12 to DOC 14, as shown by arrow 32; a second temperature sensor 30B adapted to monitor the temperature of exhaust gas moving from DOC 14 to upstream SCR 16, as shown by arrow 34; a third temperature sensor 30C adapted to monitor the temperature of exhaust gas moving from upstream SCR 16 to DPF 20, as shown by arrow 36; a fourth temperature sensor 30D adapted to monitor the temperature of exhaust gas moving from DPF 20 to downstream SCR 22, as shown by arrow 38; a fifth temperature sensor 30E adapted to monitor the temperature of exhaust gas leaving downstream SCR 22, as shown by arrow 40; and a delta pressure sensor 30F within DPF 20 adapted to monitor the DPF pressure. The level of particulate matter accumulated within 20. The multiple sensors include various other sensors incorporated within the exhaust system 10 and located within the engine 12, as well as other sensors located within the vehicle and communicating with the exhaust system controller 26.

[0037] In an exemplary embodiment, the exhaust system controller 26 is adapted to initiate nitrogen dioxide (NO2)-based aftertreatment regeneration of the DPF 20 when the particulate matter level within the DPF 20 reaches a predetermined particulate matter fill level requiring regeneration. The particulate matter level within the DPF 20 is monitored by a delta pressure sensor 30F. The initiation of NO2-based aftertreatment regeneration is based on feedback from the delta pressure sensor 30F and other information collected by each of the plurality of sensors.

[0038] Known O2-based aftertreatment regeneration methods operate at temperatures between approximately 500 and 650 degrees Celsius, while NO2-based aftertreatment regeneration methods operate at lower temperatures between approximately 300 and 500 degrees Celsius. Therefore, NO2-based aftertreatment regeneration does not cause thermal degradation of exhaust system components as much as O2-based aftertreatment regeneration.

[0039] During NO2-based aftertreatment regeneration within the DPF 20, the NO2 level in the exhaust gas from engine 12 passing through the DPF 20 increases, and the temperature of the exhaust gas from engine 12 passing through the DPF 20 is controlled, thereby triggering a spontaneous reaction between particulate matter (carbon, C) and NO2 within the DPF 20 to convert solid carbon particulate matter into CO2 gas and nitric oxide (NO). This CO2 gas and NO can then pass through the DPF 20 and the exhaust system, as shown in Formula 2.

[0040] Formula 2: C + 2NO₂ → CO₂ + 2NO

[0041] To promote spontaneous reactions within the DPF 20, the NO2 level within the DPF 20 must be increased, and the temperature of the exhaust gas within the DPF 20 must be established and maintained. However, any exhaust gas leading to the DPF 20 must first pass through the upstream SCR 16. The upstream SCR 16 is adapted to remove NO and NO2 from the exhaust gas passing through it. Therefore, to ensure that NO2 reaches the DPF 20 to initiate NO2-based aftertreatment regeneration, the exhaust system controller 26 is adapted to at least partially deactivate the first DEF injector 18 and the first SCR 16 to control the performance of the first DEF injector 18 and the upstream SCR 16, allowing sufficient NO2 to pass through the upstream SCR 16. If the first SCR is to be completely deactivated, the process is divided into two steps, wherein firstly, the exhaust system controller 26 deactivates the first DEF injector 18, thereby stopping the injection of DEF (ammonia, NH3), and then the exhaust system controller 26 allows a predetermined time to elapse before any further action to allow residual DEF in the upstream SCR 16 to dissipate. If the upstream SCR is partially shut down, the process proceeds in two steps. First, the exhaust system controller 26 controls the rate at which the first DEF injector 18 injects DEF (ammonia, NH3). Then, before any further action, the exhaust system controller 26 allows the ammonia level within the upstream SCR 16 to dissipate to a level suitable for allowing sufficient NO2 to pass through the upstream SCR 16. Ammonia in the DEF fluid is suitable for consuming both NO and NO2; therefore, the ammonia level within the upstream SCR 16 must be controlled during the start-up of NO2-based post-treatment regeneration. In some cases, it may not be necessary to completely shut down the first DEF injector 18 and the upstream SCR 16; only the performance of the first DEF injector 18 and the upstream SCR 16 needs to be controlled, such that a controlled amount of ammonia is present within the upstream SCR 16, and thus the NO / NO2 conversion occurring within the upstream SCR 16 is controlled, ensuring sufficient NO2 reaches the DPF 20.

[0042] After the first DEF injector 18 and upstream SCR 16 have been neutralized, the exhaust system controller 26 is also adapted to increase the level of nitrogen oxide (NO) in the exhaust gas from the engine 12 via communication with the engine controller 28. The DOC 14 is adapted to convert NO in the exhaust gas into NO2, which is then propagated to the DPF 20, where NO2 serves as a reducing agent for NO2-based aftertreatment regeneration.

[0043] In an exemplary embodiment, to increase the NO2 level in the exhaust gas from engine 12, exhaust system controller 26 is also adapted to selectively adjust the utilization of the exhaust gas recirculation (EGR) unit 42, injection timing, injection quantity, and fresh air quantity within engine 12 via communication with engine controller 28. Through communication with engine controller 28, exhaust system controller 26 selectively adjusts the utilization of all components and methods used within engine 12 that are adapted to reduce NO2 levels in engine exhaust. x Levels are used to increase the NO level in engine exhaust.

[0044] One known method for reducing NOx emissions is exhaust gas recirculation (EGR). This involves recirculating a controlled proportion of engine exhaust gas back into the intake air. Valves are typically used to control the flow of this gas, and can be completely closed if necessary. Replacing the oxygen-enriched air with combusted gas (which does not further participate in combustion) reduces the proportion of cylinder contents available for combustion. This results in a correspondingly lower heat release and peak cylinder temperature, and reduces NOx formation. The recirculated gas also passes through an EGR cooler, typically an air / water type. This lowers the gas temperature, thereby reducing the cylinder charge temperature when using the EGR unit. This has two effects: first, the lower charge temperature leads to a lower peak temperature; second, the cooled EGR gas is denser, allowing for a higher proportion of EGR. On diesel engines, under certain operating conditions, the recirculation fraction can be as high as fifty percent. Although it is known that the use of EGR unit 42 reduces the amount of NO in the exhaust gas from engine 12 by actively controlling the utilization of EGR, exhaust system controller 26 can reduce or eliminate the utilization of EGR unit 42 to increase the amount of NO in the exhaust gas from engine 12.

[0045] As a non-limiting example, and for illustrative purposes, in a hypothetical engine 12, a hypothetical NO2-based aftertreatment regeneration is initiated within a DPF 20, increasing the NO level in the engine exhaust to 600 parts per million (PPM) of NO, where 600 ppm is a completely random number used strictly for illustrative and descriptive purposes.

[0046] DOC 14 uses platinum and oxygen to convert NO in the exhaust gas from engine 12 into NO2, and DPF 20 uses NO2 in the exhaust gas from DOC (via upstream SCR 16) as an oxidant to convert carbon particles within DPF 20 into CO2 and NO, as shown in Equation 2 above within the DPF. However, for the chemical reactions shown in Equations 1 and 2 to occur, the temperatures within DOC 14 and DPF 20 must be at target temperatures.

[0047] In an exemplary embodiment, the exhaust system controller 26 is also adapted to actively control the combustion characteristics of the engine 12 via communication with the engine controller to establish and maintain a target exhaust gas temperature (EGT) (DPF inlet temperature) at the DPF 20 inlet 44 and a target EGT (DOC inlet temperature) at the DOC 14 inlet 46. The DPF inlet temperature is monitored by a third temperature sensor 30C, and the DOC inlet temperature is monitored by a first temperature sensor 30A. In an exemplary embodiment, as described above, the target EGT at the DPF 20 inlet 44 is as low as 300 degrees Celsius (between approximately 300 and approximately 500 degrees Celsius) to provide sufficient temperature to sustain the chemical reactions of NO2-based aftertreatment regeneration (Formula 2) while maintaining a sufficiently low temperature to minimize thermal degradation (“aging”) of components within the exhaust system 10.

[0048] The primary factors affecting the exhaust gas temperature at any point within the exhaust system 10 are the exhaust gas temperature leaving the engine 12 (i.e., the point where the exhaust gas reaches its highest temperature) and the thermal dynamics of the exhaust system 10, which determine how the exhaust gas is cooled as it flows through the exhaust system 10. Heat losses must be considered as the exhaust gas travels from the engine 12 to the DOC 14, from the DOC 14 to the upstream SCR 16, from the upstream SCR 16 to the DPF 20, and from the DPF 20 to the downstream SCR 22. Therefore, the exhaust system controller 26 is also adapted to calculate the target EGT of the exhaust gas from the engine 12 based on the target DPF inlet temperature and the thermodynamics of the exhaust system 10, and, more importantly, to calculate the target EGT of the exhaust gas from the DOC 14 in reverse.

[0049] For example, based on the thermodynamics of the exhaust system 10, if the target temperature (DPF inlet temperature) in the DPF 20 required to support aftertreatment regeneration, as measured by the third temperature sensor 30C, is 400 degrees Celsius, then the temperature in the upstream SCR 16, as measured by the second temperature sensor 30B, must be 450 degrees Celsius, and the temperature in the DOC 14 (DOC inlet temperature) must be 500 degrees Celsius.

[0050] In an exemplary embodiment, the exhaust system controller 26 is adapted to selectively utilize delayed injection and post-injection within the engine 12 via communication with the engine controller 28 to establish and maintain a target EGT for exhaust gases from the engine 12 and a target EGT for exhaust gases from the DOC 14.

[0051] Delayed ignition timing is a known strategy for rapidly preheating the catalyst. Delayed combustion reduces the work transfer from the cylinder gas to the piston, resulting in higher exhaust gas temperatures. To maintain constant engine torque, the reduced fuel conversion efficiency associated with delayed combustion requires greater fuel and airflow. Therefore, due to the higher temperatures and greater mass flow rates, delayed ignition results in a larger sensible enthalpy flow rate at engine output.

[0052] Delayed fuel injection (DFI) is a known strategy to provide closed-loop control of exhaust gas temperature and achieve high exhaust gas temperatures for aftertreatment regeneration of diesel particulate filters (DPFs). DFI is an injection strategy in which a certain amount of fuel is injected after the main injection / combustion event to release heat following the main injection combustion event. This DFI fuel is further cracked into smaller hydrocarbon molecules, then expelled from the cylinder and oxidized at DOC 14 to release high temperatures for aftertreatment regeneration within the DPF 20. This DFI fuel also improves combustion by oxidizing previously generated soot, nitrogen oxides, and reducing particulate emissions. Fuel injected during the exhaust stroke of the engine cycle provides closed-loop temperature control at the DOC 14 outlet. The temperature of the exhaust gas leaving engine 12 is typically lower than the target DOC 14 temperature. Fuel injected during the exhaust stroke is not burned in the cylinder but ignited inside the DOC 14, generating heat and raising the temperature of the exhaust gas from engine 12 to the target EGT of the exhaust gas from DOC 14.

[0053] Therefore, the exhaust system controller 26 maintains the increased NO level in the exhaust gas from the engine and maintains the target temperature at DPF 20 and DOC 14, wherein DOC 14 is adapted to convert NO in the exhaust gas entering DOC 14 into NO2.

[0054] The primary function of DOC 14 is to oxidize CO, unburned hydrocarbons, and NO, while the oxidation of active hydrocarbons can also be used to generate the exothermic heat required for downstream components. DOC 14 promotes the oxidation of exhaust components by oxygen, which is abundant in diesel exhaust. When passed through an oxidation catalyst, carbon monoxide (CO), gaseous hydrocarbons (HC), the organic portion of diesel particulate matter (OF), and unregulated emissions such as aldehydes or polycyclic aromatic hydrocarbons can be oxidized into harmless products, and therefore can be controlled using DOC 14. In this system 10, an important function of DOC 14 is to oxidize nitric oxide (NO) to nitrogen dioxide (NO2) using platinum as a catalyst.

[0055] In an exemplary embodiment, DOC 14 is adapted to convert approximately fifty percent of the NO in the exhaust gas entering DOC 14 into NO2. The NO to NO2 conversion rate depends on many factors and can be greater than or less than fifty percent based on the needs of DPF 20 and the overall design of system 10. Ultimately, DOC 14 is designed to convert NO to NO2 at a rate sufficient to ensure that an appropriate amount of NO2 reaches the DPF. Thus, referring to the non-limiting assumption example given above, where the exhaust gas from the engine comprises 600 ppm NO, DOC 14 converts approximately half of the NO in the exhaust gas from engine 12 into NO2, and where the exhaust gas leaving DOC 14 contains 300 ppm NO and 300 ppm NO2.

[0056] Within DPF 20, when carbon particulate matter within the DPF is exposed to platinum and / or palladium catalysts, solid carbon-based particulate matter accumulated within DPF 20 is converted into gaseous carbon dioxide (CO2) and NO by using NO2 present in the exhaust gas as an oxidant for NO2-based post-treatment regeneration.

[0057] Another benefit of NO2-based post-treatment regeneration is that once the chemical reaction within the DPF (Formula 2) begins, the NO byproducts of Formula 2 will further react with oxygen to form additional NO2, as shown in Formula 3, due to the presence of the platinum catalyst.

[0058] Formula 2: C + NO₂ → CO₂ + NO

[0059] Formula 3: NO+O2→NO2.

[0060] Therefore, once the chemical reaction for NO2-based post-treatment regeneration within DPF 20 begins, the reaction in Formula 3 maintains the NO2 level within the DPF to continue reacting with any remaining carbon particulate matter (soot) within DPF 20 for the time required for the exhaust gas to pass through DPF 20. Once the carbon particulate matter dissipates and more NO2 is generated through NO2-based post-treatment regeneration within DPF 20, the exhaust gas leaving DPF 20 will have less NO and more NO2. Referring again to this non-limiting example, where the exhaust gas from DOC 14 contains 300 ppm NO and 300 ppm NO2, after passing through DPF 20, the exhaust gas now contains 150 ppm NO and 450 ppm NO2. The exhaust gas from DPF 20 proceeds to downstream SCR 22, which is adapted to convert the remaining NO and NO2 in the exhaust gas from DPF 20 into nitrogen (N2) and water (H2O), as is known in the art.

[0061] Therefore, by using a control strategy that incorporates NO2-based aftertreatment regeneration to remove soot accumulated within the DPF 20, the exhaust system controller 26 can minimize the thermal degradation of the system 10. However, NO2-based aftertreatment regeneration operates more slowly than conventional O2-based aftertreatment regeneration. NO2-based aftertreatment regeneration removes soot from the DPF 20 at a rate potentially less than half the soot removal rate when using conventional O2-based aftertreatment regeneration. This means that sometimes the NO2-based aftertreatment regeneration strategy using the DPF may not be able to keep up with the rate of soot accumulation within the DPF.

[0062] In an exemplary embodiment, when the exhaust system controller 26 is performing NO2-based aftertreatment regeneration of the DPF 20, the exhaust system controller 26 is also adapted to monitor the level of carbon particulate matter in the DPF 20 via communication with the delta pressure sensor 30F, and is adapted to initiate short-term O2-based aftertreatment regeneration of the DPF 20 when one of the following occurs: 1) the particulate matter level in the DPF 20 increases during NO2-based aftertreatment regeneration; or 2) the rate of decrease of the particulate matter level in the DPF during NO2-based aftertreatment regeneration is less than a predetermined rate.

[0063] Therefore, the control strategy includes alternative options for situations where the operating conditions of engine 12 cause soot buildup in DPF 20 to occur faster than NO2-based aftertreatment regeneration can keep up, and thus exhaust system controller 26 implements short-term O2-based aftertreatment regeneration at a correspondingly higher temperature (500 to 650 degrees Celsius) for a short period of time, in which particulate matter in DPF 20 is oxidized at a much faster rate, bringing the carbon level in DPF 20 back to a controllable level, where exhaust system controller 26 can switch back to NO2-based aftertreatment regeneration. Ideally, the time range should be limited to a few minutes (one to five minutes). The shorter the time range, the less thermal degradation of the components of exhaust system 10. However, exhaust system controller 26 is adapted to initiate short-term O2-based aftertreatment regeneration for a period sufficient to bring the carbon level in DPF to a controllable level. Therefore, in extreme cases, the time range of short-term O2-based aftertreatment regeneration may be extended to more than a few minutes. This short-term O2 aftertreatment regeneration is implemented only for a short period of time, and only in extreme cases where the NO2-based aftertreatment regeneration of DPF 20 cannot keep up with the accumulation of carbon particulate matter and the exhaust system controller 26 determines that the soot oxidation rate must be temporarily increased.

[0064] When O2-based short-term aftertreatment regeneration within the DPF 20 is initiated, the exhaust system controller 26 is also adapted to increase the O2 level in the exhaust gas at the DPF intake 44 by selectively adjusting the utilization of the EGR unit 42, fresh air control, injection timing, and injection quantity within the engine 12, thereby managing the O2 level in the exhaust gas from the engine 12 through communication with the engine controller 28. This typically results in a reduction in O2 levels because the incoming ambient air contains 21% oxygen, while the appropriate O2 level required for O2-based aftertreatment regeneration is below 21%. Control of the O2 level in the exhaust gas is primarily achieved through fresh air control and injection timing / injection quantity.

[0065] In an exemplary embodiment, the exhaust system controller 26 is also adapted to actively control the combustion characteristics of the engine 12 via communication with the engine controller 28 to establish and maintain a target exhaust gas temperature (EGT) at the intake port 44 of the DPF 20. The DPF intake port temperature is monitored by a third temperature sensor 30°C. In an exemplary embodiment, as described above, the target EGT at the intake port 44 of the DPF 20 is between approximately 500°C and approximately 650°C to provide sufficient temperature to sustain the chemical reactions of O2-based aftertreatment regeneration (Formula 1).

[0066] As described above, the exhaust system controller 26 is also adapted to calculate the target EGT of the exhaust gas from the engine 12 based on the target DPF inlet temperature for O2-based aftertreatment regeneration and the thermodynamic characteristics of the exhaust system 10, and to calculate the EGT of the exhaust gas from the DOC 14 in reverse.

[0067] For example, where the temperature is non-limiting and strictly for illustrative purposes, based on the thermodynamics of the exhaust system 10, if the target temperature (DPF inlet temperature) within the DPF 20 required for O2-based aftertreatment regeneration, as measured by the third temperature sensor 30C, is 600 degrees Celsius, then the temperature within the upstream SCR 16, as measured by the second temperature sensor 30B, must be 650 degrees Celsius, and the temperature within the DOC 14 (DOC inlet temperature) must be 700 degrees Celsius.

[0068] In an exemplary embodiment, the exhaust system controller 26 is adapted to selectively utilize delayed injection and post-injection within the engine 12 via communication with the engine controller 28 to establish and maintain a target EGT for exhaust gases from the engine 12 and a target EGT for exhaust gases from the DOC, as described above.

[0069] Within DPF 20, when carbon particulate matter within the DPF is exposed to platinum and / or palladium catalysts, solid carbon-based particulate matter accumulated within DPF 20 is converted into gaseous carbon dioxide (CO2) by using O2 present in the exhaust gas as an oxidant for O2-based post-treatment regeneration.

[0070] One advantage of high-temperature, O2-based post-treatment regeneration is that the high temperatures within the upstream SCR 16 and downstream SCR 22 help reduce the absorption and accumulation of sulfur oxides (SO₄) within these two processes. x Despite the use of low-sulfur fuels and desulfurization processes, the exhaust gas still contains parts per million (ppm) of SO2. This trace sulfur, by forming inert metal sulfates, poisons the active sites of upstream SCR 16 and downstream SCR 22. This deactivation severely reduces catalytic performance.

[0071] Therefore, part of the control strategy for exhaust system 10 ensures that the SO2 absorbed in upstream SCR 16 and downstream SCR 22 is reduced. x Accidental desorption. If a predetermined time has elapsed, during which the high-temperature, O2-based post-treatment regeneration of the DPF has not yet begun, or when the estimated sulfur level exceeds a predetermined threshold, the exhaust system controller 26 further adapts to initiate short-term SCR desulfurization for internal desorption of SO in at least one of the upstream SCR 16 and downstream SCR 22. x .

[0072] In an exemplary embodiment, the exhaust system controller 26 is also adapted to actively control the combustion characteristics of the engine 12 via communication with the engine controller 28 to establish and maintain a target exhaust gas temperature (EGT) at one or both of the upstream SCR 16 intake port 48 and the downstream SCR 22 intake port 50. The exhaust gas temperature at the upstream SCR 16 intake port 48 is monitored by a second temperature sensor 30B, and the exhaust gas temperature at the downstream SCR 22 intake port 50 is monitored by a fourth temperature sensor 30D. The target EGT at the upstream SCR 16 and / or downstream SCR 22 is sufficient to cause spontaneous desorption (removal) of SO₂ at the upstream SCR 16 and / or downstream SCR 22. x The temperature, as understood in the industry.

[0073] As described above, the exhaust system controller 26 is also adapted to be based on the method for removing SO2. x The target exhaust gas temperature (EGT) at one or both of the upstream SCR 16 intake port 48 and the downstream SCR 22 intake port 50, and the thermodynamic characteristics of the exhaust system 10, are used to inversely calculate the target EGT of the exhaust gas from the engine 12.

[0074] For example, where the temperature is non-limiting and strictly for illustrative purposes, based on the thermodynamics of the exhaust system 10, if the temperature measured by the fourth temperature sensor 30D supports the removal of SO2. x If the target temperature in the downstream SCR 22 is 550 degrees Celsius, then the temperature in the upstream DPF 20, measured by the third temperature sensor 30C, must be 600 degrees Celsius, and the temperature in the first SCR 16, measured by the second temperature sensor 30B, must be 650 degrees Celsius, and the temperature in the DOC 14 (DOC inlet temperature) must be 700 degrees Celsius.

[0075] In an exemplary embodiment, the exhaust system controller 26 is adapted to selectively utilize delayed injection and post-injection within the engine 12 via communication with the engine controller 28 to establish and maintain a target EGT for exhaust gases from the engine 12 and a target EGT for exhaust gases from the DOC 14, as described above.

[0076] Therefore, the control strategy using the system 10 of this disclosure includes: 1) primarily using NO2-based aftertreatment regeneration of the DPF 20 to achieve the NO2 level and temperature in the exhaust gas to support NO2-based aftertreatment regeneration by intrusively and actively controlling the EGR 42 function and combustion characteristics (injection timing, injection quantity, and fresh air quantity) within the engine 12; 2) occasionally, when soot reduction in the DPF 20 is ineffective during NO2-based aftertreatment regeneration, using O2-based aftertreatment regeneration of the DPF 20 for a short period of time to achieve the O2 level and temperature in the exhaust gas to support O2-based aftertreatment regeneration by intrusively and actively controlling the EGR 42 function and combustion characteristics (injection timing, injection quantity, and fresh air quantity) within the engine 12; and 3) occasionally, when O2-based aftertreatment regeneration has not been recently initiated, using the upstream SCR 16 and downstream SCR to achieve the O2 level and temperature in the exhaust gas to support O2-based aftertreatment regeneration by intrusively and actively controlling the EGR 42 function and combustion characteristics (injection timing, injection quantity, and fresh air quantity) within the engine 12. One or both of the 22 SCRs are used for desulfurization to remove SO2 from one or both of the upstream SCR 16 and downstream SCR 22. x To achieve the required O2 levels and temperatures in the exhaust gas, thereby supporting SO2 levels in one or both of the upstream SCR 16 and downstream SCR 22. x Desorption.

[0077] refer to Figure 2A method 100 for aftertreatment regeneration in a diesel vehicle includes: starting from block 102, routing exhaust gas from a diesel engine 12 through an exhaust system 10 within the vehicle, the exhaust system 10 including: a diesel oxidation catalyst (DOC) 14, the DOC 14 being immediately downstream of the diesel engine 12; an upstream selective catalytic reduction (SCR) unit 16, the upstream SCR unit 16 being located downstream of the DOC 14; a first diesel exhaust fluid (DEF) injector 18, the first DEF injector 18 being positioned between the DOC 14 and the first SCR 16 and adapted to inject DEF into the exhaust gas; a diesel particulate filter (DPF) 20, the DPF 20 being located downstream of the SCR 16 and adapted to collect particulate material from the exhaust gas passing through it; a downstream SCR 22 unit, the downstream SCR 22 unit being located downstream of the DPF 20; and a second DEF injector 24, the second DEF injector 24 being located between the DPF 20 and the SCR 20. Between 22 and adapted to inject DEF into the exhaust gas; and an exhaust system controller 26 that communicates with the engine controller 28, a plurality of sensors 30A-30F in the exhaust system 10 and the first DEF injector 18 and the second DEF injector 24.

[0078] Moving to box 104, method 100 further includes initiating nitrogen dioxide (NO2)-based aftertreatment regeneration of the DPF 20 by: moving to box 106, at least partially disabling the first DEF injector 18 and the upstream SCR 16 using the exhaust system controller 26, thereby allowing NO2 to pass through the upstream SCR 16; moving to box 108, increasing the level of nitrogen monoxide (NO) in the exhaust gas from the engine 12 by the exhaust system controller 26 via communication with the engine controller 28; moving to box 110, actively controlling the combustion characteristics of the engine 12 by the exhaust system controller 26 via communication with the engine controller 28 to establish and maintain a target exhaust gas temperature (EGT) (DPF inlet temperature) at the DPF 20 inlet 44 and a target EGT (DOC inlet temperature) at the DOC 14 inlet 46; moving to box 112, using the DOC 14 to... NO in the exhaust gas of 14 is converted into NO2; moved to box 114, solid carbon-based particulate matter accumulated in DPF 20 is converted into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant; and moved to box 116, NO and NO2 in the exhaust gas from DPF 20 are converted into nitrogen (N2) and water (H2O) in the downstream SCR 22.

[0079] In an exemplary embodiment, at block 108, increasing the level of NO in the exhaust gas from the engine 12 by means of the exhaust system controller 26 communicating with the engine controller 28 further includes selectively adjusting the utilization of the exhaust gas recirculation (EGR) unit 42, injection timing, injection quantity, and fresh air quantity within the engine 12 by means of the exhaust system controller 26 communicating with the engine controller 28.

[0080] In an exemplary embodiment, at block 110, actively controlling the combustion characteristics of engine 12 by utilizing exhaust system controller 26 via communication with engine controller 28 to establish and maintain target exhaust gas temperature (EGT) at DPF 20 intake port 44 and target EGT at DOC 14 intake port 46 further includes: moving to block 118, calculating target EGT of exhaust gas from engine 12 and target EGT of exhaust gas from DOC 14 based on target DPF intake port temperature and thermodynamic characteristics of exhaust system 10; and moving to block 120, selectively utilizing delayed injection and post-injection within engine 12 by utilizing exhaust system controller 26 via communication with engine controller 28 to establish and maintain target EGT of exhaust gas from engine 12 and target EGT of exhaust gas from DOC 14.

[0081] In an exemplary embodiment, establishing and maintaining a target exhaust gas temperature (EGT) at the DPF 20 inlet 44 at block 110 further includes establishing and maintaining the DPF inlet temperature as low as 300 degrees Celsius (between approximately 300 and approximately 500 degrees Celsius).

[0082] In an exemplary embodiment, at block 112, the conversion of NO in the exhaust gas entering DOC 14 to NO2 using DOC 14 further includes: using platinum as a catalyst to convert approximately fifty percent of the NO in the exhaust gas entering DOC 14 to NO2 using DOC 14.

[0083] In an exemplary embodiment, at block 106, the exhaust system controller 26 at least partially disables the first DEF injector 18 and the upstream SCR 16, allowing NO2 to pass through the upstream SCR 16. This also includes, at block 108, before the NO level in the exhaust gas from the engine 12 increases, and at block 110, before establishing and maintaining the target DPF 20 inlet temperature and the target DOC 14 inlet temperature, and at block 112, before converting NO in the exhaust gas entering the DOC 14 into NO2 using the DOC 14. The exhaust system controller 26 at least partially disables the first DEF injector 18 and allows residual DEF in the upstream SCR 16 to dissipate.

[0084] In an exemplary embodiment, at block 114, converting (oxidizing) solid carbon-based particles accumulated within the DPF 20 into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant further includes: exposing the carbon particles within the DPF 20 to a platinum and palladium catalyst, wherein the carbon particles and NO2 react to form CO2 and NO, and further wherein NO reacts with oxygen (O2) to form NO2, wherein the newly formed NO2 further reacts with the carbon particles.

[0085] In an exemplary embodiment, method 100 further includes: moving to block 122 to monitor the level of carbon particulate matter in the DPF 20 via communication with the delta pressure sensor 30F using the exhaust system controller 26; and moving to block 124, returning to block 122 if the exhaust system is not currently running NO2-based aftertreatment regeneration, and moving to block 126 if the exhaust system is currently running NO2-based aftertreatment regeneration.

[0086] At box 126, if the particulate matter level in DPF 20 increases during NO2-based post-treatment regeneration, the process moves to box 128, and method 100 includes initiating a short-term O2-based post-treatment regeneration of DPF 20. At box 126, if the particulate matter level in DPF 20 does not increase during NO2-based post-treatment regeneration, method 100 includes moving to box 130.

[0087] At box 130, if the rate of decrease in particulate matter level within the DPF during NO2-based post-treatment regeneration is less than a predetermined rate, then the process moves to box 128, and method 100 includes initiating O2-based short-term post-treatment regeneration of the DPF 20. At box 130, if the rate of decrease in particulate matter level within the DPF during NO2-based post-treatment regeneration is not less than a predetermined rate, then method 100 includes moving to box 132.

[0088] At box 128, initiating O2-based short-term aftertreatment regeneration of DPF 20 further includes: moving to box 140, selectively adjusting the utilization of EGR unit 42, injection timing, injection quantity, and fresh air quantity within engine 12 by means of exhaust system controller 26 communicating with engine controller 28, thereby increasing the O2 level in the exhaust gas at DPF intake 44 by controlling the O2 level in the exhaust gas from engine 12 via exhaust system controller 26 communicating with engine controller 28; moving to box 142, establishing and maintaining a desired EGT between approximately 500 degrees Celsius and 650 degrees Celsius at DPF 20 intake 44 by: moving to box 144, calculating the target EGT from exhaust gas from engine 12 and the O2 level from DOC based on the desired EGT at DPF intake 44 and the thermodynamic characteristics of exhaust system 10. The method further includes: a target EGT for the exhaust gas from engine 12; and moving to block 146, actively controlling the combustion characteristics of engine 12 by utilizing exhaust system controller 26 via communication with engine controller 28, and selectively utilizing delayed injection and post-injection within engine 12 by utilizing exhaust system controller 26 via communication with engine controller 28 to establish and maintain the target EGT for the exhaust gas from engine 12 and the target EGT for the exhaust gas from DOC 14. Moving to block 148, the method also includes converting solid carbon-based particulate matter accumulated within DPF 20 into gaseous CO2 by using O2 as an oxidant.

[0089] At box 132, if a predetermined time window has not elapsed since the exhaust system controller 26 initiated O2-based short-term aftertreatment regeneration, or if the estimated sulfur level exceeds a predetermined threshold, method 100 returns to box 122. If, at box 132, a predetermined time window has elapsed since the exhaust system controller 26 initiated O2-based short-term aftertreatment regeneration, the process moves to box 134, and method 100 further includes initiating short-term SCR desulfurization and desorption of sulfur oxides (SO₂) within at least one of the upstream SCR 16 and downstream SCR 22. x ).

[0090] In an exemplary embodiment, at block 134, a short-term SCR desulfurization and desorption of sulfur oxides (SO₄) is initiated within at least one of the upstream SCR 16 and the downstream SCR 22. xThe method further includes establishing and maintaining a target desorption EGT in at least one of the intake port 48 of the upstream SCR 16 and the intake port 50 of the downstream SCR 22 by: moving to block 136, calculating the target EGT of the exhaust gas from the engine 12 and the target EGT of the exhaust gas from the DOC 14 based on the target desorption EGT and the thermodynamic characteristics of the exhaust system 10; and moving to block 138, actively controlling the combustion characteristics of the engine 12 by utilizing the exhaust system controller 26 via communication with the engine controller 28, and selectively utilizing delayed injection and post-injection within the engine 12 by utilizing the exhaust system controller 26 via communication with the engine controller 28, to establish and maintain the target EGT of the exhaust gas from the engine 12 and the target EGT of the exhaust gas from the DOC 14.

[0091] The system and method disclosed herein have the following advantages: providing a control strategy for performing aftertreatment regeneration within a diesel exhaust system 10, including: 1) primarily using NO2-based aftertreatment regeneration via DPF 20 to achieve NO2 levels and temperatures in the exhaust gas to support NO2-based aftertreatment regeneration by intrusive and active control of the EGR 42 function and combustion characteristics within engine 12; 2) occasionally, when soot reduction within DPF 20 is ineffective during NO2-based aftertreatment regeneration, using O2-based aftertreatment regeneration via DPF 20 for short periods to achieve O2 levels and temperatures in the exhaust gas to support O2-based aftertreatment regeneration by intrusive and active control of the EGR 42 function and combustion characteristics (injection timing, injection quantity, and fresh air quantity) within engine 12; and 3) occasionally, when O2-based aftertreatment regeneration has not been recently initiated, using upstream SCR 16 and downstream SCR 16 to support O2-based aftertreatment regeneration by intrusive and active control of the EGR 42 function and combustion characteristics (injection timing, injection quantity, and fresh air quantity) within engine 12. One or both of the 22 SCRs are used for desulfurization to remove SO2 from one or both of the upstream SCR 16 and downstream SCR 22. x This achieves the required O2 level and temperature in the exhaust gas to support SO2 levels in one or both of the upstream SCR 16 and downstream SCR 22. x Desorption.

[0092] The descriptions in this disclosure are merely exemplary in nature, and variations that do not depart from the spirit of this disclosure are intended to fall within its scope. These variations should not be considered as departing from the scheme and scope of this disclosure.

Claims

1. A method for aftertreatment regeneration in a diesel vehicle, comprising: Exhaust gases from the diesel engine are routed through an exhaust system within the vehicle, the exhaust system comprising: Diesel oxidation catalyst DOC, wherein the DOC is located immediately downstream of the diesel engine; An upstream selective catalytic reduction (SCR) unit is located downstream of the DOC; A first diesel exhaust fluid (DEF) injector is positioned between the DOC and the first SCR and is adapted to inject DEF into the exhaust gas; A diesel particulate filter (DPF), the DPF being located downstream of the first SCR and adapted to collect particulate material from exhaust gas passing through it; and An exhaust system controller, which communicates with an engine controller, multiple sensors within the exhaust system, and a first DEF injector; and The nitrogen dioxide (NO2)-based post-treatment regeneration of the DPF is initiated in the following manner: By using the exhaust system controller, at least partially deactivating the first DEF injector and the upstream SCR, NO2 is allowed to pass through the upstream SCR; The exhaust system controller is used to increase the level of nitrogen oxide (NO) in the exhaust gas from the engine via communication with the engine controller; By utilizing the exhaust system controller to actively control the combustion characteristics of the engine via communication with the engine controller, a target exhaust gas temperature EGT (DPF inlet temperature) at the DPF inlet and a target EGT (DOC inlet temperature) at the DOC inlet are established and maintained. The NO in the exhaust gas entering the DOC is converted into NO2 using the DOC; and By using NO2 as an oxidant, the solid carbon-based particles accumulated in the DPF are converted into gaseous carbon dioxide (CO2) and NO.

2. The method according to claim 1, wherein, The method of increasing the level of nitrogen oxide (NO) in the exhaust gas from the engine by means of the exhaust system controller via communication with the engine controller also includes selectively adjusting the utilization of the exhaust gas recirculation (EGR) unit, injection timing, injection quantity, and fresh air quantity within the engine by means of the exhaust system controller via communication with the engine controller.

3. The method according to claim 2, wherein, The method of actively controlling the combustion characteristics of the engine by utilizing the exhaust system controller via communication with the engine controller to establish and maintain target exhaust gas temperature (EGT) at the DPF inlet and target EGT (DOC inlet temperature) at the DOC inlet also includes: Based on the target DPF inlet temperature, the target DOC inlet temperature, and the thermodynamic characteristics of the exhaust system, calculate the target EGT of the exhaust gas from the engine; and By utilizing the exhaust system controller to selectively utilize delayed injection and post-injection within the engine via communication with the engine controller, the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC are established and maintained.

4. The method according to claim 3, wherein, The establishment and maintenance of the target exhaust gas temperature EGT (DPF inlet temperature) at the DPF inlet also includes establishing the DPF inlet temperature and maintaining it between approximately 300 degrees Celsius and approximately 500 degrees Celsius.

5. The method according to claim 4, wherein, The method of using the DOC to convert NO in the exhaust gas entering the DOC into NO2 also includes using platinum as a catalyst to convert NO in the exhaust gas entering the DOC into NO2.

6. The method according to claim 5, wherein, The method of at least partially disabling the first DEF injector and the upstream SCR using the exhaust system controller, allowing NO2 to pass through the upstream SCR, also includes establishing and maintaining a target DPF inlet temperature and a target DOC inlet temperature before the NO level in the exhaust gas from the engine increases, and using the DOC to convert NO in the exhaust gas entering the DOC into NO2: The first DEF injector is at least partially deactivated using the exhaust system controller; and This allows the residual DEF within the upstream SCR to dissipate to an acceptable level.

7. The method according to claim 6, wherein, The process of converting solid carbon-based particulate matter accumulated in the DPF into gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant further includes: The carbon particles within the DPF are exposed to at least one of a platinum and a palladium catalyst, wherein the carbon particles react with the NO2 to form CO2 and NO, and further wherein the NO reacts with oxygen (O2) to form NO2, wherein the newly formed NO2 further reacts with the carbon particles.

8. The method according to claim 7, further comprising: The exhaust system controller monitors the level of particulate matter within the DPF via communication with a delta pressure sensor and the exhaust gas temperature within the DPF; and Short-term O2-based post-treatment regeneration of the DPF is initiated when one of the following conditions is met: During NO2-based post-treatment regeneration, the particulate matter level within the DPF increases; or During NO2-based post-treatment regeneration, the rate of decrease in the particulate matter level within the DPF is less than a predetermined rate.

9. The method according to claim 8, wherein, The short-term O2-based post-treatment regeneration for initiating DPF also includes: By using the exhaust system controller to selectively adjust the utilization of the EGR unit, injection timing, injection quantity, and fresh air quantity within the engine via communication with the engine controller, the exhaust system controller can control the O2 level in the exhaust gas from the engine via communication with the engine controller, thereby managing the O2 level in the exhaust gas at the DPF intake. The desired EGT is established and maintained at the DPF inlet in the following manner: Based on the desired EGT at the DPF intake and the thermodynamic characteristics of the exhaust system, calculate the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC; and By actively controlling the combustion characteristics of the engine through communication with the engine controller using the exhaust system controller, and by selectively utilizing delayed injection and post-injection within the engine through communication with the engine controller using the exhaust system controller, the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC are established and maintained; and By using O2 as an oxidant, the solid carbon-based particles accumulated in the DPF are converted into gaseous CO2.

10. The method of claim 9, further comprising initiating short-term SCR desulfurization and desorbing sulfur oxides SO₂ from the upstream SCR. x The short-term SCR desulfurization includes: The target desorption EGT is established and maintained at the inlet of the upstream SCR in the following manner: Based on the target desorption EGT and the thermodynamic characteristics of the exhaust system, calculate the target EGT from the exhaust gas from the engine and the target EGT from the exhaust gas from the DOC; as well as By actively controlling the combustion characteristics of the engine through communication with the engine controller using the exhaust system controller, and by selectively utilizing delayed injection and post-injection within the engine through communication with the engine controller using the exhaust system controller, the target EGT of the exhaust gas from the engine and the target EGT of the exhaust gas from the DOC are established and maintained.

Images