LU101556B1

LU101556B1 - Catalytic converter inlet cone baffle

Info

Publication number: LU101556B1
Application number: LU101556A
Authority: LU
Inventors: Daryl Harris
Original assignee: Katcon Global Sa
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-06-22

Abstract

The present invention discloses a diffuser element to be used in an internal combustion engine exhaust line upstream of a catalytic converter, the diffuser element comprising a catalytic converter inlet cone adapted to connect a housing surrounding a catalytic converter substrate and an exhaust gas inlet pipe coming from the internal combustion engine and a baffle plate arranged inside the catalytic converter inlet cone to face the incoming exhaust gas flow and presenting a plurality of openings. According to the invention, the openings of the baffle plate are circular openings of the same diameter, preferably having a diameter comprised between 5 and 11 mm, more preferably equals to 8 mm and the circular openings are arranged in a regular pattern over substantially the entire surface of the baffle plate, said openings defining an open area corresponding to 40-80% of the surface of the baffle plate, preferentially corresponding to 50-70% of the surface of the baffle plate, more preferably the open area equals 58% of the surface of the baffle plate.

Description

| P-KATCON-009/LU 1 LU101556 Catalytic converter inlet cone baffle Technical field

[0001] The present invention generally relates to catalytic converters used in internal combustion engine exhaust lines, and more particularly to catalytic converters including an inlet diffuser. Background of the Invention

[0002] A motor vehicle exhaust line generally comprises a collector, an inlet pipe, an exhaust gas catalytic converter and an outlet pipe connected in series so that the exhaust gas coming out of the internal combustion engine of a vehicle flows through these elements prior to being released outside. The catalytic converter used in such an exhaust line is used to decrease exhaust emissions by converting carbon monoxide and unburned hydrocarbons to more innocuous compounds. When used in a gasoline engines, a catalytic converter is also used to convert nitrogen oxides and is called a Three-Way Catalyst or TWC. The catalytic converter includes a substrate which carries a catalyst for converting the exhaust gas. Suitable catalysts are known to those skilled in the art and include for example platinum-containing compositions and should be used in the most efficient manner. Thus, it is important to adjust the exhaust gas flow characteristics to provide a uniform distribution across the substrate cross-section. A uniform exhaust gas flow distribution at the substrate inlet face is also desirable because it leads to the smallest pressure loss across the converter for a given substrate geometry and engine flow. High pressure loss leads directly to increased engine back pressure which results in reduced engine power at high load and reduced fuel economy.

[0003] Conventionally, mixing devices presenting different angled and orientated blades such as the one described in document US 2015/0315943 A1 are inserted into the inlet pipe upstream of the converter to disrupt the exhaust gas flow and evenly distribute it across the catalyst. But these mixing devices are very sensitive to upstream changes, e.g. changes in the exhaust gas flow rate or the inlet pipe length, and require major design changes in order to work efficiently with different engines.

[0004] Inlet diffusers provide for more generic exhaust gas flow distribution devices. US patent US 10,227,908 B2 discloses an inlet diffuser for exhaust gas aftertreatment systems. The diffuser presents a plurality of openings formed through its front side, wherein the openings include a first plurality of openings formed through a proximal portion of the diffuser and a second plurality of openings formed through a distal portion of the diffuser. Exhaust gas flow is restricted through the second plurality of openings relative to flow through the first plurality of openings, which leads to an increased engine back pressure and can reduce engine power.

Object of the invention

[0005] Therefore, it is an object of the present invention to provide an inlet diffuser for use in the inlet pipe of a catalytic converter which is less sensitive to variations of exhaust gas flow rates and inlet pipe lengths, simpler to fabricate and presents no negative impact on the exhaust back pressure.

General Description of the invention

[0006] In conventional catalytic converters used in internal combustion engine exhaust lines, the catalytic converter substrate is carried by a housing having a cross-sectional area substantially greater than that of the exhaust pipe running from the internal combustion engine to the catalytic converter. Accordingly, catalytic converters are often built with a converter inlet cone. The inlet cone has a larger cross-sectional area at one end where it is connected to the housing surrounding the catalytic converter substrate and a smaller cross-sectional area at the other end where the inlet cone is connected to the exhaust pipe coming from the internal combustion engine.

[0007] The present invention proposes a diffuser element to be used in an internal combustion engine exhaust line upstream of a catalytic converter, the diffuser element comprising: - a catalytic converter inlet cone adapted to connect a housing surrounding a catalytic converter substrate and an exhaust gas inlet pipe coming from the internal combustion engine; and - a baffle plate arranged inside the catalytic converter inlet cone to face an incoming exhaust gas flow from the exhaust gas inlet pipe and presenting a plurality of openings.

[0008] The diffuser element object of the present invention is characterised in that the openings of the baffle plate are circular openings of the same size, preferably the circular openings have a diameter comprised between 5 and 11 mm, more preferably equal to 8 mm and the circular openings are arranged in a regular pattern over substantially the entire surface of the baffle plate, said openings defining an open area corresponding to 40-80% of the surface of the baffle plate, preferentially corresponding to 50-70% of the surface of the baffle plate, more preferably the open area equals 58% of the surface of the baffle plate.

[0009] The inlet cone may be a conventional inlet cone to avoid unnecessary production costs and facilitate the use of a baffle plate according to the present invention in already existing combustion engine exhaust lines. In particular, the inlet cone may offer either a gradual enlargement or an abrupt enlargement of the diameter of the exhaust gas inlet pipe towards the diameter of the housing surrounding the catalytic converter substrate.

[0010] The number of circular openings on the baffle plate is defined according to their size in order to provide an open area of the desired size compared to the surface of said baffle plate. In embodiments, the baffle plate may present 35 to 55 circular openings, and in preferred embodiments, the baffle plate may present 46 ciruclar openings.

[0011] The purpose of the openings in the baffle plate is to help equally distribute the incoming exhaust gas flow over the inlet face of the catalytic converter substrate, in order to ensure that the exhaust gas is flowing through all of the cells in the substrate. Both the baffle plate and the openings restrict the exhaust gas flow and split it into multiple streams in order to evenly distribute it across the iniet face of the catalytic converter substrate, thus ensuring an optimized action of the catalytic coating in the different substrate cells on the exhaust gas flow.

[0012] Contrary to conventional diffuser designs which are very sensitive to changes in gas flow rates and inlet pipe lengths, the diffuser element subject- matter of the present invention can be used without substantial changes in its design to accommodate different engines, with different exhaust gas flow rates and different inlet pipe lengths.

[0013] Surprisingly, the baffle plate design and its open area are able to achieve the required uniformity of flow distribution across the inlet face of the catalytic converter substrate without a negative impact on the exhaust back pressure across the catalytic converter.

[0014] Advantageously, the circular openings of the baffle plate are arranged in a regular pattern with a triangular pitch defining a kind of "hexagonal close packed" arrangement, but any other pattern may be considered, depending on the application, to achieve an optimal open area maintaining backpressure and flow performance.

[0015] In embodiments, the baffle plate has a roughly triangular shape and preferably, the baffle plate presents the shape of an equilateral triangle.

[0016] The use of a triangular baffle plate allows a circulation of the exhaust gas flow around said baffle plate in addition to a flow circulation through its openings. Moreover, exhaust gases may flow more easily around the baffle plate than through its openings. It is interesting to allow for an easier gas flow at the periphery of the inlet pipe where gas flow rates are generally lower than at the center of the inlet pipe, as it helps developing a flat and uniform gas flow rate profile upstream of the catalytic converter substrate.

[0017] Moreover, the roughly triangular shape of the baffle plate makes it possible to position said plate within the inlet cone, as the vertices of the triangle provides support points for the baffle plate inside the inlet cone. Furthermore, the use of a baffle plate with the shape of an equilateral triangle facilitates the installation of said baffle plate inside the inlet cone, as the plate presents no preferred orientation, but a person skilled in the art will know that any symmetrical shape such as round, square, octagonal or hexagonal can be considered.

[0018] Preferentially, the thickness of the baffle plate is comprised between 1 and 3 mm, more preferably corresponds to 1.5 mm. Such thickness of the baffle plate ensures a sufficient rigidity in order for the baffle plate not to be deformed by the pressure resulting from the exhaust gas flow while the plate remains thin enough to prevent any increase of the exhaust back pressure across the catalytic converter.

[0019] In embodiments, the baffle plate is inserted inside the catalytic converter inlet cone so as to be substantially perpendicular to the direction of the incoming exhaust gas flow. However, the direction normal to the baffle plate may form an angle a with the direction of the incoming exhaust gas flow up to 10° without modifying the performances of the diffuser element so that the baffle plate surface may be tilted compared to the catalytic substrate surface. In other words, the direction normal to the baffle plate may form an angle a with the direction of the incoming exhaust gas flow, the angle a being preferentially comprised between 0° and 10°, more preferably a equals 0°.

Preferentially, the position of the baffle plate inside the catalytic converter inlet cone is adapted for the downstream exhaust gas flow to meet an uniformity index at 10 mm from the surface of the catalytic converter substrate of at least 90%, preferentially of at least 95%, more preferably of 98%. In embodiments, the position of the baffle plate in the inlet cone is defined as the positon at which the inner diameter of the inlet cone corresponds to the biggest dimension of the triangular baffle plate. The baffle plate may be positioned 50 mm to 20 mm away from the surface of the catalytic converter substrate, more preferably 35 mm away In such embodiments, the position of the baffle plate in the inlet cone is defined as the positon at which the inner diameter of the inlet cone corresponds to the biggest dimension of the triangular baffle plate.

[0020] The position of the baffle plate in the inlet cone and the angle of the plate relative to the exhaust gas flow are functional considerations to help optimize the exhaust gas flow uniform distribution, and a person skilled in the art would know how to adapt these parameters to different combustion engine exhaust lines having different inlet pipe and different inlet cone so as to maintain a substantially equivalent uniformity index at 10 mm from the surface of the catalytic substrate.

[0021] Advantageously, the baffle plate is fixedly mounted inside the inlet cone. The baffle plate is preferentially welded to the inside of the inlet cone but any mean known to a skilled person can be used, such as clipping or form-fitting said baffle plate. Securing the baffle plate inside the inlet cone prevents any fall,

displacement or tilting from the baffle plate, thus ensuring constant performances of the diffuser element over the entire lifetime of the exhaust gas system.

[0022] The baffle plate of the diffuser element object of the present invention may be made of steel, preferentially sheet steel, as sheet steel is extremely strong, resistant to harsh environments and high temperatures, and is also malleable, so that the baffle plate may be made by stamping.

[0023] It will be appreciated that the present invention also relates to an exhaust gas system comprising an inlet pipe, a catalytic converter and a diffuser element as previously defined, said diffuser element being arranged between the inlet pipe and the catalytic converter.

Brief Description of the Drawings

[0024] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein: Fig.1 is a schematic side view of one embodiment of the diffuser element of the present invention; Fig. 2 is a schematic perspective view of the diffuser element of Fig.1; and Fig. 3 is another schematic perspective view of the diffuser element of Fig.1. Description of Preferred Embodiments

[0025] Fig.1 illustrates a schematic side view of an embodiment of a diffuser element 10 according to the present invention. Exhaust gas from the combustion engine is directed through an exhaust gas inlet pipe 12 with is connected to a catalytic converter 14. The catalytic converter comprises two main parts: a housing 16 and a catalytic substrate 18.

[0026] The terms "catalytic substrate" must be understood in a broad sense and may denote the use of a whole set of catalytic substrates and not only one, without limiting the scope of the presently described invention.

[0027] The housing 16 carries the catalytic substrate 18 and presents a larger cross-section than the inlet pipe 12. A catalytic converter inlet cone 20 is used to connect the housing 16 and the inlet pipe 12. The inlet cone 20 acts as a shape converter between two sections having different diameters. The inlet cone 20 presented in this preferred embodiment offers a gradual enlargement of the diameter of the inlet pipe 12 towards the diameter of the catalytic converter housing 16, but other types of inlet cones, such as inlet cones offering an abrupt pipe enlargement may also be used.

[0028] A baffle plate 22 is inserted inside the inlet cone 20. The baffle plate 22 has a roughly triangular shape as detailed on Fig. 2 and presents a plurality, namely forty-six circular openings 24.i having a diameter of 8 mm. The circular openings 24.i are arranged according to a regular pattern with a triangular pitch over substantially the entire surface of the baffle plate 22, defining a kind of "hexagonal close packed" arrangement. The baffle plate 22 presents a height of 84 mm so that the circular openings 24.i define an open area corresponding to 58% of the surface of the baffle plate 22.

[0029] In the present embodiment, the baffle plate 22 is made from sheet steel having a thickness of 1.5 mm using stamping but a person skilled in the art will know that other materials may be suitable and can adapt the machining method to the considered material.

[0030] The baffle plate 22 is inserted inside the inlet cone 20 so as to be substantially perpendicular to the direction of the incoming exhaust gas flow, but the direction normal to the baffle plate may form an angle a with the direction of the incoming exhaust gas flow up to 10° without modifying the performances of the diffuser element. In the present embodiment, the angle a approximately equals 7°. The surface of the baffle plate 22 is thus tilted compared to the inlet surface 28 of the catalytic substrate. The position of the baffle plate 22 in the inlet 20 cone depends on the dimensions of said plate and said cone, so that said position is defined as the positon at which the inner diameter of the inlet cone 20 corresponds to the height of the triangular baffle plate 22. In the present embodiment, the baffle plate 22 is positionned 35 mm away from the surface of the catalytic converter substrate.

[0031] Fig.2 and Fig.3 illustrate schematic perspective views of the diffuser element 10 of Fig.1. The baffle plate 22 presents the shape of an equilateral triangle with truncated vertices. The baffle plate 22 is dimensioned so that gaps

30.i are formed on at least one portion of each side of the triangular baffle plate between said sides and the inside wall of the inlet cone 20. Furthermore, the dimensions of the baffle plate 22 allow the truncated vertices to provide support points for the baffle plate 22 against the inside of the inlet cone 20.

[0032] The truncated vertices of the baffle plate are preferably welded to the inlet cone to ensure the fact that the baffle plate will stay in position during operation, but a person skilled in the art will know that the fixing of the baffle plate inside the inlet cone can be achieved through clipping, form-fitting or any other means.

List of Reference Symbols Diffuser element 12 Inlet pipe 14 Catalytic converter 16 Housing 18 Catalytic substrate Inlet cone 22 Baffle plate

24.1 Openings in the baffle plate 26 Fixing point of the baffle plate inside the inlet cone 28 Inlet surface of the catalytic substrate

30.i Gaps between baffle plate and inlet cone a Inclination angle of baffle plate

Claims

1. A diffuser element to be used in an internal combustion engine exhaust line upstream of a catalytic converter, the diffuser element comprising: - a catalytic converter inlet cone adapted to connect a housing surrounding a catalytic converter substrate and an exhaust gas inlet pipe coming from the internal combustion engine; and - a baffle plate arranged inside the catalytic converter inlet cone to face an incoming exhaust gas flow and presenting a plurality of openings; characterised in that the openings of the baffle plate are circular openings of the same size, preferably the circular openings have a diameter comprised between 5 and 11 mm, more preferably equal to 8 mm and the circular openings are arranged in a regular pattern over substantially the entire surface of the baffle plate, said openings defining an open area corresponding to 40- 80% of the surface of the baffle plate, preferentially corresponding to 50-70% of the surface of the baffle plate, more preferably the open area equals 58% of the surface of the baffle plate.

2. The diffuser element according to claim 1, wherein the circular openings of the baffle plate are arranged in a regular pattern with a triangular pitch defining a kind of "hexagonal close packed" arrangement.

3. The diffuser element according to any of the preceding claims, wherein the baffle plate has a roughly triangular shape, preferably the shape of an equilateral triangle.

4. The diffuser element according to any of the preceding claims, wherein the thickness of the baffle plate is comprised between 1 mm and 3 mm, preferably corresponds to 1.5 mm.

5. The diffuser element according to any of the preceding claims, wherein the direction normal to the baffle plate forms an angle a with the direction of the incoming exhaust gas flow, and wherein the angle a is comprised between 0° and 10°, preferably a equals 0°.

6. The diffuser element according to claim 5, wherein the position of the baffle plate inside the catalytic converter inlet cone is adapted for the downstream exhaust gas flow to meet an uniformity index at 10 mm from the surface of the catalytic converter substrate of at least 90%, preferentially of at least 95%, more preferably of 98%.

7. The diffuser element according to any of the preceding claims, wherein the baffle plate is fixed inside the inlet cone, preferentially by welding.

8. The diffuser element according to any of the preceding claims, wherein the baffle plate is made of sheet steel.

9. The diffuser element according to any of the preceding claims, wherein the baffle plate is made by stamping.

10. An exhaust gas system comprising an inlet pipe, a catalytic converter and a diffuser element according to any of the preceding claims, said diffuser element being arranged between the inlet pipe and the catalytic converter.