Methods for operating a compression ignition engine

1. A method of operating a compression ignition engine, comprising:

introducing an enriching component into a combustion chamber during an intake stroke;

igniting the enriching component during the compression stroke;

introducing a main injection of fuel to the combustion chamber after the ignition of the enriching component;

igniting the main injection of the fuel; and

introducing a supplemental gas to the combustion chamber after igniting the main injection of fuel and during an expansion stroke.

2. The method of claim 1 , wherein the enriching component comprises hydrogen.

3. The method of claim 1 , wherein the enriching component is provided by a device selected from the group consisting of a reformer, a solid oxide fuel cell, and a combination comprising at least one of the foregoing.

4. The method of claim 1 , comprising igniting the enriching component is with an element selected from the group consisting of a pilot injection of fuel, a glow plug, a spark plug, and a combination comprising at least one of the foregoing.

5. The method of claim 4 , wherein the pilot injection ignites the enriching component, and wherein the main injection of fuel is ignited in the presence of combustion products from the enriching component.

6. The method of claim 1 , comprising injecting the pilot injection when the compression stroke is at about bottom dead center to about top dead center.

7. The method of claim 6 , comprising injecting the pilot injection when the compression stroke is at about 90° to about 20° before top dead center.

8. The method of claim 6 , comprising injecting the pilot injection when the compression stroke is at about 20° to about top dead center.

9. The method of claim 1 , comprising start of the main injection at about 60° before top dead center on the compression stroke to start of main injection at about 30° after top dead center on the expansion stroke.

10. The method of claim 9 , comprising start of the main injection at about 45° before top dead center on the compression stroke to start of main injection at about 10° after top dead center on the expansion stroke.

11. The method of claim 10 , comprising start of the main injection at about 20° before top dead center on the compression stroke to start of main injection at about top dead center on the compression stroke.

12. The method of claim 1 , comprising introducing the supplemental gas at about 5° to about 90° after top dead center on the expansion stroke.

13. The method of claim 12 , comprising introducing the supplemental gas at about 10° to about 45° after top dead center on the expansion stroke.

14. The method of claim 13 , comprising introducing the supplemental gas at about 15° to about 30° after top dead center on the expansion stroke.

15. The method of claim 1 , comprising introducing main injection of the fuel and the supplemental gas using a dual-fluid injector.

16. The method of claim 1 , wherein the supplemental gas is selected from the group consisting of oxygen, oxygen-enriched air, compressed air, atmospheric air, and combinations comprising at least one of the foregoing.

17. The method of claim 1 , wherein the supplemental gas comprises an inert gas.

18. A method of operating a compression ignition engine, comprising:

introducing an enriching component into a combustion chamber during an intake stroke;

injecting a pilot injection when the compression stroke is at about bottom dead center to top dead center;

igniting the enriching component with the pilot injection of fuel during the compression stroke;

introducing a main injection of fuel to the combustion chamber after the ignition of the enriching component;

igniting the main injection of fuel in the presence of combustion products from the enriching component; and

introducing a supplemental gas to the combustion chamber after igniting the main injection of fuel and during an expansion stroke.