Transmission shift signal for aftertreatment device control
View Patent ↗Discontinuous torque ratio shifts by a transmission can result in complex transient exhaust conditions that can adversely affect exhaust air-fuel ratio control, which can result in ineffective regeneration. In extreme cases, the result can be irreversible damage to exhaust system components. The inventors' concept is to alter either regeneration scheduling or shift scheduling to avoid shifting while regenerating.
1. A method of operating a power generation system, comprising:
operating a diesel engine to produce exhaust comprising NO X ;
transmitting power from the diesel engine through a transmission capable of discontinuously shifting between torque ratios;
passing the exhaust through an exhaust aftertreatment system comprising a lean NO X trap to adsorb a portion of the NO X from the exhaust;
timing denitration of the lean NO X trap based on a criteria relating to the state and/or the performance of the exhaust aftertreatment system, or a portion thereof comprising the lean NO X trap; and
varying the denitration timing to avoid denitrating while the transmission is discontinuously shifting;
wherein denitrating the lean NO X trap comprises providing an overall rich exhaust-reductant mixture to the lean NO X trap, whereby the lean NO X trap releases and reduces stored NO X .
2. The method of claim 1 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein second controller sends the first controller a signal indicating a shift is imminent.
3. The method of claim 2 , wherein:
the signal indicating a shift is imminent is provided sufficiently far in advance of the shift to allow time for a regeneration to be initiated and completed prior to the shift; and
the first controller selectively initiates a denitration in response to the signal.
4. The method of claim 2 , wherein the first controller responds to the signal by preventing the start of any denitration in a period following the signal.
5. The method of claim 2 , wherein the first controller responds to the signal by preventing the start of any denitration at least until the first controller receives a further signal from the second controller indicating the shift has been essentially completed.
6. The method of claim 1 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein second controller sends the first controller a signal indicating a probability that a shift will occur in an upcoming period.
7. The method of claim 1 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein first controller is provided with the criteria used by the second controller in deciding the shift timing.
8. The method of claim 1 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein the second controller provides the first controller with upshift and downshift points.
9. The method of claim 1 , wherein the denitration timing is varied to avoid some types of shifts, but not to avoid other types of shifts.
10. The method of claim 1 , wherein the denitration is postponed to avoid denitrating during shifts.
11. The method of claim 10 , wherein the exhaust aftertreatment system further comprises a fuel reformer configured upstream from the lean NO X trap in an exhaust line and the method further comprises selectively injecting fuel into the exhaust line upstream from the fuel reformer during the shift to heat the fuel reformer in preparation for denitrating the lean NO X trap.
12. A method of operating a power generation system, comprising:
operating a diesel engine to produce exhaust comprising NO X ;
transmitting power from the diesel engine through a transmission that discontinuously shifts between torque ratios;
passing the exhaust through an exhaust aftertreatment system comprising a lean NO X trap to adsorb a portion of the NO X from the exhaust;
timing denitration of the lean NO X trap based on a criteria relating to the state and/or the performance of the exhaust aftertreatment system, or a portion thereof comprising the lean NO X trap; and
varying the timing of the discontinuous shifts to avoid discontinuously shifting while denitrating the lean NO X trap;
wherein denitrating the lean NO X trap comprises providing an overall rich exhaust-reductant mixture to the lean NO X trap, whereby the lean NO X trap releases and reduces stored NO X .
13. The method of claim 12 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein first controller sends the second controller a signal indicating the criteria for denitration is close to being satisfied.
14. The method of claim 12 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein first controller sends the second controller a signal indicating a denitration is imminent.
15. The method of claim 14 , wherein:
the signal indicating a shift is imminent is provided sufficiently far in advance of the denitration to allow time for a shift to be completed prior to the rich phase of the denitration; and
the second controller selectively initiates a shift in response to the signal.
16. The method of claim 14 , wherein the second controller responds to the signal by preventing any discontinuous shift in a period following the signal.
17. The method of claim 14 , wherein the second controller responds to the signal by preventing any discontinuous shift at least until the second controller receives a further signal from the first controller indicating the denitration has been essentially completed.
18. The method of claim 12 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein first controller sends the second controller a signal indicating a probability that a denitration will occur in an upcoming period.
19. The method of claim 12 , wherein:
the denitration timing is determined by a first controller; and
the discontinuous shift timing is determined by a second controller, that is physically distinct from the first controller;
wherein second controller is provided with the criteria used by the first controller in deciding the denitration timing.
20. The method of claim 12 , wherein a shift is postponed to avoid shifting during denitration.