DE102020131428A1 - Evaporator module and exhaust aftertreatment system with such a module - Google Patents

Abstract

The present disclosure relates to an evaporator module for an exhaust gas aftertreatment system for a vehicle.
The module comprises an injection nozzle shield cap (28), a flow guide device (24), a mixer (22), an evaporation chamber (16) and a plurality of spacer arms (36). The mixer (22) is arranged in the evaporation chamber (16) at an upstream end of the evaporation chamber. Each of the plurality of spacer arms (36) is attached at a first end to the upstream end of the evaporation chamber (16) and is attached at a second end to the injector shield cap (28) so that the injector shield cap is fixed at a distance from the mixer (22) . The flow guide device (24) is attached to the injection nozzle shield cap (28) in such a way that the flow guide device (24) is arranged between the mixer (22) and the injection nozzle shield cap (28) at a predetermined distance from the mixer (22).
The disclosure also relates to an exhaust gas aftertreatment system with such a module. The disclosure also relates to a vehicle with such an exhaust gas aftertreatment system.

Description

Technical area

The present disclosure relates to a module for an exhaust gas aftertreatment system for a vehicle and an exhaust gas aftertreatment system with such a module. The disclosure also relates to a vehicle with such an exhaust gas aftertreatment system.

background

Emissions standards for motor vehicles are becoming increasingly strict. Such standards typically define maximum emission levels for a range of tailpipe pollutants including carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NO _x ) and particulate matter (PM). In order to meet the requirements of current and presumed future standards, vehicles must be equipped with emission reduction technologies.

Selective Catalytic Reduction (SCR) is an effective technology to reduce tailpipe nitrogen oxide (NO _x ) emissions. It involves adding a reducing agent such as ammonia to the vehicle exhaust stream. The reducing agent uses a catalyst to reduce NO _x in the exhaust gas stream to nitrogen gas (N ₂ ) and water. In practical applications in motor vehicles, an aqueous urea solution is used as the reducing agent, and this urea solution is decomposed in the hot exhaust gas stream to form ammonia and carbon dioxide.

It is desirable to be able to remove substantially all of the NO _{x from the exhaust stream by using only SCR.} However, there are difficulties with this. In order to produce the amounts of ammonia required to reduce substantially all of the NO _x , large amounts of urea solution must be injected into the exhaust gas stream. In order to be able to use injected urea and _{to be able to reduce NO x} emissions with high efficiency via the SCR, an effective reducing agent distribution in the exhaust gas flow is essential. Uneven distribution can lead to the deposition of urea and urea degradation products on surfaces downstream of the injection site. In some cases it may be necessary to disassemble the aftertreatment system to remove such deposits. In addition, if the reducing agent is not evenly distributed over the SCR catalytic converter, the catalytic converter may have to be designed for the maximum reducing agent flow, which means that some catalytic converters will be oversized, which is wasteful from an environmental point of view and from an economic point of view. Alternatively, excess urea must be injected in order to fully supply all catalytic converters with reducing agent. This excess urea will require the use of a larger ammonia slip catalyst to avoid tailpipe ammonia emissions.

It is known to provide a mixer downstream of a reducing agent injection nozzle in the exhaust gas aftertreatment system. The mixer produces a rotation of the exhaust gases and provides an improved distribution of the reducing agent in the exhaust gas for any given volume of an evaporation chamber. Further means for directing the flow of exhaust gases can also be arranged in the aftertreatment system to cooperate with the mixer and provide improved reductant distribution in the exhaust gas flow.

There remains a need for exhaust aftertreatment systems that provide improved reductant distribution in the exhaust stream.

Summary of the invention

The inventors of the present invention have found a number of disadvantages in prior art solutions for achieving good reducing agent distribution in the exhaust gas stream. Systems that use a mixer and flow guide can provide good distribution when the various components are optimally positioned with respect to one another. However, small differences in the spatial arrangement of the components can cause significant degradation in the performance of the system. For example, a deviation of a few millimeters in the distance between a flow guide device and the mixer can reduce the amount of reducing agent that can be metered into the system without causing a deposit by up to 25%.

In systems known from the prior art, the mixer and the flow guide device are welded to separate parts located in the vicinity of one another. The chain of tolerances between the mixer and the guide plate is long, which impairs the ability to precisely control the spatial arrangement of these components, for example with regard to the distance between the components and / or the alignment of the components. After assembly of the aftertreatment system, the components are enclosed in a hidden space, which limits the possibility of checking the spatial arrangement of the components with respect to one another and / or correcting the spatial arrangement if it is found to be unduly deviated.

It is therefore an object of the present invention to obviate or mitigate at least some of the disadvantages described above. In particular, it would be desirable to provide a device for distributing reducing agent in the exhaust gas flow, which provides a consistently good distribution and can be easily checked.

These objects are achieved by the module for an exhaust gas aftertreatment system according to the attached patent claims. The exhaust aftertreatment system is preferably intended for a vehicle. The module includes: an injector shield cap, a flow guide, a mixer, a vaporization chamber, and a plurality of spacer arms. The mixer is arranged in the evaporation chamber at one end of the evaporation chamber. Each of the plurality of spacer arms is attached to the end of the vaporization chamber at a first end and is attached to the injector shield cap at a second end such that the injector shield cap is fixed at a distance from the mixer. The flow guide device is attached to the injection nozzle shielding cap in such a way that the flow guide device is arranged at a predetermined distance from the mixer between the mixer and the injection nozzle shield cap.

Such a module can reduce the power fluctuation within the system by ensuring an optimal and highly reproducible distance between the mixer and the flow guide device. This is done by ensuring that the chain of tolerances between the mixer and the flow directing device is reduced and by allowing the relative spatial arrangement of the mixer and the flow directing device to be controlled during assembly. A check of the spatial arrangement of the mixer and the flow guide device in relation to one another can become easier, since an arrangement in the relatively accessible module can be checked before the unit is introduced into the hidden space of the exhaust gas aftertreatment system.

The mixer, the flow guide device and the injection nozzle shielding cap can each be arranged coaxially to the evaporation chamber. The module allows a reproducibly excellent coaxiality between these components, which further contributes to ensuring good and highly reproducible performance.

The mixer, the flow guide device and the injection nozzle shielding cap can each be arranged normal to a longitudinal axis of the evaporation chamber. The module allows a reproducibly excellent collinearity between these components, which further contributes to ensuring good and highly reproducible performance.

The multiple spacer arms can be made integral with the vaporization chamber. This leads to a simple and robust way of providing spacer arms attached to the evaporation chamber. Alternatively or additionally, the spacer arms can be manufactured separately from the evaporation chamber. Such spacer arms can be attached to the end of the evaporation chamber. This represents a material-effective way of providing an evaporation chamber with spacer arms.

The multiple spacer arms can consist of three to five spacer arms. The spacer arms can be evenly distributed around a circumference of the evaporation chamber. Each of the plurality of spacer arms can have a width of less than 5% of the circumference of the evaporation chamber, preferably less than 2%. This helps ensure that the spacer arms do not unduly obstruct the flow of exhaust gases during operation.

The flow guide device can be attached to the mixer. This can further increase the robustness of the module. The flow guide device can be attached to the mixer using fixing lugs, for example three evenly spaced fixing lugs.

The flow guide may be attached to the injector shield cap using spacer tabs. The spacer tabs can be manufactured integrally with the flow guide device. For example, the flow guide may be attached to the injector shield cap using three to five spacer tabs.

According to a further aspect of the invention, the objects of the invention are achieved by a method of manufacturing a module according to the appended claims. The method relates to a production of a module for an exhaust gas aftertreatment system as disclosed herein. The procedure consists of the following steps.

A first unit is provided which comprises a vaporization chamber, a mixer arranged in the vaporization chamber at one end of the vaporization chamber, and a plurality of spacer arms. Each of the plurality of spacer arms is attached at a first end to the end of the evaporation chamber and extends from the end of the vaporization chamber to a second end.

A second unit is provided which comprises a flow guide device attached to an injection nozzle shield cap.

The first unit is then attached to the second unit by attaching the injector shield to the second ends of the plurality of spacer arms such that the flow guide is between the mixer and the injector shield.

Such a method allows a controllable and easily verifiable possibility of providing a module which has a predetermined and reproducible distance between the mixer and the flow guide device.

The evaporation chamber and the plurality of spacer arms can be integrally formed by cutting a sheet of material such that when the sheet of material is rolled to form a evaporation chamber, the plurality of spacer arms are provided at the end of the evaporation chamber. This is a simple and robust way of providing a vaporization chamber that has spacer arms extending from one end.

According to a further aspect of the invention, the objects of the invention are achieved by an exhaust gas aftertreatment system according to the accompanying patent claims. The exhaust aftertreatment system is preferably intended for a vehicle. The exhaust aftertreatment system includes a module as disclosed herein, a reductant injector disposed within the injector shield cap, and an exhaust conduit in fluid communication with the end of the vaporization chamber.

At least one of the plurality of spacer arms can be arranged in the exhaust pipe in such a way that, during operation, it breaks an exhaust gas flow flowing from the exhaust pipe into the evaporation chamber. By providing such a placement, the metering and distribution of reducing agent can be further improved.

The exhaust gas aftertreatment system can further comprise a particulate filter and / or a diesel oxidation catalytic converter. The diesel oxidation catalyst and the particle filter can be separate components or the particle filter can be equipped as a catalyzed particle filter with a diesel oxidation catalyst functionality.

According to yet another aspect of the invention, the objects of the invention are achieved by a vehicle having an exhaust aftertreatment system as disclosed herein.

Other objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from the following detailed description.

Figure list

• 1 schematisch ein Fahrzeug mit einem Abgasnachbehandlungssystem zeigt,
• 2 schematisch eine geschnittene Draufsicht eines Abgasnachbehandlungssystems aus dem Stand der Technik darstellt,
• 3 schematisch eine vergrößerte Ansicht des Teils des Nachbehandlungssystems aus dem Stand der Technik nahe dem stromaufwärtigen Ende der Verdampfungskammer zeigt,
• 4 schematisch ein Verdampfermodul gemäß einer beispielhaften Ausführungsform der vorliegenden Offenbarung zeigt,
• 5 schematisch ein Abgasnachbehandlungssystem gemäß einer beispielhaften Ausführungsform der vorliegenden Offenbarung zeigt,
• 6 schematisch eine vergrößerte Ansicht des Teils des beispielhaften Nachbehandlungssystems in der Nähe des stromaufwärtigen Endes der Verdampfungskammer zeigt,
• 7 ein Fließbild ist, welches eine beispielhafte Ausführungsform eines Verfahrens zur Herstellung eines Verdampfermoduls darstellt.

For a more complete understanding of the present invention and other objects and advantages thereof, the detailed description below should be read in conjunction with the accompanying figures, in which the same reference characters designate the same items in the different views and in which:

• 1 shows schematically a vehicle with an exhaust aftertreatment system,
• 2 schematically represents a sectional top view of an exhaust gas aftertreatment system from the prior art,
• 3 schematically shows an enlarged view of the portion of the prior art aftertreatment system near the upstream end of the evaporation chamber;
• 4th schematically shows an evaporator module according to an exemplary embodiment of the present disclosure,
• 5 schematically shows an exhaust aftertreatment system according to an exemplary embodiment of the present disclosure,
• 6th schematically shows an enlarged view of the portion of the exemplary aftertreatment system near the upstream end of the evaporation chamber;
• 7th Figure 12 is a flow diagram illustrating an exemplary embodiment of a method of making an evaporator module.

Detailed description

The present disclosure relates to an exhaust gas aftertreatment system with an improved evaporator module for ensuring excellent and reproducible reducing agent distribution in the exhaust gas flow during operation. By reproducible it is meant that mass-produced copies of the evaporator module consistently offer excellent reducing agent distribution and that there are consequently slight differences between different copies.

The exhaust gas aftertreatment system comprises at least one evaporator module, an exhaust line and a reductant injector. It can furthermore comprise further components which are arranged upstream or downstream of said components. Upstream and downstream respectively refer to locations in the exhaust aftertreatment system with reference to the typical direction of flow of exhaust gas from the engine to the tailpipe. One component is said to be upstream of another when it is closer to the engine in the exhaust system, whereas it is said to be downstream when it is closer to the tailpipe in the exhaust system.

The evaporator module comprises an injection nozzle shield cap, a flow guide device, a mixer and an evaporation chamber. In prior art modules having such components, the mixer is typically attached to the vaporization chamber, whereas the injector shield cap and flow guide are typically attached to another component of the exhaust aftertreatment system, such as an end cap.

As a result, the chain of tolerances between the mixer and the flow guide device is excessively long, i.e. the cumulative sum of all tolerances leads to an excessively large tolerance in the dimensional arrangement of the flow guide device in relation to the mixer. It has been found that the distribution capacity of the evaporator module is highly sensitive with regard to the dimensional module of the mixer and the flow guide device and in particular with regard to the distance between these components. For example, it has been found that in systems that are designed to dose urea in relatively high proportions without a deposit of urea or degradation products on the walls or components of the evaporator module, a slight increase in the distance between the mixer and the flow guide device to a Deposit at proportions that are 40% lower can result.

The evaporator module according to the present disclosure helps to overcome such problems. The mixer is arranged in the evaporation chamber at an upstream end of the evaporation chamber. The injector shield cap is attached to this upstream end using a plurality of spacer arms. The flow guide is attached to the injector shield cap. Such an arrangement has the effect of considerably shortening the tolerance chain between the mixer and the flow guide device, which makes it much easier to ensure that the spatial arrangement of the mixer relative to the flow guide device is within predetermined tolerances. In addition, because the module is assembled before being inserted into the exhaust gas aftertreatment system, it is much easier to check that the spatial arrangement of the mixer and the flow guide device meet the specified requirements.

The evaporation chamber provides a volume in which reducing agent metered into the exhaust gas flow can evaporate and can be distributed in the exhaust gas flow. The evaporation chamber can typically be formed by a section of pipe. It can be provided with fins on its outside in order to improve heat conduction and to facilitate evaporation of the reducing agent. For example, it can be provided with more than 100 lamellae around its outer circumference, wherein the lamellae can be formed, for example, by corrugation and laser welding of a separate metal sheet onto the evaporation chamber.

A mixer is arranged at the upstream end of the evaporation chamber. The mixer can help to impart a rotational flow to the exhaust gas flow and in this way to increase the flow length for the exhaust gas in the evaporation chamber. The mixer is typically fixedly mounted in the evaporation chamber and typically has a plurality of blades or vanes that extend radially from a central area, similar in appearance to a rotor or propeller. The mixer is typically coaxial with the evaporation chamber, i.e. a central axis of the mixer corresponds to the cylinder central axis of the evaporation chamber.

A plurality of spacer arms are arranged at the upstream end of the evaporation chamber. The spacer arms are attached to the evaporation chamber at a first end and extend longitudinally away from the evaporation chamber to a second end. In this context, by attached it is meant either attached or attached by being made in one piece with the evaporation chamber. The purpose of the spacer arms is to secure the injector shield cap in a predefined spatial relationship with the mixer. Only two spacer arms may be required to accomplish this purpose, but from three to five arms are typically used for stability and ease of assembly, although more can be used if desired. These arms are sufficiently wide to give the arrangement the required stability, but they should not be so wide that they unduly impede the flow of exhaust gas. For example, each arm can have a width that is less than 5% of the circumference of the evaporation chamber, for example less than 2% of the width of the evaporation chamber. The arms can be evenly distributed around the circumference of the evaporation chamber. However, in some cases it may be desirable to provide an uneven distribution, for example to control the flow of exhaust gas. The arms can all have the same width, but they can also differ in width, for example if a certain arm is provided to divert the flow of exhaust gas.

The spacer arms secure the injector shield cap in place relative to the vaporization chamber and mixer. The injection nozzle shield cap is a cap-shaped component, with the outer (concave) surface of the cap facing the mixer. The reducing agent injection nozzle can be mounted inside (on the concave side) of the cap. Exhaust gas does not need to enter the interior of the cap and the injector is thus shielded from the heat and contaminants in the exhaust gas. A hole is provided in the bottom of the cap to allow the reductant injector to spray reductant towards the mixer and into the exhaust stream.

A flow guide is disposed between the mixer and the injector shield cap. The flow directing device aids in directing the flow of exhaust gas in order to achieve effective evaporation and distribution of reducing agent in the exhaust gas. The flow guide device is fastened to the injection nozzle shielding cap and is in this way also fastened in a predetermined spatial relationship to the mixer. For example, the flow guide may be attached to the injector shield cap using a series of attachment tabs. These tabs can, for example, be an integral part of the flow guide device. The flow guide is typically frustoconical (volcanic) in shape and is typically arranged to progressively narrow towards the mixer. The flow guide device can have an inner guide element (“crater”) which widens in the direction of the mixer.

The module described makes it possible to fasten the evaporation chamber, the mixer, the flow guide device and the injection nozzle shielding cap with respect to one another with relatively small tolerances. In this way, for example, the gap between the mixer and the flow guide device can be controlled in an accurate and precise manner. Each of the components can be oriented so that they have a common axis and each is normal to the cylinder axis of the evaporation chamber, i.e. that they have a coaxial and collinear arrangement.

The components of the evaporator module can be made of any suitable material. For example, they can consist of stainless steel, which is corrosion-resistant and can withstand the temperatures prevailing in the exhaust gas aftertreatment system during operation. They can be made using any suitable method such as casting, molding, forming, or machining. The evaporation chamber can be made by rolling a sheet metal to form the chamber. The plurality of spacer arms can be made integral with this chamber by cutting the sheet metal at its ends to form the arms, either before or after rolling.

The evaporator module is a component of the exhaust aftertreatment system. It can be installed by inserting it into an already existing exhaust pipe in the exhaust gas aftertreatment system in such a way that part of the exhaust gas flows past the walls of the evaporation chamber. Alternatively, it can form part of the exhaust line of the exhaust gas aftertreatment system in such a way that essentially all of the exhaust gas flows through the evaporation chamber. Another exhaust line is arranged to receive the exhaust gases leaving the evaporation chamber and to direct them downstream to downstream components such as an SCR catalytic converter. The SCR catalytic converter can be designed as a separate module.

A diesel oxidation catalytic converter and a particle filter can be arranged in the aftertreatment system upstream of the evaporator module. They can be arranged as separate components or can be combined as a catalyzed particulate filter. An exhaust line guides exhaust gases from an outlet of the particle filter to the upstream end of the evaporation chamber, past the flow guide device or through it. It has been found to be advantageous that at least one arm of the plurality of spacer arms is arranged to break the exhaust gas flow in the exhaust gas line, i.e. the arm faces "upstream". This can further improve the reducing agent metering and distribution of the exhaust gas aftertreatment system.

The invention will now be described in more detail with reference to certain exemplary embodiments and the figures. However, the invention is not restricted to the exemplary embodiments explained herein and / or shown in the figures, but can be varied within the scope of protection of the appended claims. In addition, the figures should not be considered to be to scale, as some Features may be exaggerated to make certain features clearer.

1 shows schematically a side view of a vehicle 1 according to one embodiment of the invention. The vehicle 1 contains an internal combustion engine 2 and one in an exhaust pipe 10 arranged exhaust aftertreatment system 4th . The exhaust pipe 10 leads exhaust gases from the engine 2 through the exhaust aftertreatment system 4th and further to expel the treated exhaust gases. The vehicle 1 can be a heavy vehicle, for example a truck as shown here, a tractor or a bus. The vehicle 1 can alternatively be a car. The vehicle may be a hybrid vehicle having an electric machine (not shown) in addition to the internal combustion engine 2 be. Alternatively, the vehicle can be a marine vehicle, such as a ship. The invention can also be used for exhaust aftertreatment in non-vehicle engine systems, such as generators.

2 Figure 11 schematically illustrates an example of an exhaust aftertreatment system 4th from the prior art in a cross-sectional view. The system 4th includes a diesel oxidation catalyst 6th and a particulate filter 8th in a first section of pipe 10 are arranged. In a second section of the pipe 12th there is an evaporation chamber 16 . Slats 18th are on the outside of the evaporation chamber 16 present to improve heat transfer. A graduation cap 20th forms an exhaust pipe between the first pipe section 10 and the second length of pipe 12th . A mixer 22nd is in the evaporation chamber 16 located at the upstream end. A flow guide device 24 is immediately upstream of the mixer 22nd arranged. The flow guide device 24 is by means of fastening straps 26th on an injector shield cap 28 appropriate. An injector 30th is located within the injector shield cap to provide reductant to the aftertreatment system. The injector shield cap 30th is on the end cap 20th appropriate. Downstream of the exhaust aftertreatment system 4th an SCR catalytic converter can be arranged.

Due to the many manufacturing tolerances between the components that make up the mixer 22nd and the flow guide device 24 attached, the spacing, relative angle, and orientation of these components can vary significantly, negatively affecting the system's ability to dispense metered reductant. This is in 3 which is an enlargement of the upstream part of the evaporation chamber 16 and surrounding components 2 shows. Due to a series of slight deviations from the optimal position, each deviation lying within manufacturing tolerances, the relative spatial arrangement of the mixer deviates 22nd and the flow guide device 24 in terms of the distance g between them, the orientation and the angle clearly from the optimal arrangement, as by the central axis 32 the flow guide device 24 and the central axis 34 of the mixer 22nd shown.

4th shows schematically an exemplary embodiment of an evaporator module 14th according to the present disclosure. The evaporator module includes an evaporator chamber 16 , a mixer 22nd , a flow guide device 24 and an injector shield cap 28 . The mixer 22nd is in the upstream end of the evaporation chamber 16 appropriate. Multiple spacer arms 36 attach the injector shield cap 28 at the evaporation chamber 16 and fix these components in a predetermined spatial arrangement. The flow guide device 24 is by means of fastening straps 26th on the injector shield cap 28 attached, and thereby the flow guide device is also in a predetermined spatial arrangement with respect to the mixer 22nd held. You can see the arrangement of the mixer 22nd with respect to the flow guide 24 before attaching the evaporator module 14th within the exhaust aftertreatment system 4th can be easily inspected.

5 shows schematically an exemplary embodiment of an exhaust gas aftertreatment system in a cross-sectional top view, which has an evaporator module as described herein. The system 4th includes a diesel oxidation catalyst 6th and a particulate filter 8th in a first section of pipe 10 are arranged. In a second section of the pipe 12th the evaporator module is located 14th . The evaporator module 14th has an evaporation chamber 16 that are on the outside with slats 18th is provided, a mixer 22nd , a flow guide device 24 , an injector shield cap 28 and spacer arms 36 on. A graduation cap 20th forms together with the injector shield cap 28 an exhaust pipe between the first pipe section 10 and the second length of pipe 12th . An injector 30th is inside the injector shield cap 28 arranged to deliver reductant to the aftertreatment system. An SCR catalytic converter can be installed downstream of the exhaust aftertreatment system 4th be arranged. You can see a spacer arm 36 is arranged for this purpose, one in the second pipe section 12th breaking incoming exhaust gas flow. This can help to further improve a distribution of reducing agent in the exhaust gases.

6th shows an enlargement of the upstream part of the evaporation chamber 16 and surrounding components 4th . One can see that due to the use of spacer arms 36 the tolerance chain between the mixer 22nd and the flow guide device 24 is shortened. This makes it possible to position these components precisely and precisely spatially in relation to one another with regard to the distance g, the orientation and the angle, as by the collinearity of the central axis 32 the flow control device 24 and the central axis 34 of the mixer 22nd shown.

The evaporator module can be made as follows and as in the flow sheet 4th shown.

Step s701 marks the start of the manufacturing process.

A first unit is provided in step s703. The first unit comprises an evaporation chamber, a mixer arranged in the evaporation chamber at one end of the evaporation chamber, and a plurality of spacer arms. Each of the plurality of spacer arms is attached at a first end to the end of the evaporation chamber and extends from the end of the evaporation chamber to a second end, such as in FIG 4th shown.

In step s705 a second unit is provided. The second unit includes a flow guide attached to an injector shield cap, such as in FIG 4th shown.

In step s707, the first unit is attached to the second unit by attaching the injector shield cap to the second ends of the plurality of spacer arms such that the flow guide is disposed between the mixer and the injector shield cap, such as in FIG 4th shown.

Step s709 denotes the end of the manufacturing process.

In an optional step s702, the evaporation chamber and the plurality of spacer arms are made integrally by cutting a sheet of material such that when the sheet of material is rolled to form an evaporation chamber, the plurality of spacer arms are at the end of the evaporation chamber.

Claims (15)

Module (14) for an exhaust gas aftertreatment system (4), the module having an injection nozzle shielding cap (28), a flow guide device (24), a mixer (22), an evaporation chamber (16) and a plurality of spacer arms (36), wherein the mixer (22) is arranged in the evaporation chamber (16) at one end of the evaporation chamber, wherein each of the plurality of spacer arms (36) is attached at a first end to the end of the vaporization chamber (16) and at a second end to the injector shield cap (28) such that the injector shield cap is attached at a distance from the mixer (22) , and wherein the flow guide device (24) is attached to the injection nozzle shield cap (28) such that the flow guide device (24) is arranged between the mixer (22) and the injection nozzle shield cap (28) at a predetermined distance from the mixer (22). Module after Claim 1 , in which the mixer (22), the flow guide device (24) and the injection nozzle shielding cap (28) are each arranged coaxially to the evaporation chamber. Module according to one of the preceding claims, in which the mixer (22), the flow guide device (24) and the injection nozzle shielding cap (28) are each arranged normal to a longitudinal axis of the evaporation chamber. Module according to one of the preceding claims, in which the plurality of spacer arms (36) are made in one piece with the evaporation chamber (16). The module of any preceding claim, wherein the plurality of spacer arms (36) are made separate from the evaporation chamber and are attached to the end of the evaporation chamber (16). The module of any preceding claim, wherein the plurality of spacer arms (36) consist of three to five spacer arms. Module according to one of the preceding claims, in which the plurality of spacer arms (36) are evenly distributed around a circumference of the evaporation chamber (16). Module according to one of the preceding claims, in which each of the plurality of spacer arms (36) has a width of less than 5%, preferably less than 2%, of a circumference of the evaporation chamber. Module according to one of the preceding claims, in which the flow guide device (24) is attached to the mixer (22). Method for producing a module for an exhaust gas aftertreatment system according to one of the Claims 1 to 9 the method comprising the steps of: a) providing (s703) a first unit having a vaporization chamber (16), a mixer (22) arranged in the vaporization chamber at one end of the vaporization chamber, and a plurality of spacer arms (36), each of the plurality of spacer arms is attached at a first end to the end of the evaporation chamber and extends from the end of the evaporation chamber to a second end, b) providing (s705) a second unit with a flow guide device (24) which is attached to an injection nozzle shield cap (28) , and c) attaching (s707) the first unit to the second unit by attaching the injector shield cap (28) to the second ends of the plurality of spacer arms (36) so that the flow directing device (24) is between the mixer (22) and the injector shield cap (28 ) is arranged. Procedure according to Claim 10 wherein the evaporation chamber (16) and the plurality of spacer arms (36) are integrally made by cutting a sheet of material such that when the sheet of material is rolled to form an evaporation chamber, the plurality of spacer arms are provided at the end of the evaporation chamber. Exhaust aftertreatment system (4), wherein the exhaust aftertreatment system comprises a module (14) according to one of the Claims 1 to 9 and a reductant injector nozzle (30) disposed within the injector nozzle shield cap (28) and having an exhaust conduit (21) in fluid communication with the end of the vaporization chamber (16). Exhaust aftertreatment system after Claim 12 , in which at least one of the plurality of spacer arms (36) is arranged in the exhaust pipe (21) in such a way that, during operation, it breaks an exhaust gas flow flowing from the exhaust pipe (21) into the evaporation chamber (16). Exhaust aftertreatment system according to one of the Claims 12 to 13th , further comprising a particle filter (8) and / or a diesel oxidation catalyst (6). Vehicle (1) with an exhaust gas aftertreatment system (4) according to one of the Claims 12 to 14th .

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