DK178072B1 - A method of operating an internal combustion engine - Google Patents

Abstract

An internal combustion engine uses exhaust gas recirculation. The engine is operated at times in an environment with a first emission standard and at other times in another environment with a second more strict emission standard. The engine is operated with a first fuel or with a second fuel having a second lower calorific value when operating in said another environment having said second emission standard, which second lower calorific value is lower than the first lower calorific value of the first fuel. The engine is operated with a first degree of exhaust gas recirculation when operated with said first fuel and with a second, higher degree of exhaust gas recirculation when operated with said second fuel.

Description

The present invention relates to a method method of operating an internal combustion engine having cylinders with a reciprocating piston inside the individual cylinder and a combustion chamber above the piston, and at least one fuel injector injecting during operation fuel directly into the combustion chamber above the piston , said engine being operated with exhaust gas recirculation, and said engine being operated at times in an environment with a first emission standard limiting emission of polluting components with the exhaust gas and said engine being operated at other times in another environment with a second more strict emission standard limiting emission of such polluting components with the exhaust gas. WO-A-2009/046713 discloses a method and an apparatus for controlling a dual fuel compression ignition engine whereby fuel for the engine is mixed from different components to adjust the quality of the fuel in order to thereby adjust the time of ignition. Thus a fuel mixing unit is disclosed. EP-B-0 459 983 and EP-B-0 553 364 both disclose an apparatus for injecting a mixture of fuel and water into a diesel engine whereby fuel and water is injected alternately at closely spaced intervals in order to simultaneously reduce black smoke and reduce NOx. US 2011/0288744 relates to an engine having an exhaust gas recirculation conduit and an exhaust gas recirculation valve and a fuel injection system operable on several fuels. A controller controls operation so that specific fuel consumption is reduced, and at the same time exhaust emissions and components in the engine are operating within treshold limits.

Generally, the present invention aims at reducing NOx in the exhaust gas of an internal combustion engine. Exhaust gases of internal combustion engines are subject to restrictions in respect of contents of various polluting components such as NOx, and in general it is undesirable to emit particulate matter (PM) or soot.

The International Maritime Organization (IMO), which is an agency of the United Nations, has set emission standards of limits known as Tier I, Tier II and Tier III, the laughter to enter into force in 2016, where Tier I and Tier II emissions standards are globally effective, while the Tier III emission standard applies only in NOx Emission Control Areas (ECA). Tier II and III NOx emission standards have effect for new engines, while Tier I NOx requirements are for existing engines built before year 2000.

Thus, self-propelled vessels like ships navigating around the world will at times be in Tier II areas, i.e. environments where Tier II applies, and at other times in other environments (ECA) where Tier III applies, ECA being mostly defined for coastal areas.

Exhaust gas recirculation (EGR) is known to be an effective way of reducing NOx emission from an internal combustion engine having inside the individual cylinder a reciprocating piston and a combustion chamber above the piston and at least one fuel injector injecting during operation fuel directly into the combustion chamber above the piston.

During operation of the internal combustion engine, a cylinder charge comprising a mixture of inlet air and recirculated exhaust gas is taken into the combustion chamber and a spray of fuel is injected into the combustion chamber at appropriate timing with respect to the engine operating cycle, and the injected fuel ignites and develops a combustion zone within the combustion chamber. The inlet air comprises oxygen while the recirculated exhaust gas is void of oxygen or has a low oxygen content. On the other hand, the recirculated exhaust gas is relatively rich in water vapor and carbon dioxide compared to the inlet air. According to the cylinder charge has a relatively low content of oxygen and high content of water vapor and carbon dioxide compared to traditional inlet air without exhaust gas recirculation, and both the low content of oxygen and the high content of water vapor and carbon dioxide are factors that reduce the combustion temperature and, since most NOx is formed via a thermal pathway, thus reduce the formation of NOx in the combustion zone, compared to a situation where pure inlet air is used for the cylinder charge. Exhaust gas recirculation has shown a potential of lowering the emission of NOx by up to 80%.

However, as exhaust gas recirculation is increased formation of particulate matter (PM) or soot and also formation of carbon monoxide increase, and this is undesired and sets limits to the degree of exhaust gas recirculation.

The object of the present invention is to provide for further reduction of NOx emission from the internal combustion engine by using a high degree of exhaust gas recirculation, while simultaneously suppressing the emission of excess amounts of soot particles, for use in environments where additional reduction of NOx emission is required.

With a view to achieving this the method according to the present invention and as mentioned by way of introduction, is characterized in that a) when operating in the environment having said first emission standard, the engine is operated with a first fuel having a first lower calorific value and with a first degree of exhaust gas recirculation, and b) when operating in another environment having said second more strict emission standard, the engine is operated with a second fuel having a second lower calorific value and with a second degree of exhaust gas recirculation, which second lower calorific value is lower than said first lower calorific value, and which second degree of exhaust gas recirculation is higher than said first degree of exhaust gas recirculation, and that, for a given engine load, fuel injection is initiated with a timing in the engine cycle which is earlier when the internal combustion engine is operating with the second fuel than when the internal combustion does not e is operating with the first fuel.

When the engine is operated in another environment having the second emission standard, the second fuel is injected into the cylinder and the second, higher degree of exhaust gas recirculation is applied. The higher degree of exhaust gas recirculation causes a further reduction of the formation of NOx during the combustion process and thus compliance with the lower limit for NOx emission set by the second emission standard, while suppressing the emission of excess amounts of soot particles is effected. due to the effects of injecting larger amounts of fuel for a given engine load.

The formation of soot caused by heavy exhaust gas recirculation is due to the combustion zone suffering from oxygen starvation, which limits the possibility of re-oxidation of already formed soot particles and also limits further oxidation of carbon monoxide to carbon dioxide. By using a fuel with a relatively low calorific value, a larger amount of fuel is needed to achieve a given energy output. The larger amount of fuel is injected into the cylinder charge present in the combustion chamber, and if the fuel injection occurs at high pressure the injection of a larger amount of fuel will cause more powerful stirring of the contents in the combustion chamber, and a larger mass of the cylinder charge will be entrained into the combustion zone. The larger volume of injected fuel in relation to the calorific value of the injected fuel thus causes an increased mixing of cylinder charge into the actual combustion zone, and this compensates for the lower oxygen content of the cylinder charge caused by the increased degree of exhaust gas recirculation.

Accordingly, the amount of oxygen actually needed for the combustion will be present in the combustion zone and the formation of soot will be suppressed or even avoided. Furthermore, the required limitation of formation of NOx is obtained due to the increased degree of exhaust gas recirculation whereby the limits of NOx Emission Control Area can be met. When the internal combustion engine is operated outside NOx Emission Control Areas the use of the first fuel with a relatively higher lower calorific value entails that it is possible to minimize the specific fuel consumption (in terms of weight of fuel per engine effect produced) , which is also an important environmental desire.

For a given engine load, fuel injection is initiated with a timing in the engine cycle which is earlier when the internal combustion engine is operating with the second fuel than when the internal combustion engine is operating with the first fuel. The second fuel with a lower calorific value than the first fuel can be injected in a larger amount than the first fuel and thus cause the same combustion effect in the combustion chamber, and the earlier initiation of fuel injection, when using the second fuel, allows the second fuel to be injected via the same fuel nozzle geometry as the injection of the first fuel, and yet obtain the same maximum pressure during the engine cycle. This simplifies the engine cylinder design. The cylinders could also be provided with more injectors, and one or more injectors could be in operation when the second fuel is used, or the individual injector could be embodied with adjustable injection area in the injection nozzle.

Preferably, said second lower calorific value of the second fuel is less than 90% of said first lower calorific value of the first fuel, and consequently a correspondingly larger volume of second fuel is injected for a given engine load.

In an embodiment of the second fuel, a mixture comprising a first component is the first fuel and at least one other component having a lower calorific value, which is lower that the lower calorific value of the first fuel. Severalby have obtained that change from the first fuel to the second fuel may be performed by mixing the at least one other component into a flow of the first fuel. It is also an advantage that storage of the types of fuel is simplified by using the first fuel as part of the second fuel.

In an embodiment the second fuel comprises an incombustible component. The incombustible component can be said to have at least one other component of the second fuel. An incombustible component has a lower calorific value of nil and is thus a very effective modifier of the calorific value of a mixture of a first component, which is combustible.

In an embodiment a change from the first fuel to the second fuel is performed gradually. This allows for a simple switch to the second fuel by gradually adding one or more other components to the first fuel in order to provide the mixture of the second fuel.

In an embodiment the first fuel comprises a liquid fuel and the second fuel comprises a fuel selected from a group comprising: distillate fuel emulsified with water, residual fuel emulsified with water, alcohols, ammonia, di-methyl ether, and mixtures thereof. This embodiment is advantageous for engines having liquid fuel injectors.

In another embodiment, the first fuel comprises a fuel gas and the second fuel comprises a gaseous fuel selected from a group comprising: boil-off gas with low calorific value, syngas, gas mixed with an inert gas, and mixtures thereof. This embodiment is advantageous for engines having fuel injectors based on gas injection, or dual fuel injectors injecting pilot fuel to cause ignition and then gas as the main fuel.

Liquid fuel or gaseous fuel is used in accordance with specifications of the internal combustion engine in question. In the case of a liquid fuel, water emulsified into a combustible constitutes an incombustible component of the second fuel. In the case of a gaseous fuel, an inert gas like nitrogen, which does not participate in the combustion, constitutes an incombustible component of the second fuel.

An embodiment of the internal combustion engine is a low speed, two-stroke crosshead diesel type internal combustion engine. Low speed engines are engines running at 100% engine load at rotational speeds in the range of 40 to 300 rpm, especially at rotational speeds in the range 40 to 250 rpm. The expression "diesel type" should be understood to mean enterprise engines operating according to the Diesel cycle, and the engines can as an example run on diesel fuel, heavy fuel oil, gas fuel such as methane or natural gas, or dual fuel, i.e. an auto-igniting pilot fuel and a non-auto-igniting main fuel.

In another embodiment the internal combustion engine is a medium speed, four-stroke internal combustion engine. A medium speed engine is an engine running at 100% engine load at rotational speeds in the 300 to 1200 rpm range, especially at rotational speeds in the 400 to 1000 rpm range.

In one embodiment, for a given engine load, the fuel injection is performed during a larger proportion of the engine cycle when the internal combustion engine is operating with the second fuel, than when the internal combustion engine is operating with the first fuel. The lower calorific value of the second fuel and the consequently greater amount of fuel needed to be injected per engine cycle in order achieve the same engine load can be made by injecting fuel during a larger proportion of the engine cycle, and thus for an extended period of time when the engine is operating at constant revolutions (rpm). Alternatively, the injectors can be provided with a larger injection area so that the larger volume of the second fuel can be injected with the same injection profile in relation to the crank angle as the injection profile for the first fuel.

Further, local terrestrial areas may be subject to varying standards for emission of NOx, etc. in accordance with actual meteorological conditions. Internal combustion engines located in such local terrestrial areas will accordingly at times operate in an environment with a first emission standard and at other times operate in another environment with a second, more strict emission standard for allowable emission of such polluting components in the exhaust gas due to the fact that the standard of said environment changes with the actual meteorological conditions. Such shifting of emission standards due to environmental variations at a specific geographical location may be of relevance to internal combustion engines operating as propulsion engine or auxiliary engine on vessels, but is even more relevant to internal combustion engines operating as prime movers in stationary power generating facilities. delivering electrical power to a grid via a generator powered by the internal combustion engine.

Examples of the present invention and embodiments thereof are described in more detail hereinafter with reference to the highly schematic drawing, in which

FIG. 1 illustrates in vertical section a cylinder in an internal combustion engine,

FIG. 2 is an example of a diagram for exhaust gas recirculation in the internal combustion engine of FIG. 1

FIG. 3 illustrates a combustion chamber in a cylinder, and an embodiment of a fuel supply system,

FIG. 4 illustrates a diagram of soot concentration as a function of exhaust gas recirculation, and

FIG. 5 illustrates how entrained air depends on the lower calorific value of the injected fuel.

The method of the present invention is relevant to internal combustion engines of two-stroke crosshead diesel engine type, such as engines of the make MAN Diesel & Turbo and exemplary types MC or ME, or engines of the make Wårtsilå and exemplary types X, RT-flex or RTA, or the Mitsubishi Heavy Industries make. An engine of this type is a large engine typically used as a main engine in a ship or as a stationary engine in a power plant. The cylinders can e.g. have a bore in the range from 25 cm to 120 cm, and the engine can e.g. have a power in the range from 3000 kW to 120,000 kW. Such engines are low speed engines with engine speeds ranging from 40 rpm to 250 rpm, or even up to 300 rpm. The method according to the present invention also relates to four-stroke diesel engines, such as engines of the make MAN Diesel and Turbo and exemplary types 32 / 44CR, 48 / 60DF, 51 / 60DF, V28-33D, or engines of the make Wårtsilå and exemplary types 20 to 64, and DF, which have engine speed eg in the range from 300 rpm to 1200 rpm.

In FIG. An exhaust valve 1 mounted in a cylinder cover at the top of an engine cylinder 6 is shown in the open position with the piston in the bottom dead center position (BDC) where scavenge air ports in the lower section of the cylinder allow inlet air - or an inlet air / gas mixture - from a scavenge air receiver 3 to flow into the cylinder in a swirling movement and expel combustion gas products (black arrows) out through the exhaust valve and into an exhaust gas receiver 7, from which the exhaust gas flow through the turbine part of a turbocharger 2. The compressor part of the turbocharger 2 sucks in inlet air (white arrows) and delivers compressed inlet air via a gas cooler 4 and a water mist catcher 5 to the scavenge air receiver 3.

In the following the same numerals are used for details of the same type, however for ease of explanation some numerals may be identified with letters a and b when they relate to details operating in parallel.

The engine is operated with exhaust gas recirculation (EGR). An example of a layout for this is shown in FIG. 2. Two turbochargers 2a, 2b are shown, but the engine may have only one turbocharger, or more than two, such as three, four or five turbochargers. The turbocharger 2a is a secondary turbocharger that can be taken out of operation by closing two control valves 13, one of which is located in the exhaust gas conduit upstream of the turbine part and the other located in the inlet air conduit downstream of the compressor party. The turbocharger 2b is a basic turbocharger. The secondary turbocharger can be in operation when the engine load is high and be taken out of operation when the engine load is low.

In the illustrated example the engine has six cylinders, and each cylinder delivers exhaust gas to exhaust gas receiver 7. The turbochargers 2a, 2b can be supplied with exhaust gas from the exhaust gas receiver. An exhaust gas recirculation conduit 10 from the exhaust gas receiver 7 has a shut-down valve 8 and an optional first scrubber 9 for removing undesired components from the exhaust gas before it is delivered to the inlet air conduit downstream of control valve 13. A second scrubber 11 may be located in between gas cooler 4 and water mist catcher 5a for further removal of undesired components from the recirculated exhaust gas. A blower 17 can deliver recirculated exhaust gas to the scavenge air receiver 3, such as at low engine load. An EGR blower 14 of greater capacity than blower 17 can deliver recirculated exhaust gas from water mist catcher 5a via a control valve 18 to the inlet air conduit from turbocharger 2b at a location downstream of gas cooler 4b. The recirculated exhaust gas will then pass both water mist catcher 5a and water mist catcher 5b before entering the scavenge air receiver 3.

An auxiliary blower 16 is connected to the inlet air conduit from turbocharger 2b, and auxiliary blower 16 can e.g. be used during engine startup at very low engine loads where the exhaust gas flow rate is too small to efficiently supply the turbochargers 2. The individual conduits supplying the scavenge air receiver is provided with a non-return valve 15. The six cylinder supplies with inlet air / gas from the scavenge air receiver are illustrated by arrows.

Exhaust gas recirculation can also be effected in other manners, such as in a layout where secondary turbocharger 2a has been left out together with control valves 13 and blower 17, and EGR blower 14 is connected to the inlet air conduit from turbocharger 2b at a location downstream of water mist catcher 5b. A piston 19 is reciprocating within the individual cylinder 6 during engine operation. As illustrated in FIG. 3 one or more fuel injectors 22 are located on the cylinder, such as mounted in the cylinder cover, in order to inject fuel directly into a combustion chamber 20 present in the cylinder above the piston. The fuel is delivered to the individual fuel injector via a fuel supply conduit 23 when a control device 24 delivers fuel to the injector. The control device 24 is via a signal line 25 in electronic communication with a control unit 26. The engine may have a single control unit or several control units, such as a cylinder control unit for the individual cylinder, and possibly one or more central control units. The fuel to the fuel injectors 22 is delivered from a fuel supply system. This delivery can take place in several different manners. One possibility is to provide the fuel at a relatively low pressure, such as a feed pressure in the range of 2 to 25 bar, and then use a high pressure fuel pump associated with the individual injector in order to deliver the fuel with the desired timing. in the engine cycle to the injector at a high pressure, such as 800 bar. The high pressure fuel pump can be of the Bosh type and it can be hydraulically actuated or cam shaft actuated. Another possibility is to provide the fuel at the high pressure required for injection to a common rail 31 from which the individual injector can be supplied by opening and closing a control valve.

The fuel supplied to the fuel injectors 22 has a composition depending on the environment in which the internal combustion engine is currently operating. A first fuel source 27 holds a first fuel having a first calorific value. A second fuel source 28 holds a second fuel or a fuel component having a second calorific value being lower than the first calorific value of the first fuel. A mixing unit 29 mixes the first fuel and the second fuel in accordance with control signals received through signal line 30 from control unit 26, or equivalent control units like a central control unit controlling the composition of the fuel and another local control unit controlling the operation or fuel injectors on the individual cylinder.

The first fuel is the fuel having the first calorific value. The second fuel is the fuel having the second calorific value. This second fuel can be supplied as a separated fuel entirely independent of the first fuel. However, the second fuel can also be a mixture, where the first fuel is utilized as a first component in the mixture of components for the second fuel, which first component is mixed with at least one other component having a lower calorific value than the first component.

The one other component can be an incombustible component, like water or an inert gas, and in both cases the incombustible component attributes to lowering the second lower calorific value of the second fuel. The first fuel can be heavy fuel oil having a lower calorific value of 40.9 MJ / kg, or a medium grade oil having a lower calorific value of 42.9 MJ / kg. The medium grade oil mixed with 25% water can be supplied as the second fuel and has a lower calorific value of 32.2 MJ / kg. The medium grade oil mixed with 40% water can be supplied as the second fuel and has a lower calorific value of 25.7 MJ / kg. In the case of an engine running on gas, the first fuel can be butanol having a lower calorific value of 33 MJ / kg, and the second fuel can be methanol having a lower calorific value of 19.5 MJ / kg, or a mixture of butanol with an inert gas like nitrogen, or ammonia having a lower calorific value of 18.6 MJ / kg.

When the internal combustion engine operates in an environment with a first emission standard, such as a maximum limit for NOx emissions of 14.4 g / kWh, the engine is operated on the first fuel, and a first degree of exhaust gas recirculation, such as 25 % recirculation. When the engine is subsequently operating in an environment having a second emission standard, such as a maximum limit for NOx emissions of 3.4 g / kWh, the engine is operated on the second fuel, and a second degree of exhaust gas recirculation, such as 50 % recirculation. The high degree of exhaust gas recirculation has the negative effect that soot formed during combustion in the combustion chamber is not removed again before the exhaust gas leaves the engine. If the combustion products are mixed with gas containing oxygen, the carbon monoxide will react with oxygen and carbon dioxide will be formed and soot removed.

The injection of the second fuel having the lower level of lower calorific value has the consequence that a larger volume of fuel has to be injected in order to meet the engine's requirement for fuel at a given engine load. The fuel injection may be set to start earlier in the operating cycle of the engine so that the larger amount gets time to be injected, or a larger injection nozzle area can be utilized, such as by injecting via four injectors instead of injecting via three injectors per cylinder. If fuel injection for instance is set to start at 2 ° crank angle before the top dead center (TDC) when the first fuel is injected, it can for instance be set to start at 5 ° crank angle before the top dead center (TDC) when the second fuel is injected. In this case, the timing of initiation of fuel injection is thus earlier in the engine cycle when the internal combustion engine is operating with the second fuel than when the internal combustion engine is operating with the first fuel. The duration of fuel injection can also be performed during a larger proportion of the engine cycle when the engine is operating on the second fuel. The duration can be longer, not only by initiating fuel injection earlier in the cycle, but also by ending the fuel injection later in the engine cycle, such as 3 ° crank angle later in the cycle when the internal combustion engine is operating with the second fuel than when the internal combustion engine is operating with the first fuel.

The formation of soot as a function of the degree of exhaust gas recirculation is illustrated in FIG. 4. The curve A shown in full line shows how the soot concentration can increase when exhaust gas recirculation exceeds 40%. The curve B shown in broken line shows the effect on resulting soot concentration by using the second fuel injected in larger volume than the first fuel. The larger volume and larger mass of the second fuel causes a higher degree of stirring of the contents in the combustion chamber by the fuel injection. The injected fuel entrains air from outside the combustion zone and brings this air into the combustion zone, thus also drawing oxygen contained in the air into the combustion zone where the oxygen acts to remove soot. The injected fuel has a certain energy content which can be expressed in kJ. In order to operate the engine at a certain engine load, fuel with a certain energy content has to be injected into the combustion chamber. The mass of air entrained (drawn) into the combustion zone per injected kJ of fuel energy content as a function of the lower calorific value in MJ / kg of the second fuel is illustrated as curve C in Fig. 5. The mass of air is seen to increase as the lower calorific value of the second fuel decreases.

The lower calorific value LCV of the second fuel can be calculated on the basis of a measurement of one parameter or more parameters when the fuel is stored in the fuel source, such as a fuel storage tank. By obtaining in this way a measure for the lower calorific value the latter may be stored in the control unit and used automatically for the control of the internal combustion engine. A number of different parameters may be measured in ways known per se to provide the lower calorific value of the fuel. It is also possible to measure one or more operating parameters on the engine, and to use this information to decide on the setting of the fuel components being mixed into the second fuel. Such operating parameter may e.g. involves measurement of the pressure variation within the at least one cylinder through a cycle. As an alternative, the lower calorific value may be used can be set manually to the control system of the internal combustion engine.

Details of the various embodiments described in the above may be combined into further embodiments within the scope of the patent claims.

Claims (12)

A method of operating an internal combustion engine having cylinders having a reciprocating piston in each cylinder and a combustion chamber above the piston, and at least one fuel injector which injects fuel directly into the combustion chamber above the piston, which engine is powered by exhaust gas -circulation, where the engine is operated at certain times in an environment with a first emission standard with a limit on emissions of pollutants with the exhaust gas, and where the engine is at other times operated in a different environment with a second, more stringent emission standard with a limit on emissions of pollutants. with the exhaust gas, characterized by (a) the engine is operated on a first fuel having a first lower calorific value and with a first degree of exhaust gas recirculation when operating in the environment with the first emission standard, and b) the engine is operated on a second fuel with another lower calorific value and with a second degree of exhaust gas recirculation when operating in other environments with the second, more stringent emission standard, where the second lower calorific value is lower than the first lower calorific value, and where the second degree of exhaust gas recirculation is greater than the first degree of exhaust gas recirculation, and that the fuel injection at a given engine load is initiated with a timing in the engine cycle which is earlier when the internal combustion engine is operated on the second fuel than when the internal combustion engine is operated on the first fuel. Process according to claim 1, characterized in that the second lower calorific value of the second fuel is less than 90% of the first lower calorific value of the first fuel. Method according to claim 1 or 2, characterized in that the second fuel is a mixture comprising as a first component the first fuel, and at least a second component with a lower calorific value which is less than the lower calorific value of the first fuel. Process according to any one of the preceding claims, characterized in that the second fuel comprises an incombustible component. Process according to one or more of the preceding claims, characterized in that a change from the first fuel to the second fuel is carried out gradually while the engine is running. Process according to one or more of the preceding claims, characterized in that the first fuel comprises a liquid fuel and the second fuel comprises a fuel selected from a group comprising: fuel distillate emulsified with water, residual fuel emulsified with water, alcohols, ammonia , dimethyl ether, and mixtures thereof. Process according to one or more of claims 1 to 5, characterized in that the first fuel comprises a fuel gas and the second fuel comprises a gaseous fuel selected from a group comprising: low-combustion vaporized gas, syngas, gas mixed with a inert gas, and mixtures thereof. Method according to one or more of the preceding claims, characterized in that the internal combustion engine is a slow-moving, two-stroke cross-head diesel-type internal combustion engine. Method according to one or more of claims 1 to 8, characterized in that the internal combustion engine is a medium-speed, four-stroke internal combustion engine. Method according to one or more of the preceding claims, characterized in that, for a given engine load, the fuel injection is performed during a larger proportion of the engine cycle when the internal combustion engine is operated on the second fuel than when the internal combustion engine is operated on the first fuel. Method according to one or more of the preceding claims, characterized in that the internal combustion engine is a stationary engine located at a particular terrestrial location and that the engine is operated at certain times in an environment with a first discharge standard and at other times is operated in an environment with a second one. , more stringent emission standards due to the current meteorological conditions. 12. A combustion engine with cylinders with a reciprocating piston in each cylinder and a combustion chamber over the piston, at least one fuel injector which injects fuel directly into the combustion chamber above the piston, at least one turbocharger, an exhaust gas recirculation line, an exhaust valve and an exhaust valve. a recirculation fan for supplying recirculated exhaust gas to a combustion engine intake air line, characterized in that the combustion engine control unit is configured to control the combustion engine according to the method of one or more of claims 1 to 11.