BRPI0315118B1 - converter device to be arranged in an exhaust system of a combustion engine - Google Patents

Abstract

The container arrangement is for incorporation in the exhaust gas system of an internal combustion engine and comprises an outer casing (1) enclosed by a tubular body (4) and a passage for conducting exhaust gases through the container. The passage has a first part extent (17a) located externally around the tubular body, a second part extent (17b) located inside the tubular body and a third part extent (17c) which handles the flow of exhaust gases between the first and second part extents. The third part extent incorporates at least one flow path, which constitutes an extended flow extent for exhaust gases in relation to a straight-line radial flow between the first and second part extents.

Description

BACKGROUND OF THE INVENTION AND BACKGROUND OF THE INVENTION The invention relates to a converter device to be arranged in an exhaust system for a combustion engine.

In the coming years we will see increasingly stringent requirements being introduced, at least in Europe, regarding emissions from diesel vehicles. Increasingly stringent requirements for effective exhaust gas purification are also being met for combustion engines other than diesel engines. In order to meet these emission requirements, combustion engine powered vehicle exhaust systems are being equipped with catalysts, which among other things reduce the amount of nitrogen oxides, and with particulate filters that reduce the amount of particulate matter. soot in the exhaust. Such exhaust gas purification components function largely as a low pass filter. This means that low frequency sound, which is the predominant element in exhaust noise, passes almost unmuted through the exhaust gas purification components. This makes it necessary that an additional muffling volume be added to the exhaust system to compensate for the volume occupied by the particulate filter and catalytic scrubber in the exhaust system. Such a converter device will therefore be relatively elongated and thereby occupy a large amount of space in the vehicle.

SUMMARY OF THE INVENTION The object of the present invention is to provide a converter device which has suitable sonic muffling characteristics with respect specifically to low frequency noise in an exhaust system for a combustion engine while at the same time being attractive from the viewpoint. occupied, flexible and easy to maintain. The stated objective above is achieved with the device mentioned in the introduction which is characterized by what is indicated in the characterizing part of claim 1.

Achieving adequate muffling of low-frequency engine noise from a combustion engine usually requires an elongated passage leading the exhaust through the converter device. As the passage according to the present invention comprises a first outer part around from the tubular body and a second part internal to the tubular body, the result is a substantially two-way exhaust gas flow in the converter device. Such a two-way flow provides a relatively long exhaust passage through the converter device, thereby automatically providing relatively adequate sonic muffling of low frequency noise. A properly shaped passageway results in two-way flow in the converter device with relatively little flow resistance. With a properly shaped passageway, the flow resistance need not be much higher than in a conventional converter device with a substantially direct exhaust passage. Introducing a flow path that provides the exhaust gas with a greater flow distance than a substantially straight radial flow between the first outer portion and the second inner portion further extends the passage without having to increase the length of the converter device. The converter device according to the present invention thus provides a long exhaust passage within a short, compact structure which provides very adequate muffling of low frequency motor noise.

According to a preferred embodiment of the present invention, the positioning of the flow path is such as to connect a first space and a second space of the passageway. A basic principle for drowning out low frequency noise is to create a long exhaust line between two relatively large spaces. An effective low-frequency noise damper with a conventional straight flow path between two exhaust spaces represents a considerable length and thus takes up a lot of space. Proper positioning of the flow path between two such spaces in the converter device results in a converter device with a short and compact structure which at the same time exhibits adequate sonic muffling characteristics.

According to another preferred embodiment of the invention, the flow path has a spiral extension. Such a spiral path may have a relatively large outside diameter resulting in the flow path being considerably longer than a substantially rectilinear radial flow path between the first portion outside the barrel and the second portion disposed within the barrel. A spiral flow path can be made very compact and can have a major radial plane extension. Such a spiral flow path means that the converter device can be made very short and compact despite constituting a considerable length passage for the exhaust gases. A spiral flow path also provides substantially optimal smooth control of exhaust flow. Flow losses in the flow path in this way can be kept at a low level.

According to another preferred embodiment of the present invention, the flow path exhibits a spiral extension of · 180 ° to 1080 °. A spiral flow path needs, for example, to extend only one turn to cover considerable length and provide adequate sonic muffling. The flow path can display at least one part with one. area in variable cross section. The cross-sectional area of the flow path can be varied to achieve controlled muffling of exhaust noise and flow resistance. The cross-sectional area may, for example, comprise an increasing cross-sectional area in the exhaust flow direction. A cross-sectional area in the flow direction reduces the velocity of the exhaust. The resistance to flow through the flow path in this way will be low.

According to another preferred embodiment of the present invention, the flow path comprises at least one profiled section which has a spiral extension. Such a profiled section may be elongated and exhibit a length corresponding to the length of the flow path. The profiled section in this way forms a wall surface of the flow path. The third part may comprise n flow paths formed by n profiled sections which are offset 360 ° / n from each other. Advantageously, at least two flow paths are used to make it easier for exhaust gases to flow through them. The two flow paths preferably have their respective inputs and outputs offset 180 ° from each other. The result is a substantially equal distribution of the exhaust between the two flow paths. To further facilitate the distribution of exhaust gases between different flow paths, the number of flow paths may be increased additionally. Three or more of such flow paths advantageously have their inlets and outlets offset from one another according to the above formula to distribute the exhaust gases evenly among the various flow paths. The length of the third part can also be increased in this way.

According to another preferred embodiment of the present invention, the exhaust gases must be driven through the passage in a direction such that they first flow through the first radially located off-pipe part before they flow through the second inside-pipe part. . Such an exhaust flow direction through the passage has several advantages. Among other things, it makes the constituent parts of the converter device relatively easier to assemble, facilitating flow path design for effective sonic muffling and simplifying the arrangement of any possible burner at the inlet of the passage. Such a burner is intended when necessary to raise the temperature of the exhaust gas before it reaches the particulate filter. In order for the soot particles in the exhaust to ignite and burn in the particulate filter, the exhaust must reach a specific temperature.

According to another preferred embodiment of the present invention, the flow path comprises a detachable module. Such a module makes it easy for the flow path to be mounted and disassembled in the converter device. Such modules may advantageously be manufactured in various versions and sizes. The modules may thus comprise different number and different number flow paths suitable for combustion engines of different types and sizes. The detachable module preferably comprises an enclosure end wall. Such a module substantially forms a side cover which is easy to assemble and remove.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the invention is described below, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates a converter device according to the present invention, Figure 2 illustrates a section along line AA in Figure 1, Figure 3 illustrates a section along line B ~ B in Figure 1, Figure 4 illustrates a section along line C ~ C in Figure 1 and Figure 5 illustrates only one module comprising a spiral flow path .

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF

INVENTION Figure 1 illustrates a converter device to be arranged in an exhaust system for a diesel vehicle. The converter device comprises an outer housing 1 which has a substantially cylindrical shape. In Figure 1, the portion of the casing 1 facing the observer has been removed to show the items disposed within the casing 1. The casing 1 forms a closed outer surface separated from the points where an inlet 2 and an outlet 3 are arranged for the exhaust gases. A pipe 4 of circular cross-section is disposed within the housing 1 so that center lines through the housing 1 and pipe 4 coincide. The length of barrel 4 is such that it extends from a first end wall 5 of housing 1 to a module compreende which comprises a second end wall 6 of housing 1. The converter device comprises purifying components. exhaust to purify the exhaust gases flowing through a passageway extending between inlet 2 and outlet 3. A first exhaust purification component in the form of a particulate filter 7 is arranged externally at. around pipe 4. Figure 2 illustrates a section along line AA in Figure 1. It shows a particle filter 7 extending annularly around pipe 4. Particle filter 7 has such a radial extension that it fills the radial space between the pipe 4 and the housing 1. The particulate filter 7 comprises elongate ducts having an extension in a first direction 8. The elongate ducts must conduct the exhaust through the particle filter 7. The particle filter 7 has a constant cross-sectional shape in the exhaust flow direction. Exhaust gases are therefore driven substantially in the first direction 8 through the particle filter 7. Particle filter 7 comprises limiting surfaces 9 arranged at appropriate points along the length of the elongate ducts. The limiting surfaces cause the exhaust gases to be driven 9 into adjacent elongate ducts in the particle filter. Soot particles are thus trapped and burned in the particle filter 7. A second exhaust purification component in the form of a catalytic purification 10 is disposed within tube 4. Catalytic purifier 10 is disposed radially within particulate filter 7. Catalytic scrubber 10 also comprises elongate ducts for conducting exhaust gases substantially in a second direction 11 through catalytic scrubber 10. Catalytic scrubber 10 has a constant cross-sectional shape in exhaust gas flow direction 11. . Catalytic scrubber 10 should perform catalytic purification of the exhaust gas, particularly to reduce the nitrogen oxide content of the exhaust gas passing through it. Particle filter 7 has a larger cross-sectional area than catalytic scrubber 10 in plane A shown in Figure 2. The result is that the exhaust gases have a lower velocity through particulate filter 7 than through catalytic scrubber 10. The flow resistance of the exhaust gas is related to its flow velocity. Due to the limiting surfaces 9, the exhaust gas flow resistance is usually higher in the particulate filter 7 than in the catalytic scrubber 10. Decreasing the flow velocity through the particulate filter 7 can considerably reduce the total flow resistance through the particulate filter. passage. The cross-sectional area of the particulate scrubber 7 is preferably double that of catalytic scrubber 10.

A basic principle for drowning out low frequency noise is to create a long escape route between two spaces. An effective low-frequency noise damper in which such an escape route is straight takes up a lot of space. A low frequency sound is the predominant element in noise from a combustion engine. The converter device comprises sonic damping means designed in accordance with this basic principle. The converter device thus comprises two profiled sections 12a, b which extend in a spiral. In this case each of the profiled sections 12a, b extends approximately 1.5 turns, i.e. 540 °. The two profiled sections 12a, b form spiral flow wall surfaces for two paths 13a, b whose inlets and outlets are offset 180 ° from each other. Spiral paths 13a, b are disposed within module M. Exhaust gases are driven in radially inwardly through a third portion 17c of the passageway comprising spiral flow paths 13a, b from a first portion 17a of passage which is situated outside of pipe 4 to a second part 17b of the passage which is located within pipe 4. The space in the passage outside of pipe 4 upstream of the flow paths 13a, b is a first space and the space a Downstream from the flow paths 13a, b within the pipe constitutes a second space. Conducting the exhaust gases into the spiral flow paths 13a, b with a radial extension results in a long exhaust route without the converter device having to be elongated in shape. The converter device which thus comprises the exhaust purification components as well as the sonic muffler components, therefore, can be made very compact and take up little space while at the same time having very suitable sonic muffler characteristics.

A burner 14 may, if necessary, be arranged in the vicinity of input 2 for the converter device. The purpose of the burner 14 is to heat the exhaust to a temperature such that the soot particles can burn in the particulate filter 7. Soot particles usually ignite at a temperature of around 600 ° C, but in most cases it is difficult to guarantee such a high exhaust temperature even with a high performance burner. The ignition temperature of the soot particles must therefore normally be decreased. This can be achieved by converting the various types of N0X nitrogen oxides that arise into NO2 nitrogen oxide. There are basically two methods to achieve this. According to a first method, CRT (Continuous Regeneration Collector), a separate oxidation catalytic scrubber is disposed for this purpose prior to filter 7 of; particles in the direction of exhaust gas flow. In this situation, soot particles ignite at approximately 225 ° C in the particle filter 7. According to a second method, CSF (Catalytic Soot Filter), the particulate filter 7 is coated with a suitable coating material so that oxidation catalysis from NOx to NO2 occurs directly on the surface of particulate filter 7. . In this case soot particles ignite at approximately 250 ° C. It is also possible through various additives in the fuel if a reduced ignition temperature of approximately 350 ° C is achieved in a conventional particulate filter 7.

In cases where a catalytic filter 10 which works by SCR (Selective Catalytic Reduction) is used, injection devices 15 are arranged on the periphery of converter 1 to add an ammonia-containing substance, for example in the form of urea. When the ammonia-containing substance has been added, it must be adequately mixed if it is to optimize the performance of the catalytic filter 10 in reducing to nitrogen gas and water the nitrogen and ammonium oxide content of the exhaust gases passing through it. With the elongated spiral flow paths 13a, 13b, this is no problem.

Exhaust gases are led into the converter device via inlet 2. Figure 3 illustrates a section BB through the converter device inlet 2. The exhaust gases are driven from inlet 2 to the first part 17a of the passage, which exhibits a substantially annular space extending externally around the tube 4. The annular space of the first passage portion 17a provides relatively little resistance to flow, to the flowing exhaust gases, and transmits to the exhaust gas a substantially uniform distribution before them. be driven in an axial direction out of pipe 4 towards particle filter 7. Before the exhaust gases reach the particulate filter 7, they are heated as required by the burner 14 to such a temperature as to ensure ignition and combustion in the particulate filter 7 of the soot particles in the exhaust gas. The exhaust gases are conducted in a first direction 8 through the elongated ducts of the particulate filter 7. The boundary surfaces 9 arranged at suitable points along the elongate ducts in the particle filter 7 force the exhaust gases into adjacent elongate ducts. Depending on the regeneration system and temperature, the soot particles trapped at this stage in the particle filter 7 ignite and burn. Exhaust gases are thus forced to deviate laterally for a shorter distance, but mainly flow in the first direction 8 along a substantially straight line through the particle filter 7. Exhaust gases flowing out of the particle filter 7 were, in principle, purified from soot particles.

Exhaust gases flowing out of the particulate filter 7 have a substance in the form of an ammonia carrier added to them by injection devices 15 before they reach the M module. The M module is illustrated separately in Figure 5. The M module comprises a wall surface 18 which seals abutting the pipe 4 in a radially internal region. The wall surface 18 comprises a first inlet 19a through which exhaust gases are led into first flow path 13a, and a second inlet 19b through which exhaust gases are led into second path 13b flow. Spiral section sections 12a, b which are partially discernible in diagrammatic form of the first and second flow paths 13a, b. The modulus unit M thus also comprises the second end wall 6 and an outer radial region 20 of the housing 1. The modulus unit M is detachably mounted, for example by fastening straps, in a suitably suitable manner together. with the other parts of the converter device. Exhaust gases are conducted radially into module M via one of the two flow paths 13a, b which are formed by spiral shaped sections 12a, b. The inlets 19a, b of the two flow paths 13a, b are 180 ° offset from each other, resulting in a substantially equal distribution of exhaust gases between the two flow paths 13a, b. Exhaust gases successively driven in radially inwardly by the spiral flow paths 13a, b of the third passage part 17c have a considerably longer transport route than a substantially rectilinear radial flow between the first passage part 17a situated outside the passageway. barrel 4 and its second part 17b situated within barrel 4. The spiral flow paths 13a, b constitute an elongated escape route connecting two spaces of the passage so that effective low frequency noise sonic muffling is obtained from of the diesel engine. The elongated flow paths 13a also provide a necessary mixing distance for the ammonia carrier so that the ammonia carrier becomes substantially evenly distributed in the exhaust. Exhaust gases are subject to relatively slight changes in direction as they pass through the spiral flow paths 13a, b thereby reducing flow resistance. The result in spiral flow paths 13a, b is flow in a plane that is substantially perpendicular to the first flow direction 8 and the second exhaust flow direction 11. Exhaust gases flowing out of the spiral paths are led into pipe 4. Exhaust gases flowing out of the flow paths 13a, b are received into the centrally located space 21 of module M before being led into the pipe. pipe 4 and toward catalytic scrubber 10. When exhaust gases flowing within pipe 4 reach catalytic scrubber 10, they flow into the elongate ducts of the latter. The elongated ducts allow the exhaust to flow in the second flow direction 11 which is parallel but in the opposite direction to the first flow direction 8. In catalytic scrubber 10, the nitrogen and ammonium oxides contained in the exhaust gas are reduced to nitrogen gas and water. Thereafter, the scape gases, substantially free of soot particles and nitrogen oxides, flow out through the outlet 3. The outlet 3 comprises a well rounded tapered shape that connects pipe 4 to a narrower pipe of the exhaust system. The narrower barrel 4 is not illustrated in the drawings. The shape of the outlet 3 means that the exhaust gases are again subjected to very little flow resistance.

The flow paths 13a, b are thus comprised within a separate detachable module M which is easy to remove and remove. This means that the end wall 6 and the spiral flow paths 13a, b may be mounted as a unit. Such M modules can be manufactured in various versions and sizes. M modules comprising flow paths differing in number, length and cross-sectional area may thus be mounted on the converter device, depending among other things on the type and size of the combustion engine. Assembly of the module can be by means of fastening straps. The invention is by no means limited to the described embodiment, but may be freely varied within the scope of the claims. For example, the flow paths need not necessarily have a spiral length but may have a curved length of substantially any desired shape so as to result in a longer exhaust gas route than a substantially rectilinear radial flow. The exhaust gases may alternatively be conducted in an opposite direction so that they first flow through the pipe 4 on the inner side before being radially outwardly directed through the flow paths 13a, b to a final flow outside the pipe. 4. In such a case the particulate filter 7 is disposed inside the pipe 4 and the catalytic scrubber 10 outside the pipe 4. The housing 1, the exhaust purification components 7, 10 and the pipe 4 need not necessarily be circular in however, they may be substantially of any desired functional shape. Neither does barrel 4 need to be centrally disposed within housing 1, but it can have substantially any desired functional positioning.

Claims (11)

1. A converter device to be arranged in a combustion engine exhaust system, the converter device of which comprises an external housing (1); a tubular body (4) which is enclosed by the housing (1); and a passageway for conducting the exhaust gas through the converter device, the passageway comprising a first part (17a) located externally around the tubular body (4), a second part (17b) situated within the tubular body (4) and a third portion (17c) providing exhaust flow in a radial direction between the first portion (17a) and the second portion (17b) of the passageway, characterized in that the third portion comprises at least one pathway (13a). b) flow which provides exhaust gases with a longer flow path than a substantially rectilinear radial flow between the externally located first portion (17a) and the internally located second portion (17b) of the passageway. Converter device according to claim 1, characterized in that the positioning of the flow path (13a, b) is such as to connect a first space and a second passage space. Converter device according to claim 1 or 2, characterized in that the flow path (13a, b) has a spiral extension. Converter device according to claim 3, characterized in that the flow path (13a, b) has a spiral extension of 180 ° to 1080 °. Converter device according to any one of the preceding claims, characterized in that the flow path (13a, b) exhibits at least a portion with a variable cross-sectional area. Converter device according to any one of the preceding claims 3-5, characterized in that the flow path (13a, b) comprises at least one profiled section (12a, b) which has a spiral extension. Converter device according to any one of the preceding claims, characterized in that the third part (17a) of the passage comprises n flow paths (13a, b) formed by n profiled sections (12a, b) which are offset by 360 ° / n from each other. Converter device according to claim 7, characterized in that n is greater than 2 or equal to 2. Converter device according to any one of the preceding claims, characterized in that the exhaust gases must be conducted through the passage in a direction such that they first flow through their first part (17a) before flowing through them. its second part (17b). Converter device according to any one of the preceding claims, characterized in that the flow path (13a, b) is comprised within a separate detachable module (M). Converter device according to claim 10, characterized in that the detachable module (M) comprises at least one end wall (6) of the housing (1).