Patent Application
20150260073
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.
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.
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 NOx 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 include a diesel particulate filter (DPF) for control of particulates, and selective catalytic reduction (SCR) system for NOx 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:
where:
UI=flow uniformity index;
A=surface of the first layer of cells in the catalyst substrate;
V=exhaust gas speed; and
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.
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.
The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.
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
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.
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 NOx 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1404786.4 | Mar 2014 | GB | national |
