Method for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system

A method for reducing deposits related to a reduction agent (RA) in a portion of an exhaust aftertreatment system (EAS) of an internal combustion engine (ICE) and comprising an injector for injecting the RA into said EAS, said portion located downstream of said injector, as seen in an intended direction of flow of exhaust gas in said EAS, said method comprising:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Application No. EP 21171411.8 filed on Apr. 30, 2021, the disclosure and content of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a method for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine, a control unit adapted to perform the method, an exhaust aftertreatment system comprising the control unit and a vehicle comprising the control unit and/or the exhaust aftertreatment system.

The invention can be applied in all kinds of applications using an internal combustion engine, such as trucks, buses, marine vessels, industrial construction machines, construction equipment, and passenger cars. Although the invention will be described with respect to a truck, the invention is not restricted to a method for use in this particular vehicle but may also be used in other applications, e.g., in vehicles such as buses, passenger cars, marine vessels, industrial construction machines, and construction equipment. Examples of the latter may be wheel loaders, excavators, backhoe loaders, or articulated haulers. The invention is further applicable for any internal combustion engine with an exhaust aftertreatment system, for instance stationary internal combustion engines. The term “stationary internal combustion engine” as used herein relates to any application in which the internal combustion engine is not primarily used for propulsion, but for power generation. Examples of such applications may be power generation engines, genset engines, back-up power supply engines, industrial engines, or engines used in stationary machinery, such as rock crushers.

BACKGROUND

Due to environmental concerns and legal demands, in applications using an internal combustion engine, it is desired to lower the fuel consumption and to reduce emissions such as carbon dioxide (CO2) and nitrogen oxides (NOx). To maximize fuel efficiency and minimize CO2emissions, combustion is generally calibrated to high engine-out NOxemissions. The NOxemissions are reduced in an exhaust aftertreatment system, so that the overall emissions from the internal combustion engine and the exhaust aftertreatment system meet the demands One common way of reducing NOxincludes a step of injecting a reduction agent, such as an aqueous urea solution, into the exhaust aftertreatment system. The reduction agent operates with a component of the exhaust aftertreatment system, e.g., a selective catalytic reduction catalyst, to reduce the amount of NOx.

Under ideal conditions, the urea is decomposed in the exhaust gas stream to ammonia, NH3. However, the decomposition of urea is largely affected by the temperature in the exhaust aftertreatment system, in particular the temperature in the portion of the exhaust aftertreatment system where the reduction agent is injected, and during some operating conditions the reduction agent is not fully decomposed. This may lead to accumulation of reduction agent related by-products in the liquid phase or solid phase on the inner walls of the exhaust aftertreatment system. The liquid phase may consist of e.g. molten reduction agent and biuret, while solid deposits may consist of e.g. cyanuric acid and ammelide. If excessive solid deposits related to the reduction agent are accumulated in the exhaust aftertreatment system, the performance of the exhaust aftertreatment system is deteriorated, which may lead to too high NOxemissions, increased reduction agent consumption and poor fuel economy. In the present context, the term deposits is used to denote reduction agent related by-products in both the liquid phase and solid phase.

SUMMARY

In view of the above, an object of the present invention is to provide a method for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine, by which method the deposits related to a reduction agent can be reduced in an appropriate manner.

According to a first aspect of the invention, the object is achieved by a method for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine according to claim1. The exhaust aftertreatment system comprises an injector for injecting the reduction agent into the exhaust aftertreatment system, and the portion of the exhaust aftertreatment system is located downstream of the injector, as seen in an intended direction of flow of exhaust gas in the exhaust aftertreatment system. The method comprises the steps of:identifying a future operating sequence for the internal combustion engine. The future operating sequence comprises a first temporal portion and a second temporal portion, the second temporal portion being subsequent to the first temporal portion.performing a confirmation procedure comprising:confirming that the future operating sequence is suitable for reducing the deposits andconfirming that the internal combustion engine operates in accordance with the precedingly identified future operating sequence.in response to the confirmation procedure being affirmative, executing a deposit removal dosage procedure. The deposit removal dosage procedure comprises controlling the injector such that a first dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the first temporal portion and that a second dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the second temporal portion, the second dosage being smaller than the first dosage.

By executing the deposit removal dosage procedure in response to having identified a future operating sequence for the internal combustion engine and having confirmed that it is suitable for reducing the deposits, any deposits related to the reduction agent can be reduced in an appropriate manner By way of example, the build-up of deposits related to a reduction agent in the portion of the exhaust aftertreatment system can be reduced, possibly even avoided, without negatively affecting the fuel efficiency of the internal combustion engine. As a further example, when the internal combustion is used in a vehicle, deposits related to a reduction agent may be reduced without negatively affecting the driveability of the vehicle. As yet a further example, the uptime of the internal combustion engine may be improved, as the need for regeneration events during engine idle may be reduced.

Optionally, a ratio between the second dosage and a maximum dosage that can be injected by the injector is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

Optionally, a ratio between the second dosage and the first dosage is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

A low dosage of reduction agent injected by the injector provides a lesser cooling effect in the portion of the exhaust aftertreatment system located downstream of the injector than a high dosage. Thus, as the second dosage is low, more specifically significantly lower than the maximum dosage of the injector and/or than the first dosage, the temperature in the portion of the exhaust aftertreatment system can be kept high or be allowed to increase in response to the operating sequence of the internal combustion engine. Such temperature will allow for more efficient removal of deposits, which may incorporate reduction agent related by-products in both the liquid phase and solid phase. In addition, by injecting the second, low, dosage during at least a part of the second temporal portion, the risk of deposits building up in the portion of the exhaust aftertreatment system is reduced. The term “dosage” as used herein refers to amount of reduction agent per time unit. The dosage may be controlled by, e.g., adjusting the number of injections per time unit, or adjusting the duration of each injection.

Optionally, the first dosage of the reduction agent is such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst located downstream the portion of the exhaust aftertreatment system is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

By adapting the first dosage of the reduction agent so that the ratio between the actual reductant buffer and the maximum reductant buffer will be kept within a desired range, at each current operating condition throughout the precedingly identified future operating sequence, the efficiency of the selective catalytic reduction catalyst can be maintained during at least the first and the second temporal portion. This implies that, at each current operating condition, the reductant buffer in the catalyst is sufficient to ensure satisfactory emission performance, while saturation of the reductant buffer in the catalyst, which may lead to unwanted emission species, e.g. ammonia, passing through the selective catalytic reduction catalyst, is prevented.

Optionally, the future operating sequence is determined to be suitable for reducing the deposits if a ratio between an estimated workload of the internal combustion engine in the first temporal portion and the estimated workload in the second temporal portion is at least 1.5, preferably at least 2.

Optionally, a ratio between the estimated workload in the second temporal portion and the maximum workload of the internal combustion engine is less than 0.5.

By executing the deposit removal dosage procedure at an identified future operating sequence in which the estimated workload in the first temporal portion is significantly higher than the estimated workload in the second temporal portion and, purely by way of example, in which the estimated workload in the second temporal portion is significantly lower than the maximum workload of the internal combustion engine, the removal of deposits is achieved in an appropriate manner By way of example, the removal of deposits may be achieved without negatively affecting the fuel efficiency of the internal combustion engine. By identifying a period of high workload followed by a period of low workload and by controlling the injection of reduction agent to be significantly lower during at least a part of the period of low workload, the temperature in the exhaust aftertreatment system is allowed to increase to a temperature at which any deposits in the portion of the exhaust aftertreatment system can be efficiently removed. The low workload at the second temporal portion implies that the second dosage may be low while nevertheless ensuring sufficient remaining buffer level in the selective catalytic reduction catalyst so that the emissions from the exhaust aftertreatment system are maintained at a satisfactory level.

Optionally, the method further comprises a step of identifying a deposits parameter indicative of a level of deposits in the portion of the exhaust aftertreatment system and the confirmation procedure further comprises:confirming that the level of deposits is equal to or exceeds a predeterminable threshold.

By identifying if the level of deposits is equal to or exceeds a predeterminable threshold, the deposit removal dosage procedure can be controlled to be executed only when there is a need for removal of deposits. The deposits parameter may be indicative of a level of liquid and/or solid deposits.

Optionally, the method further comprises identifying a temperature parameter indicative of a temperature of the portion of the exhaust aftertreatment system. The deposit removal dosage procedure is performed in dependence on the temperature parameter, preferably the initiation of the second dosage is dependent on the temperature parameter.

Optionally, the second dosage is initiated in response to detecting that the temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold.

Optionally, the temperature of the portion of the exhaust aftertreatment system is a temperature of a wall portion of the portion of the exhaust aftertreatment system.

By identifying a temperature parameter indicative of a temperature of the portion of the exhaust aftertreatment system, which may, purely by way of example, be a temperature of a wall portion of the portion of the exhaust aftertreatment system, and performing the deposit removal dosage procedure in dependence on the temperature parameter, the efficiency of the deposit removal can be ensured. Purely by way of example, the second dosage can be initiated when the temperature of the portion of the exhaust aftertreatment system is at or near a peak value of the precedingly identified future operating sequence. As discussed above, the temperature in the portion of the exhaust aftertreatment system can thus be kept high or be allowed to increase, allowing for more efficient removal of deposits. The efficiency of the decomposition of reduction agent and/or the removal of liquid or solid deposits related to the reduction agent are largely correlated to the wall temperature of the portion of the exhaust aftertreatment system where dosing of the reduction agent takes place.

Optionally, the future operating sequence further comprises a third temporal portion, the third temporal portion being subsequent the second temporal portion, and the deposit removal dosage procedure further comprises controlling the injector such that a third dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the third temporal portion. The third dosage is such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst located downstream the portion of the exhaust aftertreatment system is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

At the second temporal portion, during at least a portion of which the second, lower, dosage is injected, the reductant buffer in the selective catalytic reduction catalyst is likely to decrease towards the lower end of a range in which efficiency of the selective catalytic reduction catalyst can be maintained. By controlling the injector to inject the third dosage during at least a part of the third temporal portion, the reductant buffer in the selective catalytic reduction catalyst can be restored to a desired range after having decreased at the second temporal portion.

Optionally, the internal combustion engine propels a vehicle, and the feature of identifying the future operating sequence and/or of confirming that the future operating sequence is suitable for reducing the deposits comprises confirming that the vehicle is predicted to be driven in at least one of the following driving conditions:uphill driving during at least a majority of said first temporal portion and level or downhill driving during at least a majority of said second temporal portion,acceleration during at least a majority of said first temporal portion and driving at constant speed or deceleration during at least a majority of said second temporal portion,entering a motorway during said first temporal portion and driving on said motorway during said second temporal portion,overtaking another vehicle during said first temporal portion and driving at constant speed or deceleration during said second temporal portion.

Each one of these driving conditions is likely to correspond to an operating sequence having a first temporal portion at which the workload of the internal combustion engine is high and a second temporal portion at which the workload of the internal combustion engine is low, thus being suitable performing the deposit removal dosage procedure. The above-described driving conditions are related to a vehicle, but it should be noted that also non-vehicle applications may show such a suitable future operating sequence.

Optionally, the vehicle comprises a route planning system, preferably comprising a GPS and/or a map database, and the feature of confirming that the vehicle is predicted to be driven in at least one of the driving conditions comprises using the route planning system.

The route planning system may facilitate the identification of the future operating sequence.

Optionally, the reduction agent is a reduction agent for NOxemissions, preferably an aqueous urea solution.

A NOxreduction agent generally cooperates with a catalyst and generally requires relatively high temperatures to be fully decomposed, thus making it suitable for the method of the invention.

A second aspect of the invention relates to a control unit according to claim13. As such, the control unit is adapted for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine, the exhaust aftertreatment system comprising an injector for injecting the reduction agent into the exhaust aftertreatment system, and the portion of the exhaust aftertreatment system being located downstream of the injector, as seen in an intended direction of flow of exhaust gas in the exhaust aftertreatment system, the control unit being adapted to:identify a future operating sequence for the internal combustion engine, the future operating sequence comprising a first temporal portion and a second temporal portion, the second temporal portion being subsequent to the first temporal portion,perform a confirmation procedure comprising:confirming that the future operating sequence is suitable for reducing the deposits andconfirming that the internal combustion engine operates in accordance with the precedingly identified future operating sequence,in response to the confirmation procedure being affirmative, execute a deposit removal dosage procedure comprising controlling the injector such that a first dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the first temporal portion and that a second dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the second temporal portion, the second dosage being smaller than the first dosage.

Effects and features of the second aspect of the invention are largely analogous to those described above in connection with the first aspect.

Optionally, a ratio between the second dosage and a maximum dosage that can be injected by the injector is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

Optionally, a ratio between the second dosage and the first dosage is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

Optionally, the control unit is adapted to adjust the first dosage of reduction agent such that a ratio between an actual reductant buffer in a selective catalytic reduction catalyst located downstream the portion of the exhaust aftertreatment system and a maximum reductant buffer in the selective catalytic reduction catalyst at a current operating temperature in the selective catalytic reduction catalyst is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

Optionally, the future operating sequence is determined to be suitable for reducing the deposits if a ratio between an estimated workload of the internal combustion engine in the first temporal portion and the estimated workload in the second temporal portion is at least 1.5, preferably at least 2.

Optionally, a ratio between the estimated workload in the second temporal portion and the maximum workload of the internal combustion engine is less than 0.5.

Optionally, the control unit further is adapted to identify a deposits parameter indicative of a level of deposits in the portion of the exhaust aftertreatment system and wherein the confirmation procedure further comprises:confirming that the level of deposits is equal to or exceeds a predeterminable threshold.

Optionally, the control unit further is adapted to identify a temperature parameter indicative of a temperature of the portion of the exhaust aftertreatment system and wherein the control unit is adapted to perform the deposit removal dosage procedure in dependence on the temperature parameter, preferably the control unit is adapted to initiate the second dosage in dependence on the temperature parameter.

Optionally, the control unit is adapted to initiate the second dosage in response to detecting that the temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold.

Optionally, the temperature of the portion of the exhaust aftertreatment system is a temperature of a wall portion of the portion of the exhaust aftertreatment system.

Optionally, the future operating sequence further comprises a third temporal portion, the third temporal portion being subsequent the second temporal portion, and wherein the deposit removal dosage procedure further comprises controlling the injector such that a third dosage of reduction agent is injected into the exhaust aftertreatment system during at least a part of the third temporal portion, the control unit being adapted to adjust the third dosage such a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst located downstream the portion of the exhaust aftertreatment system is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

Optionally, the internal combustion engine propels a vehicle and the feature of identifying the future operating sequence and/or of confirming that the future operating sequence is suitable for reducing the deposits comprises confirming that the vehicle is predicted to be driven in at least one of the following driving conditions:uphill driving during at least a majority of said first temporal portion and level or downhill driving during at least a majority of said second temporal portion,acceleration during at least a majority of said first temporal portion and driving at constant speed or deceleration during at least a majority of said second temporal portion,entering a motorway during said first temporal portion and driving on said motorway during said second temporal portion,overtaking another vehicle during said first temporal portion and driving at constant speed or deceleration during said second temporal portion.

Optionally, the vehicle comprises a route planning system, preferably comprising a GPS and/or a map database, and wherein the feature of confirming that the vehicle is predicted to be driven in at least one of the driving conditions comprises using the route planning system, preferably the control unit is adapted to receive information from the route planning system.

Optionally, the reduction agent is a reduction agent for NOx emissions, preferably an aqueous urea solution.

A third aspect of the invention relates to an exhaust aftertreatment system for an internal combustion engine according to claim14. The exhaust aftertreatment system comprises a source of reduction agent, the source being in fluid connection with an injector, the injector being adapted to inject the reduction agent into a portion of the exhaust aftertreatment system, the portion of the exhaust aftertreatment system being located downstream of the injector, as seen in an intended direction of flow of exhaust gas in the exhaust aftertreatment system, the exhaust aftertreatment system comprising a control unit according to the second aspect of the present invention, the control unit being adapted to issue a signal to the injector in order to control a dosage of reduction agent from the injector.

Effects and features of the third aspect of the invention are largely analogous to those described above in connection with the first and second aspects.

A fourth aspect of the invention relates to a vehicle according to claim15. The vehicle comprises a control unit according to the second aspect of the invention and/or an exhaust aftertreatment system according to the third aspect of the invention.

Effects and features of the fourth aspect of the invention are largely analogous to those described above in connection with the first, second and third aspects.

In the present detailed description, embodiments of the present invention are mainly described with reference to a vehicle in the form of a truck100comprising an internal combustion engine102such as the truck illustrated inFIG.1. However, it should be noted that various embodiments of the described invention are equally applicable for a wide range of vehicles and vessels, as well as for stationary applications.

FIG.1shows a simplified side-view of a vehicle, in the form of a truck100, which is equipped with an internal combustion engine102. The internal combustion engine102may be the single prime mover for propelling the truck100, or it may be comprised in a drive system comprising at least two engines and/or motors, such as electric motors. The internal combustion engine102runs on fuel, for instance diesel fuel, which is supplied to the internal combustion engine102by means of a fuel supply system (not shown).

Purely by way of example, the truck100may comprise a route planning system104, which will be presented more in detail below.

The exhaust gas which is emitted as a result of the combustion of fuel in the internal combustion engine102flows into an exhaust aftertreatment system200, where the exhaust gas is purified to at least a certain extent and/or rendered innocuous.

An example embodiment of an exhaust aftertreatment system is schematically shown inFIG.2. As may be gleaned fromFIG.2, the exhaust aftertreatment system comprises an injector202for injecting a reduction agent204into the exhaust aftertreatment system200. Preferably, the injector202injects the reduction agent204upstream an aftertreatment component206. Upstream as used herein refers to upstream as seen in an intended direction of flow208of the exhaust gas in the exhaust aftertreatment system200.

The injector202may be positioned to inject the reduction agent204in a direction substantially perpendicular to the intended direction of flow208of exhaust gas in the exhaust aftertreatment system200, as schematically illustrated inFIG.2. However, the injector202may alternatively be positioned to inject the reduction agent204at an angle to the intended direction of flow208of exhaust gas.

It is also conceivable that the exhaust aftertreatment system may comprise a plurality of injectors. For instance, the exhaust aftertreatment system may comprise a plurality of injectors injecting the reduction agent204upstream the aftertreatment component206and/or the exhaust aftertreatment system may comprise a plurality of aftertreatment components and a plurality of injectors each injecting a reduction agent upstream of a respective aftertreatment component.

Preferably, the reduction agent204may be a reduction agent for NOxemissions, most preferably the reduction agent is an aqueous urea solution.

The reduction agent204comes from a source210of reduction agent204, which source210is in fluid communication with the injector202. Purely by way of example, the source210may be implemented as a tank adapted to contain the reduction agent204. It should be noted that the setup inFIG.2, showing that the source210may be located near the injector202, is purely intended for illustrational purposes and should in no way be construed as limiting for the invention. Any other position of the source210is feasible, as long as it is in fluid communication with the injector202.

The exhaust aftertreatment system further comprises a portion212located downstream of the injector202. Downstream as used herein refers to downstream as seen in the intended direction of flow208of the exhaust gas in the exhaust aftertreatment system200. Purely by way of example, the portion212may be a portion of a pipe designed for optimum spray propagation from the injector202and efficient decomposition of the reduction agent204before reaching the aftertreatment component206. Although the pipe inFIG.2is exemplified as being straight, it is envisaged that the pipe may have other shapes, e.g. bent.

By way of example, the aftertreatment component206, which may be, e.g., a selective catalytic reduction catalyst206, may be located downstream the portion212of the exhaust aftertreatment system200. Purely by way of example, the aftertreatment component206may utilize the reduction agent204when treating the exhaust gases.

Further, the exhaust aftertreatment system comprises a control unit214. Even though the control unit214functionally is comprised in the exhaust aftertreatment system200, it is not necessarily physically comprised therein. Instead, the control unit214may be located anywhere outside of the exhaust aftertreatment system200, such as on the truck100, as long as the control unit214is operationally connected to the exhaust aftertreatment system200.

The control unit214is adapted to issue control signals to one or more components of the exhaust aftertreatment system to thereby reduce deposits related to the reduction agent204in the portion212of the exhaust aftertreatment system of the internal combustion engine (not shown inFIG.2). More specifically, the control unit214is adapted to issue a signal to the injector202to control the dosage of the reduction agent204from the injector202. It should be noted that features of the control unit214as presented hereinbelow are equally applicable to a method for reducing deposits related to the reduction agent204in the portion212of the exhaust aftertreatment system of the internal combustion engine102.

Further, as a non-limiting example, the exhaust aftertreatment system may comprise a temperature sensor216configured to sense a temperature in the portion212of the exhaust aftertreatment system and provide signal input to the control unit214. The temperature may be a temperature of a wall portion of the portion212of the exhaust aftertreatment system200. Preferably, the temperature sensor216may be located at an inlet of the portion212of the exhaust aftertreatment system200. More preferably, the temperature sensor216may be located upstream the injector202. It is conceivable that the exhaust aftertreatment system may comprise a plurality of temperature sensors.

Purely by way of example, the exhaust aftertreatment system may comprise additional sensors, such as a first NOxsensor218, providing a signal input to the control unit214. Additionally, a second NOxsensor220may be positioned downstream the selective catalytic reduction catalyst206, providing signal input to the control unit214.

Further, as a non-limiting example, the exhaust aftertreatment system may comprise further aftertreatment components, such as a diesel particulate filter222, which may be located upstream the portion212of the exhaust aftertreatment system200.

The control unit214is further adapted to identify a future operating sequence300for the internal combustion engine102. Depending on the application of the internal combustion engine102, such an identification may be carried out in a plurality of different ways, such as, e.g., by assessing a future operating scheme for the internal combustion engine102. As may be gleaned fromFIG.3, the future operating sequence comprises a first temporal portion t1and a second temporal portion t2, the second temporal portion t2being subsequent the first temporal portion t1. Optionally, the future operating sequence300may comprise also a third temporal portion t3, subsequent the second temporal portion t2.

Further, the control unit214is adapted to perform a confirmation procedure. The confirmation procedure comprises confirming that the future operating sequence300is suitable for reducing deposits and confirming that the internal combustion engine102operates in accordance with the precedingly identified future operating sequence300.

Purely by way of example, the future operating sequence300may be determined to be suitable for reducing deposits if a ratio between an estimated workload of the internal combustion engine102in the first temporal portion t1and the estimated workload in the second temporal portion t2is at least 1.5, preferably at least 2. By way of example, the estimated workloads may be determined by calculating the average workload for each temporal portion t1, t2. Optionally, for the future operating sequence300to be determined as suitable for reducing deposits, it may also be required that a ratio between the estimated workload in the second temporal portion t2and a maximum workload of the internal combustion engine102is less than 0.5.

According to one embodiment, when the internal combustion engine102is adapted to propel a vehicle such as theFIG.1truck100, the feature of confirming that the future operating sequence300is suitable for reducing deposits may comprise confirming that the truck100is predicted to be driven in at least one of the following driving conditions:uphill driving during at least a majority of the first temporal portion t1and level or downhill driving during at least a majority of the second temporal portion t2,acceleration during at least a majority of said first temporal portion t1and driving at constant speed or deceleration during at least a majority of said second temporal portion t2,entering a motorway during said first temporal portion t1and driving on said motorway during said second temporal portion t2,overtaking another vehicle during said first temporal portion t1and driving at constant speed or deceleration during said second temporal portion t2.

Purely by way of example, the control unit214may be adapted to receive information from the route planning system104. Preferably, the route planning system104may comprise a map database and/or a satellite-based radionavigation system, such as, e.g., GPS or GLONASS. The map database, if provided, may be provided in the truck100, or may be provided externally, such as in a cloud-based service. The feature of confirming that the vehicle is predicted to be driven in at least one of the driving conditions above may comprise using the route planning system104.

For a stationary application, the control unit214may be adapted to receive, e.g., information about a scheduled work cycle for the internal combustion engine102. Purely by way of example, if the internal combustion engine is used in a stationary machinery such as a rock crusher, the control unit214may be adapted to receive information from working machines supplying rocks to the crusher about their estimated arrival times and their load.

The control unit214is further adapted to, in response to the confirmation procedure being affirmative, execute a deposit removal dosage procedure. The deposit removal procedure comprises controlling the injector202, more specifically its dosage of reduction agent204. Thus, the injector202is controlled such that a first dosage d1of reduction agent204is injected into the exhaust aftertreatment system during at least a part of the first temporal portion t1and such that a second dosage d2of reduction agent204is injected into the exhaust aftertreatment system during at least a part of the second temporal portion t2, wherein the second dosage d2is smaller than the first dosage d1.

Purely by way of example, a ratio between the second dosage d2and a maximum dosage that can be injected by the injector202may be less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

By way of example, a ratio between the second dosage d2and the first dosage d1may be less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

By way of example, the control unit214may be adapted to adjust the first dosage d1of reduction agent204such that a ratio between an actual reductant buffer in the selective catalytic reduction catalyst206and a maximum reductant buffer in the selective catalytic reduction catalyst206at a current operating temperature in the selective catalytic reduction catalyst206is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

By way of example, the control unit214may further be adapted to adjust a third dosage d3of reduction agent204as a part of the deposit removal dosage procedure. Preferably, the injector202may be controlled such that the third dosage d3is injected into the exhaust aftertreatment system during at least a part of the third temporal portion t3, and the control unit214may be adapted to adjust the third dosage d3such that ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in the selective catalytic reduction catalyst206is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

The maximum reductant buffer in the selective catalytic reduction catalyst206is dependent on the operating temperature of the catalyst206, and may be known from, e.g., models of the exhaust aftertreatment system200, look-up tables, and/or empirical data. Further, and purely by way of example, the actual reductant buffer may be estimated based on the precedingly identified future operating sequence300, in conjunction with any other operating data from the internal combustion engine102and/or the exhaust aftertreatment system200, as well as data from the above-mentioned models of the exhaust aftertreatment system200, look-up tables, and/or empirical data.

Purely by way of example, the control unit214may be adapted to identify a deposits parameter indicative of a level of deposits in the portion212of the exhaust aftertreatment system200. The deposits parameter may be indicative of a level of liquid and/or solid deposits. Purely by way of example, the confirmation procedure may comprise confirming that the level of deposits is equal to or exceeds a predeterminable threshold. The deposits parameter may be estimated based on future and/or historical operating data from the internal combustion engine102and/or the exhaust aftertreatment system200, as well as on data from models of the exhaust aftertreatment system200, look-up tables, and/or empirical data.

By way of example, the control unit214may be adapted to identify a temperature parameter indicative of a temperature of the portion212of the exhaust aftertreatment system200. Preferably, the control unit may be adapted to receive information from the temperature sensor216. According to one exemplary embodiment, the control unit214may be adapted to perform the deposit removal procedure in dependence on the temperature parameter. Preferably, the control unit214may be adapted to initiate the second dosage d2in dependence on the temperature parameter, in particular to initiate the second dosage d2in response to detecting that the temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold.

The above operation of the control unit214and the method associated therewith are schematically exemplified inFIG.4. As such, the method400comprises the steps of:402: Identifying the future operating sequence300.404: Performing the confirmation procedure.406: Checking if the confirmation procedure of step404is affirmative or not.408: If the confirmation procedure of step404is affirmative, executing the deposit removal dosage procedure.