DE102018106092A1 - EXHAUST GAS TREATMENT FOR A COMBUSTION ENGINE - Google Patents

Abstract

An after-treatment system for an internal combustion engine includes a diesel cold start catalyst element, a lean NOx trap catalyst (LNT) element disposed immediately adjacent and downstream of the diesel cold start catalyst, and a selective catalytic reduction (SCR) element disposed downstream of the LNT. The diesel cold start catalyst is operable to reduce NOx emissions at operating temperatures below 200 ° C, and the LNT and SCR systems are operable to reduce NOx emissions at operating temperatures above 200 ° C.

Description

INTRODUCTION

The present disclosure relates to the art of aftertreatment systems, and more particularly to an aftertreatment system for a motor vehicle.

Internal combustion engines, when operated, often generate undesirable gases such as CO, CO2, NOx, and the like. Many countries have issued regulations that limit emissions from internal combustion engines. Various after-treatment systems have been introduced to reduce emissions. In many cases, existing aftertreatment systems operate under normal operating conditions. During normal operating conditions, the exhaust components were heated to operating temperatures that may exceed about 175 ° C.

New emission regulations are being introduced to handle emissions that may occur below normal operating temperatures. Current aftertreatment systems may use an electric heater arranged to heat an aftertreatment catalyst to reduce emissions during e.g. B. cold starts can be further reduced. Electric heaters add additional components that require periodic maintenance and increase the overall complexity of aftertreatment devices. Further, electric heaters require a warm-up time in which emissions may occur at altitudes that are not consistent with current and pending regulations. Accordingly, it is desirable to provide an aftertreatment system that operates during cold starts to reduce emissions of an internal combustion engine operating below normal operating temperatures.

SUMMARY

In an exemplary embodiment, an after-treatment system for an internal combustion engine includes a diesel cold start catalyst element, a lean NOx trap (LNT) lean element catalyst, and a selective catalyst reduction (SCR) element downstream of the LNT. The diesel cold start catalyst is operable to reduce NOx emissions at operating temperatures below 200 ° C, and the LNT and SCR systems are operable to reduce NOx emissions at operating temperatures above 200 ° C.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a Diesel Exhaust Fluid (DEF) injection system used to introduce a diesel exhaust fluid into exhaust gases generated by the internal combustion engine.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include those wherein the DEF injection system is downstream of the LNT and the SCR is upstream.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a transfer tube that fluidly connects the diesel cold start catalyst and the LNT to the SCR.

In addition to one or more of the features described above or below, or as an alternative, in other embodiments, the DEF injection system could be fluidly connected to the transfer tube.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include those in which the DEF (Diesel Exhaust Fluid) injection system includes urea injection.

In addition to one or more of the features described above or below, or as an alternative, further embodiments could include at least one O2 / NOx sensor and an exhaust gas temperature (EGT) sensor located in front of the diesel cold start catalyst, and at least one of O2 / NOx sensor and an EGT sensor located after the LNT.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a first differential pressure sensor (DPS) disposed in front of the SCR and a second DPS disposed after the SCR.

In addition to one or more of the features described above or below, or alternatively, embodiments may also include arrangements in which the diesel cold start catalyst and the LNT are disposed in a common housing.

In addition to one or more of the features described above or below, or as an alternative, others may be incorporated herein by reference Embodiments may also be a rear oxidation catalyst (ROC - Rear Oxidation Catalyst) arranged after the SCR.

In another aspect of the exemplary embodiment of the invention, a motor vehicle includes an internal combustion engine including an exhaust system and an aftertreatment system fluidly connected to the exhaust system. The aftertreatment system includes a diesel cold start catalyst (diesel cold start catalyst), a NOx trap catalyst element (LNT) disposed immediately adjacent and downstream of the diesel cold start catalyst, and a selective catalytic reduction (SCR) element located behind the LNT. The diesel cold start catalyst is operable to reduce NOx emissions at operating temperatures below 200 ° C, and the LNT and SCR systems are operable to reduce NOx emissions at operating temperatures above 200 ° C.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a Diesel Exhaust Fluid (DEF) injection system used to introduce a diesel exhaust fluid into exhaust gases generated by the internal combustion engine.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include those wherein the DEF injection system is downstream of the LNT and the SCR is upstream.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a transfer tube that fluidly connects the diesel cold start catalyst and the LNT to the SCR.

In addition to one or more of the features described above or below, or as an alternative, in other embodiments, the DEF injection system could be fluidly connected to the transfer tube.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include those in which the DEF (Diesel Exhaust Fluid) injection system includes urea injection.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a diesel exhaust fluid (DEF) injection system disposed after the LNT.

In addition to one or more of the features described above or below, or as an alternative, further embodiments could include at least one O2 / NOx sensor and an exhaust gas temperature (EGT) sensor located in front of the diesel cold start catalyst, and at least one of O2 / NOx sensor and an EGT sensor located after the LNT.

In addition to one or more of the features described above or below, or as an alternative, other embodiments could include a first differential pressure sensor (DPS) disposed in front of the SCR and a second DPS disposed after the SCR.

In addition to one or more of the features described above or below, or alternatively, embodiments may also include arrangements in which the diesel cold start catalyst and the LNT are disposed in a common housing.

The above features and advantages as well as other features and functions of the present disclosure will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.

list of figures

• 1 zeigt ein Kraftfahrzeug mit einem Abgasnachbehandlungssystem gemäß einem Aspekt einer exemplarischen Ausführungsform; und
• 2 ist ein Blockschaltbild, das ein Abgasnachbehandlungssystem gemäß einem Aspekt einer exemplarischen Ausführungsform zeigt.

Other features, advantages and details appear only by way of example in the following detailed description of the embodiments, the detailed description of which refers to the drawings, wherein:

• 1 shows a motor vehicle with an exhaust aftertreatment system according to an aspect of an exemplary embodiment; and
• 2 FIG. 10 is a block diagram showing an exhaust aftertreatment system according to an aspect of an exemplary embodiment. FIG.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure in its applications or uses. It should be noted that in all drawings the same reference numbers refer to the same or corresponding parts and features.

A motor vehicle according to one aspect of an exemplary embodiment is generally shown as 10 in FIG 1 specified. motor vehicle 10 is shown in the form of a small truck. It is understood that the motor vehicle 10 take various forms, including automobiles, commercial transports, maritime vehicles and the like. Motor vehicle 10 has a body 12 that have an engine room 14 , a passenger compartment 15 and a loading area 17 includes. In the engine compartment 14 is an internal combustion engine system 24, which in the embodiment shown, a diesel engine 26 can have. The internal combustion engine system 24 includes an exhaust system 30 fluidly with an exhaust aftertreatment system 34 connected is. The exhaust gas generated by the engine system 24 flows through the aftertreatment system 34 to reduce NOx emissions passing through an exhaust outlet pipe 36 can escape into the environment.

According to one aspect of an exemplary embodiment, as in 2 shown, the internal combustion engine system 24 a turbocharger 40 with a compressor section 42 and a turbine section 44 include. The compressor section 42 includes a compressor inlet 46, which may be fluidly connected to the environment, and a compressor outlet 47, which may be fluidly connected to an inlet (not separately referred to) of the diesel engine 26. The turbine section 44 includes a turbine inlet 49 fluidly connected to the exhaust system 30 and a turbine outlet 50 fluidly connected to the aftertreatment system 34 can be connected. The turbine outlet 50 delivers at least part of the through the turbocharger 40 flowing exhaust gases to the aftertreatment system 34 ,

In one aspect of an exemplary embodiment, the aftertreatment system 34 includes a diesel cold start catalyst element 60 and a lean NO _x trap (LNT) element 64, which are housed in a common housing 66 are arranged. Although arranged in a common housing, it is understood that the diesel cold-start catalyst element 60 and the LNT element 64 may exist in the common housing as separate components or building blocks. Further, it is understood that the diesel cold-start catalyst element 60 and the LNT element 64 each may comprise a unique substrate with a specific zone coating providing separation between the building blocks. The LNT element 64 is downstream of the diesel cold-start catalyst element 60, as will become apparent herein. Exhaust gases enter the LNT element 64 and increase its internal temperature after passing through the diesel cold-start catalyst element 60 were processed. The common housing 66 includes an inlet 69 fluidly with the turbine outlet 50 connected, and an outlet 71 fluidly connected to a transfer tube 74 connected is. The diesel cold start catalyst element 60 operates to reduce NOx emissions in exhaust gases having temperatures below about 200 ° C and the LNT element 64 works to reduce NOx emissions that may be present in exhaust gases at a temperature above about 200 ° C. In this way, the diesel cold-start catalyst element 60 and the LNT element operate 64 in parallel to reduce NOx emissions that may be present in exhaust gases from initial start up to normal operating conditions.

More specifically, the temperature of the exhaust gases emitted by the engine system 24 during initial cranking is typically below 200 ° C. The diesel cold-start catalyst element 60 may include a catalyst and / or a zeolite trap (not separately labeled) configured to reduce NOx emissions in exhaust gases at the tempering temperature. Exhaust gas temperatures begin to increase as the internal combustion engine system 24 continues to operate and the LNT element 64 is heated. As exhaust gas temperatures approach operating temperatures of about 200 ° C or higher, the diesel cold start catalyst element begins 60 to lose the NOx emission reduction efficiency. The LNT element 64 by that of the diesel cold start catalyst element 60 flowing exhaust gases is heated, but has reached an effective operating temperature. When the effectiveness of the diesel cold start catalyst element 60 As such, the LNT element 64 as such decreases to further reduce NOx emissions.

In further accordance with an exemplary aspect, a transfer tube 74 includes an inlet section 77 fluidly connected to the outlet 71 is connected, and an outlet section 79 fluidly with a selective catalytic reduction (SCR) system 84 connected is. SCR system 84 may also take the form of a SCRF system incorporating a diesel particulate filter system. SCR system 84 processes those from the LNT element 64 flowing exhaust gases to further reduce emissions. SCR system 84 includes an inlet section 86 fluidly connected to the outlet section 79 of the transfer tube 74 and an outlet section 88 connected to a rear oxidation catalyst (ROC). 91 may be connected through an exhaust pipe 94. ROC 91 is fluidic with the exhaust outlet pipe 36 and operates to oxidize gases such as CO, HC and NH3, which can be transmitted by the SCR system 84.

In still further accordance with one aspect of an exemplary embodiment, a diesel exhaust fluid (DEF) injection system 114 after the LNT element 64 and before the SCR system 84 be arranged. DEF injection system 114 can be selectively controlled to introduce an amount of diesel exhaust fluid into the exhaust gases passing through, for example, the transfer tube 74 stream. In one aspect of an exemplary embodiment, the DEF injection system includes 114 a urea injection. It is understood that the DEF injection system 114 may be configured to introduce a large range of diesel exhaust fluids into the exhaust gases entering the transfer tube 74. The introduction of diesel exhaust fluid may be based on inputs from various sensors connected to the aftertreatment system 34 are controlled in order to further reduce emissions, in particular NO _x .

In still further accordance with an exemplary aspect, the aftertreatment system 34 may include a first O ₂ / NOx sensor 124 located in the inlet 69 of the common housing 66 and a second O ₂ / NOx sensor 125 located at the outlet 71 of the common housing 66 is arranged. In addition, a first exhaust gas temperature sensor (EGT) 130 in the inlet 69 and a second EGT sensor 131 arranged at the outlet 71. In addition, a first differential pressure sensor (DPS) 134 at the inlet portion 86 of the SCR system 84 arranged and a second DPS 135 is at the outlet portion 88 of the SCR system 84 arranged. Each of the above sensors may be connected to a controller (not shown) that may be used to control aspects of the turbocharger 40, such as the wastegate position, the DEF injection system 114 and the same.

It is understood that exemplary embodiments describe a system for reducing NOx emissions generated by an internal combustion engine during both a cold start period and under normal operating conditions. The diesel cold-start catalyst element (Diesel cold-start catalyst) of the present invention is positioned such that both the exhaust gases during a cold start or gases at temperatures below about 200 ° C to be processed and a preheat for a downstream positioned lean _NOx -Speicherkatalysatorelement is provided. In this way, the exemplary embodiment eliminates the need for electrical pre-heaters that must be operated to preheat the LNT element. Further, the particular arrangement of components provides a broader range of emission reduction, including cold start, for example below about 200 ° C, and normal operation, eg, exhaust temperatures above about 200 ° C, to meet new emissions regulations.

The term "about" is intended to include the degree of error associated with the measurement of the particular amount based on the equipment available at the time of filing the application. For example, "about" may include a range of ± 8% or 5% or 2% of a given value. Further, the term "about" should be understood to represent a general indication of temperature values, as certain temperature values may depend on various system limitations, materials used, and the like.

While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and the individual parts may be substituted with corresponding other parts without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular material situation to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the specific embodiments disclosed, but that it also include all embodiments falling within the scope of the application.

Claims (10)

Exhaust after-treatment system for an internal combustion engine, comprising: a diesel cold start catalyst element; a lean NOx storage catalyst (LNT) element disposed immediately adjacent and after the diesel cold start catalyst; and a Selective Catalytic Reduction (SCR) element disposed after the LNT wherein the diesel cold start catalyst can reduce NOx emissions at operating temperatures below 200 ° C and the LNT and SCR systems can reduce NOx emissions at operating temperatures above 200 ° C , Aftertreatment after Claim 1 , further comprising: a diesel exhaust fluid (DEF) injection system operable to introduce a diesel exhaust fluid in exhaust gases generated by the internal combustion engine. Aftertreatment after Claim 2 wherein the DEF injection system is located after the LNT and before the SCR. Aftertreatment after Claim 2 , further comprising: a transfer tube, the Diesel cold start catalyst and LNT with the SCR fluidly connects. Aftertreatment after Claim 3 wherein the DEF injection system is fluidly connected to the transfer tube. Aftertreatment after Claim 2 wherein the DEF injection system comprises a urea injection. Aftertreatment after Claim 1 , further comprising: at least one of an O2 / NOx sensor and an exhaust gas temperature (EGT) sensor disposed in front of the diesel cold-start catalyst and / or at least one of an O2 / NOx sensor and an EGT sensor disposed after the LNT. Aftertreatment after Claim 1 , further comprising: a first differential pressure sensor (DPS) disposed in front of the SCR and a second differential pressure sensor disposed after the SCR. Aftertreatment after Claim 1 wherein diesel cold start catalyst and LNT are arranged in a common housing. Aftertreatment after Claim 1 , further comprising: a rear oxidation catalyst (ROC) disposed after the SCR.

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