SE535800C2 - Arrangement and method for the incorporation of reducing agents in an SCR system - Google Patents

Abstract

SUMMARY The invention relates to an arrangement for efficient mixing of reducing agents and exhaust gases for an SCR system, comprising a dosing unit (250) for dosing said reducing agent into a single exhaust duct upstream of a catalyst unit, where the means (310) present primarily in the exhaust duct for the distribution of metered-in reducing agent; - means (320) primarily arranged for evaporating metered-in reducing agent; and - means (330; 340) primarily arranged for creating mixed turbulence in a mixture of metered-in reducing agent and said exhaust gases, arranged upstream of said catalyst unit. also a process for efficient mixing of reducing agents and exhaust gases for an SCR system according to the invention. The invention also relates to an engine equipped with the arrangement. (Fig. Se)

Description

It is desirable that the reducing agent injected into the exhaust pipe be mixed well with an exhaust gas stream therein before the mixture reaches the SCR catalyst.

In a case where said injected reducing agent is not mixed in the desired manner, inner walls of the exhaust pipe can be wetted, thereby causing an increased risk of crystal formation of the urea dissolved in the reducing agent. Crystallization of urea in the exhaust pipe can in the long run lead to deteriorating performance of the vehicle due to partial or complete clogging of the exhaust pipe.

It is further desirable that the reducing agent be mixed well with the exhaust gases before the mixture reaches the SCR catalyst, so that said reaction between reducing agent and NOx gas can take place with optimized efficiency. There are today different ways of achieving an effective mixture of reducing agent and exhaust gases in vehicles. equipped with an SCR system. Document US 2009/0025368 A1 discloses a system comprising a nozzle for injecting urea into an exhaust passage and a mixing device in the form of a mixing plate. The mixing plate is arranged to stimulate mixing of the injected urea solution and the exhaust gases from the internal combustion engine. The mixing plate has four openings through which the mixture fl deserts. When flowing through the openings, a turbulent fate is created which produces an efficient mixture of the injected urea solution and the exhaust gases. Although the technology disclosed in US 2009/0025368 A1 works satisfactorily for a number of SCR systems, there is a desire to provide an improved mixing configuration to enable further reduction of the amount of unwanted emissions from motor vehicles in operation.

There is a need to improve the current SCR system to further improve performance. There is today a problem regarding handling the amount of reducing agent added in an exhaust system of an SCR system in a desired manner. SUMMARY OF THE INVENTION An object of the present invention is to provide a new and advantageous arrangement for efficient mixing of reducing agents and exhaust gases for an SCR system.

An object of the present invention is to provide a new and advantageous process for efficient mixing of reducing agents and exhaust gases for an SCR system.

An object of the present invention is to provide an arrangement of an SCR system which provides a reduced risk of crystal formation of reducing agents.

Another object of the present invention is to provide an SCR system with improved performance, in particular as regards the reduction of the amount of unwanted emissions from the SCR system.

Another object of the present invention is to provide an SCR system with an optimized use of dosed reducing agent.

A further object of the invention is to provide an alternative arrangement for efficient mixing of reducing agents and exhaust gases for an SCR system and an alternative method for efficient mixing of reducing agents and exhaust gases of an SCR system.

These objects are achieved with an arrangement according to claim 1.

According to one aspect of the invention, there is provided an arrangement for efficient mixing of reducing agents and exhaust gases for an SCR system, comprising a dosing unit for dosing said reducing agent into an exhaust passage 535,800 upstream of a catalyst unit, where in the exhaust passage of dosed reducing agent; - agents primarily provided for the evaporation of dosed reducing agent; and - means primarily arranged for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases, arranged upstream of said catalyst unit.

By combining said agents, an effective mixture of metered reducing agent and said exhaust gases can be achieved. According to one aspect of the invention, substantially the entire metered amount of reducing agent is first atomized by suitable distribution means, after which the distributed amount of reducing agent is largely evaporated by means of dedicated evaporating means. In this way, an increased proportion of vaporized reducing agent is produced in the exhaust duct compared to the prior art where no distribution or evaporating means are provided.

The vaporized reducing agent can be effectively mixed with the exhaust gases in the exhaust duct by a plurality of mixing means intended for that purpose.

When the mixture of vaporized reducing agent and the exhaust gases is fed to the SCR catalyst, a catalyticization process can be carried out at a relatively high efficiency, which entails a number of advantages, such as e.g. a lower amount of unwanted emissions in the SCR system.

By combining said means, synergistic effects with respect to functionality of components included in the arrangement are advantageously achieved.

Since a metered amount of reducing agent can be mechanically atomized in a desired manner by the distributing means, a larger amount of reducing agent can be evaporated by means of the evaporating means compared with an arrangement without distributing means. Similarly, a larger amount of vaporized reducing agent can be advantageously mixed with exhaust gases in the exhaust duct when using the evaporating means compared to an arrangement without evaporating means. In this case, a self-reinforcing effect is achieved within the 535,800 arrangement, which results in a more efficient use of the dosed amount of reducing agent. In other words, an arrangement is provided where a smaller amount of reducing agent added can provide a substantially unchanged efficiency of the SCR catalyst.

Said means for distribution may comprise a unit comprising at least one metal wire. This at least one metal wire may preferably be arranged in the form of a ball-like configuration in order to enable a mechanical distribution of said dosed reducing agent. Said reducing agent distribution means can break up a spray image of reducing agent dosed by the dosing unit so that an atomization of said reducing agent is effected. This has the effect of enabling a more efficient mixture of reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

Said evaporation means may comprise at least one sheet in the form of a sheet to provide an improved evaporation of said dosed reducing agent. According to one embodiment, said means for evaporating reducing agent comprise a plurality of plates which are separated by a mutual distance from each other. In this case, an improved evaporation of the reducing agent in the exhaust duct can be achieved. According to one embodiment, said plates are stacked on top of each other and separated by a mutual distance. This has the effect of providing a compact unit for evaporating reducing agent. According to one embodiment, at least one sheet is folded with an arbitrary number of folds. This has the effect that a larger total area intended for evaporating reducing agents is provided, whereby a compact unit for evaporating reducing agents is provided. Said plate can be of any dimension, e.g. a thin plate of 5x10 centimeters. Said sheet may be made of any material, such as e.g. a metal, e.g. aluminum, or an alloy, e.g. stainless steel. Said means for evaporating reducing agents have the effect of enabling a more efficient mixture of 535,800 reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

Said means for creating mixing turbulence may comprise at least one fin fixed to an inner wall of the exhaust duct. Any number of fins may be provided in the exhaust duct to provide a more efficient mixture of metered (possibly mechanically distributed and vaporized) reducing agents and exhaust gases upstream of the SCR catalyst. Said at least one fin may be of suitable size and configuration. Said means for creating turbulence, comprising at least one fin, have the effect of enabling a more efficient mixing of reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

Said means for creating mixing turbulence may comprise at least one blade arranged at an inner wall of the exhaust duct. Any number of blades can be provided in the exhaust duct to provide a more efficient mixture of metered (possibly mechanically atomized and vaporized) reducing agent and exhaust gases upstream of the SCR catalyst. Said leaves may be of suitable size and configuration. Said turbulence generating means, comprising at least one blade, has the effect of enabling a more efficient mixing of reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

Said means for creating mixing turbulence may comprise at least one three-dimensional object arranged at an inner wall of the exhaust duct. Any number of three-dimensional objects can be arranged in the exhaust duct to provide a more efficient mixture of metered (possibly mechanically distributed and vaporized) reducing agent and exhaust gases upstream of the SCR catalyst. Said objects may be of suitable size and configuration. for example a cylinder or hollow cone. Said turbulence generating means, comprising at least one three-dimensional object, has the effect of enabling a more efficient mixing of reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

Said means for creating mixing turbulence may comprise at least one rotatably stored propeller blade, or a rotatably stored turbine blade, which can rotate with the exhaust stream and provide a more efficient mixture of said metered reducing agents and exhaust gases in the exhaust duct.

Said means for creating mixing turbulence may consist of at least one bend of said exhaust duct. Said bend may be substantially straight, i.e. essentially 90 degrees. Said bend may be less than 90 degrees, such as e.g. 45 degrees or 60 degrees. Said bend may be greater than 90 degrees, such as e.g. 120 or 150 degrees. Said means for creating turbulence, comprising at least one bend, has the effect of enabling a more efficient mixture of reducing agents and exhaust gases in said exhaust duct upstream of the SCR catalyst.

According to one embodiment, the arrangement may comprise: - said means for distributing dosed reducing agent; said means for evaporating dosed reducing agent; and - said means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gas, which means comprise at least one fin arranged at an inner wall of the exhaust duct.

This embodiment of the arrangement, which comprises means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases, which have at least one fin, can enable an effective mixing of reducing agent and exhaust gases in said exhaust duct upstream of the SCR catalyst without a bend in the exhaust duct is provided. This is advantageous for some SCR systems where for reasons of space it is not possible to provide a bend in the exhaust duct to create mixing turbulence.

According to one embodiment, the arrangement may comprise: 535 800 - said means for dispensing dosed reducing agent; said means for evaporating dosed reducing agent; and - said means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases, which means comprise a bend of said exhaust duct.

This embodiment of the arrangement, which comprises means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases, where a bend is provided at the exhaust duct, can enable an effective mixing of reducing agent and exhaust gases in said exhaust duct upstream of the SCR catalyst without t. ex. a fin or a propeller blade is provided at the exhaust duct. This provides a design which has a lower weight and which is less complex to design and manufacture. This design is a cost effective design of the arrangement.

According to one embodiment, the arrangement may comprise: - said means for distributing dosed reducing agent; said means for evaporating dosed reducing agent; said means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gas, which means comprise at least one fin arranged at an inner wall of the exhaust duct; and - said means for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases, which means comprise a bend of said exhaust duct.

By providing an arrangement comprising both at least one fin and a bend of said exhaust duct, an optimized mixture of metered reducing agent and exhaust gases is provided in the exhaust duct upstream of the SCR catalyst. According to one embodiment, said means may be configured as an integrated unit. This has the effect of reducing the required space for said means in the exhaust duct. In this case, a more compact SCR system can be achieved, which can be manufactured at a lower cost as a smaller amount of material for the SCR system is required. This provides a less bulky SCR system, which can bring a number of advantages in cases where the SCR system e.g. is mounted in a motor vehicle.

According to an example, said mixing means in the form of at least one fin may be arranged in said mixing means as defined by said bend in the exhaust duct.

Said reducing agent may be a urea-based fluid solution, such as e.g.

AdB | ue. One skilled in the art will appreciate that any reducing agent of the SCR system may be used, and the invention is in no way limited to said exemplary product. According to a preferred example, said urea-based fluid solution is a urea-based liquid solution. An advantage of providing a urea-based liquid solution is that an efficient and accurate dosing of the reducing agent is enabled. With a suitable dosing nozzle of the dosing unit, a spray image of the reducing agent of the desired quality can be obtained.

Said arrangement may preferably be in the form of a separate unit in the exhaust duct of the SCR system. With this modular configuration, a simplified manufacturing procedure for the arrangement can be provided. By providing the arrangement as a separate unit, a more cost-effective manufacturing process can be achieved, compared to a case where retrofitting of said distributors, evaporators and mixers is required. Said arrangement may be detachable from the exhaust duct and / or replaceable thereby. Advantageously, an SCR system is provided where a defective or functionally degraded mixing configuration can be easily replaced by a new and completely correctly functioning arrangement.

The above objects are also achieved with an engine and also with a motor vehicle comprising the arrangement. The motor vehicle can be, for example, a truck, bus or car.

The above objects are also achieved with a method according to claim 12.

Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as through the practice of the invention. While the invention is described below, it should be apparent that the invention is not limited to the specific details described. Those skilled in the art having access to the teachings herein will recognize additional applications, modifications, and incorporations in other areas, which are within the scope of the invention. SUMMARY DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following detailed description which is to be read in conjunction with the accompanying drawings where like reference numerals refer to like parts in the various figures, and in which: FIG. 1 schematically illustrates a vehicle; Fig. 2 schematically illustrates a subsystem of the vehicle shown in Fig. 1, according to an aspect of the present invention; Figs. 3a-e schematically illustrate different subsystems of an SCR system; Fig. 4a schematically illustrates a fate diagram of a method, according to an aspect of the present invention; and Fig. 4b schematically illustrates in further detail a fate diagram of a method, according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE FIGURES Referring to Fig. 1, there is shown a side view of a vehicle 100, consisting of a tractor 110 and a trailer 112. The vehicle may be a heavy vehicle, such as a truck or a bus. The vehicle can alternatively be a car. The vehicle comprises a schematically shown internal combustion engine 111 intended for its operation.

It should be noted that the invention is suitable for application in any SCR system and is not sold limited to SCR systems of motor vehicles. The innovative procedure and the innovative arrangement are also well suited for other platforms that include an SCR system, such as watercraft of any kind, e.g. motorboats, ships, ferries or ships.

The innovative procedure and the innovative arrangement are also well suited for systems including industrial engines e.g. electric power plants (diesel generators).

The innovative procedure and the innovative arrangement are thus well suited for an arbitrary system that includes a NOx generator such as an engine and an SCR system.

According to one aspect of the invention, means are provided which are primarily arranged for dispensing dosed reducing agent. By the term distribution is meant herein a distribution, i.e. decomposition of a number of liquids into smaller amounts of liquids. The term distribution thus refers to the division of at least one volume of reducing agent into a number of smaller volumes of reducing agent. Typically, drops of dosed reducing agent can be broken up into smaller units of said dispersant. 535 800 12 Here, the term "link" refers to a communication link which may be a physical line, such as an optoelectronic communication line, or a non-physical line, such as a wireless connection, for example a radio or microwave link.

Here, the term "conduit" refers to a passageway for holding and transporting a fluid, such as e.g. a reductant in liquid form. The conduit may be a pipe or hose of any suitable material, such as e.g. plastic, rubber or metal.

Herein, the tin "reductant" or "reducing agent" refers to an agent used to react with certain emissions in an SCR system. These emissions can e.g. be NOx gas. The terms "reductant" and "reducing agent" are used synonymously herein. Said reductant is according to an embodiment so-called AdBlue. Of course, other types of reductants can be used.

Here, AdBIue is mentioned as an example of a reductant, but a person skilled in the art realizes that the innovative method and the innovative device can be realized for other types of reductants, with necessary adaptations, such as e.g. adjustments to the adequate freezing point for selected reductants, in control algorithms for executing software code in accordance with the innovative procedure.

Referring to Fig. 2, a subsystem 299 of the vehicle 100 is shown.

The subsystem 299 is arranged in the tractor 110. The subsystem 299 may form part of an SCR system. According to this example, the subsystem 299 consists of a container 205 which is arranged to hold a suitable amount of reductant and is further arranged to be refillable if necessary. The container can hold e.g. 75 or 50 liters of reductant.

A first conduit 271 is provided to direct the reductant to a pump 230 from the container 205. The pump 230 may be any suitable pump such as a diaphragm pump comprising at least one filter. The pump 230 is arranged to be driven by means of an electric motor. The pump is 230 arranged to pump up the reductant from the container 205 via the first line 271 and via a second line 272 supply said reductant to a dosing unit 250.

The dosing unit 250 comprises an electrically controlled dosing valve, by means of which a fate of the reductant added to the exhaust system can be controlled. The pump 230 is arranged to pressurize the reductant in the second line 272.

The dosing unit 250 is provided with a throttling unit, against which said pressure of the reductant is built up in the subsystem 299. This pressure is referred to herein as the working pressure of the subsystem 299.

The dosing unit 250 is arranged to supply said reductant to an exhaust system (see Figs. 3a-e below) of the vehicle 100. More specifically, the dosing unit 250 is arranged to supply in a controlled manner an appropriate amount of reductant to an exhaust system of the vehicle 100. An SCR catalyst (not shown) is arranged downstream of a position of the exhaust system where supply of the reductant is effected. The amount of reductant supplied to the exhaust system is intended to be mixed with exhaust gases therein and fed to the SCR catalyst downstream of the metering unit 250.

The dosing unit 250 is arranged at e.g. an exhaust pipe (see Figs. 3a-e) arranged to direct exhaust gases from an internal combustion engine 111 of the vehicle 100 to the SCR catalyst and then out to an ambient external SCR system. It should be noted that the exhaust system heats up during operation of the internal combustion engine. The heated exhaust system can in various ways contribute to evaporating the dosed reducing agent. but it can also contribute to the urea in the reducing agent being crystallized under unfavorable operating conditions, whereby accumulation of reducing agent can take place in the exhaust system.

A third conduit 273 is provided between the metering unit 250 and the container 205. The third conduit 273 is arranged to return a certain amount of the reductant fed to the metering valve 250 to the container 205. In this way the metering unit 250 is cooled by means of a fl 535 800 14 of the reductant as this is pumped through the metering unit 250 from the pump 230 to the container 205.

A first coolant line 281 is provided to hold and transport coolant for an engine of the vehicle 100. The first coolant line 281 is partially disposed in the container 205 to heat the reductant present therein in cases where the reductant is cooled. According to this example, the first coolant line 281 is arranged to direct coolant heated by the vehicle's engine in a closed circuit through the container 205, via the pump 230 and a second coolant line 282 back to the engine of the vehicle 100.

According to one embodiment, the first coolant line 281 is configured with a substantially U-shaped portion present in the container 205, as schematically shown in Fig. 2. With this configuration, an improved heating of the reductant in the container 205 is provided when the reductant has too low a temperature to work as desired. It should be noted that the first coolant line 281 may have any suitable configuration. In case the reductant has a temperature which exceeds a predetermined value, heating of the reductant by means of the coolant can be deactivated automatically.

A control unit 200 is arranged for communication with a temperature sensor 220 via a link 293. The temperature sensor 220 is arranged to detect a prevailing temperature of the reductant where the sensor is mounted. According to this embodiment, the temperature sensor 220 is arranged at the container 205.

The temperature sensor 220 is arranged to continuously send signals to the first control unit 200 including information about a prevailing temperature of the reductant.

The control unit 200 is arranged for communication with the pump 230 via a link 292 for controlling operation of the pump 230 by regulating flows of the reductant within the subsystem 299. The control unit 200 is arranged to control an operating power of the pump 230 by controlling the electric motor. The control unit 200 is arranged for communication with the dosing unit 250 via a link 291 for controlling operation of the dosing unit 250 for controlling the supply of the reductant to the exhaust system. The control unit 200 is arranged to control the operation of the dosing unit 250 to control the return of the reductant to the container 205.

Fig. 3a schematically illustrates a subsystem of an SCR system, according to an aspect of the invention. Fig. 3a shows the dosing unit 250 arranged at an exhaust pipe 390 between the internal combustion engine 111 and an SCR catalyst.

The dosing unit 250 is equipped with a nozzle 351 which is arranged to inject reducing agent into the exhaust pipe 390 upstream of the SCR catalyst.

In the exhaust pipe, means 310 for distributing reducing agents are arranged.

According to one embodiment, said means 310 for distributing reducing means comprise at least one wire in the form of a ball-like configuration. The wire can be made of any suitable material, such as e.g. a metal or metal alloy, e.g. aluminum and a steel alloy, respectively.

Said means 310 may be of any suitable configuration. According to this example, said means 310 are configured as a disc including said metal wire, which disc has substantially the same outer diameter as the inner diameter of the exhaust pipe. The disc can be of suitable thickness d1. According to this example, the thickness d1 is 5 centimeters. The thickness dt can be in a range of 1 centimeter and 10 centimeters. According to an alternative embodiment, the means 310 cover only a part of a cross-sectional area of the exhaust pipe 390.

Said means 310 are arranged to effectively break up a spray image of metered reducing agent caused by the nozzle 351. This is done by reducing means in surface form hitting at least one wire in the means 310, whereby the liquid is atomized in a mechanical manner. Said agents 310 are arranged to atomize substantially the entire amount of dosed reducing agent.

According to one embodiment, said means 310 comprises a screen having a net of suitable mesh size. In this case, said means 310 can be described as a network.

The net may be made of suitable material, e.g. a metal or metal alloy.

It should be noted that the means 310 are primarily arranged to mechanically dispense the metered amount of reductant. However, the means 310 cause a certain, smaller part of the supplied amount of reductant to evaporate in, or immediately downstream, the means 310. This is an undesirable and rather unavoidable effect. It is also the case that a certain turbulence of the exhaust fate is caused by the means 310. This is also an undesirable and rather inevitable effect. Hence the formulation that the agents 310 are primarily arranged to dispense at least a portion of the metered amount of reductant.

Fig. 3b schematically illustrates a subsystem of an SCR system, according to an aspect of the invention. F ig. Fig. 3b shows a dosing unit 250 which is identical to that described with reference to Fig. 3a. In the exhaust pipe, means 320 for evaporation of reducing agent are arranged.

According to one embodiment, said means 320 for evaporating reducing agent comprises at least one plate. The plate can be made of any suitable material, e.g. a metal or metal alloy, e.g. aluminum and a steel alloy, respectively. By providing it with at least one plate, a surface for temporary accumulation of reducing agent can act for an efficient evaporation of said reducing agent. The plate is arranged to transfer thermal energy to the supplied amount of reducing agent, whereby evaporation thereof is effected. According to one embodiment, said means 320 comprises a number of plates arranged in a suitable manner to provide a larger surface for temporary accumulation of reducing agent and thereby act for an efficient evaporation of said reducing agent. According to one embodiment, at least one sheet is folded with a number of folds. In this way, an even larger surface area to enable efficient evaporation of said reducing agent can be provided.

Said means 320 may be of any suitable configuration. Said means may be of any suitable size. According to this example, said means 320 is configured as a box 320 comprising a number of stacked and separated pleated plates. The box 320 is open at a front end and a rear end with respect to a flow direction of the exhaust gases and said dosed reducing agent. In this way, atomized reducing agent can flow into the box and be heated by at least one plate so that a phase change from liquid phase to vapor phase of the reducing agent can take place.

According to this example, the box is 320 10x5x5 centimeters, where the longer dimension runs in the longitudinal direction of the exhaust pipe.

According to another embodiment, said means 320 comprises two coaxially arranged tubes of suitable lengths, an interior of the two tubes being arranged to receive a part of said dosed reducing means in order to enable evaporation thereof. A space between an outer pipe and the inner pipe is arranged to conduct an exhaust gas stream in order to heat the inner pipe in order to enable efficient evaporation of the reducing agent therein.

According to one embodiment, said means 320 may be arranged to handle the entire metered amount of reducing agent. According to another embodiment, said means 320 may be arranged to handle a portion of the metered amount of reducing agent, as is apparent from the example illustrated in Fig. 3b.

Said means 320 are arranged to efficiently vaporize metered reducing agent in the exhaust pipe 390. This is done by supplying thermal energy in liquid form to the evaporating means 320 and thereby evaporating.

Said means 320 are arranged to vaporize at least a part of the amount of dosing reducing agent. In one embodiment, 50-70% of the metered amount of reducing agent may be vaporized by the means 320. In another embodiment, 50-90% of the metered amount of reducing agent may be vaporized by the means 320. In one embodiment, substantially all of the metered amount of reducing agent may be vaporized by the means. 320. It is desirable to vaporize as large a portion of the metered amount of reducing agent as possible to provide an effective mixture of reducing agent and exhaust gases in the exhaust pipe 390 upstream of the SCR catalyst.

It should be noted that the means 320 are primarily arranged to vaporize the metered amount of reductant. However, the means 320 cause a certain, smaller portion of the added amount to be reductantly distributed. This is an undesirable, and rather unavoidable, effect. It is also the case that a certain turbulence of the exhaust fate is caused by the means 320. This too is an undesirable, and rather inevitable effect. Hence the formulation that the agents 320 are primarily arranged to vaporize at least a portion of the metered amount of reductant.

Fig. 3c schematically illustrates a subsystem of an SCR system, according to an aspect of the invention. Fig. 3c shows a dosing unit 250 which is identical to that described with reference to Figs. 3a and 3b above. According to this example, the nozzle 351 is arranged in a bend of the exhaust pipe, which has the advantage that the exhaust gas flow can be rather turbulent. In this way, an effective mixture of metered reducing agent and the exhaust gases in the exhaust pipe 390 is provided. It should be noted that the nozzle 351 may be mounted in a bend in all of the embodiments described herein. In the exhaust pipe there are means 330 for creating mixing turbulence arranged. According to one embodiment, said means 330 for creating mixing turbulence comprises at least one fin 330. The fin 330 may be made of any suitable material, e.g. a metal or metal alloy, e.g. aluminum and a steel alloy, respectively. By providing the at least one fin, an efficient mixture of said vaporized reducing agents and exhaust gases in the exhaust duct can be achieved.

According to one embodiment, said means 330 comprises a plurality of fins arranged in a suitable manner for efficient mixing of said reducing agent and said exhaust gases.

Said means 330 may be of any suitable configuration and of any suitable size. According to this example, said means 330 is configured as a fin 330. Said means 330 may alternatively be configured as a blade or a three-dimensional body, such as a cone or a block. Alternatively, at least one rotatably mounted turbine blade may be provided to provide efficient mixing of reducing agents and exhaust gases.

According to this example, the fin is flat. with a base of 10 centimeters and a height of 10 centimeters.

Said means 330 are arranged to effectively mix metered reducing agent and exhaust gases in the exhaust pipe 390.

It should be noted that the means 330 are primarily arranged to create mixing turbulence in the exhaust pipe 390. However, the means 330 cause a certain, smaller part of the supplied amount of reductant to be distributed. This is an undesirable and rather unavoidable effect. It is also the case that a certain evaporation of the reducing agent is caused by the agents 330. This is also an undesirable and rather unavoidable effect. Hence the wording that the means 330 are primarily arranged to create mixing turbulence in the exhaust system 390. 535 800 Fig. 3d illustrates schematically subsystem of an SCR system, according to one aspect of the invention. Fig. 3d shows a dosing unit 250 which is identical to that described with reference to Figs. 3a-c above. In the subsystem, means 340 for creating mixing turbulence are arranged.

According to one embodiment, said means 340 for creating mixing turbulence comprises at least one bend 340. By providing the at least one bend 340, an effective mixture of said vaporized reducing agents and exhaust gases in the exhaust duct can be achieved.

According to one embodiment, said means 340 comprises a plurality of bends arranged in a suitable manner for efficient mixing of said reducing agent and said exhaust gases.

Said means 340 may be of any suitable configuration. Said curves can be of any degree, such as e.g. essentially 90 degrees. Alternatively, the bend may be greater or less than 90 degrees. According to this example, said means 340 are configured as a 90 degree bend.

Said means 340 are arranged to effectively mix metered reducing agent and exhaust gases in the exhaust pipe 390.

It should be noted that the means 340 are primarily arranged to create mixing turbulence in the exhaust pipe 390. However, the means 340 cause a certain evaporation of the reducing agent. This, too, is an undesirable, and rather inevitable, effect. Hence the formulation that the means 340 are primarily arranged to create mixing turbulence in the exhaust system 390.

Fig. 3e schematically illustrates an arrangement according to an aspect of the invention, in which a combination of the means described with reference to Figs. 3a-d above. Fig. 3e shows that the means 310 for distribution are arranged downstream of the nozzle 351 at a suitable distance. Furthermore, the means 320 for evaporation are arranged downstream of the means 310 for distribution at a suitable distance.

The turbulence generating means 330 are arranged downstream of the evaporation means 320 at a suitable distance, and the turbulence generating means 340 are arranged downstream of the means 330 at a suitable distance. An SCR catalyst (not shown) is provided downstream of the means 340.

According to the invention, there is provided an arrangement comprising the means 310, the means 320, the means 330 and the means 340.

It should be noted that it is advantageous for the means 310 to be arranged upstream of the means 320 and the means 330 and the means 340. It is also advantageous for the means 320 to be arranged upstream of the means 330 and the means 340. However, the means 330 and the means 340 may be arranged in any order relative to a flow direction of the exhaust stream, or as an integrated mixing configuration.

Fig. 4a schematically illustrates a flow chart of a process for, in an arrangement, efficiently mixing reducing agents and exhaust gases for an SCR system, said SCR system comprising a dosing unit for dosing said reducing agent into an exhaust duct upstream of a catalyst unit, according to an embodiment of the invention. The method comprises a first method step s401. Step s401 includes the steps of, upstream of said catalyst unit, in said exhaust duct: - distributing metered reducing agent by means primarily arranged therefor; vaporize dosed reducing agent by means primarily provided therefor; and - creating mixing turbulence of a mixture of metered reducing agent and said exhaust gases by means primarily provided therefor. After step s401, the process is terminated. Fig. 4b schematically illustrates a flow chart of a method for, in an arrangement, effectively mixing reducing agents and exhaust gases for an SCR system, said SCR system comprising a dosing unit for dosing said reducing agent into an exhaust duct upstream of a. catalyst unit, according to an embodiment of the invention.

The method includes a first method step s410. Method step s410 includes the step of dosing reducing agent into the exhaust pipe 390 by means of the dosing unit 250 according to drivers stored in the control unit 200. Said dosing of reducing agent may take place intermittently or substantially continuously. After the process step s410, a subsequent process step s420 is performed.

The process step s420 comprises the step of distributing said dosed reducing agent by means of distribution means 310. According to the invention, said dosed amount of reducing agent is mechanically distributed. In this case, droplets in said dosed amount of reducing agent can be broken up into a number of smaller parts, which smaller parts can be more easily evaporated and / or mixed with exhaust gases in the exhaust duct before supply to the SCR catalyst. After the process step s420, a subsequent process step s430 is performed.

The process step s430 includes the step of vaporizing said metered reducing agent by means of evaporating agent 320. In this case, a large part of the supplied reducing agent which is in liquid phase in the form of droplets or divided droplets (performed in step s420 above) may pass into the second phase. The phase change can be performed by transferring thermal energy stored in evaporator 230 to reducing agent before or on the evaporator 230. After the process step s430, a subsequent process step s440 is performed. The method step s440 comprises the step of creating mixing turbulence by means of mixing means 330 comprising at least one fin, and / or at least one three-dimensional object, e.g. a cone, and / or rotatably mounted propeller blade. The propeller blade can also be non-rotatably attached to the exhaust system. This provides an improved mixture of supplied (distributed and evaporated) reducing agents and exhaust gases in the exhaust duct of the SCR system. After the process step s440, a subsequent process step s450 is performed.

Process step s450 includes the step of creating additional mixing turbulence by mixing means 340 comprising at least one bend of the exhaust duct. Hereby an improved mixture of supplied (distributed, evaporated and according to step s440 mixed) reducing agent and exhaust gases is provided in the exhaust duct of the SCR system. After the procedure step s450, the procedure is terminated.

According to one aspect of the invention, there is provided a method of an arrangement comprising at least two of the method steps s420, s430, s440 and s450.

The foregoing description of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing the invention. It is not intended to be exhaustive or to limit the invention to the variations described. Obviously, many modifications and variations will occur to those skilled in the art. The embodiments were selected and described in order to best explain the principles of the invention and its practical applications, thereby enabling those skilled in the art to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims (17)

10 15 20 25 30 535 800 24 PATENT REQUIREMENTS An arrangement for efficient mixing of reducing agents and exhaust gases for an SCR system (299), comprising a dosing unit (250) with a nozzle (351) for dosing said reducing agent into an exhaust duct (390) upstream of a catalyst unit characterized in that in the exhaust duct (390) has at least: - means (310) primarily arranged for mechanical distribution and for breaking up the spray image of reducing agent metered from the nozzle (351); - means (320) primarily arranged for evaporation of dosed reducing agent; and - means (330; 340) primarily arranged for creating mixing turbulence of a mixture of metered reducing agent and said exhaust gas, and said means (310; 320; 330; 340) being arranged at suitable distances from each other arranged upstream of said catalyst unit. The arrangement of claim 1, wherein said means (310) for mechanical distribution comprises at least one metal wire. The arrangement of claim 2 wherein said means (310) for mechanical distribution is configured as a disk including said metal wire. An arrangement according to claim 3, wherein said disc has substantially the same outer diameter as the inner diameter of the exhaust pipe. An arrangement according to any one of claims 1 to 4, wherein said means (320) for evaporation comprises at least one sheet in the form of a sheet. An arrangement according to any one of claims 1-5, wherein said means (330) for creating turbulence comprises at least one fin (330) arranged at an inner wall of the exhaust duct (390). 10 15 20 25 30 535 800 25 An arrangement according to any one of claims 1-5, wherein said means (340) for creating turbulence consists of a bend (340) of said exhaust duct (390). An arrangement according to claims 6 and 7, wherein said means (330) for creating mixing turbulence comprises both a fin (330) arranged at an inner wall of the exhaust duct (390) and a bend (340) of said exhaust duct (390). ). An arrangement according to any one of the preceding claims, wherein said reducing agent is a urea-based fluid solution. An arrangement according to any one of the preceding claims, wherein said arrangement is preferably in the form of a separate unit in the exhaust duct (390). An arrangement according to any one of the preceding claims, wherein said arrangement is detachable from the exhaust duct (390) and / or replaceable therewith. A method of providing efficient mixing of reducing agents and exhaust gases for an SCR system (299), said SCR system (299) comprising a metering unit (250) with a nozzle (351) for metering said reducing agent into an exhaust duct (390) upstream of a catalyst unit, characterized by the steps of, upstream of said catalyst unit, in said exhaust duct: - mechanically atomizing (s420) and breaking up the spray image of reducing agent dosed from the nozzle (351) by means (310) primarily arranged therefor; vaporize (s430) dosed reducing agent by means (320) primarily provided therefor; and - creating (s440; s450) mixing turbulence of a mixture of metered reducing agent and said exhaust gases by means (330; 340) primarily arranged therefor, said means (310; 320; 330; 340) being arranged at suitable distances from each other arranged upstream of said catalyst unit. A method according to claim 12, wherein the step (s420) of mechanically atomizing and breaking up the spray image of reducing agent dosed from the nozzle (351) takes place by means of at least one metal wire arranged therefor. A method according to claim 12, wherein the steps of evaporating (s430) dosed reducing agent take place by means of a plate in the form of a sheet arranged therefor. The method of claim 12, wherein the steps of creating (S450) mixing turbulence of a mixture of metered reducing agent and said exhaust gases are by means of a bend (340) of said exhaust duct (390) and / or at least one fin (330) which is arranged at an inner wall of the exhaust duct (390). A method according to any one of claims 12-15, wherein said reducing agent is a urea-based id solution. An engine (111) comprising an arrangement according to any one of claims 1-11.