The present, invention pertains to combustion engines, and. in particular to a method for the control of a combustion engine according to the preamble of claim 1. The invention also relates to a system and a vehicle, as well as a computer program and. a computer program product, which implement t e method according to the invention.

Background of the invention

The background description below constitutes a background description for the invention, and thus need not necessarily constitute prior art techno1ogy .

In connection with increased government interests concerning pollution and air quality, emission standards and regulations regarding emissions from combustion engines have been, drafted in man urisdict ions .

Such emission regulations often consist of requirements defining acceptable limits for exhaust emissions in vehicles equipped with combustion engines. For example, levels of nitrogen oxides (N0 _X ) , hydrocarbons (HC) and carbon monoxide (CO) are often regulated. These emission regulations may also handle the occurrence of particles in exhaust emissions.

In an effort to comply with these emission regulations, the exhausts caused by the combustion of the combustion engine are treated (purified) , By way of example, a so-called catalytic purification process may be used, so that exhaust treatment systems in e.g. vehicles and other vessels usually comprise one or more catalysts and/or other components . For example, the exhaust treatment systems in vehicles with diesel engines often comprise particu1ate filters. Catalysts at combustion engines may be of several different types, where different types may be required for different fuels and/or conversion of different unwanted

substances /compounds occurring in the exhaust stream. In relation to at least nitrous gases (nitrogen rn.onoxi.de, nitrogen dioxide) , referred to below as nitrogen oxides N0 _X , heavy goods vehicles often comprise a catalyst where an additive is supplied to the exhaust stream resulting from the combustion in the combustion engine, in order to reduce nitrogen oxides N0 _X , primarily to nitrogen gas and aqueous vapour .

This reduction of emissions of nitrogen oxides from diesel engines is usually carried out through a method called SCR (Selective Catalytic Reduction) . This method entails that an additive, usually an aqueous solution comprising the substance urea, is supplied in a suitable dose to the exhaust stream upstream of an SCR catalyst .

The SCR catalyst ' s function usually requires access to ammonia ( H-j) , and at e.g. the evaporation of urea ammonia is also formed, so that ammonia subsequently reacts with nitrogen oxides in the exhaust stream in the SCR catalyst, with a conversion into nitrogen gas and aqueous vapour as a result .

Surrsmary of the invention

One objective of the present invention is to provide a method to control a combustion engine . This objective is achieved with a method according to claim 1.

The present invention pertains to a method for the control of a combustion engine, where said combustion engine comprises at least one combustion chamber and elements for the supply of fuel to said combustion chamber, wherein the combustion in said combustion chamber occurs in combustion cycles. The method is characterised in:

- determining, during a first combustion cycle and with the use of a first sensor element, a first parameter value

representing a quantity with respect to said combustion chamber,

- determining, with the use of said, first, parameter value, a first amount of additive for supply to said combustion

chamber, and - supplying said first amount, of additive to said combustion chamber .

Said additive may e.g. consists of an additive for the

reduction of nitrogen oxides resulting during- combustion in. said combustion chamber. During combustion in combustion engines, in particular diesel engines, unwanted nitrogen oxides ISIOx are generated, at least partly due to the excess oxygen, which is generally applied at combustion in diesel engines. Alternatively, the additive may be intended to reduce another substance/compound resulting during combustion.

Substances/compounds are referred to below only with the use of the term "substance", which is thus deemed to comprise chemical compounds , compositions and substances.

As mentioned, due to for example government regulations some type of treatment of the exhaust stream is often required, with the objective to reduce the amount, of nitrogen oxides in the exhaust stream, before the exhaust stream is released into the vehicle's environment, wherein such reduction of emissions may be carried out by injecting- additives in a suitable dose into the exhaust stream upstream, of an SCR catalyst. The additive then evaporates on contact with the ot exhausts, whereby ammonia is created/released in order to subsequently reduce nitrogen oxides in the exhausts to nitrogen gas and aqueous vapour in the SCR catalyst, .

The additive may be supplied with the help of an injection system, comprising one or seve al nozzles for injection of the additive into the exhaust stream. With the correct dosage of additive, the emission of nitrogen oxides may be reduced to a great extent .

However, the desired function at injection of additive is dependent on the exhausts keeping a sufficiently high

temperature, in order for the additive to evaporate. During large parts of a diesel engine ' s operating mode, the exhausts usually do maintain a sufficiently high temperature for t e desired evaporation to occur.

However, there are situations where this may not be guaranteed and it may be difficult, at least, during some operating mod.es, to avoid that some of the injected additives, e.g. a

urea/aqueous solution, comes into contact with wall surfaces of e.g. one or several of exhaust pipes, catalysts, silencers while in a non-evaporated, condition. In such situations, urea/urea-based compounds may attach to wall surfaces in the exhaust system.

If the formation of solid, formations is greater than the evaporation of the coating formed, a successive build-up of deposits will occur. In unfavourable conditions, the result may be a significant build-up of solid material. Such, build ^¬ ups may grow so large that, the combustion engine ' s performance is impacted, since the exhaust stream in the exhaust system is impacted (throttled) , and in case of a large build-up of the deposit, the continued operation of the engine may in extreme cases be completely prevented.. The deposit may also damage components in the after-treatment system., if the formations created, e.g. in the form of lumps, are released from the location where they were formed and. then carried along the exhaust stream to e.g. a subsequent SCR catalyst or other components. The formation of the deposit may also entail a reduced exhaust purification function.

According to the present invention, such problems with deposit formation may be reduced. Similarly, the need for SCR

catalysts may be reduced or completely eliminated.

Addi.tiona.lly, the use of additive may be adapted to the prevailing requirements, so that an exaggerated supply of additive, and associated costs, may be reduced.

According to the invention, additive is injected directly into the combustion engine's combustion chamber. This may be achieved e.g. by using an injection element arranged in direct connection with the combustion chamber, wherein the injection of additive may be carried out after the inlet for supply of the combustion gas has been closed. The temperature in the combustion chamber is, at least during the combustion of fuel, substantially higher than in e.g. the SCR catalyst, where the exhaust stream is successively cooled down when passing through the exhaust pipe, among others as the exhaust, pipe usually is cooled by the surrounding air. The SCR catalyst is, among other things, required because of this cooling down, since otherwise the reaction rate during the reduction of N0 _X with the use of the additive would be too low for the desired, reduction to be carried out before the exhaust stream is released into the vehicle's environment.

In the combustion engine's combustion chamber, on the other hand, the temperature is usually so high that the wanted reaction rate may be achieved without a catalyst, and by injecting additive directly into the combustion chamber a. very high reaction rate may be obtained at the reduction, of the resulting nitrogen oxides, as the exhaust temperature is still high.

According to one preferred embodimen of the present

invention., the nitrogen oxides resulting during combustion are estimated, so that a suitable amount of additive may be injected as a function of the estimated amount of resulting nitrogen oxides. The estimation may e.g. be carried out during a. combustion cycle, wherein the amount of injected additive in subsequent combustion cycles may be controlled, based on said estimated amount of nitrogen oxides.

When the applicable amount of additives for injection is determined, t e known chemical ratios during the reaction between the additive and nitrogen oxides may be applied, to determine the applicable amount of additive for supply to the combustion chamber. At this determination, the combustion chamber's temperature may also be estimated, e.g. with the use of said first parameter value, wherein the amount of additives may e.g. depend on the expected reaction rate.

According to one embodiment, a part of the required additive may be arranged to be injected into the combustion chamber, while another part may be injected conventionally downstream of the combustion engine, wherein one part of the reduction may be carried out in the combustion chamber and one part may be carried out in e.g. an SCR catalyst. According to one embodiment, no external injector arranged in the exhaust pipe is required for the supply of additive, but instead additive is supplied via the combustion engine's combustion chamber, for transport to e.g. a catalyst such as an SCR catalyst.

Additives supplied to the combustion chamber according to this embodiment may thus be used partly for reduction in the combustion chamber and partly for reduction in a subsequent catalyst, or for use in a subsequent catalyst only. Further, the estimation of the amount of nitrogen oxides resulting during combustion may e.g. be arranged to be carried out at applicable points in time, such as every time a significant change of the combustion occurs, e.g. a change of the injected amount of fuel. For example, the estimation may be carried out during one or a suitable number of combustion cycles, so that the injection of additive may subsequently be carried out based on said estimation, e.g. as long as the conditions remain the same or substantially the same. According to one embodiment, the amount of resulting nitrogen oxides are estimated for each combustion cycle and during the ongoing combustion cycle, whereby the supply of additive during each combustion cycle may be adapted to the ongoing combustion cycle's combustion during the ongoing combustion cycle, and may also be injected during the ongoing combustion c cle ,

According to a preferred embodiment of the present invention, the supply of additive is carried out at an early stage during the combustion cycle. For example, the supply of additive may be arranged to be carried out completely or partly before the combustion of fuel is initiated or ended, e.g. completely or partly before the fuel injection is initiated or ended. The injection of additive may also be arranged to be carried out completely or partly before the maximum pressure and/or temperature has been achieved during the combustion cycle.

According to one embodiment, the supply of additives is carried out, or at least initiated, before the piston in a piston engine has reached the top dead centre. According to one embodiment, the supply of additive is carried out at least partly after the combustion engine's one or several inlet valves for intake of combustion gas have been closed. Further, the supply of additives may be arranged to be carried out only when the temperature in the combustion chamber fulfils some applicable condition. For example, the supply may be arranged to be carried out only once a certain temperature has been reached in the combustion chamber. Further, the supply may be arranged to be carried out only if the

combustion chamber's temperature drops below some applicable temperature. If the combustion chamber's temperature is too high, there may be a risk that the additive supplied is oxidised, with the consequence that the amount of said first substance generated at combustion, e.g. the amount of nitrogen oxides, may be greater than what was the case without the supply of an additive. Further, temperature limits, and/or the amount of additive for supply, may at the supply of additive be arranged to e.g. depend on the prevailing air/fuel ratio. The greater the prevailing air excess, i.e. the higher the prevailing lambda value, the more the risk of oxidation of the additive decreases. Thus, a higher combustion chamber

temperature may be permitted during combustion with a first higher lambda value, compared to combustion at a second, lambda value, which is lower when compared to said first lambda value.

The supply of additive may also be arranged to depend on the prevailing combustion engine load, where supply before/during combustion may e.g. be arranged to be carried out only up to a certain combustion engine load, with the objective to avoid that additive is supplied at too high temperatures. Thus, the supply of additive before combustion may benefit from the lower temperatures generally arising at lower loads.

According to one embodiment , the impact on the supply by a first amount of additive, regardless of whether this is supplied early or late during the combustion cycle, may be q estimated before the supply is actually carried out, so that the designed/intended araount of additive for supply may be corrected based on the expected impact before the supply is actually carried out, e.g. with respect to the generated amount of said first substance .

Thus, a first measure of said at least one first substance, resulting at combustion during a first combustion cycle, may be estimated, so that a first amount of additive may be determined for supply to said combustion chamber, and so that a second measure of said at least one first substance, consisting of the expected resulting amount of said first substance at the supply of said first amount of additives, may be estimated before the supply is actually carried out, and so that said first amount of additive for supply to said

combustion chamber may be corrected based on said second measure .

Further, the measure of said at least one first substance may be estimated iteratively, and said first amount of additives may be corrected iteratively based on determined measures, until a measure of said at least one first substance e.g.

fulfils a first condition.

Likewise, the combustion chamber ' s expected temperature development may be estimated, so that the supply of additive may be controlled based on the expected temperature

development .

According to one embodiment , the generated amount of said first substance is estimated during a first combustion cycle, so that the additive is supplied only during a subsequent second combustion cycle, wherein the supply may be carried out before/during/after the combustion according to the above, during said subsequent second combustion cycle. Actual parameters, such as actually measured cylinder pressure for a 1C combustion cycle where the supply has been carried out, may thus be used to estimate the amount generated of said first substance, and thus to determine the applicable amount for a subsequent combustion cycle, so that the additive e.g. may be supplied before the combustion during said subsequent

combustion cycle. A new estimation of the generated amount of said substance during said subsequent second combustion cycle may then be carried out, so that the amount of additives may again be adapted based on this estimation for another

subsequent third combustion cycle, and so that the supply of additive may thus be controlled on a cycle-by-cycle basis. This may be particularly advantageous when the injection of additives occurs early during the combustion cycle according to the above.

According to one embodiment, signals from an O _x sensor, arranged downstream of the combustion engine, are applied at the determination of the applicable amount of additive for supply to the combustion chamber. In this case, e.g. an undesirably high NO _x level indicated by the NOx sensor may entail an increase of the amount of reductant supplied.

According to one embodiment, the temperature prevailing in the combustion chamber is also estimated/used, so that the

injection of additive may e.g. be arranged to be carried out only if the combustion chamber's temperature exceeds some applicable temperature. This has the advantage that unwanted deposit formations in/downstream of the combustion chamber, and caused by the additive, may to a great extent be avoided.

According to one embodiment of the invention, an extra fuel injection is carried out before or at the same time as the injection of additive, so that the temperature in the

combustion chamber may be increased through the use of the extra fuel injection, in order to thus facilitate desired chemical reactions.

According to one embodiment of the invention, the invention is combined with regulation of the combustion engine's combustion during an ongoing combustion cycle, wherein the combustion may be regulated towards one applicable criterion out of several such as one or several of : resulting nitrogen oxides,

combustion tem.perat.ure, pressure amplitude and/or pressure change rate, heat losses, work generated at combustion. The injection of additive may also be arranged to be carried out. individua11y for each cylinder, i.e. resu 1ting itrogen oxides may be determined individually for each combustion chamber, so that the injection of additive may be adapted individually for each combustion chamber. The invention thus facilitates enables a regulation, where e.g. differences between different cylinders may be detected and nitrogen oxide variations may be compensated with the use of individual adjustment of the injected amount of additive for each combustion chamber. It. may also be the case that injection of different amounts of additive in different combustion chambers may be desirable, e.g. in order to control certain cylinders towards the fulfilment of some criterion, and other cylinders towards some other applicable criterion, which may also be achieved according to the invention.

Further, only one or some of the cylinders may be arranged to be controlled according to the invention, while combustion in the remaining cylinders may be carried out in a customary or other applicable manner.

The method according to the present invention may e.g. be implemented with the use of one or several FPGA (Field- Programmable Gate Array) circuits, and/or one or several ASICs (App ication-Specific Integrated Circuit), or other types of circuits which may handle the desired calculation speed.

Further characteristics of the present invention and

advantages thereof will be described in the detailed

description of example embodiments set out below and in the enclosed drawings .

Brief description of drawings

Fig. 1A schematically shows a vehicle, in which the present i vention may be used.

Fig. IB shows a control device in the control system for the vehicle shown in Fig. 1A.

Fig. 2 shows the after-treatment system for the vehicle

displayed in Fig. 1 in more detail.

Fig. 3 snows an example of a dosage system for the supply of additives to the exhaust stream.

Fig. 4 shows the combustion engine in the vehicle shown in

Fig. 1A in more detail.

Fig. 5 shows an example method according to the present

invention .

Fig, 6 shows an example of a temperature track, nitrogen oxide change and heat release for a combustion.

Fig. 7 shows an example of a pressure track in a combustion chamber, where injection of additives is carried out before the combustion.

Detailed description of embodiments

Fig. 1A schematically shows a dxiveline in a vehicle 100, according to an embodiment of the present invention. The driveline comprises one combustion engine 101, which in a customary manner, via an output shaft on the combustion engine 101, usually via a flywheel 1.02, is connected to a gearbox 103 via a clutch 106.

The combustion engine 101 is controlled by the engine's control system via a control device 1.15. Likewise, the clutch 106, which may consist of e.g. an automatically controlled clutch, as well as the gearbox 103, are controlled by the vehicle's control system with the help of one or several applicable control devices (not shown) . Naturally, the

vehicle's driveline may also be of another type, such as a type with a conventional automatic gearbox, or a type with a manual gearbox, etc.

An output, shaft 1.0 from, the gearbox 103 operates the driving wheels 113, 114 in a customary manner via the end gear and driving shafts 104, 105. Fig. 1A shows only one shaft with driving wheels 11.3, 1.14, but in. a customary manner the vehicle may comprise more than one shaft equipped, with driving wheels, or one or more extra shafts, such as one or more support shafts. The vehicle 100 also comprises an exhaust system with an after-treatment system 200 for customary treatment

(purification) of exhaust emissions resultinq from combustion in the combustion chamber (e.q. cylinders) of the combustion engine 101.

The after-treatment system is displayed in more detail in Fig. 2. The figure shows the combustion engine 101 of the vehicle 100, which consists of an engine with turbo, which is why the exhaust generated by the combustion, (the exhaust stream) is led via a. turbocharger 220. Alternatively, the turbocharger may e.g. be of compound type. The function of various types of turbocnargers is well-known, and is therefore not described in any detai 1 here in .

The exhaust stream is subsequently led via a pipe 204

(indicated by arrows) to a diesel particulate filter (DPF) 202, via a diesel oxidation catalyst (DOC) 205. During the combustion in the combustion engine, soot particles are formed, and the particulate filter 202 is used to catch these soot particles. The exhaust stream is led through a filter structure where soot particles are caught from, the ex aust stream passing through, and are stored in the particulate filter.

The oxidation catalyst DOC 205 has several functions, and. is normally primarily used in the after treatment to oxidise remaining hydrocarbons and carbon monoxide in the exhaust stream into carbon dioxide and water. The oxidation catalyst 205 may also oxidise a large fraction of the nitrogen

monoxides (NO) occurring in the exhaust stream, into nitrogen dioxide (NO ₂ ) . Oxidisation of nitrogen monoxide NO into nitrogen dioxide NO ₂ is advantageous at the reduction of nitrogen oxides NO _x . As mentioned above, an SCR (Selective Catalytic Reduction) catalyst 201 is usually used with this objective, using ammonia (NH ₃ ) , or a composition from which ammonia may be generated/formed, e.g. urea, as an additive for the reduction of nitrogen oxides NO _x in the exhaust stream. The efficiency of this reduction is impacted, however, by the ratio between NO and NO? in the exhaust stream, so that the reduction reaction is impacted in a positive direction by the previous oxidation of NO into NO ₂ .

Regarding the present invention, the after-treatment system may generally be of a different type, and does not need to e.g. comprise a particulate filter 202 or oxidation catalyst 205. According to a preferred embodiment , no SC catalyst is required, since the reduction of nitrogen oxides may be carried out entirely in the combustion engine's combustion chamber. The after-treatment system may also comprise

a.d.ditiona.1 non-disp1.a.yed components . The SCR catalyst thus requires an additive to reduce the concentration of nitrogen oxides in exhausts. This additive is often urea-based and may consist of e.g. the product AdBlue, which basically consists of urea diluted with water.

One example of a conventional system for supply of addit displayed in more detail in Fig-. 3, where of the above

components only t e particulate filter 202 and the SCR

catalyst 201 are displayed, and where the system, apart from said catalyst 201, comprises a urea tank 302 connected to a urea dosage system (UDS) 303.

The urea dosage system 303 comprises, or is controlled by, an UDS control device 304 generating control signals for control of the supply of additive, so that the desired amount is injected from the urea tank 302 into the exhaust stream resulting from the combustion in the cylinders of the

combustion engine 101, with the help of an injection nozzle 305 upstream of the SCR catalyst 201, Fig. 3 also shows an NO _K sensor 308 arranged downstream of the SCR catalyst 201,

The more specific functions of urea dosage systems are well described in prior art technology, and the exact method for the injection of additives is therefore not described in any further detail herein. Generally, however, the temperature at the injection point/SCR catalyst 201 should be at least 200- 250 °C, preferably over 300 °C, in order for the desired

reaction rates to be obtained, and thus the desired reduction of said first compound, such as one or several types of nitrogen oxides .

According to the above, however, such systems are associated with certain disadvantages . If e.g. the temperature at the position in the after-treatment system where the supply of additive occurs is too low, there is a risk that urea injected with the injection nozzle 305, instead of directly evaporating as a result of the passing exhaust stream, encounters

relatively low temperature pipe walls, causing the additive to attach and begin to build up crystals. As long as the vehicle is driven with varying and periodically higher load with associated increases of temperature in the after-treatment system, this build-up of crystals will not be able to grow undesirably large before the crystals are burned away by the passing exhaust stream. If, on the other hand, the vehicle during a period of time is driven under relatively static conditions with a relatively low load, with low temperatures in the exhaust system as a consequence, such crystal build-up may continue until the vehicle's performance to an undesirable extent is adversely impacted by the increased flow resistance. The crystal build-up may also entail that the SCR system's ability to convert NO _x is impacted, if the supply of urea (e.g. spray image, amount) is disrupted because a deposit in the form of caki g arises. According to be above, this is resolved with the present invention by injecting the additive directly into the combustion chamber.

Combustion engines in vehicles of the type shown in Fig. IA are often equipped with controllable injectors in order to supply the desired amount of fuel at the desired point in time in the combustion cycle to the combustion engine's combustion chamber, such as at a specific piston position (crank angle degree) in the case of a piston engine..

Fig. 4 schematically shows an example of a fuel injection system for the combustion engine 101, exemplified in Fig. 1A. The fuel injection system consists of a so-called Common Rail system, but. the invention is equally applicable in other types of injection systems. Fig. 4 shows only one

cylinder/combustion chamber 401 with a piston 403 active in 1 the cylinder, but. the combustion engine 101 consists, in the present example, of a six-cylinder combustion engine, and may generally consist of an engine with any number of

cylinders/combustion chambers, e.g. any number of

cylinders/combustion chambers in the range 1-20 or even more. The combustion engine also comprises at least one respective injector 402 for each combustion chamber (cylinder) 401. Each respective injector is thus used for injection/supply of fuel into a respective combustion chamber 401, Alternatively, two or more injectors per combustion chamber may be used. The injectors 402 are individually controlled by respective actuators (not shown) arranged at the respective injectors, which, based on received control signals, e.g. from the control device 115, control the opening/closing of the

injectors 402.

The control signals for the control of the actuators '

opening/closing of the injectors 402 may be generated by some applicable control device, such as by the engine control device 115 in this example. The engine control device 115 thus determines the amount, of fuel which actually is to be injected at any given time, e.g. based on prevailing operating

conditions in the vehicle 100.

The injection system shown in Fig. 4 thus consists of a so- called Common Rail system, which means that all injectors (and therefore all combustion chambers) are supplied with fuel from a common fuel conduit 404 (Common Rail), which, with the use of a fuel pump 405, is filled with fuel from a fuel tank (not shown) at the same time as the fuel in the conduit 404 is pressurised to a certain pressure, also with the help of the fuel pump 405. When the respective injector 402 is opened., the highly pressurised fuel in the common conduit. 404 is then injected into the combustion chamber 401 of the combustion engine 101. Several ope ings /closings of a specific injector may be carried out during one and the same combustion cycle, whereby several injections may thus be carried out during the combustion of one combustion cycle. Further, each combustion chamber is equipped with a respective pressure sensor 406 for sending of signals regarding a prevailing pressure in the combustion chamber to e.g. the control device 115. The

pressure sensor may e.g. be piezo-based and should be fast enough to be able to send crank angle resolved pressure signals, for instance at every 10th, every 5th or every crank angle degree or with another suitable interval, e.g. more frequently .

With the help of a system of the type shown in Fig. 4, the combustion during a combustion cycle in a combustion chamber may be controlled to a large extent e.g. by using- multiple injections, where the times and/or duration of the injections may be controlled, and where data from e.g. the pressure sensors 406 may be taken into consideration in connection with this control. By using data from e.g. the pressure se sor, the nitrogen oxides resulting from the combustion may also be estimated, so that additive may be supplied to the combustion, for instance depending on the estimated amount of resulting nitrogen oxides. Regarding the supply of additive, each combustion chamber, or only a part of the combustion engine's combustion chambers, each comprises an injector 410 through the use of which the additive may be supplied to the

combustion chamber 401 from a tank 411.

Fig. 5 s ows an example method 500 for the supply of additive to the combustion chamber according to the present invention, where the method according to the present example is arranged to be car ied out by the engine control device 115 shown in Figs. 1A-B. In general, control systems in modern vehicles consist of a communication bus system consisting of one or more

communications buses to connect a number of electronic control devices (ECUs) , such as the control device, or controller, 115, a d va ious components arranged on the vehicle. According to prior art, such a control system may comprise a large number of control devices, and the responsibility for a specific function may be distributed among more than one con.tro1 device .

For the sake of simplicity, Figs. 1A-B show only the control device 115, in which the present invention is implemented in the embodiment displayed. The invention may, however, also be implemented in a control device dedicated to the present invention, or wholly or partly in one or several other control devices already existing in the vehicle. Considering the speed at which calculations according- to the present invention are carried out, the invention may be arranged to be implemented in a control device which is especially adapted for real time calculations of the type described below. The implementation of the present invention has shown that e.g. ASIC and FPGA solutions are suitable for and cope well with calculations according to the present invention.

The function of the control device 115 (or the control device (s) at which the present invention is implemented) according to the present invention, may, apart from depending on sensor signals from the pressure sensor 202, e.g. depend on signals from other control devices or sensors. Generally, control devices of the type shown are normally arranged to receive sensor signals from different parts of the vehicle, as well as from different control devices arranged on the

vehicle . The control is often controlled by programmed instructions. These programmed instructions typically consist of a computer program, which, when executed in a computer or control device, causes the computer/control device to carry out the desired control action, as a method step in the process according to the present invention.

The computer program usually is a part of a computer program product, where the computer program product comprises an applicable storage medium 121 (see Fig. IB), with the computer program stored on said storage medium 121. The computer program may be stored in a non-volatile way on said storage medium 121. Said digital storage medium 121 may e.g. consist of any from the following group : ROM (Read-Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash, EEPROM (Electrically Erasable PROM) , a hard disk unit, etc., and may be set up in or in combination with the control device, where the computer program is executed by the control device. By changing the computer program's instructions, the vehicle's behaviour may thus be adjusted in a specific

situation .

An example control device (control device 115) is shown schematically in Fig. IB, and the control device in turn may comprise a calculation unit 120, which may consist of e.g. a suitable type of processor or microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP) , one or several FPGA (Field-Programmable Gate Array) circuits or one or several circuits with a predetermined specific function (Application-Specific Integrated Circuit, ASIC) . The calculation unit 120 is connected to a memory unit 121, which provides the calculation unit 120 with e.g. the stored program code and/or the stored data that the calculation unit 120 needs in order to be able to carry out calculations. The calculation unit 120 is also set up to store interim or final results of calculations in the memory unit 121,

Further, the control device is equipped with devices 122, 123, 124 , 125 for rece iving and send.ing of input and. output

signals. These input and output signals may contain waveforms, pulses or other attributes which, by the devices 122, 125 for the receipt of input signals, may be detected as information for processing by the calculation unit 120, The devices 123, 124 for sending output signals are arranged to convert the calculation result from the calculation unit 120 into output signals for transfer to other parts of the vehicle's control system and/or the componen (s) for which the signals are intended. Each one of the connections to the devices for receiving and sending of input and output signals may consist of one or several of the following: a cable, a data bus, such as a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus, or any other bus configuration; or of a wireless connection.

Reverting to the method 500 shown, in Fig, 5, the method begins with step 501, where it is determined whether the supply, according to the invention, of additives to the combustion chamber for nitrogen oxide reduction should be carried out. The control according- to the invention may e.g. be arranged to be carried out continuously, as soon as the combustion engine 101 is started. According to one embodiment, injection of additive into a combustion chamber is carried out only if the injection is preceded by a combustion, during the same

combustion cycle ,

The method according to the present invention thus consists of a. method for the supply of ad.dit.ives to the combustion chamber of the combustion engine 101, while the combustion takes place in said combustion chamber 201 in combustion cycles. As is previously known, the term combustion cycle is defined as the steps comprised in a combustion in a combustion engine, e.g. a two-stroke engine's two strokes and a four-stroke engine's four strokes. The term also includes cycles where no fuel is actually injected., but where the combustion engine is still operated with a certain engine speed, such as by the vehicle's driving wheels via the driveline, in e.g. dragging. That is to say, even if no injection of fuel is carried out, a combustion cycle is still completed for e.g. every two revolutio s (for four-stroke engines), or e.g. every revolution (two-stroke engines) by the combustion engine's output shaft. The same applies to other types of combustion engines.

In step 502, it is determined whether a combustion cycle has or will be started, and when this is the case, the method continues to step 503, where an amount of nitrogen oxides resulting during combustion is estimated.

Generally, the supply of fuel to the combustion chamber, both with respect to quantity and manner of supply, i.e. t e one or several fuel injections that are to be carried out during the combustion cycle, is normally defined in advance, e.g.

depending on the work (torque) that the combustion engine must carry out during the combustion cycle.

Fuel injection is thus normally carried out according to an injection schedule, where several injections may be arranged to be carried out during one and the same combustion cycle. Combustion in connection with these fuel injections will give rise to resulting- nitrogen oxides.

According to the present invention, during the combustion cycle the prevailing pressure in the combustion chamber is determined substantially continuously using the pressure sensor 406 for instance at applicable intervals, e.g. every 0.1-10 crank angle degrees.

The combustion process in a combustion chamber may generally be described with the pressure change that the combustion gives rise to in the combustion chamber. The pressure change during a combustion cycle may be represented by a pressure track, i.e. a representation of how the pressure in the combustion chamber varies during the combustion.

In step 503 thus the pressure p _f is dete mined substantially continuously in said combustion chamber 401, by using said pressure sensor 206 during the course of the combustion in the combustion chamber . By using the pressure change, generated nitrogen oxides NO _x generated may during- the combustion cycle be estimated with the use applicable calculations, and one way to carry out the calculation is exemplified below.

Alternatively, other models with similar functions may be applied .

Generally, nitrogen oxides NO _x are mainly formed for three different reasons during a combustion process . The fuel may comprise nitrogen, and nitrogen will be released during combustion and at least generate nitrogen gas ? and nitrogen oxides Οχ . This type of NO _¾ formation may in some types of combustion, and depending on the type of fuel, account for a large part of the total amount of nitrogen oxid.es NO _x generated at combustion. As explained below, this type of NO _x formation may, however, be disregarded during normal combustion

according to e.g. the diesel cycle. Another source of NO _x formation consists of so-called prompt NO _K formation, but this source may generally be disregarded, since the impact is small in relation to other sources. A third source, which during normal combustion also constitutes the primary cause of KO _x formation during combustion at high combustion temperatures, consists of thermal formation of NO _x , which may account for in the range of 90-95% or even more of the KO _x formation during the combustion cycle.

The NO _x formation is thus heavily dependent on the combustion temperature, and the formation of thermal NO _x may in itself be described in a well-known manner, e.g. according to three main reactions (the expanded Zeldovich mechanism) :

N2 + 0 → NO + N

N + 02 → NO + 0 (1) N + OH -→ NO + H

, whe e thus the reaction speed is heavily dependent on temperature, and where also the temperature dependency as such is known, so that the amount of nitrogen oxides NO _x formed may be estimated through knowledge about the (substance) amount of the substances included and the temperature .

According to the present invention, NO _x formation is estimated by using the above chemical reaction formula, equation (1), and by using an estimation of additional combustion data. The calculation thus also requires knowledge about the available amount of nitrogen ₂ and oxygen O ₂ , as well as knowledge about access to hydrogen H. These may be obtained, from, the

combustion's combustion chemistry, which is known to a person skilled in the art, and for which the supplied amount of fuel and combustion air, as well as any exhaust recirculation is known, whereby, in combination with the fact that the fuel composition is normally known, the amounts of the substances included in equation (1) may be calculated.

Also, an estimation of the combustion's temperature is

required for estimating the amount of nitrogen oxides NO _x generated., since the reaction speed, is dependent on temperature. Likewise, pressure and/or mean temperature in the combustion chamber is required in order to, through the combustion chemistry, be able to estimate released nitrogen and oxygen during the combustion .

At the estimation of the amount of nitrogen oxides NO _x formed, knowledge about the combustion temperature itself is therefore required. The temperature is higher in the part of the

combustion chamber where the combustion is ongoing, and the combustion chamber may be considered to consist of two zones, where combustion takes place in one zone, with a high

temperature in this zone as a consequence, while no

combustion, with a lower resulting temperature, takes place in the other zone. In total, at each moment a mean temperature in the combustion chamber is thus obtained, falling below the combustion's temperature where combustion is ongoing. In order to be able to carry out a desirable determination of the combustion's temperature, knowledge about the heat release during combustion is also required.

This may be determined in different ways. For example, as described below, the estimated heat release may be predicted through the use of a combustion model. This is exemplified in the international patent applications described below. In these applications, future parts of a combustion are

estimated, while according to one embodiment of the present invention, pressure signals from, the pressure sensor 406 may be used to calculate heat release during combustion.

Heat release during combustion may then be expressed as: Where d() is released heat, p constitutes the pressure in the combustion chamber,

V constitutes the volume of the combustion chamber, while dV constitutes the volume change of the combustion chamber.

Υ(φ) , i.e. the combustion chamber's volume as a function of the crank angle, may advantageously be tabulated in the control system's memory, or be calculated in an applicable manner,

dV

whereby also may be determined,

άφ γ C _B (f) c ^: „— where C„ and/or C are preoared and tabulated

C _v (t) C _p -R ^p

for different molecules, and since the combustion chemistry is known, these tabulated values may be used together with the combustion chemistry in order to thus calculate each

molecule's (e.g. water, nitrogen, oxygen, etc.) impact on e.g. the total C value, so that this may be determined for the calculations above with a good accuracy. Alternatively, C and/or C _v may be approximated in a suitable manner. dp constitutes the pressure change i the combustion chamber, determined with the pressure se sor 406. dQ _m represents the heat released during combustion, which may be determined in a manner which is well described in the prior art technology by e.g. Woschni. Here, regard may also be had to blackbody radiation in the combustion chamber in a known manner . The international patent application PCT/SE2014/ 050493 entitled "METHOD AND SYSTEM FOR CONTROL OF AN INTERNAL

COMBUSTION ENGINE", describes a method for estimating released heat during an ongoing combustion. The method described in this application may be applied according to the present invention. Further, the method shown in said application may be simplified, as no estimation of the pressure is required according to the present embodiment, and pressure signals from the pressure sensor 406 may be used during an ongoing

combustion cycle up to the point in time when the maximum amount of nitrogen oxides is deemed to have been generated, according to the below. Said application also shows how the heat release may be estimated before a combustion.

According to the present example, however, the heat release may be estimated according to equation (2) through the use of signals from the pressure sensor 406. Fig. 6 shows, as a rough approximation, how the heat release 603 may change during a combustion cycle. Instead of expressing the combustion process as a function of time, it is expressed as a function of the crank angle degree φ. Fig. 6 also snows how the modelled NOx amount 601 resulting during combustion changes during the combustion cycle, as well as how the mean temperature 602 in the combustion chamber changes during the combustion cycle.

The pressure change p as a function of the crank angle degree φ in a cylinder (combustion chamber) for a combustion cycle may, according to the above, be obtained through the use of sensor signals from the pressure sensor 406. Further, by using a determined pressure the temperature for the part of the combustion chamber where no combustion occurs may be estimated with the help of an estimated pressure and by using equation (3) , where the temperature for the part of the combustion chamber where no combustion takes place is expressed as: P

, where T _{ri Q} may constitute corresponding combustion air temperature for e.g. the point in time/crank angle position where the valves are closed, after the supply of combustion air .

Further, n, nil, etc, constitute consecutive points in time or cra.nk a.ng1e posit ions .

Κ-γ wherein thus also K may be determined as specified for γ a ove .

By using equation (3) the temperature for the part of the combustion chamber where no combustion takes place may be determined, this temperature, however, being impacted by ongoing combustion through the effect of the heat release on the pressure, which is reflected in the signals emitted by the pressure sensor, which in turn impacts the temperature

according to equation. (3). When a. combustion then, takes place, the heat release will give rise to a temperature increase i the part(s) of the combustion chamber where combustion is taking place. This temperature increase, which is added to the temperature determined in equation (3} in order to obtain the combustion temperature, may be calculated, based on the

correlatio : dQ mC _p dT (4)

, where dQ constitutes neat release, which may be determined as above. m consists of burned mass (i.e. fuel + air + EGR comprised in the combustion) , which is also determined as set out above,

C , i.e. specific heat capacity, which may also be calculated as set out above. dT constitutes the temperature increase obtained from the combustion, with a given burned, mass and with a given C value .

By using equation (4), dT and therefore ΔΤ may thus be determined, so that the increase generated by the combustion at each point in time/crank angle position may be added to the temperature of the part of the combustion chamber where no combustion occurs, provided by equation (3), to obtain the combustion temperature .

When the combustion temperature has been estimated, the concentrations and/or absolute amounts of primarily N ₂ and O ₂ may thus be calculated by using the combustion chemistry, so that later, by using equation (1) and its combustion

temperature dependency, generated, nitrogen oxides NO _x may then successively be estimated and accumulated for the combustion cycle. The modelled nitrogen oxides basically are generated up to the maximum combustion, temperature having been, achieved, or during a certai time thereafter, i dicated, with the crank, angle position <pj in Fig. 6.

Thus, in para.11el with the estimation of the resulting

nitrogen oxides, it may be determined whether T _;;13X for the combustion cycle has been reached - step 504 - so that, when this is the case, the method continues to step 505 for

determination of an applicable amount of additives for

injection into the combustion chamber 201 by using the

injector 410, where the applicable amount of additive for injection may e.g. be determined through the use of known chemical correlations at. reactions between additives and nitrogen oxides. For example, the amount of additives may be determined as a stoichiometric amount of additive, i.e. the amount of additive required in order to entirely convert the amount of nitrogen oxides. The amount, of additive supplied to the combustion chamber may also e.g. consist of some

applicable fraction of a stoichiometric amount, such as more or less than this amount . For example, it may be desirable only to reduce nitrogen oxides NO _x to a certain extent, meaning a smaller amount may be supplied. For example, an amount may be supplied which is expected to entail that the vehicle's emissions meet the prevailing regulatory requirements where the vehicle is driven. Alternatively, the amount may be arranged to exceed the stoichiometric amount, e.g. with the objective to achieve a high reaction rate. The amount may also be arranged to fall below the stoichiome ric amount, e.g. if only a certain reduction is required or desired in the combustion chamber. Further reduction may as and when needed e.g. be achieved with the use of an SCR catalyst as per the above.

According to one embodiment, the combustion chamber's

temperature is also used, i.e. the temperature track 602 in Fig 6, for the determination of the applicable amount of additive, where the reaction rate is heavily temperature- dependent, so that the amount of additives may thus e.g. be determined as a function of one or several of the amount of resulting nitrogen oxides, pressure in the combustion chamber, temperature in the combustion chamber. According to one embodiment, the amount of resulting NO _x is estimated successively, so that when it is determined that this has reached its maximum and/or begins to decrease, e.g. at or after the position φ _χ in Fig. 6, which normally also occurs via other chemical reactions than via a reaction with an additive, although with a significantly lower reaction rate, the applicable amount of additives for supply may be determined .

The additive is then injected in step 506, so that the method, may revert to step 501 for a new determination for a

subsequent combustion cycle. According to the present

invention, the amount of resulting nitrogen oxides during a combustion cycle thus may be estimated, so that an amount, of additive adapted to the amount of qenerated nitrogen oxides may be injected into the combustion chamber in order to already achieve reduction of the nitrogen oxides in the combustion engine where a high tem.perat.ure prevails, and the efo e without a y need for an SCR catalyst. The present invention thus has the advantage that the need for an SCR catalyst may be eliminated completely, or at least reduced. According to one embodiment, additives may also be injected, upstream of an SCR catalyst, where needed., wherein e.g. a smaller SCR catalyst than would otherwise be possible may be used, but in many cases the need for an SCR catalyst

disappears entirely when the present invention is used.

Further, problems with crystal formation, etc. due to low temperatures, according to the above, may also be completely or to a great extent avoided according to the present

invention .

According to one embodiment, no injection of additives is carried out unless the combustion, chamber's mean temperature exceeds some applicable temperature Tii _m , e.g. 700-750°C. This embodiment thus requires knowledge about not only the

combustion's temperature, according to the above, but also about the mean temperature for the combustion chamber, i.e. the curve 602 in Fig, 6. This mean tem.perat.ure 602 may e.g. be estimated according to the description in the international patent application PCT/SE2014/050491, which describes in detail how the mean temperature in a combustion chamber may be estimated through the use of e.g. the pressure in the

combustion chamber, which may be obtained with the pressure sensor 406. According to the method shown in said application, an

estimation for future time is carried out, and such estimation may also be applied, in the present invention in order to thus, through estimation, predict the applicable amount for

injection already before the generated nitrogen oxides have reached the maximum level. In this case, the model shown in. the said application or another applicable model of the combustion may also be used..

One embodiment, however, uses the fact that pressure signals from thie pressure sensor 206, represent. ing t.he actua11y prevailing pressure in the combustion chamber, may be used up to the point when the amount of nitrogen oxides has reached the maximum, amount of nitrogen oxides, i.e. the position ci in Fig. 6, so that no estimation is required, and where the heat release may e.g. be estimated according to the above, and where the mean temperature may be determined e.g. according to the general gas law. Thus, according to one embodiment, it may be determined that the tem.perat.ure is sufficiently high for the desired reactions to arise, e.g. a prevailing mean

temperature in the combustion chamber exceeding 700-750 °C, where such mean temperature may thus be determined with the use of the general gas law in k own manner and, as also shown in said application, so that the unwanted crystal formation may be avoided.

Thus, according to one embodiment, the injection is carried out only if the temperature exceeds the temperature Tlim, displayed in Fig, 6, so that the interval cpi~ <p ₂ constitutes a "window" in which injection of additive should occur. This "window" may also e.g. be limited in respect of maximum temperature, i.e. injection may be arranged to occur only if the temperature in the combustion chamber drops below some applicable tem.perat.ure, where thus ψι may be shifted to the right in Fig. 6. Further, it should be noted that the

injection of an additive need not be carried out precisely where a combustion is actually ongoing in. the combustion chamber, but the injection may occur in any location inside the combustion chamber, e.g. with the additional condition that said mean temperature does not drop below Him.

According to one embodiment , the method, shown i said

international patent application PCT/SE2014/050491 may also be applied in order to, e.g. before the position φ _χ estimate whether the mean temperature will be sufficiently high for injection, to be possible, and. if it is co cluded that this is not the case, an extra fuel injection may e.g. be carried out based on such estimation, with the objective to increase the temperature in the combustion, chamber to enable injection, of add.it ive .

If this injection is carried out sufficiently late during- the combustion cycle, the injection will not. contribute to NO _K formation, but will increase the temperature. At the

application of such an extra injection, this may be arranged to be of a size determined in. advance, but it may also be arranged to be determined by using estimation according to the method shown in said international patent application

PCT/SE2014/050491, for example to determine the applicable amount of fuel for injection, separately or jointly with the injection, of additive, in order to obtain the desired,

temperature . According to the hitherto described embodiment, the estimation of the resulting amount of nitrogen oxides has been carried out during the ongoing combustion cycle, so that likewise an amount of additive based on the estimated resulting amount of nitrogen oxides is supplied.

According to one embodiment, nitrogen oxides are instead estimated during a combustion cycle, where, based on this estimation, the injection of additive is carried out during one or several subsequent combustion cycles. This has the advantage that the estimation may be carried out more

infrequently .

According to a simpler form of the invention, no estimation of nitrogen oxides is carried out, but additive is injected into the combustion chamber at the applicable point in time, where e.g. the injected amount may instead be arranged to depend on the amount of fuel that is supplied to the combustion, or a standard amount may always be applied, e.g. as long as at least one minimal amount of fuel is injected. According to a preferred embodiment , however , an estimation of the resulting nitrogen oxides is carried out.

Further, the present invention has hitherto been described in connection with a method where the nitrogen oxide formation is estimated up to the point in time during the combustion cycle, where nitrogen oxides are deemed to have been formed.

According to the above, this is indicated with crank angle position ci . According to the displayed embodiment , the control system thus has knowledge about the appearance of the pressure change in the combustion chamber 401 up to the position <pi, since it has been possible to determine this with the use of the pressure sensor 406. When the nitrogen oxide formation is then deemed to be completed, the amount may be estimated by using the actual pressure development, and an applicable amount of additive for injection during the subsequent part of the combustion cycle may be determined, based on the estimated amount of nitrogen oxides NO _x .

Further, according to the embodiment displayed, the prevailing temperature in the combustion chamber 401 may be estimated by using the actually detected, pressure change, so t at the applicable point in time for injection of the additive may be determined and so that injection occurs when the temperature in the combustion chamber 401 is within a desired temperature range .

According to one embodiment of the invention, the injection of additive is instead carried out at an earlier stage during the combustion cycle, e.g. completely or partly before the

combustion is initiated or ended, such as e.g. completely or partly before the fuel injection is initiated. One example of such a method is illustrated in Fig-. 7. Fig-. 7 shows the pressure p in the combustion chamber 401 as a function of the crank angle degree φ. In Fig. 7, a solid line 701 shows the pressure change in a combustion chamber when no combustion is carried out, i.e. the pressure change that, due to the

piston's backwards and forwards motion, the combustion chamber is subject to when inlet and outlet valves are closed. (DT _V C represents the crank angle degree where the inlet valves are closed and cp _EV o represents the crank angle degree where the exhaust valves are opened and the atmospheric pressure atm or the prevailing combustion air pressure thus prevails. (p _TDC represents the piston's top dead centre. The dashed line 702 represents the pressure change arising in the combustion chamber as a result of the combustion, where, in this example, combustion is initiated, substantially at the piston's top dead centre <p _T0C . The hatch-lined surface 703 thus represents the pressure change that the combustion gives rise to. According to the above example, the injection of additive has been carried out during the part of the combustion cycle following after crank angle position φ _Α , i.e. after the maximum pressure has been reached, which substantially corresponds to the position where the temperature will also be at a maximum during the combustion cycle.

According to one embodiment, the additive is instead supplied before the combustion is initiated, i.e. during the time starting when the inlet valves are closed at <p _IVC until the combustion is initiated, i.e. in the present example in the interval (p _IVC - cp _TDC . For example, the supply of additive may be arranged to be carried out within some applicable partial interval of the interval (p _IVC - Φτοο _? e.g. between the time <p _B -<p _c in Fig. 7. cp _B may e.g. be set so that the temperature in the combustion chamber exceeds some applicable tem.perat.ure.

According to the example displayed in. Fig. 6, the NO _x level may be estimated substantially when the combustion has ended, so that the measured pressure may be used in the calculation model according to the above, for calculation of generated nitrogen oxides NO _x . In case the additive is supplied before the combustion is started, an actual pressure track 701 may not be used up to the position (e.g. <p _A in Fig. 7) where the nitrogen oxides may be deemed to have been formed, in order also to estimate the nitrogen, oxide occurrence after the combustion, since this combustion has not. yet. occurred. At. the same time, it is desirable for an amount of additive to be supplied, which is adapted to the amount of nitrogen oxides that will later be formed during the combustion, cycle. The applicable amount of additive may be determined in several different ways. According to one embodiment , the generated nitrogen oxides NO _x are estimated according to the above, 3 during a combustion cycle, so that the additive is supplied, only during a subsequent combustion cycle. This method may e.g. be applied when the conditions for several consecutive combustion cycles are substantially the same.

According to one embodiment, however, an estimation of the nitrogen oxides NO _x formed during the subsequent part of the combustion cycle is carried, out, so that additive is supplied before the combustion has actually occurred, and based on an estimated outcome of the combustion. The amount of generated nitrogen oxides may be estimated accordinq to the above equations, but where knowledge about future pressure change in the combustion chamber is a prerequisite, since there is no knowledge of this. The pressure change in the combustion chamber may e.g. be estimated according to the international patent application PCT/SE2014/050495, where a method is described to estimate the amount of generated, nitrogen oxides, so that the combustion may then be controlled based on the expected amount of nitrogen oxides.

According to the present invention, the method exemplified in said application may be used to estimate the amount of

nitrogen oxides generated, where said application exemplifies how the pressure change during a future part of the combustion cycle may be estimated, so that such estimated pressure may be used in the calculations described above. As described in said application, knowledge of the fuel amount that will be

injected during the combustion cycle, and when the injection occurs, is required for the calculation. However, this usually constitutes known data, also been described above in

connection with, the calculation, of the heat release due to the combustion, and which is thus described in further detail in the international application PCT/SE2G14/G50493, where

prediction through estimation of neat release for a future part of the combustion cycle, which thus is performed when the calculations are carried out with the help of an estimated pressure, is described in detail.

By using the method displayed in the international patent application PCT/SE2014/050495, the expected amount of formed nitrogen oxides NO _x may thus be estimated before the time φ _Β in Fig. 7, so that also an applicable amount of additive for injection may be determined before/at the position <p _B in Fig. 7, so that such amount may then be injected in the combustion chamber, e.g. during the interval φ _Β _φ ₀ . The amount of

additives for supply may e.g. consist of a stoichiometric or other applicable amount. For example, it may be desirable to supply a larger amount of additive than what is ideally consumed to reduce the expected nitrogen oxide amount, since the additives may be "burned" during the combustion and thus reduce the efficiency of the O _x reduction.

Further, an injection of additive before the combustion will impact the combustion process itself. As is obviously the case, this depends on e.g. additional substance being

supplied to the combustion chamber. Additionally, the additive is usually a liquid, where the liquid may contain a relatively large fraction of e.g. water. The liquid supplied, will evaporate entirely or to a great extent, wherein energy is consumed at the evaporation, with the consequence that the temperature in the combustion chamber will be reduced .

Additionally, a dissociation effect arises when gaseous water molecules are split into hydrogen and oxygen, respectively, where energy is consumed for the molecule split. This in turn will impact the combustion, where a reduced temperature may entail that. a. smaller amount of nitrogen oxid.es is generated, as a result of which a smaller amount of additive is required only because of this ratio. Thus, the calculation of the expected formation of nitrogen oxides NO, should take into consideration the amount of additives supplied, which is why the additives should also be included in the calculation. This in turn may require that iterations are required to find an additive amount for supply, which corresponds to the amount of nitrogen oxides that will be generated at a combustion occurring after the additive has been supplied.

Regarding the calculations, the additive will impact specific heat capacity in the combustion chamber and thus impact gamma Y in the above equations. More specifically, the impact of the change in specific heat capacity may be obtained by

calculating specific heat capacity at a constant pressure C _p and at a constant volume C _v , respectively, where exhaust recirculation, EGR, is also treated in the below calculation.

Heat capacity is tabulated for different chemical substances and elements in tables issued by NASA, and are interpolated as a function of temperature, where the combustion chamber's mean temperature is used. This temperature may e.g. be estimated according to the description in the international patent application PCT/SE2014/050491, which describes in detail how the mean temperature in a combustion chamber may be estimated through the use of e.g. the pressure in the combustion

chamber, which may be estimated according- to the above.

Generally, the specific heat capacity at a constant, pressure Cp is tabulated in the form: α, Τ ^'"2 + α ₂ Τ ^"Λ +

R ₃ + a ₄ T + α _$ Τ ^Δ + ₆ Γ ³ + α ₇ Τ 4 (5)

The specific heat capacity for a constant volume, C _v , may then be calculated as C _v — C _p ~R , so that gamma γ may thus be calculated. When gamma γ has been calculated, the generated amount of nitrogen oxides may be estimated as per the above. The additive's impact on gamma γ is described below.

As mentioned, it may also be advantageous, during the

calculation of gamma γ, to have regard to the case where EGR recirculation is carried out, i.e. when a part of the exhausts from the combustion is recirculated to the combustion engine's inlet side, impacting the chemical composition in the

combustion chamber. Control of the EGR recirculation normally consists of its own regulation, but as described below, it may be advantageous to adjust the EGR recirculation based on the amount of additives supplied. When EGR recirculation is applied, e.g. the following correlation may be applied to estimate specific heat capacity at a constant pressure for EGR recirculated gas, where a and b constitute the number of carbon atoms and hydrogen atoms, respectively, in the fuel used to operate the vehicle, i.e. C _a H _b , and where λ _χ

constitutes the lambda value,

+ -i- )(C½i -l)c _pi v÷3,773. ₅ ; c _vN2 )

_CpEGR ^::: a^mJ^)^) ^

A corresponding calculation of specitic heat capacity

constant volume for pure air consists of: c _pAjR =-£ (3-773c _pN2 (T + Cpo ₂ (T)) (7)

With the objective of obtaining a correct gamma value, the respective heat capacity is weighted according to equation (8), where EGR% constitutes the EGR level:

CvAiR * (1 ^~ EGR%) + c _pEGR * EGR% (8) the EGR level may e.g. be determined as an EGR level

determined during a previous combustion cycle. Alternatively, the EGR level may be determined, via e.g. emission

calculations, where e.g. carbon dioxide calculations may be used to determine how large a part of the combustion air consists of recirculated exhausts. For example, this may be carried out. by measuring the carbon dioxide level at the inlet to the combustion chamber and at the outlet of the combustion chamber, or further downstream in the after-treatment system, so that the EGR level may be calculated in a manner familiar to a person skilled, in the art. The EGR recirculation thus constitutes a variable which is not calculated specifically for each combustion cycle, but which is normally available in the vehicle's control system, where this is calculated with applicable intervals. Generally, the control of EGR

recirculation is much slower than control according to the present invention.

Regarding the additive ' s impact, on specific heat capacity, and thus gamma γ, this may be determined using the following calculation : m ti.li.smede!. (Ό

c _p (T) * (1 ^■■■■ tillsmedelandel) + c _{p t} Ms _m edei. () * tillsmedelandei (9)

, where c„ _ti ,, _smedi ,, (T) may be known and tabulated. Alternatively, c _{m m!del} {T) may be determined in the same manner as described for c _EGR above through knowledge about the additive's composition. Gamma, y may then be determined as :

Y ^-p med tiilsniedel I *-v med ti.llsmedel (1 0)

, whe e: cv med tiilsniedel ^{~ c} p med tiilsniedel ~ R ( ) By using a calculated γ, which has been compensated, for injection of additive before the combustion, the expected generated nitrogen oxides during the combustion may thus be estimated according to the above, so that it may be concluded that a smaller amount of additive is required., so that a new calculation for a smaller amount of additive may be carried out, etc. The applicable amount of additive for injection before the combustion, may thus be iterated until the desired amount of additive in relation to the expected amount of formed nitrogen oxides is obtained at the calculations.

In connection, with the supply of additive to the combustion according to the present invention, there are also additional aspects that should be considered. For example, according to the above, an EGR recirculation of a part of the exhausts that are formed during- combustion is normally applied. The EGR recirculation generally has a positive (reducing) impact, on the NO _z formation. The supply of additive will entail an altered exhaust stream composition compared to the case where no additive is supplied. For example, the additive may

consist, according to the above, partly of water, so that a greater fraction of water than normally present will likely occur in the resulting exhaust stream. This means that a regulation of the EGR recirculation, based on the supply of additive, may be required. For example, the EGR recirculation may be required to be reduced because of a relatively higher water content in the exhaust stream, which gives a better effect with respect to NO _x reduction, but with a. risk that an undesirably high water content, may be obtained in the

combustion chamber if the EGR recirculation becomes too high in relation to the water content.

The control of the EGR recirculation may be carried, out in any- suitable manner, where e.g. the EGR recirculation's impact on the specific heat capacity, according to the above, inay be taken into consideration and wherein the EGR recirculation may e.g. be controlled based on these calculations. Generally, control of the EGR recirculation is slow (in the range of seconds) compared, to the control carried out according to the present invention, where calculations are carried out during the ongoing combustion cycle and where calculation may be carried out in e.g. one hundredth of a second, thousandth of a second or an even shorter time.

Further, during the supply of additives to the combustion chamber, there are additional aspects that should be

considered. The pressure in a combustion chamber may rise to relatively high pressures, such as a maximum pressure in the range of 200-300 bar. Normally, the fuel injection is carried out with substantially higher pressure than the combustion chamber pressure, e.g. at 1, 500-2, 500 bar, so that changes in the combustion chamber's pressure become substantially

negligible in relation to the high fuel injection pressure. This means that the injected amount of fuel may be determined with good accuracy . The use of high pressures is, however, usually connected with high costs, which is why it may be desirable to carry out the injection of additive at

substantially lower pressures, e.g. at a pressure in the same size range as the prevailing combustion chamber pressure. This in turn means that, due to the combustion chamber's back pressure, for a certain opening time of the injection nozzle for the injection of additives, different amounts may be supplied for one and the same opening time, depending on the prevailing combustion chamber pressure. Thus, the additive ' s injection time may be arranged to be controlled based on the prevailing combustion chamber pressure, where this may be determined e.g. by using the pressure sensor 406. Thus, at prevailing higher combustion chamber pressures a longer opening time may be used compared to where the

prevailing combustion chamber pressure is lower, wherein, obviously, the prevailing combustion chamber pressure will depend on the crank angle position at which the injection of additive occurs.

Further, the present invention comprises a solution where liquid, such as a liquid partly containing water, is supplied to the combustion engine's combustion chamber. This liquid supply may require that certain, protection aspects/measures may need to be considered. According to the above, in the case with injection of additive after the combustion, a lower temperature limit has been exemplified in order for the desired conversion to take place. There may also be

restrictions for other reasons, with respect to at which point in time during the combustion cycle the injection of additives should occur. For example, it may be desirable that the piston at a maximum may be located a certain number of crank angle degrees from the top dead centre when injection takes place, so that not too great a part of the cylinder wall is revealed during the injection, with a risk of a wall hit and the oil film being washed away as a consequence, and thus an

associated risk of unwanted wear.

Further, the supply of additive may e.g. be arranged to be closed if the vehicle ' s speed drops below some determined speed, or if the vehicle comes to a standstill, or if for another reason there is a risk that the combustion engine will shortly be shut down. In such situations, it may be desirable that e.g. the occurrence of water in the combustion engine system is reduced before the combustion engine is shut down, in order to avoid water-related damage . According to one embodiment of the invention, the supply of additive may be arranged to be shut off if the vehicle's speed drops below some applicable speed, and the vehicle's ambient temperature drops below e.g. zero degrees Celsius, with the objective to avoid that water remains in the system after the combustion engine has been shut down with a risk of freezing as a

consequence .

Further, the above embodiments may be combined with a method that adjusts the combustion as the combustion progresses, wherein the combustion is controlled based on some applicable criterion. In e.g. the international patent application.

PCT/SE2014/050495, a method is described where the combustion is controlled during the combustion cycle based, on an expected and, during an ongoing combustion cycle, estimated amount of resulting nitrogen oxides. According to one embodiment, the method according to the invention may be combined with the method shown in said application, so that the amount, of resulting nitrogen oxides NO _x before the supply of additive may be arranged to be controlled through control of the

combustion . Further, the amount of additive for supply to the combustion chamber may be arranged to be determined, based on an estimation of the resulting nitrogen oxides, according to the description in said international patent application

PCT/SE2014/050495.

Further, the method may be arranged to be interrupted when the temperature in the combustion, chamber has reached, the maximum temperature during the combustion, as substantially all nitrogen oxide generation likely will have taken place before this point in time, so that subsequent control may instead e.g. be carried, out entirely according to the selected

injection schedule, or may carried out based on some other app1ica.b1e cri ter i on . The invention has often been exemplified in a manner where a pressure sensor 406 is used to determine a pressure in the combustion chamber, and with the help of which the temperature and nitrogen oxide generation, as set out above, may be estimated. One alternative to using pressure sensors may instead consist of the use of one (or several) other sensors, e.g. high-resolution ion current sensors, knock sensors or strain gauges, where the pressure in the combustion chamber may be modelled, by using sensor signals from, such sensors. It is also possible to combine different types of sensors, e.g. in order to obtain a more reliable estimation of the pressure in the combustion chamber, and/or to use other applicable sensors, where the sensor signals are converted into

cor esponding pressures for use i control, as set out above.

The method according to the invention for the control of the combustion engine may also be combined with sensor signals from other sensor systems, where the resolution of the crank angle level is not available, such as another pressure

transmitter, Ox sensors, NH3 sensors, PM sensors, oxygen, sensors and/or temperature transmitters, etc., the input signals of which may e.g. be used as input parameters in the estimation of e.g. the expected pressure/temperature by wholly or partly using computer-driven models instead of models of the type described above. For example, signals from an NO _K sensor arranged downstream of the combustion engine may be used for the determination of the applicable amount of additive for supply to the combustion, chamber. In. this case, e.g. an undesirable high NO _x level indicated by the NO _K sensor may entail an increase of the amount of supplied reductant.

Additionally, the present invention has been exemplified above in relation to vehicles. The invention is, however, also applicable to any vessels/processes where nitrogen oxide control, as set out above, is applicable, e.g. waterc.ra.fts or aircrafts with combustion processes as per the above.

It should also be noted that the system may be modified according to various embodiments of the method according to the invention (and vice versa) , and that the present invention is in no way limited to the above described embodiments of the method according to the invention, but pertains to and

comprises all embodiments in the protection scope of the enclosed independent claims. For example, the invention is applicable to the injection of any additive in the combustion engine's combustion chamber, where such additive may be intended to reduce nitrogen oxides, or one or several other conta.mina.nts .