Method for operating internal combustion engine, control device for internal combustion engine, and internal combustion engine having such control device

Abstract

The invention relates to a method for operating an internal combustion engine, a control device for an internal combustion engine and an internal combustion engine having such a control device. The invention relates to a method for operating an internal combustion engine (1), in which-a combustion gas having a fluctuating hydrogen content is introduced into an air path (5) of the internal combustion engine (1), and in which-a combustion air ratio for a combustion chamber (15) of the internal combustion engine (1) is adjusted by a predeterminable combustion gas mass flow into the air path (5), a power variable of the internal combustion engine (1) is adjusted by means of a throttle valve (9) arranged in the air path (5), a nitrogen oxide concentration in an exhaust gas path (11) of the internal combustion engine (1) is determined, and the combustion air ratio is adjusted as a function of the determined nitrogen oxide concentration, a throttle reserve in the air path (5) is determined, and wherein an ignition time in a combustion chamber (15) of the internal combustion engine (1) is selected as a function of the determined throttle reserve.

Description

Field of the Invention

[0001] The present invention relates to a method for operating an internal combustion engine, a control device for an internal combustion engine for carrying out such a method, and an internal combustion engine having such a control device. Background Art

[0002] In particular from the perspective of environmental protection, it is planned to gradually move towards the so-called hydrogen economy, especially using hydrogen as a fuel or combustion gas. In this regard, in particular, it is provided that hydrogen is mixed with other combustion gases, especially hydrogen is injected into the distribution network of other combustion gases, especially into the natural gas network. However, here, to a certain extent, it is inevitably obtained that the hydrogen concentration fluctuates over time, whereby problems occur during the operation of an internal combustion engine using such a combustion gas mixture (hereinafter also referred to as combustion gas). In such an internal combustion engine operation, in particular, it can cause very strongly fluctuating nitrogen oxide emissions that also exceed the legally prescribed extreme values. Applying a suitable sensing mechanism, especially a hydrogen sensor, presents as a simple and feasible solution for taking into account the fluctuating hydrogen fraction in the combustion gas mixture. However, this requires additional structural components and additional control measures, which are costly and expensive. In addition, the regulation of the fluctuating hydrogen fraction faces the following problem: during the matching process, especially with an increasing hydrogen fraction, the throttle reserve seems to be depleted, and the throttle reserve is indispensable for the power of the internal combustion engine regarding possible load changes. Summary of the Invention

[0003] Therefore, the present invention is based on the task of providing a method for operating an internal combustion engine, a control device for an internal combustion engine for carrying out such a method, and an internal combustion engine having such a control device, wherein at least the mentioned disadvantages are reduced, preferably no longer occur.

[0004] This task is solved by providing the teachings of the current technology, especially the teachings of the independent claims and the preferred embodiments disclosed in the dependent claims and the description.

[0005] This task is solved in particular by providing a method for operating an internal combustion engine, in which combustion gas having a fluctuating hydrogen fraction is introduced into the air path of the internal combustion engine, in which the combustion air ratio for the combustion chamber of the internal combustion engine is adjusted by a presettable mass flow of combustion gas to be introduced or already introduced into the air path, in which the power parameter of the internal combustion engine is adjusted by means of a throttle valve arranged in the air path, in which the nitrogen oxide concentration in the exhaust gas path of the internal combustion engine is measured, in which the combustion air ratio is adjusted as a function of the measured nitrogen oxide concentration, in which the throttle valve reserve in the air path is measured, and in which the ignition timing in the combustion chamber of the internal combustion engine is selected as a function of the measured throttle valve reserve. By adjusting the combustion air ratio as a function of the measured nitrogen oxide concentration, the internal combustion engine can be advantageously adjusted with respect to the fluctuating hydrogen fraction in the combustion gas without the need for a separate hydrogen sensor. Here, in particular, it is possible to advantageously comply with the legally prescribed nitrogen oxide limits. By additionally selecting the ignition timing in the combustion chamber as a function of the measured throttle valve reserve, the throttle valve reserve is advantageously prevented from being exhausted and the power necessary or desirable for possible load changes of the internal combustion engine is maintained.

[0006] Combustion gas is in particular understood in the context of the current state of the art teaching as a combustible gas or gas mixture that is gaseous at room temperature and ambient pressure, in particular at 25 °C and 1013 mbar. Combustion gas is in particular understood as a mixture consisting of natural gas, in particular liquefied natural gas (LNG), and hydrogen (in particular with a variable hydrogen fraction).

[0007] The hydrogen fraction is in particular understood in the context of the current state of the art teaching as the hydrogen concentration or the local hydrogen pressure.

[0008] The combustion air ratio is in particular understood in the context of the current state of the art teaching as the lambda value (Lambdawert). Thus, the combustion air ratio is in particular the ratio of the actual air mass to the air mass required for complete stoichiometric combustion, or equivalently, the quotient of the actual ratio of air mass to fuel mass and the stoichiometric ratio of air mass to fuel mass.

[0009] The power parameter is understood in the context of the current state of the art teaching as a physical parameter, measured value or parameter that characterizes the power of the internal combustion engine. The power parameter can in particular be the power itself. Alternatively or additionally, the power parameter can also be the torque of the internal combustion engine or other suitable parameters.

[0010] Adjust the combustion air ratio depending on the measured nitrogen oxide concentration, which in particular means adjusting the preset combustion gas mass flow depending on the measured nitrogen oxide concentration.

[0011] The throttle reserve is in particular understood in the context of the current state of the art as the pressure difference formed by the throttle in the air path, in particular as the pressure drop formed by the throttle, in particular as the difference between a first pressure in the air path (in particular directly) upstream of the throttle and a second pressure in the air path (in particular directly) downstream of the throttle.

[0012] The internal combustion engine operates in particular in a characteristic range with a combustion air ratio of 1 during idling and in a characteristic range with a combustion air ratio of 1.75 to 2, in particular up to 1.8, during rated load operation, wherein the internal combustion engine operates in a narrow range with a combustion air ratio of in particular up to 2, in particular up to 1.8, in the load range (i.e., in particular above the idling speed). This in particular means that the internal combustion engine is preferably operated at least at full load such that the combustion air ratio does not drop below 1.8 or does not drop below 1.75. Thereby, the internal combustion engine is in particular a lean gas engine (Magergasmotor).

[0013] According to a modification of the invention, it is provided that the power parameter is adjusted to a nominal value by means of the throttle. Advantageously, thereby, the internal combustion engine can be operated in a controlled manner by means of the power parameter. The nominal value can in particular be set to be constant or variable over time.

[0014] According to a modification of the invention, it is provided that when the measured nitrogen oxide concentration is greater than the nominal nitrogen oxide concentration, the combustion air ratio is increased, that is to say, in particular the preset combustion gas mass flow is reduced, and when the measured nitrogen oxide concentration is less than the nominal nitrogen oxide concentration, the combustion air ratio is reduced, that is to say, in particular the preset combustion gas mass flow is increased. Alternatively or additionally, when the measured nitrogen oxide concentration is equal to the nominal nitrogen oxide concentration, the combustion air ratio is not changed.

[0015] An increase in the hydrogen fraction in the combustion gas in particular leads to a faster combustion process in the combustion chamber, i.e., to a faster and hotter combustion, which results in an increase in the nitrogen oxide concentration in the exhaust gas. If now the combustion air ratio is increased in a suitable manner, the combustion process slows down again and the nitrogen oxide concentration decreases. However, the power of the internal combustion engine decreases at the same time; to balance this, the throttle valve is further opened by power regulation, which causes a decrease in the throttle valve reserve. Conversely, if the hydrogen fraction in the combustion gas decreases, the combustion process slows down; the nitrogen oxide concentration decreases, and the combustion air ratio can be reduced; this means that the mass flow of the combustion gas into the air path is increased. As a result, the power of the internal combustion engine increases at the same time; to balance this, the power regulation slightly closes the throttle valve, so that the throttle valve reserve increases. Thus, the internal combustion engine is regulated with respect to the fluctuating hydrogen fraction; the regulation simultaneously affects the hydrogen fraction in the combustion gas and its throttle valve reserve.

[0016] The theoretical nitrogen oxide concentration in particular corresponds to the nitrogen oxide limit values prescribed by law. For the highest possible efficiency of the internal combustion engine, the measures explained here are particularly used, so that the current nitrogen oxide concentration corresponds as accurately as possible to the nitrogen oxide limit values prescribed by law. When the current nitrogen oxide contraction is less than the nitrogen oxide limit value, the nitrogen oxide concentration in the exhaust gas is particularly increased. In one embodiment, the theoretical nitrogen oxide concentration in particular corresponds to the nitrogen oxide limit value prescribed by law minus a safety discount, where the safety discount particularly takes into account possible aging effects, sensor deviations or other effects that act on emissions. For the highest possible efficiency of the internal combustion engine, the measures explained here are particularly used, so that the current nitrogen oxide concentration corresponds as accurately as possible to the nitrogen oxide limit value prescribed by law minus the safety discount. When the current nitrogen oxide contraction is less than the nitrogen oxide limit value minus the safety discount, the nitrogen oxide concentration in the exhaust gas is particularly increased.

[0017] In one embodiment, when the measured nitrogen oxide concentration is greater than the theoretical nitrogen oxide concentration, the combustion air ratio (starting particularly from the current value) is increased incrementally. Alternatively or additionally, when the measured nitrogen oxide concentration is less than the theoretical nitrogen oxide concentration, the combustion air ratio (starting particularly from the current value) is decreased incrementally.

[0018] In one embodiment, the combustion air ratio varies from 1.8 to 2, particularly to 2.0, in the load range.

[0019] Alternatively or additionally, the increment (λ increment) for changing the combustion air ratio is from 0.01 to 0.03, particularly 0.02.

[0020] According to a modification of the invention, when the measured throttle reserve (especially from above, that is, from a higher value) reaches or falls below a pre-determined reserve minimum, the ignition timing is adjusted backward. Wherein, when the measured throttle reserve exceeds the pre-determined reserve minimum (especially plus a pre-determined hysteresis value), the ignition timing is adjusted forward after the backward adjustment. The ignition timing is adjusted forward especially when it has been adjusted backward before and the previous backward adjustment has not been compensated by a subsequent forward adjustment. If the ignition timing is adjusted backward, this results in combustion in the combustion chamber taking place at a lower temperature, thereby reducing the concentration of nitrogen oxides in the exhaust gas; however, the exhaust gas temperature increases simultaneously due to lower expansion cooling during the expansion stroke; thus, the turbine arranged in the exhaust gas path of the internal combustion engine of the exhaust gas turbocharger is supplied with more enthalpy, and thus the compressor of the exhaust gas turbocharger arranged upstream of the throttle in the air path and drivingly connected to the turbine obtains more power. Thereby, the pressure in the air path rises again; at the same time, the power of the internal combustion engine rises, which is balanced by power regulation in such a way that the throttle is slightly closed. Thereby, the throttle reserve is increased again. Conversely, if the ignition timing is adjusted forward, this results in combustion in the combustion chamber taking place at a higher temperature, thereby increasing the concentration of nitrogen oxides in the exhaust gas; at the same time, the exhaust gas temperature drops due to higher expansion cooling; thus, the turbine is supplied with less enthalpy, so that the compressor obtains less power. Thereby, the pressure in the air path drops again; at the same time, the power of the internal combustion engine drops, which is balanced by power regulation in such a way that the throttle is further opened. Thereby, the throttle reserve is reduced.

[0021] The inventors have especially realized that the adjustment of the ignition timing, advantageously on the one hand with respect to the nitrogen oxide concentration and on the other hand with respect to the throttle reserve, acts exactly contrary to the change in the combustion air ratio, so that the adjustment of the ignition timing can be advantageously used to reduce the nitrogen oxide concentration and at the same time to re-establish the throttle reserve when the throttle reserve is almost exhausted due to the change in the combustion air ratio to reduce the nitrogen oxide concentration, that is, when it is no longer feasible to further change the combustion air ratio especially in the direction of reducing the nitrogen oxide concentration or when it is associated with serious drawbacks regarding the power of the internal combustion engine.

[0022] Adjusting the ignition timing point backwards is particularly understood in the context of the current technical teaching as the crankshaft angle value (at which ignition takes place within the working stroke with respect to said crankshaft angle value) being moved closer to the top dead center of the piston or being changed towards a higher value. Correspondingly, adjusting the ignition timing point forwards is particularly understood as the crankshaft angle value (at which ignition takes place within the working stroke with respect to said crankshaft angle value) being moved further away from the top dead center or being changed towards a lower value. Here, the working stroke extends in the case of an internal combustion engine configured as a four-stroke motor in particular from 0°KW (crankshaft angle) to 720°KW, but in the case of a two-stroke motor from 0°KW to 360°KW.

[0023] In one embodiment, when the measured throttle reserve reaches or falls below a pre-determined reserve minimum, the ignition timing point is incrementally adjusted backwards, in particular starting from the current value. Alternatively or additionally, when the measured throttle reserve exceeds the pre-determined reserve minimum (in particular plus a pre-determined hysteresis value), the ignition timing point is incrementally adjusted forwards, in particular starting from the current value.

[0024] In one embodiment, the pre-determined reserve minimum is from 100 mbar to 300 mbar, preferably up to 250 mbar, preferably up to 200 mbar, preferably up to 150 mbar. Alternatively or additionally, the pre-determined hysteresis value is from 30 mbar to 70 mbar, in particular from 40 mbar to 60 mbar, in particular 50 mbar.

[0025] In one embodiment, the adjustment range for adjusting the ignition timing point backwards is from 0.1°KW to 15°KW, in particular up to 12°KW, in particular up to 10°KW, in particular up to 8°KW. In one embodiment, the increment for adjusting the ignition timing point is 0.5°KW (ignition timing point increment).

[0026] According to a modification of the invention, it is provided that the ignition timing point is only adjusted forwards during a period in which a previous backwards adjustment has not yet been compensated. Advantageously, this avoids, in particular, selecting the ignition timing point forwards starting from a value set for normal operation, which could in particular lead to knocking or cause damage or even destruction of the internal combustion engine.

[0027] According to a modification of the invention, it is provided that when the measured throttle reserve (especially from above, that is, from a higher value) reaches or falls below a pre-determined reserve minimum, while the ignition time point reaches or exceeds a pre-determined maximum ignition time point, and at the same time the measured nitrogen oxide concentration is greater than a pre-determined theoretical nitrogen oxide concentration, a warning is issued. Especially in such a case, all measures for reducing the nitrogen oxide concentration have been exhausted: it is not possible to further increase the combustion air ratio because this would completely exhaust the throttle reserve, and it is also not possible to further retard the ignition time point because the pre-determined maximum ignition time point is especially chosen such that if the ignition time point were any later, it would no longer be possible to ensure that the internal combustion engine operates with an acceptable power or an acceptable efficiency, or it would no longer be possible to ensure complete combustion or thorough combustion in the combustion chamber. This in turn means that it is no longer possible to comply with the legally prescribed nitrogen oxide extreme values. With the aid of the warning, the operator of the internal combustion engine can advantageously be made aware of this situation. The operator can then take appropriate measures, such as intervening in the combustion gas supply or the combustion gas composition, or shutting down the internal combustion engine. This can especially also be achieved automatically without the need for manual intervention.

[0028] According to a modification of the invention, it is provided that the throttle reserve is adjusted by a bypass path adjustment device arranged in a compressor bypass path around a compressor arranged in an air path, wherein by actuating the bypass path adjustment device, the flow cross-section of the compressor bypass path is changed. Advantageously, the change in the flow cross-section of the compressor bypass path allows the adjustment, especially the regulation, of the throttle reserve when the internal combustion engine is operating at a changed throttle position. When actuating, especially closing, the bypass path adjustment device in the direction of reducing the flow cross-section of the compressor bypass path, the throttle reserve especially increases; conversely, when actuating, especially opening, the bypass path adjustment device in the direction of increasing the flow cross-section of the compressor bypass path, the throttle reserve decreases. With the aid of the bypass path adjustment device, it is especially also possible to compensate for the aging or contamination of the compressor, especially by continuously increasing the closing of the bypass path adjustment device over the life cycle of the compressor.

[0029] In one embodiment, the bypass path adjustment device is configured as a valve or a bypass valve.

[0030] A modification according to the invention is configured such that the ignition timing is adjusted backward only when, starting from the open position in particular, the predetermined closing position of the bypass path adjusting device is reached or exceeded, in particular in the direction towards the closed position (i.e., the fully closed position). Advantageously, hereby, the throttle reserve is first adjusted by means of the bypass path adjusting device, and the ignition timing is adjusted only when this option is exhausted. Thus, milder means are applied first, in particular, to maintain the throttle reserve before taking measures that more deeply interfere with the function of the internal combustion engine.

[0031] The object is also achieved in that a control device for an internal combustion engine is provided, which is configured to carry out the method according to the invention or a method according to one or more of the previously described embodiments. In respect of this control device, in particular, the advantages previously explained with respect to the method are obtained.

[0032] The object is also achieved in that an internal combustion engine is provided, which has a gas injection device, in particular a gas injection valve, wherein the gas injection device is arranged and configured to introduce combustion gas into the air path of the internal combustion engine. The internal combustion engine furthermore has a throttle valve arranged in the air path and a nitrogen oxide sensor arranged in the exhaust gas path of the internal combustion engine. In addition, the internal combustion engine has an ignition device arranged in the combustion chamber of the internal combustion engine and a control device according to the invention or a control device according to one or more of the previously described embodiments. The control device is operatively connected to the gas injection device, the throttle valve and the nitrogen oxide sensor. In respect of this internal combustion engine, in particular, the advantages previously explained with respect to the method or the control device are obtained.

[0033] A modification according to the invention is configured such that the internal combustion engine has a compressor in the air path, wherein the internal combustion engine furthermore has a compressor bypass path surrounding the compressor, wherein a bypass path adjusting device is arranged in the compressor bypass path, which is configured to change the flow cross-section of the compressor bypass path, and wherein the control device is operatively connected to the bypass path adjusting device.

[0034] In one embodiment, the internal combustion engine has a turbine in the exhaust gas path, which is operatively connected to the compressor drive. In particular, the internal combustion engine has an exhaust gas turbocharger, which on the one hand has a compressor arranged in the air path and on the other hand has a turbine arranged in the exhaust gas path, which is operatively connected to the compressor drive.

[0035] In one embodiment, the internal combustion engine, in particular, has a catalytic converter upstream of the nitrogen oxide sensor for reducing nitrogen oxides, in particular for carrying out selective catalytic reduction (SCR catalytic converter). Description of the Drawings

[0036] Below, the present invention will be explained in more detail with reference to the accompanying drawings. Herein,

[0037] Figure 1 A schematic illustration of an embodiment of an internal combustion engine having a control device;

[0038] Figure 2 A first schematic illustration of an embodiment of the method in the form of a flow chart, and

[0039] Figure 3 A second schematic illustration of the method is shown. Detailed Description of the Invention

[0040] Figure 1 A schematic illustration of an embodiment of an internal combustion engine 1 having an embodiment of a control device 3 is shown.

[0041] The internal combustion engine 1 has an air path 5 and a gas injection device 7, in particular a gas injection valve, in the air path 5, wherein the gas injection device 7 is arranged and configured to introduce combustion gas having a temporally fluctuating hydrogen fraction into the air path 5. Furthermore, the internal combustion engine 1 has a throttle valve 9 arranged in the air path 5 and a nitrogen oxide sensor 13 arranged in the exhaust gas path 11 of the internal combustion engine 1. In addition, the internal combustion engine 1 has an ignition device 17 arranged in the combustion chamber 15 of the internal combustion engine 1. For better clarity, only one combustion chamber 15 and only one ignition device 17 are correspondingly denoted by corresponding reference numerals. The control device 3 is operatively connected to the gas injection device 7, the throttle valve 9 and the nitrogen oxide sensor 13. The control device is in particular configured to carry out the method described in more detail below.

[0042] The internal combustion engine 1 in particular has a compressor 19 in the air path 5 and furthermore has a compressor bypass path 21 around the compressor 19, wherein a bypass path adjustment device 23, in particular a bypass valve, is arranged in the compressor bypass path 21. The bypass path adjustment device is configured to change the flow cross-section of the compressor bypass path 21. The control device 3 is operatively connected to the bypass path adjustment device 23.

[0043] Furthermore, the internal combustion engine 1 in particular has a turbine 25 in the exhaust gas path 11, which is operatively connected to the compressor 19 for driving. The internal combustion engine 1 in particular has an exhaust gas turbocharger 27, which on the one hand has a compressor 19 arranged in the air path 5 and on the other hand has a turbine 25 arranged in the exhaust gas path 11 and operatively connected to the compressor 19 for driving.

[0044] Figure 2 A first schematic illustration of an embodiment of the method is shown in the form of a flow chart.

[0045] Identical or functionally identical elements are provided with the same reference signs in all the figures, and accordingly reference is made to the foregoing description in this regard.

[0046] In the embodiment shown here, the method starts in a first step S1. In a second step S2, it is checked whether the nitrogen oxide concentration [NO x measured in the exhaust gas by means of the nitrogen oxide sensor 13, that is to say in particular the actual nitrogen oxide concentration, is greater than a pre-determined theoretical nitrogen oxide concentration [NO x s , where the pre-determined theoretical nitrogen oxide concentration [NO x s corresponds in particular to the legally prescribed extreme value (optionally minus a safety discount). If this is the case, in a third step S3, the combustion air ratio λ is increased from its current value by a pre-determined λ increment, in particular by appropriately controlling the gas injection device 7 in such a way that the mass flow of the combustion gas in the air path 5 is reduced incrementally. Then, in a fourth step S4, it is checked whether the throttle reserve DKR, in particular the actual throttle reserve, has reached or exceeded a pre-determined reserve minimum DKR min . If this is the case, the method continues in the second step S2.

[0047] Conversely, if the throttle reserve DKR is below the pre-determined reserve minimum DKR min , then in a fifth step S5 it is checked whether the ignition time point ZP, in particular the current actual ignition time point, has reached or exceeded a pre-determined maximum ignition time point ZP max . If this is the case, then in a sixth step S6 the ignition time point ZP is adjusted backwards from its current value, in particular by a pre-determined ignition time point increment. Preferably, however, in the sixth step S6, the ignition time point ZP is adjusted backwards only when the bypass path adjustment device 23 has reached or exceeded a pre-determined closed position. Thereby, the method continues again in the second step S2.

[0048] If in the second step S2 it is determined that the nitrogen oxide concentration [NO x is not greater than the theoretical nitrogen oxide concentration [NO x s , then in a seventh step S7 it is checked whether the nitrogen oxide concentration [NO x is less than the theoretical nitrogen oxide concentration [NO x s ​​​​If this is the case, the combustion air ratio λ is reduced from its current value in the eighth step S8, in particular by a pre-determined λ increment, in particular by appropriately controlling the gas injection device 7 in such a way that the mass flow of the combustion gas into the air path 5 is increased, in particular incrementally. Thereafter, in the ninth step S9, it is checked whether the throttle reserve DKR has reached or exceeded a pre-determined reserve minimum DKR min plus a pre-determined hysteresis value DKR Hyst If this is the case, the method continues in the second step S2.

[0049] Conversely, if the throttle reserve DKR exceeds the pre-determined reserve minimum DKR min plus a pre-determined hysteresis value DKR Hyst then in the tenth step S10 it is checked whether the ignition time point ZP has been changed backwards before. If this is the case and this backward adjustment has in particular not yet been compensated again by a subsequent forward adjustment, the ignition time point ZP is adjusted forward from its current value in the eleventh step S11, in particular by a pre-determined ignition time point increment. Thereafter, the method continues again in the second step S2.

[0050] Conversely, if in the tenth step S10 it is determined that the ignition time point ZP has not been changed backwards before, the method continues directly in the second step S2 immediately following the tenth step S10.

[0051] If in the seventh step S7 it is determined that the nitrogen oxide concentration [NO x is not less than the theoretical nitrogen oxide concentration [NO x s then in the twelfth step S12 it is checked whether the nitrogen oxide concentration [NO x is equal to the theoretical nitrogen oxide concentration [NO x s If this is the case, no further action is taken and the method optionally starts again in the first step S1 after a pre-determined waiting time. Conversely, if this is not the case, which should not actually be the case based on the inherent logic of the method, but may exceptionally occur in the case of high-frequency fluctuations in the hydrogen fraction, then the method continues in step S2.

[0052] If in the fifth step S5 it is determined that the ignition time point ZP has reached or exceeded a pre-determined maximum ignition time point ZP max then in the thirteenth step S13 it is re-checked whether the nitrogen oxide concentration [NO x is greater than the pre-determined theoretical nitrogen oxide concentration [NO x ​​​s If this is not the case, the method continues in the seventh step S7.

[0053] Conversely, if the nitrogen oxide concentration [NO x exceeds a pre-determined theoretical nitrogen oxide concentration [NO x s in the thirteenth step S13, a warning is issued in the fourteenth step S14. Preferably, the method ends thereby, but alternatively, the method can also restart in the first step S1 especially after the measures taken for the warning.

[0054] Figure 2 The method is presented in the order of discrete steps executed successively in time. The method can be executed in this way in one embodiment, and the diagrams are especially used for better understanding the structure of the method. In fact, especially in other embodiments, preferably the method is executed simultaneously by a plurality of regulating devices, as will be Figure 3 explained below in this regard.

[0055] In this regard, Figure 3 a second schematic diagram of the method is shown. In the embodiment shown here, the actual nitrogen oxide concentration [NO x and the theoretical nitrogen oxide concentration [NO x s are input into the nitrogen oxide regulating device 29. From the regulating deviation calculated therefrom, the offset combustion air ratio Δλ is calculated by the nitrogen oxide regulating device 29, and the offset combustion air ratio is settled with the theoretical combustion air ratio λ s read especially from the characteristic field in the first settlement unit 31 to obtain the combustion air ratio λ. With the combustion air ratio λ, the gas injection device 7 is controlled to adjust the combustion air ratio λ.

[0056] The actual throttle reserve DKR and the theoretical throttle reserve DKR S are simultaneously input into the bypass valve regulating device 33, which is set to adjust the position of the bypass path adjusting device 23. Through the bypass valve regulating device 33, the bypass valve position BKP is calculated from the regulating deviation calculated therefrom, and the bypass path adjusting device 23 is controlled by means of the bypass valve position.

[0057] Furthermore, the bypass valve position BKP is transmitted to the ignition timing adjustment device 35, wherein the bypass valve position BKP is particularly used to activate or trigger the ignition timing adjustment device 35. During the period when the bypass valve position BKP does not reach or exceed a predetermined closed position, the ignition timing adjustment device 35 is particularly not activated. If the bypass valve position BKP reaches or exceeds the predetermined closed position, the ignition timing adjustment device 35 is activated. Preferably, when the bypass valve position BKP is again lower than the predetermined closed position, the ignition timing adjustment device 35 is deactivated again.

[0058] If the ignition timing adjustment device 35 is activated, it calculates an offset ignition timing ΔZP from the actual throttle reserve DKR and the reserve minimum DKR min The offset ignition timing is settled with the theoretical ignition timing ZP, particularly read from the characteristic field, in a second calculation unit 37 to obtain the ignition timing ZP, and then the ignition device 17 is controlled by means of the ignition timing. The predetermined hysteresis value DKR s is particularly also input into the ignition timing adjustment device 35 so that the ignition timing ZP is adjusted forward again only when the throttle reserve DKR exceeds the reserve minimum DKR Hyst plus the predetermined hysteresis value DKR min Hyst ​​

Claims

1. A method for operating an internal combustion engine (1), wherein, - a combustion gas having a fluctuating hydrogen fraction is introduced into an air path (5) of the internal combustion engine (1), wherein, - a combustion air ratio for a combustion chamber (15) of the internal combustion engine (1) is adjusted by a presettable combustion gas mass flow into the air path (5), wherein, - a power parameter of the internal combustion engine (1) is adjusted by means of a throttle valve (9) arranged in the air path (5), wherein, - a nitrogen oxide concentration in an exhaust gas path (11) of the internal combustion engine (1) is measured, wherein, - the combustion air ratio is adjusted depending on the measured nitrogen oxide concentration, wherein, - a throttle valve reserve in the air path (5) is measured, and wherein, - an ignition time point in a combustion chamber (15) of the internal combustion engine (1) is selected depending on the measured throttle valve reserve.

2. The method according to claim 1, wherein, The power parameter is adjusted to a setpoint value by means of the throttle valve (9).

3. The method according to any one of the preceding claims, wherein, - when the measured nitrogen oxide concentration is greater than a theoretical nitrogen oxide concentration, the combustion air ratio is increased, and wherein, - when the measured nitrogen oxide concentration is less than the theoretical nitrogen oxide concentration, the combustion air ratio is decreased.

4. The method according to any one of the preceding claims, wherein, - when the measured throttle valve reserve reaches or falls below a predetermined reserve minimum, the ignition time point is adjusted backward, and wherein, - when the measured throttle valve reserve exceeds the predetermined reserve minimum, in particular exceeds the predetermined reserve minimum plus a predetermined hysteresis value, the ignition time point is adjusted forward after the backward adjustment.

5. The method according to claim 4, wherein During a period when a previous backward adjustment has not been compensated, the ignition time point is adjusted only forward.

6. The method according to any one of the preceding claims, wherein, A warning is issued when the measured throttle valve reserve reaches or falls below the predetermined reserve minimum, while the ignition time point reaches or exceeds a predetermined maximum ignition time point, and while the measured nitrogen oxide concentration is greater than the predetermined theoretical nitrogen oxide concentration.

7. The method according to any one of the preceding claims, wherein, The throttle valve reserve is adjusted by a bypass path adjustment device (23) arranged in a compressor bypass path (21) around a compressor (19) arranged in the air path (5), wherein the flow cross-section of the compressor bypass path (21) is changed by actuating the bypass path adjustment device (23).

8. The method according to claim 7, wherein When a predetermined closed position of the bypass path adjustment device (23) is reached or exceeded, the ignition time point is adjusted only backward.

9. A control device (3) for an internal combustion engine (1), which is configured to carry out the method according to any one of claims 1 to 8.

10. An internal combustion engine (1) having a gas injection device (7) arranged and configured to introduce combustion gas into an air path (5) of the internal combustion engine (1), the internal combustion engine having a throttle valve (9) arranged in the air path (5), a nitrogen oxide sensor (13) arranged in an exhaust gas path (11) of the internal combustion engine (1), an ignition device (17) arranged in a combustion chamber (15) of the internal combustion engine (1), and a control device (3) according to claim 9, wherein, The control device (3) is effectively connected to the gas injection device (7), the throttle valve (9) and the nitrogen oxide sensor (13).

11. The internal combustion engine (1) according to claim 10, wherein, The internal combustion engine (1) has a compressor (19) in the air path (5), wherein the internal combustion engine (1) furthermore has a compressor bypass path (21) around the compressor (19), wherein a bypass path adjustment device (23) is arranged in the compressor bypass path (21), the bypass path adjustment device being configured to change the flow cross-section of the compressor bypass path (21), and wherein the control device (3) is operatively connected to the bypass path adjustment device (23).

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