SE539615C2 - An engine system lubricated by means of a lubrication oil that forms ammonia-soluble ash when combusted and a vehicle corprising the engine system - Google Patents

Abstract

ABSTRACT 21 An engine system (30) comprising: an internal combustion engine (2) arranged to be operated by a fuel and to belubricated by means of a lubrication oil that forms an ammonia-soluble ash whencombusted; an exhaust gas system for cleaning an exhaust gas flow from the internalcombustion engine, the exhaust gas system comprising a diesel particulate filter(23) arranged to capture particulate matter from the exhaust gases, wherein theparticulate matter comprises the ammonia-soluble ash, an exhaust gas conduit (11) arranged to lead exhaust gases from the internalcombustion engine (2) through the exhaust gas system (10), and injection device (240) arranged to add a solvent comprising ammonia or anammonia-forming compound into the exhaust gas flow upstream of the diesel particulate filter (23), wherein the exhaust gas conduit (11) is arranged to collect the solvent and lead the solvent through the diesel particulate filter (23), thereby dissolving and thus removing the ammonia- soluble ash from the diesel particulate filter (23). ln this way, in-situ cleaning of a diesel particulate filter can be provided. Pig. 3

Description

An engine system lubricated by means of a lubrication oil that forms ammonia-soluble ash when combusted and a vehicle comprising the engine system TECHNICAL FIELD The present invention relates to a use of a lubrication oil that forms ammonia-soluble ashwhen combusted in an engine system, an engine system in which the lubrication oil is used and a vehicle comprising the engine system.BACKGROUND ART Diesel engines are provided with exhaust purification devices with the object of reducingparticles and harmful gases which occur in diesel engine exhaust gases. To regulate emissionsfrom vehicles there are various standards and legal requirements which govern permissiblelevels for exhaust discharges. Vehicles are consequently provided with various kinds ofpurification devices for exhaust gases in an exhaust gas system in order to meet legalrequirements. The exhaust gas system may be arranged for example in a silencer fluidly connected to an exhaust pipe system of a vehicle.

Silencers are used in internal combustion engines to damp engine noise and reduce emissionsand are situated in the engine's exhaust system. Internal combustion engines provided with asilencer may be used in various different applications, e.g. in heavy vehicles such as trucks orbuses. The vehicle may alternatively be a passenger car. I\/lotorboats, ferries or ships,industrial engines and/or engine-powered industrial robots, power plants, e.g. an electricpower plant provided with a diesel generator, locomotives or other applications may havecombustion engines with silencers. The silencer comprises a diesel particulate filter (DPF), alsocalled particulate filter in this context, for exhaust gas after treatment. The particulate filter isintended to catch particles, such as soot particles oxidized into ash. Usually, such a silencer ismounted primarily with regard to available space in the vehicle and without taking intoaccount that the silencer should be dismantled easily, or be easily accessible when serviced.

The particulate filter in the silencer may need to be dismantled in order to be replaced or 2 cleaned of deposited ash, and, in connection therewith, the silencer also usually needs to bedismantled at least partly. This dismantling may become considerably difficult since thesilencer may weigh between 100 to 150 kg and is not always easily accessible. The particulatefilter itself needs to be replaced or cleaned at certain intervals since accumulated ashincreases the back pressure in the exhaust system, which entails increased fuel consumption,for instance. Also, the accumulated ash may render it difficult for the exhaust gases to get incontact with a catalytic coating in the oxidation catalyst, whereby oxidation of the sootparticles into ash is obstructed. Therefore, the ash needs to be removed from the particulate filter.

Usually, the cleaning and/or replacement of the particulate filter takes place in connectionwith service, which typically entails dismantling of the silencer and the particulate filter withapproximately one year's interval. ln cases with high mileages, typically above 300,000 -400,000 km, for a cargo vehicle with a diesel engine driven with alternative fuels, cleaning ofthe particulate filter may need to be carried out at even shorter intervals. The accumulatedash can be difficult to remove and different environmentally unfriendly solvents may beneeded to remove the ash. Also the removal of ash may be laborious and time consuming. lt is thus desirable that cleaning of the particulate filter is facilitated.

There have been several attempts in the prior art to facilitate cleaning of a particulate filter.For example, EP2767690A1 discloses a device for use in clea ning of a particulate filtercomprising a disc unit having apertures and designed to let through air when cleaned througha suction device connected to the silencer sucking air through the opening and backwardsthrough the particulate filter. However, a separate process is needed for the cleaning procedure. Also, it is desirable to avoid further heavy components in the silencer.

WO2014038724 discloses a purification system in which a liquid is supplied to a particulatefilter to promote movement of ash to rear parts of the particulate filter. The particulatematter which is moved in this way is then removed by a subsequent removal processing step.Thus, the particulate matter still needs to be removed from the particulate filter in a specificprocess step. The document WO 2008/053462 A1 describes an example of how cleaning aparticulate filter in a silencer may occur without the filter having to be dismantled from the silencer. However, the particulate matter still needs to be removed from the particulate filter 3in a separate process. Further, DE4313132A1 discloses a cleaning method in which dieselparticulate filter for an exhaust system of a diesel engine is cleaned of deposited particles bymeans of a rinsing liquid which may be water. However, the cleaning method is performed in aseparate process step in which water is lead to the particulate filter via a specific liquid inlet and whereby an interruption in the operation of the diesel engine is required.

Even though there are prior art solutions on how to remove particulate matter fromparticulate filters, there is still a need to improve removal procedures in the existing exhaustgas systems. There is also a great need for a high degree of exhaust gas purification in combustion engines.

SUMMARY OF THE INVENTION ln view of the problems above, it would be desirable to facilitate cleaning of the dieselparticulate filters. The inventors of the present invention have also noted that it would bedesirable to avoid the formation of large deposits of pa rticulate matter that needs to beremoved. Further, it would be desirable that as few interruptions as possible in the operationof the diesel engine are needed. Also it is desirable that the need for service occasions is minimized.

Thus, it is an object ofthe present invention to provide a solution for minimizing the amountof particulate matter that is deposited in a diesel particulate filter. lt is a further object oftheinvention to provide a simple and automatic solution to clean the particulate filter fromparticulate matter. Further, it is an object to provide an engine system in which cleaning canoccur often and regularly during the normal use of the internal combustion engine without aneed to dismantle the particulate filter. Also, it is an objective of the present invention to decrease the number of service occasions.

The above-mentioned objectives are achieved by the invention as defined by the appendedindependent claims. Especially, the objectives are achieved with the present invention whichrelates to a in an engine system comprising:- an internal combustion engine arranged to be operated by a fuel and to belubricated by means of the lubrication oil that forms an ammonia-soluble ash when combusted; 4 - an exhaust gas system for cleaning an exhaust gas flow from the internalcombustion engine, the exhaust gas system comprising a diesel pa rticulate filterarranged to capture particulate matter from the exhaust gases, wherein theparticulate matter comprises the ammonia-soluble ash, - an exhaust gas conduit arranged to lead exhaust gases from the internalcombustion engine to the exhaust gas system, and - an injection device arranged to add an solvent comprising ammonia or anammonia-forming compound into the exhaust gas flow upstream of the dieselparticulate filter, wherein the exhaust gas conduit is arranged to collect the solvent and lead the solventthrough the diesel particulate filter, thereby dissolving and thus removing the ammonia- soluble ash from the diesel particulate filter.

By solvent in this application is meant a liquid which is capable of dissolving ash. The solventused in the present invention comprises ammonia or an ammonia-forming compound. Theammonia-forming compound may be for example urea (carbamide), which forms ammonia byhydrolysis. Urea is used as a reducing agent in the exhaust gas systems and it reduces the NOXcontents of the exhaust gas flow. The solvent is suitably provided as an aqueous solution ofammonia or ammonia-forming compound and the ammonia or ammonia-forming compoundcontent of the aqueous solution may vary for example from about 5-40% by weight of thesolvent. lf ammonia is used as the solvent, the concentration is usually kept below 25% by weight of the solvent to minimize risk for pressure build-up in a solvent reservoir. ln accordance with the present invention the lubrication oil used to lubricate the engine formsan ammonia-soluble ash. This means that the engine oil comprises additives and optionallyother compounds that render the ash ammonia-soluble. By ash is meant the non-volatileproducts and residue formed when the lubrication oil, also referred to as an engine oil, iscombusted. By ammonia-soluble is meant that the ash is capable of being dissolved in ammonia.

Preferably, the amount of the ammonia-soluble ash formed from the lubrication oil is at least 80% by weight based on the total weight of the ash, preferably at least 90% by weight based 5 on the total weight ofthe ash, most preferably at least 95% by weight based on the totalweight of the ash. I\/lost preferably, the ash is completely, i.e. 100%, ammonia-soluble. Thus,the depositions of particulate matter in the diesel particulate filter can be considerablydecreased by means of using lubrication oil forming ammonia-soluble ash after combustion.Therefore, instead of using traditional lubrication oils that normally provide a relatively smallamount of ash after combustion, but wherein the ash is not ammonia-soluble, it has beenrealized that depositions of particulate matter can be decreased since the ash is mostly orcompletely dissolved by means of the added ammonia during the operation of the enginesystem. According to the invention, the exhaust gas conduit is arranged to collect the addedammonia and lead the ammonia through the diesel particulate filter, the ammonia therebydissolving and thus removing the ammonia-soluble ash from the diesel particulate filter (DPF).Therefore, an effective in-situ cleaning ofthe diesel particulate filter can be provided. Also,only minor constructional changes are required for the existing engine systems. A further advantage is that the NOX content of the exhaust gas flow may be further decreased.

Suitably, the engine system of the present invention is customized for the use of lubrication oilforming an ammonia-soluble ash after combustion. Ammonia may be arranged to be added tothe exhaust gas flow daily, and thereby the DPF will flushed with ammonia daily and thus mostof the ash accumulated in the DPF will be dissolved in ammonia. Thus, the DPF will be in situcleaned which is a huge advantage that will reduce the amount of particulate matterdeposited in the particulate filter. Also, the cleaning occurs often without a need to dismantlethe particulate filter. Therefore, it will be possible to decrease the amount of service occasions.

The injection device may comprise a valve which is fluidly connected to a solvent reservoir.The solvent may be arranged to be fed from the reservoir to the injection device by means ofa feeding pump. The feeding pump is suitably operated by an electric motor, whereby it is easy to control the operation of the feeding pump.

According to one embodiment of the invention, the injection device may be further arrangedto inject a reducing agent into the exhaust gas flow upstream ofthe diesel particulate filter. lnthis way the NOX content of the exhaust gases may be further reduced while the amount of components in the exhaust gas system may be minimized. Also, in this way the same injection 6device may be used for the injection of both the solvent and the reducing agent, and thus the amount of required components in the engine system can be reduced.

The solvent may be the reducing agent, i.e. the reducing agent used in connection with aselective catalytic reduction (SCR) purification system. The SCR system may comprise a furtherinjection arrangement for adding a reducing agent to the exhaust gas flow. The reducing agentis used in order to reduce NOX contents of the exhaust gas flow. The reducing agent may befor example a mixture of water and urea, e.g. a product with a trade name AdBlue®, whichcomprises a mixture of 32.5% urea and water. The solvent reservoir may also constitute areservoir for the reducing agent. ln this way, further reduction of components in the engine system may be achieved.

The injection device may com prise a valve arranged to be positioned in a first position inwhich it is arranged to inject the reducing agent into the exhaust gas flow and a secondposition in which it is arranged to inject the solvent into the exhaust gas flow. ln this way, thesame injection device may be used to inject different liquids separately to the exhaust gas flow.

The engine system may further comprise a control system arranged to control the operationof the injection device. Thereby it is possible to activate or inactivate the injection device asdesired. For example the control system may be arranged to control the operation ofthe injection device at pre-determined intervals and/or pre-determined conditions.

To define the conditions in which the injection device is to be activated, i.e. to inject thesolvent into the exhaust gas flow, the exhaust gas system may further comprise a first sensorarranged upstream ofthe diesel particulate filter for measuring a pressure drop over thediesel particulate filter or the pressure of the exhaust gas flow before filtration. The firstsensor is connected to the control system. The first sensor may be a differential pressuretransmitter that measures the pressure drop over the diesel particulate filter. Differentialpressure transmitters are devices that measure the difference in pressure between twopoints. Such transmitters are available on the market by several suppliers and are known tothe skilled person. According to another variant, the first sensor measures the pressure of theexhaust gas flow before filtration. Thus, it will be possible to indicate any abnormal increase in the pressure caused by depositions of particulate matter in the diesel particulate filter. 7The control system preferably comprises means arranged to compare the measured pressuredrop value or the value for the pressure of the exhaust gas flow with a predetermined valuefor the pressure drop or the pressure ofthe exhaust gas flow and create an error code ifthepressure drop value or the pressure value differs from the predetermined value. ln this way itwill be possible to for example send a command to the injection device that solvent is to be injected to the exhaust gas flow.

According to another embodiment, the exhaust gas system may further comprise a secondsensor for measuring the pressure of the exhaust gas flow. The second sensor may bearranged downstream ofthe diesel particulate filter to measure the pressure after filtration.The second sensor is connected to the control system. ln this way it is possible to compare thepressure value before and after the diesel particulate filter and thus for example calculate a value for the pressure drop over the diesel particulate filter.

The first sensor preferably comprises, or the first and second sensors comprise, meansarranged to generate a measuring signal comprising data relating to the measured pressurevalue or pressure drop value. The control system comprises means for receiving the measuringsignals from the first sensor and/or the second sensor, respectively. ln this way it will be possible to utilize the measured data in the control system in an advantageous way.

The control system also preferably comprises means arranged to calculate a pressure dropover the diesel particulate filter from the received measuring signal from the first sensor andthe second sensor. The control system may then further comprise means arranged to comparethe calculated pressure drop value with a predetermined pressure drop value and create an error code if the measured pressure drop value differs from the predetermined value. ln case there are depositions of particulate matter in the diesel particulate filter, the pressuredrop over the diesel particulate filter will be greater than in case there are no depositions.Alternatively or additionally, the pressure of the exhaust gas flow will increase upstream ofthe diesel particulate filter. The measured or calculated pressure drop or pressure value isthen compared with the pre-determined pressure drop or pressure values and an error code iscreated if the measured or calculated values differ from the predetermined values. For example, in case of higher pressure drop or pressure values than the pre-determined values, 8the control system may command the injection device in the engine system to add solvent or alternatively send an error signal indicating that service is required.

By means of using a measurement indicating or ca|cu|ating a pressure drop over the dieselparticulate filter or by measuring the pressure of the exhaust gas flow before filtration, it ispossible to get an indication of depositions of particulate matter in the diesel particulate filterin an effective way. The control system may comprise means arranged to control the injectiondevice so as to add the solvent into the exhaust gas flow, e.g. in a pre-determined or desiredamount. Thus, the control system is arranged to command the engine system to inject adesired amount of the solvent into the exhaust gas flow or alternatively send an error signal indicating that service is required.

The control system may also comprise means arranged to control the internal combustionengine or the engine system based on the measured or calculated pressure drop value orvalue for the pressure of the exhaust gas flow so as to increase an amount of condensedwater. Condensed water is normally formed during the cold operation of the vehicle. ln someoccasions it is desirable to increase the amount of condensed water so that more liquid canflush the diesel pa rticulate filter and thus more effective cleaning of the diesel pa rticulate filter can be obtained.

The control system may be adapted to receive the measuring signals continuously. lt is alsopossible that the control system is adapted to receive the measuring signals periodically, i.e.for example at certain intervals or in case of manually controlled random intervals. An example of a random interval is for example at start ofthe engine or vehicle.

Preferably, the first sensor and/or second sensor are connected to the control unit via acommunication bus, such as CAN-bus. Thus, the pressure measurements may be made a part of the total control system of the vehicle.

The invention also relates to a vehicle comprising the engine system as defined above.

Further objects, advantages and features of the invention are described in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic side view of a vehicle comprising an engine system according tothe present invention.

Fig. 2 is a schematic drawing showing path of the exhaust gas flow through an exhaustgas system.

Fig. 3 is a schematic drawing showing an engine system according to one embodimentofthe present invention.

Fig. 4 is a schematic drawing showing an engine system according to another embodiment of the present invention.

DETAILED DESCRIPTION As mentioned above, combustion engines are used in various types of applications andvehicles today, e.g. in heavy vehicles such as trucks or buses, in cars, motorboats, ferries orships. They may also be used in industrial engines and/or engine-powered industrial robots,power plants, e.g. electric power plants provided with a diesel generator, and in locomotives.The engine system according to the present invention is intended for an internal combustionengine which is fluidly connected to an exhaust gas system by means of an exhaust gasconduit or pipe. The engine system may be employed for example in a vehicle, e.g. in a truckor bus. The exhaust gas system of the engine system can be placed in a silencer orcomponents of the exhaust gas system may be arranged in another way, for example in aseries of components and they do not need to be arranged in a silencer. For example in caseof buses, it may be difficult to place the exhaust gas system in a silencer, since the floor of thebus needs to be low and/or the bus must contain a maximal amount of seats, whereby bulky silencers are difficult to place in a bus. ln Fig. 1 an example of a vehicle 1 comprising an engine system 30 comprising an internal combustion engine 2 and an exhaust gas system 10 is shown in a schematic side view. Theinternal combustion engine 2 powers the vehicle's tractive wheels 4 via a gearbox 6 and apropeller shaft 8. The internal combustion engine 2 is arranged in fluid connection with an exhaust gas system 10 which is fitted at least partly in a silencer 12. The exhaust gas system 10 may further comprise additional exhaust gas pipes or conduits, exhaust manifold and a controlsystem, for example. The internal combustion engine 2 is powered by fuel 14 supplied to it viaa fuel system 16 which comprises a fuel tank 18. The fuel is suitably diesel, such as biodiesel ora corresponding fuel. The internal combustion engine 2 is lubricated by means of an engine oil, which according to the present invention forms an ammonia-soluble ash when combusted.

The internal combustion engine of the present invention is suitably a diesel engine. Theinternal combustion engine is arranged to be operated by a fuel and to be lubricated by meansof a lubrication oil that forms an ammonia-soluble ash when combusted. The lubrication oilcontains at least one additive that renders the ash ammonia-soluble. Such oils can be easilydetermined and they can be classified as forming ammonia-soluble ash. The engine system ofthe present invention is customized for the lubrication oils forming ammonia-soluble ash. Thelubrication oils suitable for use in the customized engine system of the present invention canthen be specified for the users. The fuel can be any of the known kinds, such as petroleumdiesel, synthetic diesel or biodiesel, also called fatty-acid methyl ester (FAM E) which isobtained from vegetable oil or animal fats that have been trans-esterified with methanol. The fuel may also be a hydrogenated oil or fat or dimethyl ether, DI\/IE.

The desired solubility ofthe ash can be obtained by using additives in the lubrication oil thatform ammonia-soluble compounds. Many metals form strong complexes with ammonia,ammine complexes, which help dissolving the ash. The solubility in ammonia may be achievedin different ways and it is not essential how the ammonia-solubility is achieved. Thus, anyadditive forming an ammonia-soluble ash can be chosen. The amount ofthe ammonia-solubleash formed from the lubrication oil is at least 80% by weight based on the total weight of theash, preferably at least 90% by weight based on the total weight of the ash, most preferably atleast 95% by weight based on the total weight ofthe ash. Preferably, the ash is completely ammonia-soluble, i.e. 100% by weight of the ash is ammonia-soluble.

The engine system of the present invention comprises an internal combustion engine and anexhaust gas system which can be arranged in a silencer. An exhaust gas conduit is arranged tolead exhaust gases from the internal combustion engine through the exhaust gas system. Alsothe exhaust gas conduit is arranged to collect the solvent and lead the solvent through the diesel particulate filter, whereby the ash is dissolved and thus removed from the diesel 11 particulate filter. The exhaust gas conduit also suitably collects condensation water formedduring the operation ofthe internal combustion engine. The solvent and the possiblecondensed water, i.e. the liquids, may be collected into the exhaust gas conduit by means ofany suitable means. The liquids can then be lead through the DPF for example by arrangingthe exhaust gas conduit in a suitable way so that a liquid flow can be obtained. The silencer inwhich at least part of the exhaust gas system is accommodated comprises a casing comprisingat least one inlet for leading an exhaust gas flow into the silencer. The silencer may compriseseveral inlets. The exhaust gas system may also comprise a diesel oxidation catalyst (DOC)which can be arranged downstream of the inlet in a silencer. The DOC is a unit designed tooxidize the exhaust gases. DPF is a unit designed to remove diesel particulate matter or sootfrom the exhaust gas flow. The DPF can for example be a catalysed soot filter (CSF). The soot isfurther oxidized or burned-off or combusted to ash in the particulate filter, e.g. duringregeneration ofthe particulate filter. The diesel particulate filter may be regenerated with orwithout a catalyst. The regeneration can then be performed by means ofthe heat from the engine's normal operation.

The exhaust gas system can further comprise a selective catalytic reduction (SCR) purificationsystem which comprises an injection arrangement for adding a reducing agent to the exhaustgas flow in order to reduce NOX contents of the exhaust gas flow. The reducing agent may befor example a mixture of water and urea, e.g. a product with a trade name AdBlue®, whichcomprises a mixture of 32.5% urea in water. The exhaust gas flow and the reducing agent aremixed and vaporised in a vaporisation chamber which is arranged downstream of the injectionarrangement. Further, a selective catalytic reduction (SCR)-catalyst is arranged downstream ofthe vaporisation chamber. The SCR- catalyst may comprise vanadium, iron or copper catalystin which NOX is converted to water vapour and nitrogen. An ammonia slip catalyst (ASC),which is a unit designed to convert any NHgslip to NZ and H20, may be arranged downstreamof the SCR-purification system. All these components may be arranged as separatecomponents in series or in a silencer. ln case the components are arranged in a silencer, anoutlet for leading the exhaust gas flow out from the silencer is arranged downstream of the SCR- catalyst and possible ASC. The silencer may comprise several outlets.

The exhaust gas system, or the silencer comprising the exhaust gas system, does not necessarily need to comprise a DOC and/or an ASC. On the other hand, the exhaust gas system 12 may comprise one or more of each of DOC and ASC together with DPF. ln case the exhaust gassystem does not comprise a DOC, the exhaust gas flow is arranged to flow to the DPF. |fthesilencer comprises a DOC and a DPF, the exhaust gas flow is arranged to flow through the DOCto the DPF. The exhaust gas flow is arranged to flow through the DPF to the injectionarrangement ifthe silencer comprises a DPF and not a DOC. |fthe exhaust gas system does notcomprise an ASC the exhaust gas is arranged to flow from the SCR purification system to an outlet of the exhaust gas system of the silencer.

Fig. 2 depicts schematically examples of possible ways the flow of exhaust gases can flowthrough an exhaust gas system 10. The arrows in Fig. 2 illustrate the flow 21 of exhaust gases,but the reference number 21 is only attached to one of the arrows. The exhaust gas system 10comprises an inlet 20 for leading an exhaust gas flow 21 into the exhaust gas system 10 and adiesel oxidation catalyst (DOC) 22 is arranged downstream of the inlet 20. A diesel particulatefilter (DPF) 23 is arranged downstream ofthe DOC 22 and the DPF 23 can for example be acatalysed soot filter (CSF). The exhaust gas flow may be arranged to flow directly from the DPF23 to an outlet 29 ofthe exhaust gas system 10 or the exhaust gas flow may be arranged toflow to an injection arrangement 24, which can be arranged upstream and/or downstream ofthe DPF 23 for adding a reducing agent to the exhaust gas flow 21 in order to reduce NOXcontents of the exhaust gas flow 22. A vaporisation chamber 25 for vaporisation of thereducing agent, is arranged downstream of the injection arrangement 24. A selective catalyticreduction (SCR)-purification system 27 comprising a SCR-catalyst 26 is arranged downstreamof the vaporisation chamber 25. An ammonia slip catalyst (ASC) 28 may be arrangeddownstream ofthe SCR-purification system 27 and an outlet 29 for leading the exhaust gas flow 21 out from the exhaust gas system 10 is arranged downstream of the ASC 28. ln case the exhaust gas system 10 does not comprise a DOC 22, the exhaust gas flow 21 isarranged to flow from the inlet 20 to the injection arrangement 24 via DPF 23. lf the exhaustgas system 10 does not comprise an ASC 28 the exhaust gas flow 21 is arranged to flow from the SCR purification system 27 to the outlet 29.

The internal combustion engine comprises an air intake manifold leading air to the cylinders ofthe internal combustion engine. An intake throttle is arranged upstream of the air intake manifold for adjusting fresh air flow into the intake manifold. By adjusting the amount of fresh 13 air to the internal combustion engine, it is possible to for example adjust the amount ofcondensed water formed during cold operation ofthe vehicle. ln some occasions it may bedesirable to additionally utilize condensed water formed by the cold operation ofthe internalcombustion engine to further increase the amount of liquid that can flush the dieselparticulate filter. This may be done for example by controlling the operation ofthe internalcombustion engine or the engine system and for example by increasing the fuel-air ratioduring the cold operation and/or the cold start of the internal combustion engine which leadsto increased amount of condensed water. The fuel-air ratio may be adjusted by for examplecontrolling the operation ofthe internal combustion engine during the cold start/coldoperation such that the fuel/air ratio is kept high while the number of revolutions is kept low.As a result, more condensed water will be obtained, since high fuel-air ratio increases thequota of water in the exhaust gases and low temperature of the exhaust gases provides morecondensed water. Alternatively or additionally the amount of condensed water may beincreased by adjusting, suitably by decreasing, the amount of fresh air that flows into theinternal combustion engine via an intake manifold by means of an intake throttle arrangedupstream ofthe intake manifold. Further, as an example, it is possible to increase the amountof condensed water by decreasing the temperature the exhaust gases. This can be done forexample by means of an exhaust gas recirculation (EGR) arrangement arranged in fluidconnection with the exhaust pipe and the intake manifold. At least part ofthe exhaust gasflow from the internal combustion engine can be recirculated from the exhaust pipe through the EGR, which comprises an EGR cooler which reduces the temperature of the EGR gases.

Fig. 3 shows a schematically an engine system 30 according to one variant ofthe presentinvention. The engine system 30 comprises an internal combustion engine 2 in fluidconnection with the exhaust gas system 10 as described above by means of an exhaust gasconduit 11. The exhaust gas system comprises DOC 22, DPF 23, vaporisation chamber 25fluidly connected to an injection arrangement 24, SCR-purification system 27 and ASC 28. The exhaust gases are arranged to flow out from the exhaust gas system 10 via an outlet 29.

An air intake throttle 37 is arranged to adjust the amount of intake air to the internalcombustion engine via an air intake manifold (not shown). Downstream of the internalcombustion engine 2, the exhaust gas conduit 11 is fluidly connected to an exhaust gas recirculation system via an EGR conduit 38. The exhaust gases are cooled by leading the 14exhaust gas flow through an EGR cooler 39 back to the internal combustion engine 2 downstream ofthe air intake throttle 37.

A first sensor 35 for measuring the pressure drop over the DPF 23 or the pressure of theexhaust gas flow is arranged downstream ofthe DOC 22 and upstream ofthe DPF 23. Asshown in more detail in Fig. 3, the first sensor 35, e.g. a pressure measurement device, isconnected to a communication bus 33, such as CAN-bus, via a connection 31, and the CAN-bus33 communicates with a control system 34 of the vehicle. The first sensor 35 is arranged togenerate a measuring signal comprising data relating to the measured pressure drop orpressure value. The first sensor may be a pressure measurement device or it may be adifferential pressure transmitter that measures a pressure drop over the DPF 23. The controlsystem 34 comprises means for receiving the measuring signal from the first sensor 35. Thecontrol system 34 suitably comprises means arranged to compare the received measuringsignal from the first sensor 35 with a predetermined pressure drop or pressure value andcreate an error code if the measured value differs from the predetermined value. ln this way,the operator of the vehicle will get an indication that the DPF needs to be cleaned or changed.The engine system also comprises an injection device 240 arranged to add a solvent into theexhaust gas flow upstream ofthe DPF 23. The injection device 240 is also connected to thecontrol system 34 via CAN-bus 33. Thus, when the measured pressure drop and/or pressurevalue differs from the predetermined value, the control system 34 commands the injectiondevice 240, which is fluidly connected to a solvent reservoir 130, to inject solvent into the exhaust gas flow in a desired amount.

The exhaust gas conduit 11 is arranged such that it collects the added solvent and optionallycondensed water formed by the cold operation of the internal combustion engine and leadsthe formed aqueous solution of the solvent through the diesel particulate filter 23. Theaqueous solution ofthe solvent thereby dissolves and thus removes the ammonia-soluble ashfrom the diesel particulate filter 23. Also, the control system 34 may control the internalcombustion engine 2 so as to increase the amount of condensed water formed during the coldoperation and/or the cold start, whereby it is possible to improve the cleaning effect since more liquid can be flushed through the diesel particulate filter 23.

Further in Fig. 3, a means 24 for the injection of a reducing agent is fluidly connected to areducing agent reservoir 140. The means 24 may be connected to the control system 34 (not shown).

The injection device 240 comprises preferably a valve (not shown) which is fluidly connectedto the solvent reservoir 130. The solvent is arranged to be fed from the reservoir 130 to theinjection device 240 by means of a feeding pump (not shown). The feeding pump may be an electrical pump and it is preferably connected to the control system 34.

Another variant of the invention is shown in Fig. 4. The system in Fig. 4 corresponds to thesystem in Fig. 3 except that the means 24 for injection of a reducing agent into the exhaust gasflow that is arranged downstream ofthe DPF 23, is fluidly connected via a conduit 150 to thesolvent reservoir 130, since the solvent is the reducing agent and the solvent reservoir 130also constitutes a reservoir for the reducing agent. Of course, in case the reducing agent isother than the solvent, it would be possible to incorporate a separate reservoir for thereducing agent, as shown in the embodiment of Fig. 3. ln the arrangement of Fig. 4 theinjection device 240 can be additionally arranged to be used for the injection of the reducingagent upstream of the DPF 23. ln that case, and ifthe reducing agent is other than the solvent,the injection device 240 should be fluidly connected to the reducing agent reservoir via aconduit. Further, the embodiment shown in Fig. 4 differs from the embodiment shown in Fig.3 in that a second sensor 36 for measuring the pressure ofthe exhaust gas flow is arrangeddownstream ofthe DPF 23 to indicate the pressure after filtration, i.e. downstream ofthe DPF23. The second sensor 36 is also connected to the communication bus 33, such as CAN-bus, viaa connection 32, and the CAN-bus 33 communicates with the control system 34 ofthe vehicle.ln this embodiment of the invention, the control system 34 suitably comprises meansarranged to calculate the pressure drop from the received measuring signals from the firstsensor 35 and the received measuring signal from the second sensor 36. The control system34 is then arranged to compare the pressure drop with a predetermined value for thepressure drop and create an error code if the calculated pressure drop differs from thepredetermined pressure drop. Therefore, it is possible for the control system 34 to control theengine system and the injection device 240 so as to inject a desired amount of the solvent intothe exhaust gas flow in case the value for the pressure drop is not acceptable, i.e. within the pre-determined values. Alternatively it is possible to send an error code and warn the 16operator ofthe vehicle that the DPF 23 needs to replaced or cleaned at service as soon as possible. ln both engine systems shown in Fig. 3 and 4, it is also possible to obtain an increased amountof condensed water that thereby increases the amount of liquid that is to be collected by theexhaust gas conduit and lead through the DPF 23. The amount may be increased by controllingthe operation ofthe internal combustion engine 2 or the engine system 30 by means of thecontrol system 34 connected to the internal combustion engine 2. For example by controllingthe internal combustion engine such that an increased fuel-air ratio during the cold operationand/or the cold start of the internal combustion engine is obtained, the amount of condensedwater can be increased. The fuel-air ratio may be adjusted by for example by controlling theoperation of the internal combustion engine 2 during the cold start/cold operation such thatthe fuel/air ratio is kept high while the number of revolutions is kept low. As a result, anincreased amount of condensed water will be obtained, since the high fuel-air ratio increasesthe quota of water in the exhaust gases and low temperature of the exhaust gases providesmore condensed water. Alternatively or additionally the amount of condensed water may beincreased by adjusting the amount of fresh air that flows into the internal combustion engine2 via an intake manifold by means of an intake throttle 37 arranged upstream of the intakemanifold. Further, it is possible to increase the amount of condensed water by decreasing thetemperature of the exhaust gases. This can be done for example by means of an exhaust gasrecirculation (EGR) arrangement arranged in fluid connection with the exhaust conduit 11 andthe intake manifold. At least part of the exhaust gas flow from the internal combustion enginecan be recirculated from the exhaust pipe 11 through the EGR pipe 38, which comprises anEGR cooler 39 which reduces the temperature of the EGR gases. Therefore it can be assuredthat the DPF 23 will be flushed with a larger amount of liquid and thus the amount ofthe accumulated ash in the DPF 23 can be effectively decreased.

The control system 34 may be adapted to receive the measuring signals from the first 35and/or the second sensor 36 continuously. lt is also possible that the control system 34 isadapted to receive the measuring signals periodically, i.e. for example at certain intervals or incase of manually controlled random intervals. An example of a random interval is for example at start of the engine or vehicle. 17 Generally the control system 34 comprises or is connected to a CAN bus 33, as shown in Fig. 3and 4, and comprises one or more communication busses to interconnect a number ofelectronic control units (ECUs), or controllers, and various components of the vehicle 1. Such acontrol system 34 may comprise a large number of control units. The control system 34function may be arranged to receive signals from various sensors in the vehicle and thuscontrol the vehicle accordingly. Further, the control of the vehicle can be performed byprogrammed instructions. These programmed instructions typically include a computerprogram, which when the program code is executed in a computer, achieves that saidcomputer carries out the desired action such as the steps ofthe present invention described above. lt should be understood that the examples described above in connection with Fig. 1-4 are tobe regarded as examples not limiting the scope of the invention, which is defined in the appended claims.

Claims (5)

18CLAll\/IS

1. An engine system (30) comprising: an internal combustion engine (2) arranged to be operated by a fuel and to belubricated by means of a lubrication oil comprising at least one additive thatrenders ash formed by combustion of the lubrication oil ammonia-soluble; - an exhaust gas system (10) for cleaning an exhaust gas flow from the internalcombustion engine (2), the exhaust gas system (10) comprising a diesel particulatefilter (23) arranged to capture particulate matter from the exhaust gases, whereinthe particulate matter comprises the ammonia-soluble ash, - an exhaust gas conduit (11) arranged to lead exhaust gases from the internalcombustion engine (2) through the exhaust gas system (10) ), and - an injection device (240) arranged to add a solvent comprising ammonia or anammonia-forming compound into the exhaust gas flow upstream ofthe dieselparticulate filter (23), wherein the exhaust gas conduit (11) is arranged to collect the solvent and lead thesolvent through the diesel particulate filter (23), thereby dissolving and thus removing the ammonia-soluble ash from the diesel particulate filter (23). An engine system according to claim 1, characterized in that the injection device (240)comprises a valve which is fluidly connected to a solvent reservoir (130), wherein thesolvent is arranged to be fed from the solvent reservoir (130) to the injection device (240) by means of a feeding pump. An engine system according to claim 1 or 2, characterized in that the injection device (240)is further arranged to inject a reducing agent into the exhaust gas flow upstream of the diesel particulate filter (23). An engine system according to claim 3, characterized in that the solvent is the reducing agent and the solvent reservoir also constitutes a reservoir for the reducing agent. An engine system according to claim 3, characterized in that the injection device (240) comprises a valve arranged to be positioned in a first position in which it is arranged to 10. 11. 19inject the reducing agent into the exhaust gas flow and a second position in which it is arranged to inject the solvent into the exhaust gas flow. An engine system according to any one of claims 1 to 5, characterized in that the enginesystem (10) further comprises a control system (34) arranged to control the operation of the injection device (240). An engine system according to c|aim 6, characterized in that the control system (34) isarranged to control the operation of the injection device (240) at pre-determined intervals and/or pre-determined conditions. An engine system according to c|aim 7, characterized in that the exhaust gas system (10)further comprises a first sensor (35) arranged upstream of the diesel particulate filter (23)for measuring a pressure drop over the diesel particulate filter (23) or the pressure of theexhaust gas flow (21) before filtration, and the first sensor (35) is connected to the control system (34). An engine system according to c|aim 8, characterized in that the control system (34)comprises means arranged to compare the measured pressure drop value or the value forthe pressure of the exhaust gas flow with a predetermined value for the pressure drop orthe pressure of the exhaust gas flow and create an error code if the pressure drop value or the pressure value differs from the predetermined value. An engine system according to c|aim 8 or 9, characterized in that the exhaust gas system(10) comprises a second sensor (36) arranged downstream ofthe diesel particulate filter(23) for measuring the pressure of the exhaust gas flow (21) after filtration and the second sensor (36) is connected to the control system (34). An engine system according to c|aim 10, characterized in that the control system (34)comprises means arranged to calculate a pressure drop over the diesel particulate filter from the received measuring signals from the first sensor (35) and the second sensor (36). 12 13. 14. 15. .An engine system according to claim 11, characterized in that the control system (34) comprises means arranged to compare the calculated pressure drop value with apredetermined pressure drop value and create an error code ifthe measured pressure drop value differs from the predetermined value. An engine system according to any one of claims 8-12, characterized in that the controlsystem (34) comprises means arranged to control the injection device (240) so as to add the solvent into the exhaust gas flow. An engine system according to claim 13, characterized in that the control system (34)further comprises means arranged to control the internal combustion engine (2) or theengine system (30) based on the measured or calculated pressure drop value or value for the pressure ofthe exhaust gas flow so as to increase an amount of condensed water. Vehicle (1), characterized in that it comprises the engine system (30) according to any one of claims 1-14.