GB2524258A

GB2524258A - Aftertreatment device having an improved inlet cone

Info

Publication number: GB2524258A
Application number: GB1404786.4A
Authority: GB
Inventors: Domenico Spatafora
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2014-03-17
Filing date: 2014-03-17
Publication date: 2015-09-23
Also published as: GB201404786D0; US20150260073A1; CN204552897U

Abstract

An aftertreatment device for purifying exhaust gases of a vehicle internal combustion engine. The aftertreatment device comprises a catalyst substrate and an inlet cone 285 from which exhaust gases reach the catalyst substrate. The inlet cone comprises a baffle 330 accommodated inside the inlet cone, and configured to realize a flow uniformity index (Ul), representing the percentage of utilized catalyst volume, higher than a flow uniformity index threshold. The baffle may be a shaped metal sheet, or an inner cone which is downscaled with respect to the inlet cone.

Description

AFTER TREA TMENT DEVICE HAVING AN IMPROVED INLET CONE

TECHNICAL FIELD

The present disclosure relates to an aftertreatment device for purifying exhaust gases of an automotive vehicle having an internal combustion engine, the aftertreatment device having an improved inlet cone.

BACKGROUND

It is known that modern engines are provided with one or more exhaust aftertreatment systems, also called catalytic converters. In general, a catalytic converter consists of a catalyst substrate or core, which is usually a ceramic monolith with a honeycomb structure, carrying the catalytic layer or ccating. The aftertreatment systems may be any device configured to change the composition of the exhaust gases. Example of them are a diesel oxidation catalyst (DCC) located in the exhaust line for degrading residual hydrocarbons (HC) and carbon oxides (CC) contained in the exhaust gas; a Lean NO Trap (LNT), which is provided for trapping nitrogen oxides NO contained in the exhaust gas and is located in the exhaust line.

Further examples are exhaust gas aftertreatment systems for the emissions reduction and in particular of particulates and oxides of nitrogen (NOx) from the diesel engine exhaust gas. These systems are provided with aftertreatment devices installed along the exhaust line of the engine and typically comprise a diesel particulate filter (DPF) for control of particulates, and selective catalytic reduction (8CR) system for NOx control.

Typically an aftertreatment device comprises an inlet cone through which exhaust gases enter the device. The catalytic converter consists of a catalyst substrate or core, which is usually a ceramic monolith with a honeycomb structure. The monolith is coated with a complex substance, the so-called washcoat. A washcoat is a carrier for the catalytic materials and is used to disperse the materials over a high surface area. Aluminum oxide, titanium dioxide, silicon dioxide, or a mixture of silica and alumina can be used.

The catalytic materials (precious metals, such as platinum, palladium and rhodium) are suspended in the washcoat prior to applying to the core.

One of the aftertreatment system task is to achieve a flow uniformity index as highest as possible. Uniformity index means how the flow is well distributed inside the canned brick of the device. From a mathematical point of view the uniformity index can be defined as follows: uic -2Av " where: UI = flow uniformity index A = surface of the first layer of cells in the catalyst substrate v = exhaust gas speed v = exhaust gas average speed A good flow uniformity index is particularly important for close coupled aftertreatment devices: these devices are accommodated close the engine and therefore their shape is often imposed by the engine geometrical constraints.

In fact, the flow uniformity index is an important parameter, which tells how much the brick inside is used, in other words, wasftcoat and precious metals. The flow uniformity index (UI) indicates the percentage of the brick volume, which is used to reduce emission.

Unfortunately, above all for close coupled aftertreatment devices, the standard target of the uniformity index, which s around 0.9, is often difficult to achieve, due to packaging constraints, which impose the shape of the brick.

Therefore a need exists for a new design of an aftertreatment device which overcomes the above inconvenience.

An object of this invention is to provide an aftertreatment device having a new feature improving the exhaust gas distribution inside the substrate of the device.

These objects are achieved by an aftertreatment device and by an internal combustion engine.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides an aftertreatment device for purifying exhaust gases of an automotive vehicle having an internal combustion engine, the aftertreatment device comprising a catalyst substrate and an inlet cone from which exhaust gases reach the catalyst substrate, wherein the inlet cone comprises a baffle, accommodated inside the inlet cone, configured to realize a flow uniformity index, representing the percentage of utilized catalyst volume, higher than a flow uniformity index threshold.

An advantage of this embodiment consists in improving the flow uniformity index on the brick, in other words, increasing the uniformity index over the target of 0.9. This means a better use of the precious metals in the catalyst and consequently leads to an improved conversion efficiency of the aftertreatment device.

According to another embodiment of the invention, the baffle is a shaped metal sheet.

An advantage of this embodiment is that the shaped metal sheet allows to separate the exhaust gas flow in two sub-volumes, this improving the uniformity index.

According to a further embodiment, the baffle is an inner cone.

According to an aspect of this embodiment the inner cone is downscaled with respect to the inlet cone.

An advantage of this embodiment is that being the cross section, formed by the inlet cone and the inner cone substantially an annular circular crown, the gas can flow in a more uniform way.

According to another embodLment, the disclosure provides an internal combustion engine equipped with an aftertreatrnent device according to any of the previous embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example1 with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an aftertreatment system.

Figure 2 is a generic aftertreatment device.

Figure 3 shows the exhaust gas distribution inside the inlet cone of an aftertreatment device according to the state of the art.

Figure 4 shows the exhaust gas distribution inside the inlet cone of an aftertreatment device according to an embodiment of the present invention.

Figure 5 is the inlet cone of an aftertreatment device according to another embodiment of the present invention.

Figure 6 is a cross section of the embodiment of Fig. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Some embodiments may include an internal combustion engine (ICE) 110, as schematized in Fig. 1, comprising an exhaust system 270. The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment systems 280.

The aftertreatment systems may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment systems 260 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts (DOC) 281, lean NOx traps (LNT) 282, hydrocarbon adsorbers, selective catalytic reduction (5CR) systems 283, particulate filters (DPF) 284 or a combination of the last two devices, i.e. selective catalytic reduction system comprising a particulate filter (SCRF).

Fig. 2 shows a generic aftertreatment device 280 with its inlet cone 285 and the catalyst substrate 286. Figure 3 shows the exhaust gas distribution inside the inlet cone of the aftertreatment device according to a standard design of the inlet cone, As can be observed, the gas flow 300 does not have a uniform distribution in the inlet cone, but is much more concentrated in a specific volume 310, having a high density flow. This leads to a low uniformity index. In fact, the uniformity index is strongly related to the shape of the inlet cone of the close coupled aftertreatment device. To define a good shape of the inlet cone, addressing the flow in a proper way, a lot of space would be needed. This is not possible since the internal combustion engine needs to be as compact as possible.

Therefore, the uniformity index has to be improved independently from the shape of the inlet cone.

According to an embodiment of the present invention, the idea is to introduce a feature inside the inlet cone to address and drive the gas flow from the outlet of the turbocharger area to the brick, so that the brick volume can be utilized as much possible. A baffle, located inside the inlet cone is the solution to improve the uniformity index.

Figure 4 shows the exhaust gas distribution inside the inlet cone of an aftertreatment device according to an embodiment of the present invention. In this case the baffle is realized by a shaped metal sheet 320, which is accommodated inside the inlet cone. As can be observed, the gas flow 300 has a more a uniform distribution in the inlet cone and the flow uniformity index UI can be higher than the desired threshold Ulthr, which is 0.9.

Figure 5 is the inlet cone according to another embodiment of the present invention, wherein the baffle is realized as an inner cone 330. Preferably, the inner cone can be realized in a metallic material and can have the shape of the inlet cone, in other words can be a downscaled inlet cone. As can be seen from Fig. 5 and Fig. 6, which is a cross section of the embodiment of Fig. 5, the gas can flow in the volume between the inlet cone 285 and the inner cone 330. Having the cross section between the two cones substantially the same width along a circumference, in other words, being the cross section substantially an annular circular crown, the gas can flow in a more uniform way.

Also with this embodiment, the flow uniformity index UI can be higher than the desired threshold Ulmr. which is 0.9.

Summarizing, the disclosed aftertreatment system shows remarkable advantages: the flow uniformity index on the bricks has been improved, i.e. increased over the target 0.9; this leads to an improved conversion efficiency for a generic aftertreatment device, i.e. a diesel oxidation catalyst or a lean NOr trap; finally, the available space for a close coupled catalytic device can be used in a more effective way.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS

internal combustion engine 270 exhaust system 275 exhaust pipe 280 aftertreatment systems 281 diesel oxidation catalyst (DOC) 282 lean NOx trap (LNT) 283 selective catalytic reduction (SCR) system 284 particulate filters (DPF) 285 inlet cone of the aftertreatment device 286 catalyst substrate 300 flow direction 310 high density flow volume 320 shaped metal sheet 330 inner cone UI flow uniformity index Ulthr flow uniformity index threshold A volume of the first layer of cells in the catalyst substrate V exhaust gas speed v exhaust gas average speed

Claims

CLAIMS1. Aftertreatrnent device (281, 282, 283, 284) for purifying exhaust gases of an automotive vehicle having an internal combustion engine, the aftertreatment device comprising a catalyst substrate (286) and an inlet cone (285) from which exhaust gases reach the catalyst substrate, wherein the inlet cone comprises a baffle (320, 330), accommodated inside the inlet cone, configured to realize a flow uniformity index (UI), representing the percentage of utilized catalyst volume, higher than a flow uniformity index threshold (Ulmr).
2. Aftertratment device according to claim 1, wherein the baffle is a shaped metal sheet (320).
3. Aftertratment device according to claim 1, wherein the baffle is an inner cone (330).
4. Aftertratment device according to claim 3, wherein the inner cone (330) is downscaled with respect to the inlet cone (285).
5. Internal combustion engine (110) equipped with an aftertreatment device (281, 282, 283, 284) according to any of the preceding claims.