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    • 专利摘要:
    The present invention relates to a method of regenerating a particulate filter (202) in a post-treatment system (200), said particulate filter (202) being adapted to treat an exhaust gas mass flow emitted at an internal combustion engine (110), wherein said pre-combustion is supplied. . The method comprises the steps of - determining a representation of a temperature of the combustion supplied air, - determining a representation of a pressure of the combustion supplied air, and - based on said representations of temperature and pressure of said air supplied to said combustion, controlling said combustion engine ( 10l) so that the magnitude of the exhaust gas mass flow emitted during combustion essentially corresponds to a first value. Fig. 5
    公开号:SE1050890A1
    申请号:SE1050890
    申请日:2010-08-31
    公开日:2012-03-01
    发明作者:Carl-Johan Karlsson；Klas Telborn
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    l0l5At the combustion engine fuel, the combustion in the cylinderssoot particles are formed. Particulate filter is used to capturethese soot particles, and works in such a way that the exhaust streamled through a filter structure where soot particles are captured fromthe passing exhaust stream and is stored in the particulate filter.
    The particulate filter is filled with soot as the vehicle is driven,and sooner or later the filter must be emptied of soot, whichusually accomplished by means of so-called regeneration.
    Regeneration means that the soot particles, which mainlyconsists of carbon particles, is converted to carbon dioxide and / orcarbon monoxide in one or more chemical processes, and essentiallyregeneration can take place in two different ways. On the one hand, regeneration canhappen through so-called oxygen (O2) -based regeneration, also called activeregeneration. During active regeneration, carbon is converted with the helpof oxygen to carbon dioxide and heat.
    This chemical reaction requires relatively highparticle filter temperatures to desired reaction rate(emptying speed) should occur at all.
    Instead of active regeneration, NO2-based regeneration,also called passive regeneration, is applied. When passiveregeneration nitric oxide and carbon monoxide are formed by a reactionbetween carbon and nitrogen dioxide. The advantage of passive regenerationis that desired reaction rates, and hence the ratewith which the filter is emptied, can be achieved at significantly lowertempelfâtlllfeï.
    Since the regeneration is temperature dependent, both are takentypes of regeneration measures to raise the particulate filtertemperature and thus obtain a faster regeneration. Atfavorable operating conditions, this regeneration can be performedduring operation, whereby the regeneration can thus be performedsubstantially without adversely affecting the driver of the vehicle.l0l5However, there are situations / operational cases where the vehicleperformance is such that regeneration during travel can notcarried out efficiently. Although the vehicle periodically canperformed under regeneration favorableconditions, it may also be the case that theseconditions occur at too sparse intervals orfor too short periods of time. This means thatthe particulate filter will sooner or later achieve onedegree of filling that regeneration must be performed in order to the vehiclemust be able to be performed in a safe and desired way.
    In such situations, the vehicle may therefore be requiredstopped, whereby the so-called parked regeneration, ie. regenerationwith the vehicle stationary, then performed.
    When regenerating when the vehicle is stationary, however, it is desirablethat the regeneration can be carried out as quickly as possible,and also in such a way that each time regeneration is performedthis takes essentially the same amount of time, so that the driver of the vehiclethus know how long the regeneration takes. Hereby it canalso ensure that the particulate filter at completionregeneration has been emptied to the desired extent.
    However, this can, especially in the case of passive regeneration, constitute onedifficulty. When stationary passive regeneration is raisedthe temperature of the particulate filter at least by addingunburned fuel for the exhaust stream, this being unburnedfuel is then allowed to oxidize (burn) inthe finishing system to generate heat such asraises the temperature of the particulate filter. This oxidation of fuelhowever, has a negative effect on the formation of it in passiveregeneration required the nitrogen dioxide, therefore desiredregeneration rate can be difficult to achieve.
    Thus, there is a need for an improved solutionpassive particle filter regeneration.l0l5Summary of the inventionIt is an object of the present invention thatprovide a procedure for regeneratingparticulate filter in an efficient manner. This purpose is achieved througha method according to the characterizing part of claimsl.
    The present invention relates to a method ofregeneration of a particulate filter into oneaftertreatment system, said particle filter beingset up for the treatment of a by a combustion in ainternal combustion engine emitted exhaust gas mass flow, whereby air is suppliedsaid combustion.
    The method comprises the steps of:determine a representation of a temperature for it tothe combustion supplied to the air,determine a representation of a print for it tothe combustion supplied to the air, and- based on said representations of temperature and pressurefor said air supplied to said combustion control saidinternal combustion engine so that the size of it at the time of combustionemitted exhaust gas mass flow substantially corresponds to a firstvalue.
    The present invention has the advantage that by controllingthe speed of the internal combustion engine based on that of the internal combustionsupplied air temperature and pressure can exhaust gas mass flowcontrolled against a certain value, thus thisexhaust mass flow can be maintained during regeneration regardless of theprevailing environmental conditions. Thus, whetherthe vehicle is in a hot or cold environment, andwhether the prevailing air pressure is high or low, essentiallythe same exhaust mass flow is always obtained. This is also possiblelOl5ensure that regeneration will always takeessentially the same amount of time.
    Said first value can be determined in an applicable manner. Theexhaust gas mass flow as from a regeneration point of view in passiveregeneration constitutes a favorable flow depends onthe possibility of the aftertreatment system to convert NO toNO2. This is due to e.g. on the size of it inthe finishing system commonthe oxidation catalyst (ie the total area of theprecious metal coated surfaces of the catalyst). Presentinvention is also applicable to systems thereoxidation catalyst is missing, and where conversion of NO to NO2takes place either in the particle filter or with the help of something elseappropriate body. The larger the oxidation catalyst (and / orprecious metal coated surfaces in the particulate filter), the largerexhaust mass flow can be set without conversion of NO to NO2too negatively affected by the oxidation catalystoxidation of unburned fuel in the exhaust stream.
    Determination of said first value can therefore e.g. achievedby testing the catalyst at different exhaust mass flows withsimultaneous supply of unburned fuel, whereby thethe resulting NO2 conversion can be determined for different flowsand optimal flow, ie. the mass flow at whichthe regeneration reaches a maximum regeneration rate, thus candetermined.
    The optimal exhaust mass flow can e.g. stored in the vehiclecontrol system for use as setpoint when parkedregeneration.
    The most advantageous flow during regeneration can e.g. alsodepend on the amount of unburned fuel suppliedthe exhaust gas flow, so in one embodiment different setpointsused for different amounts of fuel for supply tothe exhaust gas flow.
    Additional features of the present invention andbenefits thereof will be apparent from the following detaileddescription of exemplary embodiments and those attachedthe drawings.
    Brief description of the drawingsFig. 1a shows a driveline in a vehicle at whichthe present invention can be used to advantage.
    Fig. 1b shows an example control unit in a vehicle control system.
    Fig. 2 shows an example of a finishing system in onevehicle in which the present invention is advantageousCan be used.
    Fig. 3 shows an example of regeneration (soot burn-out)the speed as a function of the amount of soot inthe particulate filter, and its temperature dependence.
    Fig. 4 shows the temperature dependence for oxidation of nitric oxideto nitrogen dioxide in an oxidation catalyst.
    Fig. 5 schematically shows a method according to aexemplary embodiment of the present invention.
    Detailed description of preferred embodimentsFig. 1a schematically shows a heavy exemplary vehicle 100, such asa truck, bus or the like, according to aexemplary embodiment of the present invention. That in Fig. 1aschematically shown the vehicle 100 comprises a front pair of wheels111, 112 and a rear wheel pair with drive wheels 113, 114. The vehiclefurther comprising a driveline with an internal combustion engine 101,which in a conventional manner, via one on the internal combustion engine101 output shaft 102, is connected to a gearbox 103,for example via a coupling 106.
    A shaft 107 emanating from the gearbox 103 drives the drive wheels113, 114 via a final gear 108, such as e.g. a usualdifferential, and drive shafts 104, 105 connected to saidfinal gear 108.
    The vehicle 100 further includes a finishing system(exhaust purification system) 200 for treatment (purification) ofexhaust emissions from the internal combustion engine 101.
    The finishing system is shown in more detail in Fig. 2. The figureshows the internal combustion engine 101 of the vehicle 100, where they atthe combustion generated exhaust gases are led via a turbocharger220 (in turbo engines often drives it from combustionresulting exhaust gas a turbocharger which in turncompresses the incoming air to the cylinderscombustion). The function of the turbocharger is very well known,and is therefore not described in more detail here. The exhaust stream is then ledvia a tube 204 (indicated by arrows) to a particle filter(Diesel Particulate Filter, DPF) 202 via enOxidation Catalyst (DOC) 205.
    Furthermore, the finishing system includes a downstream rethe particulate filter 202 provided with an SCR (Selective CatalyticReduction) catalyst 201. SCR catalysts useammonia (NH3), or a composition from which ammonia cangenerated / formed, as an additive for reducing the amountnitrogen oxides NOX.
    The particle filter 202 may alternatively be arranged downstreamThe SCR catalyst 201, although this may be smalleradvantageous when the present invention relates to so-calledpassive regeneration where the regeneration depends on thenitrogen oxides normally reduced by the SCR catalyst. According toan embodiment of the present invention comprisesl0l5the finishing system does not have any SCRcatalyst.
    The oxidation catalyst DOC 205 has several functions, andutilizes the excess air that the diesel engine process generally hasgives rise to in the exhaust stream as a chemical reactor togetherwith a noble metal coating in the oxidation catalyst.
    The oxidation catalyst is normally used primarily for oxidationresidual hydrocarbons and carbon monoxide in the exhaust gas tocarbon dioxide and water. In the oxidation of hydrocarbons (ieunburned fuel) also forms heat, which is used bypresent invention for raising the particulate filtertemperature by adding fuel to the exhaust stream, whereinthis fuel was then allowed to burn over the oxidation catalystto thereby generate heat which raises the particle filtertemperature to the desired temperature.
    The fuel can be supplied to the exhaust gas stream by injection intothe combustion chamber of the internal combustion engine (as usualcylinders), late in the combustion stage inthe combustion cycle, the late injected fuel onlyto a small extent, or not at all, ignites, and at leastmost of the injected fuel is thus suppliedexhaust gas as unburned fuel.
    This method of raising the temperature of the particulate filteralso used for active regeneration.
    The oxidation catalyst can also oxidize a large proportion of those inthe exhaust gas nitrogen nitrogen oxides (NO) tonitrogen dioxide (NO 2). This nitrogen dioxide is also used in passiveregeneration according to the present invention. Even furtherreactions may occur in the oxidation catalyst.
    In the embodiment shown, DOC is 205, DPF 202 and alsoThe SCR catalyst 201 integrated into one and the sameexhaust gas purification unit 203. However, it should be understood that DOC 205 andDPF 202 does not have to be integrated in one and the sameexhaust gas purification unit, but the units may be arranged elsewherewhere appropriate. For example. DOC 205 may be providedcloser to the internal combustion engine 101. Likewise, the SCR catalystbe arranged separately from DPF 202 and / or DOC 205.
    The finishing system set shown in Fig. 2 iscommon in heavy vehicles, at least injurisdictions where stricter emission requirements apply, but whichalternatives to the oxidation catalyst can insteadthe particulate filters comprise precious metal coatings so that they inoxidation catalyst occurring chemical processesinstead occurs in the particulate filter, andthe finishing system thus does not include any DOC.
    As mentioned, soot particles are formed at the internal combustion engine 101combustion. These soot particles should not, and may in many casesnor, are released into the vehicle environment. Diesel particlesconsists of hydrocarbons, carbon (soot) and inorganic substances such assulfur and ash. As mentioned above, these soot particles are trappedtherefore up by the particle filter 202, which works in this waythat the exhaust stream is led through a filter structure theresoot particles are captured from the passing exhaust stream forto then be stored in the particle filter 202. Usingparticulate filter 202 can a very large proportion of the particlesseparated from the exhaust stream.
    As particles are separated from the exhaust stream with the helpof the particle filter 202, the separated ones thus accumulatethe particles in the particle filter 202, this over timefilled with soot. Depending on factors such as currentdriving conditions, the driver's driving style and vehicle load will onegreater or lesser amount of soot particles to be generated, whythis fulfillment happens more or less quickly, but when the filteris met to a certain level, the filter must be "emptied". Ifthe filter is met to too high a level can the vehicleperformance is affected, while also fire hazard, p.g.a.soot accumulation in combination with high temperatures, may occur.
    As above, emptying of particle filter 202 is performed by means ofregeneration where soot particles, carbon particles, in a chemicalprocess is converted to, depending on whether the regeneration is offactive or passive type, carbon dioxide and / or nitric oxide andcarbon monoxide. Thus, over time, the particulate filter 202 must be includedmore or less regular intervals are regenerated, anddetermination of the appropriate time for regeneration ofthe particle filter can e.g. performed using a control unit208, which e.g. can perform determination of appropriatetime / times at least in part by means of signalsfrom a pressure sensor 209, which measures the differential pressure acrossthe particle filter. The more the particle filter 202 fills up, the morehigher, the pressure difference across the particle filter 202 will beVafía.
    Normally no regeneration measures are taken as long asthe fill level of the filter is less than a predetermined level.
    For example. the control system control of the filter regeneration can beso arranged that no action is taken as long as that of the filterdegree of filling e.g. falls below any appropriate degree of filling inrange 60-80%. The degree of filling of the filter can be estimated atany suitable way, e.g. using the differential pressureas above, where a certain pressure difference represents a certaindegree of filling.
    The control unit 208 also controls the regeneration process according topresent invention, which is described in more detail below.l0l5llIn general, steering systems in modern vehicles usually consist of onecommunication bus system consisting of one or morecommunication buses to connect a numberelectronic controllers (ECUs), or controllers, andvarious components located on the vehicle. One suchcontrol systems can comprise a large number of control units, andthe responsibility for a specific function can be divided into several riversa control unit.
    For the sake of simplicity, in Fig. 2 only the control unit 208 is shown,but vehicles of the type shown often include a relativelarge number of control units, e.g. for engine control,gearbox, etc. etc., which year choice for the person skilled in the artthe technical field.
    The present invention can be implemented in the control unit 208.but can also be fully or partially implemented in one or moreother control units present at the vehicle.
    Control units of the type shown are normally arranged to takereceiving sensor signals from different parts of the vehicle, e.g., such asshown in Fig. 2, said pressure sensor 209 and temperature sensors210-212, and also e.g. a motor control unit (not shown). Thecontrol unit-generated control signals are normally also dependentboth of signals from other control units and signals fromcomponents. For example. the control unit 208 can controlthe regeneration of the present invention e.g. depends oninformation such as received from the engine control unit and those inFig. 2 shows the temperature / pressure sensors.
    Control units of the type shown are usually also arrangedto emit control signals to various parts and components ofthe vehicle, in the present example e.g. to the engine control unitto request / order control of the internal combustion enginecombustion as below.12The control is often controlled by programmed instructions. Theseprogrammed instructions typically consist of onecomputer programs, which when executed on a computer orcontrol unit causes the computer / control unit to perform the desired operationcontrol, such as process steps of the present invention.
    The computer program is usually a computer program product109 stored on a digital storage medium 121 (see Fig. 1b)such as: ROM (Read-Only Memory), PROM (ProgrammableRead-Only Memory), EPROM (Erasable PROM), Flash Memory, EEPROM(Electrically Erasable PROM), a hard disk drive, etc., in orin connection with the control unit and which is executed bythe control unit. By changing the instructions of the computer programcan thus the behavior of the vehicle in a specific situationEinpâSSäS.
    An exemplary controller (controller 208) is shown schematically in FIG.1b, wherein the control unit 208 in turn may comprise acalculation unit 120, which may be substantially anysuitable type of processor or microcomputer, e.g. a circuit fordigital signal processing (Digital Signal Processor, DSP),or a circuit with a predetermined specific function(Application Specific Integrated Circuit, ASIC).
    The computing unit 120 is connected to a memory unit 121,which provides the computing unit 120 e.g. the storedprogram code 109 and / or the stored data computing device120 needed to be able to perform calculations.
    The calculation unit 120 is also arranged to store partial orend result of calculations in memory unit 121.
    Furthermore, the control unit 208 is provided with devices 122, 123,124, 125 for receiving and sending input and output, respectivelyoutput signals. These input and output signals can containwaveforms, pulses, or other attributes, which ofthe devices 122, 125 for receiving input signals can13detected as information and can be converted into signals,which can be processed by the computing unit 120.
    These signals are then provided to the computing unit 120.
    The devices 123, 124 for transmitting output signals are providedto convert signals obtained from the computing unit 120 forcreation of output signals by e.g. modulate the signals,which can be transferred to other parts of the vehicle's steering systemand / or the component (s) for which the signals are intended.
    Each of the connections to the receiving devicesrespective transmission of input and output signals can be constitutedof one or more of a cable; a data bus, such as a CAN bus(Controller Area Network bus), and MOST bus (Media OrientatedSystems Transport), or any other bus configuration; orof a wireless connection.
    According to the above, regeneration can take place in mainly two different ways.
    On the one hand, regeneration can take place through so-called oxygen (O2) -basedregeneration, also called active regeneration. When activeregeneration takes place a chemical process mainly according to eq. 1:C + Og = QO2 + heat (eq. 1)Thus, during active regeneration, carbon plus oxygen are converted tocarbon dioxide plus heat. However, this chemical reaction is strongtemperature dependent, and requires relatively highfilter temperatures for that appreciable reaction rateshould occur at all. Typically a minimum is requiredparticle filter temperature of 500 ° C, but preferably shouldthe filter temperature must be even higher for the regeneration tohappen at the desired speed.
    However, the maximum temperature that can be used is often limitedduring active regeneration of tolerances for the constituentsthe components. For example. often has the particle filter 202 and / or(where present) a subsequent SCR catalystdesign constraints with respect to it14maximum temperature to which they may be exposed. This causesthe active regeneration can have a component maximumpermissible temperature which is undesirably low. At the same time, thena very high minimum temperature to anyone usefulreaction rate should occur at all. At the activethe regeneration burns the soot load in the particle filter 202normally substantially complete. That is, a totalregeneration of the particle filter is obtained, after which the soot level inthe particle filter is essentially 0%.
    Today, it is increasingly common for vehicles, in addition to particulate filters202, is also equipped with SCR catalysts 201, so itactive regeneration can cause problems in the form ofoverheating for the subsequent SCRthe catalyst treatment process.At least in part because of this reason applypresent invention, instead of the active ones described aboveregeneration, NO2-based (passive) regeneration. When passiveregeneration is formed, according to eq. 2 below, nitric oxide andcarbon monoxide in a reaction between carbon and nitrogen dioxide:NO2 + C = NO + CO (eq. 2)The advantage of passive regeneration is that desiredreaction rates, and thus the rate at whichthe filter is emptied, achieved at lower temperatures. Typically happensparticle filter regeneration in passive regeneration intemperatures in the range 200 ° C - 500 ° C, although temperaturesin the high part of the range is normally preferable.
    Regardless of this, this is compared to when activeregeneration significantly lower temperature range a largeadvantage in e.g. presence of SCR catalysts, because itthere is no risk of such a hightemperature level is reached, that the risk of the SCR catalystdamaged exists. However, it is still important that onerelatively high temperature is obtained as below, andThe present invention relates to a method of avoidingregeneration in situations when regeneration is not consideredbe carried out effectively.
    Fig. 3 shows an example of regeneration (soot burn-out)the velocity as a function of the amount of soot in the particulate filter 202 andfor operating conditions at two different temperatures (350 ° C and 450 ° C respectively).
    The regeneration rate is also exemplified for low andhigh concentration of nitrogen dioxide. As can be seen in the figure isthe burnout rate was low at low temperature (350 ° C) and lowconcentration of nitrogen dioxide. Regeneration speedtemperature dependence is clear from the fact thatthe burn-out rate is relatively low even at highconcentration of nitrogen dioxide as long as the filter temperatureis low. Burnout rates are significantly higher at 450 ° Ceven in the case of low concentration of nitrogen dioxide prevails, alsoif high levels of nitrogen dioxide are clearly preferred.
    The passive regeneration is, however, in addition to being dependentof the particle filter temperature and soot amount according to Fig. 3, andas shown in Eq. 2 above and Fig. 3, also depending onthe availability of nitrogen dioxide. Normally, however, the proportionnitrogen dioxide (NO2) of the total amount of nitrogen oxides (NOX) whichis generated during the combustion engine combustion only by 0 -% of the total amount of nitrogen oxides. When the internal combustion engineyear heavily loaded, the proportion of NO2 can be as low as 2 - 4%. INpurpose to obtain a rapid regeneration of the particulate filterthere is thus a desire that the proportion of nitrogen dioxide inthe exhaust flow is as high as possible at the onset of the exhaust flowin the particle filter 202.
    Thus, there is also a desire to increase the amountnitrogen dioxide NO2i it from the combustion engine combustionresulting exhaust gas flow. This conversion can be performed onlOl516several different ways, and can be accomplished usingthe oxidation catalyst 205, to which nitric oxide can be oxidizednitrogen dioxide.
    Oxidation of nitric oxide to nitrogen dioxide inhowever, the oxidation catalyst is also a strongtemperature-dependent process, as exemplified in Fig. 4.
    As can be seen in the figure, at favorable temperatures,the proportion of nitrogen dioxide in the total amount of nitrogen oxides inthe exhaust gas flow is increased to up to 609. As can also be seen inthe figure, it would thus be optimal with a temperature inon the order of 250 ° C - 350 ° C in the case of passive regenerationto obtain such a high oxidation of nitric oxide tonitrogen dioxide as possible.
    As described in connection with Eq. 2 and Fig. 3however, a completely different temperature ratio applies to themselvesthe burnout process. This temperature ratio is shown withdashed line in Fig. 4, and which can be seen isthe reaction rate is virtually non-existent at temperaturesbelow a particle filter temperature of 200-250 °. It willhowever, it is understood that the temperature indications shown only constituteexamples, and that fair values may differ from these. For example.can be the way in which the temperatures are determined / calculatedimpact on temperature limits. Some are exemplified belowway to determine the temperature of the filter.
    If free supply of nitrogen dioxide prevails, one would thus be so highfilter temperature as possible be preferred. As well as canseen in Fig. 4, however, this leads to low oxidation of nitric oxideto nitrogen dioxide. This in turn means regenerationwill not be able to take full advantage of the highthe filter temperature, as the reaction will be limited bylack of nitrogen dioxide. Still applies, however, according to itdashed line in Fig. 4, that the particle filter must reach17at least a minimum temperature for regeneration to be possibletake place within a reasonable time. For this reason, it is also used according toabove temperature raising measures to raise the particulate filtertemperature.
    The temperature raising measures can be accomplished bycontrol the internal combustion engine in such a way that a pileexhaust gas temperature is obtained, which is achieved by loweringengine efficiency to a low level, so that a large part ofthe energy is converted into heat. Although this type of heat-raisingmeasures are often sufficient in regeneration duringoperation, there are, as mentioned above, situations / operating caseswhere regeneration during travel cannot be performed efficientlymethod and, wherein the so-called parked regeneration, ie. regenerationwith the vehicle stationary, therefore must be performed.
    When regenerating with a stationary vehicle, it will not beresulting exhaust temperature high enough to be desiredregeneration speed should be obtainable only with the help ofcontrol the efficiency of the internal combustion engine even at passiveregeneration, but to be able to raise the particulate filtertemperature to the desired temperature, fuel must be addedthe exhaust gas stream which then generates heat during oxidation inthe oxidation catalyst.
    Injection of fuel into the exhaust stream can take place on severalway. For example. injection can be done with the help of an injector inthe exhaust system, such as in an exhaust pipe. Alternatively, fuel caninjected into the combustion chamber of the internal combustion engine.
    The present invention is applicable in any manner thatadd unburned fuel to the exhaust stream. Suchfuel injection is described in the prior art.
    When fuel is injected into the cylinder, it is injected under highprint. In order for the fuel to follow the exhaust stream unburnedthe fuel must be injected late during combustion, which18means that a relatively large part of the cylinder wall isexposed (the piston is far down in the cylinder). Thismeans that the high pressure injected fuel willhit the cylinder walls and flush it off atcylinder walls existing oil film. The cylinder walls inthe cylinders of the internal combustion engine shall normally be provided with afine oil film for lubrication of the cylinder piston up anddownward movements in the cylinder to thereby reducewear. Rinsing off this oil film, also called"Wall wetting" thus reduces the lubricity with the risk ofwear as a result. This problem can be reduced by atregeneration according to the present invention control injectionaccording to the l the parallel application "PROCEDURE AND SYSTEM FOREXHAUST CLEANING III ", with the same applicant and inventor aspresent application, described the solution there instead ofadd fuel to each combustion, such as e.g. eachcombustion rate of a four-stroke / diesel engine, largeramounts of fuel are injected during fewer incinerations. For example. candouble the amount of fuel injected at every other combustion(combustion rate), triple amount for every third combustion(combustion rate) etc.
    Supply of unburned fuel to the exhaust stream forheating of a particulate filter during passive regeneration hasalso an additional disadvantage. As above, oxidation ofunburned fuel NO2 formation in the oxidation catalyst ona negative way because the oxidation catalyst in the firsthand will perform oxidation of HC (fuel), and first insecondly, if capacity remains, form N02. Since N02-the formation is markedly reduced, or t.o.m. disappears completely atoxidation of fuel thus also disappears an importantparameter for regeneration according to eq. 2 above.19When parked passive regeneration should be supplied with fuelto the exhaust gas flow continuously, to the desiredtemperature must be able to be maintained, which therefore entailsproblems for NO2 formation as above.
    At the same time, in the case of parked regeneration, it is desirable thatthe regeneration goes as fast as possible so that the vehicle thencan return to normal operation. According to the presentinvention provides a method in which it is parkedthe regeneration follows a regeneration profile below onepredetermined time. This can ensure thatregeneration actually takes place in the desired and expectedextent. According to the present invention, a pile is obtainedregeneration rate in passive regeneration by aoperating point which gives a high NO 2 flow into the particulate filterdespite the supply of unburned fuel to the exhaust streamis set.
    An exemplary method 500 of the present invention is shownin Fig. 5.
    The procedure begins in step 501, where it is determined whether to parkregeneration should be performed. This determination can e.g. performedas above by determining the differential pressure abovethe particulate filter exceeds a certain level. Alternatively canthe determination e.g. triggered by the conditions forregeneration while traveling are not met, and / or that anumber of regeneration attempts have been performed without success.
    When parked regeneration is to be performed, the procedure continuesto step 502.
    To achieve a desired regeneration speed when parkedpassive regeneration must be supplied with unburned fuelthe exhaust gas flow to the desired particle filter temperatureobtained. The unburned fuel is oxidized according to whatl0l5described above whereby heat for heating ofthe particle filter is formed.
    As also described above, oxidation offuel in the oxidation catalyst negative on the formation ofnitrogen dioxide. In order to obtain a high NO2 flow, it mustduring combustion, a high proportion of NOX is created at the same time asthe exhaust mass flow is high. However, a high mass flow means thatthe oxidation catalyst, seen from the point of view of the exhaust stream becomes"Less" with the consequence that the NO2 conversion decreases, ie. NO2-the conversion in the oxidation catalyst decreases with the flow whenunburned fuel is simultaneously supplied with the exhaust gas stream.
    If the exhaust gas mass flow is low, the catalyst will appearthe point of view of the exhaust stream, instead of appearing larger becauseavailable catalyst capacity is then large in relation tothe exhaust gas mass flow. When, however, the mass flow is high comesthe oxidation catalyst to be fully engaged in oxidationof unburned fuel because this process takes place beforeconversion of nitric oxide to nitrogen dioxide. At high mass flowthe resources of the oxidation catalyst can be completely devoted to oxidationof fuel, leaving no resources for the conversion ofnitric oxide to nitrogen dioxide.
    To obtain as fast a regeneration as possiblethus it is important that the exhaust gas mass flow is set to a flowwhich is as high as possible for regeneration to go as fastas possible while the flow is low enough tothe conversion of NO to NO2 in the presence of unburned fuelin the exhaust gas flow must take place to the desired extent.
    Thus, the exhaust gas mass flow comes from a regeneration point of viewconstitutes a favorable flow due to the oxidation catalystsize. The larger the oxidation catalyst, the largerexhaust mass flow can be set without too negative an effect onconversion of NO to NO2. When parked regeneration can21control of the exhaust flow takes place with greater freedom, which is why it isit is desirable that the exhaust gas mass flow is set in such an optimal wayas possible.
    In step 502, therefore, the desired exhaust mass flow is determined. This flowcan e.g. be determined in advance and be stored invehicle control system. Determination of flow can e.g.achieved by testing the catalyst at differentexhaust gas mass flows with simultaneous supply of unburned fuel,wherein the resulting NO 2 conversion can be determined fordifferent flows, and optimal flow, ie. it flowed therethe regeneration rate is highest, thus determined. At the same timethe pressure and the temperature at which it is applied are determinedthe combustion supplied air has at optimum flow. Alsothese values are stored in the control system.
    The value determined in step 502 is then used as the setpointat the parked regeneration.Even if the internal combustion engine is controlled in an identical way (iehowever, the same engine speed, fuel injection, etc.)this is not that the exhaust mass flow automatically always becomesthe same. The reason for this is that the exhaust gas mass flow,in addition to engine control parameters, also to a large extentdepends on the temperature of the air supplied to the combustion,as well as prevailing air pressure. For example. the air enters the vehicleenvironment, and thus the air supplied to the vehiclecombustion, to have a lower density on a hot summer daycompared to a cold winter day. This means that at the sameengine speed, the exhaust mass flow will be lower in summercompared to in winter. The same situation appliesair pressure, where a low air pressure results in lowerexhaust mass flow.22For example, if it is a hot summer day, a temperature prevails+ 30 ° C the difference (flow reduction) comes towards a coldwinter day when it is -20 ° C to be:273.1s + (_20) ~OÅ4 (eq. 3)27l15 + 30Ie. on a hot summer day, the exhaust mass flow is only about 84% offlow on a cold winter day at the same engine control.
    Correspondingly, the exhaust gas mass flow comes on a day with lowair pressure, e.g. 700 millibars to be proportionally smallerthan the exhaust gas mass flow at e.g. 1000 millibars air pressure according to:E = 0.70(Eq. 4)1000Both individually but above all in total havethus the current pressure and temperature of the air thatthe combustion is given a very large impact on itresulting exhaust mass flow.
    The exhaust mass flow can differ by 40% or moreenvironmental conditions, where regeneration can take place atarbitrary ambient conditions.
    Thus, it is not likely that the engine control parameterswhich prevailed in determining the optimal exhaust mass flow forthe oxidation catalyst also results in optimalexhaust gas mass flow at the ambient conditions prevailing whenregeneration is actually performed.
    Therefore, according to the present invention, in step 503, arepresentation of prevailing air temperature and prevailingair pressure, the process proceeding to step 504, whereapplicable motor control parameters are determined based on the desiredexhaust gas mass flow and prevailing temperature and pressure.
    The representation of the air pressure and temperature can e.g.determined by means of temperature sensorslOl523and pressure in the vehicle environment. Alternatively canthe representation of the air pressure and temperature e.g.determined using sensors that measure temperature and pressureat or upstream of the internal combustion engine air intake. For example. canrepresentation of temperature and pressure for it tothe combustion air supplied is determined by means of sensorsarranged upstream of turbochargers or othersupercharger for pressurizing the air thatis added to the combustion.
    According to the present invention, therefore, the internal combustion engine is controlledwith air pressure and temperature as input parameters. In aembodiment, an algorithm is used to base it onpredetermined exhaust mass flow at the prevailing air pressure andtemperature calculate the appropriate parameters to obtaincorresponding exhaust gas mass flow at the air pressure and thetemperature determined in step 503.
    In one embodiment, engine control data can be stored for a quantitydifferent air pressures and / or temperatures, whereby the vehicle'scontrol system using e.g. table lookup can determineappropriate motor control parameters as desiredexhaust gas mass flow must be obtained during regeneration.
    It emitted at constant temperature and pressure conditionsthe exhaust gas mass flow depends on the speed, at least in itcase injection angles etc. are the same, regulation ofthe exhaust gas mass flow can take place by varying the internal combustion enginespeed depending on prevailing pressure and temperature.
    The process then proceeds to step 505 therethe combustion engine speed is controlled according to that in step 504determined value so that regeneration is performed with the desiredspeed. The speed can e.g. determined by means of arelationship between speed and flow that describes how the flowchanges with speed. This representation can e.g. be inlOl524tabular form or in the form of a mathematical expression. At the same timeas the procedure proceeds to step 505, a timer t is started.
    Thus, the present invention provides that regeneration canperformed with the same result regardless of ambient conditions.
    Ie. by controlling the exhaust gas mass flow, it can be ensured thatregeneration takes the same amount of time regardless of ambient pressureand / or temperature. Thus, it can also in regenerationensure that regeneration actually takes place in the desiredextent. When the timer t has reached a time T, at whichregeneration is considered completed, regeneration is terminated instep 506.
    The actual exhaust gas mass flow can also be determined with the help of aair mass sensor for determining the air flow, this flowadded with the fuel flow (exhaust mass flow = air flow +fuel flow), where the fuel flow can be calculated with knowledge ofthe amount of fuel injected during combustion. Determination ofair flow can also take place e.g. using a model based onfor example charge pressure, charge temperature, speed in known manner. Thisdetermined flow can then be used to controlthe internal combustion engine to achieve the desired exhaust mass flow.
    In some cases, it may also be desirable to steerthe exhaust gas mass flow against a flow where one compared to the maximumregeneration speed lower regeneration speed is obtained.
    Injection of unburned fuel can take place independently of itfuel supplied for the actual combustion. Thoughthe exhaust mass flow will depend on the amount of air suppliedthe combustion, why control of the actual combustionis limited to control towards operating points where the desired flowcan be delivered. However, it may be possible to with the help ofinjection times (angles) affect the amount of nitrogen oxidesemitted during combustion. In one embodiment, therefore, controlthe combustion engine combustion in such a way that one solOas high a percentage of nitrogen oxides as possible is released at the same time as desiredflow is maintained. General grating according to prior art thatemission of a higher proportion of nitrogen oxides means thatthe internal combustion engine is steered towards a higher efficiency.
    The most advantageous flow during regeneration can e.g. alsodepend on the amount of unburned fuel suppliedthe exhaust gas flow, so in one embodiment different setpointsused depending on the amount of fuel suppliedthe exhaust gas flow. The setpoint can thus be arranged to varyduring ongoing regeneration.
    Furthermore, the present invention has been exemplified above inconnection to vehicles. However, the invention is also applicablefor arbitrary vessels where exhaust gas purification systems as aboveare applicable, such as e.g. water or aircraft withcombustion / regeneration processes as above. In that caseThe present invention is implemented in other types ofvehicles than vehicles can some of the exemplifiedthe procedure steps are omitted, such as e.g. determination of avehicle speed.
    权利要求:
    Claims (14)
    [1]
    A method of regenerating a particulate filter (202) in a post-treatment system (200), said particulate filter (202) being arranged to treat an exhaust gas mass flow emitted at a combustion in an internal combustion engine (101), wherein air is supplied to said combustion, said method comprises the steps of: - determining a representation of a temperature of the air supplied to the combustion, - determining a representation of a pressure of the air supplied to the combustion, and - based on said representations of temperature and pressure of said air supplied to said combustion , controlling said internal combustion engine (101) so that the magnitude of the exhaust gas mass flow emitted during combustion substantially corresponds to a first value.
    [2]
    A method according to claim 1, wherein said internal combustion engine (101) is controlled so that the magnitude of the exhaust gas mass flow emitted during combustion substantially corresponds to a first value at least in part by controlling the speed of said internal combustion engine (101).
    [3]
    A method according to any one of claims 1 or 2, wherein said representation of a temperature and a pressure for the air supplied to the combustion consists of a representation of the ambient air temperature and air pressure.
    [4]
    A method according to any one of claims 1 or 2, wherein said representation of temperature and pressure for the air supplied to the combustion is a representation of temperature and pressure upstream of a turbocharger (220) or other supercharger for pressurizing the air supplied to the combustion. 10 15 20 25 30 27
    [5]
    A method according to any one of claims 1-4, wherein said finishing system (200) constitutes a finishing system (200) at a vehicle (100), said method being performed at a stationary vehicle (100).
    [6]
    A method according to any one of claims 1-5, wherein, in said regeneration, unburned fuel is supplied to said exhaust gas mass stream emitted at said combustion.
    [7]
    A method according to any one of the preceding claims, wherein said finishing system is a finishing system (200) at a vehicle (100), said first value being determined before traveling with said vehicle (100).
    [8]
    A method according to any one of the preceding claims, wherein said method is performed when the degree of filling of the particle filter exceeds a first level.
    [9]
    A method according to any one of the preceding claims, wherein said regeneration method is a method for passively regenerating said particle filter (202).
    [10]
    A method according to any one of the preceding claims, wherein said method comprises setting the speed of said internal combustion engine (101) so that the magnitude of the exhaust gas mass flow emitted during combustion substantially corresponds to a first value during a first time.
    [11]
    A process according to any one of the preceding claims, wherein said after-treatment system (200) comprises an oxidation catalyst (205) arranged upstream of said particulate filter (202), said fuel supplied to said after-treatment system being at least partially oxidized in said oxidation catalyst (205).
    [12]
    A method according to any one of the preceding claims, wherein when setting the speed of said internal combustion engine (101), the speed is set by means of a representation of the variation of the flow with the speed.
    [13]
    A system for regenerating a particulate filter (202) in a post-treatment system (200), said particulate filter (202) being arranged to treat an exhaust gas mass flow emitted at a combustion in an internal combustion engine (101), wherein air is supplied to said combustion, said system comprises means for: - determining a representation of a temperature of the air supplied to the combustion, - determining a representation of a pressure of the air supplied to the combustion, and - controlling said internal combustion engine (101) so that the magnitude of the emitted during combustion the exhaust gas mass flow substantially corresponds to a first value based on said representations of temperature and pressure for said air supplied to said combustion.
    [14]
    Vehicle (100), characterized in that it comprises a system according to claim 13.
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    同族专利:
    公开号 | 公开日
    WO2012030274A1|2012-03-08|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1050890A|SE535802C2|2010-08-31|2010-08-31|Process and system for regenerating a particulate filter for exhaust gas purification|SE1050890A| SE535802C2|2010-08-31|2010-08-31|Process and system for regenerating a particulate filter for exhaust gas purification|
    PCT/SE2011/051009| WO2012030274A1|2010-08-31|2011-08-23|Method and system for controlling the mass flow during regeneration of a particle filter in a post-treatment system of a combustion engine|
    EP11822209.0A| EP2611998B1|2010-08-31|2011-08-23|Method and system for controlling the mass flow during regeneration of a particle filter in a post-treatment system of a combustion engine|
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