GB2533353A

GB2533353A - Mixer for an exhaust after-treatment system of an internal combustion engine

Info

Publication number: GB2533353A
Application number: GB1422518.9A
Authority: GB
Inventors: Sculto Aurelio
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2014-12-17
Filing date: 2014-12-17
Publication date: 2016-06-22

Abstract

A mixer 1 for an exhaust gas aftertreatment system of an internal combustion engine. The mixer comprises a body portion 2 provided with a plurality of movable blades 3, and a blade positioning device 5 to move one or more blades with respect to the body portion. The blades may be moveable between deployed and folded positions. The blade positioning device may comprise an actuator 6 and an actuation arm 6a coupled to the blades. A connecting element 7 may connect two or more blades such that they are moved concurrently. The body portion may comprise a circular outer frame with a central axis Y, which the blades may extend radially with respect to. The body portion may instead comprise a quadrangular outer frame. The mixer may be in an exhaust system with an upstream injector (e.g. urea) and a downstream aftertreatment device (e.g. a selective catalytic reduction, SCR, device). A method of operating the system is also disclosed.

Description

MIXER FOR AN EXHAUST GAS AFTERTREATMENT SYSTEM OF AN

INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The technical field relates to a mixer for an exhaust gas aftertreatment system of an internal combustion engine for mixing one or more reactants, which are injected into the exhaust gas aftertreatment system, with the exhaust gas, to reduce emissions.

BACKGROUND

Exhaust gas aftertreatment systems for the emissions reduction of an internal combustion engine, and in particular for particulates and oxides of nitrogen (NOx) reduction, are known. These systems are provided with aftertreatment devices installed in the exhaust pipe of the internal combustion engine and comprise for example a diesel particulate filter (DPF) and/or a selective catalytic reduction (SCR) system for NOx control.

It is known in the art, to inject a reactant (catalyst) fluid in the exhaust pipe of the internal combustion engine in order to reduce emissions by means of the aforementioned aftertreatment devices. In particular, hydrocarbon based reactants, generally indicated as HC, like the same fuel supplied to the internal combustion engine, are injected in the exhaust pipe in order to promote the regeneration of diesel particulate filter (DPF) with the burning of soot accumulated therein. Furthermore, a fluid catalyst such as urea, or ammonia, or a combination thereof (generally in a water solution) can be injected into the exhaust pipe of an internal combustion engine in order to promote the reduction of nitrogen oxides (NOx) in the selective catalytic reduction device (SCR).

Hydrocarbon (HC) and the urea catalyst are injected into the exhaust gas flow by means of injectors provided in the exhaust pipe, upstream of the diesel particulate filter (DPF) and of the selective catalytic reduction system (SCR).

To provide an efficient reactant utilization mixers are arranged downstream of the reactant injector to enhance vaporization and dispersion of the reactant in the exhaust gas flow. In particular, mixers are used to enhance urea vaporization to allow NOx reduction by the SCR system and/or to enhance vaporization and dispersion of hydrocarbon (HC), to promote DPF device regeneration. Even the mixer allows to enhance a vaporization of the reactant in the exhaust gas flow, the mixer also create backpressure due to the partial obstruction of the exhaust gas flow passage.

Additionally, the mixer performances are strictly related to the flow rate and negatively affects exhaust gas flow, and thus the engine performance, especially when the reactant is not injected and the presence of a mixer is not needed.

In fact, the mixer is not always needed during the internal combustion engine operations. In fact, the regeneration of a DPF occurs every 800 -1600 Km and takes around 10 -20 minutes, depending on the engine operating conditions. Additionally, the urea injection is inhibited when the exhaust gas temperature drops below 200°C, such as for example at the engine starts and often during the urban traffic drive, and when a predetermined maximum mass of urea is reached in the SCR system.

It is an object of an embodiment of the present invention to provide a mixer for an exhaust gas aftertreatment system, and also an exhaust gas aftertreatment system comprising said mixer, that provides the desired mixing functions and also reduces backpressure problems, in particular when mixing function is not needed.

Another object of an embodiment of the present invention is to provide a mixer for an exhaust gas aftertreatment system able to improve efficiency of the aftertreatment system in a wide range of the exhaust gas flow rate.

SUMMARY

An embodiment of the disclosure provides a mixer for an exhaust gas aftertreatment system of an internal combustion engine, comprising a body portion provided with a plurality of movable blades and at least one blade positioning device to move one or more blades, which may have the shape of a flat plate, with respect to the body portion. The blades are arranged to be movable with respect to the body portion of the mixer, i.e. with at least a portion of the blade movable with respect to the body portion of the mixer.

Movable can mean that the blades are swivable or rotatable, e.g. that a first part of the blades are fixed to the body portion whereas a second part, possibly shaped as a flat plate, can rotate around a rotation axis. In this case the rotation may be in a plane perpendicular to the flow direction, such that the gas flow can push the blade into an open or folded position in which it provides a reduced flow resistance.

According to a possible embodiment the blades can be movably constrained to the body portion, i.e. constrained or coupled to the body portion to be movable with respect to it.

It has to be noted that the blades of the mixer define a resistant section for the flow passing through the mixer, i.e. an obstructed section of the mixer, which can be modified by changing the position of the blades with respect to the body portion. The movement of the blades is driven by the blade positioning device, allowing a correspondent, controlled, modification of the resistant section of the mixer.

It has to be noted that the expression resistant section is used in the present disclosure to indicate the area (section) of the mixer that is obstructed by the blades, thus reducing the area (section) of the mixer through which the flow passes. Advantageously, the presence of a blade positioning device, able to move the blades with respect to the body portion of the mixer to modify the position of the blades, allows to provide a variable resistance to the flow passing through the mixer.

Advantageously, the resistant section of the mixer, defined depending on the blades position, can be modified and thus regulated by modifying the position of the blades. Thus, it is possible to increase the mixing performances in a wide range of flow rates and also allows to reduce the backpressure, in particular when mixing is not needed.

In fact, the modification of the resistant section of the mixer provides a corresponded modification of the flow passage section of the mixer, and in particular a modification of the flow passage section of the exhaust pipe inside which the mixer can be installed. Additionally, the use of a blade positioning device allows to cause the movement of one or more blades of a predetermined extent, thus providing a desired modification of the resistance to the flow passing thorough the mixer.

According to an embodiment, one or more blades are movable with respect to the body portion between a deployed or closed position, providing a maximum resistance to the flow passing through the mixer (and thus a maximum resistant section), and a folded position providing a minimum resistance to the flow passing through the mixer (and thus a minimum resistant section). The movement of the blades between these positions allows to better adapt the resistance provided by the mixer to the flow passing therethrough, and thus to obtain a mixing optimization for different rates of the flow passing through the mixer. It has to be noted that the blade positioning device allows to move one or more blades to arrange it in a desired position. One or more blades can be arranged in different positions selected between said folded position and said deployed position, by means of the blade positioning device.

According to a possible embodiment the folded position of the blades, providing the minimum resistance to the flow passing through the mixer, is used when the mixing is not required, to reduce the backpressure. According to an advantageous aspect, the folded position of the blades can be a feathered position, in which the blade is parallel to the flow direction inside the mixer. In this position the resistant section and the backpressure can be minimized.

According to an embodiment, the blade positioning device comprises at least one actuator, e.g. a pneumatic or electric actuator. The presence of an actuator advantageously allows to obtain an accurate movement of the blades which can be positioned in the desired position, thus providing the desired resistance to the flow passing thorough the mixer.

Advantageously, the use of pneumatic or electric actuators allows to provide an easy and simple control of the movement of the blade and also a simple integration into an exhaust gas aftertreatment system for an internal combustion engine.

According to still another embodiment, the blade positioning device comprises at least one connecting element to connect two or more blades to each other, which are moved concurrently, i.e. simultaneously. An advantage of this embodiment is to provide a simple control of the blades and also to provide a desired and certain modification of the resistance to the flow by providing an equal modification of the position of two or more blades of the mixer, simultaneously.

According to an embodiment, the actuator comprises an actuation arm coupled to one or more blades, to move the latter. According to a possible embodiment the actuator, and in particular its actuation arm, is coupled to the connecting element connecting two or more blades. Advantageously, the actuator can be directly, or indirectly, coupled to one or more blades thus causing their movements. The actuation arm can be arranged so as to pass through an exhaust pipe in which the mixer is installed, thus allowing the arrangement of the actuator body, or actuator cylinder, outside said exhaust pipe. According to an embodiment, the blade comprises a rotation axis and is movable with respect to the body portion to rotate about the rotation axis. An advantage of this embodiment is a better control of the blades movements by providing an angular displacement of the blades about the rotation axis, and at the same an effective constraint of the blades to the body portion can be obtained, while allowing a movement between these components.

According to still another embodiment, the body portion comprises a circular-shaped outer frame, having a central axis, or a quadrangular-shaped outer frame. These embodiments allow to install the mixer in a pipe having standard circular or quadrangular cross-sections, without the need of modifying the pipe in which the mixer has to be installed.

According to still another embodiment, the blades of the mixer radially extend with respect to the central axis of the circular-shaped outer frame. An advantage of this embodiment is to provide an efficient arrangement of the blades in order to form a resistant section which can be easily modified, in a controlled manner, by means of the movement of the blades.

Another aspect of the invention provides an exhaust gas aftertreatment system for an internal combustion engine, comprising an exhaust pipe and at least one exhaust gas aftertreatment device receiving the exhaust gas flow from the internal combustion engine, further comprising at least one mixer according to the various aspects of the invention. The mixer may comprise a body portion provided with a plurality of movable blades and at least one blade positioning device to move the blades with respect to the body portion. The mixer is arranged in the exhaust pipe upstream of exhaust gas aftertreatment device, and at least one injector is arranged in the exhaust pipe, upstream of the mixer, for injecting at least one reactant in the exhaust gas flow.

The movable blades of the mixer advantageously forms a variable resistant section of the mixer. Therefore the movement of the blades, and in particular their position change caused by the blade positing device allows to modify the resistance to the flow passing thorough the mixer, and thus a modification of the resistant section of the mixer. The modification of the resistant section of the mixer corresponds to a modification of the flow passage section inside the exhaust pipe. In fact, the exhaust pipe, inside which the mixer is installed, is provided with a passage section for the exhaust gas flow that is modified by the movement of the mixer's blades, i.e. due to a change of the position of the blades operated by the blade positioning device.

Advantageously, the presence of a mixer, wherein the resistant section defined by the position of the blades can be modified, allows to better adapt the mixer to different flow rates of the exhaust gas. In particular, when mixing is not needed and the reactant injector is deactivated, the blades can be advantageously arranged to reduce the resistance to the exhaust flow, thus reducing the backpressure.

This allows to increase the engine performance and to reduce fuel consumption and CO2 emission.

Still another aspect of the invention provides a method of operating an exhaust gas aftertreatment system for an internal combustion engine according to the various aspects of the invention. The method comprises the step of operating said internal combustion engine to produce an exhaust gas flow in the exhaust pipe; the step of controlling at least one injector arranged in the exhaust pipe upstream of the mixer for injecting a reactant in the exhaust gas flow; and the step of operating at least one blade positioning device of the mixer to move one or more blades with respect to the body portion, which may depend on the flow rate of the exhaust gas in the exhaust pipe produced by the internal combustion engine.

Advantageously, the method of operating the exhaust gas aftertreatment system allows to modify the position of the blades, and thus the resistance to the exhaust flow in the exhaust pipe, providing also a variation of the resistant section of the mixer defined by the blade position.

The modification of the resistance to the exhaust gas flow (modification of the resistant section) allows to obtain an effective mixing of the reactant and the exhaust gas flow in a wide range of flow rates, also reducing the backpressure in the exhaust pipe.

Advantageously, when the mixing of the reactant with the exhaust gas flow is not needed, the blades can be moved in a folded position, thus providing the minimum resistance (minimum resistant section) to the exhaust flow inside the exhaust pipe. In fact, according to an embodiment, when the injector is deactivated, the at least one blade positioning device of the mixer is operated to move the blades in a folded position, providing a minimum resistance (minimum resistant section) to the exhaust flow passing through the mixer.

The method according to one of its aspects can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier associated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

Still another aspect of the invention provides an apparatus for operating an exhaust gas aftertreatment system for an internal combustion engine according to the various aspects of the invention, the apparatus comprising means for operating the internal combustion engine to produce an exhaust gas flow in the exhaust pipe; means for controlling at least one injector arranged in said exhaust pipe for injecting at least one reactant in the exhaust gas flow; means for operating at least one blade positioning device of the mixer to move one or more blades with respect to the body portion, which may depend on the flow rate of exhaust gas in the exhaust pipe produced by the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which: * Figures 1, 2 and 3 show to three possible embodiments of a mixer; * Figure 4 is a schematic view of a possible embodiment of an exhaust gas aftertreatment system of an internal combustion engine; * Figure 5 is a schematic view of another possible embodiment of an exhaust gas aftertreatment system of an internal combustion engine.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

With reference to figures 1, 2, and 3, a mixer 1 for an exhaust gas aftertreatment system 10 of an internal combustion engine 100 is used to mix the exhaust gas produced by an internal combustion engine 100 with at least one reactant. The internal combustion engine 100 can be fuelled by, but is not limited to, gasoline, diesel biodiesel, and other hydrocarbon fuels. The exhaust gas flow produced by the internal combustion engine 100 is directed into an exhaust gas aftertreatment system 10 comprising an exhaust pipe 11 having one or more exhaust gas aftertreatment devices 12. The exhaust gas aftertreatment devices 12 may be any device configured to change the composition of the exhaust gas. Some examples of aftertreatment devices 12 include, but are not limited to, selective catalytic reduction (SCR) systems, and particulate filters, for example diesel particulate filters (DPF). Other embodiments, not shown in attached figures, may include an exhaust gas recirculation system.

According to a possible embodiment, as for example shown respectively in figures 4 and 5, the exhaust gas aftertreatment system 10 may include a selective catalytic reduction system (SCR) or a particulate filter, such as for example a diesel particulate filter (DPF). The particulate filter, for example a diesel particulate filter may be combined with catalytic converters, or oxidation catalysts (DOC-DPF). Even if not shown in the attached figures, according to a possible configuration, the exhaust gas aftertreatment system 10 may include other aftertreatment devices or a combination of two or more aftertreatment devices.

According to a possible embodiment along the same exhaust pipe 11 a selective catalytic reduction system (SCR) and a diesel particulate filter (DPF) may be provided.

An injector 20 of the exhaust gas aftertreatment system is installed on the exhaust pipe 11, upstream of the aftertreatment device 12. In the embodiment shown in figure 4 an injector 20 of urea reactant, or ammonia, or a combination thereof (typically in water solution), and also other known catalysts used in selective catalytic reduction system (SCR) for NOx control, is arranged upstream of the selective catalytic reduction system (SCR) 12.

In the embodiment shown in figure 5, an injector 20 is installed in the exhaust pipe 11 for injecting in the exhaust gas flow hydrocarbon (HC) upstream of the diesel particulate filter (DPF).

The reactant, such as for example hydrocarbon or urea, are supplied by suitable means such as a pump 16, connected to a reactant reservoir 16a.

According to an aspect of an embodiment of the present invention the hydrocarbon (HC) used to promote the regeneration of the diesel particulate filter (DPF) is fuel used to operate the engine 100 provided from a fuel supply line 101 of the internal combustion engine 100, see for example figure 5.

The mixer 1 is configured to allow the disposition within the exhaust pipe 11 of the exhaust gas aftertreatment system 10. The mixer 1 can be attached inside the exhaust pipe 11 in any suitable manner, such as for example by welds or detachable attachments including fasteners, clips, etc. The mixer can be arranged upstream of the aftertreatment device 12 and downstream of a reactant injectors 20, to promote mixing between the injected reactant and the exhaust gas flow.

Returning now to figures 1, 2 and 3, the mixer 1 for an exhaust gas aftertreatment system 10 of an internal combustion engine 100, comprises a body portion 2 provided with a plurality of blades 3 movable with respect to the body portion 2 so as to alter the exhaust flow passing through the mixer 1. In particular, the movable blades 3 allow to provide a low backpressure when the injection of reactant is not needed and also allow to enhance mixing at wide range of exhaust flow rate.

More in detail, blades 3 of the mixer 1 forms a resistant section A which can be advantageously modified by the movement of the blades 3 with respect to the body portion 2. In other words, the mixer 1 is provided with a variable resistant section A, depending on the position of the one or more blades 3 with respect to the body portion 2.

It has to be noted that the blades are provided on the body portion to be movable with respect to it, i.e. with at least a portion of the blade movable with respect to the body portion of the mixer. According to a possible embodiment, the blades 3 are movably constrained to the body portion 2.

According to an aspect of the invention the body portion 2 and the blades 3 are made of metal, or any other suitable material able to resist to the temperature of the exhaust gas flow.

A blade 3 comprises a substantially flat planar surface, as for example in the embodiments shown in figures 1 and 2, or it can have a curved surface, as for example in the embodiment shown in figure 3.

The curvature of the blades 3 can be different, providing different aerodynamic profile according to possible embodiments not shown in the figures.

Also the shape of the blades 3 can vary according to different possible embodiments, and it can be quadrangular, as for example shown in the embodiments of figures 1, 2 and 3. More in detail, in the embodiment shown in figure 1 and 3, the blades are substantially rectangular-shaped, and in the embodiment of figure 2 the blades 3 has a substantially trapezoidal shape.

The blades 3 are movable with respect to the body portion 2 of the mixer 1, and in particular the blades can be movably constrained to the body portion 2, between a deployed position, providing a maximum resistance to the flow passing through the mixer (maximum resistant section), and a folded position providing a minimum resistance to the flow passing through the mixer (minimum resistant section).

In other words, according to a possible embodiment, the resistance and thus the resistant section A formed by the blades 3 can be varied by the movement of the blades.

In particular, in the deployed position, the blades are positioned to provide the maximum resistant section A and thus the maximum resistance to the exhaust flow. In this position the backpressure provided by the mixer in the exhaust pipe is high.

On the contrary, in the folded position, the blades provide the minimum resistant section A, and thus the minimum resistance to the exhaust gas flow. The folded position may correspond to a feathered position of the blades, in which the blades are directed parallel to the exhaust gas flow, and in particular to the exhaust gas flow direction F, to reduce backpressure.

Due to the variable resistant section A of the mixer 1, defined by the position of the blades 3 with respect to the body portion 2, the flow passage section of the exhaust pipe 11, substantially corresponding to the cross-section of the exhaust pipe 11, can be advantageously modified.

The mixer 1 comprises at least one blade positioning device 5, schematically shown in the figures, to move one or more blades 3 with respect to the body portion 2, to modify the position of the blades.

The number of the blades 3 of the mixer 1 can be varied according to the mixing performance to be obtained and also depending on the desired resistance to the flow, and in particular depending on the extent of the resistant section to be formed.

The blade positioning device 5 comprises at least one actuator 6 intended to move one or more blades 3. The actuator 6 can be of the pneumatic type, or of the electric type, or of other types known in the art.

The actuator 6 comprises an actuation arm 6a, schematically shown in figures 4 and 5, coupled to one or more blades 3 to move them with respect to the body portion 2, to alter the flow passing through the mixer and thus to modify the resistance to the flow passing through the mixer 1. The actuation arm 6a is movable with respect to an actuator body, or actuator cylinder, schematically shown in the figures.

Two or more movable blades can be connected to each other by means of at least one connecting element 7 of the blade positioning device 5. The connecting element 7, for example shaped as a connecting arm, as for example shown in the embodiments of figures 1, 2 and 3, allow the concurrent (simultaneous) movement of two or more blades 3. The connecting element is for example schematically shown in figures 1, 2 and 3, using a dotted line.

It has to be noted that, for clarity reasons, only a connecting element 7 between two blades 3 is shown in figures 1 and 3. However, it has to be noted that according to a possible embodiment three or more blades, in some embodiments all the blades of the mixer, can be connected to each other by one or more connecting element 7.

The actuator 6, and in particular the actuation arm 6a can be directly, or indirectly, coupled to the one or more blades 3. According to a possible embodiment, the actuator 6, and in particular the actuation arm 6a is coupled to two or more blades 3, which are connected to each other by means of at least connecting element 7. In other words, the connecting element 7 provides suitable transmission means, or kinematics linkage, to transmit the movement from the actuator 6 to two or more blades connected one to another. It has to be understood that the connection between the connecting element 7, the blades 3 and the actuator 6 are schematically shown in figures 1, 2 and 3, to schematically shown that the connecting element 7 allows a simultaneous movement of the connected blades 3, and in particular a rotation about their rotation axis X, by means of the actuator 6.

The blade positioning device 5, and in particular the actuator 6 of the mixer 1, is operated to move the blades 3 with respect to the body portion 2 in one or more positions between the deployed position and the folded position. In other words, the blades can be moved to modify the resistant section A in different and predetermined positions, to enhance the mixing effect taking into account the increase of resistance to the flow.

The blades 3 comprise a rotation axis X and are movable with respect to the body portion 2 to rotate about the rotation axis X. The blades 3 are rotatably constrained to the body portion 2, so as to allow the rotation of the blades about the rotation axis X, as schematically shown in the figures with the arrow R. To allow the rotation of the blades 3 with respect to the body portion 2, the blades 3 can be constrained to the body portion 2 by means of a pivot, or a hinge, or any other suitable means intended to allow a rotation of the blades about an axis X. The rotation axis X can be parallel to the plane defined by the body portion 2 that can be ring-shaped for a cylindrical exhaust pipe. In general the body portion 2 is adapted in shape and dimensions to the exhaust pipe 11, such that the mixer 1 can be installed in the exhaust pipe 11.

Therefore, the movement of the blades 3, and in particular the rotation about the rotation axis X, allow to modify the resistant section A and thus allow to modify the exhaust flow passage section of the exhaust pipe 11, inside which the mixer is arranged.

The rotation axis X can be perpendicular to the exhaust gas flow direction F inside the exhaust pipe 11 in which the mixer 1 is arranged.

As for example shown in figure 1, 2 and 3, the body portion 2 comprises an outer frame 2a which can be made by a strip of metal, or other suitable materials. The outer frame 2a is is adapted in shape and dimensionsto the cross section of the exhaust pipe 11 of the aftertreatment system 10 in which it has to be installed. According to an aspect of the invention, the outer frame 2a is a boundary frame of the mixer and it has a shape and dimensions such that it can be fitted in contact with the internal lateral surface of the exhaust pipe 11.

Different shapes of the body portion 2 and of the outer frame 2a can be provided according to different possible embodiments.

In the embodiment shown in figure 1 and 3, the body portion 2 comprises a circular-shaped outer frame 2a having a central axis Y. The blades 3 are movable with respect to the circular-shaped outer frame 2a to rotate about a rotation axis X. In other words, the blades 3 can be movably constrained to the circular-shaped outer frame 2a to rotate about a rotation axis X. The rotation axis X is arranged on the plane defined by the circular-shaped outer frame 2a, or on a plane parallel to it.

According to a possible embodiment, as for example shown in the embodiment of figure 3, the rotation axis X is radially arranged with respect to the central axis Y of the circular-shaped or ring-shaped outer frame 2a.

According to a possible embodiment, the rotation axis X of the blade 3 is directed perpendicularly with respect to the central axis Y of the circular-shaped outer frame 2a, as for example in the embodiment of figure 3.

According to another possible embodiment, as for example shown in figure 1, the rotation axis X is arranged parallel with respect to a radius of the circular-shaped outer frame 2a.

The mixer can be further provided with an inner frame 2b and the one or more blades 3 extend between the outer frame 2a and the inner frame 2b. The inner frame 2b can be also circular-shaped, as for example in the embodiment of figure 3, or it can be provided with different shapes, as for example in the embodiment of figure 2 disclosed here below. In fact, according to another possible embodiment, as for example shown in figure 2, the body portion 2 comprises a quadrangular-shaped outer frame 2a. More in detail the outer frame 2a isrectangular, but deviations from the rectangular configuration are possible.

According to this embodiment the plurality of blades 3 are arranged in rows and are rotatable about a rotation axis X, laying in the plane defined by the outer frame 2a, or on a plane parallel to it. The rotation axis X can extend between two opposite sides of the outer frame 2a. A connecting element 7 connects the rotation axes X of the blades to provide a simultaneous actuation.

The body portion 2 comprises an inner frame 2b, formed by a plurality of rods which extend between two oppos sides of the outer frame 2a. In the embodiment shown in figure 2, three parallel rods forming an inner frame 2b are provided. On each rod a plurality of blades 3 are constrained to be rotated about a rotation axis X that is parallel to the rods forming the inner frame 2b.

Also according to this embodiment, the movement of the blades, and in particular the rotation of the blades 3 about the rotation axis X allows to modify the resistant section A defined by the blades.

Returning now to the exhaust gas aftertreatment system 10 for an internal combustion engine 100, for example schematically shown in figures 4 and 5, it comprises an exhaust pipe 11 and at least one exhaust gas aftertreatment device 12 and a mixer 1 comprising a body portion 2, a plurality of movable blades 3 and at least one blade positioning device 5 to move the blades with respect to the body portion 2. The exhaust gas aftertreatment system 10 is further provided with an electronic control unit (ECU) 110, which can be the electronic control unit of the internal combustion engine 100.

The electronic control unit 110 is in communication with the mixer 1, and in particular with the blade positing device 5 and more in particular with the actuator 6, and also with one injector 20 arranged in the exhaust pipe 11, upstream of the mixer 1, for injecting at least one reactant in the exhaust gas flow.

The electronic control unit (ECU) 110 of the internal combustion engine 100, is connected to the injector 20 and also to a pump 16 to supply the required quantity of reactant.

In particular, ECU 110 operates the injector 20 to control the hydrocarbon and/or urea flow, or other suitable reactant to be injected inside the exhaust pipe 11.

The electronic control unit (ECU) 110 can be in communication with one or more sensors and/or devices associated with the internal combustion engine 100. The ECU 110 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the internal combustion engine 100. Furthermore, the ECU 110 may generate output signals to various control devices that are arranged to control the operation of the internal combustion engine 100. Note, dashed lines are used to indicate communication between the ECU 110 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 110, this apparatus may include a digital central processing unit (CPU) in communication with a memory system, or data carrier, and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals to/from the interface bus. The memory system may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to carry out the steps of such methods and control the internal combustion engine 100.

The program stored in the memory system is transmitted from outside via a cable or in a wireless fashion. Outside the electronic control unit it is normally visible as a computer program product, which is also called computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or non-transitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a Wi-Fi connection to a laptop.

In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

Instead of an ECU 110, the internal combustion engine 100 may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an onboard computer, or any processing module that might be deployed in the vehicle.

Will be now described the steps of the method of operating the exhaust gas aftertreatment system 10 comprising a mixer 1.

The method of operating the exhaust gas aftertreatment system 10 for an internal combustion engine 100 comprises the step of operating the internal combustion engine 100 to produce an exhaust gas flow in the exhaust pipe 11, the step of controlling at least one injector 20 arranged in the exhaust pipe 11 upstream of the mixer 1 for injecting at least one reactant in the exhaust gas flow, and the step of operating the blade positioning device 5 of the mixer 1 to move one or more blades 3 with respect to the body portion 2. The movement of the blades, i.e. the modification of the blade position allows to modify the resistance to the exhaust gas flow, and thus the resistant section A of the mixer. The blades are moved by the blade positioning device 5 and by means of an actuator 6, to modify the resistance to the flow (and thus the resistant section), depending on the flow rate of the exhaust gas in the exhaust pipe 11 produced by the internal combustion engine 100.

By doing so, the blades 3 of the mixer can be moved so as to modify the resistant section A to increase mixing optimization for a wide range of exhaust gas flow rate.

It has to be noted that the flow rate of the exhaust gas can be determined by means of a suitable sensor (not shown), eventually in combination with predetermined data and/or by means of the evaluation of the internal combustion engine operating point. According to different possible embodiments, the engine operating point can be determined by using different parameters, including the engine speed and/or the engine load.

The blades of the mixer can moved so as to modify the resistance to the exhaust gas flow (resistant section A), so that the mixer is more permeable when the mixing is not required, and in a particular when the injector 20 is deactivated and the reactant is not injected inside the exhaust pipe 11.

In fact, the method can comprise the step of operating the actuator 6 of the mixer 1 to move one or more blades 3 in a folded position or a a feathered position, providing a minimum resistance to the exhaust flow passing through the mixer (minimum resistant section), when the at least one injector 20 is deactivated.

The method described above may be carried out by means of a computer program comprising program codes (computer executable codes) for performing the method steps already described above.

The computer program comprises computer executable codes that can be stored on the ECU, or on a computer readable medium, or a storage unit, such as CD, DVD, flash memory, hard-disk, or the like.

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 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 as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS

1 Mixer 2 body portion 2a outer frame 2b inner frame 3 blade blade positioning device 6 actuator 6a actuation arm 7 connecting element A resistant section F exhaust gas flow direction R blade rotation directions X rotation axis of the blade Y central axis of the circular-shaped outer frame exhaust gas aftertreatment system 11 exhaust pipe 12 aftertreatment device 16 reactant pump 16a reactant reservoir 20 reactant injector internal combustion engine 101 fuel supply line 110 electronic control unit (ECU)

Claims

CLAIMS1. A mixer (1) for an exhaust gas aftertreatment system (10) of an internal combustion engine (100), comprising a body portion (2) provided with a plurality of movable blades (3) and a blade positioning device (5) to move one or more blades (3) with respect to said body portion (2).
2. The mixer (1) according to claim 1, wherein the blade positioning device (5) is configured to move one or more blades (3) with respect to said body portion (2) between a deployed position providing a maximum resistance to the flow passing through the mixer, and a folded position providing a minimum resistance to the flow passing through the mixer.
3. The mixer according to claim 1 or 2, wherein said blade positioning device (5) comprises an actuator (6).
4. The mixer according to claim 3, wherein said actuator (6) comprises an actuation arm (6a) coupled to one or more blades (3) to move one or more blades with respect to said body portion (2).
5. The mixer according to any previous claim, wherein said blade positioning device (5) comprises at least one connecting element (7) to conned two or more blades (3) to each other, said connected blades (3) being concurrently movable by the blade positioning device (5).
6. The mixer according to any previous claim, wherein one or more blades (3) comprise a rotation axis (X) and are rotatable with respect to said body portion (2) about said rotation axis (X).
7. The mixer according to any previous claim, wherein said body portion (2) comprises a circular-shaped outer frame (2a) having a central axis 00.
8. The mixer according to claim 7, wherein said blades (3) radially extends with respect to the central axis (Y) of the circular-shaped outer frame (2a).
9. The mixer according to any claim 1 to 6, wherein said body portion (2) comprises a quadrangular-shaped outer frame (2a).
10. The mixer according to any claim 7 to 9, further comprising an inner frame (2b), and said blades (3) extend between said outer frame (2a) and said inner frame (2b).
11. An exhaust gas aftertreatment system (10) for an internal combustion engine (100), comprising an exhaust pipe (11) and at least one exhaust gas aftertreatment device (12), further comprising at least one mixer (1) according to any of the previous claims, said mixer (1) being arranged in said exhaust pipe (11) upstream of said exhaust gas aftertreatment device (12), the exhaust gas aftertreatment system (10) further comprising at least one injector (20) arranged upstream of said mixer (1) for injecting at least one reactant in the exhaust gas flow.
12. A method of operating an exhaust gas aftertreatment system (10) for an internal combustion engine (100) according to claim 11, comprising the steps of: * operating said internal combustion engine (100) to produce an exhaust gas flow in the exhaust pipe (11); * controlling at least one injector (20) arranged in said exhaust pipe (11) upstream of at least one mixer (1) for injecting at least one reactant in the exhaust gas flow; * operating a blade positioning device (5) of the mixer (1) to move one or more blades (3) with respect to the body portion (2).
13. The method according to claim 12, wherein said blade positioning device (5) of the mixer (1) is operated to move one or more blades (3) with respect to the body portion (2), to modify the resistance to the exhaust gas flow passing through the mixer, depending on the flow rate of the exhaust gas in the exhaust pipe (11) produced by the internal combustion engine.
14. The method according to claim 12 or 13, wherein when said at least one injector (20) is deactivated, said blade positioning device (5) of the mixer (1) is operated to move one or more blades (3) with respect to the body portion (2) in a folded position providing a minimum resistance to the exhaust flow passing through the mixer.