Methods and systems for an engine after-treatment system
AssigneeFord Global Technologies, LLC
InventorsFrederik De Smet, Christoph Boerensen, Frank Linzen
Life of this patent
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Abstract
The present subject matter relates to a method and a treatment system monitor for monitoring an engine exhaust after-treatment system containing more than one Lean NOx Traps (LNT). The method includes receiving an exhaust gas of a desired air-fuel ratio upstream of a respective LNT. The LNT is further regenerated using a richer than stoichiometric exhaust air-fuel ratio and subsequently an air-fuel ratio received downstream of the LNT is evaluated. Further, a working state of a respective LNT is determined based on the monitoring of the air-fuel ratio and oxygen level upstream and downstream of the LNT.
Claims18
A method for monitoring an engine exhaust after-treatment system, comprising:
- receiving a first exhaust gas of a desired air-fuel ratio upstream of a first lean NOx trap (LNT);
- initiating a richer than stoichiometric regeneration of the first LNT for obtaining a second exhaust gas downstream of the first LNT;
- evaluating an air-fuel ratio of the second exhaust gas received downstream of the first LNT;
- in response to the evaluated air-fuel ratio of the second exhaust gas being higher than the desired air-fuel ratio, activating injection of a vaporized reductant by an injector disposed downstream of the first LNT to the second exhaust gas for obtaining the desired air-fuel ratio of the second exhaust gas, where the injector is a vaporizer;
- receiving the second exhaust gas of the desired air-fuel ratio upstream of a second LNT;
- initiating a richer than stoichiometric regeneration of the second LNT for obtaining a third exhaust gas downstream of the second LNT;
- evaluating an air-fuel ratio of the third exhaust gas received downstream of the second LNT;
- and
- determining a working state of each of the first LNT and the second LNT based on each of the desired air-fuel ratio of the first exhaust gas, the evaluated air-fuel ratio of the second exhaust gas, and the evaluated air-fuel ratio of the third exhaust gas.
A method, comprising:
- responsive to a first air-fuel ratio upstream of a first lean NOx trap (LNT) being richer than a first threshold, initiating regeneration of the first LNT;
- during regeneration of the first LNT and responsive to a second air-fuel ratio upstream of a second LNT being leaner than the first threshold, injecting vaporized reductant to the second LNT to regenerate the second LNT;
- and
- responsive to an indication of degradation of at least one of the first LNT and the second LNT, adjusting one or more engine operating parameters including limiting an engine load to below a threshold engine load by reducing an opening of an intake throttle.
An engine system, comprising:
- an intake system;
- an exhaust system including a first lean NOx trap (LNT) coupled to an exhaust passage, a second LNT coupled to the exhaust passage downstream of the first LNT, a first oxygen sensor coupled to the exhaust passage upstream of the first LNT, a second oxygen sensor coupled to the exhaust passage upstream of the second LNT, a third oxygen sensor coupled to the exhaust passage downstream of the second LNT, and a vaporizer coupled to the exhaust passage upstream of the second LNT and downstream of the second oxygen sensor;
- and
- a controller with computer readable instructions stored on non-transitory memory for:
- in response to a sensed first exhaust air-fuel ratio upstream of the first LNT being lower than a stoichiometric air-fuel ratio, a higher than threshold sensed exhaust temperature or both, regenerating the first LNT, and
- in response to a sensed second exhaust air-fuel ratio downstream of the first LNT being higher than the stoichiometric air-fuel ratio, initiating injection of vaporized fuel to exhaust gas via the vaporizer to decrease the sensed second air-fuel ratio to below the stoichiometric air-fuel ratio, then regenerating the second LNT, and initiating diagnostics of each of the first LNT and the second LNT.
Dependencies are inferred from the claim text.