System and method to manage SCR catalyst NO
Systems and methods are provided for determining and controlling an NO 2 to NO x ratio reference target in an exhaust conduit between a first SCR catalyst and a second SCR catalyst. The method includes determining a present NO 2 to NO x ratio in the exhaust conduit between the first SCR catalyst and the second SCR catalyst, and providing a reductant doser command in response to a deviation of the present NO 2 to NO x ratio from the NO 2 to NO x ratio reference target.
1. A method, comprising:
determining an NO 2 to NO x ratio reference target to a first selective catalytic reduction (SCR) catalyst of an aftertreatment system, the aftertreatment system including the first SCR catalyst, a second SCR catalyst upstream of the first SCR catalyst, and a diesel oxidation catalyst (DOC) upstream of the first SCR catalyst and downstream of the second SCR catalyst;
determining a present NO 2 to NO x ratio to the first SCR catalyst, wherein determining the present NO 2 to NO x ratio to the first SCR catalyst includes receiving an input that indicates a deactivation condition of the DOC correlated to a reduced NO 2 production capability of the DOC, wherein the input indicating the deactivation condition corresponds to cumulative operational data for the aftertreatment system indicating one of a poisoning condition and an aging condition of the DOC;
determining an NO 2 to NO x ratio deviation in response to the NO 2 to NO x ratio reference target and the present NO 2 to NO x ratio, wherein determining the NO 2 to NO x ratio deviation includes determining a threshold deviation value indicated by a calibration table based on the deactivation condition;
determining a reductant doser command for injection of a reductant amount upstream of the second SCR catalyst in response to the threshold deviation value; and
providing the reductant doser command in response to the threshold deviation value.
2. The method of claim 1 , further comprising determining a rate of change of the present NO 2 to NO x ratio and further adjusting the reductant doser command in response to the rate of change.
3. The method of claim 1 , wherein the second SCR catalyst is a close-coupled SCR catalyst.
4. The method of claim 1 , wherein determining the present NO 2 to NO x ratio further comprises determining an NO/NO 2 amount at an outlet of the DOC.
5. The method of claim 1 , wherein determining the present NO 2 to NO x ratio further comprises determining an NO 2 amount at an inlet to the first SCR catalyst and at an outlet of the first SCR catalyst.
6. The method of claim 1 , wherein the aftertreatment system includes the first and second SCR catalysts and the DOC comprises a portion of a diesel oxidation catalyst/diesel particulate filter (DOC/DPF) system.
7. The method of claim 6 , wherein determining the deactivation condition includes determining cumulative regeneration hours of the DOC/DPF system.
8. The method of claim 6 , wherein determining the deactivation condition includes determining accumulated temperature time of the aftertreatment system.
9. The method of claim 6 , wherein determining the deactivation condition includes determining a reversible deactivation condition by determining fuel consumption at temperature.
10. The method of claim 9 , wherein the reversible deactivation condition is a sulfur loading of the DOC/DPF system.
11. The method of claim 6 , wherein the reductant amount for injection upstream of the second SCR catalyst increases as the DOC/DPF system ages.
12. The method of claim 1 , wherein determining the reductant injection command further includes determining a second reductant command for injection of a second reductant amount upstream of the first SCR catalyst and downstream of the DOC.
13. The method of claim 12 , wherein the second reductant amount decreases as the reductant amount injected upstream of the second SCR catalyst increases.
14. The method of claim 13 , wherein the second reductant amount is limited to control ammonia slip past the second SCR catalyst.
15. A method, comprising:
interpreting an NO 2 to NO x ratio reference target comprising a target amount of NO 2 to a first selective catalytic reduction (SCR) catalyst of an aftertreatment system, the aftertreatment system including the first SCR catalyst, a second SCR catalyst upstream of the first SCR catalyst, and a diesel oxidation catalyst DOC upstream of the first SCR catalyst and downstream of the second SCR catalyst;
interpreting a present NO 2 to NO x ratio upstream of the first SCR catalyst, wherein interpreting the present NO 2 to NO x ratio upstream of the first SCR catalyst includes interpreting an input that indicates a deactivation condition of the DOC correlated to a reduced NO 2 production capability of the DOC, wherein the input indicating the deactivation condition corresponds to cumulative operational data for the aftertreatment system indicating one of a poisoning condition and an aging condition of the DOC;
interpreting a deviation of the present NO 2 to NO x ratio from the NO 2 to NO x ratio reference target, wherein determining the deviation of the present NO 2 to NO x ratio from the NO 2 to NO x ratio reference target includes determining a threshold deviation value indicated by a calibration table based on the deactivation condition; and
injecting an amount of reductant upstream of the second SCR catalyst to provide the target amount of NO 2 to the first SCR catalyst in response to the threshold deviation value.
16. The method of claim 15 , wherein the DOC comprises a portion of a diesel oxidation catalyst/diesel particulate filter (DOC/DPF) system between the first and second SCR catalysts.
17. The method of claim 16 , further comprising injecting a second amount of reductant upstream of the first SCR catalyst and downstream from the DOC/DPF system.
18. The method of claim 17 , wherein the second amount of reductant decreases as the amount of reductant injected upstream of the second SCR catalyst increases.
19. The method of claim 18 , wherein the second amount of reductant is limited to control ammonia slip past the second SCR catalyst.
20. The method of claim 16 , wherein interpreting the present NO 2 to NO x ratio further comprises interpreting an NO/NO 2 amount at an outlet of the DOC/DPF system.
21. The method of claim 16 , wherein interpreting the deactivation condition includes interpreting cumulative regeneration hours of the DOC/DPP system.
22. The method of claim 16 , wherein interpreting the deactivation condition includes interpreting a reversible deactivation condition by determining fuel consumption at temperature.
23. The method of claim 22 , wherein the reversible deactivation condition is a sulfur loading of the DOC/DPF system.
24. The method of claim 15 , wherein interpreting the present NO 2 to NO x ratio further comprises interpreting an NO 2 amount at an inlet and at an outlet of the first SCR catalyst.
25. The method of claim 15 , wherein the NO 2 to NO x ratio reference target is a molar ratio of NO 2 to NO x .
26. The method of claim 25 , wherein the molar ratio is 0.5.
27. An apparatus, comprising:
a controller implemented hardware and a non-transitory computer readable medium, the plurality of modules including:
an NO 2 to NO x ratio reference target module structured to determine a NO 2 to NO x ratio reference target at an inlet to a first selective catalytic reduction (SCR) catalyst of an aftertreatment system, the first SCR catalyst being located downstream of a second SCR catalyst and a diesel oxidation catalyst (DOC) being located upstream of the first SCR catalyst and downstream of the second SCR catalyst;
an NO 2 to NO x ratio determination module structured to determine a present NO 2 to NO x ratio at the inlet to the first SCR catalyst in response to an input corresponding to cumulative operational data of the aftertreatment system indicating a deactivation condition of the DOC correlated to a reduced NO 2 production capability of the DOC due to one of an aging condition and a poisoning condition of the DOC;
an NO 2 to NO x ratio deviation module structured to determine an NO 2 threshold deviation value indicated by a calibration table based on the deactivation condition and the NO 2 to NO x ratio reference target; and
a dosing control module structured to provide a reductant doser command linked to the deactivation condition in response to the NO 2 threshold deviation value, the reductant doser command corresponding to a reductant amount for injection upstream of the second SCR catalyst.
28. The apparatus of claim 27 , wherein the DOC comprises a portion of a diesel oxidation catalyst/diesel particulate filter (DOC/DPF) system between the first SCR catalyst and the second SCR catalyst.
29. The apparatus of claim 28 , wherein the dosing control module is further structured to provide a second reductant doser command in response to the NO 2 threshold deviation value, the second reductant doser command corresponding to a second reductant amount for injection upstream of the first SCR catalyst and downstream of the DOC/DPF system.
30. The apparatus of claim 28 , wherein the second SCR catalyst is a close-coupled SCR catalyst.
31. The apparatus of claim 28 , wherein the NO 2 to NO x ratio determination module is further structured to determine the present NO 2 to NO x ratio as a function of an NO/NO 2 amount at an outlet of the DOC/DPF system.
32. The apparatus of claim 27 , wherein the NO 2 to NO x ratio determination module is further structured to determine the present NO 2 to NO x ratio as a function of the NO 2 amount at the inlet and an outlet of the first SCR catalyst.
33. A system, comprising:
an internal combustion engine;
an exhaust conduit fluidly coupled to the internal combustion engine; a first selective catalytic reduction (SCR) catalyst fluidly coupled to the exhaust conduit;
a second SCR catalyst fluidly coupled to the exhaust conduit at a position upstream of the first SCR catalyst;
a diesel oxidation catalyst (DOC) located upstream of the first SCR catalyst and downstream of the second SCR catalyst;
a reductant doser operationally coupled to the exhaust conduit at a first position upstream of the first SCR catalyst and downstream of the second SCR catalyst and at a second position upstream of the second SCR catalyst;
a controller including a plurality of modules implemented in at least one of hardware and a non-transitory computer readable medium, the plurality of modules comprising:
an NO 2 to NO x ratio reference target module structured to determine a NO 2 to NO x ratio reference target at an inlet to the first SCR catalyst;
an NO 2 to NO x ratio determination module structured to determine a present NO 2 to NO x ratio at the inlet to the first SCR catalyst in response to an input corresponding to cumulative operational data of the aftertreatment system indicating a deactivation condition of the DOC correlated to a reduced NO 2 production capability of the DOC due to one of an aging condition and a poisoning condition of the DOC;
an NO 2 to NO x ratio deviation module structured to determine an NO 2 threshold deviation value indicated by a calibration table based on the deactivation condition and the NO 2 to NO x ratio reference target; and
a dosing control module structured to provide a reductant doser command linked to the deactivation condition in response to the NO 2 threshold deviation value, the reductant doser command corresponding to a first reductant amount for injection at the first position and a second reductant amount for injection at the second position.
34. The system of claim 33 , wherein the second SCR catalyst is a close-coupled SCR catalyst.