Method for operating an internal combustion engine and internal combustion engine
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- VOLKSWAGEN AG
- Filing Date
- 2018-08-23
- Publication Date
- 2026-07-09
AI Technical Summary
Existing methods fail to effectively reduce nitrogen oxide emissions during high-load operation of internal combustion engines, particularly in diesel engines, due to insufficient exhaust gas recirculation, leading to exceedance of emission limits in Real Driving Emissions (RDE) tests.
Increasing the exhaust gas recirculation rate by 1-5% during high-load operation to enhance pollutant conversion in exhaust gas aftertreatment devices, combined with additional measures like power or torque limitation if necessary, to maintain compliance with emission limits.
Reduces nitrogen oxide emissions by 3-5% without significant power loss, ensuring compliance with stringent emission standards even in high-load conditions.
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Abstract
Description
[0001] The invention relates to a method for operating an internal combustion engine with an air supply system and an exhaust system, as well as to such an internal combustion engine according to the preamble of the independent claims.
[0002] Current and increasingly stringent emissions legislation places high demands on raw engine emissions and exhaust aftertreatment in combustion engines. The requirements for further reductions in fuel consumption and the tightening of emissions standards regarding permissible nitrogen oxide emissions pose a challenge for engine developers. In gasoline engines, exhaust gas purification is achieved in the familiar manner via a three-way catalytic converter, as well as additional catalysts upstream and downstream of the three-way converter. Diesel engines currently employ exhaust aftertreatment systems that include an oxidation catalyst, a catalyst for the selective catalytic reduction of nitrogen oxides (SCR catalyst), a particulate filter for the separation of soot particles, and, if necessary, further catalysts. Ammonia is preferably used as the reducing agent.Because handling pure ammonia is complex, vehicles typically use a synthetic, aqueous urea solution, which is mixed with the hot exhaust gas stream in a mixing unit upstream of the SCR catalyst. This mixing heats the aqueous urea solution, causing it to release ammonia into the exhaust system. A commercially available aqueous urea solution generally consists of 32.5% urea and 67.5% water.
[0003] Under highly dynamic driving conditions, prolonged high-load operation can lead to exceeding a predefined route-specific emission limit. For diesel engines, nitrogen oxide emissions are particularly affected. Specifically, with a heated exhaust system and prolonged high-load operation, the exhaust gas temperature and / or the temperature of the catalytic converters can reach a temperature at which selective catalytic reduction of nitrogen oxides is only possible to a limited extent.
[0004] From DE 10 2014 217 591 A1, a method for controlling an exhaust gas recirculation (EGR) valve is known, wherein, for the EGR quantity during dynamic engine operation, the actual EGR quantity is compared with a target EGR quantity. In this process, to open an EGR valve and prevent a torque dip, the necessary boost pressure is adjusted such that the EGR quantity is increased to the same extent as the boost pressure built up to prevent a torque dip.
[0005] From DE 10 2016 210 243 A1 a method for adjusting the air supply to the combustion chambers of an internal combustion engine is known, in which a bypass is opened in the event of a sudden throttle release (tip-out) to increase the fresh air supply to the combustion chambers of the internal combustion engine and to reduce the exhaust gas recirculation quantity in order to avoid rough engine running or misfires.
[0006] From DE 10 2016 211 311 A1, a method for adjusting the exhaust gas recirculation rate in an internal combustion engine is known. In this method, an estimated quantity of recirculated exhaust gas is compared with a measured actual quantity, and a model for calculating the exhaust gas recirculation rate is adjusted accordingly based on the determined offset.
[0007] A disadvantage of the known methods, however, is that none of them address emission reduction during high-load operation, as such operating conditions were not tested in previous emission tests. With the transition to and recording of Real Driving Emissions (RDE), these load points, which were not tested in previous emission tests, have now also come into focus.
[0008] The object of the invention is to reduce the emissions of an internal combustion engine, particularly during high-load operation, and thus to relieve the burden on the environment.
[0009] According to the invention, this problem is solved by a method for the exhaust aftertreatment of an internal combustion engine with at least one combustion chamber. The internal combustion engine is connected via its inlet to an air supply system and via its outlet to an exhaust system of the internal combustion engine. At least one exhaust aftertreatment component for converting pollutants in the exhaust gas of the internal combustion engine is arranged in the exhaust system. The method comprises the following steps: - Recording a load condition and a route-related emission value of the internal combustion engine, wherein - when the route-related emission value approaches a defined threshold value and a high-load operation of the combustion engine is detected, the exhaust gas recirculation rate of the combustion engine is increased.
[0010] In this context, high-load operation refers to the operation of the combustion engine in which, due to the exhaust gas velocity, volume, and / or temperature, complete conversion of harmful exhaust components by the exhaust aftertreatment systems is not possible. Increasing the exhaust gas recirculation rate by one percent can reduce the raw emissions, particularly NOx emissions, of the combustion engine by 3–5 percent. At the same time, the engine's power output decreases only slightly, so the driver will barely notice, or not at all, this increase in the exhaust gas recirculation rate in the vehicle's handling.
[0011] The features listed in the dependent claims enable advantageous improvements and further developments of the exhaust gas aftertreatment method specified in the independent claim.
[0012] In a preferred embodiment of the method, the exhaust gas temperature and / or the component temperature of an exhaust aftertreatment component are additionally measured, with the exhaust gas recirculation rate being increased depending on the component temperature of the exhaust aftertreatment component. The exhaust gas recirculation rate increases with rising exhaust gas temperature or rising component temperature of the exhaust aftertreatment component, particularly the catalysts. This allows the raw emissions to be reduced accordingly, so that the limit values for route-related exhaust emissions are not exceeded.
[0013] In a preferred embodiment of the method, the increase in exhaust gas recirculation quantity occurs within a load range in which the internal combustion engine operates at least 60% of its rated power, preferably at least 70%, and particularly preferably at least 80% of its rated power, and / or at least 60% of its rated speed, preferably at least 70%, and particularly preferably at least 80% of its rated speed. Typically, the internal combustion engine is operating at high load when at least one of the aforementioned criteria is met or exceeded. While sufficient conversion of pollutants by the exhaust aftertreatment components can occur below these thresholds, additional measures are necessary above these thresholds to prevent an increase in the vehicle's tailpipe emissions.By increasing the exhaust gas recirculation rate, raw emissions can be reduced as described, so that even during these high-load phases the route-specific emission limits are not exceeded.
[0014] A further improvement to the procedure envisages that, after increasing the exhaust gas recirculation rate, a further comparison of the route-specific emission values with the current emission values will be carried out. If an exceedance of the route-specific emission values is expected, the power and / or torque of the combustion engine will be limited. If, despite increasing the exhaust gas recirculation rate, there is a risk that the route-specific emission values will not be met, additional measures can be implemented to reduce the raw emissions of the combustion engine and / or improve the effectiveness of the exhaust aftertreatment components. This objective can be achieved by limiting the power and / or torque of the combustion engine. However, this measure should only be implemented as a secondary measure, as it represents a noticeable intervention for the driver and thus reduces driving comfort.
[0015] In a preferred embodiment of the invention, the internal combustion engine is designed as a self-igniting diesel engine, and the distance-related emission value is the nitrogen oxide tailpipe emissions of the internal combustion engine. Increasing the exhaust gas recirculation rate can significantly reduce raw NOx emissions. Overall, increasing the exhaust gas recirculation rate lowers the temperature in the combustion chambers, which can also have a positive effect on other emissions.
[0016] It is advantageous that the route-specific nitrogen oxide emissions are measured by at least one NOx sensor in the exhaust system. A NOx sensor allows for the simple determination of nitrogen oxide emissions in the exhaust gas of the combustion engine. This makes it possible to identify whether there is a risk of exceeding the route-specific emission limits and, if necessary, to initiate an increase in the exhaust gas recirculation rate and, if required, secondary measures.
[0017] According to the invention, an internal combustion engine with at least one combustion chamber is proposed, the inlet of which is connected to an air supply system and the outlet of which is connected to an exhaust system. The exhaust system includes at least one exhaust aftertreatment component for converting pollutants in the exhaust gas of the internal combustion engine. The internal combustion engine has a control unit configured to carry out a method according to the invention when a machine-readable program code is executed by the control unit. Such an internal combustion engine makes it possible to reduce the raw emissions of the internal combustion engine by carrying out a method according to the invention. The raw emissions are reduced, particularly during the high-load phase, by increasing the exhaust gas recirculation rate, so that the exhaust gas contains fewer emissions.These emissions can then be converted more effectively by the exhaust aftertreatment components, significantly reducing tailpipe emissions. This allows compliance with stringent emission limits even at operating points of the combustion engine that were previously not relevant for testing.
[0018] In a preferred embodiment of the internal combustion engine, an air mass meter and a pressure sensor are arranged in the air supply system. The air mass meter determines the amount of fresh air supplied to the combustion chambers of the internal combustion engine. An additional pressure sensor in the air supply system further improves the measurement accuracy, thereby optimizing the control of the air-fuel ratio and thus the engine combustion process. This reduces the raw emissions of the internal combustion engine, so that fewer harmful exhaust gas components need to be converted by the exhaust aftertreatment components.
[0019] In a preferred embodiment of the combustion engine, a first catalyst, in particular an oxidation catalyst or a NOx storage catalyst, and a particulate filter are arranged in the exhaust system. The particulate filter has a coating for the selective catalytic reduction of nitrogen oxides, or an SCR catalyst is connected downstream of the particulate filter. Such an exhaust system enables highly efficient exhaust aftertreatment of a diesel engine. Nitrogen oxides can be reduced at three points in the exhaust system: at the NOx storage catalyst, at the SCR coating of the particulate filter, and at the SCR catalyst downstream of the particulate filter. Thus, efficient exhaust aftertreatment with regard to NOx emissions is possible in every load range of the combustion engine.
[0020] A further improvement to the combustion engine involves the integration of at least one exhaust gas sensor in the exhaust system to monitor the engine's current emissions, particularly at least one NOx sensor. A NOx sensor allows for the simple determination of nitrogen oxide emissions in the engine's exhaust gas. This enables the detection of potential exceedances of the route-specific emission limits, allowing for adjustments to the exhaust gas recirculation rate and, if necessary, the implementation of secondary measures. Furthermore, additional exhaust gas sensors, such as a temperature sensor or a lambda sensor, may be included to control the exhaust aftertreatment system and enhance its efficiency.
[0021] Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another.
[0022] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. Identical components or components with the same function are identified by the same reference numerals in the different figures. The figures show: Figs. 1 a first embodiment of an internal combustion engine with an air supply system and an exhaust system; Figs. 2 another embodiment of an internal combustion engine with an air supply system and an exhaust system; Figs. 3 a simplified flowchart for carrying out a method according to the invention for the exhaust aftertreatment of an internal combustion engine; Figs.4 a diagram for adjusting the exhaust gas recirculation quantity depending on the route-related emissions; Figs. 5 a diagram for adjusting the torque and / or power if adjusting the exhaust gas recirculation quantity alone is not sufficient to achieve the route-related emissions.
[0023] Figs. Figure 1 shows a schematic representation of an internal combustion engine. 10 The internal combustion engine 10 It is designed as a direct-injection diesel engine. The internal combustion engine 10 has multiple combustion chambers 12 on. At the combustion chambers 12 Each is a fuel injector. 14 for injecting fuel into the respective combustion chamber 12 arranged. The internal combustion engine 10 is with its admission 16 with an air supply system 20 and with its outlet 18 with an exhaust system 40 connected. The internal combustion engine10 It also includes a high-pressure exhaust gas recirculation system. 32 with an exhaust gas recirculation line 34 and a high-pressure exhaust gas recirculation valve 36 , over which an exhaust gas from the combustion engine 10 from the outlet 18 to the entrance 16 can be traced back. At the combustion chambers 12 Inlet valves and outlet valves are arranged, with which a fluidic connection to the air supply system is established. 20 to the combustion chambers 12 or from the combustion chambers 12 to the exhaust system 40 can be opened or closed.
[0024] The air supply system 20 includes an intake pipe 28 , in which, in the direction of flow of fresh air through the intake pipe 28 an air filter 22 , downstream of the air filter, an air mass meter 24 , in particular a hot-film air mass meter, and downstream of the air mass meter24 a compressor 26 an exhaust gas turbocharger 38 are arranged. The air mass meter can be used in this process. 24 also in a filter housing of the air filter 22 be arranged so that the air filter 22 and the air mass meter 24 train an assembly.
[0025] The exhaust system 40 includes an exhaust duct 42 , in which in the direction of flow of an exhaust gas from the internal combustion engine 10 through the exhaust duct 22 a turbine 44 the exhaust gas turbocharger 38 is arranged, which the compressor 26 in the air supply system 20 driven by a shaft. The exhaust gas turbocharger 38 is preferably designed as an exhaust gas turbocharger with variable turbine geometry. For this purpose, a turbine wheel of the turbine is used. 44 Adjustable guide vanes are installed upstream, which direct the flow of exhaust gas onto the turbine blades. 44can be varied. Downstream of the turbine 44 are several exhaust aftertreatment components 46 , 48 , 54 , 56 This is planned to take place immediately downstream of the turbine. 44 The first component of the exhaust aftertreatment system is a NOx storage catalyst. 48 arranged, which includes an oxidation catalyst 46 includes downstream of the NOx storage catalyst. 48 is a particulate filter 54 with a coating 56 Arranged for the selective catalytic reduction of nitrogen oxides. Downstream of the NOx storage catalyst. 48 and upstream of the particulate filter 54 is a dosing element 50 with a metering valve 52 arranged, with which a reducing agent, in particular aqueous urea solution, is introduced into the exhaust duct 42 of the internal combustion engine 10 It can be dosed. Furthermore, it is located in the exhaust system. 40an exhaust gas sensor 68 , in particular a NOx sensor, is arranged, with which the exhaust emissions can be monitored during engine operation.
[0026] The internal combustion engine 10 is equipped with an engine control unit 70 connected, which is linked to the exhaust gas sensor via signal lines not shown. 68 as well as with the dosing element 50 is connected to the metering of reducing agent. Furthermore, the control unit is connected to the injectors. 14 connected to control the fuel injection timing and the amount of fuel injected into the combustion chambers 12 to control injected fuel.
[0027] In Figs. 2 is another embodiment of an internal combustion engine 10 depicted. With essentially the same structure as to Figs. As described in 1, in this embodiment an additional pressure sensor is included in the air supply system. 30planned. Furthermore, downstream of the compressor 26 the exhaust gas turbocharger 38 and upstream of the inlet 16 of the internal combustion engine 10 An intercooler is provided, with which the compressed air is cooled before entering the combustion chambers. 12 It cools down, thus improving the filling of the combustion chambers. In the exhaust system 40 is downstream of the outlet 18 and upstream of the turbine 44 the exhaust gas turbocharger 38 another pressure sensor 66 It is provided for. Furthermore, it is located downstream of the particulate filter. 54 an SCR catalyst 64 It is arranged downstream of the particulate filter. 54 and upstream of the SCR catalyst 64 another dosing element 60 with a metering valve 62 intended for the dosing of a reducing agent. Furthermore, the exhaust duct 42 multiple exhaust gas sensors 68provided for, whereby in Figs. 2. A selection of possible positions for the exhaust gas sensors 68 is shown. As an alternative to a NOx storage catalyst 48, the first catalyst can also be used as an oxidation catalyst. 46 be installed. Furthermore, the particulate filter can 54 instead of an SCR coating, another catalytically active coating can also be used. 58 , in particular with an oxidatively active coating. Alternatively, the particle filter can be 54 with a downstream SCR catalyst 64 It can also be made uncoated, in which case one of the metering elements 50 , 60 can be omitted.
[0028] In Figs. Figure 3 is a flowchart for carrying out a method according to the invention for the exhaust aftertreatment of an internal combustion engine. 10 illustrated. In a first procedural step IThe NOx concentration in the exhaust duct will be increased. 42 through a component in the control unit 70 stored exhaust gas model calculated or by the exhaust gas sensor 68 measured. Parallelally, in a process step, II the exhaust gas mass flow from the air mass flow at the air mass meter 24 and those through the fuel injectors 14 The amount of fuel injected is determined. In one process step III The current mass-related emissions are determined based on these two parameters. In one process step IV The cumulative emissions in the exhaust duct are calculated from the current mass-related emissions. 42 determined. Furthermore, in one procedural step VI the actual distance travelled and in one procedural step VIIThe minimum specified distance is determined, with the larger value being used in the calculation. In process step V, the distance-related emissions are calculated based on the cumulative exhaust emissions and the distance traveled. EG / D determined. Optionally, in a process step, VIII the exhaust gas temperature T EG or the temperature T KAT determined by an exhaust aftertreatment component. Based on a value in the control unit 70 stored characteristic map of the combustion engine 10 It will now be determined whether the route-related emissions EG / D below a defined limit. Is it foreseeable that, with the current engine parameters, the route-related emissions will fall below a certain threshold? EG / D If this cannot be achieved, then in a procedural step IX the exhaust gas recirculation rate EGR increased.
[0029] In Figs. Figure 4 is a diagram for adjusting the exhaust gas recirculation rate. EGRdepending on the route-related emissions EG / D and the exhaust gas temperature T EG As shown. During normal operation of the internal combustion engine. 10 The emission profile corresponds to the curve shown in the first curve. This represents the exhaust gas recirculation rate during normal operation. EGR defined as 100%. During high-load operation and exhaust gas temperatures exceeding 600°C, the exhaust gas recirculation rate is... EGR adjusted according to the curves shown to reduce the raw emissions of the combustion engine 10 to reduce emissions and thus continue to fall below the limits for route-related emissions.
[0030] In Figs. Figure 5 is a diagram for adjusting the torque and / or power when adjusting the exhaust gas recirculation quantity alone is insufficient to achieve the route-specific emissions. The power output is then... P and / or the torque Mof the internal combustion engine 10 The intervention in the engine control unit is correspondingly limited. The more a certain temperature threshold is exceeded, at which compliance with the route-specific emission limits is expected, the more pronounced the intervention in the engine control unit becomes. In addition to reducing power or torque, other engine parameters, particularly the injection timing and injection quantity, can also be adjusted to reduce the raw emissions of the combustion engine. 10 to minimize. Reference symbol list 10 Internal combustion engine 12 Combustion chamber 14 Fuel injector 16 Admission 18 Outlet 20 Air supply system 22 air filters 24 air mass meters 26 compressors 28 Intake manifold 30 pressure sensor 32 High-pressure exhaust gas recirculation 34 Exhaust gas recirculation channel 36 Exhaust gas recirculation valve 38 exhaust gas turbochargers 40 Exhaust system 42 Exhaust duct 44 Turbine 46 Oxidation catalyst 48 NOx storage catalyst 50 dosing module 52 Metering valve 54 particulate filters 56 SCR coating 58 catalytic coating 60 second dosing module 62 second metering valve 64 SCR catalyst 66 Pressure sensor 68 Exhaust gas sensor / NOx sensor 70 Control unit EC / D route-related emission value EGR exhaust gas recirculation rate N N Rated speed P Performance P ist load condition P N Rated power Temperature T EG Exhaust gas temperature T KATCatalyst temperature QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] DE 102014217591 A1
[0004] DE 102016210243 A1
[0005] DE 102016211311 A1
[0006]
Claims
[1] Method for exhaust aftertreatment of an internal combustion engine (10) with at least one combustion chamber (12), wherein the internal combustion engine (10) is connected to an air supply system (20) via its inlet (16), wherein the internal combustion engine (10) is connected to an exhaust system (40) via its outlet (18), wherein at least one exhaust aftertreatment component (46, 48, 54, 64) for converting pollutants in the exhaust gas of the internal combustion engine (10) is arranged in the exhaust system (40), comprising the following steps: - Detecting a load condition (P ist ) and a route-related emission value (EC / D) of the internal combustion engine (10), wherein - when the route-related emission value (EC / D) approaches a defined threshold value (EC / D) S ) and upon detection of high load operation of the internal combustion engine (10) the exhaust gas recirculation rate (EGR) of the internal combustion engine (10) is increased. [2] Method for exhaust gas aftertreatment according to claim 1, characterized by that in addition an exhaust gas temperature (T EG ) and / or a component temperature (T KAT ) of an exhaust aftertreatment component (46, 48, 54, 64) is detected, whereby the increase in the exhaust gas recirculation (EGR) rate depends on the exhaust gas temperature (T EG ) or the component temperature (T KAT ) of the exhaust aftertreatment component (46, 48, 54, 64). [3] Method for exhaust gas aftertreatment according to claim 1 or 2, characterized by , that the increase in the exhaust gas recirculation (EGR) quantity takes place in a load range in which the internal combustion engine (10) operates at least 60% of its rated power (P N ) and / or 60% of its rated speed (N N ) reached. [4] Method for exhaust gas aftertreatment according to any one of claims 1 to 3, characterized by, that after increasing the exhaust gas recirculation (EGR) quantity, a further comparison of the route-related emission values (EG / D) with the current emission values is carried out and, if an expected exceedance of the route-related emission values (EG / D), the power (P) and / or the torque (M) of the internal combustion engine (10) is limited. [5] Method for exhaust aftertreatment according to any one of claims 1 to 4, characterized by , that the internal combustion engine (10) is designed as a self-igniting internal combustion engine (10) according to the diesel principle and the distance-related emission value (EC / D) is the nitrogen oxide (NOx) emissions of the internal combustion engine (10). [6] Method for exhaust gas aftertreatment according to claim 5, characterized by , that the route-related nitrogen oxide emissions (EC / D) are detected by at least one NOx sensor (68) in the exhaust system (40). [7] Internal combustion engine (10) with at least one combustion chamber (12), wherein the internal combustion engine (10) is connected via its inlet (16) to an air supply system (20), wherein the internal combustion engine (10) is connected via its outlet (18) to an exhaust system (40), wherein at least one exhaust aftertreatment component (46, 48, 54, 64) for converting pollutants in the exhaust gas of the internal combustion engine (10) is arranged in the exhaust system (40), and with a control unit (70) which is configured to carry out a method according to the invention as defined in any one of claims 1 to 6 when a machine-readable program code is executed by the control unit (70). [8] Internal combustion engine (10) according to claim 7, characterized by , that an air mass meter (24) and / or a pressure sensor (30) is arranged in the air supply system (20). [9] Internal combustion engine (10) according to claim 7 or 8, characterized by, that in the exhaust system (40) a first catalyst (46, 48), in particular an oxidation catalyst (46) or a NOx storage catalyst (48), and downstream of the first catalyst (46, 48) a particulate filter (54) are arranged, wherein the particulate filter (54) has a coating (56) for the selective catalytic reduction of nitrogen oxides and / or an SCR catalyst (64) is downstream of the particulate filter (54). [10] Internal combustion engine (10) according to any one of claims 7 to 9, characterized by , that at least one sensor (68) for detecting the current emissions, in particular at least one NOx sensor (68), is arranged in the exhaust system (40).