Advanced Engine Management of Individual Cylinders for Control of Exhaust Species

Abstract

This invention is a method and system for controlling engine-out exhaust species of a combustion engine having a plurality of cylinders by providing a means for controlling combustion parameters in individual cylinders, grouping the individual cylinders into a lean set and a rich set of one or more cylinders, combusting the lean set in a lean combustion parameter condition having a lean air:fuel equivalence ratio, combusting the rich set in a rich combustion parameter condition having a rich air:fuel equivalence ratio, and providing a means for adjusting the lean set and the rich set of one or more cylinders to generate net-lean combustion. The exhaust species have elevated concentrations of hydrogen and oxygen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the exhaust sampling schematic.

FIG. 2 is bar charts showing engine-out H₂, CO, and HC for AFR sweep, DEM, and Post80 LNT regeneration strategies.

FIG. 3 is a graph of peak hydrogen, CO, and HC concentrations for Post80 AFR sweep of 3 second duration.

FIG. 4 is a graph of H₂, CO, and HC concentrations for continuous individual-cylinder DEM.

FIG. 5 is a graph of oxygen, opacity (smoke), and CO₂ levels for continuous individual-cylinder DEM.

FIG. 6 is a bar chart of engine-out hydrocarbon species for continuous individual-cylinder DEM, 3 times excess fuel fraction.

FIG. 7 is a graph of catalyst core temperature versus time for 30 k hr⁻¹space velocity, normal lean versus individual-cylinder DEM (lean with H₂)

FIG. 8 is a graph of catalyst inlet and outlet NOx concentration, and catalyst inlet, core, and outlet temperatures for individual-cylinder DEM strategy during a preliminary catalyst warmup experiment.

FIG. 9 is a graph of catalyst-out reductant concentrations for individual-cylinder DEM strategy during a preliminary catalyst warmup experiment.

Claims

1. A method for controlling engine-out exhaust species of a combustion engine having a plurality of cylinders, the method comprising: providing a means for controlling combustion parameters in individual cylinders, grouping said individual cylinders into a lean set and a rich set of one or more cylinders,combusting said lean set in a lean combustion parameter condition comprising a lean air:fuel equivalence ratio,combusting said rich set in a rich combustion parameter condition comprising a rich air:fuel equivalence ratio,providing a means for sequentially indexing said lean set and said rich set of one or more cylinders to generate net-lean combustion,wherein said exhaust species comprises elevated concentrations of hydrogen and oxygen.

2. The method of claim 1 wherein said exhaust species further comprises at least one species selected from the group consisting of carbon monoxide and hydrocarbons.

3. The method of claim 1 wherein said combustion parameter is at least one parameter selected from the group consisting of intake throttling, exhaust gas recirculation (EGR), timing of in-cylinder fuel injection, duration of in-cylinder fuel injection, number of fuel injection events, and turbocharger wastegate.

4. The method of claim 1 wherein said combustion parameters further comprise enriched combustion.

5. The method of claim 4 wherein said means for controlling combustion parameters further comprises a delayed and extended main strategy.

6. The method of claim 4 wherein said means for controlling combustion parameters further comprises a post80 strategy.

7. The method of claim 1 wherein said lean air:fuel equivalence ratio is less than 1.

8. The method of claim 1 wherein said rich air:fuel equivalence ratio is greater than 1.

9. A system for controlling engine-out exhaust species of a combustion engine having a plurality of cylinders comprising: a means for controlling combustion parameters in individual cylinders,a means for grouping said individual cylinders into a lean set and a rich set of one or more cylinders,a means for combusting said lean set in a lean combustion parameter condition comprising a lean air:fuel equivalence ratio,a means for combusting said rich set in a rich combustion parameter condition comprising a rich air:fuel equivalence ratio,a means for sequentially indexing said lean set and said rich set of one or more cylinders to generate net-lean combustion,wherein said exhaust species comprises elevated concentrations of hydrogen and oxygen.

10. The system of claim 9 wherein said exhaust species further comprises at least one species selected from the group consisting of carbon monoxide and hydrocarbons.

11. The system of claim 9 wherein said combustion parameter is at least one parameter selected from the group consisting of intake throttling, exhaust gas recirculation (EGR), timing of in-cylinder fuel injection, duration of in-cylinder fuel injection, number of fuel injection events, and turbocharger wastegate.

12. The system of claim 9 wherein said combustion parameters further comprise enriched combustion.

13. The system of claim 12 wherein said means for controlling combustion parameters further comprises a delayed and extended main strategy.

14. The system of claim 12 wherein said means for controlling combustion parameters further comprises a post80 strategy.

15. The system of claim 9 wherein said lean air:fuel equivalence ratio is less than 1.

16. The system of claim 9 wherein said rich air:fuel equivalence ratio is greater than 1.