Method, computing unit, and computer program for determining an amount of hydrocarbons in an exhaust gas of a lean-operation internal-combustion engine

1. A method ( 200 ) for determining an amount of hydrocarbons in an exhaust gas ( 10 ) downstream of a lean-operation internal-combustion engine ( 110 ), comprising the following steps:

executing, with a computing unit coupled to the internal-combustion engine ( 110 ), a first catalyst heating mode of the internal-combustion engine ( 110 ) at a first catalyst temperature, wherein a predefinable amount of fuel having a predominantly non-combusting portion is introduced into a combustion chamber of the internal-combustion engine ( 110 ),

sensing an actual temperature change downstream of an oxidation catalyst ( 120 ) downstream of the internal-combustion engine ( 110 ) during the first catalyst heating mode,

determining, with the computing unit, the amount of hydrocarbons (cHC) in the exhaust gas ( 10 ) upstream of the oxidation catalyst ( 120 ) based on the actual temperature change,

calculating an expected temperature change (TExo_Mdl) downstream of the oxidation catalyst ( 120 ), taking into account the predefinable amount of fuel, and

correcting (rHC_Adapt) the calculation of the expected temperature change based on a difference (TExo_Dvt) between the actual temperature change and the expected temperature change (TExo_Mdl).

2. The method ( 200 ) according to claim 1 , further comprising:

adjusting the predefinable amount of fuel based on the actual and/or expected temperature change.

3. The method ( 200 ) according to claim 1 , further comprising:

executing a second catalyst heating mode of the internal-combustion engine ( 110 ), taking into account the correction (rHC_Adapt) of the calculation of the expected temperature change (TExo_Mdl) and/or taking into account the adjustment of the predefinable amount of fuel,

calculating a further expected temperature change downstream of the oxidation catalyst ( 120 ) during a second rich phase,

determining a further actual temperature change downstream of the oxidation catalyst ( 120 ) during the second rich phase, and

assessing a catalyst efficiency based on a difference (TExo_Dvt) between the further expected temperature change and the further actual temperature change,

wherein the second catalyst heating mode is carried out such that a lower temperature (T5_Meas) compared to the first catalyst heating mode is established downstream of the internal-combustion engine ( 110 ).

4. The method ( 200 ) according to claim 1 , wherein the expected and/or a further expected temperature change (TExo_Mdl) is determined using a first computational rule ( 220 ) that calculates the theoretical temperature (T5_MdlRef) downstream of the catalyst ( 120 ) under the prerequisite of a normal phase in which no non-combustible fuel is introduced into the combustion chamber of the internal-combustion engine ( 110 ) and using a second computational rule ( 210 ) that calculates the theoretical temperature (T5_Mdl) downstream of the catalyst ( 120 ), taking into account the non-combusting portion of the predefinable amount of fuel.

5. The method according to claim 1 , wherein a weighting factor (facWghtExo) based on a confidence factor (facWghtHC) of the determination of the amount of hydrocarbons (cHC) in the exhaust gas ( 10 ) and/or a temporal delay between a change in the amount of hydrocarbons (cHC) in the exhaust gas ( 10 ) and a change in temperature (T5_Mdl) downstream of the catalyst ( 120 ) is calculated ( 240 ) and accounted for in the calculation of the expected temperature change (TExo_Mdl).

6. The method according to claim 5 , wherein the weighting factor (facWghtExo) is calculated as a quotient from a temperature change calculated based on the amount of hydrocarbons (cHC) accounted for with the confidence factor (facWghtHC) and the temperature change (TExo_Mdl) expected without consideration of the confidence factor (facWghtHC).

7. The method ( 200 ) according to claim 1 , wherein a particulate filter ( 130 ) is provided downstream of the oxidation catalyst ( 120 ), and wherein, during the first catalyst heating mode of the internal-combustion engine ( 110 ), the particulate filter ( 130 ) is regenerated.

8. A computing unit ( 140 ) configured to:

execute a first catalyst heating mode of the internal-combustion engine ( 110 ) at a first catalyst temperature, wherein a predefinable amount of fuel having a predominantly non-combusting portion is introduced into a combustion chamber of the internal-combustion engine ( 110 ),

receive, from an exhaust temperature sensor ( 125 ), an actual temperature change downstream of an oxidation catalyst ( 120 ) downstream of the internal-combustion engine ( 110 ) during the first catalyst heating mode,

determine the amount of hydrocarbons (cHC) in the exhaust gas ( 10 ) upstream of the oxidation catalyst ( 120 ) based on the actual temperature change,

calculate an expected temperature change (TExo_Mdl) downstream of the oxidation catalyst ( 120 ), taking into account the predefinable amount of fuel, and

correct (rHC_Adapt) the calculation of the expected temperature change based on a difference (TExo_Dvt) between the actual temperature change and the expected temperature change (TExo_Mdl).

9. A non-transitory computer-readable medium including instructions executable by an electronic processor to perform a set of functions, the set of functions comprising:

executing a first catalyst heating mode of an internal-combustion engine ( 110 ) at a first catalyst temperature, wherein a predefinable amount of fuel having a predominantly non-combusting portion is introduced into a combustion chamber of the internal-combustion engine ( 110 ),

receiving, from an exhaust temperature sensor ( 125 ), an actual temperature change downstream of an oxidation catalyst ( 120 ) downstream of the internal-combustion engine ( 110 ) during the first catalyst heating mode,

determining the amount of hydrocarbons (cHC) in the exhaust gas ( 10 ) upstream of the oxidation catalyst ( 120 ) based on the actual temperature change,

calculating an expected temperature change (TExo_Mdl) downstream of the oxidation catalyst ( 120 ), taking into account the predefinable amount of fuel, and

correcting (rHC_Adapt) the calculation of the expected temperature change based on a difference (TExo_Dvt) between the actual temperature change and the expected temperature change (TExo_Mdl).