AFTERTREATMENT DEVICE HAVING AN IMPROVED INLET CONE

Abstract

An aftertreatment device is provided for purifying exhaust gases of an internal combustion engine for an automotive vehicle. The aftertreatment device includes a catalyst substrate and an inlet cone from which exhaust gases reach the catalyst substrate. The inlet cone includes a baffle accommodated inside the inlet cone and configured to realize a flow uniformity index, representing the percentage of utilized catalyst volume, higher than a flow uniformity index threshold.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Great Britain Patent Application No. 1404786.4, filed Mar. 17, 2014, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application pertains to an aftertreatment device for purifying exhaust gases of an automotive vehicle having an internal combustion engine, and more particularly an inlet cone for the aftertreatment device.

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 may be a ceramic monolith with a honeycomb structure, carrying the catalytic layer or coating. The aftertreatment systems may be any device configured to change the composition of the exhaust gases. Examples of such aftertreatment devices include: a diesel oxidation catalyst (DOC) located in the exhaust line for degrading residual hydrocarbons (HC) and carbon oxides (CO) contained in the exhaust gas; and a Lean NO_x 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 (NO_x) from the diesel engine exhaust gas. These systems are provided with aftertreatment devices installed along the exhaust line of the engine and typically include a diesel particulate filter (DPF) for control of particulates, and selective catalytic reduction (SCR) system for NO_x control.

Typically an aftertreatment device includes an inlet cone through which exhaust gases enter the device. The catalytic converter consists of a catalyst substrate or core, which may be a ceramic monolith with a honeycomb structure. The monolith is coated with a complex substance, the so-called wash coat. A wash coat 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 wash coat prior to applying to the core.

One task of the aftertreatment system is to achieve a flow uniformity index as highest as possible. Uniformity index indicates how the flow is distributed inside the housing of the device. From a mathematical point of view the uniformity index can be defined as follows:

$UI=1-\frac{1}{2A\stackrel{\_}{V}}\int \left(V-\stackrel{\_}{V}\right)A$

where:
UI=flow uniformity index;
A=surface of the first layer of cells in the catalyst substrate;
V=exhaust gas speed; and
V=exhaust gas average speed.
A good flow uniformity index is particularly important for closely coupled aftertreatrnent devices which are accommodated close the engine. As a result, the shape of the device is often dictated by the engine geometrical constraints.

In fact, the flow uniformity index is an important parameter, which tells how much the core, and in particular the wash coat and precious metals inside the housing is used. The flow uniformity index (UI) indicates the percentage of the core volume, which is used to reduce emission.

Unfortunately, above all for closely coupled aftertreatrnent devices, the standard target of the uniformity index, which is around 0.9, is often difficult to achieve, due to packaging constraints, which impose the shape of the device. Therefore a need exists for a design of an aftertreatment device that overcomes the above inconvenience.

SUMMARY

In accordance with the present disclosure, an aftertreatment device is provided having an input cone which improves the exhaust gas distribution inside the substrate of the device of an aftertreatment device for an internal combustion engine. An embodiment of the disclosure provides an aftertreatment device tier purifying exhaust gases of an automotive vehicle having an internal combustion engine. The aftertreatment device includes a catalyst substrate and an inlet cone from which exhaust gases reach the catalyst substrate. The inlet cone includes a baffle, accommodated inside the inlet cone and 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 includes consists in improving the flow uniformity index on the core, in other words, increasing the uniformity index over the target of 0.9. As a result a better use of the precious metals in the catalyst is achieved which leads to an improved conversion efficiency of the aftertreatment device.

According to another embodiment of the present disclosure, the baffle is a shaped metal sheet. An advantage of this embodiment is that the shaped metal sheet separates 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 the cross section, formed by the inlet cone and the inner cone which is preferably a substantially annular circular crown, achieves a more uniform gas flow.

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

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.

FIG. 1 is a schematic view of an aftertreatment system;

FIG. 2 is a aftertreatment device;

FIG. 3 shows the exhaust gas distribution inside the inlet cone of a conventional aftertreatment device;

FIG. 4 shows the exhaust gas distribution inside the inlet cone of an aftertreatment device according to an embodiment of the present disclosure;

FIG. 5 is the inlet cone of an aftertreatment device according to another embodiment of the present disclosure; and

FIG. 6 is a cross section of the embodiment of FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the present disclosure or the following detailed description.

Some embodiments may include an internal combustion engine (ICE) 110, as shown schematically in FIG. 1. The internal combustion engine 110 includes an exhaust system 270 having an exhaust pipe 275 with one or more exhaust aftertreatment systems 280. The aftertreatment systems 280 may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment systems 280 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 (SCR) systems 283, particulate filters (DPF) 284 or a combination of the last two devices, i.e. selective catalytic reduction system including a particulate filter (SCRF).

FIG. 2 shows an aftertreatment device 280 with its inlet cone 285 and the catalyst substrate housing 286. FIG. 3 shows the exhaust gas distribution inside the inlet cone of the aftertreatment device according to a conventional design of the inlet cone. As can be observed, the gas flow 300 does not have a uniform distribution in the inlet cone 285, 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 closely 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 disclosure, a feature is introduced inside the inlet cone to address and drive the gas flow from the outlet of the turbocharger area to the core, so that the core volume can be utilized as much possible. In this regard, a baffle, located inside the inlet cone improves the uniformity index.

FIG. 4 shows the exhaust gas distribution inside the inlet cone of an aftertreatment device according to an embodiment of the present disclosure. 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 UI_thr, which is 0.9.

FIG. 5 is the inlet cone according to another embodiment of the present disclosure. The baffle is realized as an inner cone 330. Preferably, the inner cone 330 can be realized in a metallic material and can have the shape of the inlet cone such as 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 inlet cone 285 and the inner cone 220 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 UI_thr, which is 0.9.

Summarizing, the disclosed aftertreatment system shows the following remarkable advantages. The flow uniformity index on the core has been improved, i.e. increased over the target 0.9. As a result, an improved conversion efficiency for an aftertreatment device such as a diesel oxidation catalyst or a lean NO_x trap is achieved. In this way, the available space for a closely coupled catalytic device can be used in a more effective way.

While at least one exemplary embodiment has been presented in the foregoing 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 of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an 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 of the present disclosure as set forth in the appended claims and their legal equivalents.

Claims

1-5. (canceled)

6. 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 directing exhaust gases to the catalyst substrate, and a baffle accommodated inside the inlet cone and configured to realize a flow uniformity index (UI), which represents a percentage of utilized catalyst volume, higher than a flow uniformity index threshold (UIthr).

7. The aftertreatment device according to claim 6, wherein the flow uniformity index is defined as follows: U   I = 1 - 1 2   A  V _  ∫ ( V - V _ )   A the flow uniformity index threshold is 0.9.

where:

UI=flow uniformity index;

A=surface of the first layer of cells in the catalyst substrate;

V=exhaust gas speed; and

V=exhaust gas average speed; and

8. The aftertreatment device according to claim 6, wherein the baffle comprises a shaped metal sheet.

9. The aftertreatment device according to claim 6, wherein the baffle comprises an inner cone.

10. The aftertreatment device according to claim 9, wherein the inner cone is downscaled with respect to the inlet cone.

11. The aftertreatment device according to claim 9 wherein a cross section between the inlet cone and the inner cone is substantially the same width along a circumference.

12. An internal combustion engine equipped with an aftertreatment device according to claim 6.