DE102019113006A1 - POST-TREATMENT SYSTEM WITH Lean NOx trap filter - Google Patents

Abstract

An aftertreatment system includes a first pipe section in fluid communication with an exhaust manifold of an internal combustion engine. A first aftertreatment device includes a housing and a porous substrate with substrate walls that define a plurality of flow channels, including first channels that are blocked at a first end of the substrate and second channels that are blocked at a second end of the substrate opposite the first end are. The first and second channels are nested and the inner pore surfaces in the porous substrate form a plurality of inner pores. A passive NOx adsorption catalyst is deposited on the substrate walls and the inner pore surfaces, so that the average porosity of the porous substrate is not greater than a secondary particle size of the particles. A second aftertreatment device with an inlet is in fluid communication with the outlet of the first aftertreatment device.

Description

TECHNICAL AREA

The present disclosure relates generally to an aftertreatment system for exhaust gases from an internal combustion engine, and in particular to an aftertreatment architecture with a lean NOx trap filter in combination with a selective catalytic reduction device.

BACKGROUND

Generally, vehicles, such as automobiles, are powered by a propulsion system. Certain motor vehicles use an internal combustion engine, such as a diesel engine, as the drive system that provides energy that is transferred to a transmission and used to drive the motor vehicle. To meet the latest, stricter emissions regulations, an aftertreatment system with one or more aftertreatment devices can be used to remove combustion by-products such as diesel particles, carbon monoxide, nitrogen oxides (NOx), sulfur oxides (SOx), unburned hydrocarbons and the like from an exhaust gas stream, before the exhaust gas stream is expelled from the internal combustion engine.

Conventional aftertreatment systems have certain operating temperature ranges that must be achieved to achieve adequate conversion efficiencies. For example, a selective catalytic reduction (SCR) device may not achieve sufficient conversion efficiency until it has reached an operating temperature in the range of 200-300 ° C. In these situations, the aftertreatment system does not provide sufficient conversion efficiencies at lower temperature ranges (e.g. below 200 ° C) during engine start up or in extremely low environmental conditions. An additional aftertreatment device, such as a lean NOx trap (LNT), can be integrated to expand the temperature range of the aftertreatment system and to remove the combustion by-products in lower temperature ranges. However, the LNT device may not be as efficient at removing combustion by-products as the higher operating temperature SCR system and other particle removal device.

Accordingly, it is desirable to provide a system and method for aftertreatment of an exhaust gas stream in one or more aftertreatment devices over a relatively wide operating temperature range. The use of a gradual aftertreatment device would provide efficient combustion by-product removal at a range of operating temperatures. Further desirable functions and features of the present disclosure will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings, as well as the foregoing technical field and background.

SUMMARY

According to the present disclosure, an exhaust gas aftertreatment device for the exhaust gases of an internal combustion engine is provided. The aftertreatment device includes a housing with an inlet and an outlet. A porous substrate is disposed in the housing and includes substrate walls that define a plurality of flow channels, including first channels that are blocked at a first end of the substrate and second channels that are blocked at a second end of the substrate opposite the first end. The first and second channels are nested and the inner pore surfaces in the porous substrate form a plurality of inner pores that define tortuous passages between the substrate walls. A passive NOx adsorption catalyst is deposited on the substrate walls and the inner pore surfaces, so that the average porosity of the porous substrate is not greater than a secondary particle size of the particles. According to an additional embodiment, the average porosity of the substrate is not less than 10 µm and not more than 20 µm in order to adequately filter particles and at the same time limit the pressure drop across the device.

According to an additional embodiment, the porous substrate is coated uniformly with the catalyst, so that the concentration of the catalyst on the substrate in the exhaust gas flow direction remains essentially constant over the length of the substrate. According to an alternative embodiment, the porous substrate is zone coated with the catalyst so that the concentration of the catalyst varies along the length of the substrate to define different zones based on the catalyst concentration in each area of the substrate.

According to an additional embodiment, the exhaust gas aftertreatment device further includes a diesel oxidation catalyst section, which is arranged in the housing between the inlet and the porous substrate.

According to an additional embodiment, the exhaust gas aftertreatment device includes a fuel injector configured to inject a hydrocarbon fuel into the exhaust gas stream downstream of the internal combustion engine and upstream of the porous substrate.

According to the present disclosure, an aftertreatment system for exhaust gases from an internal combustion engine with an exhaust manifold is disclosed. The aftertreatment system includes a first pipe section that is configured to be in fluid communication with an exhaust manifold of the internal combustion engine. A first aftertreatment device includes a housing having an inlet and an outlet. A porous substrate is disposed in the housing and has substrate walls that define a plurality of flow channels, including first channels that are blocked at a first end of the substrate and second channels that are blocked at a second end of the substrate opposite the first end , The first and second channels are nested and the inner pore surfaces in the porous substrate form a plurality of inner pores that define tortuous passages between the substrate walls. A passive NOx adsorption catalyst is deposited on the substrate walls and the inner pore surfaces, so that the average porosity of the porous substrate is not greater than a secondary particle size of the particles. A second aftertreatment device includes an inlet in fluid communication with the outlet of the first aftertreatment device. According to an additional embodiment, the porous substrate in the first aftertreatment device has an average porosity of not less than 10 μm and not more than 20 μm in order to adequately filter particles and at the same time limit the pressure drop across the device.

According to an additional embodiment, the porous substrate in the first aftertreatment device is coated uniformly with the catalyst, so that the concentration of the catalyst on the substrate in the exhaust gas flow direction remains essentially constant over the length of the substrate. According to an alternative embodiment, the porous substrate in the first aftertreatment device is zone coated with the catalyst so that the concentration of the catalyst varies over the length of the substrate to define different zones based on the catalyst concentration in each area of the substrate.

In accordance with an additional embodiment, the aftertreatment system further includes a diesel oxidation catalyst section disposed in the housing between the inlet and the porous substrate.

According to an additional embodiment, the aftertreatment system further includes a fuel injector configured to inject a hydrocarbon fuel into the aftertreatment system downstream of the exhaust manifold and upstream of the first aftertreatment device.

According to an additional embodiment, the second aftertreatment device includes a selective catalytic reduction (SCR) unit downstream of the first aftertreatment device. According to an additional embodiment, the aftertreatment system further includes a fluid injector configured to inject a diesel exhaust fluid into the aftertreatment system downstream of the first aftertreatment device and upstream of the SCR unit.

According to an additional embodiment, the first aftertreatment device has a NOx conversion efficiency of more than 40% in a first temperature range between about 100 ° C. and 300 ° C. and the second aftertreatment device has a NOx conversion efficiency of more than 55% in a second temperature range between about 200 ° C and 450 ° C.

According to an additional embodiment, the aftertreatment system further includes a second pipe section having a first end in fluid communication with the outlet of the first aftertreatment device and a second end in fluid communication with the SCR unit so that the second pipe section separates the first and second aftertreatment devices. According to an additional embodiment, the aftertreatment system further includes a low pressure exhaust gas recirculation circuit in fluid communication with the second pipe section.

list of figures

• 1 zeigt schematisch ein Automobilsystem gemäß einer Ausführungsform der vorliegenden Offenbarung;
• 2 ist der Abschnitt A-A eines Verbrennungsmotors des Automobilsystems von 1;
• 3 stellt ein Nachbehandlungssystem mit einer ersten Nachbehandlungsvorrichtung in Form eines Mager-NOx-(LNT)-Filters stromaufwärts einer zweiten Nachbehandlungsvorrichtung in Form einer selektiven katalytischen Reduktions-(SCR)-Einheit dar;
• 4 stellt ein Nachbehandlungssystem mit einer ersten Nachbehandlungsvorrichtung einschließlich eines Dieseloxidationskatalysators (DOC) und einem LNT-Filter stromaufwärts einer zweiten Nachbehandlungsvorrichtung in Form einer SRC-Einheit dar;
• 5 ist eine schematische Darstellung, die einen Querschnitt eines LNT-Filters darstellt;
• 6A ist ein Detail des in 5 gezeigten LNT-Filters, der den Abgasstrom durch den LNT-Filter anzeigt; und
• 6B ist ein Detail bei 6B von 6A, der den Abgasstrom durch das poröse Substrat anzeigt.

The exemplary embodiments are described below in conjunction with the following drawings, wherein like numerals designate like elements.

• 1 schematically illustrates an automotive system according to an embodiment of the present disclosure;
• 2 is the section AA of an internal combustion engine of the automotive system of 1 ;
• 3 FIG. 4 illustrates an aftertreatment system with a first aftertreatment device in the form of a lean NOx (LNT) filter upstream of a second aftertreatment device in the form of a selective catalytic reduction (SCR) unit;
• 4 FIG. 4 illustrates an aftertreatment system with a first aftertreatment device including a diesel oxidation catalyst (DOC) and an LNT filter upstream of a second aftertreatment device in the form of an SRC unit;
• 5 Fig. 4 is a schematic diagram illustrating a cross section of an LNT filter;
• 6A is a detail of the in 5 shown LNT filter, which indicates the exhaust gas flow through the LNT filter; and
• 6B is a detail at 6B from 6A that indicates the flow of exhaust gas through the porous substrate.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention disclosed herein. Furthermore, there is no intention in the above technical field, background, summary or the following detailed description to be bound to an explicitly or implicitly presented theory, it is expressly reproduced as the claimed subject matter.

Some embodiments, as shown in FIGS 1 and 2 shown an automotive system 10 include an internal combustion engine (ICE) 12 with an engine block 14 includes at least one cylinder 16 with a piston 18 defined that are coupled to a crankshaft 20 to turn. A cylinder head 22 forms together with the piston 18 a combustion chamber 24 , A fuel / air mixture can enter the combustion chamber 24 be injected and ignited, resulting in a reciprocal movement of the piston 18 caused by the expanding hot exhaust gases. The fuel is under high pressure from the fuel rail 28 in fluid communication with a high pressure fuel pump 30 to increase the pressure of the fuel from a fuel source 32 is connected to the fuel injector 26 directed. The air passes through at least one inlet duct 34 fed. Each of the cylinders 16 has at least two valves 36 on by a camshaft 38 are operated, which are coordinated with the crankshaft 20 rotates. The valves 36 selectively let air out of the intake duct 34 into the combustion chamber 24 and alternatively the exhaust gases through an exhaust opening 40 escape. In some examples, a cam phaser 42 selectively timing between the camshaft 38 and the crankshaft 20 vary.

The air can pass through an intake manifold 44 to the inlet opening (s) 34 be transported. An intake duct 46 can take ambient air to the intake manifold 44 conduct. In other embodiments, a throttle body 48 to control the air flow to the intake manifold 44 be installed. In still other embodiments, other blower systems are provided, for example a turbocharger 50 with a compressor 52 that is rotating with a turbine 54 connected is. The rotation of the compressor 52 increases the pressure and temperature of the air in the intake duct 46 and intake manifold 44 , An intercooler 56 in the intake duct 46 can reduce the temperature of the air. The turbine 54 rotates due to the incoming exhaust gases from the exhaust manifold 58 , the exhaust gases from the exhaust openings 40 through a series of blades of the turbine 54 before expanding. This example shows a Variable Geometry Turbine (VGT) with a VGT actuator 60 , which is arranged to move the blade to the exhaust gas flow through the turbine 54 to change. In other embodiments, the turbocharger 50 be a solid geometry and / or include a wastegate.

The exhaust gases leave the turbine 54 and are in an aftertreatment system 62 directed. The aftertreatment system 62 can be an exhaust pipe 64 with one or more after-treatment devices 66.1 . 66.2 include. The aftertreatment devices 66.1 . 66.2 (together 66 ) can be any device that, thanks to its design, can change the composition of the exhaust gases. More details on the preferred aftertreatment devices 66 are listed below. As illustrated, the internal combustion engine includes 12 a high pressure short range exhaust gas recirculation (HP-EGR) circuit 68 that is between the exhaust manifold 58 and the intake manifold 44 is coupled. The HP EGR cycle 68 can be an EGR cooler 70 include the temperature of the exhaust gases in the EGR circuit 68 to lower. An HP EGR valve 72 regulates a high-pressure exhaust gas flow in the HP-EGR circuit 68 , The internal combustion engine 12 also includes a low pressure exhaust gas recirculation (LP-EGR) circuit 74 with the exhaust pipe 64 downstream of the turbine 54 is coupled and exhaust gases into the air intake duct 46 upstream of the compressor 52 returns. An LP EGR valve 76 regulates a low-pressure exhaust gas flow in the LP-EGR circuit 74 ,

The automotive system 10 can also an electronic control unit (ECU) 78 include that is associated with one or more sensors and / or devices associated with the ICE 12 assigned. The ECU 78 can be a digital central processing unit (CPU) in connection with a storage system or data carrier 80 and include an interface bus. The CPU is designed to carry out the instructions stored in the memory system as a program and via the Interface bus to send and receive signals. The storage system can have various types of storage, including optical storage, magnetic storage, solid state storage and other permanent storage. The interface bus can be designed to modulate analog and / or digital signals and to send them to the various sensors and control devices or to receive them from them. The program can embody the methods disclosed herein, which enables the CPU to perform the steps of these methods and the ICE 12 to control. Instead of an ECU 78 can the automotive system 100 have different processor types to control the electronic logic, e.g. B. provide an embedded controller, an on-board computer or any processing module that could be used in a motor vehicle.

The program stored in the storage system is transmitted externally via a cable or wirelessly. Outside the automotive system 10 it is normally visible as a computer program product, also referred to in the art as a computer readable medium or machine readable medium, and is to be understood as a computer program code that is on a carrier, the carrier being a volatile or non-volatile type with which Consequence that the computer program product can be regarded as volatile or non-volatile.

An example of a transitory computer program product is a signal, for example an electromagnetic signal, such as an optical signal, which is a transitory carrier for the computer program code. Such a computer program code can be carried by modulating the signal by a conventional modulation technique, such as QPSK for digital data, so that binary data representing the computer program code is impressed on the transitory electromagnetic signal. Such signals are used, for example, in the wireless transmission of computer program code over a Wi-Fi connection to a laptop.

In the case of a non-transitory computer program product, the computer program code is embodied in a material storage medium. The storage medium is then the non-transitory carrier mentioned above, so that the computer program code is stored permanently or not permanently available in or on this storage medium. The storage medium can be of a conventional type, as is known in computer technology, such as a flash memory, an Asic, a CD or the like.

The ECU 78 can receive input signals from various sensors that are configured to be related to various physical parameters related to the ICE 12 Generate signals. These sensors include an air mass and temperature sensor without restriction 82 , a manifold pressure and temperature sensor 84 , a combustion chamber pressure sensor 86 , a level and temperature sensor for coolant and oil 88 , a fuel rail pressure sensor 90 , a camshaft position sensor 92 , a crankshaft position sensor 94 , a differential pressure sensor 96 , an exhaust gas temperature sensor 98 , an EGR temperature sensor 100 and an accelerator pedal position sensor 102 , In addition, the ECU 78 Generate output signals for various control devices, the task of which is to control the operation of the ICE 12 heard, including without limitation combustion fuel injectors 26 , Throttle valves 48 , EGR valves 72 . 76 VGT actuator 60 , Cam adjuster 42 and aftertreatment injector 104 , It should be noted that the communication between the ECU 78 and the various sensors and devices is shown by dashed lines, but some are suppressed for a better overview.

With reference to 3 now becomes an aftertreatment system 300 according to the present disclosure. It should be noted that the aftertreatment system 300 the components and the configuration of the architecture for the in 1 shown aftertreatment system 62 describes in more detail. The aftertreatment system 300 includes a first pipe section 302 with a first end in fluid communication with the exhaust manifold 58 (shown in 1 ) and a second end in fluid communication with an inlet 304 a first aftertreatment device 306 , In the in 3 In the illustrated embodiment, the first aftertreatment device is a NOx storage catalyst (LNT) filter 306 , The LNT filter 306 is a catalyst system designed to reduce both particulate matter (PM) and nitrogen oxide (NOx) in a single unit. Further details of the LNT filter are listed below. Multiple sensors 310 . 312 . 314 are at the entrance 304 arranged and several sensors 316 . 318 . 320 are at the outlet 322 the first aftertreatment device 306 arranged and provide sensor signals to the ECU 78 to control the aftertreatment system 300 ready. These sensors include oxygen / NOx sensors (also known as lambda sensors) 310 , 320, exhaust gas temperature sensors 312 . 318 and differential pressure sensors 314 . 316 ,

A first AT (post-treatment) injection nozzle 308 is configured to add hydrocarbon (HC) fuel into the exhaust stream downstream of the exhaust manifold and independently of the fuel injectors 26 of the internal combustion engine 12 inject. As illustrated herein, the first AT injection is located 308 in the first pipe section 302 downstream of the turbocharger 50 , However, one skilled in the art should understand that this is the first AT fuel injector 308 in the exhaust system upstream of the turbocharger 50 can be located. The ECU 78 is connected to the first AT injector 308 for precise control of HC injections in the aftertreatment system 300 , Generally, the AT fuel injector has 308 similar components and functions as the combustion injectors 26 , except that it is designed to operate at a lower operating pressure. The implementation of a dedicated AT fuel injector instead of a post-injection strategy with the injectors 26 brings several decisive advantages for reducing fine dust and NOx production. Controlling the HC aftertreatment independently of combustion injections eliminates any practical operating range limitation that would otherwise be required in high injection post-injection strategies. Thus, HC emissions can be controlled by increasing the peak fat mixture frequency and the number of injections regardless of the combustion conditions. In addition, the AT fuel injector can be used in combination with multiple post-injections to reduce the possibility of oil dilution.

The aftertreatment system 300 includes a second pipe section 324 with a first end in fluid communication with an outlet 322 of lean NOx trap filter 306 and a second end in fluid communication with an inlet 326 a second aftertreatment device 328 , In the in 3 The embodiment shown is the second aftertreatment device 328 a selective catalytic reduction (SCR) unit. A second AT injector 330 is configured to introduce diesel exhaust fluid or urea (DEF) into the exhaust stream downstream of the first aftertreatment device 306 inject. The ECU 78 is connected to the second AT injector 330 for precise control of DEF injections in the aftertreatment system 300 , An oxygen / NOx sensor (also known as a lambda sensor) 332 is at the outlet 334 the second aftertreatment device 328 positions and provides sensor signals to the ECU 78 to control the aftertreatment system 300 ready. The aftertreatment system 300 includes a third pipe section 336 with a first end in fluid communication with the outlet 334 the second aftertreatment device 328 , The LP-EGR cycle 74 (shown in 1 ) is in fluid communication with the second pipe section 324 to some of the exhaust gas that passes through it to the intake manifold 44 is routed as previously described.

With reference to 4 now becomes an aftertreatment system 400 according to the present disclosure. It should be noted that the aftertreatment system 400 the components and the configuration of the architecture for the in 1 shown aftertreatment system 62 describes in more detail. The aftertreatment system 400 includes a first pipe section 402 with a first end in fluid communication with the exhaust manifold 58 (shown in 1 ) and a second end in fluid communication with an inlet 404 a first aftertreatment device 406 , In the in 4 The embodiment shown is the first aftertreatment device 406 a multi-function aftertreatment device with a diesel oxidation catalyst (DOC) section 406.1 upstream of a lean NOx filter (LNT) 406.2 , Multiple sensors 410 . 412 . 414 are at the entrance 404 arranged and several sensors 416 . 418 . 420 are at the outlet 422 the first aftertreatment device 406 arranged and provide sensor signals to the ECU 78 to control the aftertreatment system 400 ready. These sensors include oxygen / NOx sensors (also known as lambda sensors) 410 . 420 , Exhaust gas temperature sensors 412 . 418 and differential pressure sensors 414 . 416 ,

A first AT (post-treatment) injection nozzle 408 is configured to add hydrocarbon (HC) fuel into the exhaust stream downstream of the exhaust manifold and independently of the fuel injectors 26 of the internal combustion engine 12 inject. As illustrated herein, the first AT injection is located 408 in the first pipe section 402 downstream of the turbocharger 50 , However, one skilled in the art should understand that this is the first AT injector 408 in the exhaust system upstream of the turbocharger 50 can be located. The ECU 78 is connected to the first AT injector 408 for precise control of HC injections in the aftertreatment system 400 ,

The aftertreatment system 400 includes a second pipe section 424 with a first end in fluid communication with an outlet 422 the first aftertreatment device 406 and a second end in fluid communication with an inlet 426 a second aftertreatment device 428 , In the in 4 The embodiment shown is the second aftertreatment device 428 a selective catalytic reduction (SCR) unit. A second AT injector 430 is configured to introduce diesel exhaust fluid or urea (DEF) into the exhaust stream downstream of the first aftertreatment device 406 inject. The ECU 78 is connected to the second AT injector 430 for precise control of DEF injections in the aftertreatment system 400 , An oxygen / NOx sensor (also known as a lambda sensor) 432 is at the outlet 434 The second aftertreatment device 428 positions and provides sensor signals to the ECU 78 to control the aftertreatment system 400 ready. The aftertreatment system 400 includes a third pipe section 436 with a first end in fluid communication with the outlet 434 the second aftertreatment device 428 , The LP-EGR cycle 74 (shown in 1 ) is in fluid communication with the second pipe section 424 to some of the exhaust gas that passes through it to the intake manifold 44 is routed as previously described.

The one in the aftertreatment system 300 SCR unit used 328 and the diesel oxidation catalyst section 406.1 and those in the after-treatment system described above 400 SCR unit used 428 are adapted with conventional technology for the selective catalytic reduction and oxidation of compounds with a reducing character, such as hydrocarbons and sulfate particles. The further explanation of the substrates, catalytic treatments and regeneration processes is therefore not further discussed here.

With reference to 5 includes a lean NOx trap (LNT) filter 500 , represented by 306 in the aftertreatment system 300 and 406.2 in the aftertreatment system 400 , a housing 502 with an inlet 504 and an outlet 506 , The housing encloses a porous substrate 508 with inlet flow channels 5 10i that with outlet flow channels 510o are overlapped by the porous substrate 508 are limited. In this regard is an inlet flow channel 510i at one end 512 adjacent to the inlet 504 open and through a stopper 514 at one end 516 adjacent to the outlet 506 blocked. An outlet flow channel is reversed 510o through a stopper 518 at the end 512 adjacent to the inlet 504 blocked and in the end 516 adjacent to the outlet 506 open. The stoppers 514 . 518 are much less porous than the porous substrate 508 to ensure that the exhaust gas cannot flow through.

As in the 5 and 6A shown, this occurs through the LNT filter 500 flowing exhaust gas AG in an inflow channel 510i one and is through the porous substrate 508 and into an outflow channel 510o pressed. Depending on the differential pressures contained therein, the exhaust gas can flow through more than one inlet duct and / or one outlet duct. With reference to 6B forms the porous substrate 508 the substrate walls 520 and the inner pore surfaces 522 with a variety of internal pores 524 , the tortuous passages between the substrate walls 520 define. The porous substrate 508 is with a passive NOx adsorption catalyst 526 coated so that the substrate walls 520 and the inner pore surfaces 522 have an exposed catalyst layer. The conventional acid-based washcoat chemistry for a passive NOx adsorption catalyst (e.g. zeolite-based catalysts and / or alkali / alkali oxide components) can be used as a catalyst 526 can be used to adsorb NOx under lower temperature conditions, such as vehicle cold starts, and release NOx when the temperature of the exhaust gas rises without requiring a rich regeneration cycle. Other passive or partially active NOx adsorption catalysts that are effective to control NOx emissions during cold start and low temperature can act as a catalyst 526 implemented in the present disclosure.

In one embodiment, the concentration of the catalyst remains 526 on the substrate 508 in the exhaust gas flow direction over the length of the substrate 508 essentially constant so that it is generally evenly coated. In an alternative embodiment, the concentration of the catalyst 526 on the substrate 508 in the exhaust gas flow direction over the length of the substrate 508 are varied, these different zones based on the catalyst concentration in each region of the substrate 508 are defined. In other words, the substrate is zone coated to promote regeneration of the diesel particulate filter in this alternative embodiment.

The material of the porous substrate 508 is selected to filter (µm) particles in the exhaust gases with an aerodynamic diameter in the range of about 10 to 20 micrometers, which generally corresponds to the secondary grain size of the particles. Particles in the exhaust gases with an aerodynamic diameter larger than about 20 µm are at the interface of the substrate wall 520 filtered, ie in the inlet flow channels 510i locked in. Particles with an aerodynamic diameter of less than about 10 µm pass through the inner pores 524 of the substrate 508 , The deposition of the catalyst 526 on the inner pore surface 522 should be taken into account when selecting the material for the porous substrate with regard to the aforementioned filter function. In this regard, the average porosity of the coated substrate is no greater than a secondary grain size of the particles.

With reference to the 6A and 6B in the context of 3 and 4 Exhaust EG occurs at the inlet end 512 into the LNT filter 500 one and gets into the inlet flow channels 510i directed (one of which is shown). A hydrocarbon fuel can be used with the first AT injector 308 . 408 based on the chemical composition of the exhaust gas EG and the desired stoichiometry for the first aftertreatment device 306 . 406 be injected into the exhaust gas EG to promote both fine dust and NOx reduction. By using a dedicated injector, higher NOx conversion efficiency can be achieved without any potential limitation compared to conventional post-injection strategies. Hydrocarbon emissions can also be controlled by increasing the peak fat mixture frequency and number of injections with a dedicated injector, regardless of fuel injections for combustion. Furthermore, using a dedicated injector in combination with multiple post-injections can reduce the oil dilution that occurs in some conventional high-injection strategies after injection.

The course of fine dust PMc (> 20 µm) in the exhaust gas EG is on the substrate wall 520 blocked. The finer fine dust PM _F (10-20 µm) in the exhaust gas is in the inner pores 524 of the porous substrate 508 locked in. In addition, it adsorbs on the substrate walls 520 and the inner pore surfaces 522 deposited catalyst 526 NOx in the exhaust gas under cold start / low temperature operating conditions. A treated exhaust gas from which fine dust has been filtered and a reduction in the NOx concentration in the exhaust gas EG under cold start / low temperature operating conditions has been achieved is via the outlet 506 delivered downstream. At conventional engine operating temperatures, a thermal reaction reverses NOx adsorption on the catalyst 526 around. Thus, NOx that is in the first aftertreatment device 306 . 406 is included by the second aftertreatment device 328 . 428 directed. Since the aftertreatment system is at conventional engine operating temperatures, the SCR unit works 328 . 428 in the reduction and oxidation of NOx and other combustion by-products in the treated exhaust gas TEG.

The aftertreatment system works by using an LNT filter in combination with an SCR unit 300 . 400 over a wide temperature range from about 100 ° C to over 400 ° C. As is currently preferred, the first post-treatment device is 306 . 406 configured to have a NOx conversion efficiency of more than 40% in a first temperature range between about 100 ° C and 300 ° C and the second aftertreatment device 328 . 428 is configured to have a NOx conversion efficiency greater than 55% in a second temperature range between about 200 ° C and 450 ° C. The LNT filter 306 , 406.2 can simultaneously reduce particulates and NOx in a single unit with a smaller catalyst volume than a system with a separate lean NOx filter and diesel particulate filter. The LNT filter 306 . 406.2 is also advantageous compared to other devices in that the catalyst used therein does not collide with platinum group metals (PGMs) which would otherwise poison the catalyst used in a selective catalyst reduction filter (SCRF) unit. It also sees the configuration of an LNT filter 306 . 406.2 separate from the SCR unit 328 . 428 protection against damage to the DEF injector assembly 330 . 430 due to overtemperature conditions.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it is to be understood that there are a large number of variations. It is further understood that the exemplary embodiment or exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment (s). It is understood that various changes in the function and arrangement of elements can be made without departing from the scope of the disclosure as set forth in the appended claims and their legal equivalents.

Claims (10)

An aftertreatment system for an exhaust gas flow of an internal combustion engine having an exhaust manifold, the aftertreatment device comprising: a first pipe section configured to be in fluid communication with the exhaust manifold; a first aftertreatment device that includes a housing having an inlet and an outlet, a porous substrate with substrate walls that define a plurality of flow channels formed therein, including first channels that are blocked at a first end of the substrate and second channels that are on a second end of the substrate is blocked from the first end, wherein the first and second channels are interleaved and the inner pore surfaces in the porous substrate form a plurality of inner pores that define tortuous passages between the substrate walls and a passive NOx adsorption catalyst, which is deposited on the substrate walls and the inner pore surfaces so that the mean porosity of the porous substrate is not greater than a secondary particle size of the fine dust particles; a second aftertreatment device an inlet in fluid communication with the outlet of the first aftertreatment device. Aftertreatment system after Claim 1 wherein the porous substrate in the first post-treatment device has an average porosity of not less than 10 µm and not more than 20 µm. Aftertreatment system after Claim 1 wherein the porous substrate in the first aftertreatment device is evenly coated with the catalyst so that the concentration of the catalyst on the substrate in the exhaust gas flow direction remains substantially constant over the length of the substrate. Aftertreatment system after Claim 1 wherein the porous substrate in the first aftertreatment device is coated with the catalyst such that the concentration of the catalyst varies along the length of the substrate to define different zones based on the catalyst concentration in a particular area of the substrate. Aftertreatment system after Claim 1 , further comprising a diesel oxidation catalyst section disposed in the housing between the inlet and the porous substrate. Aftertreatment system after Claim 1 further comprising a fuel injector configured to inject a hydrocarbon fuel into the aftertreatment system downstream of the exhaust manifold and upstream of the first aftertreatment device. Aftertreatment system after Claim 1 wherein the second aftertreatment device includes a selective catalytic reduction (SCR) unit and a fluid injector configured to inject diesel exhaust fluid into the aftertreatment system downstream of the first aftertreatment device and upstream of the SCR unit. Aftertreatment system after Claim 1 wherein the first aftertreatment device has a NOx conversion efficiency greater than 40% in a first temperature range between about 100 ° C and 300 ° C and the second aftertreatment device has a NOx conversion efficiency greater than 55% in a second temperature range between about 200 ° C and 450 ° C. Aftertreatment system after Claim 1 , further comprising a second pipe section having a first end in fluid communication with the outlet of the first aftertreatment device and a second end in fluid communication with the SCR unit so that the second pipe section separates the first and second aftertreatment devices. Aftertreatment system after Claim 9 , further comprising a low pressure exhaust gas recirculation circuit in fluid communication with the second pipe section.

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