WO2023168477A2 - Method for operating a gas-powered internal combustion engine - Google Patents

Method for operating a gas-powered internal combustion engine Download PDF

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Publication number
WO2023168477A2
WO2023168477A2 PCT/AT2023/060069 AT2023060069W WO2023168477A2 WO 2023168477 A2 WO2023168477 A2 WO 2023168477A2 AT 2023060069 W AT2023060069 W AT 2023060069W WO 2023168477 A2 WO2023168477 A2 WO 2023168477A2
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WO
WIPO (PCT)
Prior art keywords
load
internal combustion
combustion engine
exhaust gas
air ratio
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PCT/AT2023/060069
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German (de)
French (fr)
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WO2023168477A3 (en
Inventor
Anton Arnberger
Admir ZUKANCIC
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Avl List Gmbh
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Publication of WO2023168477A2 publication Critical patent/WO2023168477A2/en
Publication of WO2023168477A3 publication Critical patent/WO2023168477A3/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/10—Introducing corrections for particular operating conditions for acceleration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0639—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
    • F02D19/0642—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
    • F02D19/0644—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions the gaseous fuel being hydrogen, ammonia or carbon monoxide
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05F—DEVICES FOR MOVING WINGS INTO OPEN OR CLOSED POSITION; CHECKS FOR WINGS; WING FITTINGS NOT OTHERWISE PROVIDED FOR, CONCERNED WITH THE FUNCTIONING OF THE WING
    • E05F1/00—Closers or openers for wings, not otherwise provided for in this subclass
    • E05F1/08—Closers or openers for wings, not otherwise provided for in this subclass spring-actuated, e.g. for horizontally sliding wings
    • E05F1/16—Closers or openers for wings, not otherwise provided for in this subclass spring-actuated, e.g. for horizontally sliding wings for sliding wings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/02—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with gaseous fuels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/02—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with gaseous fuels
    • F02D19/021—Control of components of the fuel supply system
    • F02D19/023—Control of components of the fuel supply system to adjust the fuel mass or volume flow
    • F02D19/024—Control of components of the fuel supply system to adjust the fuel mass or volume flow by controlling fuel injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0002—Controlling intake air
    • F02D41/0007—Controlling intake air for control of turbo-charged or super-charged engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0027—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures the fuel being gaseous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0065—Specific aspects of external EGR control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0203—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels characterised by the type of gaseous fuel
    • F02M21/0206—Non-hydrocarbon fuels, e.g. hydrogen, ammonia or carbon monoxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/022—Adding fuel and water emulsion, water or steam
    • F02M25/025—Adding water
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/022—Adding fuel and water emulsion, water or steam
    • F02M25/025—Adding water
    • F02M25/03—Adding water into the cylinder or the pre-combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2201/00—Constructional elements; Accessories therefor
    • E05Y2201/20—Brakes; Disengaging means; Holders; Stops; Valves; Accessories therefor
    • E05Y2201/218—Holders
    • E05Y2201/22—Locks
    • E05Y2201/221—Touch latches
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2201/00—Constructional elements; Accessories therefor
    • E05Y2201/40—Motors; Magnets; Springs; Weights; Accessories therefor
    • E05Y2201/404—Function thereof
    • E05Y2201/422—Function thereof for opening
    • E05Y2201/426—Function thereof for opening for the initial opening movement
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2201/00—Constructional elements; Accessories therefor
    • E05Y2201/40—Motors; Magnets; Springs; Weights; Accessories therefor
    • E05Y2201/499—Spring tensioners; Tension sensors
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2600/00—Mounting or coupling arrangements for elements provided for in this subclass
    • E05Y2600/10—Adjustable
    • E05Y2600/12—Adjustable by manual operation
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2600/00—Mounting or coupling arrangements for elements provided for in this subclass
    • E05Y2600/10—Adjustable
    • E05Y2600/30—Adjustment motion
    • E05Y2600/33—Stepwise motion
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF
    • E05Y2900/00—Application of doors, windows, wings or fittings thereof
    • E05Y2900/20—Application of doors, windows, wings or fittings thereof for furniture, e.g. cabinets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B39/00—Component parts, details, or accessories relating to, driven charging or scavenging pumps, not provided for in groups F02B33/00 - F02B37/00
    • F02B39/02—Drives of pumps; Varying pump drive gear ratio
    • F02B39/08—Non-mechanical drives, e.g. fluid drives having variable gear ratio
    • F02B39/10—Non-mechanical drives, e.g. fluid drives having variable gear ratio electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M2026/001—Arrangements; Control features; Details
    • F02M2026/009—EGR combined with means to change air/fuel ratio, ignition timing, charge swirl in the cylinder

Definitions

  • the invention relates to a method for operating a gas-operated internal combustion engine, preferably with hydrogen as fuel, wherein the internal combustion engine is operated in a first operation when load requirements only change over the long term, in which the air ratio is reduced at higher load requirements.
  • Such internal combustion engines are often designed to operate a vehicle such as a commercial vehicle.
  • nitrogen oxides also abbreviated as N0 temperatures can be observed, while the formation of nitrogen oxides below these temperatures is low or hardly significant.
  • Preventing nitrogen oxide emissions therefore means conducting the combustion process largely outside the temperature window of NO x formation.
  • the combustion temperature and thus the NO X raw emissions are directly related, among other things, to the air ratio (lambda).
  • An additional challenge here is to achieve the desired lower air ratio value as quickly as possible in order to achieve the desired dynamics in the to meet load requirements.
  • reaching the target value for the air ratio can take up to several seconds due to the inertia of the charging components and that of the flowing gases.
  • a hydrogen internal combustion engine i.e. an internal combustion engine that burns hydrogen as fuel and/or is supplied with at least one fuel that includes hydrogen.
  • an internal combustion engine that is operated with a natural gas-hydrogen mixture as fuel.
  • the hydrogen-powered spark-ignited internal combustion engine can make a significant contribution to the de-carbonization of the mobility sector through its CO2-free exhaust and the absence of carbon-based pollutants.
  • the only relevant pollutant component remains increased nitrogen oxide emissions, which, depending on the engine's area of application, can be reduced through suitable operating strategies in combination with different peripheral technologies across the entire engine map.
  • nitrogen oxides can be reduced (i.e. freed from oxygen). Accordingly, it can be provided that nitrogen oxides are removed from the exhaust gas via a 3-way catalytic converter and/or - especially in superstoichiometric conditions - via selective catalytic reduction (SCR) or an NO x storage device.
  • SCR selective catalytic reduction
  • the last two measures in particular enable a reduction even in an oxygen-rich atmosphere.
  • additional facilities are costly, consume space and require maintenance.
  • DE 10 2018 122 963 A1 discloses a method in which exhaust gas recirculation is carried out at higher load requirements. This is also provided for in JP H0610772 A and DE 10 2019 213 132 Al and DE 10 321 793 Al. In the higher load range, NO X production is reduced. However, rapid load changes can still lead to higher nitrogen oxide emissions if they occur in the lower load range.
  • EP 1 754 874 A1 also shows such a method, in which a change is made between different operating states with different exhaust gas recirculation depending on the absolute level of the torque requirement.
  • the object of the invention is to provide a method in which dynamic torque provision is possible and at the same time nitrogen oxide production is kept as low as possible.
  • the torque provided can still be adjusted during the first operation using the air ratio, since nitrogen oxide emissions are already low there.
  • Such a first operation can therefore also be referred to as stationary operation, since the required torque change per time is low.
  • the second operation however, high required torque changes per time occur. This second operation can therefore also be referred to as dynamic operation.
  • the invention depends on the change in the load requirement per unit of time whether work is carried out in the first operation or in the second operation, i.e. on the first derivative or the gradient of the load requirement.
  • the change in the load requirement per unit of time is high, while in the case of long-term changes in the load requirement, the change in the load requirement per unit of time is correspondingly small.
  • a short-term increase in load corresponds to a high positive gradient in load demand.
  • a long-term changing load requirement corresponds to a low gradient of the load requirement.
  • the second operation ensures that little nitrogen oxide is produced even when a high torque is spontaneously provided.
  • the recirculated exhaust gas as an inert additional heat capacity, can lower the combustion temperature and thus reduce raw NO X emissions.
  • the lower boost pressure requirement results in a significantly faster increase in load, and raw NOx emissions remain low despite the rapid increase in load. It also protects against combustion anomalies such as pre-ignition and knocking and regulates the burning speed.
  • the minimum required air ratio is usually 1.75 to 1.90 if the maximum raw nitrogen oxide emissions must be kept below 10 g/kWh. If the maximum raw nitrogen oxide emissions are to be kept below 5 g/kWh, the required minimum air ratio value is normally in the range between 1.90 g/kWh and 2.00 g/kWh.
  • the required minimum air ratio value may also be determined by the exhaust gas aftertreatment used. If there is a requirement to limit the CO2 emissions converted by the reducing agent (aqueous urea solution, also AdBlue or DEF) in the SCR catalytic converter (the goal of a CO2-free drive), the maximum nitrogen oxide emissions must generally be in a range between 1- 2 g/kWh, so the required minimum air ratio value can also be 2.3 up to 2.6.
  • the reducing agent aqueous urea solution, also AdBlue or DEF
  • the exhaust gas recirculation rate is increased during the first operation. This can be useful - permanently or temporarily - particularly in certain situations such as a particularly high torque requirement. Alternatively, it can also be provided that the exhaust gas recirculation rate remains essentially the same during the first operation.
  • Long-term changing load requirements are those requirements in which the load requirement does not change or the change in the load requirement is so slow that the actually possible load change corresponds to the requirement and the minimum air ratio value required for stationary engine operation does not have to be undershot.
  • a long-term load increase occurs when, despite a change in the effective mean pressure over time, the current boost pressure or the boost pressure that the internal combustion engine can provide at short notice is sufficient to achieve the current minimum air ratio (or minimum dilution rate). can.
  • a long-term load requirement only a very small amount of nitrogen oxides is produced even when full load is reached. Typically this is a substantial change in load over a period of around 6 seconds or more.
  • Such long-term load requirements usually arise during steady operation such as highway driving or cross-country driving.
  • Short-term changing load requirements are situations in which the requirement changes so quickly that the minimum air ratio required for stationary engine operation must be undercut in order to meet the desired load change. In practical terms, this means that the engine's boost pressure reserve is too low to meet the current load requirement. In other words, there is a short-term changing load requirement if the desired temporal change in the effective mean pressure is so high that the currently available boost pressure, or the boost pressure that the internal combustion engine can provide at short notice is not sufficient to supply the internal combustion engine with the currently required minimum air ratio (or minimum dilution rate). A significantly larger torque is therefore required within a short time, usually within a few seconds (less than 6 seconds) or even fractions of a second. Such load requirements arise in particular when driving in an urban area or when a vehicle is in stop-and-go operation.
  • Minimum air ratio and minimum dilution rate do not necessarily have to be the same under the same load conditions and depend on how the dilution occurs (e.g. lean operation, exhaust gas recirculation, water injection and other factors).
  • a long-term load increase at a brake mean effective pressure (BMEP) greater than or equal to 5 bar usually occurs when the change over time in the effective mean pressure is less than 4.0 bar, preferably less than 3.5 bar per second.
  • BMEP brake mean effective pressure
  • BMEP brake mean effective pressure
  • the change in BMEP over time can be higher.
  • the numbers above may vary depending on engine size, speed and thermodynamic design of the internal combustion engine.
  • the air ratio also called lambda, is the ratio of the fresh air mass introduced into a combustion chamber of the internal combustion engine for a combustion process by the product of the fuel mass introduced into the combustion chamber for the combustion process with the stoichiometric air requirement of the fuel:
  • Air ratio fresh air quantity / (fuel quantity x stoichiometric air requirement)
  • the stoichiometric air requirement is a ratio that indicates how much air is necessary to burn the fuel in question stoichiometrically.
  • the load requirement refers to the torque requirement that is placed on the internal combustion engine at a specific moment.
  • the exhaust gas recirculation rate is the rate that results from the mass of exhaust gas recirculated into the combustion chamber, divided by the sum of the fresh air mass introduced and the fuel mass introduced:
  • Exhaust gas recirculation rate amount of exhaust gas recirculated / (amount of fresh air + amount of fuel)
  • the internal combustion engine can be operated with external (PFI - Port Fuel Injection) and/or with internal mixture formation (DI - Direct Injection).
  • the exhaust gas recirculation can take place through internal and/or external exhaust gas recirculation.
  • first and second operations In addition to the first and second operations, other operations or operating modes can also be provided. It can also make sense for the internal combustion engine, under certain conditions, to be operated in an operation that is not the first operation (for example the second operation), even when load requirements only change over the long term, and/or for the internal combustion engine to operate under certain conditions even when the load increases for a short time is operated in a company that is not the second company. This can be the case, for example, if it is clear based on the driving history or sensor data that the vehicle is in an urban area where short-term load increases are very likely to occur at shorter intervals of several seconds to minutes.
  • the air ratio is at least 1.75 and preferably at least 2 and/or at most 3.5 and preferably at most 3 when the load requirement only changes over the long term/in the first operation. This ensures that as little nitrogen oxide as possible is produced.
  • the exhaust gas recirculation rate is increased to at least 10%, preferably at least 20% and particularly preferably at least 30%, in the event of a short-term increase in load in the second operation.
  • a particularly high exhaust gas recirculation rate such as one increased by 30%, is advantageous; with regard to a particularly rapid increase in load, a lower exhaust gas recirculation rate, such as one increased by 10% to 20%, is particularly advantageous.
  • the air ratio is reduced to a value below 1.5, preferably to a value below 1.2, in the event of a short-term increase in load in the second operation.
  • the low air ratio enables maximum NOx reduction in the recirculated exhaust gas as well as low boost pressure requirements.
  • the low boost pressure requirement enables an accelerated increase in load.
  • the exhaust gas recirculation rate is increased by at least 10 percentage points, preferably at least 20 percentage points and particularly preferably at least 30 percentage points, in the event of a short-term load increase in the second operation.
  • An increase of percentage points means that the exhaust gas recirculation rate increases by the same percentage, for example an increase of 10 percentage points from 5% to 15%.
  • exhaust gas recirculation takes place during the first operation.
  • exhaust gas recirculation with a low exhaust gas recirculation rate makes sense here, for example in the range of less than 10% or less than 5%.
  • fresh air is compressed and preferably cooled via a turbocharger before being introduced into at least one combustion chamber of the internal combustion engine.
  • the boost pressure can be kept as high as possible and sufficient torque can be provided. Cooling allows the combustion temperature to be kept low, thereby reducing nitrogen oxide emissions.
  • the exhaust gas recirculation takes place via a high-pressure exhaust gas recirculation and the recirculated exhaust gas is preferably cooled before being introduced into the combustion chamber. This enables a particularly high boost pressure relief.
  • water is introduced into at least one combustion chamber, but preferably in all combustion chambers, of the internal combustion engine and is preferably injected directly into the combustion chamber.
  • the water can be mixed with the fresh air and/or fuel upstream of the inlet valve or the water can be injected directly into the combustion chamber.
  • a water injection that can be applied according to the cycle also has a lowering effect on the combustion temperature by removing heat from the combustion chamber for the phase transition (enthalpy of vaporization) of the water introduced and thus reduces NOx raw emissions.
  • water is condensed out of the exhaust gas and is particularly preferably used for water injection. This is particularly useful for hydrogen-powered internal combustion engines.
  • the boost pressure can be increased in the first operation with higher load requirements using an additional pressure source, preferably driven by an electric motor.
  • the electric motor can, for example, drive a compressor which compresses or additionally compresses the fresh air or the fresh air/fuel mixture before it is introduced into the combustion chamber (for example to form a turbocharger).
  • control times of at least one valve of the internal combustion engine are changed in the first operation with higher load requirements.
  • the control time adjustment makes it possible to influence both the air mass available to the process and the internally recirculated or remaining exhaust gas mass (internal exhaust gas recirculation) in order to influence the combustion temperature and thus the raw nitrogen oxide emissions. This measure can also be applied in the second operation.
  • valve lift height of at least one valve of the internal combustion engine is changed in the first operation with higher load requirements.
  • This measure can also be used in the second operation.
  • further measures to reduce nitrogen oxide emissions can also be taken during the first operation.
  • these measures can be the water introduction described.
  • 1a shows a diagram of the NO x production as a function of the air ratio in a process according to the prior art
  • Fig. lb is a diagram of the engine load as a function of time according to the method from Fig. la;
  • FIG. 2a shows a diagram of NOx production as a function of the air ratio in a method according to the invention in one embodiment
  • Fig. 2b is a diagram of the engine load as a function of time according to the method from Fig. 2a.
  • Fig. 1 the production of nitrogen oxides is plotted as a function of the air ratio during operation of a vehicle according to the prior art.
  • the associated exhaust gas recirculation rate is plotted below as a function of the air ratio, which remains the same throughout at around 2%.
  • NO Fig. lb shows the engine load, i.e. the output torque of the internal combustion engine, over time during the process if there is a short-term increase in load.
  • Fig. 2a the same diagram is shown, but expanded by a branch, which shows the NOx emission as a function of the air ratio when an exhaust gas recirculation behavior according to the invention (also expanded in the lower part of the diagram) is applied.
  • Fig. 2b the same load requirement curve is present as in Fig. lb, the behavior at point 1 is the same.
  • the load requirement increases in the short term, the air ratio is also significantly reduced.
  • the exhaust gas recirculation rate is increased from 2% by approximately 26 percentage points to approximately 28%. As a result, a significantly lower combustion temperature is achieved and there is only a raw NO X emission of around 2 g/kWh (point 2a).
  • the boost pressure can be adjusted accordingly and a higher air ratio of around 1.8 can be set in order to produce as little nitrogen oxide, i.e. NOx, as possible, but still operate the internal combustion engine as efficiently as possible and in a first operation with low, essentially constant Return exhaust gas recirculation (point 3).

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Abstract

The invention relates to a method for operating a gas-powered internal combustion engine, preferably with hydrogen as the fuel, wherein, with load requirements changing only in the long term, the internal combustion engine is operated in a first operating mode, in which the air ratio is lowered with a higher load requirement, characterised in that, with a short-term load increase, the internal combustion engine is operated in a second operating mode, in which the air ratio is significantly lowered (preferably air ratio = 1) and the exhaust gas recirculation rate is increased with a higher load requirement.

Description

Verfahren zum Betreiben einer gasbetriebenen BrennkraftmaschineMethod for operating a gas-powered internal combustion engine
Die Erfindung betrifft ein Verfahren zum Betreiben einer gasbetriebenen Brennkraftmaschine, vorzugsweise mit Wasserstoff als Kraftstoff, wobei die Brennkraftmaschine bei sich nur langfristig ändernden Lastanforderungen in einem ersten Betrieb betrieben wird, bei dem das Luftverhältnis bei höherer Lastanforderung abgesenkt wird. The invention relates to a method for operating a gas-operated internal combustion engine, preferably with hydrogen as fuel, wherein the internal combustion engine is operated in a first operation when load requirements only change over the long term, in which the air ratio is reduced at higher load requirements.
Solche Brennkraftmaschinen werden oft zum Betreiben eines Fahrzeugs wie eines Nutzfahrzeugs entwickelt. Such internal combustion engines are often designed to operate a vehicle such as a commercial vehicle.
Unter der Voraussetzung ausreichenden Vorhandenseins der Reaktanden Stickstoff und Sauerstoff entstehen Stickoxide (abgekürzt auch N0x, die beiden wichtigsten sind NO oder NO2) im motorischen Prozess in nennenswerter Menge oberhalb der sogenannten NOx-Bildungstemperatur, ab der eine starke Zunahme der Emissionen hin zu höheren Temperaturen zu beobachten ist, während die Stick- oxidbildung unterhalb dieser Temperaturen gering oder kaum nennenswert ist. Stickoxidemissionen verhindern bedeutet demnach den Verbrennungsprozess weitgehend außerhalb des Temperaturfensters der NOx-Bildung zu führen. Die Verbrennungstemperatur und damit die NOX Rohemission hängt unter anderem direkt mit dem Luftverhältnis (Lambda) zusammen. Assuming there is sufficient presence of the reactants nitrogen and oxygen, nitrogen oxides (also abbreviated as N0 temperatures can be observed, while the formation of nitrogen oxides below these temperatures is low or hardly significant. Preventing nitrogen oxide emissions therefore means conducting the combustion process largely outside the temperature window of NO x formation. The combustion temperature and thus the NO X raw emissions are directly related, among other things, to the air ratio (lambda).
Um die NOX Rohemissionen auf einem möglichst geringen Niveau zu halten, werden gasbetriebene Brennkraftmaschinen in einem möglichst großen Bereich mit einem mageren Verbrennungsprinzip betrieben. Unter Einsatz konventioneller Aufladetechnologie wird es allerdings bei steigender Last notwendig sein das Luftverhältnis zu senken, um die erforderliche motorische Leistung darstellen zu können. Bei langfristigen Steigerungen der Lastanforderung ist dies wenig problematisch, da, ohne wesentlich zu übersteuern, das Luftverhältnis langsam verringert und der Ladedruck angepasst werden kann und jederzeit das notwendige Drehmoment bereitgestellt wird. In order to keep NO However, when using conventional supercharging technology, it will be necessary to reduce the air ratio as the load increases in order to be able to achieve the required engine power. In the case of long-term increases in the load requirement, this is not a problem because the air ratio can be slowly reduced and the boost pressure can be adjusted without significantly oversteering, and the necessary torque can be provided at any time.
Insbesondere eine kurzfristige Steigerung der Lastanforderung kann aber dazu führen, dass zumindest kurzfristig ins Temperaturfenster der NOX Bildung eingetreten wird, um das notwendige Drehmoment bereitzustellen. Dies führt dazu, dass die NOX Rohemissionen unter diesen Bedingungen stark steigen. In particular, a short-term increase in the load requirement can lead to the temperature window of NO X formation being entered, at least briefly, in order to provide the necessary torque. This causes NOx raw emissions to rise sharply under these conditions.
Eine zusätzliche Herausforderung hier ist es, den gewünschten niedrigeren Luft- verhältnis-Wert möglichst schnell zu erreichen, um die gewünschte Dynamik in der Lastanforderung zu erfüllen. Je nach Ausführung und Peripherie der Brennkraftmaschine kann die Erreichung des Zielwertes für das Luftverhältnis aufgrund der Trägheit der Aufladekomponenten sowie jener der strömenden Gase bis zu mehrere Sekunden dauern. An additional challenge here is to achieve the desired lower air ratio value as quickly as possible in order to achieve the desired dynamics in the to meet load requirements. Depending on the design and peripherals of the internal combustion engine, reaching the target value for the air ratio can take up to several seconds due to the inertia of the charging components and that of the flowing gases.
Vorzugsweise handelt es sich um eine Wasserstoffbrennkraftmaschine, also um eine Brennkraftmaschine, die Wasserstoff als Kraftstoff verbrennt und/oder die mit zumindest einem Kraftstoff versorgt wird, der Wasserstoff umfasst. Also beispielsweise eine solche Brennkraftmaschine, die mit einem Erdgas-Wasserstoffgemisch als Kraftstoff betrieben wird. It is preferably a hydrogen internal combustion engine, i.e. an internal combustion engine that burns hydrogen as fuel and/or is supplied with at least one fuel that includes hydrogen. For example, such an internal combustion engine that is operated with a natural gas-hydrogen mixture as fuel.
Insbesondere der wasserstoffbetriebene fremdgezündete Verbrennungsmotor kann einen wesentlichen Beitrag zur De-Karbonisierung des Mobilitätssektors leisten durch sein CO2-freies Abgas und das Fehlen kohlenstoffbasierter Schadstoffe. Als einzig relevante Schadstoffkomponente verbleibt erhöhter Stickoxidaus- stoß, der je nach Anwendungsgebiet des Motors durch geeignete Betriebsstrategien in Kombination mit unterschiedlichen peripheren Technologien im gesamten motorischen Kennfeld reduziert werden kann. In particular, the hydrogen-powered spark-ignited internal combustion engine can make a significant contribution to the de-carbonization of the mobility sector through its CO2-free exhaust and the absence of carbon-based pollutants. The only relevant pollutant component remains increased nitrogen oxide emissions, which, depending on the engine's area of application, can be reduced through suitable operating strategies in combination with different peripheral technologies across the entire engine map.
In einer Abgasnachbehandlung können Stickoxide reduziert (also von Sauerstoff befreit) werden. Demgemäß kann vorgesehen sein, dass dem Abgas über einen 3- Weg- Katalysator, und/oder - insbesondere bei überstöchiometrischen Bedingungen - über selektive katalytische Reduktion (SCR) oder einen NOx-Speicher Stickoxiden entzogen werden. Insbesondere die beiden letzten Maßnahmen ermöglichen eine Reduktion auch in sauerstoffreicher Atmosphäre. Jedoch sind solche zusätzlichen Einrichtungen kostspielig, verbrauchen Platz und müssen gewartet werden. In exhaust gas aftertreatment, nitrogen oxides can be reduced (i.e. freed from oxygen). Accordingly, it can be provided that nitrogen oxides are removed from the exhaust gas via a 3-way catalytic converter and/or - especially in superstoichiometric conditions - via selective catalytic reduction (SCR) or an NO x storage device. The last two measures in particular enable a reduction even in an oxygen-rich atmosphere. However, such additional facilities are costly, consume space and require maintenance.
Die DE 10 2018 122 963 Al offenbart ein Verfahren, bei dem bei höherer Lastanforderung eine Abgasrückführung durchgeführt wird. Dies sieht auch die JP H0610772 A und die DE 10 2019 213 132 Al sowie die DE 10 321 793 Al vor. Dabei wird im höheren Lastbereich die NOX- Produktion vermindert. Jedoch kann es bei schnellem Lastwechsel trotzdem zu höheren Stickoxidemissionen kommen, wenn diese im unteren Lastbereich auftreten. DE 10 2018 122 963 A1 discloses a method in which exhaust gas recirculation is carried out at higher load requirements. This is also provided for in JP H0610772 A and DE 10 2019 213 132 Al and DE 10 321 793 Al. In the higher load range, NO X production is reduced. However, rapid load changes can still lead to higher nitrogen oxide emissions if they occur in the lower load range.
Auch die EP 1 754 874 Al zeigt ein solches Verfahren, bei der zwischen verschiedenen Betriebszuständen mit unterschiedlicher Abgasrückführung abhängig von der absoluten Höhe der Drehmomentanforderung gewechselt wird. EP 1 754 874 A1 also shows such a method, in which a change is made between different operating states with different exhaust gas recirculation depending on the absolute level of the torque requirement.
Der Stand der Technik schlägt also verschiedene Verfahren vor, bei der der absolute Wert der Lastanforderung zur Regelung der Abgasrückführung herangezogen wird. Wie oben beschrieben führt dies aber nicht zu einer wirksamen Reduktion der NOx-Produktion in allen Fällen. Bei einem abrupten Anstieg der Lastanforderung innerhalb eines niedrigen Lastanforderungsbereichs kann es nach wie vor zu einer hohen Stickoxidemission kommen. The prior art therefore suggests various methods in which the absolute value of the load requirement is used to regulate exhaust gas recirculation. However, as described above, this does not lead to an effective reduction NOx production in all cases. If the load demand increases abruptly within a low load demand range, high nitrogen oxide emissions can still occur.
Aufgabe der Erfindung ist, ein Verfahren bereitzustellen, bei dem eine dynamische Drehmomentbereitstellung ermöglicht und gleichzeitig die Stickoxidproduktion möglichst gering gehalten wird. The object of the invention is to provide a method in which dynamic torque provision is possible and at the same time nitrogen oxide production is kept as low as possible.
Dies wird erfindungsgemäß dadurch erreicht, dass die Brennkraftmaschine bei kurzfristiger Lasterhöhung in einem zweiten Betrieb betrieben wird, bei dem das Luftverhältnis bei höherer Lastanforderung abgesenkt wird und die Abgasrückführungsrate erhöht wird. This is achieved according to the invention in that the internal combustion engine is operated in a second operation during a short-term increase in load, in which the air ratio is reduced at higher load requirements and the exhaust gas recirculation rate is increased.
Bei sich nur langsam ändernden oder gar gleichbleibenden Lastanforderungen kann nach wie vor im Zuge des ersten Betriebs die Einstellung des bereitgestellten Drehmoments mit Hilfe des Luftverhältnisses erfolgen, da dort die Stickoxidemission ohnehin gering ist. Ein solcher erster Betrieb kann damit auch als stationärer Betrieb bezeichnet werden, da die geforderte Drehmomentänderung pro Zeit niedrig ist. Im zweiten Betrieb hingegen treten hohe geforderte Drehmomentänderungen pro Zeit auf. Damit kann dieser zweite Betrieb auch als dynamischer Betrieb bezeichnet werden. If the load requirements change only slowly or even remain the same, the torque provided can still be adjusted during the first operation using the air ratio, since nitrogen oxide emissions are already low there. Such a first operation can therefore also be referred to as stationary operation, since the required torque change per time is low. In the second operation, however, high required torque changes per time occur. This second operation can therefore also be referred to as dynamic operation.
Es kommt also erfindungsgemäß auf die Änderung der Lastanforderung pro Zeiteinheit an, ob im ersten Betrieb oder im zweiten Betrieb gearbeitet wird, also auf die erste Ableitung oder der Gradient der Lastanforderung. Bei einer kurzfristigen oder abrupten Erhöhung der Lastanforderung ist die Änderung der Lastanforderung pro Zeiteinheit hoch, während bei langfristigen Änderungen der Lastanforderung die Änderung der Lastanforderung pro Zeiteinheit entsprechend klein ist. In diesem Sinne entspricht eine kurzfristige Lasterhöhung einem hohen positiven Gradienten der Lastanforderung. Positiv in dem Sinne, dass die Lastanforderung steigt und nicht absinkt. Dem folgend entspricht eine sich langfristig ändernde Lastanforderung einem niedrigen Gradienten der Lastanforderung. According to the invention, it depends on the change in the load requirement per unit of time whether work is carried out in the first operation or in the second operation, i.e. on the first derivative or the gradient of the load requirement. In the case of a short-term or abrupt increase in the load requirement, the change in the load requirement per unit of time is high, while in the case of long-term changes in the load requirement, the change in the load requirement per unit of time is correspondingly small. In this sense, a short-term increase in load corresponds to a high positive gradient in load demand. Positive in the sense that the load requirement increases rather than decreases. Accordingly, a long-term changing load requirement corresponds to a low gradient of the load requirement.
Durch den zweiten Betrieb wird erreicht, dass auch bei spontaner Bereitstellung eines hohen Drehmoments wenig Stickoxid entsteht. Durch das rückgeführte Abgas, als inerte zusätzliche Wärmekapazität, kann die Verbrennungstemperatur abgesenkt und somit die NOX Rohemission reduziert werden. Der niedrigere Ladedruckbedarf bringt einen deutlich schnelleren Lastanstieg mit sich, und die NOX Rohemissionen bleiben trotz des schnellen Lastanstiegs niedrig. Dazu schützt er noch vor Verbrennungsanomalien wie Vorentflammungen und Klopfen und regelt die Brenngeschwindigkeit. Im Fall eines Wasserstoffmotors liegt der geforderte Mindestwert des Luftverhältnisses in der Regel bei 1,75 bis 1,90, falls die maximalen Stickoxid Rohemissionen unter 10 g/kWh gehalten werden müssen. Falls die maximalen Stickoxid Rohemissionen unter 5 g/kWh gehalten werden sollen, so liegt der geforderte Minimalwert an Luftverhältnis normalerweise im Bereich zwischen 1,90 g/kWh und 2,00 g/kWh. Der geforderte Minimalwertwert an Luftverhältnis ist u.U. auch durch die verwendete Abgasnachbehandlung bestimmt. Falls eine Anforderung besteht, dass die durch das Reduktionsmittel (wässrige Harnstofflösung, auch AdBlue oder DEF) im SCR Katalysator umgewandelte CO2 Emission zu beschränken (Ziel eines CO2- freier Antriebs) so muss die maximale Stickoxid Emission in der Regel in einem Bereich zwischen 1-2 g/kWh liegen, damit kann der geforderte Minimalwert an Luftverhältnis auch 2,3 bis zu 2,6 betragen. The second operation ensures that little nitrogen oxide is produced even when a high torque is spontaneously provided. The recirculated exhaust gas, as an inert additional heat capacity, can lower the combustion temperature and thus reduce raw NO X emissions. The lower boost pressure requirement results in a significantly faster increase in load, and raw NOx emissions remain low despite the rapid increase in load. It also protects against combustion anomalies such as pre-ignition and knocking and regulates the burning speed. In the case of a hydrogen engine, the minimum required air ratio is usually 1.75 to 1.90 if the maximum raw nitrogen oxide emissions must be kept below 10 g/kWh. If the maximum raw nitrogen oxide emissions are to be kept below 5 g/kWh, the required minimum air ratio value is normally in the range between 1.90 g/kWh and 2.00 g/kWh. The required minimum air ratio value may also be determined by the exhaust gas aftertreatment used. If there is a requirement to limit the CO2 emissions converted by the reducing agent (aqueous urea solution, also AdBlue or DEF) in the SCR catalytic converter (the goal of a CO2-free drive), the maximum nitrogen oxide emissions must generally be in a range between 1- 2 g/kWh, so the required minimum air ratio value can also be 2.3 up to 2.6.
Es kann dabei auch vorgesehen sein, dass während des ersten Betriebs die Abgasrückführungsrate erhöht wird. Insbesondere in bestimmten Situationen wie einer besonders hohen Drehmomentanforderung kann dies - dauerhaft oder vorübergehend - sinnvoll sein. Alternativ kann auch vorgesehen sein, dass während des ersten Betriebs die Abgasrückführungsrate im Wesentlichen gleich bleibt. It can also be provided that the exhaust gas recirculation rate is increased during the first operation. This can be useful - permanently or temporarily - particularly in certain situations such as a particularly high torque requirement. Alternatively, it can also be provided that the exhaust gas recirculation rate remains essentially the same during the first operation.
Dabei sind mit sich langfristig ändernden Lastanforderungen solche Anforderungen gemeint, bei der sich die Lastanforderung nicht ändert oder die Änderung der Lastanforderung so langsam ist, dass die tatsächlich mögliche Laständerung der Anforderung entspricht sowie der für den stationären Motorbetrieb geforderte Mindestwert an Luftverhältnis nicht unterschritten werden muss. Mit anderen Worten liegt also eine langfristige Lasterhöhung dann vor, wenn trotz zeitlicher Änderung des effektiven Mitteldrucks der aktuelle Ladedruck oder der Ladedruck, den die Brennkraftmaschine kurzfristig bereitstellen kann, ausreichend ist, um den aktuellen Mindestwert an Luftverhältnis (bzw. Mindest-Verdünnungsrate) erreichen zu können. Bei einer solchen langfristigen Lastanforderung wird auch bei Erreichen der Volllast nur eine sehr geringe Menge an Stickoxiden produziert. In der Regel handelt es sich dabei um eine substanzielle Laständerung in einem Zeitraum von etwa 6 Sekunden oder mehr. Solche langfristigen Lastanforderungen stellen sich meist bei gleichmäßigem Betrieb wie Autobahnfahrten oder Überlandfahrten ein.Long-term changing load requirements are those requirements in which the load requirement does not change or the change in the load requirement is so slow that the actually possible load change corresponds to the requirement and the minimum air ratio value required for stationary engine operation does not have to be undershot. In other words, a long-term load increase occurs when, despite a change in the effective mean pressure over time, the current boost pressure or the boost pressure that the internal combustion engine can provide at short notice is sufficient to achieve the current minimum air ratio (or minimum dilution rate). can. With such a long-term load requirement, only a very small amount of nitrogen oxides is produced even when full load is reached. Typically this is a substantial change in load over a period of around 6 seconds or more. Such long-term load requirements usually arise during steady operation such as highway driving or cross-country driving.
Unter sich kurzfristig ändernden Lastanforderungen sind solche Situationen gemeint, bei denen sich die Anforderung so schnell ändert, dass der für den stationären Motorbetrieb geforderte Mindestwert an Luftverhältnis unterschritten werden muss, um dem Laständerungswunsch zu entsprechen. Praktisch bedeutet das, die Ladedruckreserve des Motors ist zu gering um dem aktuellen Lastwunsch zu entsprechen. Mit anderen Worten liegt also eine sich kurzfristig ändernde Lastanforderung vor, wenn die gewünschte zeitliche Änderung des effektiven Mitteldrucks so hoch ist, dass der aktuell zur Verfügung stehende Ladedruck, beziehungsweise der Ladedruck den die Brennkraftmaschine kurzfristig bereitstellen kann, nicht ausreicht um die Brennkraftmaschine mit dem aktuell geforderten Mindestluftverhältnis (oder Mindest-Verdünnungsrate) zu versorgen. Es wird also ein wesentlich größeres Drehmoment innerhalb kurzer Zeit benötigt, in der Regel innerhalb von wenigen Sekunden (kleiner 6 Sekunden) oder gar Sekundenbruchteilen. Insbesondere bei einer Fahrt im Stadtgebiet oder bei einem Stop-and-Go-Betrieb eines Fahrzeugs treten solche Lastanforderungen auf. Short-term changing load requirements are situations in which the requirement changes so quickly that the minimum air ratio required for stationary engine operation must be undercut in order to meet the desired load change. In practical terms, this means that the engine's boost pressure reserve is too low to meet the current load requirement. In other words, there is a short-term changing load requirement if the desired temporal change in the effective mean pressure is so high that the currently available boost pressure, or the boost pressure that the internal combustion engine can provide at short notice is not sufficient to supply the internal combustion engine with the currently required minimum air ratio (or minimum dilution rate). A significantly larger torque is therefore required within a short time, usually within a few seconds (less than 6 seconds) or even fractions of a second. Such load requirements arise in particular when driving in an urban area or when a vehicle is in stop-and-go operation.
Mindestluftverhältnis und Mindest-Verdünnungsrate müssen bei gleichen Lastbedingungen nicht zwangsläufig gleich sein, und hängen vom Zustandekommen der Verdünnung ab (z.B. Magerbetrieb, Abgasrückführung, Wassereinspritzung und anderen Faktoren). Minimum air ratio and minimum dilution rate do not necessarily have to be the same under the same load conditions and depend on how the dilution occurs (e.g. lean operation, exhaust gas recirculation, water injection and other factors).
Beispielsweise liegt insbesondere bei einem Nutzfahrzeug-Motor eine langfristige Lasterhöhung bei einem effektiven Mitteldruck (BMEP - brake mean effective pressure) größer oder gleich 5 bar in der Regel dann vor, wenn die zeitliche Änderung des effektiven Mitteldrucks weniger als 4,0 bar, vorzugsweise weniger als 3,5 bar pro Sekunde beträgt. For example, particularly in a commercial vehicle engine, a long-term load increase at a brake mean effective pressure (BMEP) greater than or equal to 5 bar usually occurs when the change over time in the effective mean pressure is less than 4.0 bar, preferably less than 3.5 bar per second.
Meist liegt insbesondere bei einem Nutzfahrzeug-Motor eine kurzfristige Lasterhöhung bei einem effektiven Mitteldruck (BMEP - brake mean effective pressure) größer oder gleich 5 bar in der Regel dann vor, wenn die zeitliche Änderung des effektiven Mitteldrucks mehr als 3,5 bar pro Sekunde, vorzugsweise mehr als 4 bar pro Sekunde beträgt. In a commercial vehicle engine in particular, there is usually a short-term increase in load at a brake mean effective pressure (BMEP) greater than or equal to 5 bar, usually when the change in the effective mean pressure over time is more than 3.5 bar per second, is preferably more than 4 bar per second.
Bei einem BMEP unter 5 bar kann die zeitliche Änderung des BMEP höher ausfallen. Es liegt in der Regel eine kurzfristige Laständerung dann vor, wenn die zeitliche Änderung des BMEP höher als 25 bar pro Sekunde ist, vorzugsweise höher als 50 bar pro Sekunde. With a BMEP below 5 bar, the change in BMEP over time can be higher. As a rule, there is a short-term change in load when the temporal change in the BMEP is higher than 25 bar per second, preferably higher than 50 bar per second.
Bei einem BMEP unter 5 bar liegt in der Regel eine langfristige Laständerung vor, wenn die zeitliche Änderung des BMEP unter 25 bar pro Sekunde beträgt. With a BMEP below 5 bar, there is usually a long-term load change if the temporal change in the BMEP is below 25 bar per second.
Geht man beispielsweise von einem maximalem effektiven Mitteldruck von 25 bar aus, so liegt in der Regel eine kurzfristige Lastanforderung vor, wenn die gewünschte Änderung des BMEP von Nulllast bis Volllast in 6 Sekunden oder weniger erfolgen soll. For example, if one assumes a maximum effective mean pressure of 25 bar, then there is usually a short-term load requirement if the desired change in the BMEP from no load to full load should occur in 6 seconds or less.
Die Zahlen oben können abhängig von Motorgröße, Drehzahl und thermodynamischer Auslegung der Brennkraftmaschine variieren. Das Luftverhältnis, auch Lambda genannt, ist dabei das Verhältnis der in einen Brennraum der Brennkraftmaschine für einen Verbrennungsvorgang eingebrachten Frischluftmasse durch das Produkt der in den Brennraum für den Verbrennungsvorgang eingebrachten Kraftstoff masse mit dem stöchiometrischen Luftbedarf des Kraftstoffes: The numbers above may vary depending on engine size, speed and thermodynamic design of the internal combustion engine. The air ratio, also called lambda, is the ratio of the fresh air mass introduced into a combustion chamber of the internal combustion engine for a combustion process by the product of the fuel mass introduced into the combustion chamber for the combustion process with the stoichiometric air requirement of the fuel:
Luftverhältnis = Frischluftmenge / (Kraftstoff menge x stöchiometrischer Luftbedarf)Air ratio = fresh air quantity / (fuel quantity x stoichiometric air requirement)
Der stöchiometrische Luftbedarf ist dabei eine Verhältniszahl, die angibt, wie viel Luft notwendig ist, um den betreffenden Kraftstoff stöchiometrisch zu verbrennen.The stoichiometric air requirement is a ratio that indicates how much air is necessary to burn the fuel in question stoichiometrically.
Mit Lastanforderung ist dabei die Drehmomentanforderung gemeint, die der Brennkraftmaschine zu einem bestimmten Moment gestellt wird. The load requirement refers to the torque requirement that is placed on the internal combustion engine at a specific moment.
Die Abgasrückführungsrate ist dabei die Rate, die sich aus der Masse an in den Brennraum rückgeführtem Abgas, dividiert durch die Summe aus eingebrachter Frischluftmasse und eingebrachter Kraftstoffmasse, ergibt: The exhaust gas recirculation rate is the rate that results from the mass of exhaust gas recirculated into the combustion chamber, divided by the sum of the fresh air mass introduced and the fuel mass introduced:
Abgasrückführungsrate = rückgeführte Abgasmenge / (Frischluftmenge + Kraftstoffmenge)Exhaust gas recirculation rate = amount of exhaust gas recirculated / (amount of fresh air + amount of fuel)
Dabei kann die Brennkraftmaschine mit äußerer (PFI - Port Fuel Injection) und/oder mit innerer Gemischbildung (DI - Direct Injection) betrieben werden.The internal combustion engine can be operated with external (PFI - Port Fuel Injection) and/or with internal mixture formation (DI - Direct Injection).
Die Abgasrückführung kann durch eine interne und/oder eine externe Abgasrückführung erfolgen. The exhaust gas recirculation can take place through internal and/or external exhaust gas recirculation.
Dabei können neben dem ersten und zweiten Betrieb auch weitere Betriebe oder Betriebsarten vorgesehen sein. Es kann auch sinnvoll sein, dass die Brennkraftmaschine unter bestimmten Voraussetzungen auch bei sich nur langfristig ändernden Lastanforderungen in einem Betrieb betrieben wird, der nicht der erste Betrieb ist (beispielsweise der zweite Betrieb) und/oder dass die Brennkraftmaschine unter bestimmten Voraussetzungen auch bei kurzfristiger Lasterhöhung in einem Betrieb betrieben wird, der nicht der zweite Betrieb ist. Dies kann beispielsweise der Fall sein, wenn aufgrund der Fahrhistorie oder Sensordaten klar ist, dass sich das Fahrzeug im Stadtgebiet befindet, in dem mit sehr hoher Wahrscheinlichkeit in kürzeren Abständen von mehreren Sekunden bis Minuten kurzfristige Lasterhöhungen zu erwarten sind. In addition to the first and second operations, other operations or operating modes can also be provided. It can also make sense for the internal combustion engine, under certain conditions, to be operated in an operation that is not the first operation (for example the second operation), even when load requirements only change over the long term, and/or for the internal combustion engine to operate under certain conditions even when the load increases for a short time is operated in a company that is not the second company. This can be the case, for example, if it is clear based on the driving history or sensor data that the vehicle is in an urban area where short-term load increases are very likely to occur at shorter intervals of several seconds to minutes.
Vorzugsweise ist vorgesehen, dass das Luftverhältnis bei sich nur langfristig ändernder Lastanforderung/im ersten Betrieb zumindest 1,75 und vorzugsweise zumindest 2 beträgt und/oder maximal 3,5 und vorzugsweise maximal 3 beträgt. So wird sichergestellt, dass möglichst wenig Stickoxid produziert wird. Um eine besonders schnelle Drehmomentbereitstellung zu erreichen, kann vorgesehen sein, dass die Abgasrückführungsrate bei kurzfristiger Lasterhöhung im zweiten Betrieb auf zumindest 10 % erhöht wird, vorzugsweise zumindest 20 % und besonders vorzugsweise zumindest 30 %. In Hinblick auf minimale NOx Rohemissionen ist eine besonders hohe Abgasrückführrate, wie beispielsweise eine um 30 % erhöhte, vorteilhaft, in Hinblick auf einen besonders schnellen Lastanstieg ist eine geringere Abgasrückführrate, wie beispielsweise eine um 10 % bis 20 % erhöhte, besonders vorteilhaft. It is preferably provided that the air ratio is at least 1.75 and preferably at least 2 and/or at most 3.5 and preferably at most 3 when the load requirement only changes over the long term/in the first operation. This ensures that as little nitrogen oxide as possible is produced. In order to achieve a particularly rapid provision of torque, it can be provided that the exhaust gas recirculation rate is increased to at least 10%, preferably at least 20% and particularly preferably at least 30%, in the event of a short-term increase in load in the second operation. With regard to minimal NOx raw emissions, a particularly high exhaust gas recirculation rate, such as one increased by 30%, is advantageous; with regard to a particularly rapid increase in load, a lower exhaust gas recirculation rate, such as one increased by 10% to 20%, is particularly advantageous.
Besonders vorteilhaft ist, wenn bei kurzfristiger Lasterhöhung im zweiten Betrieb das Luftverhältnis auf einen Wert unterhalb von 1,5, vorzugsweise auf einen Wert unterhalb von 1,2 abgesenkt wird. Das niedrige Luftverhältnis ermöglicht eine maximale NOx Minderung des rückgeführten Abgases sowie einen niedrigen Ladedruckbedarf. Der niedrige Ladedruckbedarf ermöglicht einen beschleunigten Lastanstieg. It is particularly advantageous if the air ratio is reduced to a value below 1.5, preferably to a value below 1.2, in the event of a short-term increase in load in the second operation. The low air ratio enables maximum NOx reduction in the recirculated exhaust gas as well as low boost pressure requirements. The low boost pressure requirement enables an accelerated increase in load.
Es kann auch vorteilhaft sein, wenn die Abgasrückführungsrate bei kurzfristiger Lasterhöhung im zweiten Betrieb um zumindest 10 Prozentpunkte erhöht wird, vorzugsweise zumindest 20 Prozentpunkte und besonders vorzugsweise zumindest 30 Prozentpunkte. Die hohe AGR Rate erlaubt niedriges Luftverhältnis, (vorzugsweise Luftverhältnis = 1) Dadurch sinkt der Ladedruckbedarf signifikant. Da der Lastanstieg bei einer Brennkraftmaschine bei kurzfristiger Lasterhöhung ohnehin durch den Anstieg des Ladedrucks begrenzt wird, ist dadurch besonders schnelle Drehmomentbereitstellung möglich. Das niedrige Luftverhältnis wiederum ermöglicht eine maximale NOx Minderung des rückgeführten Abgases. Mit einer Erhöhung um Prozentpunkte ist damit gemeint, dass sich die Abgasrückführungsrate um ebenso viele Prozent erhöht, also beispielsweise bei einer Erhöhung um 10 Prozentpunkte von 5 % auf 15 %. It can also be advantageous if the exhaust gas recirculation rate is increased by at least 10 percentage points, preferably at least 20 percentage points and particularly preferably at least 30 percentage points, in the event of a short-term load increase in the second operation. The high EGR rate allows a low air ratio (preferably air ratio = 1). This significantly reduces the boost pressure requirement. Since the increase in load in an internal combustion engine is anyway limited by the increase in boost pressure in the event of a short-term increase in load, particularly rapid provision of torque is possible. The low air ratio in turn enables maximum NOx reduction in the recirculated exhaust gas. An increase of percentage points means that the exhaust gas recirculation rate increases by the same percentage, for example an increase of 10 percentage points from 5% to 15%.
Weiters kann vorgesehen sein, dass während des ersten Betriebs eine Abgasrückführung erfolgt. In der Regel ist hier eine Abgasrückführung mit niedriger Abgasrückführungsrate sinnvoll, also beispielsweise im Bereich von unter 10 % oder unter 5 %. Furthermore, it can be provided that exhaust gas recirculation takes place during the first operation. As a rule, exhaust gas recirculation with a low exhaust gas recirculation rate makes sense here, for example in the range of less than 10% or less than 5%.
In einer bevorzugten Ausführungsform wird vorgesehen, dass Frischluft vor dem Einführen in zumindest einen Brennraum der Brennkraftmaschine über einen Turbolader komprimiert und vorzugsweise gekühlt wird. So kann der Ladedruck möglichst hoch gehalten werden und eine ausreichende Drehmomentbereitstellung erfolgen. Durch die Kühlung kann die Verbrennungstemperatur niedrig gehalten und so der Stickoxidausstoß vermindert werden. Es kann vorgesehen sein, dass die Abgasrückführung über eine Hochdruckabgasrückführung erfolgt und das rückgeführte Abgas vorzugsweise vor der Einführung in den Brennraum gekühlt wird. Dies ermöglicht eine besonders hohe Ladedruckentlastung. In a preferred embodiment it is provided that fresh air is compressed and preferably cooled via a turbocharger before being introduced into at least one combustion chamber of the internal combustion engine. In this way, the boost pressure can be kept as high as possible and sufficient torque can be provided. Cooling allows the combustion temperature to be kept low, thereby reducing nitrogen oxide emissions. It can be provided that the exhaust gas recirculation takes place via a high-pressure exhaust gas recirculation and the recirculated exhaust gas is preferably cooled before being introduced into the combustion chamber. This enables a particularly high boost pressure relief.
Um die Temperatur im Brennraum weiter zu senken kann vorgesehen sein, dass im zweiten Betrieb Wasser in zumindest einen Brennraum, vorzugsweise aber in allen Brennräumen, der Brennkraftmaschine eingeführt wird und vorzugsweise direkt in den Brennraum eingespritzt wird. Dabei kann das Wasser stromaufwärts des Einlassventils mit der Frischluft und/oder Kraftstoff vermischt werden oder das Wasser direkt in den Brennraum eingespritzt werden. Eine zyklusgetreu applizierbare Wassereinspritzung wirkt sich durch Wärmeentzug aus dem Brennraum für den Phasenübergang (Verdampfungsenthalpie) des eingebrachten Wassers ebenfalls senkend auf die Verbrennungstemperatur aus und reduziert so die NOX Rohemissionen. Dabei kann vorgesehen sein, dass Wasser aus dem Abgas auskondensiert wird und besonders vorzugsweise zur Wassereinspritzung verwendet wird. Insbesondere bei wasserstoffbetriebenen Brennkraftmaschinen ist das sinnvoll. In order to further reduce the temperature in the combustion chamber, it can be provided that in the second operation, water is introduced into at least one combustion chamber, but preferably in all combustion chambers, of the internal combustion engine and is preferably injected directly into the combustion chamber. The water can be mixed with the fresh air and/or fuel upstream of the inlet valve or the water can be injected directly into the combustion chamber. A water injection that can be applied according to the cycle also has a lowering effect on the combustion temperature by removing heat from the combustion chamber for the phase transition (enthalpy of vaporization) of the water introduced and thus reduces NOx raw emissions. It can be provided that water is condensed out of the exhaust gas and is particularly preferably used for water injection. This is particularly useful for hydrogen-powered internal combustion engines.
Um eine schnellere Erhöhung des Ladedrucks unabhängig von der Abgasenthalpie zu gewährleisten, kann im ersten Betrieb bei höherer Lastanforderung der Ladedruck mittels einer zusätzlichen Druckquelle, vorzugsweise angetrieben durch einen Elektromotor, erhöht werden. Dazu kann der Elektromotor beispielsweise einen Verdichter antreiben, der die Frischluft oder das Frischluft/Kraftstoffgemisch vor dem Einführen in den Brennraum verdichtet oder zusätzlich (beispielsweise zu einem Turbolader) verdichtet. In order to ensure a faster increase in the boost pressure regardless of the exhaust gas enthalpy, the boost pressure can be increased in the first operation with higher load requirements using an additional pressure source, preferably driven by an electric motor. For this purpose, the electric motor can, for example, drive a compressor which compresses or additionally compresses the fresh air or the fresh air/fuel mixture before it is introduced into the combustion chamber (for example to form a turbocharger).
Um die Erzeugung von Stickoxiden weiter zu mindern kann vorgesehen sein, dass im ersten Betrieb bei höherer Lastanforderung die Steuerzeiten zumindest eines Ventils der Brennkraftmaschine verändert werden. Die Steuerzeitenanpassung ermöglicht die Beeinflussung sowohl der dem Prozess zur Verfügung stehenden Luftmasse als auch der intern rückgeführten bzw. verbleibenden Abgasmasse (interne Abgasrückführung) zur Einflussnahme auf die Verbrennungstemperatur und damit auf die Stickoxid-Rohemissionen. Diese Maßnahme kann auch im zweiten Betrieb angewendet werden. In order to further reduce the production of nitrogen oxides, it can be provided that the control times of at least one valve of the internal combustion engine are changed in the first operation with higher load requirements. The control time adjustment makes it possible to influence both the air mass available to the process and the internally recirculated or remaining exhaust gas mass (internal exhaust gas recirculation) in order to influence the combustion temperature and thus the raw nitrogen oxide emissions. This measure can also be applied in the second operation.
Um dieses Ziel zu erreichen kann ebenso vorgesehen sein, dass im ersten Betrieb bei höherer Lastanforderung die Ventilhubhöhe zumindest eines Ventils der Brennkraftmaschine verändert wird. Diese Maßnahme kann ebenso im zweiten Betrieb angewendet werden. Durch die Umschaltung zwischen verschiedenen Nockenprofilen kann zyklusgetreu Einfluss auf die verfügbare Luftmasse und somit auch das Luftverhältnis und die NOx-Rohemissionen genommen werden. Insbesondere die Kombination Steuerzeitanpassung und Ventilhubhöhenanpassung ist vorteilhaft. Der Einsatz eines vollvariablen Ventiltriebes bietet größtmögliche Flexibilität in der Applikation bzw. Nutzbarmachung zur Absenkung der Stickoxid- Rohem issionen. In order to achieve this goal, it can also be provided that the valve lift height of at least one valve of the internal combustion engine is changed in the first operation with higher load requirements. This measure can also be used in the second operation. By switching between different cam profiles, the available air mass and thus also the air ratio and the NO x raw emissions can be influenced according to the cycle. The combination of control timing adjustment and valve lift height adjustment is particularly advantageous. The use of a fully variable valve train offers the greatest possible flexibility in the application or use to reduce raw nitrogen oxide emissions.
Erfindungsgemäß können während des ersten Betriebs auch weitere Maßnahmen zur Reduktion des Stickoxidausstoßes gesetzt werden. Beispielsweise können diese Maßnahmen die beschriebe Wassereinführung sein. According to the invention, further measures to reduce nitrogen oxide emissions can also be taken during the first operation. For example, these measures can be the water introduction described.
In weiterer Folge wird die Erfindung anhand der nicht einschränkenden Figuren näher erläutert. Es zeigen: The invention is subsequently explained in more detail using the non-restrictive figures. Show it:
Fig. la ein Diagramm der NOx-Produktion in Abhängigkeit des Luftverhältnisses in einem Verfahren nach dem Stand der Technik; 1a shows a diagram of the NO x production as a function of the air ratio in a process according to the prior art;
Fig. lb ein Diagramm der Motorlast in Abhängigkeit der Zeit entsprechend des Verfahrens aus Fig. la; Fig. lb is a diagram of the engine load as a function of time according to the method from Fig. la;
Fig. 2a ein Diagramm der NOx-Produktion in Abhängigkeit des Luftverhältnisses in einem erfindungsgemäßen Verfahren in einer Ausführungsform; 2a shows a diagram of NOx production as a function of the air ratio in a method according to the invention in one embodiment;
Fig. 2b ein Diagramm der Motorlast in Abhängigkeit der Zeit entsprechend des Verfahrens aus Fig. 2a. Fig. 2b is a diagram of the engine load as a function of time according to the method from Fig. 2a.
In Fig. 1 ist die Produktion von Stickoxiden in Abhängigkeit des Luftverhältnisses während des Betriebs eines Fahrzeugs gemäß dem Stand der Technik aufgetragen. Darunter ist die dazugehörende Abgasrückführungsrate in Abhängigkeit des Luftverhältnisses aufgetragen, welche durchgehend gleich bleibt bei etwa 2 %. Wie ersichtlich ist, ist die NOX Emission im Bereich zwischen Luftverhältnis 1 und 1,8 sehr hoch und fällt dann mit zunehmendem Luftverhältnis weiter ab. Fig. lb zeigt die Motorlast, also das ausgegebene Drehmoment der Brennkraftmaschine, im Zeitverlauf während des Verfahrens, wenn es zu einer kurzfristigen Lasterhöhung kommt. In Fig. 1, the production of nitrogen oxides is plotted as a function of the air ratio during operation of a vehicle according to the prior art. The associated exhaust gas recirculation rate is plotted below as a function of the air ratio, which remains the same throughout at around 2%. As can be seen, the NO Fig. lb shows the engine load, i.e. the output torque of the internal combustion engine, over time during the process if there is a short-term increase in load.
Wird eine Brennkraftmaschine in einem Betriebspunkt 1 betrieben, also bei niedriger Last, so ist es ausreichend, bei einem sehr mageren Mischungsverhältnis bei einem Luftverhältnis von 2,8 zu bleiben, um dieses Drehmoment bereitzustellen. Durch das hohe Luftverhältnis wird wenig Stickoxid produziert. Wenn der Drehmomentbedarf langfristig steigt, so kann das Luftverhältnis langsam reduziert werden und so das höhere Drehmoment bereitgestellt werden. Dabei ist keine Übersteuerung nötig und niedrige Luftverhältnisse, bei denen die NOx-Rohemissionen wesentlich steigen, werden nicht erreicht. Wenn aber wie in Figs, la und lb kurzfristig der Drehmomentbedarf stark steigt, so wird das Luftverhältnis stark gesenkt. Um den Drehmomentbedarf vollständig decken zu können, muss dabei vorübergehend das Luftverhältnis auf bis zu 1,45 gesenkt werden (Punkt 2). Dadurch steigt die NOx Emission massiv an, auf etwa 40 g/kWh. Nach wenigen Sekunden kann das Luftverhältnis wieder reduziert werden, da durch den ausreichenden Ladedruck ein höheres Luftverhältnis von etwa 1,8 ausreicht, um das höhere Drehmoment bereitzustellen (Punkt 3), womit die NOx-Emission wieder auf unter 10 g/kWh fällt.If an internal combustion engine is operated at operating point 1, i.e. at low load, it is sufficient to remain at a very lean mixture ratio with an air ratio of 2.8 in order to provide this torque. The high air ratio means that little nitrogen oxide is produced. If the torque requirement increases in the long term, the air ratio can be slowly reduced and the higher torque can be provided. No overcontrol is necessary and low air conditions, at which raw NO x emissions increase significantly, are not achieved. But if as in Figs, la and lb in the short term If the torque requirement increases sharply, the air ratio is greatly reduced. In order to fully cover the torque requirement, the air ratio must be temporarily reduced to up to 1.45 (point 2). This causes NOx emissions to rise massively, to around 40 g/kWh. After a few seconds, the air ratio can be reduced again, since the sufficient boost pressure means a higher air ratio of around 1.8 is sufficient to provide the higher torque (point 3), which means that the NO x emissions fall back to below 10 g/kWh.
In Fig. 2a wird das gleiche Diagramm gezeigt, jedoch um einen Ast erweitert, der die NOx-Emission in Abhängigkeit des Luftverhältnisses zeigt, wenn ein (ebenso im unteren Teil des Diagramms erweitertes) erfindungsgemäßes Abgasrückführungsverhalten angewendet wird. Wenn gemäß Fig. 2b der gleiche Lastanforderungsverlauf wie bei Fig. lb vorliegt, so ist das Verhalten im Punkt 1 gleich. Wenn nun kurzfristig die Lastanforderung steigt, wird ebenso das Luftverhältnis stark gesenkt. Zusätzlich wird aber wie im unteren Teil der Fig. la ersichtlich die Abgasrückführungsrate von 2 % um etwa 26 Prozentpunkte auf etwa 28 % erhöht. Dadurch wird eine wesentlich geringere Verbrennungstemperatur erreicht und es kommt nur zu einer NOX Rohemission von etwa 2 g/kWh (Punkt 2a). Nach mehreren Sekunden kann der Ladedruck entsprechend angepasst und ein höheres Luftverhältnis von etwa 1,8 eingestellt werden, um wieder möglichst wenig Stickoxid, also NOx, zu produzieren aber die Brennkraftmaschine trotzdem möglichst effizient zu betreiben und in einen ersten Betrieb mit geringer, im Wesentlichen konstanter Abgasrückführung zurückzukehren (Punkt 3). In Fig. 2a the same diagram is shown, but expanded by a branch, which shows the NOx emission as a function of the air ratio when an exhaust gas recirculation behavior according to the invention (also expanded in the lower part of the diagram) is applied. If, according to Fig. 2b, the same load requirement curve is present as in Fig. lb, the behavior at point 1 is the same. If the load requirement increases in the short term, the air ratio is also significantly reduced. In addition, as can be seen in the lower part of FIG. la, the exhaust gas recirculation rate is increased from 2% by approximately 26 percentage points to approximately 28%. As a result, a significantly lower combustion temperature is achieved and there is only a raw NO X emission of around 2 g/kWh (point 2a). After several seconds, the boost pressure can be adjusted accordingly and a higher air ratio of around 1.8 can be set in order to produce as little nitrogen oxide, i.e. NOx, as possible, but still operate the internal combustion engine as efficiently as possible and in a first operation with low, essentially constant Return exhaust gas recirculation (point 3).

Claims

P A T E N T A N S P R Ü C H E Verfahren zum Betreiben einer gasbetriebenen Brennkraftmaschine, vorzugsweise mit Wasserstoff als Kraftstoff, wobei die Brennkraftmaschine in einem ersten Betrieb betrieben wird, bei dem das Luftverhältnis bei höherer Lastanforderung abgesenkt wird, dadurch gekennzeichnet, dass die Brennkraftmaschine bei kurzfristiger Lasterhöhung in einem zweiten Betrieb betrieben wird, bei dem das Luftverhältnis bei höherer Lastanforderung abgesenkt wird und die Abgasrückführungsrate erhöht wird. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass das Luftverhältnis bei im ersten Betrieb zumindest 1,75 und vorzugsweise zumindest 2 beträgt und/oder maximal 3,5 und vorzugsweise maximal 3 beträgt. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Abgasrückführungsrate bei kurzfristiger Lasterhöhung im zweiten Betrieb auf zumindest 10% erhöht wird, vorzugsweise zumindest 20% und besonders vorzugsweise zumindest 30%. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass bei kurzfristiger Lasterhöhung im zweiten Betrieb das Luftverhältnis auf einen Wert unterhalb von 1,5, vorzugsweise auf einen Wert unterhalb von 1,2 abgesenkt wird. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Abgasrückführungsrate bei kurzfristiger Lasterhöhung im zweiten Betrieb um zumindest 10 Prozentpunkte erhöht wird, vorzugsweise zumindest 20 Prozentpunkte und besonders vorzugsweise zumindest 30 Prozentpunkte. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass während des ersten Betriebs eine Abgasrückführung erfolgt. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass Frischluft vor dem Einführen in zumindest einen Brennraum der Brennkraftmaschine über einen Turbolader komprimiert wird und vorzugsweise gekühlt wird. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Abgasrückführung über eine Hochdruckabgasrückführung erfolgt und das rückgeführte Abgas vorzugsweise vor der Einführung in den Brennraum gekühlt wird. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass im zweiten Betrieb Wasser in zumindest einen Brennraum der Brennkraftmaschine eingeführt wird und vorzugsweise direkt in den Brennraum eingespritzt, besonders vorzugsweise in allen Brennräumen eingespritzt wird. Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, dass im ersten Betrieb bei höherer Lastanforderung der Ladedruck mittels einer zusätzlichen Druckquelle, vorzugsweise mittels eines Elektromotors, erhöht wird. Verfahren nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, dass im ersten Betrieb bei höherer Lastanforderung die Steuerzeiten zumindest eines Ventils der Brennkraftmaschine verändert werden. Verfahren nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, dass im ersten Betrieb bei höherer Lastanforderung die Ventilhubhöhe zumindest eines Ventils der Brennkraftmaschine verändert wird. PATENT CLAIMS Method for operating a gas-operated internal combustion engine, preferably with hydrogen as fuel, the internal combustion engine being operated in a first operation in which the air ratio is reduced when the load is higher, characterized in that the internal combustion engine is operated in a second operation when the load increases for a short time in which the air ratio is reduced at higher load requirements and the exhaust gas recirculation rate is increased. Method according to claim 1, characterized in that the air ratio in the first operation is at least 1.75 and preferably at least 2 and / or is a maximum of 3.5 and preferably a maximum of 3. Method according to claim 1 or 2, characterized in that the exhaust gas recirculation rate is increased to at least 10% in the event of a short-term increase in load in the second operation, preferably at least 20% and particularly preferably at least 30%. Method according to one of claims 1 to 3, characterized in that in the event of a short-term increase in load in the second operation, the air ratio is reduced to a value below 1.5, preferably to a value below 1.2. Method according to one of claims 1 to 4, characterized in that the exhaust gas recirculation rate is increased by at least 10 percentage points, preferably at least 20 percentage points and particularly preferably at least 30 percentage points, in the event of a short-term load increase in the second operation. Method according to one of claims 1 to 5, characterized in that exhaust gas recirculation takes place during the first operation. Method according to one of claims 1 to 6, characterized in that fresh air is compressed via a turbocharger and preferably cooled before being introduced into at least one combustion chamber of the internal combustion engine. Method according to one of claims 1 to 7, characterized in that the exhaust gas recirculation takes place via a high-pressure exhaust gas recirculation and the recirculated exhaust gas is preferably cooled before being introduced into the combustion chamber. Method according to one of claims 1 to 8, characterized in that in the second operation, water is introduced into at least one combustion chamber of the internal combustion engine and is preferably injected directly into the combustion chamber, particularly preferably injected in all combustion chambers. Method according to one of claims 1 to 9, characterized in that in the first operation with higher load requirements, the boost pressure is increased by means of an additional pressure source, preferably by means of an electric motor. Method according to one of claims 1 to 10, characterized in that in the first operation with higher load requirements, the control times of at least one valve of the internal combustion engine are changed. Method according to one of claims 1 to 11, characterized in that in the first operation with higher load requirements, the valve lift height of at least one valve of the internal combustion engine is changed.
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