GB2523084A

GB2523084A - An exhaust mixing device

Info

Publication number: GB2523084A
Application number: GB1401938.4A
Authority: GB
Inventors: Aurelio Sculto
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2014-02-05
Filing date: 2014-02-05
Publication date: 2015-08-19
Also published as: GB201401938D0

Abstract

An exhaust mixing device 600 for an internal combustion engine comprises an external pipe 605, an internal beaker-shaped body 606 axially accommodated inside the pipe, an annular inter-space 615 defined there between, and a mixing chamber 620 defined inside the body between a front end 607 and an open rear end 608 thereof. A connection rim 609 is located at the rear end of the body to close the inter-space, and a plurality of holes 650 are provided in a lateral wall of the body to connect the mixing chamber with the inter-space. A turbulator 655 comprising holes 665 and a swirler 660 may be provided at the front end of the body. An injector 675 may inject fluid into, or upstream of, the mixing chamber. The device may be used to mix exhaust gas with Urea upstream of a selective catalytic reduction (SCR) device, or with unburnt fuel to regenerate a Diesel particulate filter (DPF).

Description

AN EXHAUST MIXING DEVICE

TECHNICAL FIELD

The present disclosure relates to an exhaust mixing device which is destined to be installed in an exhaust system of an internal combustion engine, in order to uniformly mix the ex-haust gases coming from the engine with another fluid, such as for example unburned fuel (Hydrocarbons -HG) or Diesel Exhaust Fluid (DEF).

BACKGROUND

It is known that an internal combustion engine generally comprises an engine block defin-ing one or more cylinders, each of which is closed by a cylinder head and accommodates a reciprocating piston that cooperates with the cylinder head to define a combustion cham-ber. A fuel and air mixture is cyclically disposed in the combustion chamber and ignited, thereby resulting in hot expanding exhaust gasses causing reciprocal movement of the piston that rotates a crankshaft. Afier the expansion, the exhaust gases exit the combus- tion chamber and are directed into an exhaust system, which generally includes an ex-haust pipe having one or more aftertreatment devices configured to filter and/or change the composition of the exhaust gases, such as for example an Oxidation Catalyst (DOG), a Particulate Filter (DPF), a Lean NO Trap (LNT), and/or a Selective Catalytic Reduction (SCR) system.

In order to guarantee and/or restore the effi ciency of some of these aftertreatment devices, it may be necessary to mix the exhaust cases coming from the engine with an additive fluid. For example, the particulate matter that progressively accumulates inside a particu-late filter (DPF) must be periodically removed to prevent the pressure drop across the filter from becoming excessive. This process, which is conventionally known as bPF regener-ation, is achieved by increasing the temperature of the exhaust gases entering the DPF (typically up to 630°C), which in their turn heat the filter up to a temperature at which the accumulated particulate burns off. A known strategy to increase the exhaust gas temper-ature provides for the exhaust gases to be mixed with a certain amount of unburned fuel (HG) that oxidizes in the oxidation catalyst, thereby heating the exhaust gases that subse-quently pass through the DPF. The unburned fuel may come from the engine cylinder thanks to the so called post-injections or may be supplied by means of a dedicate fuel injector, which may be located directly in the exhaust pipe, upstream of the DOC.

Another example of mixing can be found in the SCR systems, which generally comprise an SCR catalyst located in the exhaust pipe downstream of an SCR injector provided for injecting in the exhaust pipe a Diesel Exhaust Fluid (DEF), typically a solution of Urea, which mixes with the exhaust gases to be absorbed inside the SCR catalyst, where the nitrogen oxides (NOr) contained in the exhaust gases are converted into diatomic nitrogen and water.

In both these examples, best results are achieved when the additive fluid, namely the un-burned fuel (HC) or the Diesel Exhaust Fluid (DEF), vaporizes as much as possible before reaching the correspondent catalyst, respectively the DOC and the SCR catalyst, and when this vapor is mixed with the exhaust gases as uniformly as possible, in order to be absorbed by a large portion of the catalyst inlet face. However, achieving a high vaporiza-tion rate and a high vapor uniformity at the inlet face of the catalyst is often very difficult, because it generally requires to locate the injector of the additive fluid at a large distance from the catalyst (in order to increase the mixing length along the exhaust pipe), which is usually not feasible due to packaging constraints.

To overcome this drawback, it is currently known to locate one or more mixers in the ex- haust pipe, between the injector of the additive fluid and the correspondent catalyst, de-pending on the available mixing length. Each of these mixers is generally embodied as a stationary swirler, namely a sort of stationary vane wheel that radially deviates the oncom-ing exhaust gases, thereby generating a turbulence that enhance the mixing of the additive fluid, particularly in the cross stream direction. This solution represents a good trade-off between mixing effect, pressure drop and cost, but it still does not achieve an optimum in terms of fluid vaporization and uniformity of the vapor distribution at the inlet face of the catalyst.

SUMMARY

In view of the above, an object of the present invention is that of providing a mixing device that may have better performances than the known mixers with particular regard to mixing effect and back pressure. Another object is that of reaching this goal with a simple, rational and rather inexpensive solution. These and other objects are achieved by the embodi-ments of the invention as defined in the independent claims. The dependent claims define preferred or particularly advantageous aspects of the embodiments of the invention.

In particular, an embodiment of the invention provides an exhaust mixing device for an internal combustion engine, comprising an external pipe, an internal beaker-shaped body axially accommodated inside the external pi oe, an interspace defined between the external pipe and a lateral wall of the beaker-shaped body, a mixing chamber defined inside the beaker-shaped body between a front end and a rear open end thereof, a connection rim located at the rear open end of the beaker-shaped body to close the interspace, and a plurality of holes realized in the lateral wall of the beaker-shaped body to connect the mix-ing chamber with the interspace.

Thanks to this solution, the exhaust gases that flow through the external pipe of the mixing device reach first the front of the beaker-shaped body, which is located upstream of the rear open end with respect to the direction of the gas flow. The front end of the beaker-shaped body deviates at least part of the oncoming exhaust gases into the interspace surrounding the lateral wall, where they are forced by the connection rim to enter into the mixing chamber through the holes. Passing through these holes, the stream of exhaust gases deviates from the axial direction of the external pipe and acquires a velocity having a radial component, thereby generating in the mixing chamber a zone of recirculation. Due to this zone of recirculation, the mixing device is advantageously capable of enhancing the mixing of the exhaust gases with any addwve fluid added thereto, particularly in terms of vaporization and uniform distribution, without causing an excessive back pressure that otherwise could reduce the engine performance and increase the fuel consumption.

According to an aspect of the invention, the axes of the holes may be inclined with respect to a central longitudinal axis of the mixing chamber, in order to aid the flowing of the ex-haust gas thereby reducing the back pressure.

According to another aspect of the invention, the mixing chamber may be additionally con-nected with the internal volume of the external pipe through a turbulator provided in the front end of the beaker shaped body. A turbulator may be any device that increases the turbulence of a fluid that passes through it. In this way, part of the exhaust gases that run into the front end of the beaker-shaped body enters the internal pipe directly through the turbulator, which generates a zone of turbulence in the mixing chamber just upstream the zone of recirculation, thereby advantageously enhancing the vaporization and the mixing of the additive fluid in the exhaust gases.

According to another aspect of the invention, the turbulator may comprise a plurality of holes realized in the front end of the beaker shaped body. This aspect has the advantage of providing a very simple and reliable solution to generate the zone of turbulence in the mixing chamber.

According to another aspect of the invention, the turbulator may alternatively or additionally comprise a swirler. This solution has the advantage of imparting a swirl motion to the flow of exhaust gases entering the mixing chamber through the turbulator, thereby further im-proving the mixing of the additive fluid.

Still another aspect of the invention provides that the mixing device may comprise an in-jector to inject the additive fluid inside the external pipe. This solution has the advantage of embodying in a single device both the functions of supplying the additive fluid and mixing it with the exhaust gases.

According to an aspect of this solution, the injector may be located to inject the additive fluid directly inside the mixing chamber. For example, the injector may be located in the front end of the beaker shaped body, particularly in its center This aspect of the invention has the advantage of bringing the injection area in the immediate vicinity of the zone of turbulence and/or recirculation, allowing an effective mixing of the additive fluid and a re-duction of the overall dimensions of the mixing device.

According to still another aspect of the invention, the injector may be coupled to a conduit arranged to convey the additive fluid into the mixing chamber.

Thanks to this solution, it is advantageously possible to locate the injector in a more con-venient place, for example on the external pipe of the mixing device or even outside of the latter.

According to another aspect of the invention, the internal beaker-shaped body may com-prise a pipe defining the lateral wall thereot a closing cap coupled to a front end section of the pipe, and an annular element coupled to the opposite rear end section of the pipe to define the connection rim.

This aspect of the invention provides a simple and practical solution for manufacturing the beaker-shaped body.

Another embodiment of the invention provides an exhaust system for an internal combus- tion engine, comprising an exhaust pipe to convey exhaust gases from the internal com-bustion engine to the external environment, an aftertreatment device located in the exhaust pipe to change the composition of the exhaust gases, and the exhaust mixing device lo-cated in the exhaust pipe upstream of the aftertreatment device. This embodiment of the invention takes advantage of the mixing device explained above, particularly to enhance the mixing of the exhaust gases with an additive fluid to be adsorbed in the aftertreatment device.

According to an aspect of this embodiment, the external pipe of the exhaust mixing device may be a portion of the exhaust pipe. This aspect of the invention has the advantage of integrating the mixing device in the exhaust pipe.

According to another aspect of the invention, the external pipe of the exhaust mixing device may be a portion of an housing of the aftertreatment device. This aspect of the invention has the advantage of integrating the mixing device directly in the aftertreatment device.

Still another embodiment of the invention provides an automotive system comprising an internal combustion engine and the exhaust system described above connected to the internal combustion engine. Also this embodiment of the invention takes advantage of the mixing device to enhance the mixing of the exhaust gases with the additive fluid to be adsorbed in the aftertreatrnent device

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically shows an automotive system.

Figure 2 is the section A-A of figure 1.

Figure 3 is a longitudinal section of a mixing device included in the automotive system of figure 1.

Figure 4 is the section IV-IV of figure 3 Figure 5 is a longitudinal section of a mixing device according to a more detailed embodi-ment of the invention.

Figure 6 shows a variant of the mixing device of figure 5.

Figure 7 is a longitudinal section of a mixing device according to another more detailed embodiment of the invention.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that may belong to a motor vehicle, such as a car or a truck. The automotive system in-cludes an internal combustion engine (ICE) 110, for instance a gasoline or diesel engine, having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement ofthe piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190. Each of the cylinders has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow airinto the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some ex-amples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbo- charger 230, having a compressor 240 rotationally coupled to a turbine 250, may be pro-vided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. In the present example, the aftertreatment devices include an oxidation catalyst (e.g. a DOC) 280, a particulate filter (e.g. a DPF) 281 located downstream of the oxidation catalyst 280, and a selective reduction catalyst (SCR) 282 located downstream of the particulate filter 281. The oxidation catalyst 280 and the particulate filter 281 may be accommodated inside a common casing located in the ex- haust pipe 275. Other embodiments may additionally or alternatively include, catalytic con- verters (two and three way), lean NOx traps, hydrocarbon adsorbers and/or other after-treatment devices.

The exhaust system 270 may also include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The exhaust system 270 may further comprise at least an exhaust mixing device 600, which may be located in the exhaust pipe 275 to mix an additive fluid with the exhaust gases coming from the ICE 110.

As schematically shown in figure 3 and 4, the mixing device 600 may comprise an extemal pipe 605 and an internal beaker-shaped body 606 that is axially accommodated inside the external pipe 605, in such a way that they extend almost in the same longitudinal direction.

For example, the external pipe 605 and the beaker-shaped body 606 may be mutually coaxial. The beaker-shaped body 606 has afront end 607, which is destined to be reached first by the exhaust gas flowing in the external pipe 605, and an opposite open end 608, which is destined to be located downstream of the front end 607 with respect to the gas flow direction. The beaker-shaped body 606 has an overall diameter that is smaller than the overall diameter of the external pipe 605, so that the internal volume of the external pipe 605 is locally divided into a toroidal interspace 615 defined between the internal sur-face of the external pipe 605 and the external surface of the beaker-shaped body 606, and a mixing chamber 620 defined by the internal cavity of the beaker-shaped body 606. A connection rim 609 is located at the rear open end 608 of the beaker-shaped body 606 for fastening the latter to the external pipe 605. The connection rim 609 has also the function of closing the axial exit of the toroidal interspace 615, while letting the axial exit of the mixing chamber 620 open. Even if the external pipe 605 and the beaker-shaped body 606 of the present example are substantially cylindrical and extend in a rectilinear direction, other embodiments may provide for them to have a more complex shape and/or to extend in a curved or inclined direction.

In greater details, the lateral wall of the beaker-shaped body 606 may be defined by an internal pipe 610 of smaller diameter, which is axially or coaxially inserted inside the ex-temal pipe 605. The internal pipe 610 have two opposite end sections, particularly a front end section 625 and a rear end section 630, wherein the rear end section 630 is destined to be located downstream of the front end section 625 with respect to the gas flow direc-tion. The front end section 625 of the internal pipe 610 may be slightly tapered, in such a way that its diameter progressively increases from a leading edge 635 of the internal pipe 610 towards the rear end section 630. Correspondingly, also the annular portion of the external pipe 605 surrounding the front end section 625 may be tapered substantially in the same way.

A closing cap 640 may be coupled to the front end section 625 of the internal pipe 610 to define the front end 607 of the beaker-shaped body 606. The closing cap 640 may close the axial entrance of the mixing chamber 620, while letting the axial entrance of the toroidal interspace 615 open. In the present example, the closing cap 640 may be located inside the front end section 625, so that the leading edge 635 of the intemal pipe 610 remains free. In other embodiments, the closing cap 640 may be directly coupled to the leading edge 635. The closing cap 640 of the present example is embodied as a curved sheet plate but it could also be flat or even embodied as a more massive element. The closing cap 640 may be realized in a single body with the internal pipe 610 or may be realized in separate body that may be fixed to the front end section 625 with any suitable means, such as welding.

On the other side, an annular element 645 may be coupled to the rear end section 630 of the internal pipe 610 to define the connection rim 609. The annular element 645 of the present example is embodied as a thin flange but it could also be embodied as a more massive element. In the present example, the annular element 645 is realized in a single body with the internal pipe 610 and is fixed to the external pipe 605 by any suitable means, such as welding. In other embodiments, the annular element 645 could be realized in a single body with the external pipe 605 and fixed to the internal pipe 610, or it could be realized as a separate body that is fixed to both the internal and the external pipe.

The toroidal interspace 615 communicates with the mixing chamber 620 through a plurality of narrow holes 650 which are realized in the lateral wall of the beaker-shaped body 606, for instance in the lateral wall of the intemal pipe 610, distributed between the closing cap 640 and the annular element 645. The axes of these lateral holes 650 may be radially oriented towards the central longitudinal axis of the mixing chamber 620 or maybe slightly inclined. The lateral holes 650 may be distributed on the beaker-shaped body 606 in many different ways, either ordinate or substantially casual. Preferably, the lateral holes 650 should be distributed so as to be located at different distance from the front end 607 of the beaker-shaped body 606. By way of example, the lateral holes 650 may be distributed in groups, wherein the holes of each group are circumferentially located around the internal pipe 610 and wherein these groups are located at different distances form the front end 607.

The mixing chamber 620 may be also in communication with the internal volume of the extemal pipe 605 through a turbulator 655, which is provided in the front end 607 of the beaker-shaped body 606, for instance in the closing cap 640. A turbulator may be any device that allows the passage of the gases through it, while increasing the turbulence of said gases.

In greater details, the turbulator 655 may comprise a swirler 660 located in the center of the front end 607. The swirler 660 is a component that basically comprises a plurality of vanes radially distributed around a central hub or axis. The vanes are angularly spaced to each other, in order to define passages for the gases, and are shaped so as to impart to them a swirl motion. The vanes may be straight vanes or twisted vanes. The swirler 660 may be stationary or may be rotated by the oncoming gases like a sort of turbine wheel.

The turbulator 655 may additionally or alternatively comprise a plurality of narrow holes 665, which may be realized in the front end 607 of the beaker-shaped body 606, so as to define a sort of perforated plate 670. The axes of these holes 665 may be substantially parallel to the central axis of the mixing chamber 620.

In the present example, the turbulator 655 comprises both the swirler 660, which is located in the center of the closing cap 640 and a plurality of narrow holes 665, which are realized in the annular portion of the closing cap 640 that surrounds the swirler 660 and that defines the perforated plate 670. In other embodiments, the turbulator 655 may only comprise the swirler 660 or the perforated plate 670. In the latter case, the perforated plate 670 may extend also in the central part of the closing cap 640. In still other embodiments, the tur-bulator 655 could be completely absent.

The mixing device 600 may further comprise an injector 675 destined to supply the additive fluid to be mixed with the exhaust gases. In the present example, the injector 675 is located so as to inject the additive fluid directly into the mixing chamber 620. Particularly, the in- jector 675 may be fastened to the front end 607 of the beaker-shaped body 606, for ex- ample in the central portion thereof or in the hub of the swirler 660 (if any). In other em- bodiments, the injector 675 could be located to inject the additive fluid in the internal vol-ume of the external pipe 605, upstream of the beaker-shaped body 606, outside of the mixing chamber 620. In still other embodiments, the injector 675 may be located in the external pipe 605, upstream of the beaker-shaped body 606, and a conduit may be pro-vided to convey the additive fluid from the injector to the mixing chamber. For instance, this conduit may connected the injector to a passage realized in the central portion of the front end 607 or closing cap 640. In all of these cases, the additive fluid may be provided to the injector 675 from a conduit 680 in fluid communication with a pump 685 that takes the additive fluid from a tank 690.

The mixing device 600 described above is generally located in the exhaust pipe 275, so that the front end 607 of the beaker-shaped body 606 is located upstream of the rear open end 608 with respect to the direction of the gas flow. In this way, the oncoming exhaust gases run into the front end 607 and are at least partly deviated into the interspace 615 surrounding the beaker-shaped body 606. Since the axial exit of the interspace 615 is closed by the connection rim 609, this primary flow of exhaust gas is forced to enter the mixing chamber 620 through the lateral holes 650. In this way, the primary gas flow devi-ates from the axial direction of the external pipe 605 and enters the beaker-shaped body 606 with a velocity having a radial component, thereby generating in the mixing chamber 620 a zone of recirculation, which enhances the mixing of the exhaust gases with the ad-ditive fluid supplied by the injector 675 particularly in terms of vaporization and uniform distribution.

At the same time, a secondary part of the exhaust gases may enter the mixing chamber 620 directly through the passages defined by the turbulator 655 (if present). Passing through the turbulator 655, this secondary flow of exhaust gases generates a zone of tur-bulence in the mixing chamber 620 just behind the front end 607 of the beaker-shaped body 606, upstream of the zone of turbulence mentioned above and in the immediate vi-cinity of the injector 675, thereby further enhancing the vaporization and the mixing of the additive fluid in the exhaust gases.

Referring to the scheme of figure 1, the mixing device 600 may be generally located in the exhaust pipe 275 upstream of a catalyst, so that the additive fluid mixed to the exhaust gas can be used in said catalyst to perform a particular task.

In this particular example, the DOC 280 is located in a closed coupled position (i.e. located near the ICE 110 immediately afterthe turbocharger 230), possibly followed by a DPF 281.

As shown also in figure 7, the mixing device 600 may be located in the exhaust pipe 275 between the DCC 280 (or the DPF 281 if present) and the selective reduction catalyst 282, where the injector 675 (located immediately downstream of the DOC 280) may be used to supply a Diesel Exhaust Fluid (DEF), typically a solution of Urea, which mixes with the exhaust gas to be absorbed inside the SCR catalyst 282, where the nitrogen oxides (NO) contained in the exhaust gas are converted into diatomic nitrogen and water.

In other embodiments, the exhaust system 270 may comprise a close coupled DOC 280 and a plurality of additional aftertreatment devices located in the exhaust pipe 275 in an under floor configuration. These under floor aftertreatment devices may include an SCR catalyst 282 preceded by a first mixer 600, which may be associated to a first injector 675 used to supply the Diesel Exhaust Fluid (DEF) to be absorbed in the 8CR catalyst 282.

Downstream of the 8CR catalyst 282, the under floor aftertreatment devices may also include a second DOC 280 coupled with a DPF. Between the 8CR catalyst 282 and the second DOC 280, a second mixing device 600 may be located in the exhaust pipe 275 and may be associated to a second injector 675, which may be used to supply unburned fuel (I-IC) into the exhaust gas stream during the regeneration of the particulate filter 281.

In any case, the external pipe 605 of the mixing device 600 may have substantially the same diameter of the exhaust pipe 275, for example it may be embodied by a portion of the exhaust pipe 275. In other embodiments, the external pipe 605 of the mixing device 600 may have substantially the same diameter of the casing containing the catalyst (for example the casing containing the oxidation catalyst or the selective reduction catalyst), for example it may embodied by a portion of said casing.

Figure 5 shows a mixing device 600A according to a more detailed and concrete embodi-ment of the present invention. The reference numbers indicated in figure 5 are the same that have been used in figure 3 and 4, since they basically corresponds to the same tech-nical features.

The mixing device 600A comprises an external pipe 605, which may be basically a portion of the exhaust pipe 275. The external pipe 605 accommodates an internal beaker-shaped body 606, so that the internal volume of the external pipe 605 is divided into a toroidal interspace 615, which is defined between the intemal surface of the external pipe 605 and the external surface of the beaker-shaped body 606, and a mixing chamber 620, which defined by the internal cavity of the beaker-shaped body 606. The beaker-shaped body 606 has a front end 607 and an opposite rear open end 606 that is provided with a con-nection rim 609.

The beaker-shaped body 606 particularly comprises an internal pipe 610 having two op-posite end sections, including a front end section 625, which is destined to be reached first by the exhaust gas flawing in the external pipe 605, and a rear end section 630, which is destined to be located downstream of the front end section 625 with respect to the gas flow direction. In this example, the rear end section 630 is tapered in such a way that its diameter progressively decreases away from the front end section 625. Correspondingly, also the annular portion of the external pipe 605 surroundin9 the rear end section 630 is tapered substantially in the same way.

The front end 607 of the beaker-shaped body 606 is defined by a closing cap 640, which is directly coupled to the front end section 625 of the internal pipe 610 to close the axial entrance of the mixing chamber 620, while letting the axial entrance of the toroidal inter-space 615 open. The closing cap 640 may be realized in a single body with the internal pipe 610 or may be realized in separate body that may be fixed to the front end section 625 with any suitable means, such as welding.

On the other side, the connection rim 606 is defined by an annular element 645, which is coupled to the rear end section 630 of the internal pipe 610 and to the external pipe 605, in order to close the axial exit of the toroidal interspace 615, while letting the axial exit of the mixing chamber 620 open. In the present example, the annular element 645 is realized in a single body with the internal pipe 610 and is fixed to the external pipe 605 by suitable means, such as welding or the like.

The toroidal interspace 615 communicates with the mixing chamber 620 through a plurality of narrow holes 650 which are realized in the lateral wall of the internal pipe 610, distributed between the closing cap 640 and the annular element 645. The axes of these lateral holes 650 may be radially oriented towards the central longitudinal axis of the mixing chamber 620 or may be slightly inclined. The lateral holes 650 are distributed in groups, wherein the holes of each group are circumferentially located around the internal pipe 610 and wherein these groups are located at different distances form the closing cap 640. In this or other examples, the lateral holes 650 may have different diameters. For example, the diameter of the holes may decrease from the closing cup towards the annular element 645.

The mixing chamber 620 is also in communication with the internal volume of the external pipe 605 through a turbulator 655, which is provided in the closing cap 640. In the present example, the turbulator 655 comprises a swirler 660 located in the center of the closing cap 640 and a plurality of narrow holes 665, which may be realized in the annular portion of the closing cap 640 that surrounds the swirler 660. In this way, that portion of the closing cap 640 defines a sort of perforated plate 670. In other embodiments, the swirler 660 may be absent.

In the example of figure 5, the additive fluid may be supplied by an injector (not depicted), which is located in the external pipe 605 upstream of the closing cap 640, to inject the additive fluid outside of the mixing chamber 620.

In the example of figure 6, which is basically a variant of the embodiment of figure 5, a conduit 695 is provided for conveying the additive fluid from an injector 675 to the mixing chamber 620. In particular, the conduit 695 extends from the wall of the external pipe 605 inwards, and it is connected with the mixing chamber 620 through a passage realized in the closing cap 640, for example in the central portion thereof. In the present example, the above mentioned passage is defined by the swirler 660, but it could be also defined by an opening that matches with the internal end of the conduit 695, for example similar to the conduit 680 of figure 3 and 4. The opposite end of the conduit 695 may open out from the external pipe 605 and may be coupled to the injector 675 of the additive fluid.

Another concrete embodiment of the present invention is shown in figure 7, where the reference numbers are the same that have been used in figure 3, 4, 5 and 6, since they basically corresponds to the same technical features. Figure 7 particularly shows a mixing device 600B which is located in the exhaust pipe 275, between the DOG 280 and a selec-tive reduction catalyst 282, to mix the exhaust gases with the urea solution (or the like) necessary for the reduction of the NO. In the present example, the DOC 280 and the selective reduction catalyst 282 are "closed coupled", connected by a short portion of the exhaust pipe 275 having an elbow. However it should be understood that, in other embod-iments, the DOC 280 and the selective reduction catalyst 282 may be more distant one another.

The mixing device 600B comprises an external pipe 605, which may be basically a portion of the casing of the selective reduction catalyst 282. The external pipe 605 accommodates an internal beaker-shaped body 606, so that the internal volume of the external pipe 605 is divided into a toroidal interspace 615, which is defined between the internal surface of the external pipe 605 and the external surface of the beaker-shaped body 606, and a mix-ing chamber 620, which defined by the internal cavity of the beaker-shaped body 606. The beaker-shaped body 606 has a front end 607 and an opposite rear open end 608 that is provided with a connection rim 609.

The lateral wall of the beaker-shaped body 606 is defined by an internal pipe 610, which however is not cylindrical as per the preceding example, but it has a tapered shape. Cor-respondingly, also the external pipe 605 is tapered substantially in the same way. The internal pipe 610 have two opposite end sections, particularly a front end section 625, which is destined to be reached first by the exhaust gas flowing in the external pipe 605, and a rear end section 630, which is destined to be located downstream of the front end section 625 with respect to the gas flow direction.

The front end 607 of the beaker-shaped body 606 is defined by a closing cap 640, which is directly coupled to the front end section 625 of the internal pipe 610 to close the axial enhance of the mixing chamber 620, while. letting the axial entrance of the toroidal inter-space 615 open. The closing cap 640 may be realized in a single body with the internal pipe 610 or may be realized in separate body that may be fixed to the front end section 625 with any suitable means, such as welding.

On the other side, the connection rim 609 is defined by an annular element 645, which is coupled to the rear end section 630 of the internal pipe 610 and to the external pipe 605, in order to close the axial exit of the toroidal interspace 615, while letting the axial exit of the mixing chamber 620 open. In the present example, the annular element 645 is realized in a single body with the internal pipe 610 and is fixed to the external pipe 605 by suitable means, such as welding or the like.

The toroidal interspace 615 communicates with the mixing chamber 620 through a plurality of narrow holes 650 which are realized in the lateral wall of the internal pipe 6101 distributed between the closing cap 640 and the annular element 645. Due to the tapered form of the internal pipe 610, the axes of these lateral holes 650 are slightly inclined with respect to the central longitudinal axis of the mixing chamber 620. The lateral holes 650 are distrib-uted in groups, wherein the holes of each group are circumferentially located around the internal pipe 610 and wherein these groups are located at different distances form the closing cap 640. In this or other examples, the lateral holes 650 may have different diam-eters.

The mixing chamber 620 is also in communication with the internal volume of the external pipe 605 through a turbulator 655, which is provided in the closing cap 640. In the present example, the turbutator 655 comprises a swirler 660 located in the center of the closing cap 640 and a plurality of narrow holes 665, which may be realized in the annular portion of the closing cap 640 that surrounds the swirler 660. In this way, that portion of the closing cap 640 defines a sort of perforated plate 670. As an alternative, the swirler 660 may be absent to reduce back pressures.

The additive fluid may be supplied by an injector 675, which may be located in the exhaust pipe 275 upstream of the closing cap 640 to inject the additive fluid outside of the mixing chamber 620. In particular, the injector is located in the elbow of the exhaust pipe, so that it is axially aligned with the internal pipe 610 of the mixing device, in order to improve the mixing effects.

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 em- bodiment, it being understood that various changes may be made in the function and ar-rangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCES

automotive system internal combustion engine 120 engine block cylinder cylinder head camshaft piston 145 crankshaft combustion chamber cam phaser fuel injector fuel rail 180 fuelpump fuelsource intake manifold 205 air intake duct 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 oxidation catalyst 281 particulate filter 262 selective reduction catalyst 290 VGT actuator 300 exhaust gas recirculation system 310 EGR cooler 320 EGR valve 330 throttle body 600 mixing device 600A mixing device 600B mixing device 605 external pipe 606 beaker-shaped body 607 front end 608 rearopen end 609 connection rim 610 internal pipe 615 toroidal interspace 620 mixing chamber 625 front end section 630 rear end section 635 leading edge 640 closing cap 645 annular element 650 lateral holes 655 turbulator 660 swirler 665 narrow holes 670 perforated plate 675 injector 680 conduit 665 pump 690 tank 695 conduit 700 boss

Claims

CLAIMS1. An exhaust mixing device (600) for an internal combustion engine (110), comprising an external pipe (605), an internal beaker-shaped body (606) axially accommodated inside the external pipe (605), an interspace (615) defined between the external pipe (605) and a lateral wall of the beaker-shaped body (606), a mixing chamber (620) defined inside the beaker-shaped body (606) between a front end (607) and a rear open end (608) thereof, a connection rim (609) located at the rear open end (608) of the beaker-shaped body (606) to close the interspace (615), and a plurality of holes (650) realized in the lateral wall of the beaker-shaped body (606) to connect the mixing chamber (620) with the interspace (615).
2. An exhaust mixing device (600) according to claim 1, wherein the axes of said holes (650) are inclined with respect to a central longitudinal axis of the mixing chamber (620).
3. An exhaust mixing device (600) according to claim I or 2, wherein the mixing cham-ber (620) is additionally connected with the internal volume of the external pipe (605) through a turbulator (655) provided in the front end (607) of the beaker-shaped body (606).
4. An exhaust mixing device (600) according to claim 3, wherein the turbulator (655) comprises a plurality of holes (665) realized in the front end (607) of the beaker-shaped body (606).
5. An exhaust mixing device according to claim 3 or 4, wherein the turbulator (655) comprises a swirler (660).
6. An exhaust mixing device (600) according to any of the preceding claims, comprising an injector (675) to inject an additive fluid inside the external pipe (605).
7. An exhaust mixing device (600) according to claim 6, wherein the injector (675) is located to inject the additive fluid inside the mixing chamber (620).
8. An exhaust mixing device (600) according to claim 7, wherein the injector (675) is located in the front end (6079 of the beaker-shaped body (606).
9. An exhaust mixing device (600) according to claim 6. wherein the injector (675) is coupled to a conduit (695) arranged to convey the additive fluid into the mixing chamber (620).
10. An exhaust mixing device (600) according to any of the preceding claims, wherein the internal beaker-shaped body (606) comprises a pipe (610) defining the lateral wall thereof, a closing cap (640) coupled to a front end section (625) of the pipe (610), and an annular element (645) coupled to the opposite rear end section (630) of the pipe (610) to define the connection rim (609).
11. An exhaust system (270) for an internal combustion engine (110), comprising an exhaust pipe (275) to convey exhaust gases from the internal combustion engine to the external environment, an aftertreatment device (280, 281, 282) located in the exhaust pipe (275) to change the composition of the exhaust gases, and an exhaust mixing device (600) according to any of the preceding claims located in the exhaust pipe (275) upstream of the aftertreatment device (280, 281, 282).
12. An exhaust system (270) according to claim 11, wherein the external pipe (605) of the exhaust mixing device (600) is a portion of the exhaust pipe (275).
13. An exhaust system (270) according to claim 11, wherein the external pipe (605) of the exhaust mixing device (600) is a portion of an housing of the aftertreatment device (280, 281, 282).
14. An automotive system (100) comprising an internal combustion engine (110) and an exhaust system (270) according to any of the claims from 11 to 13.